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Regression of ventricular repolarisation inhomogeneity after aortic bileaflet valve replacement in patients with
1National Taiwan University College of Medicine, Departments of Surgery and Internal Medicine, National Taiwan University Hospital, Taipei. tsaicher@ha.mc.ntu.edu.tw
Background:
Aortic valve replacement relieves mechanical outflow obstruction in patients with aortic stenosis. However, there is limited information on whether aortic valve replacement can provide regression of ventricular repolarisation inhomogeneity.
Objectives:
To determine whether aortic valve replacement can provide regression of ventricular repolarisation inhomogeneity in patients with aortic stenosis after bileaflet aortic valve replacement.
Methods:
We studied the changes of electrocardiographic QT or QTc intervals and QT or QTc dispersions of 71 patients with severe aortic stenosis and angiographically insignificant coronary lesions (<50% in diameter) before and after valve replacement (6+/-3 days after operation). Seventy-one healthy control subjects, matched for age and sex, served as control subjects. Twelve-lead electrocardiograms and echocardiographic examinations were measured before and after surgery. The QT interval was corrected for heart rate using the standard Bazett formula. QT dispersion was defined as the difference between maximal and minimal QT interval measurements occurring among any of the 12 leads on a standard electrocardiogram. QTc dispersion was calculated in a manner similar to QT dispersion. No subject had fewer than nine measurable leads.
Results:
Left ventricular systolic blood pressure, pressure gradient across aortic valve, left ventricular mass index, and systolic wall stress were significantly reduced after valve replacement compared with before valve replacement. The QT interval significantly decreased from 425+/-38 ms to 398+/-32 ms after replacement (P<0.0001). The QTc dispersion significantly decreased from 62+/-25 ms to 32+/-13 ms after replacement (P<0.0001). The value of QT or QTc dispersion after replacement was similar to that in controls. Univariate analysis revealed that QTc dispersion was significantly only correlated with left ventricular mass index (r=0.236, P=0.05). Multivariate analysis revealed that the best predictor of QTc dispersion was sex and left ventricular mass index (P=0.008 and 0.005, respectively).
Conclusions:
Our study demonstrated a favorable consequence of aortic valve replacement distinct from hemodynamic improvement. Patients with aortic stenosis before valve replacement have abnormal prolonged QT or QTc intervals and increased QT or QTc dispersions. After successful valve replacement left ventricular mass index regressed and QT or QTc intervals and QT or QTc dispersions were normalized. These findings warrant further investigation in a large trial and long-term follow-up for clinical implications.