[Evaluation of cardiac function by external polygraphic recordings. Comparison with angiography].
Good correlations have been reported between angiographic ejection fraction and indices of left ventricular function obtained by external polygraphic recordings. We studied 104 coronary or normal patients undergoing angiography within 24 hours of external polygraphic recordings. The angiographic ejection fraction was compared with three external indices in each case: the Weissler index (PEP/ET), the normalised derivation of a calibrated apex cardiogram (ds/dt/s) and the ejection fraction calculated from the apex cardiogram (EF apex). The angiographic ejection fraction was calculated after measuring left ventricular end diastolic and end systolic volumes in the 30 degrees RAO projection by a method derived from Dodge's. No correlation was found between the angiographic ejection fraction and any of the external indices. Analysis of our results and of those previously reported lead us to the following conclusions: --systolic time intervals are very sensitive to stress, imposing recording conditions which are difficult to meet in hospital surroundings, --a good quality apex cardiogram can only be obtained in a small percentage of patients, --the apex cardiogram reflects a mechanical phenomenon due to displacement of the apex beat and cannot therefore be assimilated to changes in cardiac volume, --the ds/dt/s index is difficult to calculate without a sophisticated computer. Therefore, these methods of external recording are not suitable for routine medical practice.