Value, sensitivity and specificity of stroke volume ratio in routine equilibrium gated scintigraphy

The stroke volume ratio (SVR) is a new, non invasive method to quantify ventricular volume overload (VVO). We have analyzed its value, sensitivity and specificity in routine clinical practice. The results of 238 consecutive patients (pts) were analysed prospectively within a 3 months period. The SVR was expressed as the ratio of left ventricular (LV) stroke counts over the right ventricular (RV) stroke counts measured on the time-activity curves. One region of interest was drawn per ventricle on the phase and amplitude images. Values above 1.6 were considered as LVVO and below 0.9 as RVVO. Fifty-one patients had VVO due to valvular regurgitation or left-to-right shunt; 187 patients had no evidence of VVO. Mean value obtained for 23 normal subjects with adequate positioning was 1.27 +/- 0.14 (MV +/- SD), ranging from 0.9 to 1.47. Among patients with adequate positioning, no difference was observed in subgroups with dilated cardiopathy (DC) or anteroseptal aneurysm (AA) despite a low EF. MV for patients with LV or RV hypertrophy (H) were statistically different. Sensitivity was 82% for the 51 patients with VVO. False negatives were due to biventricular overload or mild VVO. Specificity evaluated in the 187 patients without VVO was 76%. The 45 false positives were due to poor separation of the right cardiac chambers and/or of the 2 ventricles. They were observed in 4 patients with AA, 3 patients with DC, 7 patients with LVH, 4 patients with RVH and 24 patients with inadequate positioning. No explanation was found in 3 patients. We conclude that cardiac equilibrium blood pool scintigraphy has an adequate sensitivity and specificity to evaluate patients with VVO.