Estimation of the compliance of the human capacitance vessels using radionuclide plethysmography

Radionuclide (RN) plethysmography with Tc-99m RBC was performed in 32 patients with heart disease with the purpose of obtaining compliance of human capacitance vessels. When equilibrium was achieved, RN counts of the region of interest and venous pressure in the forearm were sequentially recorded when the vein of the upper arm was occluded with a cuff inflator. Based on the RN count-venous pressure curve, the specific compliance of the forearm vein and compliance of systemic venous system (SVS) were estimated. In the group of the NYHA functional classification I, which is recognized as hemodynamically ''normal'', the compliance of SVS was 129.8 +- 25.9 ml · mmHg-1 (mean +- SD; n = 9). In comparing the NYHA functional classification and the compliance of SVS, the compliance of SVS was significantly decreased for severer heart failure. Tongue administration of nitroglycerin (0.6 mg) significantly increased the compliance of SVS (p < 0.01). (Namekawa, K.)