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Van de Heyning CM, Moerenhout CM, Vrints CJ. Case report: Chest pain, intermittent left bundle branch block and negative T waves. Int J Cardiol 2011; 147:302-4. [PMID: 21215481 DOI: 10.1016/j.ijcard.2010.12.059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 12/09/2010] [Indexed: 10/18/2022]
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Madias JE. Is the different frequency of T-wave inversion in arrhythmogenic right ventricular cardiomyopathy and idiopathic ventricular tachycardia due to different frequency and duration of ventricular ectopy inducing a different degree of cardiac memory effect? Am J Cardiol 2010; 106:1522. [PMID: 21059451 DOI: 10.1016/j.amjcard.2010.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 08/13/2010] [Indexed: 11/26/2022]
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103
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Padeletti L, Fantappiè C, Perrotta L, Ricciardi G, Pieragnoli P, Chiostri M, Valsecchi S, Porciani MC, Michelucci A, Fantini F. Cardiac memory in humans: vectocardiographic quantification in cardiac resynchronization therapy. Clin Res Cardiol 2010; 100:51-6. [DOI: 10.1007/s00392-010-0209-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Accepted: 08/19/2010] [Indexed: 11/24/2022]
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104
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Shvilkin A, Bojovic B, Vajdic B, Gussak I, Ho KK, Zimetbaum P, Josephson ME. Vectorcardiographic and electrocardiographic criteria to distinguish new and old left bundle branch block. Heart Rhythm 2010; 7:1085-92. [DOI: 10.1016/j.hrthm.2010.05.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Accepted: 05/15/2010] [Indexed: 10/19/2022]
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105
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Byrne R, Filippone L. Benign persistent T-wave inversion mimicking ischemia after left bundle-branch block—cardiac memory. Am J Emerg Med 2010; 28:747.e5-6. [DOI: 10.1016/j.ajem.2009.10.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 10/13/2009] [Indexed: 11/27/2022] Open
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Yue-Chun L, Li-Sha G, Xue-Qiang G, Peng C, Lian-Pin W, Peng-Lin Y, Ji-Fei T, Jia-Feng L. Establishment of a canine model of cardiac memory using endocardial pacing via internal jugular vein. BMC Cardiovasc Disord 2010; 10:30. [PMID: 20569432 PMCID: PMC2906410 DOI: 10.1186/1471-2261-10-30] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2010] [Accepted: 06/22/2010] [Indexed: 11/20/2022] Open
Abstract
Background Development of experimental animal models has played an important role in understanding the mechanisms of cardiac memory. The purpose of this study was to evaluate a new canine model of cardiac memory using endocardial ventricular pacing via internal jugular vein. Methods Twelve Beagle dogs underwent placement of a permanent ventricular pacemaker mimicking the use of pacemakers in humans and induction of cardiac memory by endocardial ventricular pacing. Results Cardiac memory was achieved in 11 of 12 attempts overall. Procedural mortality due to cardiac tamponade (n = 1) occurred in the first attempt. The T-wave memory persisted for 96 ± 17 minutes and 31 ± 6 days in the short-term and long-term cardiac memory groups, respectively. There were no significant differences in the heart rate, blood pressure and echocardiographic parameters in the animals between before and after ventricular pacing in the short-term and long-term cardiac memory groups. No significant pathologic changes with the light microscopy were found in the present study in all dogs. Conclusion The model does require surgery but is not as invasive as an open-chest model. This canine model can serve as a useful tool for studying mechanisms of cardiac memory.
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Affiliation(s)
- Li Yue-Chun
- Department of Cardiology, Second Affiliated Hospital of Wenzhou Medical College, Wenzhou, Zhejiang 325000, China.
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Bierhuizen MFA, Vos MA. The molecular labyrinth of electrical remodeling: making sense of cardiac memory. Heart Rhythm 2010; 7:971-2. [PMID: 20382268 DOI: 10.1016/j.hrthm.2010.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Indexed: 12/28/2022]
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Abstract
Cardiac arrhythmias are a major cause of death and disability. Despite the clinical need and the importance of studying arrhythmia mechanisms in humans, a noninvasive imaging modality for cardiac electrophysiology is not yet available for routine application. Here we describe such a noninvasive imaging modality, electrocardiographic imaging (ECGI), and provide examples of its application in various (normal and abnormal) cardiac rhythms.
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Affiliation(s)
- Yoram Rudy
- Cardiac Bioelectricity and Arrhythmia Center, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
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Ozgen N, Lau DH, Shlapakova IN, Sherman W, Feinmark SJ, Danilo P, Rosen MR. Determinants of CREB degradation and KChIP2 gene transcription in cardiac memory. Heart Rhythm 2010; 7:964-70. [PMID: 20346417 DOI: 10.1016/j.hrthm.2010.03.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Accepted: 03/19/2010] [Indexed: 01/12/2023]
Abstract
BACKGROUND Left ventricular pacing (LVP) to induce cardiac memory (CM) in dogs results in a decreased transient outward K current (I(to)) and reduced mRNA and protein of the I(to) channel accessory subunit, KChIP2. The KChIP2 decrease is attributed to a decrease in its transcription factor, cyclic adenosine monophosphate response element binding protein (CREB). OBJECTIVE This study sought to determine the mechanisms responsible for the CREB decrease that is initiated by LVP. METHODS CM was quantified as T-wave vector displacement in 18 LVP dogs. In 5 dogs, angiotensin II receptor blocker, saralasin, was infused before and during pacing. In 3 dogs, proteasomal inhibitor, lactacystin, was injected into the left anterior descending artery before LVP. Epicardial biopsy samples were taken before and after LVP. Neonatal rat cardiomyocytes (NRCM) were incubated with H(2)O(2) (50 micromol/l) for 1 hour with or without lactacystin. RESULTS LVP significantly displaced the T-wave vector and was associated with increased lipid peroxidation and increased tissue angiotensin II levels. Saralasin prevented T-vector displacement and lipid peroxidation. CREB was significantly decreased after 2 hours of LVP and was comparably decreased in H(2)O(2)-treated NRCM. Lactacystin inhibited the CREB decrease in LVP dogs and H(2)O(2)-treated NRCM. LVP and H(2)O(2) both induced CREB ubiquitination, and the H(2)O(2)-induced CREB decrease was prevented by knocking down ubiquitin. CONCLUSION LVP initiates myocardial angiotensin II production and reactive oxygen species synthesis, leading to CREB ubiquitination and its proteasomal degradation. This sequence of events would explain the pacing-induced reduction in KChIP2, and contribute to altered repolarization and the T-wave changes of cardiac memory.
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Affiliation(s)
- Nazira Ozgen
- Department of Pharmacology, Columbia University, New York, New York 10032, USA.
