7.1 Circulatory Support for Complex, High Risk PCI: How to Predict Who Benefits

These proceedings summarize the educational activity of the 17th Biennial Meeting of the International Andreas Gruentzig Society held January 30 to February 2, 2024 in Chiang Rai, Thailand.

Faculty Disclosures     Vendor Acknowledgments

2024 IAGS Summary Document

Statement of the problem or issue

There are three very important issues in this field. First is oxygen supply to the myocardium, which is determined by myocardial perfusion pressure, or coronary diastolic pressure minus LV end-diastolic pressure (LVEDP). Second is oxygen demand of the myocardium, which is defined by pressure-volume (PV) loop area. Third is whole body circulation, which is determined by cardiac power product (CPO), or cardiac output multiplied by mean arterial blood pressure (MBP), then divided by 451 (See Figure 1). Normally, CPO is >1. Normal coronary perfusion pressure is typically between 60-to-80 (or, approximately 72 as shown in Figure 1.

Figure 1. Important concepts in circulatory support.

Typically, in high-risk PCI, we are concerned about creating a vicious cycle of myocardial ischemia with resultant loss of coronary perfusion pressure and then reduction in CPO, leading to further loss of perfusion pressure and more reduction in CPO (Figure 2). This phase may happen when CPO becomes less than <0.6, the point where reduced systemic circulation leads to reduced coronary perfusion. If this continues, a point can be reached where CPO becomes <0.53, beyond which the spiral may be irreversible and tragically end in death. Patients with already-reduced CO and MBP, for example, those with heart failure (HF) or low ejection fraction (EF), frequently require measures that increase CO and MBP.

Figure 2. The vicious cycle of myocardial perfusion, ischemia, and CPO.

Gaps in current knowledge

Our gaps in knowledge center around understanding which patients are “high-risk,” which device is best suited to which patient, and when (the timing) of mechanical circulatory support (MCS) is appropriate. Additionally, we need to differentiate between patients who suffer predominantly from inadequate coronary circulation, for example a sole surviving coronary artery or left main disease but with normal LV function, and those patients who have both severe coronary disease and hemodynamic compromise. The choice and timing of MCS will differ accordingly.

Figure 3. Currently available mechanical circulatory support devices.

Possible solutions and future directions

It will be important to develop an individual risk profile for each patient. Broadly speaking, we might consider this to consist of coronary anatomic risk for the PCI procedure, and then in addition consider risk associated with overall patient complexity (Figure 4). There can be high-risk anatomy, but in a low-risk patient, because circulation is okay (normal LVEF). Or, there can be high-risk anatomy in a high-risk patient. Finally, there can be low-risk anatomy, but in a high-risk patient, perhaps because of comorbidities or markedly reduced LVEF. Developing an individual decision aid algorithm which incorporates all these data to help determine whether any MCS is required at all, and if so, which one, is crucial.

Figure 4. Concepts of anatomic risk and patient risk.

In the future, as we refine these concepts and learn more about device characteristics and how to match them to patient risk, we can expect much smoother PCI procedures for the complex, high-risk patients. Furthermore, better left ventricular assist devices will be developed, like a miniaturized percutaneously delivered artificial heart which would completely support the systemic circulation, perhaps even allowing interventional procedures to be done with greater precision and at complete leisure. I will end with a diagram of the vicious cycle of ischemia-coronary perfusion-CPO and indicate some potential points where various available MCS devices might be employed (Figure 5).

Figure 5. Points of intervention with MCS devices.

References

1. Mishra S, Chiu W, Wolfram R. Role of prophylactic intra-aortic balloon pump in high-risk patients undergoing percutaneous coronary intervention. Am J Cardiol. 2006;98(5):608-612. doi: 10.1016/j.amjcard.2006.03.036. PMID: 16923445.
2. Naidu SS. Novel percutaneous cardiac assist devices. The science of and indications for hemodynamic support. Circulation. 2011;123(5):533-543. doi: 10.1161/CIRCULATIONAHA.110.945055. PMID: 21300961.
3. Mishra S. Upscaling cardiac assist devices in decompensated heart failure: choice of device and its timing. Indian Heart J. 2016;68 (Suppl 1):S1-4. doi: 10.1016/j.ihj.2015.12.012. PMID: 27056646.