Left atrial overload: A hemodynamic, echocardiographic, electrocardiographic and vectorcardiographic study

Abstract

Combining electrocardiography with current techniques for continuous bedside hemodynamic monitoring and echocardiography permits analysis of P wave morphology in light of concurrent and accurate measurements of left atrial pressure and chamber size. In order to determine a noninvasive means of estimating left ventricular filling pressure during changing hemodynamics, and to evaluate contributions of left atrial size and pressure to P-wave morphology, 144 pulmonary capillary wedge pressures (PCW, mm. Hg) with 12-lead electrocardiograms, vectorcardiograms, and left atrial echocardiograms were obtained in 61 cardiac care patients.Noninvasive predictors of the PCW were sought initially and after changes in the PCW. Three electrocardiographic and seven vectorcardiographic P-wave indices and three echocardiographic left atrial dimension indices were evaluated. This study found that the P-terminal negativity, PTF V1, (abnormal defined as greater than −.30 mm.-sec. negativity) was the best electrocardiographic predictor of PCW; PTF V1 correlated moderately well with PCW (r = .67, P < .01) and was the best separator of patients with PCW ≤ 14 mm. Hg from those with PCW > 14 (sensitivity 86 per cent and specificity 79 per cent). Despite the lack of a high correlation, PTF V1 was helpful in that a normal PTF V1 excluded patients with PCW pressures in the pulmonary edema range (PCW > 24 mm. Hg). No patient with PCW > 24 had a normal PTF V1. Similarly, presence of an abnormal PTF V1 excluded patients with low left ventricular filling pressures (PCW < 10 mm. Hg). Neither P-terminal positivity in orthogonal lead z nor a multiple coefficient regression program of computer measured vectorcardiographic parameters was superior to other individual electrocardiographic and vectorcardiographic measurements in theri correlation with PCW. Despite the widespread use of PTF V1 for the electrocardiographic diagnosis of left atrial enlargement, echocardiographic left atrial dimension showed a significant but low correlation with PTF V1 (r = .49), suggesting that atrial size is a weaker determinant of PTF V1 than atrial hypertension. Left atrial wall tension, expressed as the product of PCW pressure and left atrial dimension, also showed a moderate though better correlation (r = .72) with PTF V1 than did PCW pressure or left atrial dimension individually. Conclusions of this study are that additional factors are importantly related to the ECG pattern of left atrial overload. This conclusion is supported by the rather modest correlation coefficient between PTF V1 and PCW pressure initially and an important second finding that in 51 patients studied serially, simultaneous changes in the electrocardiogram, vectorcardiogram, and left atrial dimension were unreliable predictors of acute changes in PCW pressure.The study design utilized offers potential for testing and improving current electrocardiographic criteria and the results obtained caution against inferences made about hemodynamics and cardiac anatomy from the electrocardiogram, particularly when non-dynamic comparisons between the electrocardiogram and these functions are made.