Fellows Course: MCS Overview with Latest Data and Guidelines
Jeffrey Moses, MD, discusses mechanical circulatory support (MCS) devices and the data supporting their use, explaining that temporary MCS is an essential tool in contemporary percutaneous coronary intervention (PCI) practice. Dr. Moses is a professor of cardiology and director of interventional cardiac therapeutics at Columbia University Medical Center and director of complex coronary interventions at St. Francis Hospital in Roslyn, NY. This discussion was part of Abiomed’s MCS & Complex Coronary Intervention virtual fellows course held on September 26, 2020.
The use of MCS, Dr. Moses emphasizes, should be “very judicious, and thoughtful, and evidence-based.” It is important to think about performance both in terms of myocardial energetics (PV loops) and effects on peripheral circulation (CPO). Dr. Moses explains that shrinking the PV look and moving it down to the left increases myocardial efficiency and reduces myocardial work. “And that’s one of the key objectives of mechanical circulatory support in terms of the myocardium itself.” The best index for the effect of MCS on peripheral circulation is cardiac power output (CPO). The prognosis in cardiogenic shock is highly dependent on CPO, Dr. Moses states. “As the power drops, mortality incrementally increases.”
Dr. Moses explains that the goals of hemodynamic support are to reduce myocardial oxygen demand, increase myocardial oxygen supply, and increase CPO. As he discusses various MCS devices—intra-aortic balloon pump (IABP), TandemHeart, Impella®, and extracorporeal membrane oxygenation (ECMO)—he describes their effects on each of these components.
The IAPB, he notes, is a well-known technology the provides modest increases in CO and coronary perfusion and is relatively easy to use; however, it does not effectively unload the heart, requires a minimum of cardiac function and stable rhythm, and demonstrates no proven benefit on mortality.
TandemHeart, he explains, creates an extracorporeal circuit that bypasses the left ventricle. However, while it unloads the left atrium, the retrograde flow into the femoral artery contributes to increased afterload. Thus, TandemHeart increases the PV area and increases the work of the heart.
Impella actively unloads the left ventricle and can significantly increase cardiac index and mean atrial pressure and reduce systemic vascular resistance and wedge pressure. “So this is active support,” Dr. Moses emphasizes, “in a heart that needs unloading and is not producing enough cardiac output.” Dr. Moses reviews data supporting the use of Impella, including data demonstrating that early initiation Impella support, before revascularization, improves outcomes in AMI cardiogenic shock. He also presents ongoing studies designed to present objective evidence that will “cement the guidelines in many clinical scenarios” as well as controversial administration database studies, for which he cautions: “read these types of articles with a healthy bit of skepticism.”
Dr. Moses also discusses uses and data for ECMO, “the most aggressive of the devices.” While ECMO does support circulation, it increases PV area and increases the work of the heart. However, data support improved survival by concomitantly unloading the heart with Impella.
In conclusion Dr. Moses states, “It’s very important once you segregate out the nature of the shock, to apply the right device to the right entity, whether it’s predominantly left ventricle, or right ventricular, or biventricular. And if any of these initial entities do not respond to your initial administration, it’s important not to sit on them, but to escalate them to more powerful combinations.”