Myocardial Viability, Functional Status, and Collaterals of Patients With Chronically Occluded Coronary Arteries

PET evaluation of myocardial perfusion function after percutaneous coronary intervention in patients with chronic total occlusion: a systematic review and meta-analysis

Objective. The benefit of percutaneous coronary intervention (PCI) in chronic complete coronary artery occlusion (CTO) remains controversial. PCI is currently indicated only for symptom and myocardial ischemia abolition, but large chronically occluded vessels with extensive afferent myocardial territories may benefit most from this procedure. The noninvasive evaluation of myocardial perfusion is critical before and after revascularization, and positron emission tomography (PET) can determine absolute myocardial perfusion. Here, we aimed to explore and compare myocardial perfusion in CTO territories and their remote associated areas before and after PCI. Design. We searched for relevant articles published before November 28, 2022, in the Cochrane Library and PubMed. We calculated 95% confidence intervals (CIs) and standardized mean differences (SMDs) for parameters related to myocardial perfusion in CTO territories and remote areas in CTO patients before and after PCI. Results. We included five studies published between 2017 and 2022, with a total of 592 patients. Stress myocardial blood flow (MBF) was increased in CTO territories after PCI when compared to pre-PCI (mean difference [MD]: 1.70, 95% confidence interval [CI] 1.33-2.08, p < 0.001). Coronary flow reserve (CFR) in CTO regions was also higher after PCI (MD 1.37,95% [CI]1.13-1.61, p < 0.001). Stress MBF in remote regions was also increased after PCI (MD 0.27,95% [CI]0.99 ∼ 0.45, p = 0.004), as was CFR in remote regions (MD 0.32,95% [CI] 0.14-0.5, p = 0.001). Conclusions. According to our pooled analysis of current literature, there was an increase in stress MBF and CFR in both CTOs and remote regions after PCI, suggesting that patients with CTO have widespread recovery of blood perfusion after the procedure. These results provide evidence that patients with CTO arteries and high ischemic burdens would indeed benefit from CTO-PCI. Future research on the correlation of ischemia burden reduction with hard clinical endpoints would contribute to a clearer demarcation of the role of CTO PCI with prognostic potential.

Clinical impact of multimodality assessment of myocardial viability

Coronary artery disease (CAD) is a prevalent cause of left ventricular dysfunction. Nevertheless, effective elective revascularization, particularly surgical revascularization, can enhance long-term outcomes and, in selected cases, global left ventricular contractility. The assessment of myocardial viability and scars is still relevant in guiding treatment decisions and selecting patients who are likely to benefit most from blood flow restoration. Although the most recent randomized studies challenge the notion of "hibernating myocardium" and the clinical usefulness of assessing myocardial viability, the advancement of imaging techniques still renders this assessment valuable in specific situations. According to the guidelines of the European Society of Cardiology, non-invasive stress imaging may be employed to define myocardial ischemia and viability in patients with CAD and heart failure before revascularization. Currently, several non-invasive imaging techniques are available to evaluate the presence and extent of viable myocardium. The selection of the most suitable technique should be based on the patient, clinical context, and resource availability. This narrative review evaluates the characteristics of available imaging modalities for assessing myocardial viability to determine the most appropriate therapeutic strategy.

Collateral presence and extent do not predict myocardial viability and ischemia in chronic total occlusions: A stress-CMR study

BACKGROUND

Well-developed collaterals are assumed as a marker of viability and ischemia in chronic total occlusions (CTO). We aim to correlate viability and ischemia with collateral presence and extent in CTO patients by cardiac magnetic resonance (CMR).

METHODS

Multicentre study of 150 CTO patients undergoing stress-CMR, including adenosine if normal systolic function, high-dose-dobutamine for patients with akinetic/>2 hypokinetic segments and EF ≥35%, otherwise low-dose-dobutamine (LDD); all patients underwent late gadolinium enhancement (LGE) imaging. Viability was defined as mean LGE transmurality ≤50% for adenosine, as functional improvement for dobutamine-stress-test, ischemia as ≥1.5 segments with perfusion defects outside the scar zone.

RESULTS

Rentrop 3/CC 2 defined well-developed (WD, n = 74) vs poorly-developed collaterals (PD, n = 76). Viability was equally prevalent in WD vs PD: normo-functional myocardium with ≤50% LGE in 52% vs 58% segments, p = 0.76, functional improvement by LDD in 48% vs 52%, p = 0.12. Segments with none, 1-25%,26-50%,51-75% LGE showed viability by LDD in 90%,84%,81%,61% of cases, whilst in 12% if 76-100% LGE (p < 0.01). There was no difference in WD vs PD for ischemia presence (74% vs 75%, p = 0.99) and extent (2.7 vs 2.8 segments, p = 0.77).

CONCLUSIONS

In a large cohort of CTO patients, presence and extent of collaterals did not predict viability and ischemia by stress-CMR. Scar extent up to 75% LGE was still associated with viability, whereas ischemia was undetectable in 25% of patients, suggesting that the assessment of CTO patients with CMR would lead to a more comprehensive evaluation of viability and ischemia to guide revascularization.