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Chiale PA, Pastori JD, Garro HA, Faivelis L, Ianovsky O, Sánchez RA, Alvarez CB, González MD, Elizari MV. Reversal of primary and pseudo-primary T wave abnormalities by ventricular pacing. A novel manifestation of cardiac memory. J Interv Card Electrophysiol 2010; 28:23-33. [PMID: 20333458 DOI: 10.1007/s10840-010-9473-9] [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] [Received: 11/30/2009] [Accepted: 01/27/2010] [Indexed: 10/19/2022]
Abstract
AIMS "Cardiac memory" refers to abnormal T waves (TW) appearing after transient periods of altered ventricular depolarization. The aim of the study was to test the hypothesis that in the presence of abnormal TW, short periods of tailored ventricular pacing (VP) can be followed by normalization of ventricular repolarization. METHODS Ten patients with normal TW (control group) and 18 patients with abnormal TW (study group) underwent 15 min of VP at a cycle length of 500 ms. In the control group, VP was performed from the right ventricular apex, and in the study group from right or left ventricular sites that resulted in paced QRS complexes of opposite polarity to that of the abnormal TW. Before and after VP, atrial pacing was maintained at a stable cycle length. Simultaneous 12-lead electrocardiography (ECG) was recorded before, during, and following VP to assess changes in TW polarity, amplitude, electrical axis, QTc interval, and QTc interval dispersion. RESULTS As expected, VP was followed by memory-induced changes in TW in eight of ten patients in the control group. Mean T wave axis shifted from +60 degrees + or - 21.2 degrees to +23.5 degrees + or - 50.7 degrees (p = 0.01) in the frontal plane. In the study group, complete or partial normalization of TW occurred in 17 of 18 patients. Mean T wave axis shifted from -23.7 degrees + or - 22.9 degrees to +19.7 degrees + or - 34.7 degrees (p < 0.0002) in the frontal plane when paced from right ventricular outflow tract. The QTc interval shortened after VP both in the control group (424 + or - 25 vs. 399 + or - 27 ms; p = 0.007) and in the study group (446 + or - 26 vs. 421 + or - 22 ms; p < 0.0002). No significant changes were found in QTc interval dispersion. CONCLUSIONS Transient changes in the sequence of ventricular activation may either induce or normalize abnormal TW. The background of preceding ventricular depolarization needs to be taken into account before determining the clinical significance of a given pattern of ventricular repolarization.
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Affiliation(s)
- Pablo A Chiale
- Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, Division of Cardiology, Ramos Mejía Hospital, Buenos Aires, Argentina.
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Sachdeva G, Kalyanasundaram K, Krishnan J, Chakravarthy VS. Bistable dynamics of cardiac cell models coupled by dynamic gap junctions linked to cardiac memory. BIOLOGICAL CYBERNETICS 2010; 102:109-121. [PMID: 20012545 DOI: 10.1007/s00422-009-0352-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 11/16/2009] [Indexed: 05/28/2023]
Abstract
In an earlier study, we suggested that adaptive gap junctions (GJs) might be a basis of cardiac memory, a phenomenon which refers to persistent electrophysiological response of the heart to external pacing. Later, it was also shown that the proposed mechanism of adaptation of GJs is consistent with known electrophysiology of GJs. In the present article, we show that a pair of cardiac cell models coupled by dynamic, voltage-sensitive GJs exhibits bistable behavior under certain conditions. Three kinds of cell pairs are considered: (1) a Noble-Noble cell pair that represents adjacent cells in Purkinje network, (2) a pair of DiFranceso-Noble cells that represents adjacent SA nodal cells, and (3) a model of Noble cell coupled to Luo-Rudy cell model, which represents an interacting pair of a Purkinje fiber and a ventricular myocyte. Bistability is demonstrated in all the three cases. We suggest that this bistability might be an underlying factor behind cardiac memory. Focused analysis of a pair of Noble cell models showed that bistability is obtained only when the properties of GJs "match" with the properties of the pair of cells that is coupled by the GJs. This novel notion of match between GJs and cardiac cell types might give an insight into specialized distributions of various connexin proteins in cardiac tissue.
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Affiliation(s)
- Gairik Sachdeva
- Department of Biotechnology, Indian Institute of Technology, Chennai, India
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Abstract
The following article is a personal reflection on my study of a subject which has long interested me. The subject is the T wave, and especially the T wave changes occurring as a marker of cardiac memory. My interest evolved over coffees that Mauricio Rosenbaum and I used to share at the Hotel Algonquin during his frequent trips from Buenos Aires to New York. There is something about the Algonquin, whose scarred wooden tabletops carry the imprints of Robert Benchley, Dorothy Parker, and the 1920's New York literati, and there was something about Mauricio-clinician-scientist, friend, and raconteur extraordinaire-that made his repeated challenges to me to "look at cardiac memory before you begin losing your own" irresistible. So began my personal voyage into trying to understand the T wave. My guideposts were the experiments of Wilson and Finch,(1) the astute observations of a host of investigators who followed, and Mauricio's iconoclastic insights. The story is far from over...I doubt I'll see the end of it in my lifetime. But if the beauty of discovery is in the voyage, then it has been - for me - a memorable trip.
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Affiliation(s)
- Michael R Rosen
- Department of Pharmacology, Center for Molecular Therapeutics, and Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
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Jeyaraj D, Ashwath M, Rosenbaum DS. Pathophysiology and clinical implications of cardiac memory. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2009; 33:346-52. [PMID: 20025710 DOI: 10.1111/j.1540-8159.2009.02630.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Altering the pattern of activation of the ventricle causes remodeling of the mechanical and electrical properties of the myocardium. The electrical remodeling is evident on the surface electrocardiogram as significant change in T-wave polarity following altered activation; this phenomenon is ascribed to as "T-wave memory" or "cardiac memory." The electrophysiological remodeling following altered activation is characterized by distinct changes in regions proximal (early-activated) versus distal (late-activated) to the site of altered activation. The early-activated region exhibits marked attenuation of epicardial phase 1 notch due to reduced expression of the transient outward potassium current (I(to)). This is attributed to electrotonic changes during altered activation, and angiotensin-mediated regulation of Kv4.3 (the pore-forming alpha subunit responsible for I(to)). The late-activated region exhibits the most significant action potential prolongation due to markedly increased mechanical strain through a mechano-electrical feedback mechanism. Consequently, regionally heterogeneous action potential remodeling occurs following altered activation. This enhances regional repolarization gradients that underlie the electrophysiological basis for T-wave memory. Further, recent clinical studies highlight detrimental consequences of altered activation including worsening mechanical function and increased susceptibility to arrhythmias. Future studies to identify molecular mechanisms that link electrotonic and mechanical strain-induced changes to cellular electrophysiology will provide important insights into the role of altered activation in regulating cardiac repolarization and arrhythmogenesis.
