Assessment of left ventricular function by radionuclide angiography during induced supraventricular tachycardia

Electrocardiographically synchronized radionuclide angiography was performed before, during and after induced paroxysmal Supraventricular tachycardia in 13 patients. Data were acquired with a computer-interfaced Anger camera in a left anterior oblique projection. No data were acquired during tachycardia until tachycardia had been sustained for 1 minute. Patients ranged in age from 20 to 64 years (mean ± standard deviation 42 ± 14.5). Three patients had organic heart disease and 10 did not. Baseline and tachycardia heart rates (beats/min) were 59 to 99 (73 ± 11) versus 141 to 228 (157 ± 22). Baseline and tachycardia left ventricular measurements (mean ± standard error) were as follows: ejection fraction 64 ± 2 versus 62 ± 4 percent (not significant), ejection rate 3.0 ± 0.1 versus 4.3 ± 0.4 mean ventricular counts/s (p < 0.001), normalized end-diastolic counts 72.7 ± 7.8 versus 48.7 ± 6.7 × 10³ counts (p < 0.001), normalized stroke counts 37.1 ± 3.4 versus 23.3 ± 2.7 × 10³ counts (p < 0.001) and normalized count cardiac output 2,717.5 ± 273.0 versus 3,620.2 ± 403.7 × 10³ counts/min (p < 0.005). Although ejection fraction for the whole group did not change significantly, it decreased during tachycardia by 5 percentage points or more in five patients. These were the three patients with heart disease and the two normal patients with the fastest heart rate during tachycardia (228 and 214 beats/min, respectively).In summary, paroxysmal Supraventricular tachycardia was characterized by a marked decrease in left ventricular end-diastolic and stroke volumes but increased ejection rate and cardiac output without significant change in ejection fraction. Heart disease or rapid heart rate during tachycardia appeared to have a deleterious effect on ejection fraction.