Journal List > Korean Circ J > v.37(11) > 1016281

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Kim, Nam, Kang, Hong, Jang, Kim, Jo, Kim, Park, Choi, and Kim: A Clinical Observation of Patients with Hypertrophic Cardiomyopathy and Implantable Cardioverter-Defibrillators
Original Article
Korean Circulation Journal

Korean Circulation Journal 2007; 37(11): 574-580.

Published online: 30 November 2007

DOI: https://doi.org/10.4070/kcj.2007.37.11.574

A Clinical Observation of Patients with Hypertrophic Cardiomyopathy and Implantable Cardioverter-Defibrillators

Jong Wook Kim, MD, Gi-Byoung Nam, MD, Byung Wook Kang, MD, Yoonki Hong, MD, Eun Young Jang, MD, Mi-Young Kim, MD, Jae-Cheol Jo, MD, Hyoung Young Kim, MD, Kyoung-Min Park, MD, Kee-Joon Choi, MD, You-Ho Kim, MD

Division of Cardiology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.

Correspondence: You-Ho Kim, MD, Division of Cardiology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea. Tel: 82-2-3010-3161, Fax: 82-2-486-5918, youho@amc.seoul.kr

Received 2 June 2007       Revised 18 July 2007       Accepted 30 August 2007

Copyright © 2007 The Korean Society of Cardiology

Abstract

Background and Objectives

Hypertrophic cardiomyopathy (HCM) is one of the most common heritable cardiac diseases. Patients with HCM are prone to ventricular tachyarrhythmias, and implantable cardioverter-defibrillator (ICD) implantation is recommended in high-risk patients to prevent sudden death. Clinical and tachycardial characteristics in patients with HCM have not been studied systematically.

Subjects and Methods

Between April 1996 and February 2006, 23 patients with HCM underwent implantation of ICDs. ICDs were indicated for primary prevention in 9 patients and for secondary prevention in 14 patients. Clinical features, follow-up events and intracardiac electrograms were reviewed.

Results

During a median follow-up period of 561 days (range 16 to 2,694 days), a total of 51 episodes of ventricular tachycardia (VT) occurred in 6 patients, while only one episode of ventricular fibrillation (VF) was recorded. There were 45 (64.2%) appropriate shocks [30 defibrillation shocks in 5 patients and 15 antitachycardia pacings (ATP) in 2 patients] in 6 patients, and 25 (35.7%) inappropriate shocks in 7 patients. The coupling intervals and VT cycle lengths were highly variable within individual patients. Over-drive acceleration in response to ATP was observed in 1 patient.

Conclusion

As ventricular tachycardia is the main ventricular tachyarrhythmia in patients with HCM, an empirical ATP setting for VTs appears to be mandatory even in patients without previously documented VT. Based on the analyses of the intracardiac electrograms (presence of overdrive acceleration, variations in coupling intervals and cycle lengths), triggered activity may have an important role in the mechanism of a ventricular tachycardia.

Keywords: Cardiomyopathy, hypertrophic, Tachycardia, ventricular, Defibrillators, implantable, Death, sudden, cardiac

Figures and Tables

Fig. 1
The Indications for ICD implantation at Asan Medical Center. Post-MI VT, Brugada syndrome, HCM were the three major causes of ICD implantation at Asan Medical Center. In 17% of total ICD implantations, HCM was the underlying heart disease. MI: myocardial infarction, VT: ventricular tachycardia, HCM: hypertrophic cardiomyopathy, DCM: dilated cardiomyopathy, ARVD: arrhythmogenic right ventricular dysplasia, Post-op: post-operation.
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Fig. 2
A marked variation in the coupling interval and ventricular tachycardial cycle length (Patient number 3). The panel A, B, C show 3 intracardiac electrograms recorded from patient number 3 during different VT events. The coupling intervals were 531, 875, 805 msec respectively (indicated as double-headed arrows), and the mean VT cycle lengths were 370, 336, 429 msec respectively for each episode. Within the same patient, coupling intervals and VT cycle lengths were highly variable. VT: ventricular tachycardia.
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Fig. 3
Distribution of coupling intervals and ventricular tachycardial cycle lengths. Coupling intervals and VT cycle lengths were measured by analyzing intracardiac electrograms recorded on ICDs. Coupling intervals and VT cycle lengths were highly variable within each patient. VTCL: ventricular tachycardial cycle length, CI: coupling interval, VT: ventricular tachycardia, ICD: implantable cardioverter-defibrillator.
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Fig. 4
An example of overdrive acceleration in patient number 1. An example of overdrive acceleration is shown. The VT cycle length is changed from an average of 333±27 msec to 294±22 msec after anti-tachycardia pacing. This was subsequently terminated by a defibrillation shock (not shown on the figure). VT: ventricular tachycardia.
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Table 1
Indications for ICD implantation
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Indications for ICD insertion for each patient are listed in this table. In some patients, inducible VT during electrophysiologic study was included as an indication of ICD insertion for primary prevention (This was considered as an indication in previous studies,10) but the relevance of invasively induced arrhythmias appeared to be limited in successive stidies13)). ICD: implantable cardioverter-defibrillator, Pt. No.: the number of patient, SCD: sudden cardiac death survivor, VT: ventricular tachycardia, Family Hx: family history of sudden cardiac death, NSVT: non-sustained ventricular tachycardia during 24 hour Holter monitoring, EPS: ventricular tachycardia induced during electrophysiologic study, EchoCG: excessive LV wall hypertrophy on echocardiography, TMT: abnormal BP response to treadmill test, Second ary: secondary prevention, Primary: primary prevention, ATP: anti-tachycardia pacing setting

Table 2
Characteristics of the study subjects
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*Mean±standard deviation. LV: left ventricle, LVEF: left ventricular ejection fraction

Table 3
The type of ventricular tachyarrhythmias and the ICD discharges
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Ventricular tachyarrhythmias occurred in 6 patients. The types of ventricular tachyarrhythmia and ICD discharge are described in this table. 4 patients received 30 defibrillation shocks and 2 patients received 15 antitachycardia pacings. Except for one case of overdrive acceleration which needed defibrillation shock for termination in patient number 1, all ATPs successfully terminated VTs. ATP setting was not done in patient number 2 due to LV outflow tract obstruction and mitral regurgitation with possible hemodynamic instability during ATP, in patients number 3 and 4 due to presence of fast VT, and in patient number 5 because there had been no previously documented VTs. ICD: implantable cardioverter-defibrillator, Pt. No.: the number of patient, VT: ventricular tachycardia, VF: ventricular fibrillation, ATP: antitachycardia pacing

Table 4
Summary of ventricular arrhythmia
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In every patient, the onsets and terminations of VT were abrupt. Overdrive acceleration was noted in one patient (patient number 1). Pt. No.: the number of patient, VTCL: ventricular tachycardial cycle length, CI: coupling interval, VT: ventricular tachycardia

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