IABP Use: Do We Need to Think More Like Heart Failure Specialists?
- Volume 20 - Issue 12 - December 2012
- Posted on: 12/6/12
- 0 Comments
- 5610 reads
You have a unique perspective on mechanical circulatory support. Can you tell us about your background?
I am an interventional cardiologist with advanced training in heart failure and cardiac transplantation. My background in heart failure certainly influences how I approach patients in the cath lab. On the heart failure service, we think about hemodynamics all the time, because that is how we guide patient therapy. Similarly, as an interventionalist, the root of our practice is founded in a comprehensive appreciation for invasive hemodynamics. Since Tufts has a large cardiac transplant and ventricular assist device (VAD) program, our patient population tends to be people with early or late stage heart failure from various causes, anything from inherited myopathies all the way to acute myocardial infarction (MI). For this reason, we have developed an interdisciplinary interventional/heart failure (IHF) team approach that allows us to implement a gamut of mechanical support devices, both percutaneous and surgical, when necessary. For the past five years, when selecting a percutaneous ventricular support device (Figure 1), we have used a decision-making algorithm that blends interventional criteria, like coronary anatomic risk, clinical characteristics, acute MI and acute coronary syndromes (ACS), and heart failure characteristics such as hemodynamic assessment, New York Heart Association (NYHA) class, and Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) class1.These multi-disciplinary evaluations often involve our interventionalists, advanced heart failure specialists, and cardiac surgeons.
My particular expertise focuses on mechanical support devices, cardiac remodeling, and the development of the IHF program at Tufts. The IHF program is a great example of interdisciplinary work leading to better patient care, because decisions often have to be made acutely in the cath lab and having a system in place to rapidly discuss complex patient scenarios, if necessary, is helpful. Everyone, including our technologists and nurses, who are an important part of the IHF team, recognizes that whether we are implanting a mechanical support device, performing a high risk coronary intervention in a patient with advanced heart failure, percutaneously treating an aortic or mitral valve, performing a septal alcohol ablation procedure, or interrogating a patient’s hemodynamic status. We are constantly asking: what is the root cause of their heart failure and what is the best approach to stabilize and improve their quality and quantity of life?
Can you tell us more about the algorithm you use to assess patients for high risk PCI?
For high risk coronary interventions, our algorithm involves four main criteria:
- Assessing the patient’s coronary anatomy, thereby laying out realistic expectations of how difficult the procedure may be;
- Determining the amount of myocardium at risk in a coronary territory;
- Considering other aspects of the patient’s characteristics such as ejection fraction and clinical presentation — is it acute MI, is it ACS, or is it purely an elective percutaneous coronary intervention (PCI)?;
- Determining the hemodynamic status of the patient at the time of PCI (perhaps one of the most important criteria).
In most complex PCI cases, we first assess cardiac filling pressures and function with a pulmonary artery (PA) catheter or at minimum, a pigtail left ventricular end diastolic pressure (LVEDP) measurement. If we find that the patient has massively elevated cardiac filling pressures and if it is an elective or semi-elective procedure, we will often opt to diurese the patient, seeking to normalize their hemodynamics as much as possible, before making the myocardium ischemic during a potentially high-risk coronary intervention. For example, if you take a patient who comes in with a LVEDP of 40 who needs to have a PCI done, that makes the procedure considerably higher risk than if the LVEDP is 10, even if each patient has the same ‘high-risk coronary anatomy’. This is because the first effect of ischemia is to increase LVEDP, or cardiac filling pressures, which can lead to congestion, heart failure, cardiogenic shock, etc.
Percutaneously delivered mechanical support devices are designed to minimize the workload of the heart, by reducing LV pressure and volume, while sustaining systemic perfusion when cardiac function is impaired. For this reason, patients who have low filling pressures and preserved cardiac function may not benefit from a mechanical support device. As I noted, we evaluate the patient from a coronary/anatomic risk perspective, from a clinical presentation perspective, and then also from a heart failure perspective (or a hemodynamic assessment of the patient). If the patient is fortunate enough to only require elective or semi-elective PCI, we will try to optimize their condition with medications and potentially bring them back when they are in better shape. If there is a mandate or need to do the intervention at that time and their hemodynamic status is deranged, as in the case of an acute MI presenting with decompensated heart failure, then we will consider pre-procedural implant of an IABP in those patients. We commonly use an IABP for patients with decompensated heart failure, high-risk PCI, as well as for cardiogenic shock, because of its ease of implantation and global familiarity with the device and how it is used. I also like IABPs because they do not penetrate the heart, whereas other support options require cannulation of the left atrium or left ventricle (Figure 2). Often we find that we do not need to advance beyond an IABP for a more aggressive mechanical support device. One caveat is that if a patient has severely impaired cardiac function and meets high-risk criteria in several of the areas we are measuring: coronary anatomy, clinical presentation and hemodynamics, then there are occasions where we will skip an IABP and go directly to an Impella device (Abiomed), and more rarely, to a TandemHeart device (CardiacAssist), for high-risk PCI. In cardiogenic shock, whether it is an acute MI or not, our general practice is to first put in an IABP. However, if we do not see clinical or hemodynamic improvement with IABP implantation, meaning that the patient is now considered to be in ‘balloon pump refractory cardiogenic shock’, we will then quickly move to a more aggressive mechanical support device, like an Impella device or a Tandem device. The key for most patients with impaired LV function presenting with cardiogenic shock is to assess the hemodynamic status of the patient first and then to take a stepwise approach in escalating mechanical support options beginning with an IABP, then moving towards more aggressive support systems as needed.
What is your take on where we are headed with IABP use?
The field of mechanical circulatory support in the cath lab has a long history, but it seems to be renewing itself. The IABP represents one of the original devices that came out for this purpose, but since then, there have been several other devices that are now widely available, including the Impella and TandemHeart devices, and extracorporeal membrane oxygenation (ECMO).
The IABP, for a long time, dominated the field, especially in the cath lab, because it was easy to implant and there were limited alternatives available. But over the past two decades, with the emergence of the Impella device and the TandemHeart device in cath labs around the world, it has become clear that there is no algorithm to guide use of these devices and worse, no consensus as to how these devices impact left ventricular function. Who should get what device and why we would choose one device over another remains poorly understood. Furthermore, most trials exploring the clinical utility of these devices for high risk PCI or cardiogenic shock do not show mortality benefit for the use of percutaneous mechanical support. The issue is made more complicated since most interventional operators have experienced clinical scenarios where an IABP, Impella, TandemHeart, or ECMO system has saved a patient who otherwise might have died. For this reason, the science behind mechanical support requires further exploration.
Clinically, cardiology is also changing. With advances in coronary intervention, we have essentially traded one disease for another. Nearly 25% of patients who survive an acute MI go on to develop chronic ischemic heart failure. As a result, we are experiencing a tsunami of heart failure patients that are increasing in numbers in the United States and around the world. Historically, in the 1960s and 1950s, the patients would come in with a heart attack, they would be treated medically and as a result, in-hospital mortality rates were about 50%. However, with advances in balloon angioplasty, medical therapy, drugs, etc., there is now a larger population of patients who survived their heart attack and now have heart failure. As an estimate, out of 300 million individuals in the U.S., about 2.6% have heart failure (7.8 million people). Fifty percent of this heart failure population has impaired contractile function or systolic heart failure (3.9 million people), and about 550,000 of those patients have advanced heart failure, meaning they are in NYHA class IIIb or IV. Eventually, this population of heart failure patients will be likely to show up in a cath lab.