A new microcomputer-based ECG analysis system

Accuracy of advanced versus strictly conventional 12-lead ECG for detection and screening of coronary artery disease, left ventricular hypertrophy and left ventricular systolic dysfunction

Background

Resting conventional 12-lead ECG has low sensitivity for detection of coronary artery disease (CAD) and left ventricular hypertrophy (LVH) and low positive predictive value (PPV) for prediction of left ventricular systolic dysfunction (LVSD). We hypothesized that a ~5-min resting 12-lead advanced ECG test ("A-ECG") that combined results from both the advanced and conventional ECG could more accurately screen for these conditions than strictly conventional ECG.

Methods

Results from nearly every conventional and advanced resting ECG parameter known from the literature to have diagnostic or predictive value were first retrospectively evaluated in 418 healthy controls and 290 patients with imaging-proven CAD, LVH and/or LVSD. Each ECG parameter was examined for potential inclusion within multi-parameter A-ECG scores derived from multivariate regression models that were designed to optimally screen for disease in general or LVSD in particular. The performance of the best retrospectively-validated A-ECG scores was then compared against that of optimized pooled criteria from the strictly conventional ECG in a test set of 315 additional individuals.

Results

Compared to optimized pooled criteria from the strictly conventional ECG, a 7-parameter A-ECG score validated in the training set increased the sensitivity of resting ECG for identifying disease in the test set from 78% (72-84%) to 92% (88-96%) (P < 0.0001) while also increasing specificity from 85% (77-91%) to 94% (88-98%) (P < 0.05). In diseased patients, another 5-parameter A-ECG score increased the PPV of ECG for LVSD from 53% (41-65%) to 92% (78-98%) (P < 0.0001) without compromising related negative predictive value.

Conclusion

Resting 12-lead A-ECG scoring is more accurate than strictly conventional ECG in screening for CAD, LVH and LVSD.

The orthogonal electrocardiogram as risk indicator for the prediction of myocardial infarction and/or cardiac death

In a prospective study on Coronary Heart Disease (CHD) orthogonal electrocardiograms (Frank) were recorded annually for ten years from 1,444 asymptomatic, middle-aged males with a mean age of 57.4 +/- 10.6 years. Cases with overt or suspected CHD were excluded. The purpose of the study was to identify risk indicators in electrocardiograms and to compare them with other known risk factors used for prediction of acute CHD events such as myocardial infarction (MI) and/or cardiac death (CD). Such acute events occurred in 88 cases. Pre-event ECGs of these acute events were compared with all others without events, using logistic regression analysis. Identified ECG risk indicators were then compared with other known risk factors such as smoking, blood pressure, cholesterol, age, weight, etc. The predictive power of the ECG, derived mainly from the ST-T complex, exceeded all others by a wide margin. The amplitude of the first 1/8 of the ST-T complex in lead x (similar to V5-V6) together with relative body weight proved best when one pre-event record was available. Prediction improved when ECG changes between two pre-event recordings were included. Precision of measurements by computer appeared essential for improvements in CHD prediction.

Serial measurements of systolic time intervals during treatment with hydrochlorothiazide alone and combined with other antihypertensive agents

As part of the Veterans Administration cooperative studies on antihypertensive agents, systolic time intervals (STIs) were recorded before and after 2 or 4 weeks of treatment with hydrochlorothiazide (HCTZ) alone in 320 asymptomatic patients with mild to moderate hypertension. After treatment with HCTZ, left ventricular ejection time corrected for heart rate (delta LVET) was significantly reduced. This decrease is consistent with other hemodynamic observations indicating a reduced preload and stroke volume after administration of thiazides. Electromechanical systole corrected for heart rate (delta QS2) decreased, while the ratio of preejection period to LVET (PEP/LVET) increased, reflecting reduced left ventricular function. PEP did not change. Four step 2 drugs--hydralazine, prazosin, oxprenolol and propranolol--were then added randomly to HCTZ and further recordings of STIs were taken at 1 and 6 months after administration of these drugs. The delta LVET and delta QS2 increased and PEP/LVET decreased, suggesting improved left ventricular function after administration of all 4 agents. These changes may have been due to the added agents or to the recovery of cardiac output that occurs independently during long-term treatment with thiazide diuretic drugs alone. PEP decreased slightly after hydralazine and prazosin and increased slightly after treatment with the beta-blocking drugs, although none of these changes were significant except those during hydralazine treatment. Processing of the STIs was greatly facilitated by the automated system for recording and analyzing the measurements.