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Affiliation(s)
- Darwin Jeyaraj
- Heart and Vascular Research Center, The Department of Biomedical Engineering, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, USA
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115
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Rudy Y. Cardiac repolarization: insights from mathematical modeling and electrocardiographic imaging (ECGI). Heart Rhythm 2009; 6:S49-55. [PMID: 19880074 DOI: 10.1016/j.hrthm.2009.07.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Indexed: 11/16/2022]
Abstract
Cardiac repolarization is a complex rate dependent process. At the cellular level, it depends on a delicate dynamic balance of ion channel currents. At the heart level, it is spatially heterogeneous, leading to spatial gradients of potential and excitability. This article provides insights into the molecular mechanisms of the delayed rectifiers I(Kr) (rapid) and I(Ks) (slow) that underlie effective function of these channels as repolarizing currents during the cardiac action potential (AP). We also provide noninvasive images of cardiac repolarization in humans. Methodologically, computational biology is used to simulate ion channel function and to incorporate it into a model of the cardiac cell. ECG imaging (ECGI) is applied to normal subjects and Wolff-Parkinson-White (WPW) patients to obtain epicardial maps of repolarization. The simulations demonstrate that I(Kr) and I(Ks) generate their peak current late during the AP, where they effectively participate in repolarization. I(Kr) maximizes the current by fast inactivation and gradual recovery during the AP. I(Ks) does so by generating an available reserve of channels in closed states from which the channels can open rapidly. ECGI shows that in the human heart, normal repolarization epicardial potential maps are static with 40 ms dispersion between RV and LV. In WPW, ECGI located the accessory pathway(s) and showed a large base-to-apex repolarization gradient that resolved to normal one month post-ablation, demonstrating presence of "cardiac memory". We conclude that computational biology can provide a mechanistic link across scales, from the molecular functioning of ion channels to the cellular AP. ECGI can noninvasively image human cardiac repolarization and its alteration by disease and interventions. This property makes it a potential tool for noninvasive risk stratification and evaluation of treatment by drugs and devices.
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Affiliation(s)
- Yoram Rudy
- Cardiac Bioelectricity and Arrhythmia Center, Washington University in St. Louis, St. Louis, Missouri 63130-4899, USA.
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[Cardiac memory of the ECG following ventricular pacing]. Herz 2009; 34:324-6. [PMID: 19575164 DOI: 10.1007/s00059-009-3188-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Accepted: 03/18/2009] [Indexed: 10/18/2022]
Abstract
During abnormal pacemaker depolarization, abnormal repolarization occurs and persists in normal QRS beats often seen in alternation with paced beats. The T-wave direction of normal beats is typically similar to the direction of the QRS complex during pacing, hence the term cardiac memory. The normal nonpaced beats have shown a sensitivity of 92% and a specificity of 100% for cardiac memory in the presence of T-wave inversions (TWI) in the precordial and inferior (II, III and aVF) leads with a positive T wave in aVL, a positive or isoelectric T wave in lead I, and the maximal precordial TWI being greater than the TWI of lead III, discriminating it from ischemic precordial TWI. In the latter, TWI are also seen in leads aVL and I.
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Kooshkabadi M, Whalen P, Yoo D, Langberg J. Stretch-activated receptors mediate cardiac memory. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2009; 32:330-5. [PMID: 19272062 DOI: 10.1111/j.1540-8159.2008.02240.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Cardiac memory refers to long-lasting T-wave changes that follow an episode of altered ventricular activation sequence. Memory-induced alterations in repolarizing ion channel activity have been characterized. However, the mechanism by which changes in activation sequence produce these effects is unknown. We hypothesized that cardiac memory is mediated by the response of stretch-activated receptors (SARs) to a change in mechanical activation sequence. METHODS In anesthetized, closed-chest dogs, coronary sinus leads were used to pace the posterolateral left ventricle (LV) continuously for 1 hour at a rate of 120 bpm. The surface vectorcardiogram was used to quantify cardiac memory by measuring T-wave displacement after pacing. Streptomycin, which has been shown to block SARs, was given at a dose of 4 g intramuscularly 1 hour before experimental LV pacing sessions. T-wave displacement after control sessions of LV pacing in the absence of drug (n = 12) was compared to that produced by pacing after streptomycin administration (n = 10 sessions). RESULTS There was a distinct and consistent cardiac memory seen after 1 hour of LV pacing under control conditions, with T-wave displacement of 1.28 +/- 0.43 mV (P < 0.001 vs baseline). Pretreatment with streptomycin had no direct effect on the electrocardiogram or hemodynamics, but decreased pacing-induced T-wave displacement to 0.50 +/- 0.28 mV (P < 0.001 vs control sessions). CONCLUSIONS Streptomycin, a SAR blocker, dramatically attenuated the development of cardiac memory following epicardial pacing. These data suggest that SARs are a critical link between mechanical sequence of activation and regional modulation of action potential duration that is responsible for cardiac memory.
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Affiliation(s)
- Mohammad Kooshkabadi
- Section of Cardiac Electrophysiology, Emory University, 1342 Clifton Road, Atlanta, GA 30322, USA.
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118
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Rautaharju PM, Surawicz B, Gettes LS, Bailey JJ, Childers R, Deal BJ, Gorgels A, Hancock EW, Josephson M, Kligfield P, Kors JA, Macfarlane P, Mason JW, Mirvis DM, Okin P, Pahlm O, van Herpen G, Wagner GS, Wellens H. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part IV: the ST segment, T and U waves, and the QT interval: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society. Endorsed by the International Society for Computerized Electrocardiology. J Am Coll Cardiol 2009; 53:982-91. [PMID: 19281931 DOI: 10.1016/j.jacc.2008.12.014] [Citation(s) in RCA: 577] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Shvilkin A, Bojovic B, Vajdic B, Gussak I, Zimetbaum P, Josephson ME. Vectorcardiographic determinants of cardiac memory during normal ventricular activation and continuous ventricular pacing. Heart Rhythm 2009; 6:943-8. [PMID: 19560083 DOI: 10.1016/j.hrthm.2009.03.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2009] [Accepted: 03/13/2009] [Indexed: 11/24/2022]
Abstract
BACKGROUND Cardiac memory (CM) refers to persistent T-wave changes on resumption of normal conduction after a period of abnormal ventricular activation. Traditionally, to observe CM, normal ventricular activation had to be restored, limiting the exploration of this phenomenon in clinical practice. OBJECTIVE This study sought to prove that CM can be detected during continuous aberrant activation and to establish factors affecting its magnitude using a vectorcardiographic technique. METHODS Sixteen nonpacemaker-dependent patients (11 male, age 72 +/- 8 years, mean +/- SD) undergoing pacemaker/internal cardioverter-defibrillator implantation were paced in DDD mode with a short atrioventricular (AV) delay for 7 days to induce CM. Electrocardiograms were acquired during AAI and DDD pacing at a constant rate before and after CM induction. Dower transform-derived vectorcardiograms were reconstructed and analyzed. RESULTS T vector during AAI pacing changed in both magnitude (baseline, 0.26 +/- 0.10 mV; Day 7, 0.39 +/- 0.13 mV, P < .01) and direction aligning with the paced QRS vector (baseline DDD QRS - AAI T angle 125 degrees +/- 36 degrees; Day 7, 39 degrees +/- 21 degrees, P < .01). During DDD pacing, there was no change in T-vector direction, but T amplitude decreased (baseline, 1.06 +/- 0.32 mV; Day 7, 0.71 +/- 0.26 mV, P < .01). CM measured as T-vector peak displacement (TPD) was identical in AAI and DDD mode (TPD 0.46 +/- .0.17 mV and 0.46 +/- 0.17 mV, respectively). Individual CM magnitude correlated with QRS/T-vector amplitude ratio during DDD pacing at baseline (r = 0.90). CONCLUSION CM can be reliably shown during continuous ventricular pacing, expanding its application to situations in which abnormal ventricular activation persists. Its magnitude is determined by the QRS/T-amplitude ratio of the ventricular paced beat.
