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By Jeffrey Zimmet, MD, PhD
Associate Professor of Medicine, University of California, San Francisco, Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center
Dr. Zimmet reports no financial relationships relevant to this field of study.
SOURCE: Valenti R, et al. Impact of chronic total occlusion revascularization in patients with acute myocardial infarction treated by primary percutaneous coronary intervention. Am J Cardiol 2014; Sept 25. doi: 10.1016/j.amjcard.2014.09.016. [Epub ahead of print.]
Patients with ST elevation myocardial infarction have significant cardiac morbidity downstream, even after successful primary percutaneous coronary intervention (PCI). Such patients who have ischemic territory in the non-infarct-related arteries have higher event rates than those who do not. The presence of chronic total occlusions (CTO) in this setting carries a particularly negative prognosis.
Valenti and colleagues examined the Florence CTO-PCI registry to determine the effect of successful downstream CTO angioplasty on survival after primary PCI. Consecutive patients with acute MI were examined for candidacy. During the period from 2003 and 2012, 217 patients who underwent successful primary PCI were found to have a CTO in a non-infarct-related artery. This represented 11% of the total primary PCI group. The authors excluded patients who died during the index hospitalization, or whose CTO involved a side branch vessel. This left 169 patients with a main coronary artery CTO in a non-infarct-related artery. Patients who had suitable coronary anatomy, who had no contraindications to a procedure (such as severe chronic kidney disease), and who agreed to participate were scheduled for staged CTO PCI within 30 days of the primary PCI.
From the 169 patients in the group, 74 (44%) underwent a CTO PCI attempt. Fifty-eight of these attempts resulted in an open artery, for a success rate of 78%. These 58 patients with successful CTO angioplasty were compared with the 111 patients with either failed or non-attempted CTO PCI. Within the study, all patients had scheduled clinical and electrocardiographic examinations at 6 and 12 months, and yearly thereafter. All patients were scheduled for angiographic follow-up at 6-9 months, unless contraindicated by renal insufficiency; the achieved angiographic follow-up rate was 86%.
Patients in the successful CTO PCI group were overall younger (64 ± 10 vs 69 ± 14 years), but also were more likely to have low EF on admission, to have higher rates of LAD involvement, and to be smokers. Median follow-up was 3.9 years. Cardiac mortality at 1 year was higher in patients with failed or non-attempted CTO-PCI as compared to the successful CTO-PCI group (12% vs 1.7%; P = 0.025). Likewise, the 3-year cardiac survival rate was significantly higher in patients who underwent successful CTO-PCI as compared with those with a persistently occluded artery (96% ± 3% vs 85% ± 3%; P = 0.030). Within the latter group, there was no difference in survival between those who underwent a failed PCI attempt and those in whom no attempt was made. Follow-up echocardiographic data were available for 156 of the 169 patients. While EF improved at 6 months in both groups, the increase was higher in the successful CTO PCI group (8 ± 9% vs 5 ± 10%; P = 0.039).
It should come as no surprise that the authors of the study use their findings to buttress the argument for complete revascularization beyond just the infarct-related artery in acute MI patients. They further conclude that successful recanalization of a CTO in such patients improves cardiac survival.
This study touches on two major points of controversy within interventional cardiology today. The first is in regard to treatment of non-infarct-related artery stenosis at the time of, or soon after, primary angioplasty. The traditional wisdom saying that such "preventive" PCI is contraindicated was challenged last year with the publication of the PRAMI trial. In that study, patients in the preventive PCI group had lower rates of downstream cardiac events compared with those who underwent treatment of only the infarct-related artery. Similar results were reported more recently in the smaller CvLPRIT trial.
In PRAMI and CvLPRIT, however, patients with CTO were specifically excluded. This brings us to the second point of contention: indications for, and benefits of, CTO angioplasty. Among patients who are referred for coronary angiography, the incidence of CTO has been reported to be as high as one-third. In the current study, 11% of primary angioplasty patients had a coexisting CTO. Although some retrospective studies have suggested a possible survival advantage from successful CTO PCI, this has not been definitively proven. The current ACC/AHA guidelines give only a class IIa recommendation to CTO PCI with "appropriate clinical indications and suitable anatomy." This is undoubtedly due at least in part to the increased difficulty and reduced success rates in PCI of CTO vs non-CTO vessels. CTO PCI in the absence of symptoms is considered to be class III. One controversial aspect of the current study, then, was that the indication for CTO angioplasty was simply the presence of viable myocardium downstream, as assessed either by echo or by myocardial perfusion imaging.
The study authors posit that successful CTO recanalization could impart a survival advantage through improvement in LV function, or by the prevention or reduction of left ventricular remodeling. Improved survival from subsequent acute coronary events is another plausible explanation. But as the authors note, registry data such as this cannot provide a definitive cause-and-effect result. This study may be as good as it gets; however, the prospects for good randomized data on CTO PCI are relatively bleak, due both to a perceived lack of clinical equipoise about revascularization and to the wide range of operator experience and success rates in this specific subset of coronary lesions.
As of just a few weeks ago, the ACC has withdrawn its previous class III recommendation against revascularization of non-culprit vessels in acute MI. This study provides additional information supporting that action. CTO angioplasty is a specialized area, however, and not every interventionalist has or requires this skill set. Therefore, it is even more difficult to endorse the scheme of the study as a blanket clinical strategy. There are enough data with this and other studies to argue that cardiac centers should encourage and develop CTO expertise so that patients may be evaluated on an individual basis, and those with significant ischemic territories and appropriate anatomy may be offered PCI.