PCI in the patient with severely depressed ventricular function

# Overview
Heart failure (HF) is a major public health problem. In the United States, 5 million patients have heart failure and annually more than one million are hospitalized with heart failure. In addition 50,000 patients die of heart failure in the United States. Coronary artery disease (CAD) is the most common cause of heart failure as a result of left ventricular systolic dysfunction (60-68%). There are no randomized studies to evaluate the best strategy to manage coronary artery disease in this patient population. However, there are a number of registry studies that evaluated percutaneous coronary intervention (PCI) and coronary artery bypass surgery (CABG) in patients with coronary artery disease and heart failure.

# Mechanism of Functional Recovery after Revascularization
Patients with HF can have hibernating or stunned myocardium. Hibernating myocardium in chronically dysfunctional tissue related to inadequate myocardial blood flow. Stunned myocardium refers to dysfunction in viable myocardium related to transient ischemia. Previous studies have demonstrated that both hibernating myocardium and stunned myocardium can lead to left ventricular systolic dysfunction, remodeling and eventually development of heart failure. Chareonthaitawee et al demonstrated that 60% of ischemic LV dysfunction is related to dysfunctional but viable myocardium. Stunned and hibernating myocardium could potentially be improved by revascularization by optimizing perfusion into the myocardium.

# Role of PCI
The benefit of PCI in patients with heart failure related to stunned myocardium has been studied in observational studies. Keelan et al subdivided patients undergoing PCI in HF into 3 categories: group 1, ejection fraction (EF) 40%; group 2, EF 41% to 49%; and group 3, EF 50%. The respective mortality rates were 11.0%, 4.5%, and 1.9% (p <0.001) after 1 year. The composite end points of death/ myocardial infarction (MI) and death/ MI/ CABG occurred more frequently among patients in group 1. Thus, significant LV dysfunction was still associated with increased in-hospital and 1-year mortality in patients having contemporary PCI.
The GRACE (Global Registry of Acute Coronary Events) Registry demonstrated that the 6-month mortality was significantly lower in the PCI treated group compared to the medical therapy group (14% vs. 23.7%, p=<0.0001). PCI in chronic total occlusion in the setting of HF has been shown to be beneficial. Stenting can be safely performed in patients with HF with acceptable late adverse events.
A previous study demonstrated that patients with left ventricular ejection fraction (LVEF) 40% had better survival at 5 years if they received a stent compared with balloon angioplasty alone (76% for stents vs. 53% for balloon angioplasty; p<0.05). Stenting was found to be significant predictor of late survival in patients with an LVEF 50% and LVEF 40%. This study demonstrates improved 5-year survival for patients undergoing stenting compared with balloon angioplasty in patients with LVEF 40%.
A recent study compared PCI using drug eluting stents (DES) and CABG. The 2 years major adverse cardiac and cerebrovascular events free survival rate was 76% in DES group and 79% in the CABG cohort (p=NS). The same group demonstrated that DES reduced mortality and MACE compared to bare metal stents. MACE rate was 10% for the DES group and 41% for the BMS group (P = 0.003).

# Surgical Revascularization
The State University of New York study suggested that patients with HF who underwent PCI had better outcomes than patients who underwent medical therapy. Over the last decade management of patients with significant heart failure has improved significantly. Better medical management strategies using statins, angiotensin converting enzyme inhibitors and the use of implantable defibrillators and cardiac resynchronization therapy have significantly improved the outcome of patients with . PCI has also seen significant advance in recent years with availability of drug eluting stents, intra-aortic balloon pump support and the use of low osmolar non-ionic contrast media which reduces the incidence of renal failure in patients with heart failure. Hence large randomized clinical studies in the modern era are required to determine the best revascularization strategy for patients with heart failure. There are currently three randomized trials are underway to evaluate the effect of revascularization in patients with ischemic dysfunction (STICH trial, HEART trial and PARR-2 trial).

# The Role of Viability Testing
Viability studies could be beneficial in identifying patients who will benefit from revascularization. Viability can be assessed by single photon emission computed tomography (SPECT), positron emission tomography (PET), dobutamine stress echocardiography and cardiac magnetic resonance imaging (CMR). Among patients who demonstrated viability the 1-year mortality was 16% in patients who underwent medical therapy and 3.2% in those who underwent revascularization. There was no difference in mortality in those who did not demonstrate viability. CMR is now emerging as a gold standard for viability testing, but further studies are required to compare CMR viability to clinical outcomes.

# Patient Selection for PCI
PCI and CABG should be considered as complimentary rather than competitive treatment for patients with heart failure. PCI could be considered in patients with focal stenosis, patients who have had prior CABG, with concomitant co-morbidities and advanced age. CABG should be considered in patients with diffuse disease pattern, complex lesions including chronic total occlusions and patients who require concomitant mitral valve surgery.