Idiopathic hypertrophic subaortic stenosis.

The clinical and laboratory findings in 29 patients with idiopathic hypertrophic subaortic stenosis are presented. Dyspnoea during exercise, angina pectoris, syncope combined with left ventricular hyperthrophy on ECG and chest X-ray and a systolic ejection murmur at the apex and the left sternal border are the most important findings. The findings were different in patients below and above 30 years of age. Most of the patients below 30 were in function group I, had a normal heart volume on chest X-+ray, and syncope was related to exercise. All patients above 30 had symptoms, nearly all were in function groups II-IV and often complained of palpitations, had increased heart volume on chest X-ray, sign of enlarged left atrium or atrial fibrillation of ECG. Syncope was not related to exercise, but always associated with palpitation in patients above 35 years of age. Pathologic Q waves were found more often in the younger age group. The differential diagnosis is discussed in relation to fixed aortic stenosis, mitral valve disease, ventricular septal defect, coronary artery disease, and hypertrophic cardiomyopathy without outflow tract obstruction.