1
|
Overdrive pacing of spiral waves in a model of human ventricular tissue. Sci Rep 2020; 10:20632. [PMID: 33244010 PMCID: PMC7691998 DOI: 10.1038/s41598-020-77314-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Accepted: 10/30/2020] [Indexed: 01/03/2023] Open
Abstract
High-voltage electrical defibrillation remains the only reliable method of quickly controlling life-threatening cardiac arrhythmias. This paper is devoted to studying an alternative approach, low-voltage cardioversion (LVC), which is based on ideas from non-linear dynamics and aims to remove sources of cardiac arrhythmias by applying high-frequency stimulation to cardiac tissue. We perform a detailed in-silico study of the elimination of arrhythmias caused by rotating spiral waves in a TP06 model of human cardiac tissue. We consider three parameter sets with slopes of the APD restitution curve of 0.7, 1.1 and 1.4, and we study LVC at the baseline and under the blocking of INa and ICaL and under the application of the drugs verapamil and amiodarone. We show that pacing can remove spiral waves; however, its efficiency can be substantially reduced by dynamic instabilities. We classify these instabilities and show that the blocking of INa and the application of amiodarone increase the efficiency of the method, while the blocking of ICaL and the application of verapamil decrease the efficiency. We discuss the mechanisms and the possible clinical applications resulting from our study.
Collapse
|
2
|
Nguyen TP, Sovari AA, Pezhouman A, Iyer S, Cao H, Ko CY, Bapat A, Vahdani N, Ghanim M, Fishbein MC, Karagueuzian HS. Increased susceptibility of spontaneously hypertensive rats to ventricular tachyarrhythmias in early hypertension. J Physiol 2016; 594:1689-707. [PMID: 26775607 DOI: 10.1113/jp271318] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 12/07/2015] [Indexed: 01/19/2023] Open
Abstract
Hypertension is a risk factor for sudden cardiac death caused by ventricular tachycardia and fibrillation (VT/VF). We hypothesized that, in early hypertension, the susceptibility to stress-induced VT/VF increases. We compared the susceptibility of 5- to 6-month-old male spontaneously hypertensive rats (SHR) and age/sex-matched normotensive rats (NR) to VT/VF during challenge with oxidative stress (H2 O2 ; 0.15 mmol l(-1) ). We found that only SHR hearts exhibited left ventricular fibrosis and hypertrophy. H2 O2 promoted VT in all 30 SHR but none of the NR hearts. In 33% of SHR cases, focal VT degenerated to VF within 3 s. Simultaneous voltage-calcium optical mapping of Langendorff-perfused SHR hearts revealed that H2 O2 -induced VT/VF arose spontaneously from focal activations at the base and mid left ventricular epicardium. Microelectrode recording of SHR hearts showed that VT was initiated by early afterdepolarization (EAD)-mediated triggered activity. However, despite the increased susceptibility of SHR hearts to VT/VF, patch clamped isolated SHR ventricular myocytes developed EADs and triggered activity to the same extent as NR ventricular myocytes, except with larger EAD amplitude. During the early stages of hypertension, when challenged with oxidative stress, SHR hearts showed an increased ventricular arrhythmogenicity that stems primarily from tissue remodelling (hypertrophy, fibrosis) rather than cellular electrophysiological changes. Our findings highlight the need for early hypertension treatment to minimize myocardial fibrosis, ventricular hypertrophy, and arrhythmias.
Collapse
Affiliation(s)
- Thao P Nguyen
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine
| | - Ali A Sovari
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine.,Present address: Department of Medicine, Cedars-Sinai Medical Centre, Los Angeles, CA, USA
| | - Arash Pezhouman
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine
| | - Shankar Iyer
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine
| | - Hong Cao
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine.,Present address: Department of Physiology, Wuhan University, Wuhan, China
| | - Christopher Y Ko
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine
| | - Aneesh Bapat
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine.,Present address: Department of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Nooshin Vahdani
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine.,Present address: School of Pharmacy, West Coast University, Los Angeles, CA, USA
| | - Mostafa Ghanim
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine
| | - Michael C Fishbein
- Department of Pathology, UCLA David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Hrayr S Karagueuzian
- UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine
| |
Collapse
|
3
|
Myles RC, Wang L, Bers DM, Ripplinger CM. Decreased inward rectifying K+ current and increased ryanodine receptor sensitivity synergistically contribute to sustained focal arrhythmia in the intact rabbit heart. J Physiol 2014; 593:1479-93. [PMID: 25772297 DOI: 10.1113/jphysiol.2014.279638] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/27/2014] [Accepted: 08/30/2014] [Indexed: 01/18/2023] Open
Abstract
