MSCT guiding PCI

Mohamad Ashraf Ahmad, MD Lecturer of cardiovascular medicine

Assiut University

Agenda

• Introduction • MSCT in CTO• MSCT in aorto-coronary lesions• MSCT in bifurcation lesions • MSCT in CABG • MSCT in diffuse disease

Introduction

• Selective invasive coronary angiography (ICA) is considered the gold standard for detection of CAD.

• Coronary CT angiography has been increasingly used in the diagnosis of CAD owing to rapid technological developments and improved spatial and temporal resolution.

• In patients with a low– intermediate risk of CAD, 64-detector CT identified significant CAD with a sensitivity of 95–99%, specificity of 64–83% and a negative predictive value of 97–99%.

• As a result of the high sensitivity and negative predictive value, current guidelines recommend the use of cardiac CT to exclude significant CAD in this population.

• MSCT is similar to IVUS in the capability to assess both the lumen and vessel wall.

• Coronary calcium score • Evaluation of each coronary artery using– Axial slices– MPR– cMPR– MIP– Volume rendered images.

Coronary CT guiding PCI in CTO

• Successful recanalization of a CTO is associated with substantial improvement in symptoms, quality of life and survival as well as decrease the need for CABG.

• However, PCI in CTO remains a challenge for interventional cardiologists.

• The procedures are often lengthy and complex, with increased radiation exposure, increased contrast load and a higher risk of complications.

• Success rates in most experienced centers range from 55 to 80%

• Angiographic predictors for CTO failure include: – Length of the lesion. – Course and tortuosity of the occluded segment.– Severity and distribution of calcification within the

occluded segment. – Blunt stump, side branches and bridging

collaterals.

Role of MSCT in CTO recanalization:

• Plaque characterization:– Characterization of plaques into soft, mixed and fibro-

calcific comparable with IVUS.– Detecting, quantifying and localizing calcification within

the plaque.• Exact length of the occluded segment with minimal

foreshortening.• Clear course of the occluded artery without adjacent

vessel overlap.

Role of MSCT in CTO recanalization:

• Determining views that show the entry point of the lesion.

• Can define the best angulation with least foreshortening.

Trials of MSCT guided-CTO recanalization:

• Up till now there is no randomized trial compared MSCT guided-CTO versus conventional PCI of CTO without MSCT assistance.

• It has been found that, CTO length > 15 mm and severe calcification that occupies > 50% of the luminal cross section area, are negative CT predictors for recanalization.

• Ueno et al. 2012 showed that Preoperative MSCT does not affect the prevalence of procedural success, irradiation time and the dose of contrast agents, but may be useful to reduce the prevalence of complications during PCIs of CTOs.

• International Journal of CardiologyVolume 156, Issue 1 , Pages 76-79, 5 April 2012

• In a retrospective analysis demonstrated a significantly higher success rate of CTO recanalization procedures in patients who had pre-procedural MSCT.

CT guiding PCI in Coronary aorto-ostial stenosis

• Aorto-ostial coronary stenosis is obstruction of > 50% in diameter involving the ostium of a coronary artery within 3 mm from the aorta.

• Angiographic analysis of aorto-ostial stenosis is limited, particularly by the catheter position .

• ICA has difficulty in assessment of plaque morphology, principally its location, either coronary, aortic or aorto-ostial.

• MSCT allows better identification of morphology and extension of aorto-ostial plaques and help in ideal stent positioning during PCI.

MSCT guiding PCI for bifurcation lesions

Bifurcation lesions

• Bifurcation is a coronary artery narrowing occurring adjacent to, and/or involving, the origin of a significant side branch.

• PCI for bifurcation lesions represents 15~20% of all PCI procedures in daily practice.

• PCI in bifurcation lesions has a relatively high restenosis rate as well as a high incidence of procedural complications including side branch occlusion and myocardial infarction.

• Evaluation of bifurcation depends on:– Degree of side branch involvement.– Diameter of the side branch.– Distal stenosis. – Angle of bifurcation.

• Understanding the bifurcation will help in deciding the technique of PCI– One stent – Two stents – Provisional stenting

Medina classification

MSCT benefit in PCI for bifurcation lesions

• MSCT allows 3D evaluation of both the lumen and the wall of the vessel; thus, it provides a more comprehensive assessment of the complex geometry of bifurcation lesions.

• Preprocedural coronary MSCT may help identify patients at higher risk for branch vessel compromise who would be more likely to benefit from a planned 2-stent strategy.

Distal left main bifurcation lesion

• MSCT is a valid tool for accurate assessment of angiographically uncertain LMCA stenosis.

• MSCT better identify the exact location, length and composition of disease in the LM.

• It gives Information regarding the plaque extension into the LAD and LCx as well as the bifurcation angle.

The plaque distribution and morphology assessed by MSCT may provide useful information that can predict the potential compromise of the branch vessel during treatment of LM bifurcation lesion.

Role of MSCT after CABG

Role of MSCT after CABG

• ICA remains the standard of reference for detection of native coronary artery and graft lesions after CABG.

• However, sometimes selective cannulation and visualization of venous and arterial grafts are challenging.

• Recently, coronary MSCT has emerged as an appropriate alternative investigation technique to assess graft patency and stenosis in symptomatic patients (ACC appropriateness criteria 2010)

MSCT in diffuse CAD

• The diffuse nature of CAD poses problems in ICA, causing it to underestimate the degree of stenosis when there is no nearby "normal" reference segment.

• Under these conditions, segments with diffuse disease could appear on ICA as a normal artery of a small caliber.

• In contrast, IVUS and MSCT are immune from this problem; they depict the vessel wall as well as the lumen and provide measures of maximum lumen area may be crucial in choosing the ideal strategy and appropriate size of the stents.

Limitations of coronary MSCT

• Heart rate greater than 60 or 70 beats/min• Irregular heart rhythm (AF, frequent

extrasystoles)• Inability to sustain a breath hold for at least 5 to

10 seconds• It remains difficult to differentiate between

calcified subtotal and total occlusions.

• Detection of severe stenosis in the distal runoff arteries beyond the anastomotic site after CABG.

• Is not possible on MSCT to identify bridging collaterals or septal collaterals owing to their intramyocardial location

• Increased radiation and contrast exposure.

Take home message

• Coronary MSCT can effectively guide PCI in many

complex coronary lesions especially in CTO and

bifurcations, however, due to its limitations it should

be restricted to cases that incompletely defined by

ICA.

• Pre-procedural MSCT in CTO should be applied in:– CTO lesions that are difficult to visualize on ICA – Lesions with negative predictors for procedural

success on ICA.– lesions that have had previous failed attempts at

recanalization.

Thank you