Drug-induced changes in blood flow in the acutely ischaemic canine myocardium; relationship to subendocardial driving pressure

SUMMARY 1. The effects of various drugs have been studied on blood flow and oxygen handling (availability, extraction and consumption) in both normal and acutely ischaemic regions of the canine myocardium. Ischaemia was produced by the acute ligation of the anterior descending branch of the left coronary artery.
2. Lidoflazine, like other coronary vasodilator drugs, increases blood flow in the normal myocardium, but does not increase flow through the ischaemic region. Drugs of this type may, in addition, open up 'shunt' vessels within the ischaemic region.
3. Of three cardiac stimulants studied, only oxyfedrine consistently increases blood flow through the ischaemic region; isoprenaline and glucagon do not.
4. Noradrenaline causes marked increases in flow through the ischaemic region: its effect is associated with an increase in coronary pressure in the artery distal to the ligature.
5. Evidence is put forward that the critical factor determining flow through ischaemic regions of the myocardium is the transventricular driving pressure. When the effects of various drugs on flow and driving pressure are analysed and compared, the only drugs that increase flow in an ischaemic region are those that increase the pressure gradient across the wall of the left ventricle.