Adult with Single Ventricle Physiology without Previous Surgical Repairs and History of Endocarditis

Olivia A. Crapanzano¹, Angela J. Weingarten², Jonathan H. Soslow²

¹Department of Pediatrics, ²Division of Pediatric Cardiology, Monroe Carell Jr. Children’s Hospital at Vanderbilt University Medical Center, Nashville, Tennessee, United States of America;

Clinical History:

A 30-year-old male with original anatomy consisting of congenitally corrected transposition of the great arteries with a large inlet ventricular septal defect (VSD), moderate right ventricular hypoplasia, mildly overriding tricuspid valve, and pulmonary valve stenosis presented to an outside hospital with a 2-month history of weight loss, fatigue and cough.

Transthoracic echocardiogram demonstrated a vegetation on the pulmonary valve and multiple blood cultures grew Gemella. He did not meet criteria to have the vegetation removed so completed a 4-week course of antibiotics for endocarditis.[1] He was discharged on IV antibiotics. Follow up with his primary cardiologist after completion of antibiotics demonstrated 4×10 mm vegetation on the pulmonary valve with severe subvalvular and valvular stenosis (peak gradient 99 mmHg, mean gradient of 63mmHg) (Figure 1). The subvalvular and valvular stenosis were unchanged from previous echocardiogram (peak gradient 96 mmHg).

The patient was initially referred to our institution unrepaired at 7 years of age for possible biventricular repair. His Qp:Qs at cath was 2.6:1 but a TEE demonstrated a hypoplastic left-sided right ventricle and overriding tricuspid valve, resulting in a recommendation for either continued observation or single ventricle palliation. Given that he was asymptomatic at the time of the catheterization, observation was chosen. He continued to be followed at the OSH until 14 years old, at which time he transferred care to our institution. At that time, he was asymptomatic, had increased pulmonary stenosis on echocardiogram, and was felt to be clinically well-balanced. His oxygen saturations were low-normal at rest (95-97%) but dropped to the high 80s with activity. At 16 years old, he underwent cardiac catheterization to evaluate his physiology after near completion of his somatic growth. That catheterization demonstrated a well-balanced physiology with a Qp:Qs of 1.6:1, normal pulmonary vascular resistance of 1.1 Wood unit x m2 (WUm2), left ventricular end diastolic pressure (LVEDP) of 11mmHg, and a peak-peak gradient of 65mmHg across the pulmonary valve. He had no additional catheterizations before his presentation with endocarditis.

Figure 1: Transthoracic echocardiographic images in the long axis and short axis prior to and during admission for endocarditis. New echo bright areas consistent with endocarditis delineated by yellow arrows.

CMR Findings:

Eight months after completion of therapy, cardiac magnetic resonance imaging (CMR) was obtained for routine evaluation (there was no prior CMR study for review). CMR, performed on a Siemens 1.5T Avanto Fit, demonstrated l-looped ventricles with a large inlet VSD with membranous and muscular extension (Figure 2A, Movies 1, 2, 3). The subpulmonary left ventricle was moderately dilated with an indexed left ventricular end diastolic volume of 133 ml/m2 (Figure 3). His systemic right ventricle was mildly dilated and appropriately hypertrophied with an indexed end diastolic volume of 118 ml/m2. He had normal biventricular function with a subpulmonary left ventricular ejection fraction of 69% and a systemic right ventricular ejection fraction of 69%. Dephasing jets in the main pulmonary artery suggested pulmonary valve stenosis, and he had severe post-stenotic branch pulmonary artery dilation (Figure 4, Movie 4). There was mild tricuspid regurgitation based on a regurgitant fraction of 7%. He had small patches of late gadolinium enhancement at the inferior wall of the mid-left ventricle (Figure 5). His Qp:Qs was increased at 2.4-2.6:1 based on phase contrast imaging in the aorta and pulmonary artery (main pulmonary artery 239ml; aorta 92ml) and the aorta and branch pulmonary arteries (right pulmonary artery 128ml; left pulmonary artery 92ml; aorta 92ml). The stroke volumes in the left and right ventricles were also increased, with a left ventricular stroke volume of 191 ml and right ventricular stroke volume of 150 ml. There was no ASD and the pulmonary venous return was normal; the larger left ventricular stroke volume than expected was assumed to be secondary to the large VSD, relative RV hypoplasia, and somewhat overriding tricuspid valve (Figure 2B), which it was hypothesized were leading to a physiology more consistent with a single ventricle. Of note, the total ventricular stroke volume was similar to the total arterial stroke volume.

