Beta-blocker therapy for dynamic left ventricular outflow tract obstruction induced by exercise

In patients who present with angina, dynamic left ventricular outflow tract obstruction may be responsible of symptoms. The aim of our study was to evaluate the effect of negative inotropic therapy on ventricular physiology and symptoms of patients with dynamic left ventricular outflow tract obstruction induced by exercise in the absence of hypertrophic cardiomyopathy.

Seventy eight patients with symptoms of angina, normal exercise SPECT test and normal resting left ventricular systolic function were prospectively analysed with exercise echocardiography. Fifteen of them developed high outflow tract velocities (greater than 2.57 m/s) on effort. After treatment with bisoprolol (mean dose 6.9+/-3.5 mg) in these patients, symptoms and dynamic left ventricular outflow tract obstruction during exercise were re-evaluated.

After negative inotropic therapy, there was a significant reduction of 86.6% in the development of intracavitary gradient (15 to 2 patients). In all patients the left ventricular outflow tract velocities decreased (2.91+/-0.4 m/s to 1.92+/-0.46 m/s, p=0.001). However, the oxygen consumption during exercise was higher (7.3+/-1.7 METs to 8.5+/-1.8 METs, p=0.005), and symptoms improved significantly following therapy, with a reduction in mean NYHA class from 1.9+/-0.5 to 1.0+/-0.0 (p=0.001).

Negative inotropic therapy may represent a beneficial therapeutic approach in selected patients with dynamic left ventricular outflow tract obstruction induced by exercise and identified during exercise echocardiography.