Culprit Vessel PCI versus Traditional Cath and PCI for STEMI

Achieving rapid reperfusion in patients with ST-elevation myocardial infarction (STEM) has been established as an effective and life-saving treatment for these patients. The mortality benefit of primary percutaneous coronary intervention (PCI) is critically dependent on the time required to achieve reperfusion.^1–4 This has been conventionally measured as door-to balloon time with a goal of 90 minutes established as the time within which reperfusion should be achieved. Moreover, this measure is being incorporated as a core measure of quality care by a number of regulatory bodies within the United States, and Europe.^5,6 However, when it became apparent that most centers were not achieving this door-toballoon time within 90 minutes, a nationwide initiative to improve door-to-balloon times was launched.^7–10 Subsequent assessments of door-to-balloon times have indicated marked improvement in door-to-balloon times, primarily as result of eliminating delays in the initial diagnosis of the STEMI, and earlier activation of the cardiac catheterization laboratory.^8,11,12 However, there has been little change in the management of patients once in the catheterization laboratory to further reduce door-to-balloon times.^6,13,14
PCI for STEMI is usually achieved by following the traditional method used in elective cases: complete coronary angiography performed first, followed by PCI. This traditional approach not only allows identification of the culprit lesion, but also allows evaluation of the presence of other coronary disease, such as a critical left main disease, which may alter the decision to proceed with PCI. However, disease that could potentially alter the decision to proceed with PCI is infrequently found in STEMI patients.¹⁵ Additionally, mobilization of an operating room for emergency cardiac surgery exceeds a satisfactory time to achieve reperfusion. Thus, delaying culprit vessel PCI by first performing complete coronary angiography potentially may not result in the most beneficial and timely intervention. We hypothesized that we would reduce door-to-balloon time by performing culprit vessel PCI and then completing coronary angiography and left ventriculography after reperfusion had been achieved.

Methods
One hundred thirty-five consecutive patients at our institution undergoing primary PCI for STEMI from July 2005 to June 2007 and who had complete door-to-balloon time information available were included in the study. During the study period, 5 patients who underwent primary PCI for STEMI were excluded because of incomplete door-to-balloon time information. No other patients were excluded from this analysis. Eighty-five STEMI patients who underwent complete coronary artery angiography followed by culprit lesion PCI served as the control group. The study group consisted of 50 STEMI patients who first underwent culprit PCI followed by complete coronary angiography. The choice of strategy for achieving reperfusion was at the discretion of the interventionalist performing the procedure. During the study period, 6 interventionalists performed primary PCI for STEMI. Five of the 6 performed culprit PCI during thestudy. Concern about performing PCI prior to the availability of information from complete coronary angiography, prior coronary artery bypass graft surgery (CABG) and cardiogenic shock were factors in determining the decision to perform culprit versus traditional PCI by some interventionalists. Identification of the culprit lesion and selection of a guiding catheter for PCI were based on evaluation of the electrocardiogram (ECG). The study was approved by the Institutional Review Board of Wake Forest University Baptist Medical Center.
Patients with STEMI presenting to the emergency department (ED) were assessed immediately with an ECG as well as an initial evaluation by the ED attending physician. The ED attending physician was then responsible for activating the cardiac catheterization laboratory after a brief phone consultation with the interventional cardiology attending physician on call. In the ED, anticoagulation was accomplished with unfractionated heparin as a 30 unit/kg bolus. Patients also received glycoprotein IIb/IIIa receptor inhibition according to usual protocol with abciximab.¹⁶ All patients were treated with aspirin (325 mg daily) prior to PCI, and indefinitely thereafter (81–325 mg). Patients also received clopidogrel (300–600 mg as a loading dose, given immediately after the procedure, followed by 75 mg/day). Clopidogrel was administered for a minimum of 1 month in bare-metal stent-treated patients, for a minimum of 3 months for sirolimus-eluting stent-treated patients, and for a minimum of 6 months for paclitaxel-eluting stenttreated patients. Additional clopidogrel use was at the discretion of the physician responsible for the clinical care of the patient.
In the traditional PCI group, vascular access was obtained using the femoral approach, followed by complete coronary angiography and left ventriculography at the discretion of the attending physician performing the procedure. Identification of the culprit lesion was based on composite assessment of the ECG, coronary angiogram and left ventriculogram if available. The choice of equipment for PCI was left to the discretion of the attending physician performing the procedure, including guide catheter shape and size (6 or 7 Fr). In the culprit PCI group, the location of the presumed infarct lesion was based on the init ial ECG obtained in the ED. In these patients, after vascular access was obtained, a guide catheter was advanced and PCI was performed immediately prior to complete coronary angiography or left ventriculography. Following the PCI, coronary angiography was completed, with left ventriculography at the discretion of the attending physician performing the procedure.
Time intervals for each case were prospectively collected as part of a previously implemented hospital program to assess STEMI quality of care. Prior to hospital discharge, patient and procedural data and hospital outcomes were entered into the Wake Forest University Baptist Medical Center Cardiovascular Information Services Database. Collection of data and outcomes measures conformed to the American College of Cardiology National Cardiovascular Database Registry definitions for cardiovascular data.¹⁷ Stent thrombosis was defined following the recommendations of the Academic Research Consortium as presentation with acute coronary syndrome and definite angiographic or pathologic evidence of stent thrombosis, unexplained death within 30 days of stent placement or target vessel infarction in the absence of angiography.¹⁸ Nonfatal MI was defined as ischemic symptoms and an elevation of creatine kinase-MB > 2 times the upper limit of normal, with or without ST-elevation or development of Q-waves.
Statistical methods. Descriptive statistics (means and standard deviation of continuous factors, frequency counts and relative frequencies of categorical factors) were calculated and compared by PCI method using the Wilcoxon rank sum test for continuous factors and chi-square testing or Fisher’s exact testing where appropriate for categorical factors. Door-to-balloon time intervals were calculated as mean ± standard deviation and compared by PCI method using the Wilcoxon rank sum test. SAS, Version 9.1 Statistical Software Package (SAS Institute, Cary, North Carolina) was used for all statistical analyses.

