The antianginal effect of b-blockers may be attributed to which one of the following

The beneficial effects of b-blocking agents are related to their hemodynamic effects--decreased hea rate, blood pressure, and contractility--which decrease myocardial oxygen requirements at rest and during exercise. Lower hea rate is also associated with an increase in diastolic perfusion time that may increase coronary perfusion. Undesirable effects of b-blocking agents in angina include an increase in end-diastolic volume and an increase in ejection time, both of which tend to increase myocardial oxygen requirement. Ref: Katzung 13e pg:203