Primary Angioplasty in ST-Elevation Myocardial Infarction Due to Unprotected Left-Main Coronary Disease in a High-Volume Catheterization Center Without On-Site Surgery Facilities: Immediate and Medium-Term Outcome: The STEMI-Placet Registry

Abstract: Background. Very few data have been published for ST-elevation myocardial infarction (STEMI) caused by unprotected left main coronary artery (ULMCA) and very little is known about the results in this subgroup of patients in a hospital with high-volume catheterization laboratories (cath labs) without on-site cardiosurgery. Methods and Results. From January 2004 to December 2009, a total of 38 patients with evolving STEMI and ULMCA as the culprit lesion treated with primary angioplasty were enrolled in our registry. Despite dramatic clinical presentation (73.7% cardiogenic shock, 15.8% cardiac arrest and resuscitation maneuvers, 81.6% additive EuroSCORE >13, and 89.5% distal bifurcation involvement), angiographic success was obtained in 84.2% and final TIMI 3 flow was achieved in 34 (89.5%), while target lesion failure occurred in 47.4% (mostly [42.1%] during the in-hospital phase). Most of the patients discharged from hospital had no events at follow-up (47.4%), and notably no target lesion revascularization was required during the follow-up phase. Conclusions. Primary angioplasty in patients presenting with ULMCA as the culprit lesion in a STEMI setting appears to be technically feasible and a good alternative to surgical revascularization. Mortality in this group of patients tends to be high, but lower than mortality of untreated patients; the majority of events are concentrated during the in-hospital phase. Procedural delay related to activation of operator’s staff in off-duty hours doesn’t correlate with a worse prognosis.

J INVASIVE CARDIOL 2012;24:645-649

Key words: PPCI, primary angioplasty, STEMI, ULMCA

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“Primary” angioplasty (PPCI) is the preferred reperfusion strategy in acute myocardial infarction (AMI) with electrocardiographic ST elevation at presentation (STEMI),¹ but very few data have been published for STEMI with unprotected left main coronary artery (ULMCA) as the culprit lesion. Recent guidelines¹ consider coronary artery bypass graft (CABG) the preferred revascularization strategy for ULMCA disease, but patients with STEMI due to ULMCA occlusion were excluded in most of the published trials.² Recently, some preliminary registries have shown acceptable results with PPCI in ULMCA-STEMI,^3,4 suggesting a more favorable outcome when compared with historical surgical data,⁵ but most of the studies were performed in tertiary hospitals with on-site cardiac surgery (CCH); hence, very little is known about the in-hospital results of high-volume catheterization laboratories (cath labs) without on-site CCH which is the most common situation in northwest Italy.

Methods

We retrospectively analyzed all patients admitted to our hospital with a STEMI diagnosis between January 2004 and December 2009; a dedicated database (Cardioplanet, EBIT-AE, IT) was used to obtain clinical and procedural data and a committee-based (authors Romagnoli and Gagnor) clinical event  was used for endpoint adjudication. All angiograms were reviewed to assess primary involvement of ULMCA, percutaneous coronary intervention (PCI) technique, and procedural details. Thirty-eight patients with evolving STEMI and ULMCA as the culprit lesion treated with primary angioplasty were enrolled in our registry; patients were eligible if the inclusion criteria (typical chest pain >30 minutes and <12 hours with ST-segment elevation in at least two contiguous electrocardiographic leads or a new left bundle branch block and ULMCA as the definite culprit lesion) were satisfied. Due to the lack of an on-site cardiothoracic surgical team at our institution, the decision to perform PCI instead of CABG was primarily dependent on hemodynamic stability of the patient, high surgical risk (eg, critically ill condition), and the technical feasibility of the percutaneous procedure; in these patients, PCI was performed because of the unacceptable delay in reaching the nearest cardiac surgery for bypass surgery in such an emergent setting.

