<qa>  What is the pathophysiologic mechanism responsible for heart failure?The pathophysiologic mechanisms responsible for the development of heart failure in people with preserved ejection fraction i.e. normal left ventricular function remain poorly understood. One possible mechanism may be the contribution of increased arterial stiffness to changes in pulsatile hemodynamic load during ventricular systole, implicating abnormal ventricular-vascular interactions throughout the cardiac cycle in the pathogenesis of heart failure with normal ejection fraction. 