Noninvasive beat to beat monitoring of left ventricular function by a nonimaging nuclear detector during premature ventricular contractions

A specially designed cardiac probe was used to evaluate beat to beat changes in left ventricular performance caused by premature ventricular contractions in four open chest dogs and 15 patients with various cardiac disorders. After intravenous injection of 15 to 20 mCi of technetium-99m serum albumin, left ventricular time-activity curves were obtained by positioning the probe over the left ventricular area in a 40 ° lateral anterior oblique projection with a 10 to 20 ° caudad tilt. Correct positioning was found by maximizing both the stroke counts and the end-diastolic counts. In the animal experiments, data generated by the probe were displayed side by side with left ventricular pressure, aortic pressure and aortic flow. Increases or decreases in stroke volume measured with the flowmeter correlated well with those measured with the cardiac probe. In the patients, the relative standard deviation of filling volumes, stroke volumes and ejection fractions of the sinus beats was 16 ± 5 percent, 14 ± 5 percent and 12 ± 5 percent, respectively. The premature ventricular contractions manifested end-systolic volume greater than, equal to or less than that of sinus beats. The filling volume, stroke volume and ejection fraction of these contractions were 51 ± 21 percent, 57 ± 17 percent and 45 ± 19 percent lower, respectively, than those of the sinus beats. In the compensatory sinus beats stroke volume and ejection fraction were 20 ± 27 percent and 26 ± 12 percent higher, respectively, than those in the sinus beats; however, the filling volume of these beats was essentially equal to that of the sinus beats.