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Affiliation(s)
- Alexei Shvilkin
- Department of Medicine/Division of Cardiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.
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Eisner DA, Dibb KM, Trafford AW. The mechanism and significance of the slow changes of ventricular action potential duration following a change of heart rate. Exp Physiol 2009; 94:520-8. [PMID: 19270038 DOI: 10.1113/expphysiol.2008.044008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This article reviews the effects of changes of heart rate on the ventricular action potential duration. These can be divided into short term (fractions of a second), resulting from the kinetics of recovery of membrane currents, through to long term (up to days), resulting from changes of protein expression. We concentrate on the medium-term changes (time course of the order of 100 s). These medium-term changes occur in isolated tissues and in the intact human heart. They may protect against cardiac arrhythmias. Finally, we discuss the cellular mechanisms responsible for these changes.
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Affiliation(s)
- D A Eisner
- University of Manchester, Unit of Cardiac Physiology, 3.18 Core Technology Facility, Manchester, UK.
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121
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Rautaharju PM, Surawicz B, Gettes LS, Bailey JJ, Childers R, Deal BJ, Gorgels A, Hancock EW, Josephson M, Kligfield P, Kors JA, Macfarlane P, Mason JW, Mirvis DM, Okin P, Pahlm O, van Herpen G, Wagner GS, Wellens H. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part IV: the ST segment, T and U waves, and the QT interval: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: endorsed by the International Society for Computerized Electrocardiology. Circulation 2009; 119:e241-50. [PMID: 19228821 DOI: 10.1161/circulationaha.108.191096] [Citation(s) in RCA: 275] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Benchimol D, Mazanof M, Dubroca B, Benchimol H, Bernard V, Couffinhal T, Dartigues JF, Roudaut R, Pillois X, Bonnet J. Detection of coronary stenoses by stress echocardiography using a previously implanted pacemaker for ventricular pacing: preliminary report of a new method. Clin Cardiol 2009; 23:842-8. [PMID: 11097132 PMCID: PMC6655253 DOI: 10.1002/clc.4960231111] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND The number of patients with pacemakers has been increasing and a large number of them will present with chest pain or symptoms suggesting angina pectoris. Myocardial ischemia and presence of coronary artery disease are difficult to detect and assess by noninvasive methods in patients with a pacemaker; the electrocardiogram (ECG) at rest and during exercise is usually very difficult to analyze in terms of ischemia or even presence of an acute myocardial infarction. HYPOTHESIS To detect significant coronary stenosis in patients with previously implanted pacemakers, we tested a new stress echocardiography method using incremental ventricular pacing by already implanted pacemakers. METHODS We studied prospectively 25 consecutive patients who underwent stress echocardiography with increasing ventricular pacing up to either 85% of the age-predicted maximal heart rate or chest pain. Positive tests were defined by new hypokinesia or worsening of a preexisting alteration in wall motion in at least two adjacent territories. All patients underwent coronary angiograms to define the presence and severity of coronary stenoses. RESULTS Among the 25 tests, 11 (44%) were stopped for chest pain. 1 (4%) for moderate discomfort, 1 (4%) for a drop in blood pressure, and the target pacing rate was achieved in the tests of the remaining 12 patients (48%). There were no complications. Thirteen patients had significant stenoses. In 10 cases, stress echocardiography was a true positive test with respect to coronary angiography. There were 11 true negative, 1 false positive, and 3 false negative tests. The sensitivity was 77%, specificity was 90%, the positive predictive value was 91%, and the negative predictive value 79%. The accuracy was 84%. CONCLUSIONS This new stress echocardiography method appears feasible, easy, safe, and effective for detection of significant coronary stenoses in patients with pacemakers.
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Affiliation(s)
- D Benchimol
- Service de Cardiologie et Maladies Vasculaires, Hôpital Cardiologique, Pessac, France
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Lee KT, Chu CS, Cheng KH, Lu YH, Huang CH, Lin TH, Lee MC, Sheu SH, Lai WT. Effect of Short-term Cardiac Memory on Ventricular Electrical Restitution and QT Intervals in Humans. Kaohsiung J Med Sci 2009; 25:53-61. [DOI: 10.1016/s1607-551x(09)70041-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Abstract
Cardiac memory is a form of electrophysiological remodeling generally considered benign, although it shares transduction pathways with factors that may be pathological, such as angiotensin II and reactive oxygen species. When induced by electrical pacing, memory provides a window into the mechanisms engaged during cardiac device therapy. Emphasis is placed on the complexity of signaling processes occurring downstream to the simple intervention of cardiac pacing and the relationship of resultant ion channel changes to their expression in action potentials and body surface recordings.
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Rottensteiner J, Kaneppele A, Stockner I, Ladurner C, Panizza G, Wiedermann CJ. Precordial T-wave inversion of "cardiac memory" pattern after high-dose methylprednisolone pulse therapy. Intern Emerg Med 2008; 3:375-8. [PMID: 18274710 DOI: 10.1007/s11739-008-0121-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Accepted: 11/12/2007] [Indexed: 01/09/2023]
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Thomsen MB, Sosunov EA, Anyukhovsky EP, Ozgen N, Boyden PA, Rosen MR. Deleting the accessory subunit KChIP2 results in loss of I(to,f) and increased I(K,slow) that maintains normal action potential configuration. Heart Rhythm 2008; 6:370-7. [PMID: 19251214 DOI: 10.1016/j.hrthm.2008.11.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 11/21/2008] [Indexed: 10/21/2022]
Abstract
BACKGROUND Four voltage-gated potassium currents, I(to,f) (K(V)4.2), I(to,s) (K(V)1.4), I(K,slow) (K(V)1.5+K(V)2.1), and I(SS) (TASK1), govern murine ventricular repolarization. Although the accessory subunit KChIP2 influences I(to,f) expression, in preliminary experiments we found that action potential duration (APD) is maintained in KChIP2 knockout mice. OBJECTIVE We tested the role of KChIP2 in regulating APD and studied the underlying ionic currents. METHODS We used microelectrode techniques, whole-cell patch clamp studies, and real-time polymerase chain reaction amplification to characterize ventricular repolarization and its determinants in wild-type and KChIP2(-/-) mice. RESULTS Despite comparable baseline action potentials, APD was more markedly prolonged by 4-aminopyridine (4-AP) in KChIP2(-/-) preparations. Peak K(+) current densities were similar in wild-type and KChIP2(-/-) cells (mean +/- SEM I(P): 28.3 +/- 2 (n = 27) vs. 29.2 +/- 2 pA/pF (n = 24), respectively; P > .05). Heteropodatoxin-2 (HpTx-2, 1 microM) had no effect on current amplitude in KChIP2(-/-) myocytes. The current fractions sensitive to 4-AP (50 microM and 1 mM) were larger in KChIP2(-/-) than wild-type (P < .05). Real-time polymerase chain reaction showed absence of KChIP2 and increased K(V)1.5 expression in KChIP2(-/-) ventricular myocardium. CONCLUSION KChIP2 deficiency eliminated HpTx-2-sensitive I(to,f), but had little impact on total APD, secondary to upregulation of 4-AP-sensitive I(K,slow) in association with increased K(V)1.5 expression. There is increased sensitivity to 4-AP-mediated APD prolongation in KChIP2(-/-). Thus, KChIP2 seems important for murine repolarization in circumstances of reduced repolarization reserve.
