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[Calculation of the ejection fraction from simultaneously recorded systolic intervals and angiography. Comparative
Abstract:
Garrard, Weissler and Dodge have reported a close correlation (r = -0,90) between angiographic ejection fractions (EF) and the ratio of left ventricular preejection and ejection periods (PEP/LVET) in patients with left ventricular disease without simultaneous recording equation Y" = 1,25 - 1,25 x where x is the PEP/LVET ratio and Y" the ejection fraction. Using this formula a theoretical EF may be calculated when the PEP/LVET ratio is known. A number of precautions must be taken in measuring systolic time intervals (synchronous recordings, rapid and constant recording speeds of at least 100 mm/s, good quality tracings). Respecting these conditions, close correlations between the theoretical and angiographic EF were obtained. However, discrepancies were observed in some cases and so the relationship was examined with and without simultaneous recordings in 28 patients (19 with coronary artery disease). The equations obtained were Y = 1,2 - 1,51 x and Y = 1,04 - 1,04 x respectively. The correlations in the whole group and in the coronary subgroup were not as good when the recording was not simultaneous (r = -0,78, compared to r = -0,85). The theoretic EF appeared to be "optimised" under these conditions. The "optimisation" increased with increasing values of the PEP/LVET ratio. A downward correction had to be made for abnormally high values (for example for a PEP/LVET of 0,38, the EF had to be corrected by -3,1% and for a value of 0,50 by -10,5%). This was also applicable in the patients with coronary artery disease. Curiously, the equation relating simultaneous EF and PEP/LVET was very close to that obtained by Garrard (Ya = 1, 12 - 1,27 x, ra = -0,80). The theoretical EF calculated from this equation was very close to the angiographic value. However, it was slightly higher or lower in coronary patients with or without myocardial infarction. Garrard's equation would appear to be useful for repeated studies of the ejection fraction in these patients.