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Intracardiac T-Wave Alternans and Ventricular Arrhythmia in Long-QT Syndrome GARETH J. PADFIELD, M.B.Ch.B., Ph.D., CHRISTIAN STEINBERG, M.D., Ph.D., and JOHN A. YEUNG-LAI-WAH, M.B.Ch.B., F.R.C.P.C. From the Heart Centre, St. Paul’s Hospital, University of British Columbia, Vancouver, Canada
Basic: cardiac fibrillation/defibrillation, Clinical: electrophysiology – long-QT, Clinical: implantable devices – ventricular tachycardia/fibrillation Case History A 30-year-old woman with genotype positive long-QT syndrome (KCNQ1 and V205M mutations) was admitted following recurrent shocks from her implantable cardioverter defibrillator (ICD). In the days preceding her admission she had been heavily intoxicated with alcohol, and suffering from a diarrheal illness. On examination, she was exhibiting signs and symptoms of acute alcohol withdrawal but was hemodynamically stable in a paced atrial rhythm. Routine biochemistry was unremarkable. A 12-lead ECG demonstrated atrial pacing at a rate of 80 bpm with normal PR and QRS durations. The corrected QT interval was massively prolonged to 690 milliseconds, with marked beat-to-beat T-wave alternans (TWA) (Fig. 1). Interrogation of the ICD confirmed several appropriate shocks for ventricular fibrillation (VF), all preceded by TWA and premature ventricular depolarizations, which were evident on the intracardiac electrograms (Fig. 2). She was admitted to hospital for observation and treatment with benzodiazepines. Her QT interval gradually returned to baseline without further ventricular arrhythmias. The QTc prior to discharge remained prolonged; however, TWA was no longer present. J Cardiovasc Electrophysiol, Vol. 26, pp. 1155-1156, October 2015. No disclosures. Address for correspondence: Dr. Gareth Padfield, M.B.Ch.B., Ph.D., Clinical Fellow in Cardiac Electrophysiology and Device Therapy, Division of Cardiology, University of British Columbia; E-mail: [email protected] doi: 10.1111/jce.12668
T-wave alternans is an important sign of electrical instability that often precedes ventricular arrhythmia, classically torsade de pointes.1 Both temporal and spacial dispersion of repolarization are thought to contribute to TWA. Progressive increments in QT dispersion from beat to beat can culminate in unidirectional block at sites of delayed repolarization, and this may lead to re-entry of depolarization sufficient to initiate ventricular fibrillation.2 Triggered activity by late after depolarizations may be another important mechanism by which ventricular arrhythmia develops in this setting. The most common clinical manifestation is microvolt alternans, cyclical variation in repolarization too small to be detected on the surface ECG. Macrovolt alternans such as in this case indicate severe repolarization abnormalities and impeding ventricular arrhythmia. Although classically described in long-QT syndrome, TWA also occurs in other conditions not necessarily associated with prolongation of the QT interval, such as congestive cardiac failure.3 The presence of TWA of intracardiac electrograms of ICD recipients is likely to be clinically relevant and can serve as a predictor of recurrent ICD shocks.4 References 1. Grabowski M, Karpinski G, Filipiak KJ, Opolski G: Images in cardiovascular medicine. Drug-induced long-QT syndrome with macroscopic T-wave alternans. Circulation 2004;110:e459-e460. 2. Narayan SM: T-wave alternans and the susceptibility to ventricular arrhythmias. J Am Coll Cardiol 2006;47:269-281. 3. Klingenheben T, Zabel M, D’Agostino RB, Cohen RJ, Hohnloser SH: Predictive value of T-wave alternans for arrhythmic events in patients with congestive heart failure. Lancet 2000;356:651-652. 4. Kim JW, Pak HN, Park JH, Nam GB, Kim SK, Lee HS, Jang JK, Choi JI, Kim YH: Defibillator electrogram T wave alternans as a predictor of spontaneous ventricular tachyarrhythmias in defibrillator recipients. Circ J 2009;73:55-62.
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Journal of Cardiovascular Electrophysiology
Vol. 26, No. 10, October 2015
Figure 1. Surface 12-lead ECG at hospitalization demonstrating atrial pacing at 80 bpm with gross prolongation of the QTc interval. There is clear variation in the T-wave morphology with alternate beats; however, it is quite variable in different leads. Lead II, for instance, which is frequently used as a rhythm strip (as in this case) for monitoring purposes, would miss the diagnosis. This emphasizes the importance of a 12-lead ECG.
Figure 2. Intracardiac ECG of a typical event leading to VF and an ICD shock. T-wave alternans is evident with increasing magnitude of T-wave distortion leading to premature ventricular depolarization and the initiation of VF.