Definitions. Cardiogenic shock was defined as systolic blood pressure persistently below 90 mm Hg. Coronary flow was defined according to TIMI grade.⁶Procedural success was defined as <30% residual stenosis, and TIMI 3 flow without patient death or in-hospital target lesion failure (TLF). Significant disease in vessel different from ULMCA was defined as >50% stenosis. Cardiac death was defined as any death due to cardiac cause, procedure-related deaths, and death of unknown cause. MI was defined as any elevation of creatine-kinase level or its MB isoenzyme to 3 times the upper normal limit.⁷Target lesion revascularization (TLR) was defined as any revascularization procedure performed because of angiographic restenosis at the site of the lesion treated associated with clinical and/or objective evidence of inducible myocardial ischemia. Stent thrombosis was classified according to Academic Research Consortium Classification.⁸ Procedure strategy (thrombus aspiration, balloon dilatation, stent selection, use of intra-aortic balloon pump, and anticoagulation regimen) was left to operator discretion. If not clinically contraindicated, the intravenous use of glycoprotein IIb/IIIa inhibitors (mainly abiciximab) was recommended, particularly in patients presenting in cardiogenic shock, under resuscitation maneuver, orotracheal intubation, or in which an adequate platelet inhibition was not likely to be obtained with oral therapy. In patients with orotracheal intubation and unable to assume dual antiplatelet therapy, both aspirin and clopidogrel were administrated in a nasogastric probe. Additive EuroSCORE was adopted to assess the cardiac surgical or percutaneous mortality risk.^9,10

Door-to-balloon time was defined as time from first medical contact to coronary flow restoration. Endpoints were: (1) death for any cause during hospitalization; (2) death for any cause at follow-up; and (3) TLF, defined as death from cardiac cause, MI attributable to the target vessel, or clinically driven target vessel revascularization (TVR). In a sensitivity analysis, we separately evaluated the cohort of patients undergoing ULMCA PCI during on-duty versus off-duty hours.

All survived patients with no clinical contraindications were scheduled for angiographic follow-up at 6 months. Clinical follow-up data were obtained from outpatient clinic visit or direct telephone contact. The follow-up period began at the moment of hospital discharge.

Statistical analysis. All continuous results are presented as mean ± standard deviation (SD). Chi-square and unpaired student’s t-tests were used to compare ordinal and continuous variables, respectively. A P-value <.05 was considered statistically significant. Survival curves were generated using Kaplan-Meier methods. No multivariate analyses were performed due to small sample size.

All statistical analyses were carried out using SPSS-PASW 18.0 (IBM).

Results

During the observed period, thirty-eight patients with STEMI due to ULMCA occlusion were treated; demographic and clinical characteristics are listed in Table 1 and procedural data are presented in Table 2. The mean age of patients was 67.7 ± 11.45 years (68.1 ± 13.1 years for the on-duty subgroup vs 67.4 ± 9.7 years for the off-duty subgroup; P=.85), 73.7% were males, and diabetes was present in 21.1%; males were slightly more represented in the off-duty population (P=.02). Fifty percent of the procedures were performed during off-duty hours. Most of the patients (73.7%) presented in cardiogenic shock (15.8% with cardiac arrest and during resuscitation maneuvers) with no differences between the two selected populations, 34.2% had orotracheal intubation before or during the PPCI, and intra-aortic balloon pump (IABP) was used in 94.7%. Logistic EuroSCORE was 57.4 ± 21.3, additive EuroSCORE was 15.7 ± 2.9, and additive EuroSCORE >13 was present in 81.6%. 