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Affiliation(s)
- Morten B Thomsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
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Sucu MM, Davutoglu V. Cardiac memory T-wave changes after ventricular tachycardia in pregnancy. Am J Emerg Med 2008; 26:968.e1-3. [PMID: 18926372 DOI: 10.1016/j.ajem.2008.02.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Accepted: 02/10/2008] [Indexed: 11/19/2022] Open
Abstract
A 36-year-old pregnant woman (20 weeks) was admitted to the coronary care unit because of ventricular tachycardia (VT). 12-Lead electrocardiogram showed a monomorphic regular wide QRS tachycardia with a ventricular rate of 220 beats/min and left bundle branch block morphology. Her electrocardiogram after the termination of the tachycardia returned to baseline with the Twave inversions in V1-V6 and DII, DII, aVF. The marked T-wave inversions demonstrate cardiac memory due to the preceding abnormal ventricular activation caused by VT. Because the T-wave inversion happened after the conversion from VT to sinus rhythm, it may be explained by the cardiac memory phenomenon.
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Affiliation(s)
- M Murat Sucu
- Department of Cardiology, Medical Faculty, Gaziantep University, Gaziantep, Turkey
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128
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Pavri BB, Hillis MB, Subacius H, Brumberg GE, Schaechter A, Levine JH, Kadish A. Prognostic value and temporal behavior of the planar QRS-T angle in patients with nonischemic cardiomyopathy. Circulation 2008; 117:3181-6. [PMID: 18574059 DOI: 10.1161/circulationaha.107.733451] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The planar QRS-T angle can be easily obtained from standard 12-lead ECGs, but its predictive ability is not established. We sought to determine the predictive ability of the planar QRS-T angle in patients with nonischemic cardiomyopathy and to assess QRS-T angle behavior over time. METHODS AND RESULTS Baseline QRS-T angles from 455 patients in the Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial were measured. All patients had nonischemic cardiomyopathy, New York Heart Association class I to III heart failure, and nonsustained ventricular tachycardia or frequent ventricular ectopy. The primary end point (a composite of total mortality, appropriate implantable cardioverter-defibrillator shock, or resuscitated cardiac arrest) occurred in 25 of 172 patients (14.5%) with a QRS-T angle < or =90 degrees and in 72 of 283 patients (25.4%) with a QRS-T angle >90 degrees (hazard ratio, 1.93; 95% confidence interval, 1.23 to 3.05; P=0.002). A QRS-T angle >90 degrees remained a significant predictor of the primary end point (P=0.039) after adjustment for treatment group, age, gender, QRS duration, left bundle-branch block, left ventricular ejection fraction, New York Heart Association class III, atrial fibrillation, and diabetes mellitus. The secondary end point (total mortality) occurred in 17 of the 172 patients (9.9%) with a QRS-T angle < or =90 degrees and in 49 of the 283 patients (17.3%) with a QRS-T angle >90 degrees (hazard ratio, 1.79; 95% confidence interval, 1.03 to 3.10; P=0.016). A sample of 152 patients with multiple follow-up ECGs was analyzed to assess temporal QRS-T angle behavior. Changes in the QRS-T angle correlated with changes in left ventricular ejection fraction and QRS duration over time (P<0.001). CONCLUSIONS A planar QRS-T angle >90 degrees is a significant predictor of a composite end point of death, appropriate implantable cardioverter-defibrillator shock, or resuscitated cardiac arrest in nonpaced, mild to moderately symptomatic patients with nonischemic cardiomyopathy with frequent or complex ventricular ectopy. QRS-T angles changed predictably with left ventricular ejection fraction and QRS duration.
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Affiliation(s)
- Behzad B Pavri
- Department of Medicine, Division of Cardiology, Thomas Jefferson University Hospital, 925 Chestnut St, Philadelphia, PA 19107, USA.
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Mechanoelectric Feedback as a Trigger Mechanism for Cardiac Electrical Remodeling: A Model Study. Ann Biomed Eng 2008; 36:1816-35. [DOI: 10.1007/s10439-008-9559-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Accepted: 08/27/2008] [Indexed: 12/20/2022]
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130
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Kontogeorgis A, Li X, Kang EY, Feig JE, Ponzio M, Kang G, Kaba RA, Wit AL, Fisher EA, Morley GE, Peters NS, Coetzee WA, Gutstein DE. Decreased connexin43 expression in the mouse heart potentiates pacing-induced remodeling of repolarizing currents. Am J Physiol Heart Circ Physiol 2008; 295:H1905-16. [PMID: 18757477 PMCID: PMC2614590 DOI: 10.1152/ajpheart.590.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Gap junction redistribution and reduced expression, a phenomenon termed gap junction remodeling (GJR), is often seen in diseased hearts and may predispose toward arrhythmias. We have recently shown that short-term pacing in the mouse is associated with changes in connexin43 (Cx43) expression and localization but not with increased inducibility into sustained arrhythmias. We hypothesized that short-term pacing, if imposed on murine hearts with decreased Cx43 abundance, could serve as a model for evaluating the electrophysiological effects of GJR. We paced wild-type (normal Cx43 abundance) and heterozygous Cx43 knockout (Cx43+/−; 66% mean reduction in Cx43) mice for 6 h at 10–15% above their average sinus rate. We investigated the electrophysiological effects of pacing on the whole animal using programmed electrical stimulation and in isolated ventricular myocytes with patch-clamp studies. Cx43+/− myocytes had significantly shorter action potential durations (APD) and increased steady-state (Iss) and inward rectifier (IK1) potassium currents compared with those of wild-type littermate cells. In Cx43+/− hearts, pacing resulted in a significant prolongation of ventricular effective refractory period and APD and significant diminution of Iss compared with unpaced Cx43+/− hearts. However, these changes were not seen in paced wild-type mice. These data suggest that Cx43 abundance plays a critical role in regulating currents involved in myocardial repolarization and their response to pacing. Our study may aid in understanding how dyssynchronous activation of diseased, Cx43-deficient myocardial tissue can lead to electrophysiological changes, which may contribute to the worsened prognosis often associated with pacing in the failing heart.
