Measurement of coronary circulation time with a catheter type micro G-M counter.

Abstract

Coronary circulation time was measured in 17 closed-chest dogs. Meas-urement was made by injecting P32 into the left ventricle, and detecting its arrival into the right ventricle with a catheter type micro G-M counter in situ. This technic was devised to exclude sources of significant error inherent to conventional dye dilution technic.Average circulation time in dogs was 2.2 (0.9-3.8) sec., and was significantly shorter than that reported in published works. Appearance of P32 in the superior and inferior vena cava through circulation took 5.0 and 4.6 sec. on average, respectively, occurring appreciably later than that in the right ventricle through circuit. The coronary dilution curve, however, could not be separated from systemic one in the right ventricle.Discussion was also made about characteristics of the micro G-M counter, and it was suggested to be useful for in vivo measurement of radioisotopes in various ways.