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Intracardiac T-Wave Alternans and Ventricular Arrhythmia in Long-QT Syndrome GARETH J. PADFIELD, M.B.Ch.B., Ph.D., CHRISTIAN STEINBERG, M.D., Ph.D., and JOHN A. YEUNG-LAI-WAH, M.B.Ch.B., F.R.C.P.C. From the Heart Centre, St. Paul’s Hospital, University of British Columbia, Vancouver, Canada
Basic: cardiac fibrillation/defibrillation, Clinical: electrophysiology – long-QT, Clinical: implantable devices – ventricular tachycardia/fibrillation Case History A 30-year-old woman with genotype positive long-QT syndrome (KCNQ1 and V205M mutations) was admitted following recurrent shocks from her implantable cardioverter defibrillator (ICD). In the days preceding her admission she had been heavily intoxicated with alcohol, and suffering from a diarrheal illness. On examination, she was exhibiting signs and symptoms of acute alcohol withdrawal but was hemodynamically stable in a paced atrial rhythm. Routine biochemistry was unremarkable. A 12-lead ECG demonstrated atrial pacing at a rate of 80 bpm with normal PR and QRS durations. The corrected QT interval was massively prolonged to 690 milliseconds, with marked beat-to-beat T-wave alternans (TWA) (Fig. 1). Interrogation of the ICD confirmed several appropriate shocks for ventricular fibrillation (VF), all preceded by TWA and premature ventricular depolarizations, which were evident on the intracardiac electrograms (Fig. 2). She was admitted to hospital for observation and treatment with benzodiazepines. Her QT interval gradually returned to baseline without further ventricular arrhythmias. The QTc prior to discharge remained prolonged; however, TWA was no longer present. J Cardiovasc Electrophysiol, Vol. 26, pp. 1155-1156, October 2015. No disclosures. Address for correspondence: Dr. Gareth Padfield, M.B.Ch.B., Ph.D., Clinical Fellow in Cardiac Electrophysiology and Device Therapy, Division of Cardiology, University of British Columbia; E-mail: [email protected] doi: 10.1111/jce.12668
T-wave alternans is an important sign of electrical instability that often precedes ventricular arrhythmia, classically torsade de pointes.1 Both temporal and spacial dispersion of repolarization are thought to contribute to TWA. Progressive increments in QT dispersion from beat to beat can culminate in unidirectional block at sites of delayed repolarization, and this may lead to re-entry of depolarization sufficient to initiate ventricular fibrillation.2 Triggered activity by late after depolarizations may be another important mechanism by which ventricular arrhythmia develops in this setting. The most common clinical manifestation is microvolt alternans, cyclical variation in repolarization too small to be detected on the surface ECG. Macrovolt alternans such as in this case indicate severe repolarization abnormalities and impeding ventricular arrhythmia. Although classically described in long-QT syndrome, TWA also occurs in other conditions not necessarily associated with prolongation of the QT interval, such as congestive cardiac failure.3 The presence of TWA of intracardiac electrograms of ICD recipients is likely to be clinically relevant and can serve as a predictor of recurrent ICD shocks.4 References 1. Grabowski M, Karpinski G, Filipiak KJ, Opolski G: Images in cardiovascular medicine. Drug-induced long-QT syndrome with macroscopic T-wave alternans. Circulation 2004;110:e459-e460. 2. Narayan SM: T-wave alternans and the susceptibility to ventricular arrhythmias. J Am Coll Cardiol 2006;47:269-281. 3. Klingenheben T, Zabel M, D’Agostino RB, Cohen RJ, Hohnloser SH: Predictive value of T-wave alternans for arrhythmic events in patients with congestive heart failure. Lancet 2000;356:651-652. 4. Kim JW, Pak HN, Park JH, Nam GB, Kim SK, Lee HS, Jang JK, Choi JI, Kim YH: Defibillator electrogram T wave alternans as a predictor of spontaneous ventricular tachyarrhythmias in defibrillator recipients. Circ J 2009;73:55-62.
1156
Journal of Cardiovascular Electrophysiology
Vol. 26, No. 10, October 2015
Figure 1. Surface 12-lead ECG at hospitalization demonstrating atrial pacing at 80 bpm with gross prolongation of the QTc interval. There is clear variation in the T-wave morphology with alternate beats; however, it is quite variable in different leads. Lead II, for instance, which is frequently used as a rhythm strip (as in this case) for monitoring purposes, would miss the diagnosis. This emphasizes the importance of a 12-lead ECG.
Figure 2. Intracardiac ECG of a typical event leading to VF and an ICD shock. T-wave alternans is evident with increasing magnitude of T-wave distortion leading to premature ventricular depolarization and the initiation of VF.
