Hypertrophic cardiomyopathy: Is a left ventricular outflow tract gradient a major prognostic determinant?

The relationship of left ventricular outflow tract gradient as well as of clinical, ECG and haemodynamic data to presenting features and prognosis was evaluated in 125 consecutive patients with hypertropic cardiomyopathy, 79 men and 46 women (mean age: 34 +/- 7 years) studied between January 1970 and December 1985. Most clinical, ECG and haemodynamic findings were similar in the 44 patients (35%) with a pressure gradient (greater than or equal to 30 mmHg) and in the 81 patients (65%) without. Those with obstruction had greater ECG voltage SV1 and RV5; however, higher grade ventricular arrhythmias were more common in patients without obstruction. During a mean follow-up period of 7.6 +/- 4.5 years (range 2-18 years), death from a cardiac cause occurred in 28 patients (21 died suddenly) and was significantly less common in patients with a pressure gradient than in those without (11% vs 28%, P = 0.039). Univariate analysis of survival curves showed that the most powerful predictors of a poor prognosis were ejection fraction P = 0.0001), mean pulmonary artery pressure (P = 0.0001), dyspnoea (P = 0.001), left ventricular end-diastolic pressure (P = 0.002), complex ventricular arrhythmias (P = 0.029) and severe mitral regurgitation (P = 0.037). Using multivariate analysis, a decreased ejection fraction (P = 0.006) and a raised mean pulmonary artery pressure (P = 0.022) were the only independent prognostic determinants. Thus, the presence of a left ventricular outflow tract gradient does not seem of adverse prognostic significance. Risk factor characterization in patients with hypertrophic cardiomyopathy may be improved by assessment of ventricular arrhythmias in the context of left ventricular function.