CONTINUOUS ONLINE MONITORING OF LEFT-VENTRICULAR FUNCTION WITH A NEW NONIMAGING DETECTOR - VALIDATION AND CLINICAL USE IN THE EVALUATION OF PATIENTS POST ANGIOPLASTY

A new miniaturized nonimaging radionuclide detector (Cardioscint, Oxford, England) was evaluated for the continuous on-line assessment of left ventricular function. This cesium iodide probe can be placed on the patient's chest and can be interfaced to an IBM compatible personal computer conveniently placed at the patient's bedside. This system can provide a beat-to-beat or gated determination of left ventricular ejection fraction and ST segment analysis. In 28 patients this miniaturized probe was correlated against a high resolution gamma camera study. Over a wide range of ejection fraction (31% to 76%) in patients with and without regional wall motion abnormalities, the correlation between the Cardioscint detector and the gamma camera was excellent (r = 0.94, SEE +/- 2.1). This detector system has high temporal (10 msec) resolution, and comparison of peak filling rate (PFR) and time to peak filling (TPFR) also showed close agreement with the gamma camera (PFR, r = 0.94, SEE +/- 0.17; TPFR, r = 0.92, SEE +/- 6.8). In 18 patients on bed rest the long-term stability of this system for measuring ejection fraction and ST segments was verified. During the monitoring period (108 +/- 28 minutes) only minor changes in ejection fraction occurred (coefficient of variation 0.035 +/- 0.016) and ST segment analysis showed no significant change from baseline. To determine whether continuous on-line measurement of ejection fraction would be useful after coronary angioplasty, 12 patients who had undergone a successful procedure were evaluated for 280 +/- 35 minutes with the Cardioscint system. While the majority of patients showed no significant changes in ejection fraction or ST segments, four patients demonstrated substantial changes in ejection fraction. In two of these patients there was significant improvement in left ventricular function that occurred early after angioplasty and correlated with radionuclide angiograms at follow-up. One patient had two episodes of transient ischemia assessed by ejection fraction monitoring, one with and one without symptoms suggesting coronary spasm. The fourth patient demonstrated improvement in ejection fraction that over the course of the monitoring period returned to baseline with worsening ST segments. On follow-up angiogram the patient had an occlusion of the vessel that was dilated. The miniaturized detector system can be used to provide an accurate on-line continuous assessment of left ventricular ejection fraction. Particularly in the unstable cardiac patient, this system may be useful in monitoring therapy and in determining the effects of acute interventions.