LETTER TO THE EDITOR
Revascularizing chronic total occlusions: what about the coronary collaterals and myocardial viability story?
S. K. Chugh, MDa
a Interventional Cardiology, St. Paul’s Hospital, 1081 Burrard Street, Room 5029, Vancouver, BC V62 1Y6 Canada
drskchugh{at}hotmail.com
With reference to the study by Suero et al. (1), I wish to make the following comments:
1. Although there was a 10-year survival advantage in patients who had a successful percutaneous coronary intervention (PCI) to a chronic total occlusion (CTO), this study did not look at the relation of such a survival advantage following a successful revascularization to the presence of viability of infarcted myocardium in the 54% with a previous myocardial infarction (MI). This relationship is expected.
2. It may not be correct to state that all CTOs benefit from revascularization. I suspect that the survival advantage in this cohort came mainly from improvement in left ventricular (LV) function following improvement in contractility of viable infarcted myocardial segments (2). In support, there is data from some uncontrolled surgical series to show that improved survival in patients with LV dysfunction correlates with the presence of myocardial viability in several LV segments (3).
This will be the subject of evaluation in the Total Occlusion Study of Canada (TOSCA-2) substudy of the ongoing Occluded Artery Trial (OAT), which follows the previously published TOSCA study (4). Interestingly, this survival advantage occurred although only 10% of patients received a stent. A significant reduction in restenosis following stenting compared with balloon angioplasty of a CTO was reported in the TOSCA study.
3. The role of collaterals in this situation has always been an area both of controversy and interest. This would perhaps be a good opportunity to review the data to see whether the survival advantage reported in this study correlates with the presence of angiographic collaterals, especially as there is now data to show that collateral flow assessed invasively (5) does correlate with viability of infarcted myocardium, as was first proposed in Chugh’s hypothesis (6).
An important relevant observation is that the study population had a mean duration of occlusion of the CTO vessel of 12 ± 20 months. This study is therefore more likely to be able to answer the often asked question about the role of angiographic collaterals in predicting myocardial viability. This is because it is believed that CTOs such as these give adequate time for collateral development, unlike the recent occlusions studied using contrast echocardiography soon after acute MI (7).
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1. Suero JA, Marso SP, Jones PG, et al. Procedural outcomes and long-term survival among patients undergoing percutaneous coronary intervention of a chronic total occlusion in native coronary arteries: a 20-year experience. J Am Coll Cardiol. 2001;38:409–414[Abstract/Free Full Text]
2. Bolognese L, Cerisano CP, Bnonamici PV, et al. Influence of infarct zone viability on left ventricular remodelling after acute myocardial infarction. Circulation. 1997;96:3353–3359[Abstract/Free Full Text]
3. Senior R, Kaul S, Lahiri A. Myocardial viability on echocardiography predicts long-term survival after revascularization in patients with ischemic congestive heart failure. J Am Coll Cardiol. 1999;33:1848–1854[Abstract/Free Full Text]
4. Buller CE, Dzavik V, Carere RG, et al. Primary stenting versus balloon angioplasty in occluded coronary arteries: The Total Occlusion Study of Canada (TOSCA). Circulation. 1999;100:236–242[Abstract/Free Full Text]
5. Lee CW, Park SW, Cho GY, et al. Pressure-derived fractional collateral blood flow: a primary determinant of left ventricular recovery after reperfused myocardial infarction. J Am Coll Cardiol. 2000;35:949–955[Abstract/Free Full Text]
6. Chugh SK, Werner GS, Richartz BM, et al. Collateral flow index: to assess myocardial viability—Chugh’s hypothesis revisited. Circulation. 2001;104:13
7. Karila-Cohen D, Czitrom D, Brochet E, et al. Decreased no-reflow in patients with anterior myocardial infarction and pre-infarction angina. Eur Heart J. 1999;20:1724–1730[Abstract/Free Full Text]
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