Rationale and Indications to CTO Recanalisation
Relief of symptomatic ischaemia and angina and improvement of prognosis are the ultimate goals of CTO revascularisation. Borgia et al. documented that successful CTO PCI is related to improved angina-related quality of life (QoL).24 A number of retrospective reports and prospective registries have demonstrated that successful CTO revascularisation leads to enhanced left ventricular function tests and exercise tolerance, decreased need for CABG and improved survival and decreased cardiac mortality or complications in case of future acute events.4,5,7,19,20,25–28 Multicentre randomised trials, such as the EuroCTO trial, have been launched to further elucidate the prognostic impact of CTO revascularisation.15 In anticipation of the study results, the indications to revascularisation of CTOs should not differ from the indications to revascularisation of subocclusive lesions and can be defined based on a potential improvement of prognosis. The dimension of the occluded artery and the presence of other critically narrowed arteries weigh heavily in the decision to revascularise a CTO. Evidence of ischaemia and viability in the territory supplied by the occluded vessel, accompanied in most cases by anginal symptoms or anginal equivalents, should be confirmed.15
Imaging techniques are most suitable to define viability and ischaemia. Magnetic resonance imaging (MRI) can provide objective evaluation of pharmacologically-induced wall motion changes, precisely assessing myocardial fibrosis, perfusion29 and viability. Subendocardial extent of the late gadolinium enhancement smaller than 50 % of the wall thickness with MRI and reversible perfusion deficit greater than 10 % of the total myocardial mass with myocardial nuclear perfusion are currently used as gold standards for viability and prognostically relevant ischaemia. Patients with poorly controlled anginal symptoms with medical therapy may also have indications to revascularisation.30 A prerequisite to meet this indication is the optimisation of the dose and type of drugs, starting from beta-blockers, and the demonstration of objective evidence of ischaemia. Secondary causes of angina, such as anaemia or hyperthyroidism must be appropriately corrected. In theory, indications to surgery or angioplasty are based on the same criteria and the decision between one or the other is purely technical. Surgical revascularisation may be favoured in the presence of left main coronary artery disease, complex triple vessel disease (especially in patients with insulin-dependent diabetes, severe left ventricular dysfunction or chronic renal insufficiency), occluded proximal left anterior descending artery and multiple CTOs with a relatively low anticipated success rate.31 In practice, surgical indications are rarely given if there is no involvement of the proximal left anterior descending coronary artery. The decisions should be taken in an open discussion among clinicians, interventionalists and cardiac surgeons. Data from large national registries (British Cardiovascular Interventional Society (BCIS), Swedish Coronary Angiography and Angioplasty Registry (SCAAR), American College of Cardiology (ACC) Dynamic registry) suggest underutilisation of PCI for CTO, limited to 5-6 % of all the revascularisation procedures and far below its prevalence.12,32 The preference given to surgery is probably not justified because recent trials show that more than 30 % of occlusions initially scheduled for bypass implantation were not grafted because of poor distal vessel quality and the occlusion rate of vein grafts, the most frequently used conduits for right and left circumflex coronary arteries, remains suboptimal and in some series in excess of 50 %.
Nikolaos Konstantinidis is grateful to the Hellenic Society of Cardiology for the 2013 research grant.