Methods

This was a retrospective review of consecutive HC patients with a diagnosis of apical HC who underwent cardiac MRI examinations at the Mayo Clinic (Rochester, MN) from August 1999 to October 2011. We used the standard clinical and echocardiographic criteria in the absence of other diseases capable of explaining the extent of hypertrophy to define HC. The study was approved by the Mayo Clinic Institutional Review Board.

Clinical and demographic data from the electronic medical records at the time of cardiac MRI study were abstracted. This included age, gender, ethnicity, genotype, and structural subtype. Co-morbidities included hypertension, diabetes mellitus, coronary artery disease, defined by either angiographically (invasive or CT) proven 50% stenosis or previous myocardial infarction, history of atrial fibrillation, and history of syncope. First-degree family history of HC and sudden cardiac death were recorded. Severe symptoms were defined as the presence of either New York Heart Association class ≥3 dyspnea or Canadian Cardiovascular Society angina class ≥3. Any subsequent surgical intervention and ICD implantation were recorded.

Additional data were abstracted in patients with electrocardiography (ECG) and Holter monitoring within 6 months of cardiac MRI. ECGs were examined for PR, QRS, and QT interval duration, ST-segment and T-wave changes, and the presence of bundle branch block and atrial fibrillation. Holter reports were examined for the presence of total ventricular beats, ventricular couplets or bigeminy, and number of nonsustained ventricular tachycardia episodes (NSVTs) defined as 3 or more consecutive ventricular beats.

Two-dimensional echocardiograms performed within 6 months of the cardiac MRI were reviewed in each patient. Magnitude and distribution of LV hypertrophy, intracavitary and LV outflow tract velocities, strain rate analysis, and the presence or absence of apical pouches and thrombus were recorded.

Cardiac MRIs were reviewed for magnitude and distribution of LV hypertrophy, apical pouch, thrombus, LV outflow tract obstruction, systolic anterior motion of the mitral valve, and the presence and distribution of late gadolinium enhancement (LGE). LV ejection fraction, LV end-systolic and end-diastolic diameters and volumes, LV end-diastolic mass, and maximal (end-diastolic) septal thickness were analyzed using steady-state free precession sequences in multiple imaging planes. The myocardial delayed enhancement sequence that was used for the assessment of myocardial viability is a conventional 2-dimensional inversion recovery gradient-echo pulse sequence. A double dose of gadolinium (0.2 mmole/kg) was infused, and LGE imaging occurred at approximately 10 minutes after the administration of contrast. LGE enhancement data were taken from the clinical report and did not use any automated software to ascribe a threshold for enhancement. All studies were performed on a 1.5-T MRI scanner (Signa Twin Speed Excite; General Electric, Waukesha, Wisconsin).

Mean ± SD or number (frequency) are presented to summarize data for continuous and nominal variables, respectively. Pearson’s chi-square tests test was used to compare categorical data. Independent, 2-sample t tests were used to compare continuous data; p <0.05 was considered statistically significant. Analysis was performed using SPSS Statistics software, version 19 (IBM, Armonk, New York).