Arguments for Recanalization of Chronic Total Occlusions*
Patrick W.J.C. Serruys, MD, PhD, FESC, FACC*,
Robert-Jan van Geuns, MD, PhD
Thoraxcenter, Erasmus Medical Center, Rotterdam, the Netherlands.
Chronic total coronary occlusions (CTOs) are a significant clinical problem and are observed in up to 30% to 35% of patients with suspected or known coronary artery disease who undergo diagnostic coronary artery catheterization (1). Because the success rate of percutaneous coronary intervention (PCI) is lower than for nonocclusive stenosis, the majority of these patients are frequently sent for surgery. In the multivessel PCI versus coronary artery bypass graft surgery (CABG) SYNTAX (SYNergy Between PCI with TAXUS and Cardiac Surgery) study, the prevalence of CTO in the randomized arm was only 10%, but in the CABG registry arm it was 40%. In case of single-vessel disease, CTO patients may not be revascularized at all and continued on medical treatment. Although percutaneous treatment of CTOs is a challenging task with a serious risk of vessel perforation, the conservative management of a CTO may not be the best option. Several observational studies have shown a survival benefit if a CTO is successfully treated versus the vessel not being opened (2–4). This may be because during successive years, patients are partially protected against subsequent events in the remaining open vessels. Also, improvement in regional and global left ventricular function provided by treatment has been shown with a decrease in end-systolic volume and an increase in ejection fraction (5,6), which are, in general, related to positive long-term survival. On the other hand, the recently published randomized TOSCA-2 (Total Occlusion Study of Canada) study showed no improvement in left ventricular ejection fraction and remodeling in patients who underwent PCI of the total occluded infarct-related vessel shortly after acute myocardial infarction (MI) compared with optimal medical therapy (7).
The big difference between the TOSCA-2 trial and the nonrandomized trials is the method of patient selection. In the TOSCA-2 trial, patients were included shortly after an acute MI for which no primary PCI was performed. In addition, thrombolytic agents were only administrated in 30% of patients. Therefore, the study included relatively large infarctions with probably a small amount of viable tissue. In contrast, the nonrandomized trials frequently included patients with anginal complaints who usually had a positive ischemia stress test indicating a significant amount of viable tissue. As was shown in 2006, the amount of viable tissue in the CTO region (as detected by delayed contrast-enhanced magnetic resonance imaging [MRI]) is related to reversed left ventricular remodeling during follow-up (8). Hence, pre-procedural viability testing seems to be eminently important in making the decision for or against invasive treatment.
In this issue of JACC: Cardiovascular Interventions, Cheng et al. (9) confirmed the 2006 findings regarding viability testing and also studied the recovery of regional function in greater detail. In addition to regional wall thickening and viability, they investigated myocardial blood flow (MBF) using a quantitative first-pass MRI perfusion technique. In this technique, quantitative MBF is derived from a first pass of an intravenous injection of an MRI contrast agent through the myocardium using a deconvolution method on the successive image intensities. The investigators have a long experience with this technique, which they have validated extensively in animal and human studies. In the hands of these experts, it is as reliable as positron emission tomography imaging, with the advantage of a higher spatial resolution. They clearly showed that, before treatment, hyperemic myocardial blood flow both in the CTO area and in the area from nonoccluded lesions is reduced and becomes normalized within 24 h after the procedure. In this small number of patients, the data give the impression that improvement of wall thickening takes a longer time, although this is statically inconclusive. More remarkable is the increase in resting wall thickening without improvement in resting MBF. The question is whether these areas at baseline represent more chronic stunning instead of hibernation. This also raises the question of whether there was a relationship between improvement in MBF and regional wall thickening. The results of this study should be considered in the perspective of the low sample size and baseline differences between the groups (especially the larger amount of scar tissue in the medically treated CTO group). It is unclear whether this could also explain the low baseline MBF in the stenotic but not occluded areas.
What are the consequences of this study? Pre-procedural evaluation with delayed contrast-enhanced MRI may help in determining which patients may benefit from PCI of a CTO. Perfusion imaging was not evaluated as a diagnostic tool in this study and will probably not be routinely performed because of the cumbersome acquisition and analysis, but it can give us insight into the recovery process of the myocardium after recanalization.
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Footnotes
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* Editorials published in the JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology. 
* Reprint requests and correspondence: Dr. Patrick W. J. C. Serruys, Thoraxcenter, Erasmus Medical Center, Department of Interventional Cardiology, Dr. Molewaterplein 40, Ba-583, Rotterdam, Zuid Holland 3015 GD, the Netherlands. (Email: p.w.j.c.serruys{at}erasmusmc.nl).
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REFERENCES
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- Baks T, van Geuns RJ, Duncker DJ, et al. Prediction of left ventricular function after drug-eluting stent implantation for chronic total coronary occlusions J Am Coll Cardiol 2006;47:721-725.[Abstract/Free Full Text]
- Cheng ASH, Selvanayagam JB, Jerosch-Herold M, et al. Percutaneous treatment of chronic total coronary occlusions improves regional hyperemic myocardial blood flow and contractility: insights from quantitative cardiovascular magnetic resonance imaging J Am Coll Cardiol Intv 2008;1:44-53.[Abstract/Free Full Text]
Related articles in JACC Interventions:
- Percutaneous Treatment of Chronic Total Coronary Occlusions Improves Regional Hyperemic Myocardial Blood Flow and Contractility: Insights From Quantitative Cardiovascular Magnetic Resonance Imaging
- Adrian S.H. Cheng, Joseph B. Selvanayagam, Michael Jerosch-Herold, William J. van Gaal, Theodoros D. Karamitsos, Stefan Neubauer, and Adrian P. Banning
JACC Interventions 2008 1: 44-53.
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