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

Thesympathetic nervous system hasanimportant effect onthestrength ofmyocardial contraction whichismediated through beta-adrenergic receptors (Ahlquist, 1948), andtheadministration ofa selective beta-adrenergic blocking agentsuchas propranolol mightbeexpected toreducemyocardial contractility inpatients whohavea high sympathetic tone.Thereisevidence thatpatients inheart failure haveincreased activity ofthesympathetic nervous system(Braunwald andChidsey, 1965), whichmayactasacompensatory mechanism, increasing thestrength ofmyocardial contraction andallowing thestroke output tobemaintained ata lowerdiastolic pressure thanwouldotherwise be possible. Underthese circumstances beta-adrenergic blockade might beexpected tohaveadeleteriouseffect on myocardial performance. Infact thedevelopment ofcardiac failure isarecognized hazard oftreatment withbeta-adrenergic blocking drugs(Braunwald andChidsey, 1965). These agents arenowbeing usedextensively inischaemic andhypertensive heartdisease, andreports have appeared oftheir value inreducing theseverity of angina pectoris (Apthorp, Chamberlain, andHayward,1964), oftheir useinmyocardial infarction (Snow, 1965), andoftheir hypotensive effect in systemic hypertension (Prichard and Gillam, 1964).Thepossibility thatcardiac failure might beproduced inpatients withserious heart disease hasnecessarily restricted theuseofbeta-adrenergic blocking drugs inthese conditions. Inthis study anattempt hasbeenmadetoassess thechanges indiastolic toneoftheleft ventricle produced by beta-adrenergic blockade, sothat patients likely tosuffer fromleft ventricular failure after propranolol canbedistinguished fromthose whowill tolerate this treatment without difficulty. Thediastolic properties oftheleft ventricle have