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

Abstract

Chronic total coronary occlusions (CTO) are documented in approximately one fifth of diagnostic invasive coronary angiographies (ICA). Percutaneous coronary interventions (PCI) of CTO are challenging and are accompanied by higher complication and lower success rates in comparison with non-CTO PCI. Scrutinous evaluation of ischemia and viability to justify percutaneous revascularization is therefore of importance to select eligible patients for such a procedure. Furthermore, knowledge of the anatomical features of the occlusion may predict the chances of success of PCI CTO and could even guide the procedural strategy to augment the likelihood of recanalization. Positron emission tomography (PET) is unequivocally accepted as the reference standard for ischemia and viability testing, whereas coronary computed tomography angiography (CCTA) currently allows for non-invasive detailed three-dimensional imaging of the coronary anatomy that adds morphological information over two-dimensional ICA. Hybrid PET/CT could therefore be useful for optimal patient selection as well as procedural planning. This review discusses the potential value of PET/CT to guide PCI in CTOs.

Keywords: Chronic total occlusion; Coronary artery disease; Coronary computed tomography angiography; Invasive coronary angiography; Percutaneous coronary intervention; Positron emission tomography.

Figures

Fig. 1

Proposed diagnostic and treatment algorithm in patients with a documented chronic total coronary occlusion (CTO). LV left ventricular, OMT optimal medical therapy

Fig. 2

Extensive myocardial ischemia induced by a CTO LAD. Patient with a known CTO LAD for over 7 years with NYHA class II was analyzed with PET to assess the extent of myocardial ischemia before reconsidering (percutaneous) revascularization. a The proximal total occlusion of the LAD (white arrow). To appreciate collateralization, length, and course (white arrow) of the occlusion, a bilateral injection was performed during a diagnostic invasive coronary angiogram (b). PET perfusion shows the extensive (c and d) perfusion defect in presence of a proximal occlusion of the LAD. CTO chronic total occlusion, LAD left anterior descending artery, NYHA New York Heart Association, PET positron emission tomography

Fig. 3

Representative cases of a false-negative and false-positive SPECT result due to limited tracer extraction or attenuation, respectively. False-negative SPECT result (a) in case of an unmistakable perfusion defect of the inferior wall on PET (b) of a patient with a chronic total occlusion (white arrow) of the RCA on ICA (c). False-positive SPECT result (d) (perfusion defect of the inferior wall) of a patient with normal perfusion on PET (e) and no obstructive coronary artery disease on ICA (f). SPECT single photon emission computed tomography, RCA right coronary artery, ICA invasive coronary angiography; other abbreviations as in Fig. 2

Fig. 4

Balanced ischemia on SPECT. Example of a (nearly) normal SPECT (a) and severely reduced perfusion on positron emission tomography (PET) (b, c) in case of a significant left main stenosis (white arrow) and a chronic total occlusion of the RCA (black arrow) on invasive coronary angiography (d). SPECT is hampered by the relative nature of the images, whereas quantification with PET allows for detection of diffusely balanced ischemia. Abbreviations as in Figs. 2 and 3

Fig. 5

State-of-the-art illustration of fused CCTA and PET of a CTO RCA. Relative and absolute (normal value >2.3 mL min−1 g−1 [58]) perfusion defect on H2 15O PET perfusion (a, b) fused with CCTA (c) shows the perfusion defect of the left ventricle in relation to the occluded segment of the RCA (white arrow). ICA confirmed the precise location of the coronary occlusion (white arrow) with bilateral contrast injection (d). CCTA coronary computed tomography angiography; other abbreviations as in Figs. 2 and 3

Fig. 6

Myocardial viability imaging with PET. Illustration showing a mismatch of resting MBF and glucose metabolism of the inferolateral wall indicating viable myocardium (top). A matched resting perfusion and glucose metabolism defect of the inferior wall, indicating non-viable myocardium is shown in the bottom image. 82Rb82rubidium, 18F-FDG18F-deoxyglucose, SA short axis, HLA horizontal long axis, VLA vertical long axis; reprint with permission [63]

Fig. 7

Viability assessment with combined PET perfusion and metabolism. Illustration of simultaneous mapping of coronary anatomy, myocardial perfusion, and metabolism. Due to fused images, it becomes possible to precisely distinguish ischemic viable form non-viable myocardium. 13NH3 13N-labeled ammonia, HU Hounsfield units; other abbreviations as in Fig. 6; reprint with permission [64]

Fig. 8

Example of precise occlusion length estimation with CCTA. Three-dimensional reconstruction (a), maximum intensity projections (b), center line extraction (c), and multiplanar reconstructions (d) of CCTA accurately assesses coronary course, epicardial collaterals, plaque morphology, and occlusion length in case of a long LAD occlusion (white arrows). The occlusion length (black arrow) was confirmed with bilateral contrast injection during ICA (e). Abbreviations as in Figs. 2, 3, and 5

Fig. 9

CCTA coronary course tracking. ICA of the RCA during bilateral contrast injection (a) and corresponding CCTA coronary course tracking images (b) show that the course of the occluded segment is superiorly illustrated with CCTA in comparison with ICA. Abbreviations as in Figs. 2, 3, and 5

Fig. 10

CTO wire crossing difficulty score appreciated from CCTA and ICA. The top CCTA (a) and ICA (b) images display a short occlusion (<20 mm) (white arrow), tapered proximal stump, no calcification, and no bending of the occluded segment (low CT-RECTOR score). This occlusion should be approached and probably successfully crossed with antegrade wire escalation technique. The bottom CCTA (c) and ICA (d) images clearly demonstrates a long (>20 mm) (white arrow) calcified occlusion (high CT-RECTOR score) suggesting that the operator should be able to use dissection and re-entry techniques before trying to cross this occlusion because anatomy dictates which approach should be used. Abbreviations as in Figs. 2 and 3

Fig. 11

Algorithm for crossing CTOs. Hybrid approach dictated by anatomical features of a chronic total occlusion of a native coronary artery. LaST limited antegrade subintimal tracking; other abbreviations as in Fig. 2; reprint with permission [••]