Abstract 2465: QT/RR Slope: A Novel Arrhythmogenic Substrate In Hypertensive Left Ventricular Hypertrophy
Objective: Left ventricular hypertrophy (LVH) portends an increased risk of ventricular arrhythmias and sudden death. QT rate dependence, i.e. the dependence of QT interval from the duration of the preceding cardiac cycle, is a major predictor of ventricular arrhythmias in hypertrophic cardiomyopathy, after myocardial infarction, and in patients receiving antiarrhythmic drug therapy, but data in hypertensive LVH are lacking.
Methods: A total of 912 patients with untreated essential hypertension (57% men; age 49+/−11 years) underwent M-mode echocardiography and standard electrocardiography. The QT interval was manually measured to the nearest 10 milliseconds in all leads from the onset of the QRS complex to the end of the T wave, and the longest QT interval was chosen. The average of 3 consecutive normal beats was considered for the analysis.
Results: In the whole cohort, a direct relation was found between the duration of RR interval and QT duration (r=0.59, p<0.001). The slope of QT/RR regression line was greater in patients with LVH (LV mass >=51 g/m^2.7; n=324, b=0.163) than in those without (n=588, b=0.110), and such difference held in a multiple linear regression (multiplicative interaction term “RR * LVH”: beta=0.749, p<0.0001). The QT/RR regression slope increased progressively ongoing from the bottom to the top quartile of LV mass (Figure⇓).
Conclusions: In essential hypertension, left ventricular hypertrophy is associated with an increased slope of QT/RR regression line. This potential arrhythmogenic substrate may contribute to explain the hypertensive LVH-related risk for ventricular arrhythmias and sudden death.