A system for and method of treating a malfunctioning heart is based on hemodynamics. The mean arterial pressure (MAP) mean right atrial pressure (MRAP), mean right ventrical pressure (MRVP), mean left atrial pressure (MLAP), mean left ventrical pressure (MLVP) or mean central venous pressure (MCVP) is sensed. The long term mean baseline pressure is monitored and if the short term current mean pressure differs therefrom by a predetermined value, an indication of hemodynamic compromise, cardioversion/defibrillation is effected. In a second embodiment, the determination of whether the difference between mean baseline and mean current pressure is undertaken after a rate criteria (for example a heart rate above 155 b.p.m. has been met. In a third embodiment, the rate and pressure criteria both must exist at the same time, before cardioverting/defibrillation is initiated. In a fourth embodiment, a microprocessor is used. The system may be integrated with antitachycardia and/or antibradycardia pacemakers.