EFFECT OF LIDOCAINE ON LEFT-VENTRICULAR PRESSURE-VOLUME CURVES DURINGDEMAND ISCHEMIA IN PIGS

The diastolic pressure-volume curve shifts upward during demand ischem ia, most likely because of changes in Ca2+ dynamics within the sarcome re. It is possible that agents that affect Na+/Ca2+ exchange, such as Lidocaine, a class Ib-type Na+-channel blocker that decreases intracel lular Na+, could affect the diastolic pressure-volume relationship bec ause of indirect effects on intracellular Ca2+. Lidocaine is a drug wi dely used to treat arrhythmias in patients with myocardial ischemia. W e studied the effects of Lidocaine on diastolic dysfunction associated with demand ischemia. We compared diastolic las represented by the sh ift in the diastolic pressure-volume relationship) and systolic functi on during demand ischemia before and after lidocaine injection. We cre ated demand ischemia in pigs before and after administering lidocaine (5 mg/kg) in eight open-pericardium anesthetized pigs. Demand ischemia was induced by constricting the left anterior descending coronary art ery and then pacing at 1.5-1.8 times the baseline heart rate for 1.5-3 min. Hemodynamics were recorded during baseline, demand ischemia, bas eline after lidocaine injection, and demand ischemia after Lidocaine. Lidocaine did not affect systolic function or the time constant of iso volumic relaxation, but it increased the upward shift of the diastolic pressure-volume curve during demand ischemia compared with the increa se that occurred before Lidocaine was administered. This result sugges ts that lidocaine could aggravate diastolic dysfunction in patients wi th ischemic heart disease.