Circulatory Support Devices in the Catheterization Laboratory: Evolution or Revolution?

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Innovation in the field of interventional cardiology has redefined the term “complex percutaneous intervention.” No longer are anatomic variables such as left main stenosis, bifurcation disease, or multi-vessel PCI considered “out of reach” for the interventional community. The lines between basic and advanced structural intervention have similarly been altered with the widespread adoption of transcatheter aortic valve replacement and next-generation approaches for functional mitral regurgitation. Advances in wire and balloon technology have also resulted in rapid coronary reperfusion in acute myocardial infarction (AMI) and thereby significantly reduced in-hospital mortality. As a result of this expanding interventional domain, in-hospital mortality has been reduced in AMI; however, the number of AMI patients surviving to ultimately develop systolic heart failure has grown substantially. This increasing heart failure population has led to a growing demand for mechanical support options to support coronary and non-coronary interventions. Therefore, the approach to the high-risk interventional patient now requires a better understanding of invasive hemodynamics, heart failure status, and the impact of device therapy on physiologic and clinical outcomes. 

The overall goals of percutaneous circulatory support systems are to: (1) increase vital organ perfusion; (2) augment coronary perfusion; and (3) reduce wall stress, stroke work, and myocardial oxygen consumption. Clinical scenarios where these devices are commonly used include cardiogenic shock, mechanical complications after AMI, high-risk coronary and non-coronary intervention, and for high-risk electrophysiologic procedures.

The intra-aortic balloon pump (IABP) is a catheter-mounted balloon that augments pulsatile blood flow by displacing blood volume in the descending aorta, which reduces ventricular afterload and increases in mean arterial pressure and stroke volume. Larger capacity IABPs, known as the Mega Series (Maquet), have been introduced into practice; however, their clinical utility remains unknown. Advantages of IABPs may include ease of insertion, global familiarity with the technology, and relative cost. 

Both the Impella (Abiomed) and TandemHeart (CardiacAssist) devices are rotodynamic pumps that generate continuous, minimally pulsatile flow when functioning optimally. The Impella devices are catheter-mounted axial-flow pumps that are placed into the left ventricle in retrograde fashion across the aortic valve. The Impella 2.5 LP and CP devices can be deployed without the need for surgery, while the Impella 5.0 device requires surgical vascular access. The TandemHeart device is an extracorporeal centrifugal flow pump that reduces left ventricular preload by transferring oxygenated blood from the left atrium to the descending aorta via a transseptal inflow cannula in the left atrium and an arterial outflow cannula in the femoral artery. Other centrifugal pumps include the Centrimag (Thoratec), Rotaflow (Maquet), and Biomedicus (Medtronic) pumps. The net effect of these devices is to reduce native left ventricular volume and pressure, while increasing mean arterial pressure without greatly influencing ventricular afterload. The advantage of the Impella 2.5 and CP devices is ease of insertion via a single arterial access, while an advantage of the TandemHeart device is the magnitude of support provided without the need for surgical vascular access. No studies comparing these continuous flow devices head-to-head exist.

Clinical trials examining the clinical utility of percutaneous circulatory support devices have failed to identify reduced in-hospital mortality in high-risk PCI or cardiogenic shock. Perhaps the most aggressively studied of these devices is the IABP, with decades of clinical experience and registry data supporting its use. Recent studies attempting to identify optimal candidates for IABP support in high-risk PCI, acute MI, or cardiogenic shock have shown no significant benefit to elective IABP insertion. The CRISP-AMI trial² showed that IABP implantation immediately prior to revascularization for an anterior ST-elevation myocardial infarction did not reduce infarct size or improve short-term survival. The IABP-SHOCK II study³ was another important and large trial that effectively showed that not all patients presenting with an acute coronary syndrome (ACS) with marginal blood pressures and clinical evidence of hypoperfusion should receive an IABP. More recently, a long-term follow-up analysis of the Balloon-pump assisted Coronary Intervention Study (BCIS-1) showed a 34% relative reduction in all-cause mortality with elective IABP use in patients with severe ischemic cardiomyopathy undergoing high-risk PCI.⁴ For the Impella device, the PROTECT II study⁵ was terminated early due to a determination of futility. No difference in major adverse cardiac events was observed between IABP and Impella 2.5 for patients undergoing high-risk PCI. Furthermore, a meta-analysis of smaller studies evaluating these devices for cardiogenic shock showed improved hemodynamic profiles associated with the Impella and TandemHeart devices compared to IABP; however, it showed no impact on short-term mortality.⁶ 

