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Left ventricular volumes were determined sequentially in 31 dogs and simultaneously in 12 by biplane angiocardiography and a dye-dilution, thermal washout technique. The mean ejected fraction (SV/EDV; systolic volume/end diastolic volume) was significantly higher when measured by angiocardiography (.53 ± .03) than by the washout method (.27 ± .02). The end diastolic volume measured by angiocardiography was lower, 21.1 ± 1.5 ml/10 kg versus 34.4 ± 3.6, as was the end systolic volume, 11.3 ± 1.3 ml/10 kg versus 25.5 ± 3.2. Mean stroke volume by angiocardiography was 10.9 ml/10 kg, or 1.8 ml greater than by dye dilution (the average amount of contrast material injected per beat was 1.9 ml/10 kg). No difference was found between the washout fractions calculated from early and from late beats. There was a significant inverse correlation between the observed heart rate and washout SV/EDV. There was no correlation between heart rates and the discrepancy in measuring the various volumes. Technical difficulties and theoretical considerations are discussed and it is concluded that in dogs the angiographic method gives more accurate calculations of end diastolic and end systolic volumes than the washout technique. The latter method appears to underestimate SV/EDV systematically, probably because of incomplete mixing of indicator in the ventricle. This leads to falsely high values for EDV and ESV.

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