A system for and method of treating a malfunctioning heart is based on hemodynamics, the pressure at a site in a patient's circulatory system being sensed. A signal is developed representative of short term mean arterial pressure (MAP), mean right atrial pressure (MRAP), mean right ventricle pressure (MRVP), mean left atrial pressure (MLAP), mean left ventricle pressure (MLVP), mean central venous pressure (MCVP), mean pulmonary artery pressure (MPAP), mean pulmonary vein pressure (MPVP), mean pulmonary capillary wedge pressure (MPCWP), right ventricular systolic pressure (RVSP), right ventricular end diastolic pressure (RVEDP), or right ventricular pulse presure (RVPP). A signal representative of fixed or varying baseline pressure is provided and if the short term current 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 fixed or varying baseline pressure and 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.