The main goal of mechanical cardiac assistance is to provide haemodynamic support in case of an endangered coronary or systemic circulation by increasing or maintaining coronary and systemic blood flow. In addition to haemodynamic support, mechanical cardiac assistance may also provide myocardial protection by unloading the ventricle. The experience with percutaneous mechanical support devices is mainly gathered in patients with cardiogenic shock (CS) or during high-risk percutaneous coronary intervention (PCI).
CS is a physiological state in which inadequate tissue perfusion results from cardiac dysfunction, most commonly due to acute myocardial infarction. Non-ischaemic causes include myocarditis, end-stage cardiomyopathy or sustained arrhythmias. CS remains the leading cause of death for hospitalised patients after ST-segment elevation myocardial infarction (STEMI).1 If CS occurs after STEMI, it is mostly a consequence of decreased myocardial contractility due to the infarction, resulting in a cascade of decreased cardiac output (CO), hypotension and decreased coronary blood flow, which will further reduce contractility and CO. This vicious circle may not only lead to further myocardial ischaemia, but also to diminished organ perfusion and ultimately multiple organ failure and death.
Patients with complex or high-risk coronary lesions due to extensive and diffuse multivessel, left main or last remaining coronary artery disease, who previously were not considered suitable for PCI, are increasingly treated with PCI. In patients who have been refused for cardiac surgery, PCI is increasingly considered as an alternative. During these high-risk procedures, haemodynamic compromise and complications can occur rapidly, for which support of a mechanical cardiac assist device can be helpful, particularly in patients with poor left ventricular (LV) function. Although the exact role of mechanical cardiac assistance in periprocedural risk management of complex and high-risk PCI procedures remains debatable, a growing number of high-risk PCI procedures are being performed with mechanical cardiac assistance.
Haemodynamic Support
The primary objective of cardiac support is the maintenance of haemodynamic stability. This is achieved by maintaining or improving coronary and systemic blood flow in order to ensure sufficient CO and adequate organ perfusion. The improvement of coronary and microvascular blood flow could also accelerate recovery of stunned myocardium after ischaemia. The SHOCK-trial investigators have shown that cardiac power output (CPO) is the best haemodynamic parameter to predict mortality in case of CS.2 This parameter takes the CO and the mean arterial pressure into account, based on the assumption that both adequate CO and blood pressure are necessary for sufficient end-organ perfusion. Haemodynamic support devices should be able to maintain both CO as well as blood pressure to provide adequate organ perfusion, ideally without the use of concomitant vasopressor or inotrope therapy.