"[P]acemakers elevate the heart rate... but they don’t always reproduce a normal heartbeat. ...[I]f the pacemaker leads are placed directly in ventricular muscle... the natural electrical system is not utilized. ...[T]here is loss of the natural twisting motion needed for efficient contraction. It may even cause heart function to worsen and produce heart failure in patients with dilated hearts. In other patients, fatigue will not improve, and shortness of breath will not get better."