Normal Functioning Tilting Disc Aortic Valve in Its Fourth Decade

Introduction

A 48-year-old male patient presented to the outpatient department with symptoms of exertional dyspnea for a few months. He had been previously diagnosed with rheumatic heart disease (RHD) during childhood and had undergone aortic valve replacement (AVR) with a mechanical prosthetic heart valve (PHV) in October 1988 (at 12 years of age) at another institution. The surgery was performed for possible severe aortic stenosis. Unfortunately, no previous surgical records were available with the patient. He had no other comorbidity and was on oral anticoagulation with warfarin (international normalized ratio (INR) mostly in the range of 2.0-2.5) and tablet enalapril for several years. On clinical examination, the patient was hemodynamically stable and in sinus rhythm. Both opening and closing clicks of the PHV were audible on auscultation, with no abnormal associated murmurs noted. The first heart sound was accentuated, with a mid-diastolic rumbling murmur noted at the apex.

Transthoracic echocardiography (TTE) revealed a metallic PHV at aortic position, possibly of tilting disc morphology (Figure 1). Due to intense acoustic shadowing, further delineation of the nature of PHV was not possible. The peak/mean pressure gradient across the valve was 21/11 mmHg, V_max of 2.28 m/s, with an early peaking triangular continuous wave Doppler (CW) contour. The acceleration time (AT) of the CW jet was 69 ms and aortic ejection time (ET) was 254 ms. The AT/ET ratio was 0.27. The Doppler velocity integral (DVI) was 0.44, while the calculated effective orifice area by the continuity equation was 1.25 cm². Mild aortic regurgitation (AR) was noted. No paravalvular AR, thrombus/vegetation was noted.

OPEN IN VIEWER Figure 1.

Transthoracic Echocardiography Showing Aortic Prosthetic Heart Valve (PHV) and Rheumatic Mitral Stenosis (a), Closed PHV with Mild Valvular Aortic Regurgitation (AR) (b), Severe Mitral Stenosis by Planimetry (c), Pressure Gradient Across PHV (d).

The mitral valve (MV) was thickened with anterior mitral leaflet (AML) doming in diastole and posterior mitral leaflet (PML) restricted. No significant calcification was noted in the valve leaflets or commissures. The peak/mean pressure gradient across the MV was 37/20 mmHg. The planimetered MV area (MVA) was 1.19 cm², suggestive of severe mitral stenosis (MS). Mild mitral regurgitation (MR) was noted. The calculated Wilkins’ score of MV was 7. The left atrium was dilated (5.4 cm). Concentric left ventricular hypertrophy was present, with other cardiac chamber dimensions within the normal range. The left ventricular systolic function was normal with an ejection fraction of 55%. There was mild tricuspid regurgitation (TR), with a resting calculated pulmonary artery systolic pressure (PASP) of 33 mmHg.

Transesophageal echocardiography (TEE) confirmed the findings of RHD, severe MS, and mild MR, with a valve appearing suitable for balloon mitral valvotomy (BMV). There was no left atrial appendage (LAA) thrombus. The aortic tilting disc PHV was better appreciated on TEE; however, acoustic shadowing was still noted (Figure 2, Supplemental Video Files 1-4). A valve size of 27-29 mm was estimated. No obvious thrombus, vegetation, or significant pannus ingrowth was noted. A mild valvular AR was seen.

OPEN IN VIEWER Figure 2.

Transesophageal Echocardiography Demonstrates Closed (a, b) and Open (d, e) Aortic Prosthetic Heart Valve (PHV) on Long and Short Axis Views, Mild Valvular Aortic Regurgitation (AR) (c), Color M-mode Image Showing AR (f).

Fluoroscopy confirmed the PHV as Björk–Shiley valve (BSV) at aortic position, with a stable prosthesis (Figure 3, Supplemental Video Files 5 and 6), possibly of concavo-convex disc morphology. Normal excursion of the tilting disc was appreciated, with an opening angle of 70° (Figure 4). Subsequently, the patient underwent a successful, uncomplicated BMV procedure, with >50% increase in MVA from baseline and no increase in severity of MR.

OPEN IN VIEWER Figure 3.

Fluoroscopic Still Images Showing Aortic Prosthetic Heart Valve (PHV) at Closed and Open Positions in Anteroposterior Projection (a, b) and Right Anterior Oblique Projection (c, d).

OPEN IN VIEWER Figure 4.

Three-dimensional En-face View of Aortic Prosthetic Heart Valve (PHV) on Transesophageal Echocardiography (TEE) (a), Valve Dimension on TEE (b) and Opening Angle 70° (c).

Our patient has had a normal functioning BSV at aortic position for 36 years, despite having a subtherapeutic INR (a higher target INR of 3.0-4.0 being recommended by current guidelines for older generation PHV).^{1, 2} In one of the largest studies involving Doppler parameters of normal functioning aortic BSV in 141 patients, the normal range of peak velocity of 2.5 ± 0.6 m/s, mean gradient of 13.9 ± 7.0 mmHg, and DVI of 0.40 ± 0.10 were noted. ³ Our patient’s PHV Doppler echocardiographic findings were within this range, suggestive of a normal functioning prosthesis.

Previous case reports have described normal functioning older generation tilting disc aortic PHV 4-5 decades after implantation, with the longest reported case of 48 years post-AVR.^4–7 There have been scarce case reports of normal functioning older generation PHVs from India, despite cardiologists encountering such patients during clinical practice. The longest reported tilting disc PHV in an Indian patient had been implanted at the mitral position 33 years before redo surgery for PHV dysfunction. ⁸

However, our patient is unique in that he underwent AVR in the pediatric age group. Despite the limitations of achieving therapeutic INR levels and adequacy of testing, the patient never had any thromboembolic complications or structural valve deterioration, which is a rare finding in itself. The valve has demonstrated successful performance during 1.5 billion cardiac cycles over 36 years (assuming an average heart rate of 80 beats/min), far exceeding the fatigue test durability limit of 140 million cardiac cycles. ⁷

This case highlights the need for cardiologists and imaging specialists to be alert toward the possibility of encountering patients with older generation PHV during clinical practice. BSV was withdrawn from the market from 1986 onwards. There have been reports of late structural deterioration and outlet strut fractures (OSFs) of the BSV at a rate of 0.02%-0.04% per year. ⁹ Risk factors predisposing to OSF include younger age, larger valve, opening angle of 70°, and implantation at the mitral position. ⁹ Consequently, prophylactic replacement of these valves with current generation valves has been suggested. An individualized approach is required, balancing between the risk of OSF and loss of life expectancy versus the risk of reoperation and gain in life expectancy. ¹⁰

Current guidelines recommend a higher target INR in these patients owing to enhanced thrombogenicity as compared to the newer generation valves.^{1, 2} Such patients must be counseled about the need for optimum anticoagulation and to report immediately on development of new symptoms. Echocardiographic evaluation is indicated on emergence of new symptoms or clinical suspicion of prosthetic valve dysfunction. A multi-imaging approach using TTE, TEE, and cinefluoroscopy/cardiac computed tomography must be pursued for diagnosing prosthetic valve dysfunction.