Introduction
Chronic total occlusion (CTO), is a common abnormality in patients with known coronary artery disease. Many of these patients have been undertreated because of the poor prognosis associated with other known coronary artery disease; e.g., multivessel CAD (MVCAD).
CTO definition
CTO is defined as an occlusion or very low grade TIMI flow of at least 3 months duration [1]. This suggests that dead muscle may be present. If this is the case, as suggested by the work of Khoeif et al. [1], a simple way to evaluate this question is to obtain some indication of LV dysfunction (regional wall motion, RWM) prior to recanalization of a CTO and perform another LV function test after recanalization for comparison - perhaps an echo or another form of imaging to assess RWM such as a cardiac MRI. Collaterals may be present suggesting viability, and these patients are most likely to improve regional wall motion with CTO recanalization.
Early success of CTO/PCI
Early success of CTO PCI is defined as the recanalization of the occluded artery. This occurs in about 80% of the time when done by experienced CTO operators and the success rate increases over time.
Early successful opening of an occluded artery does not correlate with prognosis when the perfused myocardium shows no viability.
Lack of literature on the subject of CTO
I could not find any reports in the English literature in which there was normalization of affected regional LV wall motion (not EF) after successful early recanalization of a typical total occlusion in the absence of viable myocardium. Discussions with interventional cardiologists have failed to reveal whether there are any data on improved regional wall motion after CTO revascularization in non-viable myocardium in the area supplied by the totally occluded epicardial coronary artery.
What must be done
It seems to me that patients who had a successful early opening of a CTO should have an improved prognosis but only if there is viable muscle.
Unfortunately, patients with non-viable myocardium did not show any improvement in regional wall motion after recanalization of CTO. Only if there is viability of the ventricular myocardium supplied by the now opened CTO, can there be a correlation with long term prognosis (see Table 1).
Expected Objective Findings Early and Three Months After the Early Opening of a CTO.
| Viability | TIMI Flow | RWM | Prognosis |
|---|---|---|---|
| Nonviable | No change | No change | No change |
| Viable | Improvement | Improvement | Improvement |
Kawashima et al. [2] used the SYNTAX scoring system to evaluate the efficacy of CTO on RWM and prognosis and found that, expected objective findings early and 3 months after the early opening of the CTO, a SYNTAX score greater than 8 implied a poor prognosis and a score less than 8 implied a better prognosis. At 10 years follow up, revascularization of CTO did not affect mortality unless it was offered to patients with refractory angina in the setting of myocardial viability.
Summary and conclusions
There are no studies in patients with non-viable myocardium subtending a CTO to show improvement of RWM after opening of the CTO.
Patients without symptomatic multivessel CAD or no symptoms of angina have not been evaluated since there was no indication for study in the catheterization laboratory.
CTO of collateral vessels that feed viable myocardium may lead to improvement in regional myocardial wall motion and thus potentially a decrease in mortality.
CTO recanalization in patients with active angina improve symptoms despite limited ability to demonstrate an improvement in wall motion.