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A 56-year-old man presented with anasarca and a 40-lb weight gain that had occurred over the course of 3 to 4 weeks. He had a history of permanent atrial fibrillation and a congenital anomaly of the right ventricular inflow tract. This defect consisted of a muscular shelf in the right ventricular inflow tract, which encased the tricuspid subvalvular apparatus in such a manner that it created tricuspid stenosis. The clinical consequences of this anatomic and hemodynamic situation were a massively dilated right atrium, permanent atrial fibrillation, and clinical evidence of right-sided heart failure, including fluid retention and ascites. The patient underwent surgical resection of the muscular shelf, which was followed by progressive resolution of the ascites and fluid retention.
Isolated congenital tricuspid valve stenosis is a rare entity: fewer than 20 cases have been described in the medical literature.1 This stenosis is typically associated with an abnormality of the valvular or subvalvular apparatus, or both. Right ventricular (RV) inflow obstruction due to the presence of an intraventricular muscular shelf has never, to our knowledge, been described. We describe the hemodynamic abnormalities discovered preoperatively in one patient by means of 2-dimensional echocar-diography and right-sided cardiac catheterization. We also describe the novel surgical approach that was used to correct this highly unusual problem in a definitive manner.
A 56-year-old man presented with anasarca, severe groin and sacral hidadenitis in the setting of a known tricuspid valve anomaly, a 2-year history of permanent atrial fibrillation, iron-deficiency anemia, and benign hypertrophy of the prostate. His current medications included digoxin 250 μg once daily, ferrous sulfate 325 mg once daily, torsemide 40 mg once daily, thyroxine 100 μg once daily, tamsulosin 0.4 mg once daily, and warfarin (intended to achieve an international normalized ratio [INR] of between 2 and 3, with regular testing). His physical examination was remarkable for anasarca and bilateral crepitations. His initial laboratory results revealed microcytic anemia with hemoglobin of 9.7 g/dL, bilirubin of 2.5 mg/dL, aspartate aminotransferase of 65 U/L, and an INR of 2.7.
Transthoracic echocardiography revealed severe right atrial dilation associated with a diastolic tricuspid gradient that originated at the level of a large muscle bundle just beneath the tricuspid valve (mean gradient, 8 mmHg). The tricuspid valve displayed normal leaflet motion, but there was mild tricuspid regurgitation (Figs. 1—3).
Cardiac catheterization revealed normal coronary arteries. The right-sided heart study showed a central venous pressure of 20 mmHg with a large V wave of 22 mmHg, a right ventricular pressure of 28/8 mmHg, and a pulmonary artery pressure of 28/18 mmHg. The pulmonary capillary wedge pressure was 11 mmHg with a pulmonary vascular resistance of 144 (dyne · sec)/cm5. The mean tricuspid valve gradient was 8.89 mmHg (Fig. 4).
Magnetic resonance imaging confirmed subvalvular tricuspid stenosis and insufficiency, with a hypoplastic but normally contracting RV.
The patient was taken to the operating room for definitive surgical treatment. At operation, the right atrium was seen to be massively dilated and the RV to be small with normal contractility. The tricuspid valve was stenotic: the septal and anterior leaflets were mobile, but the posterior leaflet was fused to the subvalvular structures. There was a large band of muscle beneath the anterior and posterior leaflets, extending 3 cm into the RV cavity and causing severe inflow obstruction (Fig. 5).
A complete left- and right-sided bipolar radiofrequency maze procedure was performed, and the left atrial appendage was transected and oversewn. The muscle band beneath the tricuspid annulus was found to be heavily calcified and to encase the undersurface of the valve. The inflow obstruction was completely resected, and the valve was replaced with a 29-mm porcine bio-prosthesis (Fig. 6).
Postoperatively, the patient remained in sinus rhythm. When a follow-up echocardiogram was performed after surgery, the mean gradient observed across the tricuspid valve was 2 mmHg.
To the best of our knowledge, this is the first reported case of congenital subvalvular stenosis due to a muscular shelf. Right ventricular inflow stenosis is normally related to the presence of valvular tricuspid stenosis. Isolated tricuspid stenosis can be rheumatic in rare cases,2,3 congenital,3 or of unknown cause.4,5 Right ventricular inflow obstruction can result from valvular abnormalities due to rheumatic heart disease, congenital causes, metabolic or enzymatic abnormalities, and active infective endocarditis.6 Rare causes include carcinoid syndrome, endocarditis, endomyocardial fibrosis, lupus erythematosus, right atrial myxoma, congenital tricus-pid atresia, Fabry disease, and giant blood cysts.
Several conditions can mimic tricuspid stenosis by obstructing flow through the valve. These include supravalvular obstruction from congenital diaphragms, intracardiac or extracardiac tumors, thrombosis or emboli, or large endocarditis vegetations. In addition, other conditions that impair right-sided filling, such as constrictive pericarditis and restrictive cardiomyopathy, can produce similar symptoms and physical findings.
The tricuspid valve leaflets have several embryologic origins. The septal leaflet of the tricuspid valve develops mostly from the inferior endocardial cushion, with a small contribution from the superior cushion. The anterior and posterior tricuspid valve leaflets develop from a shelf of ventricular muscle tissue that extends until the atrioventricular valve junction is reached.7–9 Resorption of that muscle tissue produces normal-appearing valve leaflets and chordae tendineae. Fusion of developing valve-leaflet components results in stenosis (partial fusion) or atresia (complete fusion) of the valve.10,11 Whether muscular tricuspid atresia or well-formed but fused tricuspid valve leaflets develop depends on the embryologic stage at which the aberration takes place.10,11 The classic muscular form of tricuspid atresia develops if the embryologic insult occurs early in gestation. Fused valve leaflets occur if the insult occurs slightly later in gestation. Should valve fusion be incomplete, stenosis of the tricuspid valve develops. In the case presented here, resorption of the muscular shelf was incomplete, which produced leaflet fusion, thereby causing subvalvular tricuspid stenosis.
The surgical correction was approached with the intent of repairing the tricuspid valve. However, as can be seen from the intraoperative photographs, the posterior leaflet was severely scarred, foreshortened, and fused to the annulus. Only the septal and anterior leaflets exhibited mobility—yet both of these leaflets were also restricted by the calcific subannular muscular obstruction, which had foreshortened and fused the subvalvular apparatus in several areas.
Echocardiography provided accurate preoperative views that helped to guide the surgical strategy. The surgical approach used in this case proved successful in eliminating the RV inflow obstruction.
Address for reprints: Seshasayee Narasimhan, MD, MRCP (UK), FRACP, Department of Medicine, Cardiovascular Division, Montefiore-Einstein Heart Center, Jack D. Weiler Hospital of the Albert Einstein College of Medicine, 1825 Eastchester Rd., Bronx, NY 10461-2373