Successive measurements of cardiac output by external monitoring using digital counter and automatic digital printer.

The selection of a calibration time for an external radioisotope determination of cardiac output is discussed with respect to obtaining values which agreed well with those of direct arterial sampling technique. Placement of external detector was also examined using 2 scintillation head with different collimators and focusing angulations simultaneously. External cardiac output demonstrated higher value by conventional 10 minute calibration method than 5 to 3 minute ones, and the values calibrated at 5 minute after RISA injection were in most reasonable agreement with those of direct value, and the authors recommended the left cardiac apex monitoring with 5 minute calibration as the standard method. Examples of successive determination of cardiac output before and aftere amino-