Microvascular dysfunction in the immediate aftermath of chronic total coronary occlusion recanalization

Predictors of long-term adverse outcomes after successful chronic total occlusion intervention: physiology or morphology?

BACKGROUND

Quantitative flow ratio (QFR) and target-vessel SYNTAX score (tvSS) are novel indices used to assess lesion physiology and morphology in percutaneous coronary intervention (PCI). Their prognostic implication after successful recanalization of coronary chronic total occlusion (CTO) is unknown.

OBJECTIVES

To investigate the prognostic value of QFR measured immediately after successful CTO-recanalization in predicting vessel-oriented adverse events, and to compare it with the pre-procedural morphological tvSS.

METHODS

QFR was measured offline after successful CTO-PCIs in a single center. We grouped the patients according to a cut-off value of post-PCI QFR (0.91). The primary outcome was target-vessel failure (TVF) at 2 years.

RESULTS

Among 470 CTO lesions performed during the study period, 324 were eligible for QFR analysis (258 with QFR ≥ 0.91 and 66 with QFR < 0.91). The mean age of the study population was 68.3 ± 10.7 years. The low QFR group had a lower left ventricular ejection fraction (45.8 ± 13.9% vs. 49.8 ± 12.4%, p = 0.025) and a higher rate of atrial fibrillation (19.7% vs. 11.2%, p = 0.020). The mean tvSS was 12.8 ± 4.8, and it showed no significant difference in both groups (13.6 ± 5.1 vs. 12.6 ± 4.6, p = 0.122). Patients with low post-CTO QFR had a trend to develop more TVF at 2 years (21.2% vs. 12.4%, HR 1.74; 95% CI 0.93-3.25, p = 0.086). Low post-CTO QFR failed to predict 2-year TVF (aHR 1.67; 95% CI 0.85-3.29, p = 0.136), while pre-procedural tvSS was an independent predictor for 2-year TVF (aHR 1.06; 95% CI 1.01-1.13, p = 0.030).

CONCLUSION

We found a limited prognostic value of immediate physiological assessment using QFR after successful CTO intervention. Pre-procedure morphological characteristics of CTO lesions using tvSS can play a role in predicting long-term adverse events.

Evaluation of right atrial function by two-dimensional echocardiography and strain imaging in patients with RCA CTO recanalization

OBJECTIVES

The right heart is mainly supplied with blood by the right coronary artery (RCA). The impact of RCA chronic total occlusion (CTO) on the function of the right heart [right atrium (RA) and ventricle (RV)] and whether successful recanalization of a RCA CTO improves the function of the right heart is not clearly understood yet. We aimed to evaluate right atrial function after recanalization of the RCA using transthoracic echocardiography with additional strain imaging.

METHODS AND RESULTS

Fifty-five patients undergoing RCA CTO recanalization at the University Medical Center of Mainz were included in the study. Right atrial strain was assessed before and 6 months after successful CTO revascularization. The median age of the total collective was 66 (50-90) years. We did not find difference in our analysis of RA Volume (p 0.086), RA area (p 0.093), RA major dimension (p 0.32) and RA minor dimension (p 0.139) at baseline and follow-up. Mean RA reservoir strain at baseline was 30.9% (21.1-43.0) vs. 33.4% (20.7-47.7) at follow up (p < 0.001). Mean RA conduit strain was - 17.5% (- 10.7-(- 29.7)) at baseline vs. - 18.2% (- 9.6-(- 31.7)) at follow-up (p = 0.346). Mean RA contraction strain was - 12.9% (- 8.0- (- 21.3)) at baseline vs. - 15.5% (- 8.7-(- 26.6)) at follow-up (p < 0.001).

CONCLUSION

Right atrial function was altered in patients with RCA CTO. Successful revascularisation of an RCA CTO improved RA function assessed by strain imaging at follow-up.

Impact of percutaneous coronary intervention of chronic total occlusions on absolute perfusion in remote myocardium

BACKGROUND

Revascularisation of a chronic total coronary occlusion (CTO) impacts the coronary physiology of the remote myocardial territory.

AIMS

This study aimed to evaluate the intrinsic effect of CTO percutaneous coronary intervention (PCI) on changes in absolute perfusion in remote myocardium.

METHODS

A total of 164 patients who underwent serial [¹⁵O]H_²O positron emission tomography (PET) perfusion imaging at baseline and three months after successful single-vessel CTO PCI were included to evaluate changes in hyperaemic myocardial blood flow (hMBF) and coronary flow reserve (CFR) in the remote myocardium supplied by both non-target coronary arteries.

RESULTS

Perfusion indices in CTO and remote myocardium showed a positive correlation before (resting MBF: r=0.84, hMBF: r=0.75, and CFR: r=0.77, p<0.01 for all) and after (resting MBF: r=0.87, hMBF: r=0.87, and CFR: r=0.81, p<0.01 for all) CTO PCI. Absolute increases in hMBF and CFR were observed in remote myocardium following CTO revascularisation (from 2.29±0.67 to 2.48±0.75 mL·min^-1·g^-1 and from 2.48±0.76 to 2.74±0.85, respectively, p<0.01 for both). Improvements in remote myocardial perfusion were largest in patients with a higher increase in hMBF (β 0.58, 95% CI: 0.48-0.67, p<0.01) and CFR (β 0.54, 95% CI: 0.44-0.64, p<0.01) in the CTO territory, independent of clinical, angiographic and procedural characteristics.

