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Hoeker GS, James CC, Tegge AN, Gourdie RG, Smyth JW, Poelzing S. Attenuating loss of cardiac conduction during no-flow ischemia through changes in perfusate sodium and calcium. Am J Physiol Heart Circ Physiol 2020; 319:H396-H409. [PMID: 32678707 DOI: 10.1152/ajpheart.00112.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myocardial ischemia leads to conduction slowing, cell-to-cell uncoupling, and arrhythmias. We previously demonstrated that varying perfusate sodium (Na+) and calcium (Ca2+) attenuates conduction slowing and arrhythmias during simulated ischemia with continuous perfusion. Cardioprotection was selectively associated with widening of the perinexus, a gap junction adjacent nanodomain important to ephaptic coupling. It is unknown whether perfusate composition affects the perinexus or ischemic conduction during nonsimulated ischemia, when coronary flow is reduced or halted. We hypothesized that altering preischemic perfusate composition could facilitate perinexal expansion and attenuate conduction slowing during global ischemia. To test this hypothesis, ex vivo guinea pig hearts (n = 49) were Langendorff perfused with 145 or 153 mM Na+ and 1.25 or 2.0 mM Ca2+ and optically mapped during 30 min of no-flow ischemia. Altering Na+ and Ca2+ did not substantially affect baseline conduction. Increasing Na+ and decreasing Ca2+ both lowered pacing thresholds, whereas increasing Ca2+ narrowed perinexal width (Wp). A least squares mean estimate revealed that reduced perfusate Na+ and Ca2+ resulted in the most severe conduction slowing during ischemia. Increasing Na+ alone modestly attenuated conduction slowing, yet significantly delayed the median time to conduction block (10 to 16 min). Increasing both Na+ and Ca2+ selectively widened Wp during ischemia (22.7 vs. 15.7 nm) and attenuated conduction slowing to the greatest extent. Neither repolarization nor levels of total or phosphorylated connexin43 correlated with conduction slowing or block. Thus, perfusate-dependent widening of the perinexus preserved ischemic conduction and may be an adaptive response to ischemic stress.NEW & NOTEWORTHY Conduction slowing during acute ischemia creates an arrhythmogenic substrate. We have shown that extracellular ionic concentrations can alter conduction by modulating ephaptic coupling. Here, we demonstrate increased extracellular sodium and calcium significantly attenuate conduction slowing during no-flow ischemia. This effect was associated with selective widening of the perinexus, an intercalated disc nanodomain and putative cardiac ephapse. These findings suggest that acute changes in ephaptic coupling may serve as an adaptive response to ischemic stress.
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Affiliation(s)
- Gregory S Hoeker
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Carissa C James
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia
| | - Allison N Tegge
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Statistics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Robert G Gourdie
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - James W Smyth
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Steven Poelzing
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
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Wit AL. Basic Electrophysiologic Mechanisms of Sudden Cardiac Death Caused by Acute Myocardial Ischemia and Infarction. Card Electrophysiol Clin 2017; 9:525-536. [PMID: 29173399 DOI: 10.1016/j.ccep.2017.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Sudden cardiac death caused by acute ischemia results from electrophysiologic changes in myocardium deprived of its blood supply. These changes include a reduction in resting potential and phase 0 depolarization and an increase in intercellular resistivity that slow conduction, cause conduction block, and lead to reentrant excitation and ventricular fibrillation. Reperfusion of a coronary artery after a short period of occlusion leads to similar changes.
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Affiliation(s)
- Andrew L Wit
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, 630 West 168(th) Street, New York, NY 10032, USA.
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3
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Garg V, Taylor T, Warren M, Venable P, Sciuto K, Shibayama J, Zaitsev A. β-Adrenergic stimulation and rapid pacing mutually promote heterogeneous electrical failure and ventricular fibrillation in the globally ischemic heart. Am J Physiol Heart Circ Physiol 2015; 308:H1155-70. [PMID: 25713306 PMCID: PMC4551128 DOI: 10.1152/ajpheart.00768.2014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/16/2015] [Indexed: 01/09/2023]
Abstract
Global ischemia, catecholamine surge, and rapid heart rhythm (RHR) due to ventricular tachycardia or ventricular fibrillation (VF) are the three major factors of sudden cardiac arrest (SCA). Loss of excitability culminating in global electrical failure (asystole) is the major adverse outcome of SCA with increasing prevalence worldwide. The roles of catecholamines and RHR in the electrical failure during SCA remain unclear. We hypothesized that both β-adrenergic stimulation (βAS) and RHR accelerate electrical failure in the globally ischemic heart. We performed optical mapping of the action potential (OAP) in the right ventricular (RV) and left (LV) ventricular epicardium of isolated rabbit hearts subjected to 30-min global ischemia. Hearts were paced at a cycle length of either 300 or 200 ms, and either in the presence or in the absence of β-agonist isoproterenol (30 nM). 2,3-Butanedione monoxime (20 mM) was used to reduce motion artifact. We found that RHR and βAS synergistically accelerated the decline of the OAP upstroke velocity and the progressive expansion of inexcitable regions. Under all conditions, inexcitability developed faster in the LV than in the RV. At the same time, both RHR and βAS shortened the time to VF (TVF) during ischemia. Moreover, the time at which 10% of the mapped LV area became inexcitable strongly correlated with TVF (R(2) = 0 .72, P < 0.0001). We conclude that both βAS and RHR are major factors of electrical depression and failure in the globally ischemic heart and may contribute to adverse outcomes of SCA such as asystole and recurrent/persistent VF.
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Affiliation(s)
- Vivek Garg
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah
| | - Tyson Taylor
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Mark Warren
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Paul Venable
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Katie Sciuto
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Junko Shibayama
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Internal Medicine, School of Medicine, University of Utah, Salt Lake City, Utah
| | - Alexey Zaitsev
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
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4
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Abstract
Ventricular fibrillation (VF) is the leading cause of sudden cardiac death. This brief review addresses issues relevant to the dynamics of the rotors responsible for functional reentry and VF. It also makes an attempt to summarize present-day knowledge of the manner in which the dynamic interplay between inward and outward transmembrane currents and the heterogeneous cardiac structure establish a substrate for the initiation and maintenance of rotors and VF. The fragmentary nature of our current understanding of ionic VF mechanisms does not even allow an approach toward a "Theory of VF". Yet some hope is provided by recently obtained insight into the roles played in VF by some of the sarcolemmal ion channels that control the excitation-recovery process. For example, strong evidence supports the idea that the interplay between the rapid-inward sodium current and the inward-rectifier potassium current controls rotor formation, as well as rotor stability and frequency. Solid evidence also exists for an involvement of L-type calcium current in the control of rotor frequency and in determining VF-to-ventricular tachycardia conversion. Less clear, however, is whether or not time dependent outward currents through voltage-gated potassium channels affect the fibrillatory process. Hopefully, taking advantage of currently available approaches of structural, molecular and cellular biology, together with computational and imaging techniques, will afford us the opportunity to further advance knowledge on VF mechanisms.
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Affiliation(s)
- Sami F Noujaim
- Department of Pharmacology and Institute for Cardiovascular Research, SUNY Upstate Medical University, Syracuse, NY 13210, USA
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5
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Abstract
The membrane site of action and intracellular effects of diltiazem on heart and blood vessels are briefly discussed and compared to those of other calcium entry blockers, mainly verapamil and nifedipine. Diltiazem seems to have another site of action in the membrane than verapamil and nifedipine. Even if its main action is exerted at the cell membrane level, diltiazem may, at high concentrations, appears to have intracellular effects. Similar to the haemodynamic effects of verapamil and nifedipine, those of diltiazem are determined not only by direct actions on heart and peripheral vessels, but also by sympathetic reflex activity which modulates the direct effects. Two aspects of the myocardial protective action of diltiazem are discussed, the ability of the drug to reduce the frequency of ventricular dysrhythmias associated with ischaemic damage, and the ability to protect the ischaemic myocardium during reperfusion.
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6
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Clusin WT. Mechanisms of calcium transient and action potential alternans in cardiac cells and tissues. Am J Physiol Heart Circ Physiol 2008; 294:H1-H10. [DOI: 10.1152/ajpheart.00802.2007] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Alternation of cardiac action potential duration (APD) from beat to beat and concurrent alternation of the amplitude of the calcium transient are regarded as important arrhythmia mechanisms. These phenomena are causally interrelated and can be reliably evoked by an increase in beat frequency or by ischemia. The first part of this historical review deals with the physiology of APD alternans. Sections recounting the evolution of knowledge about calcium-activated ion currents and calcium transient alternans are interspersed among sections describing the growth of the so-called “restitution hypothesis,” which involves time-dependent recovery of potassium channels (including their passage through pre-open states) as a function of diastolic interval. Major developments are generally in chronological order, but it is necessary to move back and forth between the two theories to respect the overall time line, which runs from about l965 to the present. The concluding two sections deal with the pathophysiology of calcium transient and APD alternans during ischemia, which may be the basis for out-of-hospital cardiac arrest during the initial stages of acute myocardial infarction.
