Manipulation of external pressure as a method to assist the failing heart

The development and state of the art in circulatory assistance using external pressure variations is reviewed. All of these techniques use the principle that by cyclic external pressure waves properly timed to the cardiac cycle, hemodynamic energy can be noninvasively transmitted to assist the circulation. Cyclic pressure waves to the lower body require that the high pressure phase occurs in diastole in order to augment cardiac output or coronary flow. In contrast, pressure waves to the chest would optimally augment cardiac output if they begin at the onset of ventricular systole. Manipulation of lung pressure by synchronized ventilation may be also utilized to augment cardiac output. The above methods are discussed in detail in the manuscript with special emphasis on the pathophysiology and mechanisms of cardiac assistance.