Assessment of regurgitant fraction and right and left ventricular function at rest and during exercise: a new technique for determination of right ventricular stroke counts from gated equilibrium blood pool studies.

Calculation of accurate stroke count ratios for the assessment of valvular regurgitation from equilibrium blood pool images has been difficult and did not permit computation of regurgitant fractions (RF) because of contamination of right ventricular (RV) stroke counts by right atrial activity. We describe a new approach to correct for this contamination by subtracting one half of the right atrial counts from the RV counts, assuming that in the standard or "modified" left anterior oblique projection commonly used about one half of the right atrial activity is superimposed to the RV. This new method was tested in 20 patients without valvular disease or shunts. Left ventricular (LV) to RV stroke count ratio approached unity (1.01 +/- 0.14). RV ejection fractions (EF) derived by this technique agreed well with those obtained by gated first-pass studies recorded in the right anterior oblique projection. In 9 normals and 17 patients with moderate severe or severe aortic (12 patients or mitral (7 patients) regurgitation, LVEF, RVEF, and RF were determined at rest and maximum exercise. In patients at rest, LVEF (56.0 +/- 6.4%) and RVEF (49.0 +/- 7.3%) did not differ significantly from LVEF (59.6 +/- 4.2%) and RVEF (52.5 +/- 6.4%) in normals. The calculated RF was negligible in normals (1.9 +/- 8.6%), but averaged 51.8 +/- 9.8% in patients with valvular disease. During exercise, LVEF fell significantly (p less than 0.001) to 44.1 +/- 7.2% in patients but increased to 70.5 +/- 3.8% in normals. RVEF increased in aortic regurgitation to 64.5 +/- 9.8% (NS to normals) but fell in mitral regurgitation to 36.6 +/- 5.9% (p greater than 0.001). In both patient subsets RF decreased with exercise to 25.4 +/- 15.0% in aortic and 39.1 +/- 12.7% in mitral regurgitation. The results indicate that this new approach permits assessment of RVEF and RF from gated equilibrium blood pool studies and is suitable to evaluate the hemodynamic response to physiologic and therapeutic interventions in patients with valvular regurgitation.