Right-sided Pulsus Alternans in Prosthetic Mitral Valve Thrombosis

Pulsus alternans is characterized by alternating strong and weak myocardial contractions in the absence of respiratory or cycle length variations, and is commonly associated with advanced left ventricular dysfunction. The alternation may be seen in the systemic circulation, the pulmonic circulation or in both.¹ Isolated right-sided pulsus alternans has been described in situations with increased pulmonary resistance, right ventricular dilatation, right-sided congestive heart failure or in diastolic left ventricular dysfunction.^2,3 The present case describes a patient with isolated right-sided pulsus alternans as a result of stuck prosthetic mitral valve. To our knowledge, isolated right-sided pulsus alternans in this clinical context has not been previously reported. Case Report. A 26-year-old man was admitted to the hospital because of progressive exertional dyspnea and orthopnea. Several years earlier he had undergone mitral valve replacement (Sorin 29 mm) due to rheumatic mitral valve stenosis. An echocardiogram performed two years prior to admission revealed normal size and function of the left and right ventricles, normal function of the prosthetic mitral valve, mild tricuspid stenosis, mild aortic regurgitation and normal estimated pulmonary pressure. The patient was on chronic warfarin treatment, but his international normalized ratio (INR) values remained below recommended levels most of the time. On admission, the patient appeared mildly dyspneic and tachycardic, with a blood pressure of 95/60 mmHg. His jugular venous pressure was mildly elevated. The lungs were clear. Auscultation of the heart revealed clear prosthetic mitral valve sounds, and a systolic murmur 4/6 was heard at the left lower sternal border. An echocardiographic study of the heart revealed normal size and systolic function of the two ventricles. The prosthetic mitral valve was not visualized well, but an elevated mean gradient of 8 mmHg and an elevated estimated pulmonary pressure of 70 mmHg were detected on pulse doppler studies. A fluoroscopic study revealed limited motion of both leaflets of the prosthetic valve, compatible with a stuck valve. Because of some uncertainty related to the diagnosis, a hemodynamic evaluation was performed. Systemic blood pressure was 100/65 mm Hg. The mean right atrial pressure was 6 mmHg, the peak systolic pulmonary pressure was 52 mmHg and the diastolic pulmonary pressure 27 mmHg. The mean pulmonary wedge pressure was 30 mmHg. Continuous pressure tracings (Figure 1) revealed pulsus alternans in the right ventricle, the pulmonary artery (Figure 1), and in the wedge position , but not in right atrium or in the aorta. At surgery, a thrombus was found at the prosthetic valve, causing obstruction to the leaflet motion and impeding mitral inflow. The valve was replaced with a new prosthetic valve (Carbomedics 29 mm). At a followup echocardiographic study four months later, the prosthetic valve was found to function well, and the estimated pulmonary pressure was within normal limits. Discussion. Isolated right-sided pulsus alternans is an uncommon event. It has been described in diastolic left ventricular dysfunction,^4,5 primary pulmonary hypertension,⁶ pulmonary embolism,⁷ and valvular disease such as mitral stenosis,⁸ or during pulmonic valvuloplasty.⁹ The mechanism underlying pulsus alternans is controversial. The common mechanism proposed for right-sided pulsus alternans in mitral stenosis and diastolic left ventricular dysfunction is an inflow obstruction to the left ventricle, resulting in increased after-load of the right ventricle and increased pulmonary resistance.¹⁰ The mechanism responsible for pulsus alternans in our patient is probably similar to that in mitral stenosis. Our patient had elevated pulmonary artery wedge pressure and pulmonary artery pressure, reflecting an increased pulmonary resistance. The estimated pulmonary pressure hypertension resolved at the echocardiographic examination performed after valve replacement, implicating the stuck valve as the causative factor.