Objectives: This study was conducted to test the hypothesis that the time-voltage integral of the QRS complex can improve the electrocardiographic (ECG) identification of left ventricular hypertrophy.
Background: Standard ECG criteria have exhibited poor sensitivity for left ventricular hypertrophy at acceptable levels of specificity. However, left ventricular mass may be more closely related to the time-voltage integral of the summed left ventricular dipole than to QRS duration or voltages used in standard ECG criteria.
Methods: Standard 12-lead ECGs, orthogonal lead signal-averaged ECGs and echocardiograms were obtained in 62 male control subjects without left ventricular hypertrophy and 51 men with left ventricular hypertrophy defined by echocardiographic criteria (indexed left ventricular mass > 125 g/m2). Voltage of the QRS complex was integrated over the total QRS duration in leads X, Y and Z to calculate the time-voltage integral of each orthogonal lead, of the maximal spatial vector complex and of the horizontal, frontal and sagittal plane vector complexes.
Results: At matched specificity of 99%, the 73% (37 of 51) sensitivity of the time-voltage integral of the vector QRS complex in the horizontal plane was significantly greater than the 10% sensitivity of the Romhilt-Estes point score, the 16% sensitivity of QRS duration alone, the 22% sensitivity of Cornell voltage, the 33% sensitivity of the 12-lead sum of QRS voltage and the 37% sensitivity of Sokolow-Lyon voltage (each p < 0.001). Sensitivity of the horizontal plane time-voltage integral was also greater than the 10% to 51% sensitivity of the time-voltage integral calculated in the individual X, Y or Z leads (p < 0.01 to < 0.001), the 18% and 35% sensitivity of the time-voltage integrals of the frontal and sagittal plane vectors (p < 0.001) and the 49% sensitivity of the time-voltage integral of the maximal spatial vector complex calculated from all three orthogonal leads (p < 0.001). Comparison of receiver operating characteristic curves confirmed that the superior performance of the horizontal plane time-voltage integral relative to standard and other signal-averaged criteria was independent of partition value selection.
Conclusions: These findings suggest that use of the time-voltage integral of the QRS complex, a method that can be readily implemented on commercially available computerized ECG systems, can improve the accuracy of ECG methods for the identification of left ventricular hypertrophy.