CONCLUSIONS

CTO revascularisation resulted in an increase in remote myocardial perfusion. Furthermore, the quantitative improvement in hMBF and CFR in the CTO territory was independently associated with the absolute perfusion increase in remote myocardial regions. As such, CTO PCI may have a favourable physiologic impact beyond the intended treated myocardium.

Prompt and consistent improvement of coronary flow velocity reserve following successful recanalization of the coronary chronic total occlusion in patients with viable myocardium

Background

Coronary chronic total occlusion (CTO) is characterized by the presence of collateral blood vessels which can provide additional blood supply to CTO-artery dependent myocardium. Successful CTO recanalization is followed by significant decrease in collateral donor artery blood flow and collateral derecruitment, but data on coronary hemodynamic changes in relation to myocardial function are limited. We assessed changes in coronary flow velocity reserve (CFVR) by echocardiography in collateral donor and recanalized artery following successful opening of coronary CTO.

Methods

Our study enrolled 31 patients (60 ± 9 years; 22 male) with CTO and viable myocardium by SPECT scheduled for percutaneous coronary intervention (PCI). Non-invasive CFVR was measured in collateral donor artery before PCI, 24 h and 6 months post-PCI, and 24 h and 6 months in recanalized artery following successful PCI of CTO.

Results

Collateral donor artery showed significant increase in CFVR 24 h after CTO recanalization compared to pre-PCI values (2.30 ± 0.49 vs. 2.71 ± 0.45, p = 0.005), which remained unchanged after 6-months (2.68 ± 0.24). Baseline blood flow velocity of the collateral donor artery significantly decreased 24 h post-PCI compared to pre-PCI (0.28 ± 0.06 vs. 0.24 ± 0.04 m/s), and remained similar after 6 months, with no significant difference in maximum hyperemic blood flow velocity pre-PCI, 24 h and 6 months post-PCI. CFVR of the recanalized coronary artery 24 h post-PCI was 2.55 ± 0.35, and remained similar 6 months later (2.62 ± 0.26, p = NS).

Conclusions

In patients with viable myocardium, prompt and significant CFVR increase in both recanalized and collateral donor artery, was observed within 24 h after successful recanalization of CTO artery, which maintained constant during the 6 months.

Trial registration

ClinicalTrials.gov (Number NCT04060615).

iFR uncovers profound but mostly reversible ischemia in CTOs and helps to optimize PCI results

OBJECTIVES

The study aimed to demonstrate through instant wave-free ratio (iFR) measurements that myocardium distal to a chronic total occlusion (CTO) is ischemic, that ischemia is reversible by PCI, and that iFR assessment after PCI can be used to optimize PCI results.

BACKGROUND

The greatest benefit of revascularization is found in patients with low fractional flow reserve. In patients with CTOs, iFR measurement may be more appropriate to evaluate ischemia as it does not require maximal microvascular vasodilation, which may be hampered by microvascular dysfunction.

METHODS

The iFR was measured in 81 CTO patients, both pre- and post-PCI in 63 patients, and only post-PCI in the following 18 patients. A pressure wire pullback was performed post-PCI if iFR ≤0.89.

RESULTS

The first 63 patients all had significant ischemia distal to the CTO with a median iFR of 0.33 [0.22; 0.44], improving significantly post-PCI to a median iFR of 0.93 [0.89;0.96] (p < .001). In the complete cohort, the median iFR post-PCI was 0.93 [0.86;0.96] but still ≤0.89 in 23 patients (30%). 12 of these patients had further PCI optimization because of a residual focal pressure gradient on pullback, after which only two had a final iFR ≤0.89.

CONCLUSIONS

In CTO patients with an indication for PCI, iFR consistently demonstrated profound myocardial ischemia. Successful PCI immediately relieved ischemia in 70% of patients. In the remaining 30% of cases, a manual iFR pullback proved helpful in guiding further optimization of the PCI result.

Applicability and Interpretation of Coronary Physiology in the Setting of a Chronic Total Occlusion

Concurrent coronary artery disease in a vessel remote from a chronic total occlusion (CTO) is common and presents a management dilemma. While the use of adjunctive coronary physiology to guide revascularization is now commonplace in the catheterization laboratory, the presence of a CTO provides a unique and specific situation whereby the physiological assessment is more complex and relies on theoretical assumptions. Broadly, the physiological assessment of a CTO relies on assessing the function and regression of collaterals, the assessment of the microcirculation, the impact of collateral steal as well as assessing the severity of a lesion in the donor vessel (the vessel supplying the majority of collaterals to the CTO). Recent studies have shown that physiological assessment of the donor vessel in the setting of a CTO may overestimate the severity of stenosis, and that after revascularization of a CTO, the index of ischemia may increase, potentially altering the need for revascularization. In this review article, we present the current literature on physiological assessment of patients with a CTO, management recommendations and identify areas for ongoing research.