Value of Hybrid Imaging with PET/CT to Guide Percutaneous Revascularization of Chronic Total Coronary Occlusion

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.

The indications and utility of adjunctive imaging modalities for chronic total occlusion (CTO) intervention

Coronary chronic total occlusions (CTO) are common in patients undergoing coronary angiography, yet the optimal management strategy remains uncertain, with conflicting results from randomized trials. Appropriate patient selection and careful periprocedural planning are imperative for successful patient management. We review the role of adjunctive imaging modalities including myocardial perfusion imaging (MPI), cardiac magnetic resonance imaging (CMR), echocardiography and computed tomography coronary angiography (CTCA) in myocardial ischemic quantification, myocardial viability assessment, as well as procedural planning for CTO revascularization. An appreciation of the value, indications and limitations of these modalities prior to planned intervention are essential for optimal management.

Non-invasive Imaging in Patients With Chronic Total Occlusions of the Coronary Arteries-What Does the Interventionalist Need for Success?

Chronic total occlusion (CTO) of coronary arteries is a common finding in patients with known or suspected coronary artery disease (CAD). Although tremendous advances have been made in the interventional treatment of CTOs over the past decade, correct patient selection remains an important parameter for achieving optimal results. Non-invasive imaging can make a valuable contribution. Ischemia and viability, two major factors in this regard, can be displayed using echocardiography, single-photon emission tomography, positron emission tomography, computed tomography, and cardiac magnetic resonance imaging. Each has its own strengths and weaknesses. Although most have been studied in patients with CAD in general, there is an increasing number of studies with positive preselectional factors for patients with CTOs. The aim of this review is to provide a structured overview of the current state of pre-interventional imaging for CTOs.

Hybrid PET/MR imaging for the prediction of left ventricular recovery after percutaneous revascularisation of coronary chronic total occlusions

Purpose

To evaluate myocardial viability assessment with hybrid 2-deoxy-2-[¹⁸F]fluoro-d-glucose positron emission tomography/magnetic resonance imaging ([¹⁸F]FDG-PET/MR) in predicting left ventricular (LV) wall motion recovery after percutaneous revascularisation of coronary chronic total occlusion (CTO).

Methods and results

Forty-nine patients with CTO and corresponding wall motion abnormality (WMA) underwent [¹⁸F]FDG-PET/MR imaging for viability assessment prior to percutaneous revascularisation. After 3–6 months, 23 patients underwent follow-up MR to evaluate wall motion recovery. In total, 124 segments were assigned to the CTO territories, while 80 segments displayed impaired wall motion. Of these, 68% (54) were concordantly viable in PET and MR; conversely, only 2 segments (2%) were assessed non-viable by both modalities. However, 30% showed a discordant viability pattern, either PET non-viable/MR viable (3 segments, 4%) or PET viable/MR non-viable (21 segments, 26%), and the latter revealed a significant wall motion improvement at follow-up (p = 0.033). Combined imaging by [¹⁸F]FDG-PET/MR showed a fair accuracy in predicting myocardial recovery after CTO revascularisation (PET/MR area under ROC curve (AUC) = 0.72, p = 0.002), which was superior to LGE-MR (AUC = 0.66) and [¹⁸F]FDG-PET (AUC = 0.58) alone.

Conclusion

Hybrid PET/MR imaging prior to CTO revascularisation predicts more accurately the recovery of dysfunctional myocardium than PET or MR alone. Its complementary information may identify regions of viable myocardium with increased potential for functional recovery.

Use of Coronary Computed Tomographic Angiography to Facilitate Percutaneous Coronary Intervention of Chronic Total Occlusions

Chronic total coronary occlusions (CTO) are found frequently in coronary artery disease; however, the technical challenge to open the occlusion by percutaneous coronary intervention is considerably higher than for nonocclusive lesions. The angiographic analysis is limited by the inability to visualize the occluded segment and requires a dual injection approach from donor and recipient vessel to assess the CTO. Therefore, imaging of the CTO by computed tomographic angiography can provide additional information on the vessel course within the CTO segment, specifically the degree and extent of calcification, and maybe even be superior to angiography to analyze the proximal cap morphology. This had been integrated in a score to predict the interventional success. This information provides a valuable means to better plan the procedure and the required strategy. In addition, an integration of the computed tomographic angiography is possible by synchronization with the gantry position and movement of the angiography system during percutaneous coronary intervention, illustrating the course of the occluded segment and possible obstacles in the way. It remains to be established which patient will most likely profit from this additional preprocedural examination involving increased radiation and contrast media exposure and institutional expenses.

