REGIONAL MYOCARDIAL-FUNCTION DURING CONTIGUOUS ISCHEMIA IN AN ANESTHETIZED CANINE MODEL - COMPARISON OF 6 METHODS OF MEASUREMENT

During acute myocardial ischaemia, the function of the unaffected musc le is the primary determinant of residual cardiac performance. We comp ared six methods of measuring regional function in the remaining non-i schaemic segment after acute ligation of the left anterior descending (LAD) coronary artery in 16 dogs. Preparation included left ventricula r micromanometers, regional sonomicrometer transducers to measure segm ent length and wall thickness, caval occluders and left atrial cathete rs for injection of radioactive microspheres to measure regional blood flow. Pulmonary artery, central venous and systemic arterial pressure s were measured and regional coronary venous blood was collected for d irect myocardial oxygen consumption (Vo(2)) calculations. Under basal high-dose fentanyl-neuromuscular blocker anaesthesia, the LAD was occl uded after addition of halothane or isoflurane at 0.5 or 1.5 MAC conce ntrations. Regional myocardial function of the non-ischaemic segment w as assessed by the following computer derived indices: percent systoli c wall thickening (% WT), velocity of shortening (v(s)), percent systo lic shortening (% SS), regional stroke work (RSW), regional preload re cruitable stroke work (RPRSW) and regional end-systolic elastance (Ees ). No index demonstrated enhanced function in the nonischaemic segment after LAD ligation and all monitors, except Ees, were sensitive to de pression of function represented by a decrease in values after adminis tration of halothane and isoflurane (P < 0.05). Ees values increased w ith the addition of isoflurane and remained constant with halothane. C irculating concentrations of catecholamines were unchanged after ischa emia, while inhalation agents caused a decrease in the concentrations of adrenaline and dopamine (P < 0.05), but not noradrenaline. Overall, % WT, obtained without complex derivations, monitored regional functi on well, correlated most closely with load-independent RPRSW and portr ayed the lack of augmented function in the normal segment. Ees appeare d inconsistent, and consequently unreliable, as an index of regional f unction.