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CT & MRI OF THE CORONARY ARTERIES – TIPS AND TRICKS Dr. Karen Lyons, MB BCh BAO Pediatric Radiologist, Arkansas Children’s Hospital Assistant Professor, University of Arkansas Medical Sciences INTRODUCTION • Why does CT and MR imaging of coronary arteries matter • Reasons to do it in children • Technical pitfalls of each modality • Case examples INDICATIONS FOR CORONARY IMAGING • Coronary vasculitis • Kawasaki disease • Anomalous coronary origins • ALCAPA • AAOCA • Coronary fistula • Pre-operative evaluation in CHD CORONARY CTA VS. MRA MRA • Better temporal resolution • Feasible during free breathing • Non contrast • Allows concomitant evaluation of function, perfusion, viability CTA • Better spatial resolution • Images less degraded by valves, or metallic coils • Inferior temporal resolution • Dependence on slower heart rates CORONARY MRA VS. CTA 4-year-old with common coronary from right cusp, inter-arterial course of left coronary 3D SSFP Navigator 19-day-old with myocardial infarction, single coronary arising from RVOT Volumetric axial, retrospective ECG-gated, ED 11.7 mSv CARDIAC CT… NEED FOR SPEED • Ability to image dependent on HR and CT temporalcoverage • Solutions: faster gantry rotation, dual x-ray tube sources, broader detector array, combining multiple heart beats, and partial scan and undersampled acquisition and reconstruction • Temporal resolution < 80 ms and coverage > 40 cm/s feasible CT ANGIOGRAPHY - MERITS • • • • • Spatial resolution slightly better than MRI. Gold standard for non-invasive coronary imaging 3D–dataset with true isotropic resolution Multi-phasic and functional studies possible Good temporal resolution – about .35-2 seconds per dynamic, but less than MRI • Half scan reconstruction 175 ms • Safe and effective in presence of metallic coils, pacemaker wires, valvular prostheses, aneurysm clips CT ANGIOGRAPHY - PITFALLS • Ionizing radiation • Dependent on fast injection rates to dilate the coronary arteries • Timing is critical • Fast HRs in small children – systole may be the best phase • If HR >65bpm or variable, temporal resolution 175ms not fast enough • Multiple prospectively gated heart beat scans using multisegment reconstruction or multiple heart beat scans using retrospective gating. 7 YEAR OLD BOY WITH CHEST PAIN HR: 90 bpm Pitch 0.293 3mL/sec 70mL total injection HLHS S/P NORWOOD & COILING OF AORTIC OUTFLOW MR CORONARY ANGIOGRAPHY MR CORONARY ANGIOGRAPHYMERITS • No ionizing radiation • Calcification • Non contrast • High temporal resolution MR CORONARY ANGIOGRAPHY PITFALLS • Lower spatial resolution • Longer imaging time • Diaphragmatic drift • PPM/ ICD • Susceptibility artifact MR CORONARY ANGIOGRAPHY – TECHNICAL CONSIDERATIONS • Coil selection (5 vs 32 channel) • Field strength (3T vs 1.5T) • Target volume vs. whole heart technique • Contrast agent Cardiac Localization Right Coronary Artery (RCA) 1 2 3 4 x x x x x x 1. 2. 3. 4. Acquire a stack of 2D axial localizers from a coronal localizer. Use 3-point tool (red x) to create slab orientation along RCA from base to apex. Again Use 3-point tool to fine tune the location of the slab. Resulting images should lay out RCA in-plane. Cardiac Localization Left Anterior Descending Artery (LAD) 1 2 3 4 x x x 1. 2. 3. 