Isolated pulmonary valvular stenosis with equilateral triangle orifice

⁎ Corresponding author at: Division of Cardiology, Department of Internal Medicine, Kyoto Social Welfare Foundation Nishijin Hospital, 1035 Mizomae-cho, Kamigyo-ku, Kyoto 602-8319, Japan. pj.ca.m-upk.otok@adonust

Abstract

Isolated congenital pulmonary valvular stenosis is a relatively common abnormality. A 52-year-old woman with an asymptomatic cardiac murmur since her childhood visited our hospital. The peak pressure gradient across the pulmonary valve (PV) was calculated 25 mmHg by Doppler velocity during the transthoracic echocardiography, the severity was graded into mild. The cardiac computed tomography indicated a dome-shaped PV with an equilateral triangle orifice without commissural fusion. No case has been described in a triangle orifice, it will be necessary to follow up carefully.

Introduction

Isolated congenital pulmonary valvular stenosis (PS) is a relatively common abnormality accounting for 7 to 12% of all congenital cardiac abnormalities [1], [2], but may be associated with other conditions such as tetralogy of Fallot, congenital rubella syndrome, and Noonan syndrome [2], [3]. With less severe stenosis, the majority of patients may remain asymptomatic, and are pointed out in adulthood by cardiac murmur and diagnosed by imaging modalities. We present a case of PS with an equilateral triangle orifice, demonstrated by a cardiac multi-detector computed tomography (CT).

Case report

A 52-year-old Japanese woman with an asymptomatic cardiac murmur since her childhood visited our hospital as an outpatient due to intermittent chest pain at rest. She had no smoking habit, no history of rheumatic heart valve disease, and no family history of heart disease or sudden death. She was obese (height: 161 cm, weight: 84 kg), her blood pressure was 130/87 mmHg, and heart rate 79 bpm. Auscultation of the heart resulted in a systolic ejection murmur (Levine grading scale 3/6) maximally audible at the second left intercostal sternal border, and that of lung resulted in no abnormal findings. Abdominal and neurological examination findings were negative, and there was no peripheral edema. An electrocardiogram (ECG) revealed sinus rhythm, and no right ventricular hypertrophy. On her laboratory data, the serum brain natriuretic peptide (BNP) level was slightly increased (BNP: 31.4 pg/mL, upper normal range threshold: 18.4 pg/mL). Chest radiography demonstrated no cardiomegaly (cardiothoracic ratio: 42%), but the pulmonary truncus dilated markedly ( Fig. 1 A). Echocardiography showed a normal size of biventricular chambers with normal contraction, and no signs of pericardial effusion. The pulmonary valve (PV) leaflets could not be revealed clearly. The severity of pulmonary regurgitation (PR) was trivial to mild. The high velocity jet across the PV and secondary dilatation of the main pulmonary artery (PA) were demonstrated ( Fig. 1 B). The peak pressure gradient (PG) can be calculated using the modified Bernoulli equation (peak PG: 25 mmHg by transthoracic Doppler echocardiography). Generally speaking, echocardiography alone frequently remains insufficient in pulmonary valvular disease, especially obese patients.

Chest radiography demonstrated that the pulmonary artery was dilated markedly (A). Echocardiography showed the high velocity jet across the pulmonary valve and turbulent flow in the pulmonary artery (B). Enhanced computed tomography showed the thickened valve and the secondary dilatation of the main pulmonary artery (C), and the triangle orifice of pulmonary valve seen from the arterial aspect in 3-dimensional view (D).

PA, pulmonary artery; RV, right ventricle.

She underwent a cardiac multi-detector CT to assess whether pulmonary valvular disorder was not complicated with coronary artery disease and/or other congenital heart defects. The acquisition of raw data was made using a 64-slice CT (Philips Brilliance 64, Best, the Netherlands). The acquired image was synchronized to the heartbeat, allocated 20 time phases of R-R interval to a cardiac cycle (spatial resolution, 0.45 × 0.45 × 0.80 mm). We could access the reconstructed images in workstation, and rotate the images to evaluate every region of interest from any view. The enhanced CT showed the thickened PV and the secondary dilatation of the main PA ( Fig. 1 C), and the triangle orifice of PV seen from the arterial aspect in 3-dimensional view ( Fig. 1 D). The ECG-gated CT images indicated the immobile triangle structure at the sinotubular (ST) junction level of PV in both systolic phase ( Fig. 2 E), and diastolic phase ( Fig. 2 F). So the valve orifice continued maintaining an equilateral triangle during a cardiac cycle. At the coaptation zone level, tricuspid semilunar valves were too much open excessively in systolic phase ( Fig. 2 C), and coapted against one another centrally in diastolic phase ( Fig. 2 D). In the long-axis view through the right ventricular (RV) outflow tract and PA ( Fig. 2 A, B), the distal edge of leaflet was thick, and fixed the location through all phases of the cardiac cycle ( Table 1 ). The basal part of leaflet (so-called Belly region) was thin, and demonstrated dome-shaped opening in systolic phase ( Fig. 2 A), and the closure with the belly region in diastolic phase ( Fig. 2 B). There was no evidence of the calcification of PV annulus or each leaflet tissue. The three-dimensional schema of present valve was performed by the author’s freehand drawing in reference to a picture of an existing prosthetic valve, rendering systolic phase ( Fig. 2 G), and diastolic phase ( Fig. 2 H). As a result that the leaflet edge was tethered from commissure and linearized without raphe, the configuration of central orifice was formed in the equilateral triangle at ST junction level.

