Hemodynamic changes during dipyridamole stress in patients with aortic stenosis.

Dipyridamole is a potent vasodilator used in pharmacologic stress testing. Patients with severe aortic stenosis are not suitable for exercise, and are usually not subjected to testing with vasodilator substances. The aim of the present study was to investigate hemodynamic changes during dipyridamole stress test in patients with aortic stenosis and to see if these changes where reversible by theophylline, an aminophylline derivative. Ten patients with aortic stenosis underwent right and left heart catheterization. Simultaneous recordings of cardiac output, left ventricular and aortic pressures were performed at baseline, after intravenous dipyridamole infusion (0.56 mg/kg dissolved in 250 ml of saline given over four minutes), and after intravenous theophylline injection (115 mg). There was an increase in heart rate, stroke volume and flow, and a decrease in systolic and diastolic blood pressure and in systemic vascular resistance after dipyridamole infusion. Left ventricular stroke work index and pressure time per minute increased after dipyridamole infusion suggesting an increase in myocardial oxygen demand, but there was no significant change compared to baseline after theophylline administration. Less than one third of left ventricular work was due to the resistance of the aortic valve. The aortic valve area changed with changes in flow. It is concluded that cardiac output, left ventricular work and myocardial oxygen demand after dipyridamole infusion increased in patients with aortic stenosis. The systemic vascular resistance seems to be more important determinant of cardiac output than the aortic valve obstruction. The calculated valve area appears to be flow-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)