Several important issues such as atrial fibrillation and CRT, response of elderly patients to CRT and the aspects of upgrading conventional pacemakers to biventricular devices are addressed. The peak endocardial acceleration (PEA) concept and PEAarea method are explained. Finally, the role of pressure-volume loop analysis in CRT is discussed. Chapter 2 We studied 130 patients with a biventricular pacemaker and advanced heart failure. Echocardiographic response (LVEF improvement ? 5 %) was documented in 69%, 88% and 91% of the survivors, after 3 months, 1 year and 2 years, respectively.