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7
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Abstract
Rapid progress has been made in understanding the molecular mechanisms by which calcium ions mediate certain cardiac arrhythmias. Principal advances include imaging of cytosolic calcium in isolated cells and in intact tissues, use of fluorescent indicators and monophasic action potentials to record membrane potentials in isolated tissue, and sequencing of the genes that encode critical ion channel proteins. In this review, five types of arrhythmias are discussed where calcium ion currents, or currents controlled by calcium, appear to be responsible for arrythmogenesis. These include: (1) the delayed afterpotential that occurs in conditions of intracellular calcium overload such as digitalis toxicity; (2) the early afterdepolarization that occurs when action potential duration is prolonged; (3) the slowly conducted calcium-dependent action potential (the slow response) in the SA and AV nodes; (4) the phenomenon of calcium transient alternans during ischemia, which is related to action potential duration alternans and t-wave alternans; (5) catecholamine-induced cardiac arrhythmias in families with mutations of the sarcoplasmic reticulum calcium-release channel. For each type of arrhythmia, the clinical implications of emerging knowledge are discussed. An especially important issue is whether ventricular fibrillation during acute coronary artery occlusion is due to calcium transient alternans. Ventricular fibrillation due to acute ischemia is an important subset of the 400,000 sudden cardiac deaths that occur annually in the U.S. Certain drugs, including beta blockers, fish oils, verapamil, and diltiazem, seem to specifically prevent ventricular fibrillation in this setting, and in most cases an effect of the drug on cytosolic calicum appears to be involved.
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Affiliation(s)
- William T Clusin
- Cardiac Electrophysiology and Arrythmia Service, Stanford University Medical Center, Stanford, CA 94305-5233, USA.
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8
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Strohmenger HU, Eftestol T, Sunde K, Wenzel V, Mair M, Ulmer H, Lindner KH, Steen PA. The predictive value of ventricular fibrillation electrocardiogram signal frequency and amplitude variables in patients with out-of-hospital cardiac arrest. Anesth Analg 2001; 93:1428-33, table of contents. [PMID: 11726418 DOI: 10.1097/00000539-200112000-00016] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
UNLABELLED We evaluated ventricular fibrillation frequency and amplitude variables to predict successful countershock, defined as pulse-generating electrical activity. We also elucidated whether bystander cardiopulmonary resuscitation (CPR) influences these electrocardiogram (ECG) variables. In 89 patients with out-of-hospital cardiac arrest, ECG recordings of 594 countershock attempts were collected and analyzed retrospectively. By using fast Fourier transformation analysis of the ventricular fibrillation ECG signal in the frequency range 0.333-15 Hz (median [range]), median frequency, dominant frequency, spectral edge frequency, and amplitude were as follows: 4.4 (2.4-7.5) Hz, 4.0 (0.7-7.0) Hz, 7.7 (3.7-13.7) Hz, and 0.94 (0.24-1.95) mV, respectively, before successful countershock (n = 59). These values were 3.8 (0.8-7.7) Hz (P = 0.0002), 3.0 (0.3-9.7) Hz (P < 0.0001), 7.3 (2.0-14.0) Hz (P < 0.05), and 0.53 (0.03-3.03) mV (P < 0.0001), respectively, before unsuccessful countershock (n = 535). In patients in whom bystander CPR was performed (n = 51), ventricular fibrillation frequency and amplitude before the first defibrillation attempt were higher than in patients without bystander CPR (n = 38) (median frequency, 4.4 [2.4-7.5] vs 3.7 [1.8-5.3] Hz, P < 0.0001; dominant frequency, 3.8 [0.9-7.7] vs 2.6 [0.8-5.9] Hz, P < 0.0001; spectral edge frequency, 8.4 [4.8-12.9] vs 7.2 [3.9-12.1] Hz, P < 0.05; amplitude, 0.79 [0.06-4.72] vs 0.67 [0.16-2.29] mV, P = 0.0647). Receiver operating characteristic curves demonstrate that successful countershocks will be best discriminated from unsuccessful countershocks by ventricular fibrillation amplitude (3000-ms epoch). At 73% sensitivity, a specificity of 67% was obtained with this variable. IMPLICATIONS In patients with out-of-hospital cardiac arrest, successful countershocks will be best discriminated from unsuccessful countershocks by ventricular fibrillation amplitude (3000-ms epoch). At 73% sensitivity, a specificity of 67% was obtained with this variable.
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Affiliation(s)
- H U Strohmenger
- Department of Anesthesiology, Leopold-Franzens University, Innsbruck, Austria.
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9
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Aupetit JF, Bui-Xuan B, Kioueh I, Loufoua J, Frassati D, Timour Q. Opposite change with ischaemia in the antifibrillatory effects of class I and class IV antiarrhythmic drugs resulting from the alteration in ion transmembrane exchanges related to depolarization. Can J Physiol Pharmacol 2000. [DOI: 10.1139/y99-129] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is known that class I antiarrhythmic drugs lose their antifibrillatory activity with severe ischaemia, whereas class IV antiarrhythmic drugs acquire such activity. Tachycardia, which is also a depolarizing factor, has recently been shown to give rise to an alteration of ion transmembrane exchanges which is particularly marked in the case of calcium. This leads one to wonder if the change in antifibrillatory activity of antiarrhythmic drugs caused by ischaemia depends on the same process. The change in antifibrillatory activity was studied in normal conditions ranging to those of severe ischaemia with a class I antiarrhythmic drug, flecainide (1.00 mg·kg-1 plus 0.04 mg·kg-1·min-1), a sodium channel blocker, and a class IV antiarrhythmic drug, verapamil (50 µg·kg-1 plus 2 µg·kg-1·min-1), a calcium channel blocker. The experiments were performed in anaesthetized, open-chest pigs. The resulting blockade of each of these channels was assessed at the end of ischaemic periods of increasing duration (30, 60, 120, 180, 300, and 420 s) by determining the ventricular fibrillation threshold (VFT). VFT was determined by means of trains of diastolic stimuli of 100 ms duration delivered by a subepicardial electrode introduced into the myocardium (heart rate 180 beats per min). Ischaemia was induced by completely occluding the left anterior descending coronary artery. The monophasic action potential was recorded concurrently for the measurement of ventricular conduction time (VCT). The monophasic action potential duration (MAPD) varied with membrane polarization of the fibres. The blockade of sodium channels by flecainide, which normally raises VFT (7.0 ± 0.4 to 13.8 ± 0.8 mA, p < 0.001) and lengthens VCT (28 ± 3 to 44 ± 5 ms, p < 0.001), lost its effects in the course of ischaemia. This resulted in decreased counteraction of the ischaemia-induced fall of VFT and decreased aggravation of the ischaemia-induced lengthening of VCT. The blockade of calcium channels, which normally does not alter VFT (between 7.2 ± 0.6 and 8.4 ± 0.7 mA, n.s.) or VCT (between 30 ± 2 and 34 ± 3 ms, n.s.), slowed the ischaemia-induced fall of VFT. VFT required more time to reach 0 mA, thus delaying the onset of fibrillation. Membrane depolarization itself was opposed as the shortening of MAPD and the lengthening of VCT were also delayed. Consequently there is a progressive decrease in the role played by sodium channels during ischaemia in the rhythmic systolic depolarization of the ventricular fibres. This reduces or suppresses the ability of sodium channel blockers to act on excitability or conduction, and increases the role of calcium channel blockers in attenuating ischaemia-induced disorders.Key words: pigs, ion transmembrane exchanges, myocardial ischaemia, sodium channel, calcium channel.
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Watson JN, Addison PS, Clegg GR, Holzer M, Sterz F, Robertson CE. A novel wavelet transform based analysis reveals hidden structure in ventricular fibrillation. Resuscitation 2000; 43:121-7. [PMID: 10694172 DOI: 10.1016/s0300-9572(99)00127-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We report a new method of interrogating the surface ECG signal using techniques developed in the field of wavelet transform analysis. Previously unreported structure within the ECG during ventricular fibrillation (VF) is found using a high-resolution decomposition of the signal employing the continuous wavelet transform. We believe that wavelet transform methods could lead to the development of powerful tools for use in the resuscitation of patients with cardiac arrest.
