Determination of ventricular volume by radioisotope-angiography

Directly determined ventricular volumes, free of hemodynamic changes induced by radiopaque media, were obtained by cardiac visualization after radioisotope injection in eight studies in 4 open chest dogs. Six mcurie of technetium-99m in 3 cc. of saline were injected into the left ventricle. Two biplane images were recorded with the Anger scintillation camera and stored on videomagnetic tape. Reference standards were used to correct for distortion and magnification. Gating of the video signal using the electrocardiogram allowed selection of both end-diastolic and end-systolic volumes. Dextran was infused to increase end-diastolic volume and pressure, and a second pair of biplane images was obtained. End-diastolic volume, calculated from the images by the method of longest measured length, was then compared with end-diastolic volume determined from left ventricular pressure-volume curves. Excellent agreement of the ratio of preto postinfusion end-diastolic volume was obtained between these two methods: 0.61 (range 0.51 to 0.65) by the isotope technic and 0.61 (range 0.59 to 0.62) by the pressure-volume curves. Control end-diastolic volume averaged 25.2 cc. by the isotope method and 30 cc. by the pressure-volume curve; postinfusion volumes averaged 41.9 and 49.0 cc., respectively. The ratio of end-systolic volume to end-diastolic volume was 0.67 in the preinfusion studies and 0.64 in the postinfusion studies. Thus, direct isotope visualization of the heart, which does not disturb circulatory function, may provide a useful and safe means for serial study of ventricular volume changes.