Relationship of myocardial hibernation, scar, and angiographic collateral flow in ischemic cardiomyopathy with coronary chronic total occlusion

BACKGROUND

The relationship between myocardial viability and angiographic collateral flow is not fully elucidated in ischemic cardiomyopathy (ICM) with coronary artery chronic total occlusion (CTO). We aimed to clarify the relationship between myocardial hibernation, myocardial scar, and angiographic collateral flow in these patients.

METHODS AND RESULTS

Seventy-one consecutive ICM patients with 122 CTOs and 652 dysfunctional segments within CTO territories were retrospectively analyzed. Myocardial hibernation (perfusion-metabolism mismatch) and the extent of 18F-fluorodeoxyglucose (FDG) abnormalities were assessed using 99mTc-sestamibi and 18F-FDG imaging. Myocardial scar was evaluated by late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) imaging. Collateral flow observed on coronary angiography was assessed using Rentrop classification. In these patients, neither the extent nor frequency of myocardial hibernation or scar was related to the status of collateral flow. Moreover, the matching rate in determining myocardial viability was poor between any 2 imaging indices. The extent of 18F-FDG abnormalities was linearly related to the extent of LGE rather than myocardial hibernation. Of note, nearly one-third (30.4%) of segments with transmural scar still had hibernating tissue. Hibernation and non-transmural scar had higher sensitivity (63.0% and 66.7%) than collateral flow (37.0%) in predicting global functional improvement.

CONCLUSIONS

Angiographic collateral cannot accurately predict myocardial viability, and has lower sensitivity in prediction of functional improvement in CTO territories in ICM patients. Hence, assessment of myocardial viability with non-invasive imaging modalities is of importance. Moreover, due to the lack of correlation between myocardial hibernation and scar, these two indices are complementary but not interchangeable.

Hybrid anatomo-functional imaging of coronary artery disease: Beneficial irrespective of its core components

Coronary artery disease (CAD) is the most common and important cause of ischemic heart disease, with major implications on global morbidity and mortality. Non-invasive testing is crucial in the diagnostic and prognostic work-up of patients with or at risk of CAD, and also to guide decision making in terms of pharmacologic and revascularization therapy. The traditional paradigm is to view anatomic (i.e., coronary computed tomography) and functional imaging (e.g., myocardial perfusion scintigraphy) tests as opposing alternatives. Such approach is too reductionist and does not capitalize on the strengths of each type of test while risking to overlook the inherent limitations. The combination of anatomic and functional tests in a logic of hybrid imaging holds the promise of overcoming the limitations inherent to anatomic and functional testing, enabling more accurate diagnosis, prognosis, and guidance for revascularization in patients with CAD.

Prevalence of ischaemia in patients with a chronic total occlusion and preserved left ventricular ejection fraction

Aims

Previous studies on invasive assessment of collateral function in patients with a chronic total occlusion (CTO) have displayed only a limited increase in collateral flow and high occurrence of coronary steal during pharmacological stress. This could question the necessity for ischaemia testing prior to revascularization of CTOs in the presence of myocardial viability. The purpose of the present study was to determine the prevalence of perfusion impairments in patients with a CTO as assessed by [15O]H2O positron emission tomography (PET).

Methods and results

Seventy-six consecutive patients (60 men, 62 ± 10 years) with a documented CTO and preserved left ventricular ejection fraction (LVEF) were included. All patients underwent PET to assess (hyperaemic) myocardial blood flow (MBF) and coronary flow reserve (CFR). Collateral connection score was 0 in 7 (9%), 1 in 13 (17%), and 2 in 56 (74%) of the cases, with predominantly a high Rentrop grade (96% ≥2). MBF of the target area during hyperaemia was significantly lower when compared with the remote area (1.37 ± 0.37 vs. 2.63 ± 0.71 mL min-1 g-1, P < 0.001). Target to remote ratio during hyperaemia was on average 0.54 ± 0.13, and 73 (96%) patients demonstrated a significantly impaired target to remote ratio (≤0.75). Only 7 (9%) patients displayed a preserved CFR of ≥2.50, whereas coronary steal (CFR <1.0) was observed in 10 (13%) patients.

Conclusions

Even in the presence of angiographically well-developed collateral arteries, the vast majority of CTO patients with a preserved LVEF showed significantly impaired perfusion. These results suggest that collateral function during increased blood flow demand in viable myocardium is predominantly insufficient.