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Affiliation(s)
- J N Watson
- Faculty of Engineering, Napier University, Edinburgh, UK
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11
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Clusin WT, Anderson ME. Calcium channel blockers: current controversies and basic mechanisms of action. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1999; 46:253-96. [PMID: 10332505 DOI: 10.1016/s1054-3589(08)60473-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Affiliation(s)
- W T Clusin
- Cardiology Division, Stanford University School of Medicine, California 94305, USA
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12
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Murasato Y, Nagamoto Y, Urabe T, Kuraoka F, Nakashima Y, Kuroiwa A. Effects of lidocaine and diltiazem on recovery of electrophysiologic activity during partial reperfusion following severe myocardial ischemia in canine hearts. J Electrocardiol 1997; 30:113-25. [PMID: 9141606 DOI: 10.1016/s0022-0736(97)80019-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The effects of lidocaine and diltiazem on recovery of electrophysiologic activity during partial reperfusion following severe myocardial ischemia were investigated in 28 dogs. The left anterior descending artery was ligated, and the distal end was connected to the carotid artery. Myocardial ischemia was induced by retrograde blood flow for 10 minutes, after which flow-limited reperfusion (30-60% of the coronary flow before ischemia) was performed. The dogs were divided according to the agent administered before ischemia into the following three groups: saline (group S, n = 11); lidocaine (group L, n = 8, 0.07 mg/kg/min by intravenous drip infusion following 2 mg/kg intravenous injection); and diltiazem (group D, n = 9, 0.02 mg/kg/min by intravenous drip infusion. There were no significant differences among the three groups in the incidence of ventricular tachyarrhythmia, which occurred as ventricular tachycardia (VT) or ventricular fibrillation (VF). In each group, the occurrence of VT was frequently preceded by delayed potential which was initiated after reperfusion, with depressed conduction in the epicardium, suggesting reentry (82%, 96%, and 87%, not significant). The determining factors for VT with degeneration into VF were long duration of VT in groups S and L (VT with degeneration into VF vs VT without, 1.2 +/- 0.2 seconds vs 0.6 +/- 0.1 seconds, P < .05, in group S and 11.6 +/- 2.5 seconds vs 2.2 +/- 0.4 seconds, P < .05, in group L), and decrease in average R-R interval during VT in groups L and D (195 +/- 8 ms vs 313 +/- 17 ms, P< .01, in group L and 201 +/- 11 ms vs 327 +/- 28 ms, P< 0.01, in group D). In addition, occurrence of epicardial electrophysiologic activity with reduced time from onset of the QRS complex in the surface electrocardiogram to the onset of the activity during VT preceded VF in group L (VT with degeneration into VF vs VT without, 130.0 +/- 15.1 ms vs 185.8 +/- 21.4 ms, P < .05), while that with prolongation of the time had this effect in group D (116.0 +/- 15.7 ms vs 69.0 +/- 10.7 ms, P < .05). It is concluded that, even when partial reperfusion is applied, neither lidocaine nor diltiazem suppresses VT because neither drug decreases delayed potential acting as a triggering factor or suppresses VF, since the alteration of the epicardial conductivity during VT can change the VT circuit to a smaller one.
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Affiliation(s)
- Y Murasato
- Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
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13
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Strohmenger HU, Lindner KH, Brown CG. Analysis of the ventricular fibrillation ECG signal amplitude and frequency parameters as predictors of countershock success in humans. Chest 1997; 111:584-9. [PMID: 9118691 DOI: 10.1378/chest.111.3.584] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
OBJECTIVE The purpose of this study was to assess from the ventricular fibrillation ECG signal whether certain amplitude parameters, or frequency parameters derived using fast Fourier transform analysis, are predictive of countershock success (defined as a stable supraventricular rhythm following countershock). DESIGN Retrospective, descriptive study. SETTING Emergency medical service at a university hospital. PATIENTS Twenty-six patients with out-of-hospital cardiac arrest, whose initial ECG rhythm was identified as ventricular fibrillation. METHODS AND RESULTS In all patients, advanced cardiac life support was performed in the out-of-hospital setting and a semiautomatic defibrillator was used for countershock therapy and simultaneous on-line ECG recording. For each patient, ECG data were stored in modules in digitized form over a period of 20 min and analyzed retrospectively. Using fast Fourier transform analysis of the ventricular fibrillation ECG signal in the frequency range of 0.3 to 30 Hz (mean +/- SD), median frequency, dominant frequency, edge frequency, and amplitude were as follows: 5.17 +/- 1.05 Hz, 4.56 +/- 0.99 Hz, 10.74 +/- 3.46 Hz, and 1.33 +/- 0.44 mV before successful countershock (n = 20); and 4.21 +/- 1.17 Hz (p = 0.0034), 3.31 +/- 1.57 Hz (p = 0.0004), 9.46 +/- 2.93 Hz (p = 0.5390), and 1.15 +/- 0.69 mV (p = 0.0134) before unsuccessful countershock (n = 134). Using software filters to completely eliminate interference due to manual cardiopulmonary resuscitation from the ventricular fibrillation power spectrum, only amplitude remained statistically different (p < or = 0.03) in predicting countershock success. CONCLUSIONS We conclude that in patients, median frequency, dominant frequency, and amplitude are predictive of countershock success in humans.
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Affiliation(s)
- H U Strohmenger
- Department of Anesthesiology and Critical Care Medicine, University of Ulm, Germany
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14
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Timour Q, Aupetit JF, Freysz M, Frassati D, Faucon G. Possible prevention by amlodipine of ventricular fibrillation related to brief ischemia episodes. Can J Physiol Pharmacol 1996. [DOI: 10.1139/y96-139] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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15
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Timour Q, Bui-Xuan B, Faucon G, Aupetit JF. Delay by a calcium antagonist, amlodipine, of the onset of primary ventricular fibrillation in myocardial ischemia. Cardiovasc Drugs Ther 1996; 10:447-54. [PMID: 8924058 DOI: 10.1007/bf00051109] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Calcium antagonists have been reported to counteract the increase by ischemia of vulnerability to ventricular fibrillation. This ability might be especially of interest in the prevention of sudden death subsequent to a major, but transitory, inadequacy between myocardial oxygen requirements and available coronary blood flow produced by exercise, emotion, etc., because death is then not related to irreversible damage of myocardial fibers. This study has been undertaken to examine the protective effect of a calcium antagonist on an animal model of this type of ischemia. This model used complete, but transient occlusion of the left anterior descending coronary artery near its origin during pacing at a constant high rate (180 beats/min) in anesthetized, open-chest pigs, most often resulting in fibrillation within 1-2 minutes after a progressive fall of the electrical fibrillation threshold. Amlodipine was the preferred calcium antagonist for this study because it is only moderately negatively inotropic. The results of the preventive administration of amlodipine was assessed by the time to onset of fibrillation. Amlodipine 0.30 mg/kg prolonged this time by 50-100% (p < 0.05) without appreciable impairment of blood pressure or myocardial contractility. Concurrently, amlodipine delayed the shortening of the monophasic action potential duration, the lengthening of conduction time, and the alterations of ST segments and T waves linked to ischemic depolarization. Consequently, when given experimentally before the occurrence of major, but transitory ischemia, amlodipine protected against fibrillation. Similarly, in clinical settings it ought to delay sudden death that may occur as a result of a major but transitory inadequacy between myocardial oxygen requirements and available coronary blood flow.
