Relationship between quality of coronary collateral and myocardial viability in chronic total occlusion: a magnetic resonance study

Assessment of Myocardial Viability and Risk Stratification in Coronary Chronic Total Occlusion: A Qualitative and Quantitative Stress Cardiac MRI Study

BACKGROUND

Indicators for assessing myocardial viability and risk stratification in patients with coronary chronic total occlusion (CTO) are still in the research stage.

PURPOSE

To use stress-MRI to assess myocardial function, blood perfusion, and viability and to explore their relationship with collateral circulation.

STUDY TYPE

Prospective.

SUBJECTS

Fifty-one patients with CTO in at least one major artery confirmed by X-ray coronary angiography (male: 46; age 55.2 ± 10.8 years).

FIELD STRENGTH/SEQUENCE

3.0T; TurboFlash, balanced steady-state free precession cine, and phase-sensitive inversion recovery sequences.

ASSESSMENT

Stress-MRI was used to obtain qualitative and quantitative parameters of segmental myocardium. Myocardial segments supplied by CTO target vessels were grouped according to the degree of collateral circulation assessed by radiographic coronary angiography (no/mild, moderate, or good). Depending on qualitative stress perfusion assessment and late gadolinium enhancement (LGE) extent, segments were also categorized as negative, viable, or trans-infarcted.

STATISTICAL TESTS

Independent sample Student's t-test, one-way analysis of variance (ANOVA) test, Mann-Whitney U test, Kruskal-Wallis test, Spearman correlation coefficient (r). P < 0.05 was considered statistically significant.

RESULTS

A total of 334 segments were supplied by CTO target vessels. The radial strain (RS), circumferential strain (CS), longitudinal strain (LS) of the negative, viable, and trans-infarcted regions showed a significant and stepwise impairment. Myocardial blood flow at rest was positively correlated with RS, CS, and LS (r = 0.42, 0.43, 0.38, respectively). Among the different collateral circulation, there were no significant differences in RS, CS, LS, and LGE volume (P = 0.788, 0.562, 0.122, 0.170, respectively), and there were also no statistically significant differences in the proportions of negative, viable, and trans-infarcted regions (P = 0.372).

DATA CONCLUSION

Myocardial perfusion obtained by stress-MRI combined with strain and LGE may comprehensively evaluate myocardial function and viability, and has potential to facilitate risk stratification of CTO.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

Chronic Total Occlusion of the Left Main Coronary Artery With Preserved Left Ventricular Systolic Function Presenting as a Chronic Coronary Syndrome: A Case Report and Brief Review

The incidence of lesions involving the left main coronary artery (LMCA) during coronary angiography is approximately 5% to 8%. It usually presents with acute coronary syndrome and can be fatal. Total occlusion of the LMCA is rare, often accompanied by myocardial infarction and cardiogenic shock. We present an LMCA chronic total occlusion case in a 60-year-old female patient with chronic coronary syndrome. In our case, the LMCA was selectively visualized, and it was found to be occluded. The right coronary artery fed the entire left system through the collateral network. The patient had no risk of coronary artery disease other than hypertension. Successful coronary artery bypass grafting was performed without any complications.

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.

The association of collaterals with myocardial ischemia and viability in chronic total occlusions

Collateral development in chronic total occlusions (CTO) is crucial to perfuse the distal myocardium and its angiographic evaluation is frequently used to assess the need for revascularization. We aimed to analyse the association between the presence of ischemia and hibernating myocardium, evaluated by cardiac [¹³ N]NH3/2-[¹⁸ F]FDG PET-CT, and the angiographic characterization of the collateral circulation. Prospective study including patients with a CTO who underwent a [¹³ N]NH3 and, when deemed necessary, 2-[¹⁸ F]FDG PET-CT. Well developed (WD) collaterals were defined as a concomitant angiographic Rentrop grade 3 and Werner collateral connection score 2 or 3, whereas the remaining as poorly developed (PD). 2% thresholds used to identify prognostic benefit of revascularization were applied: ischemia > 10% and hibernating myocardium > 7%. Fifty-nine patients (age 62.9±9.1 years, 58 male) were recruited, WD collaterals were present in 28 (47.5%). No significant differences were found in ischemia (WD 6.4±4.3 vs. PD 7.0±4.1, p = 0.64) and hibernation (WD 1.8±1.9 vs. PD 3.1±3.3, p = 0.18) scores. Most CTO territories demonstrated ischemia, but only 19 (46.3%) were associated with an area > 10% (WD 47.6% vs. PD 45.0%, p = 0.58). Scared non-viable myocardium was limited to 9 (15.3%) patients and was not associated with PD collaterals. Hibernating myocardium was frequent (54.2%), but just 6 (10.2%) CTO patients had an area of > 7% (WD 3.6% vs. PD 16.1%, p = 0.20). Collateral assessment by angiography has a poor association with the ischemic burden and hibernation state of CTO territories. Myocardial viability was present even in most CTO with angiographic PD collaterals.