When to Perform Chronic Total Occlusion Interventions

1.1 Chronic Total Occlusion Definition

A coronary chronic total occlusion (CTO) is defined as 100% occlusion in a coronary artery with noncollateral thrombolysis in myocardial infarction (TIMI) 0 flow of at least 3 month duration. The duration of occlusion may be difficult to determine if there has been no prior angiogram demonstrating presence of the CTO. In such cases estimation of the occlusion duration is based upon first onset of symptoms and/or prior history of myocardial infarction in the target vessel territory.

Occluded arteries discovered within 30 days of a myocardial infarction, such as those included in the Open Artery Trial, are not considered to be CTOs. Hence, the lack of benefit observed with percutaneous coronary intervention (PCI) in these subacute lesions should not be extrapolated to CTO PCI.

1.2 Prevalence of Chronic Total Occlusions

Coronary CTOs are common, found in approximately one in three patients undergoing diagnostic coronary angiography ( Table 1.1 ).

Table 1.1

Prevalence of Coronary Chronic Total Occlusions

First Author	Country	Year	Number of Sites	n	CTO Prevalence (%)	CTO Prevalence Among Prior CABG Patients (%)
Kahn	United States	1993	1	287	35	–
Christofferson	United States	2005	1	8,004	52	–
Werner	Germany	2009	64	2,002	35	–
Fefer	Canada	2012	3	14,439	18	54
Jeroudi	United States	2013	1	1,669	31	89
Azzalini	Canada	2015	1	2,514	20	87
Tomasello	Italy	2015	12	13,423	13	–
Ramunddal	Sweden	2016	30	89,872	16	–

CABG , coronary artery bypass graft surgery; CTO , chronic total occlusion.

Among 14,439 patients undergoing coronary angiography at three Canadian centers, at least one CTO was present in 18.4% of patients with coronary artery disease (CAD). The CTO prevalence was higher (54%) among patients with prior coronary artery bypass graft surgery (CABG) and lower among patients undergoing primary PCI for acute ST-segment elevation myocardial infarction (10%) ( Fig. 1.1 ). Left ventricular function was normal in >50% of patients with CTO and half of the CTOs were located in the right coronary artery. In a Swedish nationwide study and an Italian multicenter registry the prevalence of CTOs among patients with coronary artery disease was 16% and 13%, respectively.

Figure 1.1, Prevalence of coronary chronic total occlusions (CTO) in a large multicenter Canadian registry.

1.3 Should Chronic Total Occlusion Percutaneous Coronary Intervention Be Performed in This Patient?

CTO PCI is a tool in the armamentarium for the treatment of CAD. As with every patient with CAD, treatment of patients with coronary CTOs should include optimal medical therapy (OMT) (every patient should receive aspirin and a statin unless they have a contraindication) and possibly coronary revascularization, with either PCI or CABG.

Revascularization is indicated in patients with angina or other symptoms due to ischemia, such as dyspnea, and possibly patients with ischemia on noninvasive testing, or left ventricular dysfunction ( Fig. 1.2 ). Percutaneous revascularization is preferred in case of single-vessel disease and in post-CABG patients (especially those with patent left internal mammary artery grafts to the left anterior descending artery) due to the high risk and technical challenges associated with redo CABG. In case of multivessel disease, CABG is generally preferred in patients with complex disease (especially if they are diabetic) whereas PCI is preferred in patients with simpler disease.