Cardiac MRI in ACHD What We Have Learned to Apply to ACHD Patients Faris Al Mousily, MBChB, FAAC, FACC Consultant, Pediatric Cardiology, KFSH&RC/Jeddah Adjunct Faculty, Division of Pediatric Cardiology and Department of Radiology, University of Florida
Prevalence of ACHD Since the advent of neonatal repair of complex lesions in the 1970s, there has been a significant improvement in survival rate of patients with CHD. An estimated 85% of patients with CHD will survive to adulthood. In the United States, there are approximately 800 000 adults with CHD. Patients with single ventricle, systemic right ventricle or complex intra cardiac baffles are entering adult life and starting their families.
Imaging in CHD X ray 1895 Cardiac Catheterization 1937 Nuclear tracers 1952 Echocardiography 1953 Cardiac CT 1979 Cardiac MRI 1983
Indications for CMR in CHD 1. Initial evaluation and follow up of adult CHD. 2. Assessment of shunt size. 3. Anomalies of the viscero-atrial situs with and without complex CHD. 4. Anomalies of the atria and venous return. 5. Anomalies of the AVV. 6. Anomalies of the ventricles. 7. Anomalies of the semilunar valves. 8. Anomalies of the arteries.
General Recommendation for CMR in ACHD Location of CMR resources Training i in CMR of ACHD Recognition of previously unsuspected CHD in adults Baseline CMR European Heart Journal (2010) 31, 794 805
Indications for CMR Journal of the American College of Cardiology Vol. 52, No. 23, 2008
Indications for CMR Journal of the American College of Cardiology Vol. 48, No. 7, 2006
Indications for CMR European Heart Journal (2010) 31, 794-805
Where does CMR fit It provides an additional noninvasive imaging modality if findings by echocardiography are uncertain. It provides direct visualization of the defect and extra cardiac structures t such as pulmonary veins. It can also measure, with relative accuracy, function, volumes and shunt ratio.
Strengths th of CMR in CHD Unrestricted access to cardiovascular anatomy and function without exposure to ionizing radiation Well suited for repeated, life-long follow-up investigation, if needed. Versatility, including measurements of biventricular size and function regardless of chamber geometry, measurements of flow volumes, characterization of tissues, and assessment of myocardial function, viability, and perfusion, when required. CMR without gadolinium is applicable in women with CHD during pregnancy.
Applications of cardiac MR Morphology Function Flow quantification Perfusion Late enhancement Coronary angiography Tagging
Morphology
Ventricular Function Qualitative Quantitative
Ventricle Evaluation
Short axis stack for Quantitative and Qualitative function
Post processing
Flow Quantification Clinical applications: Cardiac output Valve regurgitation g Qp/Qs Split lung perfusion Diastolic function
Flow Quantification
Post Processing
Tissue Characterization Perfusion and viability Evaluation of cardiac masses Cardiac iron load with T2*
Perfusion
Late Enhancement
Tagging
Coronary imaging
Patients with tetralogy of Fallot should have echocardiographic examinations and/or MRIs performed by staff with expertise in ACHD. Appropriate imaging (2 dimensional echocardiography annually in most cases and/or MRI every 2 to 3 years) should be undertaken by staff trained in imaging of complex congenital heart defects. MRI is now seen as the reference standard for assessment of RV volume and systolic function, assessing the severity of pulmonary regurgitation and in evaluating important associated pathology, especially involving the pulmonary arteries and the ascending aorta. Journal of the American College of Cardiology Vol. 52, No. 23, 2008
Tetralogy of Fallot Journal of Cardiovascular Magnetic Resonance 2011, 13:9
Indications for Pulmonary Valve Replacement: Indications for PVR in patients with repaired TOF or similar physiology with moderate or severe pulmonary regurgitation (regurgitation fraction 25%) I. Asymptomatic patient with two or more of the followingcriteria: a. RV end diastolic volume index >150 ml/m2 or Z score >4. In patients whose body surface area falls outside published normal data: RV/LV end diastolic volume ratio >2 b. RV end systolic volume index >80 ml/m2 c. RV ejection fraction <47% d. LV ejection fraction <55% e. Large RVOT aneurysm f. QRS duration >140 ms g. Sustained tachyarrhythmia related to right heart volume load h. Other hemodynamically significant abnormalities: RVOT obstruction with RV systolic pressure 2/3 systemic Severe branch pulmonary artery stenosis (<30% flow to affected lung) not amenable to transcatheter therapy Moderate tricuspid regurgitation Left to right shunt from residual atrial or ventricular septal defects with pulmonary to systemic flow ratio 1.55 Severe aortic regurgitation Severe aortic dilatation (diameter 5 cm)
Tetralogy of Fallot Myocardial function Ascending aorta dimensions Residual shunts RVOT aneurysm RVOT tethering to the sternum PR,TR and AR MPA morphology Branch PAs Collateral vessels Late enhancement
Tetralogy of Fallot MRA Branch PAs
Coarctation of the Aorta Every patient with coarctation (repaired or not) should have at least 1 cardiovascular MRI or CT scan for complete evaluation of the thoracic aorta and intracranial vessels. MRI or CT angiography with 3 dimensional reconstruction identifies the precise location and anatomy of the coarctation and entire aorta, as well as collateral vessels. Magnetic resonance angiography may also be useful to quantify collateral flow. Evaluation of the coarctation repair site by MRI/CT should be performed at intervals of 5 years or less, depending on the specific anatomic findings before and after repair. Journal of the American College of Cardiology Vol. 52, No. 23, 2008
Coarctation of the Aorta LV mass and function Arch anatomy and branching Severity of coarctation tti or recoarctation tti Collateral vessels Aneurysm formation Aortic valve and ascending aorta
Ascending Aorta
Coarctation Post repair evaluation
Pregnancy!
Limitations of CMR in CHD Thin mobile structures may not be well seen. Experience is needed for appropriate velocity acquisition and Interpretation. Cardiovascular magnetic resonance lacks the portability of echo and is not available during open heart surgery. Implanted pacemakers and defibrillators generally preclude CMR.
MRI Challenges Pacemakers and metals Artifact Nephrogenic systemic fibrosis (NSF) Claustrophobia
Artifact
Nephrogenic systemic fibrosis Caused by Gadolinium in patients with renal impairment. i Tissue fibrosis including skin. Final Diagnosis by skin biopsy.
Conclusion Regional centers caring for ACHD should have CMR capability. Those centers should provide high quality studies with well trained personnel and up to date equipment. Cardiologist should be aware of the indications, i contraindication i as well as the limitations of CMR.