Relation of electrocardiographic patterns to phenotypic expression and clinical outcome in hypertrophic cardiomyopathy.

Twelve-lead electrocardiography, a traditional component in evaluations of patients with hypertrophic cardiomyopathy (HC), is often regarded as a marker for the magnitude of left ventricular (LV) hypertrophy, which in turn has been linked to sudden death risk. To determine whether electrocardiographic (ECG) patterns have clinical utility by accurately reflecting phenotypic expression or predicting clinical outcome, voltages and patterns were compared with LV wall thicknesses assessed by echocardiography and with clinical outcomes in 448 consecutive patients with HC. Significant but relatively weak correlations were evident between maximum LV wall thickness and ECG voltage: r = 0.295 (p <0.01) for the sum of R- and S-wave voltages in all 12 leads, r = 0.254 (p <0.01) for the maximum R or S wave in any lead, and r = 0.210 (p <0.01) for the sum of SV(1) (or SV(2)) and RV(5) (or RV(6)). Of 55 patients with extreme LV hypertrophy (LV wall thickness > or =30 mm), only 24 (44%) showed greatly increased ECG voltage > or =30 mm in any lead. Of 102 patients with outflow gradients > or =30 mm Hg at rest, only 43 (42%) had ECG voltage > or =30 mm in any lead. Normal ECG results were uncommonly associated with HC-related death (1 of 40 patients, 2.5%) but had similar prevalence in surviving patients (17 of 376 patients, 4.5%; p = NS). In conclusion, in HC, 12-lead ECG voltages are not a reliable clinical marker for the magnitude of LV hypertrophy or outflow obstruction. Diverse ECG patterns, consistent with heterogeneous expression of this disease, did not predict HC-related death. Scalar electrocardiography has selective but limited power in routine clinical assessments of patients with HC.

Cardioverter-defibrillator implantation in high-risk patients with hypertrophic cardiomyopathy.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) are used with increasing frequency in hypertrophic cardiomyopathy (HCM) patients of all ages for primary and secondary sudden death prevention. Concerns may arise regarding the safety of device implantation because of unique clinical and phenotypic expressions of HCM. OBJECTIVES: The purpose of this study was to assess the efficacy and safety of ICD placement in high-risk patients with HCM. METHODS: We analyzed the experience with ICDs and transvenous lead systems in 75 consecutive HCM patients at the Minneapolis Heart Institute from 1993 to 2004. RESULTS: The age of the study group patients was 12 to 79 years (mean 36 +/- 16). Patients received ICDs for secondary (n = 4, after cardiac arrest) or primary prevention (n = 71, with > or = 1 risk factor). Thirty-one patients demonstrated disease features that potentially impacted methodology and safety of the implant procedure, most commonly massive left ventricular (LV) hypertrophy and outflow obstruction > or = 50 mmHg. There were no procedure-related deaths; defibrillator implants were successful and uneventful in 71 of 75 patients (95%). In 3 of the 75 patients (4%), defibrillation was unsuccessful because of high thresholds, associated with extreme hypertrophy (wall thickness > 45 mm) and/or ongoing amiodarone therapy. In two of these patients, thoracotomy with epicardial lead placement achieved successful defibrillation; ICD therapy was abandoned in the other patient. CONCLUSION: ICD placement in children and adults with HCM is generally safe and effective. However, in some patients with massive LV hypertrophy and/or prior administration of amiodarone, transvenous defibrillation proved difficult, and epicardial lead placement was required. High-energy ICD devices and defibrillation threshold testing are recommended for most high-risk HCM patients.