Reflex cardiovascular response to acute myocardial ischaemia

The usual cardiovascular response to acute myocardial ischaemia is either pressor, characterised by tachycardia and hypertension or depressor, manifested by bradycardia, hypotension and systemic vasodilatation. We studied the incidence of ectopic arrhythmias, the changes in heart rate, in left ventricular pressure and dP/dt and the changes in plasma level of free fatty acids. Acute anterior ischaemia increased the heart rate, left ventricular dP/dtmax and plasma level of free fatty acids and developed frequent ventricular ectopic arrhythmias. Previous injection of propranolol prevented the elevation of plasma free fatty acids. Acute inferior ischaemia produced a slight decrease in heart rate, no change in plasma level of free fatty acids and a significant decrease in left ventricular dP/dtmax. The experimental model allowed us to study the response to acute myocardial ischaemia in conscious dogs; the results obtained point to a preferential location of the pressor and depressor receptors respectively to the anterior and inferior surfaces of the left ventricle.