2008n-740 arrhythmia arrhythmias artificial bioelectricenergysources biomedicalengineering biomedicalmaterials blood cardiac cardiacpacing circulation congresses defibrillators diseases electriccountershock electricproperties electrophysiology electrotherapeutics heart heartconductionsystem implantable implanted mechanical pacemaker rd598c3422009 therapy treatment wg168c26172009