BACKGROUND: An unusual form of hypertrophic cardiomyopathy localized to the left ventricular apex has racial differences in phenotypic expression between many Japanese reports and most reports from outside Japan. In Japanese patients follow up study of apical hyertrophy has shown benign clinical course without demonstrable genetic transmission, but other ethnic patients with this variant was clinically different from Japanese patients. The purpose of this study was to evaluate the clinical course and the progression of hypertrophy of apical hyper- trophic cardiomyopathy by echocardiography and to define the relationship between the severity of apical hypertrophic cardiomyopathy and the clinical course. METHODS: Between June 1990 and August 1996, 35 out of 53 patients with apical hypertrophic cardiomyopathy diagnosed by echocardiography were studied. In 26 out of 35 patients, two- dimensional echocardiography and EKG were obtained at initial visit and follow up. We analyzed the sum of S wave in lead Vl and R wave in lead VS(mm) and T wave negativity in lead V4 on EKG. Measured echocardiographic parameters were apical thickness and apical cross-sectional area of left ventricle at end-diastole in apical tour chamber view, anteroposterior left atrial dirnension at end systole in parasternal short axis view and pulsed-wave Doppler pattern of transmitral inflow. RESULTS: 1) Mean age at presentation was 57.9+8.3 years(range 37 to 72). Mean follow up duration of echocardiography and EKG were 29.5+/-13.5 months and 27.7+ -1.4 months, respectively. 2) Eleven(31%) out of 35 patients were asymptomatic at initial presentation. In the remaining 24 patients, major symptoms included atypical chest pain(n=7), angina (n=11), dyspnea(n=12), palpitation(n=4) and fatigue(n=l), During follow-up, symptoms aggravated in 5/35(14%), no change in 22/35(63%) and allenated in 8/35(23%). The clinical event during follow up was transient ischemic attack in 1 patient, syncope in 1 patient and death in 1 patient with cerebral infarction and upper gastrointestinal bleeding. 3) Electrocardiography revealed normal sinus rhphm in 24 patients and atrial fibrillation in 2 patients at initial presentation. Paroxysmal atrial fibrillation was observed in 1 patient during follow up period at 24 hours Holter monitoring. Negative T wave amplitude was increased from 11.5+/-5.5 to 13.1+/-6.5mm(p<0.05), however the sum of SV, and RV, did not change significantly. 4) The apical thickness and apical cross-sectional area changed over time, frorn 19.9+/- 3.2 to 21.8+/-4.lmm(p<0.005) with interobservers difference of 2.3+/-1.2mm and from 11.4+/-2.4 to 12.5+/-3.1cm(p<0.05) with interobservers difference of 1.9+/-1.5cm, respectively. Left atrial dimension increased from 43.5+/-6.6 to 46.2+/-6.1mm(p<0.005). Transmitral inflow revealed norrnal E/A ratio and deceleration time of 150~ 40msec in 11 patients with changed to relaxation abnormalities in three and pseudonormalization in ovo and relaxation abnormalities in 14 patients with changed to pseudonormalization in three at follow-up. CONCLUSIONS: Patients with apical hypertrophic cardiomyopathy have relatively favorable prognosis during follow up period without any significant clinical event and symptomatic deterioration. T wave negativity on EKG and left atrial dimension on echocardiographic examination were increased during follow up, but these parameters were not associated with clinical presentation.