1 Division of Cardiovascular Medicine, Section of Adult Congenital Heart Disease, Vanderbilt University Medical Center, Nashville, Tennessee
2 Division of Pediatric Cardiology, Monroe Carell Jr. Children’s Hospital, Vanderbilt University Medical Center, Nashville, Tennessee
Clinical History
We report the case of a 32-year-old male with a history of double outlet right ventricle (DORV), anomalous left circumflex artery from right coronary sinus, D-malposed great arteries with subpulmonary ventricular septal defect (VSD), subaortic stenosis, hypoplastic aortic valve, interrupted aortic arch (type A) status post aortic arch reconstruction, pulmonary artery band and atrial septectomy at 2 days of age, followed by Damus-Kaye-Stansell (DKS) with central shunt with 5 mm Gore-Tex graft at 9 months of age. He was ultimately surgically palliated with a fenestrated lateral tunnel Fontan at 23 months of age. The original decision to pursue a single ventricle pathway is unknown. He presented with signs and symptoms of heart failure exacerbation. His transthoracic echocardiogram (TTE) showed normal left ventricular (LV) size with severely reduced systolic function with ejection fraction of 5-10%, at least moderately reduced right ventricular (RV) function with mild dilation, large inlet-to-outlet VSD and possible LV thrombus at the apex after administration of LV cavity enhancing contrast (Figure 1 and Movie 1). He was treated with intravenous diuretics for acute heart failure exacerbation and anticoagulation for stroke prevention. After 2 days of anticoagulation, cardiac magnetic resonance imaging (CMR) with contrast was obtained to evaluate ventricular volumes, function, and myocardial delayed enhancement as well as evaluation of possible LV thrombus. MRA chest was also obtained to assess Fontan pathway and aortic arch patency.
 Figure 1. Apical two-chamber view of the left ventricle on TTE with microbubble echo contrast demonstrating possible apical thrombus (red arrow). |
 Movie 1. Apical two-chamber view of the left ventricle on TTE with microbubble echo contrast demonstrating possible apical thrombus. |
CMR Findings
A CMR was performed on a 1.5T Siemens Avanto Fit scanner adopting a mass protocol. The patient was in sinus rhythm and had adequate breath holds with an average heart rate of 98 beats per minute, blood pressure of 125/80 mmHg and body surface area of 2.5 m2. CMR showed severely reduced LV systolic function (LVEF 12%) with mild LV dilation with indexed end diastolic volume of 102 ml/m2. No LV thrombus was noted on CMR after only 2 days of anticoagulation with a heparin drip. Cine images showed earlier LV systole compared to RV systole with increase of LV size at the end of the RV systole. Right ventricular systolic function was moderately to severely reduced with ejection fraction of 38% with indexed diastolic volume of 108 ml/m2 (Movie 2).
 Movie 2. 4-chamber SSFP cine showing biventricular dysfunction and earlier LV systole compared to RV systole. |
CMR also revealed mild to moderate tricuspid regurgitation (TR) with regurgitant volume of ~15 ml and regurgitant fraction of 14% and mild to moderate combined insufficiency of the native, neo aorta and DKS with regurgitant volume of 8 ml and regurgitant fraction of 20-26%. The calculated stroke volumes of RV and LV were 103 ml and 31 ml, respectively. However, the calculated stroke volume measured in the ascending aorta was only 48 ml, with regurgitant volume of 8 ml. This discrepancy required additional flow calculations to determine where the remaining stroke volume was ejected. We then utilized four-dimensional flow (4DF) visualization to better understand this complex physiology. The 4DF visualization showed LV and RV dyssynchrony in which the right to left shunt through the large outlet VSD occurred during systole and left to right shunt during diastole (Figure 2, Figure 3 and Movie 3).
 Figure 2. Four-dimensional flow CMR imaging demonstrating right to left shunt through large outlet VSD during right ventricular systole with region of interest placed at the VSD (2a), and cross-sectional image demonstrating the anatomy (2b). Ao=aorta; Asc=ascending; VSD=ventricular septal defect; RV= right ventricle; LV=left ventricle; DKS=Damus-Kaye-Stansel. |
 Figure 3. Four-dimensional flow CMR imaging demonstrating left to right shunt through large outlet VSD during right ventricular diastole with region of interest placed at the VSD(3a), and cross-sectional image demonstrating the anatomy (3b). Ao=aorta; Asc=ascending; VSD=ventricular septal defect; RV= right ventricle; LV=left ventricle; DKS=Damus-Kaye-Stansell |
 Movie 3. Four-dimensional flow CMR imaging demonstrating flows across the aorta and VSD during cardiac cycle. |
Figure 4 demonstrates the anatomical diagram of the patient’s heart with the calculated stroke volumes, shunts and regurgitations. All flows in Figure 4 (native aorta, neo-aorta, ascending aorta, TR volume and RV stroke volume) are derived from 4DF data. TR volume was obtained through 4DF at the level of the tricuspid valve annulus. The ascending aortic flow was performed with both phase contrast and 4DF and the results were similar. MRA of the chest demonstrated a patent Fontan with unobstructed flow into the right pulmonary artery and left pulmonary artery, patent DKS and mild narrowing of the aortic arch at the isthmus level of the previously repaired arch.
