Measuring the Score: Understanding the Parsonnet and EuroSCORES for Guidance Proceeding With Unprotected Left Main PCI in a High-Risk, Non-Surgical Candidate

Percutaneous coronary intervention (PCI) has emerged as a viable treatment option for left main coronary artery (LMCA) disease. Data show that PCI is particularly safe and effective in low-risk patients, especially in those with angiographically favorable lesions.^1,2 The 2009 American College of Cardiology (ACC)/American Heart Association (AHA)/Society for Cardiovascular Angiography and Interventions (SCAI) focused PCI guidelines state that LMCA stenting can be considered in patients with anatomic conditions that are associated with a low risk of procedural complications and clinical characteristics that may increase the risk of adverse surgical outcomes (class IIb).³ This case involves a patient with a severe lesion in the LMCA that is very amenable to PCI and clinical conditions that made him a high surgical-risk patient who was not a candidate for coronary artery bypass grafting (CABG).

Case Report

A 70 year-old morbidly obese (142 kg) male with multiple medical problems including coronary artery disease with a history of myocardial infarction in the past as well as stable angina, ischemic cardiomyopathy, status post pacemaker placement in 2006 for sick sinus syndrome, diabetes mellitus, hypertension, and chronic renal insufficiency (baseline serum creatinine of 3 mg/dL) presented to a community hospital with severe substernal chest pressure and shortness of breath that began the prior night and did not respond to 2 nitroglycerin tablets at home. Upon arrival to the emergency department, electrocardiography showed a paced rhythm. The first troponin was 0.22 ng/ml. Coronary angiography revealed a subtotal eccentric lesion in the left main coronary artery (LMCA) (Figure 1) and a heavily calcified occluded proximal left anterior descending artery (LAD) with no collaterals (Figure 2). The LMCA supplied perfusion to a long diagonal branch, long ramus intermedius, and left circumflex artery (LCX). The right coronary artery (RCA) had mild, diffuse disease. The ejection fraction was 35%. An intra-aortic balloon pump (IABP) was placed because of cardiogenic shock. Cardiac surgical consultation deemed the patient was too high an operative risk. His hospital course was complicated by methicillin-resistant staphylococcus aureus septicemia and E. Coli urinary tract infection which were successfully treated with antibiotics, and worsening renal failure, which returned back to baseline. IABP was continued for 10 days because of the need for prolonged hemodynamic support. The patient was then transferred to UCLA Medical Center for percutaneous revascularization of the LMCA. After prasugrel and aspirin were given, unfractionated heparin was administered to attain an activated clotting time of 250 seconds. A 6 Fr Q3.5 guiding catheter (Boston Scientific, Natick, Mass.) was used to engage the LMCA. A 0.014-inch Balance guidewire (Abbott Vascular, Redwood City, Calif.) was advanced across the LMCA into the proximal LAD and into the diagonal branch. After predilatation, a 4.0 x 20 mm Taxus Liberte stent (Boston Scientific) was precisely positioned at the ostium of the LMCA in the left anterior oblique (LAO)-cranial view with 1 to 2 mm of stent struts protruding into the aorta (Figure 3) and deployed at 16 atmospheres for 5 seconds, covering the ostium and midshaft, but just proximal to the distal bifurcation. The stent was post-dilated with a 4.0 x 15 mm Voyager NC balloon (Abbott Vascular) that was inflated at 16 atmospheres for 5 seconds, at which time the blood pressure briefly decreased by 30 mmHg. The blood pressure was promptly returned to baseline when the noncompliant balloon was deflated and removed from the LMCA. Final angiography revealed TIMI-3 flow and a well-apposed stent with no evidence of dissection (Figures 4 and 5). At the conclusion of the procedure, an iliofemoral angiogram revealed that the sheath entry point was above the bifurcation and below the infra-epigastric artery, and therefore, a 6 French Angio-Seal hemostasis device (St. Jude Medical, Minnetonka, Minn.) was deployed with good hemostasis. The patient was discharged from the hospital the following day.

