Mechanical circulatory support (MCS) use in cardiogenic shock (CS) in the setting of acute myocardial infarction (AMI) is one of the most controversial topics in cardiology. Despite advances in many aspects in our cardiovascular field, mortality from CS remains unacceptably high. At the most recent AHA meeting, two studies suggested the use of intra-aortic balloon pumps (IABP) in CS might result in better outcomes compared to use of the percutaneous MCS device, Impella. I wanted to share my thoughts and ideas on this topic in light on these studies.
Major Randomized Clinical Trials on MCS
There is limited evidence in the literature supporting the use of MCS in AMI-CS1-3. There are two main randomized clinical trials in MCS devices: IABP-SHOCK II and IMPRESS trials. IABP-SHOCK II trial compared IABP with medical treatment in 600 patients with AMI-CS, and showed no difference in survival between the two groups2. The IMPRESS trial compared Impella CP versus IABP in 48 patients with CS-AMI and again did not show a difference in survival between these groups3.
Summary of recently-released studies at AHA19
A study by Amin et al, which included 48,306 patients undergoing percutaneous coronary intervention (PCI) with MCS from the Premier Healthcare Database, found wide variations in the use and clinical outcomes of Impella (mortality, stroke, bleeding, acute kidney injury) across hospitals. They also found that Impella had higher odds of adverse events and higher costs compared to IABP after adjusting for hospital, patients and time period4.
A separate study by Dhruva et al, which included 28,304 matched patients with AMI-CS undergoing PCI from NCDR Cath-PCI registry, found that 8,471 patients (29.9%) had IABP only, and 1,768 patients (6.2%) had Impella only. In-hospital outcomes were compared; in-hospital mortality was 34.1% with IABP compared to 45% with Impella use, and in-hospital bleeding rates were also lower in IABP group with 16% versus 31.3% in the Impella group5.
In light of the results of these two observational real-world studies, I think we should take these results with a grain of salt. As we know, observational data has its own limitations, including confounding bias. Patients with AMI-CS may differ significantly based on their co-morbidity profile and angiographic complexity, which could potentially influence device selection; as we expect that patients who are sicker will usually get Impella as it provides more hemodynamic support compared to IABP, making comparison between these two devices inaccurate.
Both studies have shown an increase in the use of Impella over the past years, which is an opportunity to study these devices with larger numbers in different clinical settings. Registries across the nation are being established to build databases to compare these devices. Stronger evidence and more robust data with potential randomized clinical trials are much needed to help us know how to best manage this complex patient population and select which MCS device is optimal for each of our patient populations.
I would like to say special thank you to Dr Khaldia Khaled, my friend and colleague at Louisiana State University, for helping me write this blog and for her continued support.
1- Schrage B et al: Impella Support for Acute Myocardial Infarction Complicated by Cardiogenic Shock. Circulation. 2019 Mar 5;139(10):1249-1258.
2- Thiele et al: Intraaortic Balloon Support for Myocardial Infarction with Cardiogenic Shock. N Engl J Med 2012; 367:1287-1296. DOI: 10.1056/NEJMoa1208410
3- Ouweneel DM et al: Experience from a randomized controlled trial with Impella 2.5 versus IABP in STEMI patients with cardiogenic pre-shock. Lessons learned from the IMPRESS in STEMI trial. Int J Cardiol. 2016 Jan 1;202:894-6. doi: 10.1016/j.ijcard.2015.10.063. Epub 2015 Oct 9.
4- Amin et al: The Evolving Landscape of Impella® Use in the United States Among Patients Undergoing Percutaneous Coronary Intervention with Mechanical Circulatory Support.
Circulation. 2019 Nov 17. doi: 10.1161/CIRCULATIONAHA.119.044007.
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