Coronary Artery Imaging Suvipaporn Siripornpitak, MD Inter-hospital Conference : Rajavithi Hospital
Larger array : cover scan area Detector size : spatial resolution Rotation speed : scan time
Retrospective ECG gating Prospective ECG gating (only <65) Mid-late diastole reconstruction (60-80%)
sensitivity specificity PPV NPV 16 slice 77 91 60 96 64 slice 88 96 79 98 Dual source 92 93 75 98 320 slice????
ACC guideline
Low to intermediate probability of hemodynamically stenosis Not recommend for screening in asymptomatic subjects Roberts WT. et al, Heart 2008
Contraindications C/I to contrast and radiation Creatinine clearance < 60 ml/min Excessive artifact Severe irregular heart beat High calcium score High HR with C/I for B-blocker Moloo J et al, Semin Roentg 2008
Patient Preparation Preparation of lower HR prior to scan D/C caffeine -12 hours prior D/C NSAID & metformin (reduce contrast induce nephropathy) C/I for B-blocker and NTG Adequate fluid
Techniques HR < 65 beats/min (ideal 60) B-blocker (propanolol, metropolol 50 mg, ½ tab for 3x ) 1 hour prior scan Sublingual NTG just before scan (elective) Contrast 80-85 ml ( 350 mg/ml), CABG 90-100 cc 5mL/s at least Smart prep (asc ao, HU 170). 120 KV, 400-500 MA, 0.35 rotation scan Total scan time/ BH 5 sec (320 slices), 5-9 sec (64 slices)
Coronary calcium score Agatston score calcification of an area of at least 1mm 2 lower threshold of 130 HU Calcium mass score better than volume score
Absence CAC- highly unlikely in the presence of significant luminal stenosis & future cardiac event unstable plaque Positive CAC- plaque burden but Not specific for obstructive CAD Not correlate with angiographic severity Not a sign of stable or unstable plaque Higher the relative risk of cardiac event
CAC : USE IN Risk stratification in intermediate risk Elderly population multiple risk factor with high calcium score (>75% tile) should be aggressive for lipid lowering therapy CAC : NOT USE IN stand-alone screening test risk factors that predict future cardiac event FU tool for evaluation CAD progression does not determine future cardiac event Asymptomatic with low risk CAD
Vulnerable Plaque Non-calcified (fatty, fibro-fatty and fibrous plaques) Lipid rich plaque = 50-70 HU Non-calcified plaque = 90-116 HU Thin fibrous cap =???
Coronary artery stenosis 1-25 % 26-50% Minimal Mild 51-70 % 71-99 % Moderate Severe Occlusion Sundaram B, et al. AJR 2009
Positive remodeled lesion Sundaram B, et al. AJR 2009
CTA Stenosis Threshold Stenosis 70% coronary angiogram Stenosis 50-69% MPS, stress echo Improve the likelihood of significant disease ICA = 0.1 mm 3, CTA = 0.5 mm 3 (64 slices) Nicol et al, Int J Cardiology 2009
Stable Chest Pain GROUP (471) Calcium score- Significant CAD Negative CS 0.5 % R/O CAD without need for further evaluation Low CS (<10) 8.7 %???? Low-intermediate (10-400) = 42% could undergo CTA Stress test used in high CS and obstructive CAD NOT INCLUDED UNSTABLE SYMTOMS WHO OBSTRUCTIVE CAD WITHOUT CALCIFICATION ARE MORE PREVALENCE Nieman, Am J Cardiol 2009
Poor Image Quality 1. irregular heart rate 2. >90 /min 3. calcification 4 vessel motion 5. small caliber (<1.5mm) False (+) with heavy calcification (18%)
Good agreement for detection coronary a. stenosis Presence of non-eccentric calcified plaque affected both intra and interobserver agreement Nicol ED, JCAT 2009;33: 161-8
Blooming artifact Plain Contrast
Bypass Graft and Stents Stent with 64 slices depends on diameter and strut thickness of the stent Location, diameter, patency In-stent restenosis, thrombosis, side branch In-stent contrast attenuation- higher Moderate sensitivity, high NPV
CABG LIMA or saphenous vein graft Radial artery Arterial has more long term patency Type, origin, course and anastmosis Stenosis, thrombosis, aneurysm, anastomosis stricture, opacification of native coronary artery
CABG
LIMA
What Can CT NOT DO Collateral circulation In-stent restenosis Flow quantification
Conclusion-Radiation 64 slice CTA is highly sensitive to R/o significant CAD, high NPV Effective mean radiation dose (64 slices) 11.0 msv Men 7.5-15.2 (dose modulation 7.5 & 8.6) Women 10.2-21.4 msv (10.2 and 12.2 msv Cancer risk 1/114 (20 yo woman), 1/715 (60 yo woman)
Cost-effectiveness MDCT-CA Main value- R/O significant CAD R/O CAD in low or intermediate pretest likelihood Can not replace CA due to determine distal run-off, distal insertion site for CABG Not recommended for detecting asymptomatic CAD.
LF Function LV function LV volume (25% and 99% of RR interval) LVESV overestimate LVEF, LVSV underestimate Interobserver variability 2-11% (CT) and 2-6 % (MR) The higher slice machine such as dual source CT temporal resolution = 83 ms B-blocker Orakzai, JACT 2006; 30
Anatomical Variation
Anomalous origin LMA from RCA (0.09-0.11) LAD or LCx from right coronary sinus (0.32-0.67)- retroaortic course RCA from left coronary sinus (0.03-0.17) RCA, LMCA and a branch from noncoronary sinus
courses Interarterial course 75% of LMA from right coronary sinus Retroaortic course Pre-pulmonic course Sub-pulmonic course
RCA from LAD
Anomalous coronary artery that has hemodynamic significant Myocardial bridging 0.5-2.5% Rarely produce symptom
Inflammatory Process : Kawasaki Dsc Visualization of coronary artery aneurysm Size, length and location Coronary calcification Presence of thrombus Detection of stenosis-occlusion Sensitivity & specificity : 94% & 97%
Coronary MR angiogram
MR angiography Useful for the screening coronary artery lesion in the case that have C/I for CTA or angiography such as allergy to contrast media No radiation exposure No contrast administration Can be perform with other study such as stress and function MR studies
MR angiography: limitations Demonstrated only proximal lesion of LAD and LCX, entire RCA Lesser accuracy in detection of stenosis lesion comparing with CTA Not widely use, no large clinical data MRA in CABG : few report MRA in stent coronary : can not evaluate
RCA LMA-LAD LCX
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