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Affiliation(s)
- Q Timour
- Department of Medical Pharmacology, Cl. Bernard University, Lyon, France
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16
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Strohmenger HU, Lindner KH, Keller A, Lindner IM, Pfenninger E, Bothner U. Effects of graded doses of vasopressin on median fibrillation frequency in a porcine model of cardiopulmonary resuscitation: results of a prospective, randomized, controlled trial. Crit Care Med 1996; 24:1360-5. [PMID: 8706492 DOI: 10.1097/00003246-199608000-00015] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE To assess the effects of graded doses of vasopressin vs. saline on median fibrillation frequency and defibrillation success in a porcine model of cardiopulmonary resuscitation. DESIGN Prospective, randomized, controlled trial. SETTING Animal laboratory in a university medical center. SUBJECTS Twenty-eight domestic pigs (body weight between 26 and 31 kg), aged 12 to 14 wks. INTERVENTIONS AND MAIN RESULTS After 4 mins of ventricular fibrillation and 3 mins of closed-chest cardiopulmonary resuscitation, the animals were allocated to receive either 0.2 U/kg of vasopressin (n = 7), 0.4 U/kg of vasopressin (n = 7), 0.8 U/kg of vasopressin (n = 7), or 10 mL of saline (n = 7, control group). Using radiolabeled microspheres, myocardial blood flow rates during cardiopulmonary resuscitation-before drug administration and 90 secs and 5 mins after drug administration-were as follows in the four groups (mean +/- SEM): 18.8 +/- 0.9, 17.2 +/- 1.1, and 14.6 +/- 1.4 mL/min/100 g in the control group; 17.8 +/- 2.2, 49.6 +/- 6.3 (p < .01 vs. control group), and 29.4 +/- 3.1 mL/min/100 g (p < .05 vs. control group) in the group receiving 0.2 U/kg of vasopressin; 17.1 +/- 1.0, 52.4 +/- 7.5 (p < .01 vs. control group), and 52.2 +/- 5.8 mL/min/100 g (p < .001 vs. control group) in the group receiving 0.4 U/kg of vasopressin; and 18.1 +/- 1.6, 94.9 +/- 9.2 (p < .001 vs. control group), and 57.2 +/- 6.3 mL/min/100 g (p < .001 vs. control group) in the group receiving 0.8 U/kg of vasopressin. Using spectral analysis, median frequencies of ventricular fibrillation-before drug administration and 90 secs and 5 mins after drug administration-were as follows in the four groups: 9.6 +/- 0.4, 8.5 +/- 0.8, and 7.2 +/- 1.0 Hz in the control group; 9.7 +/- 0.5, 12.9 +/- 0.8 (p < .01 vs. control group), and 12.7 +/- 0.8 Hz (p < .001 vs. control group) in the group receiving 0.2 U/kg of vasopressin; 10.3 +/- 0.2, 12.7 +/- 0.9 (p < .01 vs. control group), and 12.8 +/- 0.7 Hz (p < .001 vs. control group) in the group receiving 0.4 U/kg of vasopressin; and 10.0 +/- 0.9, 14.1 +/- 0.9 (p < .001 vs. control group), and 12.5 +/- 0.9 Hz (p < .001 vs. control group) in the group receiving 0.8 U/kg of vasopressin at the same points in time. Median frequency before the first defibrillation attempt was 12.3 +/- 0.4 Hz in the resuscitated animals (n = 19) and 8.2 +/- 1.2 Hz in the nonresuscitated animals (n = 9) (p < .001). CONCLUSIONS This study contributes to the characterization of the effect of increasing global myocardial blood flow on median fibrillation frequency after administration of graded doses of vasopressin in a porcine model of ventricular fibrillation. Interventions such as vasopressor treatment that increase fibrillation frequency improve the chance of successful defibrillation.
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Affiliation(s)
- H U Strohmenger
- Department of Anesthesiology and Critical Care Medicine, University of Ulm, Germany
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17
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Strohmenger HU, Lindner KH, Prengel AW, Pfenninger EG, Bothner U, Lurie KG. Effects of epinephrine and vasopressin on median fibrillation frequency and defibrillation success in a porcine model of cardiopulmonary resuscitation. Resuscitation 1996; 31:65-73. [PMID: 8701111 DOI: 10.1016/0300-9572(95)00899-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE This study was designed to assess whether median frequency of ventricular fibrillation (VF) correlates with myocardial blood flow and defibrillation success during cardiopulmonary resuscitation (CPR) after epinephrine or vasopressin administration. METHODS AND RESULTS After 4 min of VF and 3 min of CPR, 14 pigs received 0.045 mg/kg epinephrine or 0.4 U/kg vasopressin. Using radio-labeled microspheres, median myocardial blood flow during CPR before, and 90 s and 5 min after drug administration (DA) was 15.5 (12.6, 23.1; 25th percentile, 75th percentile), 26.4 (18.5, 29.1), 16.9 (14.9, 19.1) mL min-1 100 g-1, respectively, in the epinephrine, and 16.9 (15.4, 18.9), 48.1 (36.9, 68.9) (P < 0.05 vs. before DA), 52.3 (38.5, 65.0) mL min-1 100 g-1, respectively, in the vasopressin group. Using spectral analysis of VF, median frequency of VF was 11.0 (10.7, 11.8), 11.3 (9.6, 13.1), 10.2, (8.8, 11.4) Hz, respectively, in the epinephrine, and 10.1 (10.0, 10.5), 11.7 (11.1, 14.2) (P < 0.05 vs. before DA), 13.2 (11.5, 13.9) Hz, respectively, in the vasopressin group at the same points in time. Median frequency correlates significantly with myocardial blood flow in the epinephrine (n = 21); rs = 0.772; P < 0.001) and in the vasopressin group (n = 21; rs = 0.905; P < 0.001). Median fibrillation frequency before the first defibrillation was 13.0 (12.2, 13.2) Hz in resuscitated (n = 8) and 9.2 (8.3, 10.2) Hz (n = 6) in non-resuscitated animals (P < 0.01). CONCLUSIONS We conclude that median frequency of VF reflects myocardial blood flow and the chance of successful defibrillation during closed-chest CPR after vasopressor treatment in a porcine model of VF.
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Affiliation(s)
- H U Strohmenger
- Department of Anesthesiology and Critical Care Medicine, University of Ulm, Germany
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18
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Freysz M, Timour Q, Bernaud C, Bertrix L, Faucon G. Cardiac implications of amlodipine-dantrolene combinations. Can J Anaesth 1996; 43:50-5. [PMID: 8665636 DOI: 10.1007/bf03015958] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
PURPOSE Cardiac disorders, cardiac arrest and ventricular fibrillation in the most severe cases, have been observed after the administration of dantrolene to patients treated by verapamil for coronary artery disease. This study was designed to examine the interaction of dantrolene with amlodipine, a dihydropyridine. METHODS In 12 anaesthetized, open-chest pigs, the effects of the interaction have been studied on heart rate, atrioventricular conduction, monophasic action potential duration, intraventricular conduction time, left ventricular dP/dt max and mean blood pressure. The study was performed with normal coronary circulation and ischaemia of a large area of the left ventricule, obtained by complete occlusion of the left anterior descending coronary artery near its origin, under pacing at a constant high rate, 180 beats.min-1. The drugs were injected iv, amlodipine 0.4 mg.kg-1 first and dantrolene 3.0 mg.kg-1 20 min later in six animals and the order was reversed in the other animals. RESULTS Sinus rate and atrioventricular conduction were not affected by amlodipine, but were slowed by dantrolene added (145 +/- 9 to 131 +/- 7 beats.min-1, P < 0.01 and 150 +/- 15 to 180 +/- 20 msec, P < 0.01). In contrast, amlodipine or amlodipine plus dantrolene did not change MAP duration or conduction time in the normal heart. Similarly, they did not alter the maximal variations due to ischaemia, but delayed them, while prolonging the time to onset of fibrillation (111 +/- 8 to 343 +/- 33 sec. P < 0.001 with amlodipine alone, 289 +/- 11 to 323 +/- 16 sec, P < 0.05 with dantrolene). Left ventricular dP/dt max was lowered from 1670 +/- 86 to 1532 +/- 50 mmHg.sec-1 (P < 0.001) and mean blood pressure from 79 +/- 4 to 70 +/- 3 mmHg (P < 0.01) by amlodipine, but dantrolene did not enhance and even counteracted these effects. Finally, potassium plasma concentration did not increase above 5.1 +/- 0.2 mmol.L-1 under the dual influence of amlodipine and dantrolene. CONCLUSION In usual clinical doses, dantrolene may be safely administered concurrently with amlodipine.
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Affiliation(s)
- M Freysz
- Department of Anesthesiology and Intensive Care, General Hospital, Dijon
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19
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Bianchetti G, Bagheri H, Houin G, Dubruc C, Thénot JP. Pharmacokinetic and bioavailability of diltiazem sustained-release: influence of food and time of administration. Fundam Clin Pharmacol 1995; 9:197-201. [PMID: 7628834 DOI: 10.1111/j.1472-8206.1995.tb00281.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Diltiazem is a calcium channel blocking agent known to be effective in the treatment of angina pectoris, hypertension and supraventricular arrhythmias. To improve the conditions of diltiazem administration in the treatment of hypertensive patients, a sustained-release formulation (Mono-Tildiem LP 300 mg) allowing a single daily oral administration has been developed. The aim of the present study was to first evaluate the influence of food intake and second to evaluate those of the time of administration on the pharmacokinetic parameters and the bioavailability of this sustained-release formulation. The influence of these factors was investigated over two different open, randomized, cross-over studies in 12 healthy volunteers. Although a significant decrease in Tmax and an increase in Cmax occurred when diltiazem sustained-release was administered with food intake, AUC0-48, and therefore the fraction absorbed, were not modified either by concurrent food intake or by different times of administration. The minor modifications of pharmacokinetic parameters of diltiazem sustained release observed were unlikely to induce any clinical consequence.
