The purpose of post-arrest cardiogenic shock therapy is to reduce cardiac effort while keeping essential organs perfused. Vasopressors enhance systemic blood pressure and cardiac output at the expense of increased myocardial oxygen demand and peripheral vascular resistance, accelerating tissue acidosis and multi-organ failure. Increasing vasopressors is associated with poor clinical outcomes in cardiogenic shock induced by acute myocardial infarction. Mechanical circulatory support allows users to minimize heart effort while maintaining essential organ perfusion without the risk of vasopressor side effects (Emory Department of Medicine, 2017). The intra-aortic balloon pump (IABP) and Impella are two MCS devices that are often used, especially in the case of acute myocardial infarction. By inflating during ventricular diastole and deflating during systole, IABP enhances coronary artery perfusion and increases cardiac output. In post-arrest individuals, particularly those with obstructive coronary artery disease, these hemodynamic consequences may be significant. Impella has the ability to enhance cardiac output. Both devices are generally implanted percutaneously during left heart catheterization in a cardiac catheterization laboratory.
In cardiogenic shock, inotropic and vasopressor medications can be utilized to improve hemodynamic parameters quickly. They are usually given with the notion that increasing cardiac output or vascular tone can help with short-term clinical recovery. Despite all of these medications producing ventricular arrhythmias, contraction band necrosis, and infarct enlargement, they all enhance myocardial oxygen demand. The hemodynamic advantages are thought to exceed the dangers of an inotropic treatment since hypotension impairs myocardial perfusion (Mandawat, 2017). Increased myocardial oxygen consumption and vascular tone may have unfavorable effects, such as impaired peripheral organ perfusion and an increase in myocardial ischemia, which can negatively influence clinical outcomes. Despite favorable short-term results, many patients with acute myocardial infarction are left with large infarcts and organ dysfunction, limiting long-term survival and quality of life. It is suggested that pharmacological inotropic circulatory support be used.
Mechanical cardiac aid aims to help the ailing circulation by increasing systemic blood flow, which prevents organ hypoperfusion and facilitates overall organ recovery. In addition to providing hemodynamic support, mechanical cardiac aid may also provide myocardial protection by unloading the ventricle. This left ventricular unloading may reduce infarct size and improve left ventricular recovery. The Impella’s immediate unloading of the left ventricle is a crucial feature (Mandawat, 2017). Reduced end-diastolic wall stress and a rapid reduction while employing the Impella indicate the unloading effect. A rise in coronary perfusion pressure and flow is also seen. The PVA of measured pressure-volume loops is lower, indicating that the myocardium consumes less oxygen. Increased perfusion pressure and lower left ventricular volume – related intramyocardial resistance are likely responsible for the Impella – induced increase in coronary flow. The Impella support has been shown to decrease infarct size in a case study. Because it contributes far more to total circulation, it should result in even more unloading.
The registry’s main conclusion is that implanting the Impella before revascularization may enhance survival considerably. These findings are consistent with those of other registries, which show that starting Impella treatment before revascularization is linked to a reduced death rate (Dhruva et al., 2021). The insertion of an Impella before primary PCI may allow for more stable hemodynamics during the procedure. It may help to avoid deterioration during the operation and when the occluding artery is opened. Some animal investigations have demonstrated that emptying the left ventricle before reperfusion decreases infarct size despite the extended ischemia period. According to these investigations, the administration of Impella prior to revascularization triggers the neurohormonal cascade linked to reperfusion damage. As a result, a cardioprotective signaling cascade is activated, which reduces myocardial damage.
Dhruva, S., Ross, J. S., & Mortazavi, B. J. (2021). Use of mechanical circulatory support devices among patients with acute myocardial infarction complicated by cardiogenic shock. JAMA Network Open, 4(2), 1-13. Web.
Emory Department of Medicine. (2017). Cardiac arrest and percutaneous mechanical circulatory support for cardiogenic shock [Video]. YouTube.
Mandawat, A. (2017). Percutaneous mechanical circulatory support devices in cardiogenic shock. Circulation: Cardiovascular Interventions, 10(5), 1-11. Web.