Assessment of relative actions of beta-adrenergic blocking drugs on heart rate and left ventricular ejection using a non-invasive method in patients with aortic Starr-Edwards prostheses.

The relative effects on heart rate and left ventricular ejection at rest and during exercise ofM & B I7,8o3a, propranolol, and practolol were studied in the same 6 patients with Starr-Edwards aortic valve replacement. Changes in left ventricular ejection were measured phonocardiographically, an increase in ejection being associated with a reduction in the time between the R wave of the electrocardiogram and the opening sound of the prosthesis (A1). At the three selected equivalent dose levels there was no significant difference in the reduction of heart rate produced by intravenous administration of the three drugs, either at rest or on exercise. All three drugs prolonged the RA1 interval at rest and on exercise, but at the highest dose (30 mg) M & B 17,803a and practolol increased left ventricular ejection at rest, possibly due to their intrinsic sympathomimetic activity. On exercise, M & B i7,803a and practolol were not statistically distinguishable, and both produced significantly less reduction in left ventricular ejection than the equivalent doses of propranolol. It is concluded that intravenous administration ofM & B I7,8o3a in the same doses as practolol produces a similar effect on heart rate and left ventricular ejection. It is also concluded that there is nofixed relation between changes in heart rate and left ventricular ejection, at rest or during exercise, after the administration of beta-adrenergic receptor blocking agents.