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Affiliation(s)
- G Bianchetti
- Department of Clinical Research, Synthélabo Recherche (LERS), Bagneux, France
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20
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Aupetit JF, Timour Q, Chevrel G, Loufoua-Moundanga J, Omar S, Faucon G. Attenuation of the ischaemia-induced fall of electrical ventricular fibrillation threshold by a calcium antagonist, diltiazem. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1993; 348:509-14. [PMID: 8114951 DOI: 10.1007/bf00173211] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Calcium antagonists have been reported to decrease the incidence of sudden death in postinfarction management and vulnerability to fibrillation secondary to experimental coronary occlusion. In order to confirm such beneficial results regarding ischaemic ventricular fibrillation, the threshold intensity for fibrillation electrically induced with impulses of 100 ms and 180 beats.min-1 was measured during the course of ischaemias obtained by total occlusion of the left anterior descending coronary artery near its origin in open-chest pigs. The variations of electrical fibrillation threshold with ischaemia duration (30, 60, 120, 180, 240, 360 s) were compared under control conditions and after i.v. diltiazem (0.50 mg.kg-1 plus 0.02 mg.kg-1.min-1 over 25 min). Electrical fibrillation threshold was not influenced by diltiazem before, but raised during ischaemia, particularly from the 60th s (1.7 to 4.0 mA), with delay in the triggering of fibrillation which occurs when the fibrillation threshold falls down to the pacing threshold (0.2 to 0.3 mA). In 6 pigs out of 8, fibrillation was even avoided in the longest of the ischaemic periods considered (360 s), for fibrillation threshold ceased falling before reaching the critical level. These experimental results obtained with diltiazem are consistent with the clinical effectiveness of calcium antagonists recently observed in the prevention of postinfarction sudden death, provided that myocardial contractility is not too much adversely affected. But, left ventricular dP/dtmax was not reduced by more than 6.8% in the present experiments.
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Affiliation(s)
- J F Aupetit
- Department of Medical Pharmacology, Claude Bernard University, Lyon, France
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21
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Baxter GF, Yellon DM. Attenuation of reperfusion-induced ventricular fibrillation in the rat isolated hypertrophied heart by preischemic diltiazem treatment. Cardiovasc Drugs Ther 1993; 7:225-31. [PMID: 8357776 DOI: 10.1007/bf00878512] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The ability of the calcium antagonist diltiazem to protect against reperfusion-induced arrhythmias in hypertrophied myocardium was studied. Hearts from normotensive and DOCA-salt hypertensive rats were Langendorff perfused and subjected to 10 minutes of stabilization, 10 minutes of left coronary artery occlusion, and 5 minutes of reperfusion. The incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) during reperfusion were determined and the effects of diltiazem or vehicle (given as a single bolus 3 minutes before coronary artery occlusion) were assessed in hypertrophied and normal hearts. In vehicle-treated (control) hypertrophied hearts, VF incidence was 91% compared with 67% in normal hearts, and the median duration of VF was 272 seconds (mean 207.4 +/- 32.3) compared with 27 seconds (mean 110.6 +/- 36.6; p < 0.05), respectively, suggesting that reperfusion VF is more severe in hypertrophied hearts. In normal hearts, diltiazem 18 micrograms reduced VT incidence from 92% to 55%, reduced VF from 67% to 27%, and sustained VF from 42% to 9%. In hypertrophied hearts, 18 micrograms diltiazem reduced the VT incidence from 100% to 58%, reduced VF from 91% to 25% (p < 0.01), and sustained VF from 82% to 8% (p < 0.01). Median VF duration in this group was reduced to 0 seconds (p < 0.05; mean 24.7 +/- 22.6). Diltiazem did not significantly affect heart rate or coronary flow rate decreases during ischemia. However, developed tension, at the onset of ischemia, was lower in diltiazem-treated groups than in the control groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G F Baxter
- Department of Pharmacology, De Montfort University, Leicester, UK
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22
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Kralios AC, Anderson FL, Kralios FA. Protective effect of coronary sinus obstruction from primary ischemia-induced ventricular fibrillation in the dog. Am Heart J 1993; 125:987-95. [PMID: 8465771 DOI: 10.1016/0002-8703(93)90105-i] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We examined whether partial coronary sinus obstruction affects the latency of the early ventricular fibrillation (VF) of acute ischemia. During baseline trials 15 of 19 open-chest dogs fibrillated repeatedly and predictably within 2 to 5 minutes (251.6 +/- 64 seconds) after reversible, double coronary artery occlusion without developing profound hemodynamic deterioration. The effect of partial coronary sinus obstruction sufficient to increase coronary sinus pressure to 40 mm Hg could be adequately tested in 11 dogs. Coronary sinus obstruction consistently prevented VF in five dogs, significantly prolonged the VF latency in three (p < 0.01 to p < 0.001), and had no clear effect in another three. The overall effect was significant at the p < 0.01 level. VF latency prolongation/prevention was also positively correlated to the residual coronary sinus pressure at the time of VF (r = 0.76; p < 0.008), as well as the baseline VF latency (r = 0.75; (p < 0.008). The protective effect of coronary venous hypertension most likely reflects preservation of adequate extracellular fluid in the ischemic region after the perfusion arrest. This extracellular fluid may constitute a key component in the prevention of early ischemic arrhythmias by preserving interstitial hydraulic continuity and tissue homogeneity through enhanced dilution and diffusion of solutes.
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Affiliation(s)
- A C Kralios
- Cardiology Section, Department of Veterans Affairs Medical Center, Salt Lake City, Utah 84148
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23
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Nánási PP, Knilans TK, Varró A, Murphy AM, Fujiki A, Schwartz A, Lathrop DA. Active and passive electrical properties of isolated canine cardiac Purkinje fibers under conditions simulating ischaemia: effect of diltiazem. PHARMACOLOGY & TOXICOLOGY 1992; 71:52-6. [PMID: 1523194 DOI: 10.1111/j.1600-0773.1992.tb00520.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effect of a calcium channel blocker diltiazem on the electrical properties of canine Purkinje fibers superfused in a milieu similar to that occurring in acute myocardial ischaemia was studied. Action potential parameters, passive electrical properties, and conduction velocity were measured using conventional microelectrode techniques. Superfusion with glucose-free Tyrode's solution containing 9 mM K+, gassed with 100% N2 at pH = 6.5 ('ischemic solution') significantly reduced the maximal diastolic potential, action potential duration, maximal upstroke velocity, conduction velocity and length constant, while input resistance and longitudinal resistance were elevated and membrane resistance remained unchanged. Diltiazem (1 microM) alone reduced only the action potential duration, while all other parameters were unaffected. Pretreatment with diltiazem did not fully prevent the effects of ischemic superfusion; however, the ischaemia-induced decrease in length constant was not significant in the presence of diltiazem. In addition, the increase in longitudinal resistance during ischaemia was significantly reduced following diltiazem pretreatment. This decrease in longitudinal resistance may contribute to the improvement of ischaemia-induced conduction delay observed in intact animals and may be related to a reduction of ischaemia-induced increase in intracellular free Ca2+.
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Affiliation(s)
- P P Nánási
- Department of Paediatrics (Cardiology), University of Cincinnati College of Medicine, OH
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24
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Stefenelli T, Wikman-Coffelt J, Wu ST, Parmley WW. Intracellular calcium during pacing-induced ventricular fibrillation. Effects of lidocaine. J Electrocardiol 1992; 25:221-8. [PMID: 1645062 DOI: 10.1016/0022-0736(92)90007-m] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hemodynamics and endocardial [Ca2+]i transients were studied during ventricular fibrillation in isolated perfused rat hearts. During 1 minute of pacing-induced ventricular fibrillation, the diastolic fibrillatory [Ca2+]i level increased significantly (p less than 0.001) above the end-systolic [Ca2+]i concentration of the last regular contraction. A bolus of lidocaine led to a decrease in the [Ca2+]i level during fibrillation (p less than 0.007) to the end-diastolic level of baseline conditions and then subsequently converted the heart to sinus rhythm. In 13 (62%) of the 21 studies described, post-lidocaine ventricular fibrillation converted to a brief period of asystole followed by sinus rhythm; in 8 (38%) of the studies, post-lidocaine ventricular fibrillation switched to ventricular tachycardia. Postfibrillatory cardiac dysfunction was related to the duration and degree of elevated diastolic [Ca2+]i. The authors conclude that [Ca2+]i levels are increased during ventricular fibrillation, and that lidocaine treatment leads to a prompt decrease in [Ca2+]i preceding conversion to sinus rhythm.