The systolic phase (upper panels) and the diastolic phase (lower panels) of pulmonary valve on electrocardiogram-gated cardiac computed tomography, with 3-dimensional schema. The long-axis view showed a dome-shaped opening (A), and a closure (B). The dotted line indicates coaptation zone level (C in A, D in B), and the broken line indicates sinotubular (ST) junction level (E in A, F in B). At the coaptation zone level, tricuspid semilunar valves opened excessively (arrows in C), and three leaflets closed (D). At the ST junction level, the triangle was surrounded by a straight line to connect each commissure, fixed through the cardiac cycle (E, F). The schema of pulmonary valve has rendering systolic phase (G), and diastolic phase (H). Inset panel shows schematics of coronal cut end at the section indicated by black solid line (rectangle).

Table 1

The thickness and flexibility in parts of semilunar leaflets.

Based on these findings, a diagnosis of isolated PS with triangle orifice was made. Her coronary CT angiography revealed that the principal coronary arteries were intact. PS was associated with poststenotic dilatation of the main PA due to the turbulent flow, but there was no evidence of the hemodynamic consequences of PS, such as RV hypertrophy and RV dysfunction. Because the PS is graded as mild, neither surgical nor catheter-directed treatment was performed. In following up the clinical course carefully, her symptom was relieved.

Discussion

Echocardiography obviously remains a useful and basic tool of imaging routinely used in all patients. Besides echocardiography, the ECG-gated cardiac CT has gained particular importance, the use of currently available imaging modalities in adult congenital heart disease needs to be complementary. However, when studying recent descriptions, PV is the most poorly appreciated of cardiac valves [4]. Transthoracic echocardiography (TTE) is the first-line imaging for valvular disease, however, TTE has technical limitations caused by the body habitus and imaging artifacts by the costal and sternum. Transesophageal echocardiography is infrequently used, however optimal imaging is not often obtained because of farther location of the echo probe from the PV [1]. Cardiac CT is the most preferred imaging modality for pulmonary valvular diseases, except low temporal resolution.

PS can be seen either at the valvular, subvalvular, or supravalvular levels [1], [2], [3], [4]. In a study by Stamm and colleagues, the categories of PS were separated into dome-shaped valves, dysplastic valves, and a third group of less typical cases [5]. In the dome-shaped valves, which had a relatively circular origin of their leaflets, three raphes were tethered to the arterial wall at the ST junction. Most often, there is a typical dome-shaped PV with a narrow central opening but a preserved mobile valve base [5]. On the other hand, the leaflets of the dysplastic valves were attached in a relatively normal semilunar fashion, but stenosis was caused by thickening of the leaflets at their free edges. The present case is included in the dome-shaped valves, but has normal semilunar lines rather than circular line of attachment of the valvular leaflets, and no fusion of the commissures. In addition, previous reports show that the central orifice is formed from the pin-hole [5], or the fish-mouth appearance. Although Rajiah and colleagues [3] found a thickened and restricted PV case which resembled that in our present case, they did not mention the orifice shape or the movement of leaflets during a cardiac cycle.

For comparison, we investigated from the same viewpoint to the aortic valve that should be equally applicable to the PV and its abnormalities. In published review articles of pathogenesis or morphogenesis, a number of differences between aortic and pulmonic congenital semilunar valve disease is described [6], [7], however, no case has been described in the orifice structure of ventriculoarterial valvular stenosis with triangle configuration coexisting domed triple leaflets, whether aortic or pulmonary.

The majority of the moderate or severe PS cases are treated either with a surgical replacement or with a transcatheter intervention, including balloon valvuloplasty and valve implantation [4], [8]. Balloon valvuloplasty is currently recommended for asymptomatic patients with domed valve morphology and peak echo gradient greater than 60 mmHg (mean greater than 40 mmHg) with less than moderate PR and for symptomatic patients with peak echo gradient greater than 50 mmHg (mean greater than 30 mmHg) with less than moderate PR [1], [2], [4], [9]. Patients with isolated, mild PS are usually asymptomatic and their probability of long-term survival is similar to the general population [4]. Also, a stenotic PV may calcify late in life [9]. It will be necessary to follow up carefully because the condition may progress.

Conflicts of interest

The authors declare that there is no conflict of interest.

Funding

This work received no grant from any funding agency in the public, commercial, or not-for-profit sectors.