Results

The baseline clinical characteristics of the culprit and traditional groups were similar, although patients were younger in the culprit vessel group (56 ± 10 years versus 60 ± 13 years) in the traditional group, p = 0.029 (Table 1). The target vessel was more often the right coronary artery (70% versus 49%, p = 0.020) in the culprit versus the traditional group. Procedural characteristics were similar, although fewer drug-eluting stents were used in the culprit vessel group (60%) compared to the traditional group (76%, p = 0.043) (Table 2).
Door-to-balloon times were shorter in the culprit vessel group (66 ± 20 minutes) than in the traditional group (79 ± 28 minutes, p = 0.003) (Figure 1). This was achieved primarily because of a shorter vascular access-to-balloon time in the culprit group (11 ± 8 minutes) than in the traditional group (18 ± 8 minutes, p < 0.001). Door-to-vascular access times were similar for the two groups: 55 ± 18 minutes in the culprit group, versus 61 ± 24 minutes in the traditional group; p = 0.10. Ninety- two percent of the culprit group achieved a door-to-balloon time < 90 minutes, compared to 76% of the traditional group; p = 0.023. In 62% of the traditional PCI group, left ventriculography was performed after the PCI. Door-to-balloon times were still significantly lower in the culprit vessel PCI group (17 ± 9 minutes) than in this subgroup of traditional PCI patients (22 ± 7 minutes; p < 0.001).

In the culprit group, PCI was performed with the initial guide catheter chosen in 49 of 50 patients. In the remaining patient, a right coronary guide was chosen, and the infarct vessel was in the distal portion of a dominant left circumflex coronary artery. Left main or severe three-vessel coronary artery disease was found in 2% of the culprit vessel patients, and in 8% of the traditional patients; p = 0.14. Cardiogenic shock on presentation was infrequent and similar in both groups. Thirty day outcomes are shown in Table 3. Planned revascularization procedures after the index PCI were performed in 2 culprit vessel patients, and in 1 traditional patient; p = 0.28. There were no stent thromboses or recurrent nonfatal MIs in either group. One patient in each group died during the initial hospitalization (p = 0.70), and none thereafter.

