J-point Amplitude Research Articles

Comparison of primary coronary angioplasty versus thrombolysis in patients with ST-segment elevation acute myocardial infarction and grade II and grade III myocardial ischemia on the enrollment electrocardiogram

We investigated the impact of primary angioplasty compared with thrombolysis in 894 patients with ST elevation acute myocardial infarction and electrocardiographic grades II and III ischemia on enrollment. Patients were divided into 2 groups based on the enrollment electrocardiogram—grade III: (1) absence of an S wave below the isoelectric baseline in leads that usually have a terminal S configuration (leads V 1 to V 3), or (2) ST J-point amplitude ≥50% of the R-wave amplitude in all other leads. To be included in the grade III group, grade III criteria in ≥2 adjacent leads were required. Patients with ST elevation but without grade III criteria were classified as having grade II. In-hospital mortality was 3.2% and 6.8% in the grade II (n = 616) and grade III (n = 278) groups, respectively (p = 0.016). In the grade II group, in-hospital mortality was similar in the thrombolysis and angioplasty subgroups (3.2% and 3.3%, p = 0.941). In patients with grade III, in-hospital mortality was 6.4% and 7.3%, respectively (p = 0.762). The odds ratio for the grade III group for death with thrombolysis was 2.06 (95% confidence intervals [CI] 0.82 to 5.19; p = 0.125); the odds ratio for primary angioplasty was 2.30 (95% CI 0.93 to 5.66; p = 0.07). In the thrombolysis group, reinfarction occurred in 3.3% and 6.5% of the grade II and grade III subgroups (p = 0.137). In the angioplasty group, reinfarction occurred in 1.3% and 4.4%, respectively (p = 0.239). Grade III ischemia on admission was associated with higher in-hospital and 30-day mortality and a higher rate of reinfarction. There was no difference in mortality between primary angioplasty and thrombolysis in the grade II and grade III ischemia patients.

Electrocardiographic Findings in a Healthy Biracial Population

It has been well documented that the prevalence of certain electrocardiographic (ECG) findings among individuals free of coronary heart disease (CHD) differs by race. However, it is not known whether these differences exist independently of CHD risk factors (e.g., hypertension). We examined the ECG tracings of 2,686 apparently healthy, middle-aged African-American and white men and women who participated in the Atherosclerosis Risk in Communities Study and were at low risk of CHD. Using the Minnesota Code, among men, 46% of African-Americans, but only 25% of whites, had a minor ECG finding (p <0.001). In women, 32% of African-Americans and 23% of whites had a minor ECG finding (p <0.01). Specifically, the age-adjusted prevalences of high-amplitude R wave, ST elevation, T-wave findings, and prolonged P-R interval were statistically significantly higher in African-Americans. As for continuous ECG measurements, the R wave in leads V 5 and V 6, the S wave in V 1, the J-point amplitude in leads V 2 and V 5, the P-R interval, and the Cornell voltage (|S V 3| + R aVL) for left ventricular hypertrophy were all significantly greater in African-Americans than in whites. However, in both men and women, the heart rate corrected QT interval was shorter in African-Americans than in whites. All of these findings remained statistically significant after further adjustment for traditional CHD risk factors. These results suggest that racial differences in electrocardiograms may not be explained entirely by differences in established CHD risk factors, and because current diagnostic ECG criteria are largely based on data from middle-aged white men and women, race should be considered in the interpretation of ECG findings.

Selection of optimal electrocardiographic leads from body surface potential maps for the diagnosis of left ventricular hypertrophy

In this study, we assess the effects of electrode placement error on the EASI-derived 12-lead electrocardiogram (ECG). The study data set consisted of 744 body surface potential map (BSPM) recordings. The BSPMs, each of which was made up of 117 leads, were recorded from a mixture of healthy, myocardial infarction, and left ventricular hypertrophy subjects. The BSPMs were interpolated to increase the number of data points in the region of the EASI recording electrodes I, E, and A and the precordial leads. This facilitated 3 experiments. Firstly, recording sites I, E, and A were simultaneously moved ±5 cm vertically, in 0.5 cm increments, from their correct locations. Secondly, recording sites I and A were moved horizontally, again up to ±5 cm, in 0.5 cm increments. Finally, all 6 precordial leads were moved vertically in 0.5 cm increments up to ±5 cm. At each movement step, the resulting 12-lead ECG was compared with the original 12-lead ECG. Root mean square error was determined along with the absolute difference in J-point amplitude. Although the EASI leads were found to be less sensitive to electrode misplacement than the standard precordial leads, it was found that when precordial leads were moved up to ±3 cm vertically, the resulting 12-lead ECG more accurately resembled the original 12-lead ECG than a 12-lead ECG reconstructed from accurately positioned EASI leads. Further work is required to establish the effects of electrode misplacement beyond the ±5 cm limits assessed in this study.