Effect of propranolol on left atrial systole in ischaemic and hypertensive heart disease.

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Abstract
The effect of sympathetic blockade on the abnormally large presystolic thrust in the apex cardiogram was studied in 16 patients with ischemic and hypertensive heart disease. There was a marked reduction in the presystolic wave after intravenous propranolol in all 10 patients with no left ventricular failure. Four of the 6 patients with clinical evidence of left ventricular failure had larger presystolic waves after propranolol. Possible mechanisms are considered. A change in left ventricular distensibility is thought unlikely, and the effect of an increase in ventricular volume related to the slowing of the heart is not sufficient to account for the changes. A reduction in left atrial contractility is probably responsible for the reduced presystolic thrust in patients with no left ventricular failure. The increased thrust noted in patients with left ventricular failure may be due to the Starling response to a rise of left atrial pressure. The therapeutic implications of these findings are discussed.