Comparative studies of two-dimensional echocardiographic and 12-lead ECG findings in right heart enlargement.

This thesis project was designed to evaluate certain EG criteria presently used in the diagnosis of right heart enlargement. Using a relatively new diagnostic tool, two-dimensional echocardiography as the "gold standard" in cardiac dimension sizing, 3 cases were studied. In 37 normal adults, the analysis of six two-dimensional echo parameters resulted in the following measurements of mean and standard deviation: RV area = 19.8 ± 5.1 cm2; RV area/BSA = 10.5 ± 2.5 cm2/m2; RA area = 13.4 ± 2.9 cm2; RA area/BSA = 7.1 ± 1.3 cm2/m2; RV/LV area ratio = 0.68 ± 0.14; RA/LA area ratio = 0.93 ± 0.16. From this data, a population of 36 patients was defined as having enlargement if one or more measurements exceeded these means plus two standard deviations. Following this classification, a number of parameters were measured on all cases, both normal and abnormal. Through the use of t-tests, significant differences were found between the following ECG parameters: R wave amplitude in V1-V2; S wave amplitude in V5-V6; R/S ration in V1-V2; R/S ration in V5-V6; QRS axis deflection; P wave amplitude. Linear regression analysis was then used to evaluate correlations of chamber dimensions with ECG measurements. Poor correlation was found with 0.0 < r < 0.52. To increase the predictive value of the ECG measurements, a multivariate discriminant analysis was performed which resulted in a 60% sensitivity and 90% specificity using the following ECG parameters; R wave in V1-V2; S wave in V5-V6; R/S ratio in V1/V2; QRS axis. The resulting discriminant function was: Y = 0.02(X1) + 0.074(X2) + 0.006(X3) + 0.0006(X4) - 0.48, where X1 to X4 are the above respective parameter measurements. Subjects with Y > .511 were then classified as having right heart enlargement with the confidence range previously mentioned. From this project, it has been shown that multivariate ECG analysis is a potentially powerful technique for diagnosing right heart enlargement. Furthermore, through the use of 2-D echocardiography, the potential now exists for the rapid collection of large data bases of previously difficult to obtain cardiac structural information.