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Affiliation(s)
- T Stefenelli
- Department of Medicine, University of California, San Francisco 94143
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25
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Rabkin SW. The calcium antagonist diltiazem has antiarrhythmic effects which are mediated in the brain through endogenous opioids. Neuropharmacology 1992; 31:487-96. [PMID: 1528399 DOI: 10.1016/0028-3908(92)90088-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The purpose of this study was to examine the hypothesis that the calcium channel blocker, diltiazem, modulates catecholamine-induced arrhythmias through CNS mechanisms. Rats, that had catheters previously inserted into the lateral cerebral ventricle and femoral artery, received diltiazem, 10 or 50 micrograms/kg or the diluent, into the lateral cerebral ventricle (i.c.v.). Epinephrine was infused to produce arrhythmias. The onset of ventricular arrhythmias, premature ventricular complexes, occurred at a significantly (P less than 0.05) greater dose of epinephrine, after diltiazem, compared to the control group and in a dose-dependent manner, with the mean (+/- 1 SEM) dose of epinephrine being 198 +/- 5, 175 +/- 13 and 115 +/- 15 micrograms/kg in the groups treated with 50 and 10 micrograms/kg of diltiazem and the control groups, respectively. The development of fatal arrhythmias, mainly ventricular tachyarrhythmias, occurred at significantly (P less than 0.05) greater concentrations of epinephrine with diltiazem, 50 and 10 micrograms/kg, 225 +/- 5 and 183 +/- 13 micrograms/kg, respectively, compared to controls, 131 +/- 15 micrograms/kg. Endogenous opioids of the mu-type were implicated in this action of diltiazem, because the mu opioid antagonist naloxone, 1 mg/kg (i.v.), significantly (P less than 0.05) antagonized the antiarrhythmic effects of centrally administered diltiazem and the mu opioid agonist DAGO (i.c.v.), did not further enhance the suppression of epinephrine-induced arrhythmias, produced by diltiazem, 50 micrograms/kg. Atropine sulfate, which crosses the blood-brain barrier and atropine methylnitrate, which does not enter the brain, each at 1 mg/kg (i.v.), produced an equal and significant antagonism of the effect of diltiazem, 50 micrograms/kg, that was less than that of naloxone. The combination of naloxone plus atropine sulfate completely prevented the effect of diltiazem, 50 micrograms/kg, on arrhythmias. The antiarrythmic action of diltiazem could not be explained by alteration of the blood pressure or heart rate response to epinephrine. The results suggest that: (a) calcium channels on neurons in the CNS play an important role in the modulation of epinephrine-induced cardiac arrhythmias, (b) diltiazem can suppress arrhythmias through CNS mechanisms, (c) activation of the parasympathetic nervous system mediates some of the effect of diltiazem, but (d) the mechanism of action of diltiazem is modulated through endogenous opioids.
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Affiliation(s)
- S W Rabkin
- Department of Medicine (Cardiology), University Hospital (Shaughnessy), University of British Columbia, Vancouver, Canada
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26
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Timour Q, Larbre JP, Aupetit JF, Gerentes-Chassagne I, Loufoua-Moundanga J, Kioueh I, Faucon G. Protection against ischaemic ventricular fibrillation by blocking agents of myocardial cell calcium influx. Electrophysiological study in the pig in situ heart. Fundam Clin Pharmacol 1991; 5:641-4. [PMID: 1778542 DOI: 10.1111/j.1472-8206.1991.tb00753.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Q Timour
- Department of Medical Pharmacology, Claude Bernard University, Lyon, France
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27
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Higginson L, Tang A, Knoll G, Calvin J. Effect of intracoronary diltiazem on infarct size and regional myocardial function in the ischemic reperfused canine heart. J Am Coll Cardiol 1991; 18:868-75. [PMID: 1869751 DOI: 10.1016/0735-1097(91)90814-p] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
This study was designed to investigate whether intracoronary diltiazem given before reperfusion could enhance myocardial salvage in the canine heart. Twenty-five dogs were subjected to 90 min of coronary occlusion followed by 4 h of reperfusion. The dogs were assigned to one of three experimental groups. The early diltiazem group received intracoronary diltiazem into the distal coronary bed at the onset of coronary occlusion and for 60 min after reperfusion. The late diltiazem group received the same amount of drug beginning 15 min before reperfusion and the control group received saline solution for 90 min of occlusion and 60 min of reperfusion. Infarct size expressed as a percent of the area at risk was significantly smaller in the early and late diltiazem groups (15.6 +/- 3.6% and 21.2 +/- 5.1%, respectively) than in the control group (49 +/- 4.6%) (p less than 0.05). Intracoronary diltiazem restored systolic function of the stunned, previously ischemic tissue to essentially normal preocclusion values. Segmental shortening after reperfusion averaged 21.6% in the early diltiazem group versus 0 +/- 1.7% and 7.3 +/- 4% for the control and late diltiazem groups, respectively (p less than 0.05). Low dose intracoronary diltiazem did not alter hemodynamic variables or myocardial blood flow but did improve segmental shortening 2 and 6 h after reperfusion. These data indicate that intracoronary diltiazem given during occlusion or just before reperfusion increases the salvage of myocardium compared with the salvage achieved by reperfusion alone. These results also suggest that intracoronary diltiazem given during the ischemic period enhances systolic contractile function of postischemic stunned myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Higginson
- University of Ottawa Heart Institute, Ontario, Canada
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28
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Lee JA, Allen DG. Mechanisms of acute ischemic contractile failure of the heart. Role of intracellular calcium. J Clin Invest 1991; 88:361-7. [PMID: 1864950 PMCID: PMC295338 DOI: 10.1172/jci115311] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- J A Lee
- University of Newcastle upon Tyne, Department of Pathology, Royal Victoria Infirmary, United Kingdom
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Stefenelli T, Wikman-Coffelt J, Wu ST, Parmley WW. Calcium-dependent fluorescence transients during ventricular fibrillation. Am Heart J 1990; 120:590-7. [PMID: 2389696 DOI: 10.1016/0002-8703(90)90016-q] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Using surface fluorometry, calcium-dependent fluorescence transients were recorded during ventricular fibrillation in perfused rat and hamster hearts loaded with INDO 1-AM (fluorimetric reagent for calcium ion). Among a series of 203 consecutive isolated heart studies, 13 instances of ventricular fibrillation occurred. These arrhythmias developed during pretreatment with isoproterenol, dobutamine, norepinephrine, phenylephrine, digoxin, and 4 mmol/L calcium in the perfusate. Alternans behavior of calcium transients occurred in three cases; premature beats preceded ventricular fibrillation in six cases. Premature beats led to a further increase in the free intracellular calcium ([Ca2+]i) concentration, resulting in a stronger contraction with the subsequent beat and/or the initiation of ventricular fibrillation. Two distinct patterns of calcium transients were seen: ventricular fibrillation type 1 showed fast disorganized transients with small amplitude and an irregular, nonuniform tracing; type 2 revealed fast activity and multiform, polymorphous transients with marked changes in amplitude. Independent of the morphologic type of fibrillation, [Ca2+]i remained constant or even increased during an observation time up to 9 minutes. No intracellular hypocalcemia was observed. Isoproterenol pretreatment resulted in [Ca2+]i levels in the range of the end-diastolic calcium level of the last regular contraction. Fibrillating calcium transients after norepinephrine, dobutamine, phenylephrine, digoxin, high calcium, and fast pacing were in the previous end-systolic range. It is suggested that inotropic agents acting without a major elevation of cyclic adenosine monophosphate result in higher [Ca2+]i.
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Affiliation(s)
- T Stefenelli
- Department of Medicine (Cardiology), University of California, San Francisco
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31
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Kinoshita K, Mitani A, Hearse DJ, Braimbridge MV, Manning AS. Reperfusion-induced arrhythmias in the conscious rat: a comparative study with three calcium antagonists. J Surg Res 1989; 47:166-72. [PMID: 2755121 DOI: 10.1016/0022-4804(89)90083-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of three calcium antagonists (diltiazem, verapamil, and nifedipine) on reperfusion-induced arrhythmias were compared in a conscious rat preparation with coronary artery occlusion and implanted electrocardiogram limb electrodes. Upon reperfusion after a 5-min period of occlusion, all (15/15) untreated control rats exhibited immediate ventricular tachycardia, which rapidly deteriorated to ventricular fibrillation; 87% (13/15) of the rats died as a consequence of these rhythm disturbances. In the groups treated with calcium antagonists, each drug (diltiazem, verapamil, or nifedipine) was given as an intravenous bolus 10 min prior to coronary occlusion (n = 12 in each group). The incidence of ventricular fibrillation was significantly reduced by all three calcium antagonists and this antifibrillatory effect resulted in a significantly lower mortality in all drug-treated groups. With diltiazem (0.5 and 2.0 mg/kg) mortality fell from 87 to 42% (P less than 0.05) and 35% (P less than 0.01), respectively; with verapamil (0.5 and 5.0 mg/kg) it fell to 25% (P less than 0.01) and 0% (P less than 0.001); and with nifedipine (5.0 and 50 micrograms/kg), it fell to 25% (P less than 0.01) and 8% (P less than 0.001). At a dose of 5.0 mg/kg, verapamil caused a large reduction in heart rate both prior to and during coronary occlusion and reperfusion; however, with other doses and drugs no significant changes in heart rate were observed. ST segment elevation during the 5-min ischemic period was reduced by pretreatment with all drugs. In conclusion, in the conscious rat, pretreatment with diltiazem, verapamil, or nifedipine affords some protection against reperfusion-induced arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- K Kinoshita
- Department of Cardiovascular Surgery, Kyushu University School of Medicine, Fukuoka, Japan
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Batchelor AJ, Kruyer WB, Hickman JR. Ventricular ectopy in totally symptom-free subjects with defined coronary artery anatomy. Am Heart J 1989; 117:1265-70. [PMID: 2471400 DOI: 10.1016/0002-8703(89)90405-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ambulatory ECG recordings were obtained from 313 consecutive, totally symptom-free male subjects on whom cardiac catheterization was subsequently performed for occupational reasons. These recordings were examined for ventricular ectopy and the results were studied in relation to the findings on selective coronary angiography. Ventricular ectopy was a common finding, with 58% of those subjects with normal coronary artery anatomy having at least one ventricular premature beat during the period of monitoring (mean 16 1/2 hours), 22% having greater than one such complex per hour, and 10% having greater than 10 per hour. Complex ventricular ectopy was present in 21% of the normal subjects. No association between the extent or complexity of ventricular ectopy and the presence or grade of anatomic coronary artery disease was demonstrated, nor was ventricular ectopy overrepresented in those with both significant coronary artery disease on angiography and evidence of ischemia on provocative testing.
