Atrial septal defect MRI
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [[2]]; Cafer Zorkun, M.D., Ph.D. [3]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [[4]]
Overview
Magneic resonance imaging (MRI) is a noninvasive imaging modality that can be used as a diagnostic tool in identifying an atrial septal defect. MRI aids in direct visualization of the atrial septal defect and pulmonary veins. It can assist in quantifying right ventricular volume and function as well as shunt size. Velocity-encoded, phase difference MRI have been found to assess the magnitude of left-to-right shunting as reliably as is done by cardiac catheterization [1]. Also it has the additional advantage of being a non-invasive tool compared to the invasive cardiac catheterization. In addition to this, Phase-contrast cine MRI has been found to be more reliable than Spin-echo images in determining the size of defect that in turn helps to make a better therapeutics decision i.e. trans-cutaneous or the surgical closure [2].However, its current utility is limited for small defects as echocardiography is cheaper, non-invasive and sensitive in diagnosing atrial septal defect.
Magnest Resonance Imaging (MRI)
- Non-invasive imaging method
- Effective tool for when echocardiographic results are inconclusive.
- Provides better visualization of heart vasculture
Indications
- Effective in measuring:[3]
- Flow measurements from the aorta and main pulmonary vein
- Shunt flow
- Heart volumes
- Blood flows
- Ventricular wall thickness
- Size of the septum defect
- Provides identification of additional associated anomalies
Advantages
- Phase velocity mapping helps in measuring the ratio of pulmonary to systemic blood flow (Qp:Qs).[3]
- Quantifies ventricular volume and function and shunt size
- Provides an assessment of the pressure gradient across the valves and atria
- Can provide morphologic image of the heart in neonates
- Provides multiple images of the heart per cardiac cycle
Disadvantages
- Certain physiologic formations can be misidentified, such as a thin fossa ovalis, and mistaken for an ostium secundum defect.
- Imaging, specifically static images, can provide a skewed perception of the thickness of the septum.
- Lacks large study backing, needs more clinical trial investigation to further evaluate the potential indications and limitations of the technique.[3]
- In pediatrics, it may require general anesthesia. This may be less desirable as echocardiography does not.
ACC / AHA Guidelines - Evaluation of the Unoperated Patient (DO NOT EDIT)[4]
| “ |
Class I1) ASD should be diagnosed by imaging techniques with demonstration of shunting across the defect and evidence of RV volume overload and any associated anomalies. (Level of Evidence: C) |
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Supportive trial data
- In a study done by Hundley et al. velocity-encoded, phase difference MRI have been found to assess the magnitude of left-to-right shunting as reliably as was done by cardiac catheterization. Also, it has the additional advantage of being a non-invasive tool compared to the invasive cardiac catheterization.[1]
- In another study done by Holmvang et al. Phase-contrast cine MRI has been found to be more reliable than Spin-echo images. The phase contrast MRI defines the defect shape by the cross section of the shunt flow. Due to the accurate diagnosis of the defect size it helps in making a decision on the therapeutics aspect of the patient i.e. transcutaneous catheter or surgical closure. On the other hand, spin-echo images, are not very accurate in finding ASD size and septal thinning adjacent to a secundum ASD may be falsely considered a part of the defect [2]
References
- ↑ 1.0 1.1 Hundley WG, Li HF, Lange RA, Pfeifer DP, Meshack BM, Willard JE; et al. (1995). "Assessment of left-to-right intracardiac shunting by velocity-encoded, phase-difference magnetic resonance imaging. A comparison with oximetric and indicator dilution techniques". Circulation. 91 (12): 2955–60. PMID 7796506.
- ↑ 2.0 2.1 Holmvang G, Palacios IF, Vlahakes GJ, Dinsmore RE, Miller SW, Liberthson RR; et al. (1995). "Imaging and sizing of atrial septal defects by magnetic resonance". Circulation. 92 (12): 3473–80. PMID 8521569.
- ↑ 3.0 3.1 3.2 Xiuling, Q.I., Merchant, N., Walker, F., Webb, G., McLaughlin, P., Stainsby, J., Wright, G. "MRI Assessment of Atrial Septal Defects in Adults". Proc Intl. Soc. Mag. Reson. Med. year= 2001. 9: 455.
- ↑ Warnes CA, Williams RG, Bashore TM, Child JS, Connolly HM, Dearani JA; et al. (2008). "ACC/AHA 2008 guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Develop Guidelines on the Management of Adults With Congenital Heart Disease). Developed in Collaboration With the American Society of Echocardiography, Heart Rhythm Society, International Society for Adult Congenital Heart Disease, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons". J Am Coll Cardiol. 52 (23): e1–121. doi:10.1016/j.jacc.2008.10.001. PMID 19038677.