Author + information
- Loes P. Hoebers, MD, PhD,
- Jose P.S. Henriques, MD, PhD∗ (, )
- EXPLORE Investigators
- ↵∗Department of Cardiology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands
As Drs. Parodi and Di Mario point out in their letter, in 2006 we published our observation that ST-segment elevation myocardial infarction (STEMI) patients with a concurrent chronic total occlusion (CTO) have an increased mortality risk after primary angioplasty (1). This raised the question of whether a routine approach of CTO–percutaneous coronary intervention (PCI) would improve left ventricular function (LVF) and clinical outcome over time instead of the current practice of evaluation of symptoms, ischemia, and viability during follow up. In addition to reducing ischemia in viable myocardium, we hypothesized that early restoration of flow in the CTO territory would beneficially affect infarct healing in addition to restore normal contractility of hibernating myocardium. The EXPLORE (Evaluating Xience and Left Ventricular Function in Percutaneous Coronary Intervention on Occlusions After ST Elevation Myocardial Infarction) protocol did not mandate viability and ischemia testing before inclusion because it is known that more than 90% of all CTOs have inducible ischemia and in the EXPLORE trial all patients had a transmural extension of infarction <75%, and thus a viable myocardium. The majority of patients experienced symptoms in many other registries, whereas in the EXPLORE trial this was rarely the case. As such, the EXPLORE trial was a strategy-based study such as PRAMI and PRIMULTI (PRImary PCI in MULTIvessel Disease).
EXPLORE showed no benefit of routine CTO-PCI on LVF or left ventricular diameters after a follow-up period of 4 months. However, certain sub-groups with a large area of ischemia and infarct size may still benefit such as left anterior descending (LAD) CTOs as suggested in our sub-analysis. Nevertheless, during Transcatheter Cardiovascular Therapeutics (TCT) 2016 we showed that in patients with baseline and 4-month magnetic resonance image no effect was found on LVF including no effect of CTO-PCI in patients with an LAD CTO. We did however find a significant regional improvement in segmental wall thickening in patients randomized to CTO-PCI compared with those treated conservatively. Clinical follow-up data as well as 1-year magnetic resonance images are awaited as remodeling is a complex process which may take more than 4 months to develop (2). In response to Dr. Iannaccone et al., we would like to refer to the supplementary files stating all inclusions over time. All participating centers were high-volume STEMI and CTO centers. We indeed however did not keep a log of patients not included in the trial. Also, many papers describe an improvement over time as the paper referred to by Dr. Iannoccone and also in EXPLORE there was an improvement of LVF but similar in both groups. No study has ever included a control group with a conservative approach; it is very likely that these patients will also show an improvement over time just on medical therapy only including alleviation of stunning. Regarding the success rate, in current literature no uniform definition of successful CTO-PCI exists. Commonly, successful PCI for a non-CTO lesion is defined by a residual stenosis of <30% and post-procedural thrombolysis in myocardial infarction flow ≥2. Because of the complexity of CTO-PCI with sometimes a successful lesion crossing but no effective antegrade perfusion of the myocardium, the EXPLORE core lab mandated that for successful CTO-PCI antegrade perfusion should be achieved to at least 50% of the myocardium supplied by the CTO. Furthermore, currently (almost) none of the published registries underwent core lab adjudication.
Please note: Dr. Henriques has reported that he has received grants from Abbott Vascular during the conduct of the study; and has received grants from BBraun, Abiomed, and Biotronik outside the submitted. Dr. Hoebers has reported that he has no relationships relevant to the contents of this paper to disclose. William Lombardi, MD, served as Guest Editor for this paper.
- 2017 American College of Cardiology Foundation