Implications of electrocardiographic frontal QRS axis on left ventricular diastolic parameters derived from electrocardiogram-gated myocardial perfusion single photon emission computed tomography.

BACKGROUND: Current electrocardiographic (ECG) machines report various variables including frontal QRS axis automatically. We tested the hypothesis that QRS axis is associated with left ventricular (LV) diastolic parameters derived from ECG-gated myocardial perfusion single photon emission computed tomography (SPECT) independent of myocardial ischemia.

METHODS: Ninety-three patients with preserved LV ejection fraction and no evidence of myocardial ischemia were enrolled based on ECG-gated SPECT. Peak filling rate (PFR), one-third mean filling rate (1/3 MFR) and time to peak filling (TTPF) were obtained as LV diastolic parameters.

RESULTS: There were 82 male and 11 female patients with a mean age of 69 ± 9 years. QRS axis ranged from - 40° to 85° (36° ± 31°). QRS axis was correlated with PFR (r = 0.28, p < 0.01), 1/3 MFR (r = 0.25, p = 0.02) and TTPF (r = - 0.21, p = 0.04). QRS axis was also correlated with age (r = - 0.23, p = 0.03), body mass index (BMI) (r = - 0.36, p < 0.01) and LV mass index (LVMI) (r = - 0.27, p < 0.01). Linear regression analysis showed that QRS axis was associated with PFR, 1/3 MFR and TTPF for LV diastolic function, but was not associated with these LV diastolic parameters after adjustment of various confounders.

CONCLUSIONS: Our data suggest that QRS axis depends on age, BMI or LVMI, and serves as a surrogate marker of LV diastolic function.