Among 838 patients enrolled in the study with an index event defined as first acute MI, there were 216 females (26%) and 622 males (74%). The baseline clinical variables are described in . Women were older, had more diabetes and hypertension, and presented more frequently with pulmonary congestion than men. Thrombolytic therapy was used less frequently in women. Men in the study were more likely to be Caucasian and current or ex-smokers. Heart rate at baseline ECG was faster, QTc was longer, and QRS duration was shorter in females compared to males, whereas QRS voltage was higher in males than females (). There was no difference in the frequency of Q wave MI and non-Q wave MI between males and females. However, males had more Q waves in inferior leads than females (44% vs. 35%, p=0.03). The presence of Q waves in other locations was similar in males and females.
When analyzing changes in ST-T segment, females had ST segment depression in lateral leads (V5-6, I, aVL) significantly more often as compared to males. There was no significant difference in the frequency of ST depression in other locations. Women had more frequent T wave inversions in anterior and lateral location with no difference in inferior location in comparison to men.
In multivariate logistic regression analysis, the following clinical variables were associated with female gender: advanced age, history of diabetes, and hypertension. When ECG parameters were tested after adjustment for the above clinical variables, lateral ST depression, faster heart rate, and longer QTc were positively associated with female gender, whereas longer QRS duration and higher sum of SV2 and RV5 voltage were more likely to occur in males ().
Clinical and Electrocardiographic Parameters Associated with Female Gender in the Multivariate Logistic Regression Analysis
During mean follow-up time of 688 ± 279 days, there were 138 cardiac events in males and 65 in females (events rate males vs. females 22% vs. 30%, p=0.02). There were 79 combined end-points of death or non-fatal MI (10% in males vs. 8% in females, p=0.52) and 10 cardiac deaths (1% in males vs. 1% in females, p=0.71). Females had a higher likelihood of combined cardiac events compared to males ().
Cumulative probability of recurrent events by the gender in patients after MI.
Age, Caucasian ethnicity, history of diabetes mellitus, hypertension, pulmonary congestion, type of MI (Q wave vs. non-Q wave), history of smoking, and therapies with ACE-I, aspirin, beta-blockers and diuretics were considered in stepwise Cox analyses model. The only predictive variable that entered the model was the type of MI (Q wave vs. non-Q wave). After adjustment for the type of index event (Q wave MI vs. non-Q wave), females had a 38% higher risk of cardiac events compared to males (adjusted HR= 1.38, 95% CI 1.03-1.86, p= 0.03). Among all tested ECG variables, only lateral ST depression in males () and persistent anterior ST segment elevation in females were associated with significantly increased risk of recurrent cardiac events (). In addition, anterior T wave inversions in females had a positive trend toward worsened outcome (). After adjusting for type of index event (Q wave vs. non-Q wave), lateral ST depressions among males and persistent anterior ST elevations among females were the only significant ECG predictors of recurrent cardiac events. The interaction between gender and anterior ST segment elevation was significant. Anterior T wave inversions did not reach statistical significance level ().
Figure 2A Cumulative probability of recurrent events among males by presence of lateral ST depressions.
Figure 3A Cumulative probability of recurrent events among males by presence of ST elevation in V1-V4 on the 5th -7th post-MI day.
Cumulative probability of recurrent cardiac events among females by presence of T waves inversions in leads V1-4.
Multivariate Cox Analysis of Electrocardiographic Parameters in Predicting Cardiac Events in Males and Females After Myocardial Infarction