4. Acquire a stack of 2D coronal localizers through aortic root. Position axial oblique slab along LAD from its origin toward the apex. Use 3-point tool to identify the origin and distal points along the LAD. Resulting images should lay out LAD in-plane. PERFUSION/ VIABILITY IMAGING • Perfusion imaging: 3T MR provides improved contrast in first-pass myocardial perfusion imaging over a range of gadolinium doses • Viability imaging: Improved real-time cine LGE imaging method at 3T • Specialized techniques: • Stress perfusion MRI imaging • MR evaluation of allograft coronary vasculopathy EXAMPLES CASE 1 • 2 y/o female with unknown heart disease, lost to follow-up • At 8 presented with syncope, echo/angio/ecg showed mitral insufficiency, pulmonary arterial hypertension, A-Fib à mitral annuloplasty performed CASE HISTORY • 2 y/o female with unknown heart disease, lost to follow-up • At 8 presented with syncope, echo/angio/ecg showed mitral insufficiency, pulmonary arterial hypertension, A-Fib à mitral annuloplasty performed • At 10, again had syncope with episodic SOB… had further work-up including cardiac cath and cardiac MRI à showed dilated LA, mitral insufficiency, LVH, restrictive cardiomyopathy, PAH, dysrhythmia… • Eventually came to TCH for Cardiac CTA CARDIAC CTA Texas Children’s Hospital Singleton Department of Pediatric Radiology CARDIAC CTA OUTSIDE CARDIAC MRI ANOMALOUS ORIGIN OF THE LEFT CORONARY ARTERY FROM THE PULMONARY ARTERY (ALPACA) • Bland-White-Garland syndrome • 1 / 300,000 live births • 0.25 – 0.5% of all congenital heart defects ALCAPA • “Coronary steal” phenomenon à left-to-right shunt = abnormal left ventricular perfusion • Myocardial ischemia and infarction ALCAPA • “Coronary steal” phenomenon à left-to-right shunt = abnormal left ventricular perfusion • Myocardial ischemia and infarction • Infant type: 90%, present in first year of life with heart failure (usually within weeks/months of birth), if untreated results in death ALCAPA • “Coronary steal” phenomenon à left-to-right shunt = abnormal left ventricular perfusion • Myocardial ischemia and infarction • Infant type: 90%, present in first year of life with heart failure (usually within weeks/months of birth), if untreated results in death • Adult type: development of significant collateral circulation, but usually not enough à chronic LV subendocardial ischemia, mitral insufficiency, malignant ventricular dysrhythmias à sudden cardiac death in 80-90% (small % asymptomatic) ALCAPA FACTORS ENABLING SURVIVAL BEYOND INFANCY IMAGING FINDINGS • LCA arising from MPA, typically left inferolateral aspect • MR: retrograde flow on SSFP cine images • Secondary findings: • • • • Dilated/tortuous RCA and LCA Dilated intercoronary collaterals (epicardial and interventricular) Left ventricular hypertrophy and dilation from chronic myocardial ischemia Myxomatous degeneration and ischemia of papillary muscles, causing mitral insufficiency/prolapse • Global hypokinesis • Dilated bronchial arteries acting as systemic collaterals • Delayed subendocardial enhancement à predictive of malignant dysrhythmias and indication for repair DILATED CORONARY ARTERIES • Kawasaki disease • Multiple focal coronary artery aneurysms • Young patients following viral illness • Coronary artery-coronary sinus fistula • Only fistulous artery is dilated • Takayasu Arteritis • Coronary artery aneurysms and stenosis • Additional involvement of aorta and great vessels TREATMENT • Infant type: • Coronary button transfer: Direct reimplantation with button of MPA (preferred) • Takeuchi procedure: transpulmonary baffle • Adults: • CABG with ALCAPA ligation • Heart transplantation if severe left ventricular dysfunction CASE 1 • 4 yo female with abnormal EKG CMRI ALCAPA • Anomalous left coronary artery arising from the PA, rare and 90% diagnosed in 1st year of life, Bland-White-Garland syndrome • Problem