Most of the patients presented with distal bifurcation involvement (89.5%) and this presentation was more frequent in the on-duty population (P=.03); 28.9% had TIMI 0 flow and 47.4% had TIMI 3 flow at presentation; no difference according to TIMI flow at presentation was observed (P=.2). Anatomycomplexity was well underlined by Syntax score¹¹ (30.7 ± 8.8); no difference in the two populations was detected (28.9 ± 8.1 on-duty vs 32.4 ± 9.3 off-duty; P=.65). No differences in the two groups were observed according to door-to-balloon time (71.9 ± 55.9 minutes for on-duty vs 92.8 ± 58.0 minutes for off-duty; P=.41). All patients except 1 were treated with stents, with a relative high percentage of bare-metal stent usage (36.8%). Final kissing balloon was more frequently performed in the on-duty subgroup (14 vs 4; P=.009). Complete revascularization was achieved in only 63.2% of patients, and intravascular ultrasound and thrombus aspirators were used in a minority of patients (2.6% in the on-duty group and 10.5% in the off-duty group). Immediate angiographic success was obtained in 84.2% and final TIMI 3 flow was achieved in 34 patients (89.5%). In-hospital and follow-up outcomes are listed in Table 3. Mean follow-up was at 504 ± 653 days; death occurred in 44.7% (42.1% in-hospital). TLF occurred in 47.4% (42.1% in-hospital) and stent thrombosis in 7.9% (5.3% in-hospital). Clinical follow-up was accomplished in 100% of cases while angiographic follow-up was performed in 63.6% of patients. 

Most of the patients discharged from hospital had no events at follow-up (47.4%), and notably no TLR was required during the follow-up phase. No differences between the two populations were observed for the specified endpoints. Kaplan-Meier survival curves for death and TLF are shown in Figures 1 and 2.

Discussion

Our data refer to a single-center experience with high activity volume (more than 900 angioplasties [PCIs] per year), with three dedicated operators, and without on-site cardiac surgery but with surgical back-up by 30 minutes ambulance travel. Due to geographical and economical reasons (ie, a very diffuse distribution of cath labs, but a high concentration of cardiac surgery facilities), most of the PPCIs in our region are treated at centers without on-site cardiac surgery; in 2009, we performed more than 900 PCIs and more than 200 PPCIs at our center (results described elsewhere).¹² STEMI due to ULMCA occlusion is relatively frequent (3.8% in our registry, 0.8%-2.5% in previously reported data)^13-16 and correlates with a very poor clinical status at presentation with a high percentage of cardiogenic shock (73% in our registry vs 64.2% in the literature),¹⁴ high EuroSCORE, and high mortality rate¹⁵ (up to >50%).¹⁶

It is well established that PPCI, performed expeditiously by experienced operators, is the preferred revascularization strategy in STEMI,¹ but little is known about STEMI due to LMCA occlusion although it has been hypothized that clinical outcome is improved by revascularization¹⁷ with a treatment bias favoring PCI rather than coronary artery bypass graft, mainly due to faster revascularization with the percutaneous approach.^17,18 Based on the fact that avoiding any delay in revascularization is crucial in this setting and that cardiac surgery causes an important increase in ischemic time even if CCH is present on site, PPCI has been proposed as the preferred revascularization strategy in this patient subgroup,¹⁸ but most of the reported data are from hospitals with on-site CCH. Despite revascularization, mortality rates in this very high-risk patient subgroup remain very high and vary from 36%-83%;^14-16,19 previous studies have shown at least comparable results with surgical revascularization.²⁰ Most of the deaths occur during the in-hospital phase, with a very low number of events occurring in survivors during the follow-up period.^4,5,10,14 Notably, ULMCA PCI is technically feasible with a very high percentage of angiographic immediate success when performed by experienced operators.^5,14-16,21

The major finding of this single-center registry is that our data confirm the high clinical risk of the ULMCA-STEMI population (additive EuroSCORE >13 in 81.6%) with a very high percentage of cardiogenic shock (73.7%), cardiac arrest requiring resuscitation (15.8%), and very depressed systolic function (50% with <35% ejection fraction) at presentation; these characteristics could explain the very high percentage of IABP usage (94.7%). Frequently (in 97.4% of cases), this population has no previous history of coronary artery disease; furthermore, despite the high-risk profile related to conventional risk factors, isolated left main disease is detected in 28.9% of patients. There is an involvement of distal bifurcation in the majority of patients (89.5%), but the dramatic clinical presentation requires a procedure as quick (and simple) as possible; this fact could partially explain the very high percentage of single-stent technique used for bifurcation treatment and the relatively low percentage of final kissing balloon. Thrombus-aspirator devices were underused when compared with our general STEMI population (2.6% vs 53.2%) probably to obtain a faster revascularization without any delay in very critical patients.¹² Despite no statistically significant differences (P=.2 for in-hospital death and .52 for death at follow-up), a trend for better outcomes for patients presenting with normal TIMI flow at admission was evident (in-hospital death occurred in 33.3% of patients with TIMI 3 flow and in 50% of the other group). A more numerous population could probably give more precise outcome evidence for these two groups. In this selected population with a very high prevalence of cardiogenic shock, complete revascularization was achieved in a percentage smaller than expected.¹ We re-evaluated all coronary angiographies, and in patients with incomplete revascularization the reason to stop the procedure without treating other diseased vessels was: (1) patient death in 35.7%; and (2) clinical stabilization achieved by ULMCA PCI and IABP usage in 64.3%. The relatively high BMS utilization could be due to economical reasons, perhaps with a reluctance to use more expensive devices when little is known about a patient’s short-term prognosis and long-term dual antiplatelet regimen adherence.