KEY POINTS Heart failure leads to dramatic electrophysiological remodelling as a result of numerous cellular and tissue-level changes. Important cellular changes include increased sensitivity of ryanodine receptors (RyRs) to Ca(2+) release and down-regulation of the inward rectifying K(+) current (IK1), both of which contribute to triggered action potentials in isolated cells. We studied the role of increased RyR sensitivity and decreased IK1 in contributing to focal arrhythmia in the intact non-failing rabbit heart using optical mapping and pharmacological manipulation of RyRs and IK1. Neither increased RyR sensitivity or decreased IK1 alone led to significant increases in arrhythmia following local sympathetic stimulation; however, in combination, these two factors led to a significant increase in premature ventricular complexes and focal ventricular tachycardia. These results suggest synergism between increased RyR sensitivity and decreased IK1 in contributing to focal arrhythmia in the intact heart and may provide important insights into novel anti-arrhythmic treatments in heart failure. ABSTRACT Heart failure (HF) results in dramatic electrophysiological remodelling, including increased sensitivity of ryanodine receptors (RyRs) and decreased inward rectifying K(+) current (IK1), which predisposes HF myocytes to delayed afterdepolarizations and triggered activity. Therefore, we sought to determine the role of increased RyR sensitivity and decreased IK1 in contributing to focal arrhythmia in the intact non-failing heart. Optical mapping of transmembrane potential and intracellular Ca(2+) was performed in Langendorff-perfused rabbit hearts (n = 15). Local β-adrenergic receptor stimulation with noradrenaline (norepinephrine; NA, 50 μl, 250 μM) was applied to elicit focal activity (premature ventricular complexes (PVCs) or ventricular tachycardia (VT ≥ 3 beats)). NA was administered under control conditions (CTL) and following pretreatment with 50 μM BaCl2 to reduce IK1, or 200 μM caffeine (Caff) to sensitize RyRs, both alone and in combination. Local NA injection resulted in Ca(2+)-driven PVCs arising from the injection site in all hearts studied. No increase in NA-mediated PVCs was observed following pretreatment with either BaCl2 or Caff alone (CTL: 1.1 ± 0.7, BaCl2: 1.0 ± 0.7, Caff: 1.3 ± 0.8 PVCs/injection, P not significant). However, pretreatment with the combination of BaCl2 + Caff resulted in a significant increase in PVCs (2.3 ± 2.8 PVCs/injection, P < 0.05 vs. CTL, BaCl2, Caff). Additionally, pretreatment with BaCl2 + Caff led to sustained monomorphic VT arising from the NA application site in all hearts studied, which lasted up to 6 min following a single NA injection. VT was never observed under any other condition suggesting synergism between increased RyR sensitivity and decreased IK1 in contributing to focal activity. These findings may have important implications for the understanding and prevention of focal arrhythmia in HF.
Collapse
Affiliation(s)
- Rachel C Myles
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
| | | | | | | |
Collapse
|
4
|
Miura M, Hattori T, Murai N, Nagano T, Nishio T, Boyden PA, Shindoh C. Regional increase in extracellular potassium can be arrhythmogenic due to nonuniform muscle contraction in rat ventricular muscle. Am J Physiol Heart Circ Physiol 2012; 302:H2301-9. [PMID: 22447939 DOI: 10.1152/ajpheart.01161.2011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In the ischemic myocardium, extracellular potassium ([K(+)](o)) increases to ≥20 mmol/l. To determine how lethal arrhythmias occur during ischemia, we investigated whether the increased spatial pattern of [K(+)](o), i.e., a regional or a global increase, affects the incidence of arrhythmias. Force, sarcomere length, membrane potential, and nonuniform intracellular Ca(2+) ([Ca(2+)](i)) were measured in rat ventricular trabeculae. A "regional" or "global" increase in [K(+)](o) was produced by exposing a restricted region of muscle to a jet of 30 mmol/l KCl or by superfusing trabeculae with a solution containing 30 mmol/l KCl, respectively. The increase in [Ca(2+)](i) (Ca(CW)) during Ca(2+) waves was measured (24°C, 3.0 mmol/l [Ca(2+)](o)). A regional increase in [K(+)](o) caused nonuniform [Ca(2+)](i) and contraction. In the presence of isoproterenol, the regional increase in [K(+)](o) induced sustained arrhythmias in 10 of 14 trabeculae, whereas the global increase did not induce such arrhythmias. During sustained arrhythmias, Ca(2+) surged within the jet-exposed region. In the absence of isoproterenol, the regional increase in [K(+)](o) increased Ca(CW), whereas the global increase decreased it. This increase in Ca(CW) with the regional increase in [K(+)](o) was not suppressed by 100 μmol/l streptomycin, whereas it was suppressed by 1) a combination of 10 μmol/l cilnidipine and 3 μmol/l SEA0400; 2) 20 mmol/l 2,3-butanedione monoxime; and 3) 10 μmol/l blebbistatin. A regional but not a global increase in [K(+)](o) induces sustained arrhythmias, probably due to nonuniform excitation-contraction coupling. The same mechanism may underlie arrhythmias during ischemia.
