RADIONUCLIDE VENTRICULOGRAPHY IN THE EVAL UATION OF LEFT-VENTRICULAR MYOCARDIAL-CONTRACTILITY IN PACEMAKER-IMPLANTED PATIENTS

An EKC-500 pacmaker was implanted in 16 patients with coronary heart d isease (CHD) and 14 idiopathic conduction disturbance for complete atr ioventricular block. After surgery, the patients underwent equilibrium radionuclide ventriculography by using a nuclear stethoscope at rest and during exercise at different stimulation rates with the aim of cho osing their optimal values. It was established that patients with idio pathic conduction disturbances showed improved left ventricular contra ctility at all stimulation rates and their optimal values ranged 60-70 per minute. In patients with CHD, the stimulation rate of 60 impulses /min was optimal at rest, and with this, exercise resulted in a signif icant deterioration of myocardial contractility, but only the stimulat ion rate of 80 impulses/min led to a slight improvement, which was due to accessory mechanisms of contractility enhancement. The peak ejecti on rate was the most sensitive to progressive myocardial dysfunction, yet the basic contractility index was the mean ejection rate.