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Affiliation(s)
- Andrianos Kontogeorgis
- Leon H. Charney Division of Cardiology, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA
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Ghosh S, Rhee EK, Avari JN, Woodard PK, Rudy Y. Cardiac memory in patients with Wolff-Parkinson-White syndrome: noninvasive imaging of activation and repolarization before and after catheter ablation. Circulation 2008; 118:907-15. [PMID: 18697818 DOI: 10.1161/circulationaha.108.781658] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Cardiac memory refers to a change in ventricular repolarization induced by and persisting for minutes to months after cessation of a period of altered ventricular activation (eg, resulting from pacing or preexcitation in patients with Wolff-Parkinson-White syndrome). ECG imaging (ECGI) is a novel imaging modality for noninvasive electroanatomic mapping of epicardial activation and repolarization. METHODS AND RESULTS Fourteen pediatric patients with Wolff-Parkinson-White syndrome and no other congenital disease, were imaged with ECGI a day before and 45 minutes, 1 week, and 1 month after successful catheter ablation. ECGI determined that preexcitation sites were consistent with sites of successful ablation in all cases to within a 1-hour arc of each atrioventricular annulus. In the preexcited rhythm, activation-recovery interval (ARI) was the longest (349+/-6 ms) in the area of preexcitation leading to high average base-to-apex ARI dispersion of 95+/-9 ms (normal is approximately 40 ms). The ARI dispersion remained the same 45 minutes after ablation, although the activation sequence was restored to normal. ARI dispersion was still high (79+/-9 ms) 1 week later and returned to normal (45+/-6 ms) 1 month after ablation. CONCLUSIONS The study demonstrates that ECGI can noninvasively localize ventricular insertion sites of accessory pathways to guide ablation and evaluate its outcome in pediatric patients with Wolff-Parkinson-White syndrome. Wolff-Parkinson-White is associated with high ARI dispersion in the preexcited rhythm that persists after ablation and gradually returns to normal over a period of 1 month, demonstrating the presence of cardiac memory. The 1-month time course is consistent with transcriptional reprogramming and remodeling of ion channels.
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Affiliation(s)
- Subham Ghosh
- Cardiac Bioelectricity and Arrhythmia Center, Department of Biomedical Engineering, Washington University, St Louis, MO, USA
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132
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Bucciarelli-Ducci C, Denes P, Holly TA, Wu E. Pseudo Wellens T-waves in patients with suspected myocardial infarction: How cardiac magnetic resonance imaging can help the diagnosis. Int J Cardiol 2008; 128:e68-71. [PMID: 17720261 DOI: 10.1016/j.ijcard.2007.05.062] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Accepted: 05/19/2007] [Indexed: 10/22/2022]
Abstract
Wellens' syndrome is characterized by symmetrically inverted T-waves in the precordial leads suggestive of impending myocardial infarction due to a critical proximal left anterior descending (LAD) stenosis. We describe three unusual cases of patients with such electrocardiographic abnormality in which coronary angiography ruled out the presence of critical coronary stenosis and cardiac magnetic resonance imaging excluded the presence of acute or chronic myocardial infarction.
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133
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Erdogan O, Aktoz M. Right ventricular outflow tract pacing: relation of high to low synchronous ventricular activation with cardiac memory. Int J Cardiol 2008; 127:e27-9. [PMID: 17445924 DOI: 10.1016/j.ijcard.2007.01.084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Accepted: 01/04/2007] [Indexed: 11/29/2022]
Abstract
Cardiac memory is usually observed after right ventricular apical pacing and considered to be related to alter asynchronous activation by apical pacing. However, it is not known whether it occurs by unaltered high to low synchronous ventricular activation by right ventricular outflow tract (RVOT) pacing. We present here a case with dual chamber pacemaker whose ventricular lead positioned in the RVOT and developed cardiac memory immediately after ventricular pacing had stopped and the underlying sinus rhythm resumed.
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134
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Elizari MV. Mauricio Rosenbaum: The Internationally Renowned Electrocardiologist South of the Equator (1921-2003). Ann Noninvasive Electrocardiol 2008; 13:86-91. [DOI: 10.1111/j.1542-474x.2007.00205.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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135
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Sosunov EA, Anyukhovsky EP, Rosen MR. Altered ventricular stretch contributes to initiation of cardiac memory. Heart Rhythm 2008; 5:106-13. [DOI: 10.1016/j.hrthm.2007.09.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Accepted: 09/07/2007] [Indexed: 11/24/2022]
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136
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Lee KT, Chu CS, Lin TH, Yen HW, Voon WC, Sheu SH, Lai WT. Effect of sodium and calcium channel blockers on short-term cardiac memory in humans. Int J Cardiol 2008; 123:94-101. [PMID: 17320222 DOI: 10.1016/j.ijcard.2006.11.151] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Revised: 11/10/2006] [Accepted: 11/13/2006] [Indexed: 11/15/2022]
Abstract
BACKGROUND Cardiac memory (CM) can be induced by both short and long period of pacing from the right ventricle. Although several mechanisms have been proposed in animal studies, mechanisms of CM in humans are not well studied. METHODS A total of 46 patients (20 females; mean age 46+/-13 years) with paroxysmal supraventricular tachycardia referred for catheter ablation were enrolled. After catheter ablation, CM was induced by 20 min of pacing from right ventricular apex (RVA). The CM was quantified as the difference of T wave area in each lead between baseline and after RVA pacing. After complete recovery from the induced CM, verapamil (1.5 mg/kg; 0.005 mg/kg/min), lidocaine (1 mg/kg; 2 mg/min), procainamide (10 mg/kg; 4 mg/min), and nitroglycerine (0.6 mg sublingually; 5 microg/min), were given in 14, 10, 12, and 10 patients respectively. The pacing procedure was repeated and the degrees of CM were compared before and after each drug administered. RESULTS The short-term CM was demonstrated by changes in T wave area after RVA pacing in all patients. The degrees of CM were suppressed in patients after verapamil and lidocaine. In contrast, procainamide and nitroglycerin had no significant effect on the degrees of CM expression. CONCLUSIONS The expression of short-term CM can be suppressed by verapamil and lidocaine but not by procainamide and nitroglycerin. The results may suggest that short-term CM in humans can be modulated by calcium dependent process and the functional alternations of sodium and potassium channels.