Taken together, these findings suggest the need for a more comprehensive examination of how these devices impact native ventricular function and based on this information, how best to match patients with the appropriate device. For example, a common theme among these trials is that irrespective of the degree of hemodynamic support, short-term mortality is not greatly improved; however, long-term mortality may be impacted positively. Several possible reasons for this observation include: (1) poor selection criteria for identifying device responders versus non-responders; (2) under-powering of studies for these long-term endpoints; (3) variability in terms of the hemodynamic condition for which devices are used (ie, “early shock” versus “late shock” versus “decompensated heart failure”); or (4) different effects of device type, timing of activation, or duration of support on changes in cardiac structure and function. 

As device innovation in the domain of circulatory support continues to expand to include options for the failing right ventricle, interventionalists are now being asked to return to their roots in invasive hemodynamics and think more like heart failure specialists. This potent combination of advanced hemodynamics and device innovation may ultimately yield the best approach to managing patients in the cath lab. Furthermore, beyond circulatory support, the expansion of percutaneous therapies for the advanced heart failure patient including valvular approaches, treatments for heart failure with preserved ejection fraction, and devices designed to alter ventricular remodeling represent important strides toward the development of a community of “interventional heart failure” specialists, who in many ways are part of the natural “evolution” of interventional cardiology as opposed to a “revolution” in the field. 

References

1. Koeckert MS, Jorde UP, Naka Y, Moses JW, Takayama H. Impella LP 2.5 for left ventricular unloading during venoarterial extracorporeal membrane oxygenation support. J Card Surg. 2011;26(6):666-668.
2. Patel MR, Smalling RW, Thiele H, et al. Intra-aortic balloon counterpulsation and infarct size in patients with acute anterior myocardial infarction without shock: the CRISP AMI randomized trial. JAMA. 2011;306(12):1329-1337. 
3. Thiele H, Zeymer U, Neumann FJ, et al; IABP-SHOCK II Trial Investigators. Intraaortic balloon support for myocardial infarction with cardiogenic shock. N Engl J Med. 2012;367(14):1287-1296.
4. Perera D, Stables R, Clayton T, De Silva K, Lumley M, Clack L. Long-term mortality data from the balloon-pump assisted coronary intervention study (BCIS-1): a randomized controlled trial of elective balloon counterpulsation during high risk PCI. Circulation. 2012 Dec 6 (Epub ahead of print).
5. O’Neill WW, Kleiman NS, Moses J, et al. Prospective, randomized clinical trial of hemodynamic support with Impella 2.5 versus intra-aortic balloon pump in patients undergoing high-risk percutaneous coronary intervention: the PROTECT II study. Circulation. 2012;126(14):1717-1727.
6. Cheng JM, den Uil CA, Hoeks SE, van der Ent M, Jewbali LS, van Domburg RT, Serruys PW. Percutaneous left ventricular assist devices vs. intra-aortic balloon pump counterpulsation for treatment of cardiogenic shock: a meta-analysis of controlled trials. Eur Heart J. 2009;30(17):2102-2108.

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Dr. Kapur has clinical expertise in interventional cardiology, advanced heart failure, and the use of mechanical support devices for acute myocardial infarction and cardiogenic shock. He is an Investigator at the Molecular Cardiology Research Institute, the Assistant Director of Interventional Cardiology and Director of the Surgical Research Laboratories, Interventional Cardiology Division at Tufts University School of Medicine in Boston, Massachusetts. Email: nkapur@tuftsmedicalcenter.org

Disclosures: Dr Kapur reports preclinical research support from Heartware Inc and CardiacAssist Inc and speaker honoraria/consultant fees from Maquet and Thoratec Inc.