Cardiac Resynchronization Therapy: The Low Voltage Road or the High Voltage Road?

Abstract

Cardiac resynchronization therapy is an additional therapeutic option for heart failure patients that has became available in recent years and aroused great interest among both electrophysiologists and clinical cardiologists managing heart failure patients. The prevalence of conduction disturbances (QRS interval ≥120 ms) among patients with left ventricular dysfunction or overt heart failure has been found to range between 27% and 53% [1–3]. Upon analyzing subjects with varying degrees of functional impairment according to New York Heart Association (NYHA) functional class, wider mean QRS intervals were found in subjects with a higher degree of functional impairment [4]. In subjects with dilated cardiomyopathy the QRS interval was widened in elec- trograms recorded shortly before death as compared to recordings made a mean of 35 months before the terminal event [5]. In unselected patients, left bundle branch block was associated with increased risk of both total mortality and sudden death at 1 year [2]. In another study [6] a QRS duration >110 ms was associated with increased mortality independently of left ventricular ejection fraction. It is a matter for investigation to assess whether left bundle branch block with left QRS axis deviation is most closely related to left ventricular enlargement and left ventricular dysfunction or whether it carries additional prognostic implications [7]. In a recent paper [8], a widening of the QRS interval in patients with heart failure who were followed by a heart failure clinic was a definite and independent predictor of mortality. According to these data, analysis of the QRS interval may provide additional information as a basis for selecting candidates for nonpharmacological treatments.