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Affiliation(s)
- Kun-Tai Lee
- Department of Internal Medicine, College of Medicine, Kaohsiung Medicine University, Kaohsiung, Taiwan
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137
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Wylie JV, Zimetbaum P, Josephson ME, Shvilkin A. Cardiac memory induced by QRS widening due to propafenone toxicity. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2007; 30:1161-4. [PMID: 17725763 DOI: 10.1111/j.1540-8159.2007.00830.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Propafenone toxicity can cause significant QRS widening and markedly abnormal ventricular activation pattern. Aberrant ventricular activation upon its resolution is known to produce persistent T-wave changes known as "cardiac memory" (CM). A 74-year-old woman presented with a severely abnormal electrocardiogram consistent with propafenone toxicity. As her QRS complex narrowed, T-wave inversions developed with the T-wave axis and resolution kinetics consistent with CM. Abnormal ventricular activation due to propafenone toxicity can result in CM development.
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Affiliation(s)
- John V Wylie
- Harvard-Thorndike Electrophysiology Institute,Harvard Medical School, Boston, Massachusetts, USA
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138
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Shimizu W. Proarrhythmic effect of altered ventricular activation sequence in patients with permanent pacemaker. Heart Rhythm 2007; 4:1487-8. [PMID: 18068634 DOI: 10.1016/j.hrthm.2007.08.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Indexed: 11/26/2022]
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139
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140
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Sovari AA, Farokhi F. When the heart remembers. Am J Emerg Med 2007; 25:831-3. [PMID: 17870490 DOI: 10.1016/j.ajem.2007.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2006] [Revised: 01/04/2007] [Accepted: 01/05/2007] [Indexed: 11/18/2022] Open
Abstract
We present a 61-year-old patient who showed deep T wave inversion on her electrocardiogram (ECG) after cardioversion of her atrial flutter to sinus rhythm. A cardiac catheterization showed normal coronary arteries. The T wave inversion on her ECG is thought to be due to a cardiac memory phenomenon. Cardiac memory is a phenomenon that appears with T wave inversion on ECG after a change in the activation sequence of the heart. It may mimic cardiac ischemia and may mask any condition that appears with T wave abnormality on the ECG.
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Affiliation(s)
- Ali A Sovari
- Department of Internal Medicine, University of Illinois, COM-UC, Urbana, IL 61801, USA.
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141
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Right ventricular pacing-induced electrophysiological remodeling in the human heart and its relationship to cardiac memory. Heart Rhythm 2007; 4:1477-86. [PMID: 17997360 DOI: 10.1016/j.hrthm.2007.08.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Accepted: 08/01/2007] [Indexed: 11/20/2022]
Abstract
BACKGROUND Right ventricular apical (RVA) pacing induces electrophysiological and structural remodeling. Cardiac memory (CM) evolves during the course of pacing and is readily apparent on electrocardiography (ECG) or vectorcardiography (VCG) when normal ventricular activation resumes. OBJECTIVE This study sought to assess ventricular repolarization (VR) changes during pacing and intermittent normal ventricular conduction by ECG and VCG and to determine the temporal and conformational evolution of CM. METHODS Twenty sick sinus patients received a dual-chamber rate-adaptive (DDD-R) pacemaker and were paced from the RVA endocardium. The pacemakers were programmed to a short AV delay to maximize ventricular preexcitation. The ECG and VCG were recorded before and 1 day after implantation, and then daily for the first week (n=6) or weekly for 5 to 8 weeks (n=14), with the pacemakers temporarily programmed to AAI (normal ventricular activation). RESULTS The first parameters to change were T-vector amplitude, T(area), and T(peak)-T(end) (T(p-e)), which decreased within 1 day after initiating pacing. CM became apparent between day 1 and day 3, was fully established after 1 week, and then remained stable. Signs of increased VR heterogeneity were observed as the T loop became more circular (decreased T(egenv)) and distorted (increased T(avplan)), which have previously been observed in conditions with increased risk for arrhythmias. Over weeks, VR duration was prolonged (increased QTc). In contrast, during ventricular pacing, a gradual shortening of the repolarization time was observed, suggesting a stabilizing adaptive process. CONCLUSION In sick sinus syndrome patients in whom ventricular pacing is indicated, switching between normal AV conduction and ventricular pacing should be minimized to avoid periods of repolarization instability.
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Krishnan J, Sachdeva G, Chakravarthy VS, Radhakrishnan S. Interpreting voltage-sensitivity of gap junctions as a mechanism of cardiac memory. Math Biosci 2007; 212:132-48. [PMID: 18316101 DOI: 10.1016/j.mbs.2007.05.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 05/06/2007] [Accepted: 05/09/2007] [Indexed: 11/16/2022]
Abstract
Memory in the nervous system is essentially a network effect, resulting from activity-dependent synaptic modification in a network of neurons. Like the nervous system, the heart is a network of cardiac cells electrically coupled by gap junctions. The heart too has memory, termed cardiac memory, whereby the effect of an external electrical activation persists long after the presentation of stimulus is terminated. We have earlier proposed that adaptation of gap junctions, as a function of membrane voltages of the cells that are coupled by the gap junctions, is related to cardiac memory [V.S. Chakravarthy, J. Ghosh, On Hebbian-like adaption in heart muscle: a proposal for "Cardiac Memory", Biol. Cybern. 76 (1997) 207, J. Krishnan, V.S. Chakravarthy, S. Radhakrishnan, On the role of gap junctions on cardiac memory effect, Comput. Cardiol. 32 (2005) 13]. Using the proposed mechanism, we demonstrate memory effect using computational models of interacting cell pairs. In this paper, we address the biological validity of the proposed mechanism of gap junctional adaptation. It is known from electrophysiology of gap junctions that the conductance of these channels adapts as a function of junctional voltage. At a first sight, this form of voltage dependence seems to be at variance with the form required by our mechanism. But we show, with the help of a theoretical model, that the proposed mechanism of voltage-dependent adaptation of gap junctions, is compatible with the known voltage-sensitivity of gap junctions observed in electrophysiological studies. Our analysis suggests a new significance of the voltage-sensitivity of gap junctions and its possible link to the phenomenon of cardiac memory.
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Affiliation(s)
- J Krishnan
- Biomedical Engineering Group, Department of Applied Mechanics, Indian Institute of Technology, Madras, India.
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144
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Jeyaraj D, Wilson LD, Zhong J, Flask C, Saffitz JE, Deschênes I, Yu X, Rosenbaum DS. Mechanoelectrical feedback as novel mechanism of cardiac electrical remodeling. Circulation 2007; 115:3145-55. [PMID: 17562957 DOI: 10.1161/circulationaha.107.688317] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Altered electrical activation of the heart by pacing or disease induces profound ventricular electrical remodeling (VER), manifested electrocardiographically as T-wave memory and ultimately as deleterious mechanical remodeling from heterogeneous strain. Although T-wave memory is associated with altered expression of sarcolemmal ion channels, the biophysical mechanisms responsible for triggering remodeling of cardiac ion channels are unknown. METHODS AND RESULTS To test the hypothesis that mechanoelectrical feedback triggered by regional strain is a mechanism for VER, dogs (n=6) underwent 4 weeks of ventricular pacing to induce VER. Multisegment transmural optical action potential imaging of left ventricular wedges revealed profound and selective prolongation of action potential duration in late-activated (288+/-29 ms) compared with early-activated (250+/-9 ms) myocardial segments (P<0.05), providing the first experimental evidence that amplification of repolarization gradients between segments of left ventricle is the electrophysiological basis for T-wave memory. In vivo tagged magnetic resonance imaging revealed a 2-fold and preferential increase in circumferential strain in late-activated segments of myocardium, which exactly coincided with segments undergoing VER. VER could not be attributed to structural remodeling because it occurred without any histological evidence of cellular hypertrophy. CONCLUSIONS The mechanism responsible for triggering remodeling of ion channel function in VER was locally enhanced circumferential strain. These data suggest a novel mechanoelectrical feedback mechanism for inducing physiological and potentially deleterious electrical heterogeneities in the heart.