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Affiliation(s)
- A J Batchelor
- Clinical Sciences Division, USAF School of Aerospace Medicine, Brooks Air Force Base
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33
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Blake K, Clusin WT, Franz MR, Smith NA. Mechanism of depolarization in the ischaemic dog heart: discrepancy between T-Q potentials and potassium accumulation. J Physiol 1988; 397:307-30. [PMID: 3411509 PMCID: PMC1192127 DOI: 10.1113/jphysiol.1988.sp017003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
1. To study the origin of ischaemic myocardial depolarization, the diastolic surface potential - T-Q depression-was correlated with subepicardial extracellular K+ accumulation during serial episodes of widespread ischaemia in open-chest dogs, and in isolated, blood-perfused canine hearts. Placement of the reference electrode on a small island of non-ischaemic myocardium simplified the interpretation of the T-Q potentials. 2. In some experiments, changes in resting potential in the ischaemic zone were recorded using a 'contact' monophasic action potential (MAP) electrode. The change in MAP resting potential was linearly related to T-Q depression for a wide range of experimental conditions (R greater than 0.98). T-Q depression is therefore a linear index of depolarization in superficial myocardial cells. 3. The validity of T-Q depression as a 'measure' of local cellular depolarization was further tested by infiltration of isotonic KCl into the superficial myocardium subjacent to the ischaemic zone electrode. Resulting T-Q depression was 2- to 3-fold larger than the maximum values obtained in ischaemia; and the ratio of T-Q depression to the amplitude of the accompanying monophasic potential was consistent with the assumption that KCl had fully depolarized the underlying myocardium (delta Vm = 89 mV). KCl prevented (i.e. occluded) further changes in the T-Q potential during ischaemia. KCl did not have these effects if it was introduced at sites more remote from the electrode (greater than 4 mm). 4. Ischaemic T-Q depression was drastically accelerated by increasing the heart rate from 90 to 180 beats/min and was further accelerated by arterial infusion of CaCl2. These effects were most striking during the first minute of ischaemia. 5. In contrast, the above manoeuvres produced little acceleration of subepicardial K+ accumulation. After CaCl2 infusion, large ischaemic potentials, severe conduction impairment, and arrhythmias could be observed when K+ activity was almost normal (aK = 4.0-4.5 mM). 6. T-Q depression was larger in vivo than in isolated hearts, both absolutely and relative to K+ accumulation. 7. Based on the reproducible amplitude of ischaemic epicardial potential-estimates of cellular depolarization (delta Vm) could be obtained, which were compared with the concurrent change in K+ electrode potential (delta EK) for each experimental condition. 8. Estimated depolarization was nearly identical to delta EK in isolated hearts under basal conditions. However, depolarization significantly exceeded delta EK during rapid pacing, CaCl2 infusion, or during paced occlusions performed in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- K Blake
- Falk Cardiovascular Research Center, Stanford University School of Medicine, CA 94305
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Opie LH, Coetzee WA, Dennis SC, Thandroyen FT. A potential role of calcium ions in early ischemic and reperfusion arrhythmias. Ann N Y Acad Sci 1988; 522:464-77. [PMID: 3288056 DOI: 10.1111/j.1749-6632.1988.tb33386.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- L H Opie
- Department of Medicine, University of Cape Town Observatory, South Africa
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35
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Gülker H, Haverkamp W, Hindricks G, Bender F. Calcium antagonists and acute myocardial ischemia: comparative effects of gallopamil and nifedipine on ischemia-induced and reperfusion-induced ventricular arrhythmias, epicardial conduction times, and ventricular fibrillation thresholds. Cardiovasc Drugs Ther 1987; 1:367-76. [PMID: 3154673 DOI: 10.1007/bf02209078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The comparative effects of the calcium-antagonists gallopamil and nifedipine on ischemia-induced and reperfusion-induced ventricular arrhythmias, particularly ventricular fibrillation (VF), were assessed in a total of 40 mongrel dogs in two experimental preparations. In part I of the study, changes in the time course of spontaneous ventricular arrhythmias and VF parallel to changes in epicardial conduction following acute coronary artery occlusion lasting 20 minutes and followed by subsequent reperfusion were determined. In part II, repeated coronary artery occlusions (20 min) followed by reperfusion (60 min) were performed, and changes in ventricular fibrillation threshold (VFT) were assessed. Gallopamil proved to be highly effective in preventing ventricular arrhythmias and VF following coronary delay was reduced. The ischemia-induced fall in conduction delay was reduced. The ischemia-induced fall in VFT occurring during the first few minutes after occlusion (phase Ia) was significantly reduced. In contrast, nifedipine failed to influence the incidence of ventricular arrhythmias and VF. Following reperfusion, neither drug reduced the incidence of VF nor the associated fall in VFT at the onset of reperfusion. The time course of recovery of epicardial conduction was not affected by either drug. However, the increase in the VFT during the early postreperfusion period was significantly enhanced by both agents. The effects of gallopamil were more pronounced than those of nifedipine. Delayed reperfusion ventricular arrhythmias arising 5 to 10 minutes after release of coronary artery obstruction were significantly reduced by gallopamil whereas nifedipine proved ineffective. The results show that calcium antagonists display direct antiarrhythmic and cardioprotective actions in acute transient myocardial ischemia. The different effectiveness of gallopamil compared to nifedipine can be explained by differences in electrophysiological properties of the drugs. Enhanced ventricular vulnerability following acute transient coronary artery occlusion and subsequent release of coronary artery obstruction, first described by Tennant and Wiggers, has been extensively investigated over the past decade in a variety of experimental and clinical settings. However, the basic mechanisms underlying ischemia- and reperfusion-induced ventricular arrhythmias and ventricular fibrillation (VF) have not yet been fully elucidated. Furthermore, the results of pharmacological approaches to prevent ventricular arrhythmic activity are conflicting. The present study aimed to evaluate the antiarrhythmic efficacy of calcium antagonists in acute myocardial ischemia and reperfusion. We have examined the effects of gallopamil and nifedipine on the time course of ventricular arrhythmias during the first 20 minutes after acute coronary artery occlusion and subsequent reperfusion. We have studied the underlying mechanisms by mapping epicardial conduction and by assessing the electrically induced ventricular fibrillation threshold (VFT) both within and outside ischemic areas.
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Affiliation(s)
- H Gülker
- University Hospital, Department of Cardiology-Angiology, Muenster, West Germany
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Clusin WT. What is the solution to sudden cardiac death: calcium modulation or arrhythmia clinics? Cardiovasc Drugs Ther 1987; 1:335-42. [PMID: 3154668 DOI: 10.1007/bf02209072] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- W T Clusin
- Falk Cardiovascular Research Center, Stanford University School of Medicine, California 94305
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37
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Lee HC, Smith N, Mohabir R, Clusin WT. Cytosolic calcium transients from the beating mammalian heart. Proc Natl Acad Sci U S A 1987; 84:7793-7. [PMID: 3478728 PMCID: PMC299387 DOI: 10.1073/pnas.84.21.7793] [Citation(s) in RCA: 109] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
To elucidate the role of cytosolic calcium, [Ca2+]i, in the physiology of the normal and ischemic heart, we have developed a method for recording [Ca2+]i transients from the epicardial surface of the rabbit ventricle after arterial perfusion with the cell-permeant cytosolic calcium indicator indo-1 AM. Hearts were illuminated at 360 nm, and fluorescence was recorded simultaneously at 400 and 550 nm. The F400/F550 fluorescence ratio was calculated by an analog circuit that allowed cancelation of small movement artifacts that were present at single wavelengths. Clear [Ca2+]i transients were present in the F400/F550 signal and were remarkable for their slow decay. Slow decay of the transients was not due to buffering of [Ca2+]i by indo-1, since there was no associated impairment of contraction or relaxation. The peak amplitude of the [Ca2+]i transients was increased by ouabain, adrenaline, postextrasystolic potentiation, and acetylcholine. The extent to which the transients decayed diminished with shortening of the interbeat interval, but decay of the transients could be further diminished by acetylcholine or caffeine. A major advantage of the intact heart over isolated myocytes is the ability to measure changes in [Ca2+]i during ischemia. Ischemia produced a marked increase in both peak systolic and end-diastolic [Ca2+]i, which was most rapid during the first 30 sec, and approached a plateau value after 90 sec. This increase in [Ca2+]i was associated with a characteristic broadening of the peak of the transient. The increase in [Ca2+]i during ischemia is consistent with a proposed causative role of [Ca2+]i in mediating early electrophysiological abnormalities.