Discussion

The decision to perform CABG or PCI for patients with LMCA disease may be a difficult one. A multidisciplinary approach with a “Heart Team” which includes a cardiac surgeon and interventional cardiologist should help the patient make an informed decision after hearing the risks and benefits of both revascularization strategies. Risk stratification with predictive models prior to revascularization is an integral part of the pre-procedural evaluation of patients who are being considered for LMCA revascularization. Predictive models provide the cardiologist, cardiac surgeon, and patient the potential risks of either revascularization strategy during the consent process. The Parsonnet score, which incorporates patient- (including age, sex, diabetes, hypertension, morbid obesity, dialysis, and catastrophic states like cardiogenic shock) and cardiac-related factors (including reoperation, emergent need for surgery, ejection fraction, pacemaker dependency, preoperative IABP status, and need for concomitant need for valve surgery), is typically used to risk-stratify surgical revascularization candidates, but has been identified as a significant predictor of major adverse cardiac and cerebrovascular events in patients who underwent LMCA PCI with drug-eluting stent (DES).⁴ The Parsonnet score can be calculated online at https://www.sfar.org/scores2/parsonnet2.html. This patient’s calculated Parsonnet score revealed a predicted 34% probability of operative mortality. The EuroSCORE incorporates patient- (including age, sex, renal function, and any critical preoperative state like IABP counterpulsation), cardiac- (including left ventricular function and the presence of unstable angina), and operation-related factors, and is a method of calculating predicted operative mortality for patients undergoing cardiac surgery. The EuroSCORE can also be calculated online at https://www.euroscore. org/euroscore_scoring.htm. The patient’s EuroSCORE was 12. A EuroSCORE ≥ 6 was an independent predictor of mortality in patients with LMCA disease who underwent PCI or CABG.⁵ Given the high mortality risk with CABG, the LMCA lesion was in the ostium/midshaft, did not involve the distal bifurcation, and PCI could be successfully performed with only 1 stent with a high likelihood of technical success, the consensus was that LMCA PCI was preferred over CABG. The Society of Thoracic Surgeons Predicted Risk of Mortality (STS) score was calculated on the STS website (https://209.220. 160.181/STSWebRiskCalc261/de.aspx). The risk of mortality was 31.9%, morbidity or mortality was 85.5%, and permanent stroke was 4.0%. The SYNTAX score, which only incorporates angiographic data and predicts safety and efficacy outcomes in patients with LMCA disease undergoing PCI or CABG, was 35.⁶ Patients with LMCA disease and a SYNTAX score ≥ 33 treated with PCI had higher rates of repeat revascularization (27.7% vs. 9.2%, p7 However, PCI was chosen because of the unfavorable coronary anatomy (the LAD was occluded and the only potential vessels to be bypassed were the diagonal branch and ramus intermedius), as well as the multiple medical co-morbidities, and the cardiac surgeon felt the patient was not a candidate for CABG. Prior to PCI, the patient confirmed his willingness to take all his medications and there were no impending surgical or dental procedures, or any financial burden that would preclude uninterrupted dual antiplatelet therapy for at least 1 year. One of the reasons why prasugrel was chosen over clopidogrel in this patient was because of the superior outcomes of prasugrel, especially in diabetic patients. The diabetic subgroup of patients in the TRITON-TIMI 38 trial had almost a 5% absolute risk reduction in the primary end point of cardiovascular death, myocardial infarction, and nonfatal stroke (12.2% vs. 17.0%; hazard ratio [HR], 0.70, p8 Furthermore, he did not have a contraindication to prasugrel like a history of stroke/transient ischemic attack, age ≥ 75 years, or body weight 1 year) dual antiplatelet therapy, the decision was made to perform PCI with a DES rather than a bare-metal stent (BMS). A meta-analysis comparing LMCA PCI with DES and BMS (n = 5,081) reported that treatment with a DES reduced 3-year rates of death (odds ratio [OR] 0.70, 95% confidence interval [CI] 0.53-0.92, p = 0.01), myocardial infarction (OR 0.49, 95% CI 0.26-0.92, p = 0.03) and repeat revascularization (OR 0.46, 95% CI 0.30-0.69, p 9 The randomized ISAR-LEFT MAIN trial reported similar rates of angiographic restenosis at 6 to 9-month follow up after LMCA PCI with either sirolimus-eluting stents (SES) or paclitaxel-eluting stents (PES) (19.4% vs. 16.0%, p = 0.30) and target lesion revascularization at 2-year follow up (10.7% vs. 9.2%, p = 0.47).