A decrease in left ventricular volume increases the severity of left ventricular outflow tract obstruction in patients with obstructive hypertrophic cardiomyopathy, formerly called idiopathic hypertrophic subaortic stenosis. Because of this, a musician with the condition develops dizziness playing his saxophone which requires repeated and prolonged Valsalva maneuvers.
A 50-year-old man, a professional musician, complains of dizziness when playing the saxophone. The symptom gradually has been growing worse and is interfering with his work. His pulse is 60 beats/minute, and his blood pressure is 155/80 mm Hg. His carotid pulses are brisk, and a prominent left ventricular (LV) impulse is felt in the left anterior axillary line. A grade 3/6 systolic murmur is heard over the entire precordium and is loudest at the lower left sternal border; it increases in intensity during a Valsalva maneuver. These findings indicate obstructive hypertrophic cardiomyopathy (HC).
The electrocardiogram (ECG) shows striking LV hypertrophy with huge QRS voltage (the precordial leads are recorded at 1/2 standard), borderline long QRS duration (0.105 s), and typical repolarization changes (a depressed J point and a downsloping ST segment into an inverted T wave with a more rapidly upsloping return to baseline), the so-called strain pattern ( Figure 1 ). Similar ECG patterns have been seen with other causes of LV hypertrophy, such as severe long-standing systemic arterial hypertension, other forms of LV outflow obstruction, for example, severe valvular aortic stenosis, and chronic severe aortic regurgitation. When such spectacular changes of LV hypertrophy are seen, however, obstructive HC should immediately be considered because it most characteristically produces such changes. Total 12-lead QRS voltage >17.5 mV has been shown to be superior to other ECG criteria in detecting LV hypertrophy in patients with HC. Our patient’s total 12-lead QRS voltage is 37 mV. The good news is that large QRS voltage is negatively correlated with myocardial fibrosis, as determined by late gadolinium enhancement, in patients with HC.