is coronary steal when pulmonary perfusion pressure falls after first couple of months, risk of myocardial ischemia • Late presentation usually with LV dysfunction, myocardial infarction ALCAPA • Surgical repair: • direct re-implantation (also known as coronary button transfer technique), • Tackeuchi repair (where the pulmonary artery is opened, creating an anterior transverse flap of native pulmonary artery tissue, which creates a baffle to carry the aortic oxygenated blood to the anomalous coronary artery , • left coronary artery ligation • coronary artery bypass grafting (CABG) ALCAPA • Complications; • Narrowing of the anastomoses • Myocardial ischemia CASE 2 • 7 y.o. male with fever, strawberry tongue, mouth hyperemia and conjunctivitis Texas Children’s Hospital Singleton Department of Diagnostic Imaging CHEST CTA Axial CHEST CTA CHEST CTA DIFFERENTIAL DIAGNOSIS • Kawasaki disease • Other vasculitides • Coronary fistulae KAWASAKI DISEASE • Rare, unknown etiology – abnormal response to infection/ toxin suggested • Small to medium vessels • Young children, M>>F, peaks: 6-24 months, after 5 years, most self-limited • Prolonged fever, conjunctivitis, inflamed tongue/oral mucosal membranes, cervical LAD, maculoerythematous rash hands/ feet KAWASAKI DISEASE • Myocarditis (36%), pericarditis (16%) • Fusiform/saccular coronary aneurysms (2nd-3rd wk), occlusion/ stenosis, calcifications • ASA (high dose then low dose), IVIG (acute – may decrease coronary abnormalities), tPA, ocasionally bypass or transplant CASE 3 • 10 year old with abnormal ECHO 10 YEAR OLD WITH ABNORMAL ECHO ANOMALOUS AORTIC ORIGIN OF A CORONARY ARTERY (AAOCA) • • • • 0.6% incidence ARCA 0.1% incidence ALCA 14-17% SCD 10-30 yoa • • • • Mechanism unclear Intra-arterial Intra-mural Ostial stenosis IMAGING OF AAOCA • • • • • CT preferred to MRI Improved spatial resolution and contrast Evaluate ostium and proximal course Retrospective CT gives dynamic information CT • • • • Coronary dimension Pericoronary fat Morphology of ostium Good surgical correlation in 25 pts STANDARDIZED NOMENCLATURE MANAGEMENT REFERENCES • Sakuma H. Coronary CT versus MR angiography: The role of MR angiography. Radiology 2011;258:340-349 • Sena L, Krishnamurthy R, Chung T. Pediatric Cardiac CT. En Lucaya J. Strife J, eds. Pediatric Chest Imaging. Berlin, Heidelberg: Springer-Verlag; 2007:361-395 • Araoz PA et al: 3 Tesla MR Imaging provides improved contrast in first-pass myocardial perfusion imaging over a range of gadolinium doses. J Cardiovasc Magn Reson. 2005;7(3):559-64 • Kadbi Met al: An improved real-time late gadolinium enhancement imaging method at 3T. Conf Proc IEEE Eng Med Biol Soc. 2011;2011:531-4 REFERENCES • Hussain T., Fenton M., Peel S.A., et al; Detection and grading of coronary allograft vasculopathy in children with contrast-enhanced magnetic resonance imaging of the coronary vessel wall. Circ Cardiovasc Imaging. 2013;6:91-98 • Noel C, Molossi S, Krishnamurthy R, Moffett B, Krishnamurthy R. Cardiac MR stress perfusion with regadenoson and dobutamine in children: single center experience in repaired and unrepaired congenital and acquired heart disease. J Am Coll Cardiol. 2016;67(13_S):964. • Dietz SM, Tacke CE, Kuipers IM, et al. Cardiovascular imaging in children and adults following Kawasaki disease. Insights into Imaging. 2015;6(6):697-705. doi:10.1007/s13244-015-0422-0 • Mery C, Lawrence S, Krishnamurthy R, Sexson-Tejtel K, Carberry K, McKenzie D, Fraser C. Anomalous Aortic Origin of a Coronary Artery: Toward a Standardized Approach. Semin Thorac Cardiovasc Surg. 2014;26(2):110-22