¹⁰ Although the SPIRIT IV trial reported a lower rate of target lesion failure (cardiac death, target-vessel myocardial infarction, or ischemia-driven target lesion revascularization) at 1 year with everolimus-eluting stents (EES) as compared with PES (4.2% vs. 6.8%, p = 0.001),¹¹ there were no differences among diabetic patients (6.4% vs. 6.9%, p = 0.80) or any of its components, regardless of insulin use.¹² Furthermore, there was no significant difference in target lesion failure when the reference vessel diameter was greater than 2.75 mm.¹¹ Given that there are no data supporting the superiority of EES in diabetic patients as well as large reference vessel diameters as compared with PES, and the fact that a 20-mm stent was the ideal length for the LMCA PCI in this particular case (18-mm EES was felt to be too short and a 23-mm EES was felt to be too long), a Taxus stent was used. Data suggest that LMCA PCI with DES is safe and effective. The risk of in-stent restenosis after LMCA PCI involving the ostium or midshaft is low. The rate of target lesion revascularization was 0.7% at long-term follow up.² The overall 2-year rate of Academic Research Consortium-defined definite stent thrombosis rate in patients who underwent LMCA PCI was 0.5% at 2-year follow up.¹⁰ Intravascular ultrasound (IVUS) plays an integral part in LMCA PCI, as it provides invaluable information prior to stenting regarding plaque distribution, bifurcation involvement, and vessel size. Post-stent deployment, IVUS can assess for adequate stent expansion and apposition to minimize the risk of restenosis and stent thrombosis. Two nonrandomized studies reported improved overall survival and event-free survival, respectively, with the use of IVUS during LMCA PCI.^13,14 However, in this high-risk patient, without the hemodynamic support of an IABP or left ventricular assist device, and an occluded LAD, the decision was made not to perform IVUS, but instead perform “hit-and-run” PCI with high-pressure balloon inflations with a non-compliant balloon to ensure full stent expansion and apposition. Although it would have been ideal to confirm that stent struts covered the ostial LMCA with IVUS, positioning of the stent in the LAO-cranial projection provided good reassurance that at least 1 to 2 mm of stent struts protruded into the aorta proximal to the inferior ostial aspect of the LMCA. Routine surveillance angiography after LMCA PCI has not been proven to provide a clinical benefit. Its performance may lead to unnecessary target vessel revascularization, especially with the “oculo-stenotic reflex” and if hemodynamic assessment with fractional flow reserve is not performed. The ACC/AHA/SCAI 2009 PCI guidelines no longer recommend routine follow-up angiography after LMCA PCI.³ However, non-invasive assessment of ischemia should be performed at 6 months (or sooner if there is clinical suspicion of ischemia) and annually thereafter. Over the past decade, the dramatic improvement in pharmacotherapy (new thienopyridines), stent technology (DES), and PCI technique, as well as data showing favorable outcomes with surgical revascularization, have resulted in enthusiasm for PCI as an alternative revascularization strategy in selected patients with LMCA disease. With careful patient selection and meticulous pre-PCI planning, LMCA PCI is feasible and can be performed safely with low risk of stent thrombosis even in high-risk patients. Long-term efficacy of LMCA PCI of the ostium or midshaft with DES is excellent with low rates of in-stent restenosis and target lesion revascularization. In high-risk patients who do not have hemodynamic support, PCI can be performed expeditiously in angiographically favorable lesions. Dr. Lee can be contacted at MSLee@mednet.ucla.edu Disclosure: Dr. Lee reports that he consults for Boston Scientific, Bristol-Myers Squibb, Merck, and St. Jude Medical. This article received a double-blind peer review from members of Cath Lab Digest’s editorial board.

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