 Figure 4. Illustration demonstrating the current anatomy of the patient’s heart with the calculated stroke volumes, shunts and regurgitations. A=Lateral tunnel Fontan; I=Aortic Insufficiency; Ao=Native Aortic valve (E); Asc Ao = ascending aorta; B=anomalous left circumflex artery; C=right coronary artery; D=left coronary artery; DKS= Damus-Kaye-Stansell; IVC; inferior vena cava; ml=milliliter; Neo Ao=neo-aortic valve (F); RV= Right Ventricle; SVC=superior vena cava; TR=Tricuspid Regurgitation; VSD= Ventricular Septal Defect with right to left shunt during RV systole. |
Conclusions
CMR with 4DF was able to elucidate the ventriculo-ventricular interactions in this patient with single ventricle physiology. Cine imaging shows earlier LV systole compared to RV systole with an increase in LV size at the end of the RV systole. 4DF imaging confirms that LV has become a sink, siphoning blood from the systemic RV during systole via the large VSD, and hence the LV is compromising his cardiac output. There was discussion about surgical closure of his VSD to improve cardiac output; however, given his significant systemic ventricular dysfunction, he was felt to be a poor surgical candidate. He is now being medically managed with anticoagulation for stroke prevention, diuretics, and goal directed medical therapy. He will likely require transplantation in the future.
Perspectives
CMR is the best imaging modality for evaluating cardiac masses (including thrombi), volumes and flows.[1] However, there are instances the conventional CMR phase contrast flow and volume assessment can be insufficient to explain complex hemodynamics.[1] Four-dimensional flow CMR imaging is one of the leading imaging techniques that can provide comprehensive and accurate assessment of hemodynamics (flow) and morphological disorders of the cardiovascular system simultaneously which can be applied to better understand patients with complex congenital heart disease.[2,3] We used 4DF visualization to better understand the complex physiology of this patient with single ventricle physiology with a larger “second” ventricle “stealing” cardiac output from the primary systemic ventricle, biventricular systolic dysfunction, large outlet VSD and severely reduced cardiac output with MRI flows and volumes showing discrepancy in his calculated ventricular stroke volumes, regurgitation volumes and stroke volume in the ascending aorta.
The 4DF CMR imaging demonstrated right to left shunt across the large outlet VSD occurring during systole and left to right shunt during diastole. By utilizing the 4DF CMR imaging, we were able to establish and calculate the correct hemodynamics and flows between the two ventricles, VSD, valvular regurgitation and ascending aorta. Given the complexity of hemodynamic flow patterns in patients with congenital heart disease (CHD), especially after multiple surgeries resulting in anatomical distortions, 4DF CMR as opposed to single directional velocity encoding through a single plan in 2D-phase contrast CMR can be useful to assess flow patterns. 4DF CMR can be useful for the evaluation of complex CHD including but not limited to left to right shunt calculations in patients with large atrioventricular septal defects, volumetric assessment of peak blood flow velocity in bicuspid aortic valve, accurate direct quantification of left atrioventricular valve regurgitation, assessment of abnormal hemodynamics involved in bicuspid aortic valve, aortic coarctation and Fontan physiology to understand disease process, progression and pathophysiology.[4] One of the major limitations of using 4DF CMR imaging is the extensive post-processing time and the need for specialized user expertise which may limit its routine clinical use.[5,6] Another major limitation of its application in CHD patients is the relatively long scan time duration required to complete study of the heart and its great vessels with adequate spatiotemporal resolution.[4]
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References
- Parato VM, Nocco S, Alunni G, Becherini F, et al. Imaging of Cardiac Masses: An Updated Overview. J Cardiovasc Echogr. 2022 Apr-Jun;32(2):65-75. doi: 10.4103/jcecho.jcecho_18_22. Epub 2022 Aug 17. PMID: 36249434; PMCID: PMC9558634.
- Zhuang B, Sirajuddin A, Zhao S, Lu M. The role of 4D flow MRI for clinical applications in cardiovascular disease: current status and future perspectives. Quant Imaging Med Surg. 2021 Sep;11(9):4193-4210. doi: 10.21037/qims-20-1234. PMID: 34476199; PMCID: PMC8339660.
- Bissell MM, Raimondi F, Ait Ali L, et al. 4D Flow cardiovascular magnetic resonance consensus statement: 2023 update. J Cardiovasc Magn Reson. 2023 Jul 20;25(1):40. doi: 10.1186/s12968-023-00942-z. PMID: 37474977; PMCID: PMC10357639.
- Rizk, Judy. “4D flow MRI applications in congenital heart disease.” European radiology vol. 31,2 (2021): 1160-1174. doi:10.1007/s00330-020-07210-z
- Carrillo H, Osses A, Uribe S, Bertoglio C. Optimal dual-VENC unwrapping in phase-contrast MRI. IEEE Trans Med Imaging. 2019;38(5):1263–1270. doi: 10.1109/TMI.2018.2882553
- Blanken CPS, Westenberg JJM, et al. Quantification of mitral valve regurgitation from 4D flow MRI using semiautomated flow tracking. Radiol Cardiothorac Imaging. 2020;2(5):e200004. doi: 10.1148/ryct.2020200004
Case prepared by
Anna Baritussio, MD, PhD
Department of Cardiac, Thoracic, Vascular Sciences and Public Health
Padua University Hospital, Padua, Italy