Figure 2: A) 4-chamber view demonstrating l-looped ventricles with left ventricle labeled as LV, right ventricle labeled as RV, and large inlet VSD with muscular and perimembranous extension denoted by * (of note, the perimembranous extension is not visible in this view). The pulmonary veins and left atrium are dilated (suggesting significant left to right shunting) but the RV is relatively hypoplastic compared with the LV. B) 4-chamber view one slice inferior during ventricular filling demonstrating mild tricuspid valve override (tricuspid valve denoted as TV).

Figure 3: Ventricular contours at end diastole (A) and systole (B).

Movie 1: Axial stack scrolling in the caudalcephalad direction. Images demonstrate pertinent anatomy of atrial situs solitus, l-looped ventricles, l-transposed great arteries with a large inlet VSD with muscular and perimembranous extension, pulmonary valve stenosis, and dilated main and branch pulmonary arteries.

Movie 2: Coronal stack scrolling in the anterior/posterior direction. Images demonstrate pertinent anatomy of atrial situs solitus, l-looped ventricles, l-transposed great arteries with a large inlet VSD with muscular and perimembranous extension, pulmonary valve stenosis, and dilated main and branch pulmonary arteries.

Movie 3: 4-chamber view demonstrating l-looped ventricles and large inlet VSD with muscular and perimembranous extension (of note, the perimembranous extension is not visible in this view).

Figure 4: A) Left ventricular outflow tract view demonstrating thickened and doming pulmonary valve leaflets (yellow arrow) with a dephasing jet from the pulmonary valve stenosis. B) Post-stenotic dilatation of the branch pulmonary arteries.

Movie 4: Left ventricular outflow tract view demonstrating thickened and doming pulmonary valve leaflets with a dephasing jet from the pulmonary valve stenosis.

Figure 5: Small patches of late gadolinium enhancement in the inferior wall, the septum, and the anterior and posterior RV insertion points.

Conclusion:

As CMR results were concerning for worsening in left to right shunting, cardiac catheterization was performed confirming the Qp:Qs of 2.5:1 and demonstrating a peak-to-peak gradient of 60mmHg across the pulmonary valve, normal pulmonary artery pressures, a pulmonary vascular resistance of 0.22 WUm2, and a LVEDP of 8 mmHg (Table 1). The patient was discussed in the multidisciplinary adult congenital conference. Options included physiologic repair (VSD repair and relief of pulmonary valve stenosis), anatomic repair (double switch operation), and continued observation.[2]. Observation with close monitoring was chosen. Follow up CMR 2 years later was similar. He continues to undergo surveillance of his biventricular function and ventricular level shunting with annual CMR and cardiac catheterization every 3-5 years to reassess for development of pulmonary hypertension.[3] His most recent echocardiogram demonstrated a decreased peak RVOT gradient at 75mmHg.

Perspective:

This infection likely led to a change in his Qp:Qs from 1.6:1 to 2.6:1, as this was the only known clinical change. We hypothesize that this change was due to a decrease in the pulmonary outflow obstruction from the endocarditis.  Although there was no change in the pulmonary valve gradient on initial echocardiogram, the subsequent echocardiogram performed 2 year later demonstrated a decreased peak and mean gradient. It is unclear if this reflects a slow change over time or inherent variability in the testing.  Another possible explanation is that the catheterization results at 16 y/o were incorrect, though we feel confident in the accuracy of cardiac catheterization results at our institution and think this is an unlikely explanation. 

This case highlights the important additional information that can be gleaned from CMR, particularly a direct measurement of Qp:Qs. Other novel aspects of this case include the hypothesized increase in this patient’s left to right shunting caused by an episode of endocarditis, a complication of endocarditis which we have not previously seen reported. While the patient did not undergo operative repair, the knowledge of this increased shunting prompted closer observation with frequent follow up CMR imaging and cardiac catheterization to assess for progression of chamber dilation, ventricular dysfunction, or increased pulmonary vascular resistance (1).  

This case highlights the clinical and hemodynamic implications of endocarditis in patients with congenital heart disease, the importance of reassessing physiology after a significant event, and the importance of CMR imaging for the assessment of hemodynamics.

Click here to view the entire CMR on CloudCMR.

References:

1. Delgado V, Ajmone Marsan N, de Waha S, et al. 2023 ESC Guidelines for the management of endocarditis. Eur Heart J. 2023;44(39):3948-4042.
2. Spigel Z, Binsalamah ZM, Caldarone C. Congenitally Corrected Transposition of the Great Arteries: Anatomic, Physiologic Repair, and Palliation. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2019;22:32-42.
3. Stout KK, Daniels CJ, Aboulhosn JA, et al. 2018 AHA/ACC Guideline for the Management of Adults With Congenital Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2019;73(12):1494-1563.