Right Ventricular Pacing in Bradycardia Patients With Preserved Systolic Function: Results of the PACE Trial

In medicine, it is encouraging when research yields results consistent with our understanding of the operative mechanisms, especially when there is a direct potential impact on clinical practice. Adverse left ventricular (LV) remodeling is a complex maladaptive process involving structural, hemodynamic, histopathological, and genetics changes. The process may be multifactorial and is frequently encountered in patients after loss of myocardium (myocardial infarction), volume overload (valvular insufficiency), or pressure overload (hypertension). It involves both LV hypertrophy and dilation, and is initially an adaptive response that serves to maintain stroke volume. If persistent and progressive, the process becomes maladaptive and leads to further deterioration of LV function, LV dilation, and eventually the typical symptoms of heart failure. It is evident that substantial prolongation of the QRS complex, especially with a left bundle branch block (LBBB) pattern, results in a delayed and dyssynchronous LV contraction.This dyssynchrony may be a major contributor that can both initiate and aggravate the process of adverse remodeling... (excerpt