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Affiliation(s)
- Darwin Jeyaraj
- Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 MetroHealth Dr, Cleveland, OH 44109-1998, USA
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145
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Lee KT, Chu CS, Lu YH, Lin TH, Yen HW, Voon WC, Sheu SH, Lai WT. Modulation of the expression of long-term cardiac memory by short-term cardiac memory in patients with Wolff-Parkinson-White syndrome after catheter ablation. Circ J 2007; 71:331-7. [PMID: 17322630 DOI: 10.1253/circj.71.331] [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: 11/09/2022]
Abstract
BACKGROUND The interaction between long-and short-term cardiac memory (CM) is unknown. METHODS AND RESULTS The T-wave areas and QTc intervals in each ECG lead were analyzed in 11 patients with manifest Wolff-Parkinson-White syndrome with posterior or septal accessory pathway (4 females; mean age: 47+/-12 years) in the following ECGs: (1) immediately after catheter ablation (post-ablation ECG); (2) immediately after 20 min of right ventricular outlet pacing (post-pacing ECG); and (3) 1 week after ablation (recovery ECG). Compared with the post-ablation ECGs, the T-wave areas of the recovery ECGs in leads II and aV(F) changed dramatically from negative to positive while that in lead III became less negative (p<0.01), and those in leads I, aV(L), and V(2-4) became less positive (p<0.05). Compared with the post-ablation ECGs, the T-wave areas of the post-pacing ECGs in leads III and aV(F) became less negative (p<0.01), and those in leads I, aV(L), and V(2-4) became less positive (p<0.05). The QTc interval in the post-ablation ECG was significantly longer than in either the post-pacing or recovery ECGs (p<0.05). CONCLUSIONS Mechanisms involved in the expression of long-term CM could be affected by short-term CM.
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Affiliation(s)
- Kun-Tai Lee
- Department of Internal Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
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Hegazy AM, Alkandary MH. Cardiac memory versus likelihood of ischemic heart disease in hypertensive patients with ventricular repolarization abnormalities after repetitive uniform ventricular extrasystoles. Med Princ Pract 2007; 16:193-7. [PMID: 17409753 DOI: 10.1159/000100389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Accepted: 10/11/2006] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVES To investigate the value of T-wave inversion after premature ventricular complexes (PVCs) for the prediction of hypertensive patients with a likelihood of ischemic heart disease (IHD). PATIENTS AND METHODS Ambulatory 24-hour ECG, ambulatory 24-hour blood pressure (BP) recording, echocardiography, treadmill exercise ECG test and thallium-201 scintigraphy were performed for 210 hypertensive patients. RESULTS Predictive indices showed that persistent symmetrical T-wave inversion after repetitive uniform PVCs equaling 30 min can be considered an indicator for the prediction of IHD in hypertensive patients as sensitivity was 80%, specificity: 73%, accuracy: 78%, positive predictive value: 83%, and negative predictive value: 69%. kappa coefficient value (kappa) indicated that there was good agreement between changes in ventricular repolarization after PVCs and stress thallium scintigraphy (kappa = 0.897). Receiver-operating characteristic curve data showed that the ideal cutoff value of T-wave inversion voltage to predict IHD in hypertensive patients was 2.2 mV (sensitivity: 66% and false positive: 35%, and area under curve: 0.716), but the ideal cutoff value of time for resolution of T-wave inversion was 34 min (sensitivity: 83% and false positive: 18%, and area under curve: 0.873). Multivariate analysis revealed that T-wave inversion after repetitive uniform PVCs was significantly associated with non-sustained ventricular tachycardia, decreased parasympathetic activity, increased sympathetic activity, morning BP surge, systolic BP load >50% and left ventricular diastolic dysfunction status. CONCLUSION The data show that persistent symmetrical T-wave changes following resumption of sinus rhythm after repetitive uniform PVCs are an independent variable for the prediction of IHD in hypertensive patients.
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Electrocardiography. CARDIOVASCULAR MEDICINE 2007. [DOI: 10.1007/978-1-84628-715-2_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Conrath CE, Opthof T. Ventricular repolarization: An overview of (patho)physiology, sympathetic effects and genetic aspects. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2006; 92:269-307. [PMID: 16023179 DOI: 10.1016/j.pbiomolbio.2005.05.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Most textbook knowledge on ventricular repolarization is based on animal data rather than on data from the in vivo human heart. Yet, these data have been extrapolated to the human heart, often without an appropriate caveat. Here, we review multiple aspects of repolarization, from basic membrane currents to cellular aspects including extrinsic factors such as the effects of the sympathetic nervous system. We critically discuss some mechanistic aspects of the genesis of the T-wave of the ECG in the human heart. Obviously, the T-wave results from the summation of repolarization all over the heart. The T-wave in a local electrogram ideally reflects local repolarization. The repolarization moment is composed of the moment of local activation plus local action potential duration (APD) at 90% repolarization (APD90). The duration of the latter largely depends on the balance between L-type Ca2+ current and the delayed rectifier currents. Generally speaking, there is an inverse relationship between local activation time and local APD90, leading to less dispersion in repolarization moments than in activation moments or in APD90. In transmural direction, the time needed for activation from endocardium toward epicardium has been considered to be overcompensated by shorter APD90 at the epicardium, leading to the earliest repolarization at the subepicardium. In addition, mid-myocardial cells would display the latest repolarization moments. The sparse human data available, however, do not show any transmural dispersion in repolarization moment. Also, the effect of adrenergic stimulation on APD90 has been studied mainly in animals. Again, sparse human data suggest that the effect of adrenergic stimulation is different in the human heart compared to many other mammalian hearts. Finally, aspects of the long QT syndrome are discussed, because this intrinsic genetic disease results from repolarization disorders with extrinsic aspects.
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Affiliation(s)
- Chantal E Conrath
- Department of Cardiology, University Medical Center, Utrecht, The Netherlands.
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149
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Affiliation(s)
- Michael R. Franz
- Georgetown University and Veteran Affairs Medical Center, Washington, D.C
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150
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Affiliation(s)
- Chetan Shenoy
- Department of Internal Medicine, Guthrie/Robert Packer Hospital, Sayre, Penn 18840, USA.
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