Collapse
Affiliation(s)
- Masahito Miura
- Department of Clinical Physiology, Health Science, Tohoku University Graduate School of Medicine, Sendai, Japan.
| | | | | | | | | | | | | |
Collapse
|
5
|
Miura M, Nishio T, Hattori T, Murai N, Stuyvers BD, Shindoh C, Boyden PA. Effect of nonuniform muscle contraction on sustainability and frequency of triggered arrhythmias in rat cardiac muscle. Circulation 2010; 121:2711-7. [PMID: 20547931 DOI: 10.1161/circulationaha.109.907717] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Arrhythmias are benign or lethal, depending on their sustainability and frequency. To determine why lethal arrhythmias are prone to occur in diseased hearts, usually characterized by nonuniform muscle contraction, we investigated the effect of nonuniformity on sustainability and frequency of triggered arrhythmias. METHODS AND RESULTS Force, membrane potential, and intracellular Ca(2+) concentration ([Ca(2+)](i)) were measured in 51 rat ventricular trabeculae. Nonuniform contraction was produced by exposing a restricted region of muscle to a jet of 20 mmol/L 2,3-butanedione monoxime (BDM) or 20 mumol/L blebbistatin. Sustained arrhythmias (>10 seconds) could be induced by stimulus trains for 7.5 seconds only with the BDM or blebbistatin jet (100 nmol/L isoproterenol, 1.0 mmol/L [Ca(2+)](o), 24 degrees C). During sustained arrhythmias, Ca(2+) surges preceded synchronous increases in [Ca(2+)](i), whereas the stoppage of the BDM jet made the Ca(2+) surges unclear and arrested sustained arrhythmias (n=6). With 200 nmol/L isoproterenol, 2.5 mmol/L [Ca(2+)](o), and the BDM jet, lengthening or shortening of the muscle during sustained arrhythmias accelerated or decelerated their cycle in both the absence (n=10) and presence (n=10) of 100 mumol/L streptomycin, a stretch-activated channel blocker, respectively. The maximum rate of force relaxation correlated inversely with the change in cycle lengths (n=14; P<0.01). Sustained arrhythmias with the BDM jet were significantly accelerated by 30 mumol/L SCH00013, a Ca(2+) sensitizer of myofilaments (n=10). CONCLUSIONS These results suggest that nonuniformity of muscle contraction is an important determinant of the sustainability and frequency of triggered arrhythmias caused by the surge of Ca(2+) dissociated from myofilaments in cardiac muscle.
Collapse
Affiliation(s)
- Masahito Miura
- Department of Clinical Physiology, Health Science, Tohoku University Graduate School of Medicine, Sendai, Japan.
| | | | | | | | | | | | | |
Collapse
|
6
|
Gopinathannair R, Chaudhary AK, Xing D, Ely D, Zheng W, Martins JB. Angiotensin II effects on ischemic focal ventricular tachycardia are predominantly mediated through myocardial AT(2) receptor. Am J Physiol Heart Circ Physiol 2009; 297:H1889-98. [PMID: 19783782 DOI: 10.1152/ajpheart.00080.2009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ischemic focal ventricular tachycardia (VT) occurs in animals and humans. Angiotensin-converting enzyme inhibitors and receptor blockers reduce sudden death in patients with ischemic heart disease. In our dog model of coronary artery occlusion (CAO), we tested the hypothesis that angiotensin II (AGII) will selectively promote focal VT and that the specific AT(2) blocker PD-123319 (PD), or AT(1) blocker losartan, will affect this VT. Anesthetized dogs (n = 90) underwent CAO, followed by three-dimensional activation mapping of inducible VT. Dogs without VT in 1-3 h after CAO received AGII, and those with VT received either PD or losartan. Focal endocardium excised from ischemic sites was studied in vitro with standard microelectrode. Of 33 dogs with no inducible VT, AGII infusion resulted in sustained VT of only focal Purkinje origin in 13 (39%) compared with 0 of 20 dogs with saline. Of 26 dogs with inducible VT at baseline, given PD, reinduction was blocked in 8 of 10 (P < 0.05) focal VT, but only 1 of 15 with reentry. In contrast, of 11 dogs given losartan, reinduction of either mechanism was not blocked. In vitro triggered activity in Purkinje was blocked by PD in 13 of 19 (P < 0.05), but not by losartan in 8. Also, triggered activity was promoted by AGII, losartan, or the combination in 9 of 12 tissues. AGII promotes only focal, mainly Purkinje ischemic VT. PD, but not losartan, preferentially blocked focal VT, which is likely due to triggered activity due to delayed afterdepolarizations in Purkinje.
Collapse
Affiliation(s)
- Rakesh Gopinathannair
- Department of Internal Medicine, University of Iowa College of Medicine and the Veterans Affairs Medical Center, University of Iowa, Iowa City, Iowa, USA
| | | | | | | | | | | |
Collapse
|