PubMed · 4783370
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A Caspi, A Eliras. 1973-12-02. [Editorial: Bundle-branch blocks].. https://pubmed.ncbi.nlm.nih.gov/4783370/
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This report describes a patient with tachycardia-dependent left bundle branch block (LBBB) and atrial extrasystoles, some of which were followed by an unexpectedly narrow QRS complex. His-bundle recordings and premature atrial stimulation were performed to analyze the mechanism underlying the normalized intraventricular conduction of some of the early atrial impulses. The results suggested the presence of supernormal conduction in the left bundle branch (LBB), because: (1) the HV interval was identical in LBBB complexes and in early narrow QRS complexes; (2) during single test stimulation using different paced atrial cycle lengths, there was a well-defined range of H1H2 intervals resulting in normalization of intraventricular conduction; and (3) atrial pacing with a cycle length of 500 msec resulted in alternation between wide and narrow QRS complexes. These findings rule out alternative mechanisms that could explain the unexpectedly normal intraventricular conduction of early impulses.
OBJECTIVES: The object of this study was to assess the hypothesis that the product of QRS voltage and duration, as an approximation of the time-voltage integral of the QRS complex, can improve the electrocardiographic (ECG) identification of left ventricular hypertrophy. BACKGROUND: Electrocardiographic identification of left ventricular hypertrophy has been limited by the poor sensitivity of standard voltage criteria. However, increases in left ventricular mass can be more closely related to increases in the time-voltage integral of the summed left ventricular dipole than to changes in voltage or QRS duration alone. METHODS: Antemortem ECGs were compared with left ventricular mass at autopsy in 220 patients. There were 95 patients with left ventricular hypertrophy, defined by left ventricular mass index > 118 g/m2 in men and > 104 g/m2 in women. The voltage-duration product was calculated as the product of QRS duration and Cornell voltage (Cornell product) and the 12-lead sum of QRS voltage (12-lead product). RESULTS: At partitions with a matched specificity of 95%, each voltage-duration product significantly improved sensitivity for the detection of left ventricular hypertrophy when compared with simple voltage criteria alone (Cornell product 51% [48 of 95] vs. Cornell voltage 36% [34 of 95], p < 0.005 and 12-lead product 45% [43 of 95] vs. 12-lead voltage 31% [30 of 95], p < 0.001). Sensitivity of both the Cornell product and 12-lead product was significantly greater than that found for QRS duration alone (28%, 27 of 95, p < 0.005) and the Romhilt-Estes point score (27%, 26 of 95, p < 0.005), and compared favorably with the sensitivity of the complex Cornell multivariate score (44%, 42 of 95, p = NS). Comparison of receiver operating characteristic curves demonstrated that improved performance of the voltage-duration products for the detection of left ventricular hypertrophy was independent of test partition selection. In addition, test performance of the voltage-duration products was not significantly affected by the presence or absence of a bundle branch block. CONCLUSIONS: These data suggest that the simple product of either Cornell or 12-lead voltage and QRS duration can identify left ventricular hypertrophy more accurately than can voltage or QRS duration criteria alone and may approach or exceed the performance of more complex multiple regression analyses.