Cardiovascular Risk Profile, Presentation and Management Outcomes of Patients with Acute Coronary Syndromes after Coronary Artery Bypass Grafting

Abstract

Background: Coronary artery bypass (CABG) is an important revascularization procedure with excellent long-term results. However, bypass grafts, particularly venous grafts, develop structural changes and atherosclerotic plaques that may cause angina or even acute coronary syndromes (ACS). Here we aimed to study patients with previous CABG presenting with an ACS and evaluated their cardiovascular (CV) risk profile, clinical presentations, angiographic findings, management strategies and short and long term outcomes.

Patients and methods: This represents an observational retrospective cross sectional single center study including all consecutive patients with previous CABG presenting with ACS at the University Heart Center of the University Hospital Zurich, Switzerland between January 1, 2000 and December 31, 2016. Mean age was 76.4 years and 83.1% were males, 60.2% were diabetics and 58.6% obese, 43.5% hypertensives and 37.8% had hyperlipidemia. Major adverse cardiovascular and cerebrovascular events (MACCE) at 1-year and long-term follow up were analyzed using Kaplan Meyer survival analysis.

Results: We included 510 patients with ACS and prior CABG. 73% (n=372) presented as unstable angina (UA), 22.5% as NSTEMI (n=115) and only 4.5% as STEMI (n=23). Acute events during the index hospitalization occurred in 4.9% (n=25) before discharge, in 4.9% (n=25) within the first year and in 90.2% (n=460) thereafter. Most patients (92.2%; n=470) had stenosed or occluded venous bypass grafts at presentation, while a minority (7.8%; n=40) had significantly narrowed or occluded arterial grafts. CV risk profiles were similar in both groups. However, arterial graft disease occurred earlier after CABG and more likely presented as NSTEMI rather than UA compared to the SVG group. In 54.7% (n=279) primary PCI of the saphenous graft, and in 13.5% (n=69) of the native coronary arteries was performed, while 6.5% (n=33) underwent redo CABG and 25.3% (n=129) received medical treatment only. MACE at 1 year occurred in 12.2% (n=62) with repeated revascularization as the most common event (7.2%; n=37) followed by cardiac death (2.4%; n=12), MI (1.2%; n=6), cerebrovascular infarction (1.2%; n=6) and major bleeding (0.2%; n=1). Hypertensive and obese patients, those with myocardial infarction or an ACS before discharge or during the first year after CABG had higher MACCE. In patients undergoing pPCI the rate of cardiac death and MI at 1 year was lower with an intervention in the native coronary arteries and with redo CABG compared to pPCI of bypass grafts.

Conclusion: Thus, patients with ACS and prior CABG typically present as UA and much less frequently as NSTEMI-ACS and rarely as STEMI. Most events occur after one year, particularly with SVG. The 1 year MACCE rate is comparable to those with native coronary artery ACS. Hypertensive and obese patients, those with MI or with an ACS before discharge had higher MACCE rates.