Even in the absence of on-site cardiac surgery, “primary” angioplasty of ULMCA in a STEMI setting performed by experienced operators is technically feasible, associated with a good angiographic success rate (84.2%) and a relatively high clinical success rate, and an acceptable rate of MACEs and death if compared with the natural outcome of non-treated patients.¹⁷ Notably, as reported in other studies,^4,5,10,14 the higher prevalence of mortality is concentrated during acute and in-hospital phases and in patients with cardiogenic shock at presentation, with a low number of events during the follow-up period. In our experience, fourteen of the in-hospital deaths occurred during the index procedure (6 patients) or during the first 48 hours (8 patients) without any significant improvement in clinical status after PCI. Two patients with definite stent thrombosis⁸ were treated with a new PCI during hospitalization at day 3 and day 5 of hospitalization, respectively. Both patients were treated with thrombus aspiration and in-stent dilatation with non-compliant balloon, but died during the procedure; one of the patients was not adequately treated with dual antiplatelet therapy (ie, was not treated with clopidogrel during orotracheal intubation). One patient experienced sudden death at follow-up and was classified as probable stent thrombosis.⁸ It’s important to emphasize that the procedural delay related to the activation of the operator’s staff in off-duty hours doesn’t correlate with a worse prognosis and has a similar short- and long-term mortality and TLF rate. This fact could be partially explained by the fact that most of the patients had TIMI 3 flow at presentation. Another partial explanation could be that the delay needed to activate a cath lab’s staff is partially offset by the transportation delay from the spoke centers to our institution. Of course, a word of caution has to be used due to the small number of patients presented in this very select single-center population; in fact, a small, non-significant trend favoring patients who received PPCI during on-duty hours with faster activation of the cath lab and staff is evident, so larger number are needed to obtain definitive conclusions.

Study limitations. This was a retrospective, non-randomized study, with a very select population and a relatively small sample size. Another limitation was the lack of collegial discussion with the surgical team in urgent cases, which might have forced the selection of PCI treatment. Nevertheless, this registry reflects the current practice in most centers offering 24-hour PCI availability without on-site surgical back-up.

Conclusion

Patients presenting with ULMCA as the culprit lesion in a STEMI setting represent a very select population with high clinical risk. PPCI in this group of patients appears to be technically feasible and a good alternative to surgical revascularization, particularly in a center with a high-volume cath lab and experienced operators with a very large personal caseload per year without in-hospital surgical facilities. Mortality in this group of patients tends to be quite high, but lower than the mortality of untreated patients. In addition, the majority of events is concentrated during the in-hospital phase with a very low number of events in the follow-up period. Procedural delay related to staff activation during off-duty hours doesn’t correlate with a worse prognosis.

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From the ¹Ospedale degli Infermi, ASL TO 3, Cardiology Department, Rivoli (Turin), Italy and ²Policlinico Casilino, Cardiology Department, Rome, Italy.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted April 5, 2012, provisional acceptance given May 2, 2012, final version accepted July 16, 2012.

Address for correspondence: Andrea Gagnor, MD, Ospedale di Rivoli, Strada Rivalta 29 10029 Rivoli (TO). Email: gagnora@gmail.com