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Affiliation(s)
- H C Lee
- Division of Cardiology, Stanford University School of Medicine, CA 94305
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Garcia-Dorado D, Théroux P, Fernandez-Avilés F, Elizaga J, Solares J, Galinanes M. Diltiazem and progression of myocardial ischemic damage during coronary artery occlusion and reperfusion in porcine hearts. J Am Coll Cardiol 1987; 10:906-11. [PMID: 3655155 DOI: 10.1016/s0735-1097(87)80287-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
This study was designed to investigate whether a cardioprotective intervention could delay the completion of necrosis so that subsequent reperfusion would be more useful. Thirty-six pigs were randomly allocated to treatment with diltiazem (15 micrograms/kg per min) or saline solution and to a 60 or 120 minute coronary occlusion period followed by reperfusion. The treatment was begun 15 minutes before coronary occlusion and terminated 75 minutes after reperfusion. Twenty-four hours after the procedure, the heart was sliced and incubated in triphenyltetrazolium chloride. The infarct area and the maximal transmural area of extension of the infarct were calculated by planimetry. The total number of red blood cells in a transmural section was also counted. In the pigs with a 60 minute coronary occlusion, diltiazem (compared with saline solution) significantly reduced infarct size from 9.7 +/- 1.5% of left ventricular mass to 5.9 +/- 0.6% (p less than 0.05) and the percent transmural extension from 0.72 +/- 0.05 to 0.61 +/- 0.05% (p less than 0.05). Red blood cell extravasation in the infarcted area was reduced from 161,934 +/- 59,905 to 78,525 +/- 46,484 cells/mm3 (p less than 0.05) with diltiazem and the percent transmural extension of the hemorrhagic necrosis from 70 +/- 10 to 36 +/- 15% (p less than 0.05). No such differences were observed in the 120 minute coronary occlusion groups. Mean red blood cell counts and the extent of hemorrhagic necrosis did not correlate with either infarct size or transmural extension.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D Garcia-Dorado
- Servicio de Cardiologia, Hospital Provincial de Madrid, Spain
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Budden M, Kirchengast M, Zhang KM, Meesmann W. Effects of the calcium antagonist gallopamil on the increase of myocardial extracellular potassium activity during LAD occlusion in dogs. Basic Res Cardiol 1987; 82:279-89. [PMID: 2443124 DOI: 10.1007/bf01906860] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
It has been implied that the increase of myocardial extracellular potassium activity [( K+]e) in the early stage of acute myocardial ischemia is a major cause of the increased likelihood of arrhythmia after acute coronary artery occlusion. There is also experimental evidence that some calcium antagonists reduce the occurrence of ischemia-induced early ventricular arrhythmias. In order to clarify the antiarrhythmic effect of gallopamil during the early phase of acute LAD occlusion, the influence of this calcium antagonist on the time course of [K+]e during acute ischemia was measured in open-chest anesthetized dogs using a K+-selective surface multielectrode. The regional myocardial blood flow was determined with 9 micron radioactive tracer microspheres. After application of gallopamil (bolus 25 micrograms/kg and infusion 2.5 micrograms/kg.min for 30 min) the maximal and mean rate of rise of [K+]e as well as the plateau of [K+]e reached during ischemia were significantly diminished compared with the control occlusions. 90 min after gallopamil, the rate of rise of [K+]e as well as the plateau of [K+]e reached were still significantly reduced, but 180 min after the gallopamil application, no significant differences between the time course of [K+]e and that of the two control occlusions could be found. Gallopamil significantly elevated myocardial blood flow in the non-ischemic area, but did not influence blood flow in the ischemic region. While collateral perfusion remains unchanged, the slowed and reduced increase of myocardial [K+]e during acute coronary artery occlusion may be an important component of the antiarrhythmic effect of gallopamil during early ischemia.
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Campistron G, Rostin M, Coulais Y, Caillard C, Zarrouk G, Frances J, Thiercellin JF, Montastruc JL, Houin G. Effect of size and dosage strength on the bioavailability of two diltiazem formulations during repeated administrations in humans. Fundam Clin Pharmacol 1987; 1:67-75. [PMID: 3666663 DOI: 10.1111/j.1472-8206.1987.tb00546.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In angina pectoris, diltiazem is usually prescribed as two 60 mg tablets in the morning and two 60 mg tablets in the evening. In the course of the pharmaceutical development of this drug, it was therefore planned to study an experimental formulation containing 120 mg of diltiazem. On the basis of dissolution tests in vitro, a bioavailability study was initiated to compare the 120 mg experimental formulation to the standard 60 mg tablet. The study was conducted in 12 healthy volunteers who received the 2 treatments (one 120 mg tablet bid for 7 days versus two 60 mg standard tablets bid for 7 days) according to a cross-over design. Blood and urine samples were analysed by HPLC method with a UV spectrophotometric detection (sensitivity: 5 ng/ml). Analysis of variance did not show any significant difference between the two formulations for the following parameters: maximum plasma levels observed at steady-state, area under the curves and unchanged urinary diltiazem. From these results the extent of absorption of the 120 mg experimental formulation can be considered as bioequivalent to the administration of 2 tablets of the 60 mg commercially available diltiazem formulation. The time to peak, however, was delayed in 75% of the subjects with the 120 mg diltiazem tablet, showing that the surface area of the pharmaceutical preparation is of primary importance for drug dissolution and rate of absorption.
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Affiliation(s)
- G Campistron
- Unité de Pharmacocinétique Clinique, Centre Hospitalier Universitaire Purpan, Toulouse, France
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41
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Blake K, Clusin WT. Effect of diltiazem on ischemic myocardial depolarization and extracellular K+ accumulation. Eur J Pharmacol 1986; 127:261-5. [PMID: 3758182 DOI: 10.1016/0014-2999(86)90372-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Diltiazem retards ischemic arrhythmias and reduces cellular depolarization, as inferred from recordings of T-Q segment depression (delta T-Q). To explore this further, we correlated delta T-Q with the extracellular K+ electrode potential (delta EK) during serial ischemic trials. delta T-Q and delta EK were uniform in control trials, but decreased markedly in trials that immediately followed diltiazem infusion (0.5 mg/kg). delta EK at 2 min of ischemia was reduced from 11.8 +/- 1.3 to 7.4 +/- 1.2 mV; while delta T-Q was reduced from 7.2 +/- 0.5 to 4.4 +/- 0.7 mV. The effect of diltiazem on ischemic depolarization is largely, but not entirely explained by reduction of delta EK.
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42
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Kendall MJ, Okopski JV. Calcium antagonism--with special reference to diltiazem. JOURNAL OF CLINICAL AND HOSPITAL PHARMACY 1986; 11:159-74. [PMID: 3528227 DOI: 10.1111/j.1365-2710.1986.tb00841.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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43
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Raeder EA, Verrier RL, Lown B. Protective effect of tiapamil against ventricular fibrillation during coronary artery occlusion. Am Heart J 1986; 111:878-82. [PMID: 3706107 DOI: 10.1016/0002-8703(86)90637-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Calcium channel antagonists differ in their effects on myocardial excitable properties. This study examines whether tiapamil (100 micrograms/kg/min intravenously) is capable of reducing the susceptibility to ventricular fibrillation (VF) during acute occlusion and reperfusion of the left anterior descending coronary artery. During occlusion, tiapamil elevated the VF threshold to 17.5 +/- 8.2 mA compared to a control of 8.6 +/- 5.9 mA (2p less than 0.01). However, no significant effect was noted upon reperfusion of the vessel. Adrenergic stimulation with norepinephrine, 0.5 microgram/kg/min, lowered the VF threshold by 32% (2p less than 0.02), and by 6% (N.S.) when tiapamil was infused concurrently. Thus, tiapamil protects the heart against VF during coronary occlusion, but not during reperfusion. This appears to be mediated in part by an antiadrenergic action of the drug.
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Botting JH, Curtis MJ, Walker MJ. Arrhythmias associated with myocardial ischaemia and infarction. Mol Aspects Med 1985; 8:307-422. [PMID: 3916014 DOI: 10.1016/0098-2997(85)90014-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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