Electrocardiographic risk stratification of asymptomatic population without cardiovascular disease: Should we add the QRS-T angle?

Effect of anemia on the frontal QRS-T angle

BACKGROUND

Anemia is a common health problem worldwide and is associated with a poor prognosis for cardiovascular diseases. It can alter myocardial depolarization and repolarization by affecting the generation and propagation of electrical impulses. The frontal QRS-T angle is a novel marker of the absolute difference between myocardial depolarization and repolarization. This study investigated the effects of anemia on the frontal QRS-T angle.

METHODS

The study included 66 anemic subjects with no cardiac disorders, and 50 age- and gender-matched controls. Twelve-lead electrocardiography (ECG) was obtained for all subjects, and the frontal QRS-T angle was calculated based on the automatic report of the ECG machine.

RESULTS

Subjects with anemia had a significantly higher frontal QRS-T angle than subjects without anemia (28.9±14.1 vs. 22.5±11.8, P=0.011). In correlation analysis, the frontal QRS-T angle was positively correlated with the Body Mass Index (BMI; r=0.287, P=0.002), left ventricular mass (LVM; r=0.264, P=0.004), and heart rate (r=0.275, P=0.003) and negatively correlated with the hemoglobin level (r=-0.349, P<0.001). Multivariate regression analysis showed that the hemoglobin level (β=-0.254, tβ=-2.805, P=0.006), BMI (β=0.240, t=2.770, P=0.007), and LVM (β=0.201, t=2.303, P=0.023) were independently associated with the frontal QRS-T angle.

CONCLUSIONS

The hemoglobin level was found to be an independent predictor of the frontal QRS-T angle.

Prognostic value of frontal QRS-T angle in patients undergoing myocardial revascularization or cardiac valve surgery

BACKGROUND

An abnormal frontal QRS-T angle (fQRSTa) is associated with increased risk of death in primary and secondary cardiovascular prevention. The aim of this study was to evaluate the fQRSTa prognostic role in patients undergoing myocardial revascularization and/or cardiac valve surgery.

METHODS

We enrolled and prospectively followed for 48 ± 26 months 939 subjects with available QRS and T axis data; mean age was 68 ± 12 years, 449 patients (48%) underwent myocardial revascularization, 333 (35%) cardiac valve surgery, 94 (10%) valve plus bypass graft surgery and 63 (7%) cardiac surgery for other cardiovascular (CV) diseases. The ECG variables were collected at the end of the cardiac rehabilitation program and fQRSTa was considered normal if <60°, abnormal if >120°, borderline otherwise. Endpoints were overall and CV mortality.

RESULTS

The fQRSTa was normal in 333 patients (36%), borderline in 285 (30%) and abnormal in 321 (34%). Overall (p = 0.012) and cardiovascular (p = 0.007) mortality were significantly higher in patients with abnormal fQRSTa even after adjusting separately for gender, PR-, QTc- intervals, presence of right or left bundle branch block and left atrial volume index. The predictive value was confirmed in patients with stable coronary artery disease (SCAD), not in patients with acute coronary syndrome or valve disease. SCAD patients with abnormal both fQRSTa and QRS axis had higher risk of overall (hazard ratio = 2.9, p < 0.0001) and CV (hazard ratio = 4.4, p < 0.0001) mortality compared with SCAD patients with normal fQRSTa, even after multivariate adjustment for age, gender, ECG intervals, left-ventricle ejection fraction and mass index.

CONCLUSIONS

In SCAD patients undergoing myocardial revascularization, abnormal fQRSTa is independent predictor of overall and CV mortality.