Electrophysiologic studies (EPS) were performed in 155 patients with hypertrophic cardiomyopathy (HCM). Indications for EPS were cardiac arrest in 22 patients, syncope in 55 patients, presyncope in 37 patients, asymptomatic ventricular tachycardia (VT) in 24 patients, palpitations in 10 patients, and a strong family history of sudden cardiac death in seven patients. Thirty-five (23%) patients had significant resting left ventricular outflow tract obstruction. Electrophysiologic abnormalities were present in 126 (81%) patients. A high prevalence of abnormal sinus-node function (66%) and His-Purkinje (HV) conduction (30%) was noted. The most commonly induced supraventricular arrhythmias were atrial reentrant tachycardia and atrial fibrillation (10% and 11% of patients, respectively). Accessory atrioventricular pathways were present in seven (5%) patients. Programmed ventricular stimulation (PVS) induced nonsustained ventricular tachycardia in 22 (14%) patients and sustained ventricular arrhythmia in 66 (43%) patients. Sustained ventricular arrhythmia was polymorphic VT in 48 (73%) patients, monomorphic VT in 16 (24%) patients, and ventricular fibrillation in two (3%) patients. Induction was with two premature stimuli in 19 (29%) patients and three premature stimuli in 47 (71%) patients. Of 17 cardiac arrest survivors with sustained ventricular arrhythmia, 16 (94%) patients required three premature stimuli for arrhythmia induction. Sustained ventricular arrhythmia was induced at a right ventricular site in 51 (77%) patients and at a left venticular site in 15 (23%) patients. Univariate analysis showed a significant (p < 0.05) association between inducibility of sustained ventricular arrhythmia and VT on Holter in patients with a history of cardiac arrest or syncope but not in patients with presyncope or asymptomatic patients. Multivariate logistic regression analysis revealed that the following were significantly associated with inducibility of sustained ventricular arrhythmia: clinical presentation (cardiac arrest more than syncope more than presyncope more than asymptomatic patients, p = 0.0002: chronic or inducible atrial fibrillation, p = 0.002: and male gender, p = 0.04). In contrast, there was no clinical correlate of induced nonsustained VT. We conclude that: 1) EPS commonly identify abnormalities in selected HCM patients, 2) induction of VT occurs more commonly in patients with severe clinical manifestations of HCM, 3) VT on Holter is associated with increased ventricular electrical instability in patients with sudden cardiac arrest or syncope but not in less symptomatic patients, 4) PVS using less than three premature stimuli induces VT in only a small percentage of HCM patients with serious clinical manifestations, and 5) induction of sustained ventricular arrhythmia with three or less premature stimuli (polymorphic VT in most patients) is an abnormal finding in HCM that may provide a useful guide to therapy.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)