Comments
In this small pilot study, we found that door-to-balloon times were reduced using a strategy of performing culprit vessel PCI for STEMI prior to complete coronary angiography and left ventriculography, compared to traditional complete coronary angiography followed by PCI. The benefit occurred due to a decrease in the vascular access-to-balloon time of 7 minutes. Importantly, this benefit was achieved when efforts to reduce door-to-balloon times under 90 minutes had already been implemented, with an average doorto- balloon time of 79 minutes in the traditional PCI group. Significant left main or three-vessel coronary artery disease, cardiogenic shock or mechanical complications of MI were infrequently observed and similar in each group. In-hospital and 30-day outcomes were similar in these small groups of patients. Thus, the strategy of performing culprit vessel PCI alone for STEMI shows promise based on the results of this trial and merits further study.
Achieving reperfusion for STEMI in the cardiac catheterization laboratory by PCI has been recognized as a life-saving procedure.^4,7 However, the mortality benefit of PCI is critically dependent on obtaining reperfusion in a timely fashion.^1,19 The data examining the relationship of time-to-primary PCI in the STEMI patient, however, have yielded inconsistent findings. Cannon et al observed a significant relationship between door-to-balloon times for primary PCI and mortality, but not between symptom-onset time to balloon time and mortality.² Additionally, delay in PCI treatment has been shown to adversely affect mortality in some^,4,19 but not all, clinical trials comparing primary PCI to thrombolytic therapy for STEMI treatment.²⁰ Perhaps the clearest example of the time dependency of the mortality benefit of PCI for STEMI treatment was observed in the study of De Luca et al, where each 30 minutes of delay was associated with a 7.5% relative increase in mortality at 1 year.³ Together, these data provide strong evidence that a shorter time-to-reperfusion with PCI is better.
Efforts to reduce door-to-balloon times have focused on reducing the time spent prior to getting the patient in the cardiac catheterization laboratory.^6,9,11,12 However, there have been few efforts aimed at further reducing door-to-balloon times within the cardiac catheterization laboratory itself.^6,13 Traditionally, patients undergoing revascularization initially undergo complete coronary angiography, with or without left ventriculography. This strategy allows identification of left main and severe three-vessel coronary artery disease, as well as important valvular disease, or myocardial processes such as a ventricular septal defect, or pseudoaneurysm. This traditional approach to the patient requiring emergency revascularization, including STEMI patients has continued to be utilized in most cases. However, several factors have evolved in contemporary care of patients with coronary artery disease that are relevant to this approach. First, the actual number of cases undergoing emergency revascularization procedures requiring CABG has dramatically fallen in the past decade.^21,22 Second, mobilization of the operating room, even under the best of circumstances, generally exceeds a satisfactory time to achieve reperfusion in STEMI patients. Finally, there has been a growing acceptance of hybrid revascularization procedures utilizing both PCI and CABG, either at the same time, or as part of a planned revascularization strategy.²³ Thus, the identification of left main or three-vessel coronary disease itself is not a contraindication to performing PCI of a culprit vessel in a STEMI patient with a staged CABG as deemed necessary.
Observational studies such as ours may be subject to selection bias. Randomized clinical trials would provide the fairest evaluation of culprit vessel versus traditional PCI for STEMI. The decision to perform culprit versus traditional may have been influenced by important patient and procedural factors that may have impacted the outcomes of the study, such as age, prior PCI or CABG, and infarct location. While we cannot exclude this possibility, our culprit and traditional patients had similar baseline clinical and lesion characteristics. Moreover, among the interventionalists performing culprit primary PCI for STEMI, no patient or procedural factors influenced the decision to perform culprit PCI. While we were concerned that discovery of important clinical information after first performing culprit PCI would surface, this was infrequently observed. These concerns need to be evaluated in larger groups of patients before accepting this strategy as standard clinical practice. Also, the study groups were small and studies in larger groups of patients will need to be performed to determine if the strategy evaluated in this study is both feasible and beneficial in broader clinical practice. Our study did not examine outcomes beyond 30 days. Hopefully, longer-term follow up of cohorts such as this will provide valuable information concerning the relative benefit of culprit vessel versus traditional PCI for STEMI.

Clinical Implications
Achieving reperfusion for STEMI in the cardiac catheterization laboratory by PCI has been recognized as a life-saving procedure. However, the mortality benefit of PCI is critically dependent on obtaining reperfusion in a timely fashion. In this study, we found that door-to-balloon time was reduced further using a strategy of performing culprit vessel PCI for STEMI prior to complete coronary angiography and left ventriculography compared to traditional complete coronary angiography followed by PCI. Significant left main or three-vessel coronary artery disease, or mechanical complications of MI, were infrequently observed and similar in each group. Thus, a strategy of tailoring the catheterization sequence for STEMI patients may allow shorter door-to-balloon times without compromising subsequent cardiac care independent of other preprocedural strategies to reduce door-to-balloon times. Larger studies will need to be performed to determine if the shorter door-to-balloon time with culprit vessel PCI as observed in this study translates into superior patient outcomes.
Acknowledgement. We gratefully acknowledge Tammy Davis for manuscript preparation, and Angelina Pack, Aruna Hulme, Sabrina Smith and Robin Taylor for data collection and database entry.

References

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