Barlow Syndrome

Functional, constitutional or degenerative disorder of the mitral valve.

Mitral Valve Prolapse; Familial Mitral Regurgitation; Floppy Mitral Valve; Familial Myxomatous Valvular Disease; Myxomatous Mitral Valve Prolapse; Myxomatous Degeneration of the Mitral Valve.

Mitral valve prolapse (MVP) is found in 3 to 5% of adults. The predominance in young female adults disappears in the older population.

In the majority of idiopathic MVP cases, inheritance is autosomal dominant. In some cases, it is linked to chromosome 16p. Penetrance of MVP is variable.

In approximately 80% of cases (typically children or young females), MVP is considered a functional consequence of a valve-ventricle mismatch. In these patients, MVP and mitral regurgitation (MR) tend to resolve slowly over time, and the prognosis is generally good. In a minority of cases (20%), MVP is the result of progressive myxomatous degeneration of the mitral valve leaflets. These patients, mostly males, develop severe MR and eventually left ventricular dysfunction. With worsening MR, progressive pulmonary hypertension ensues. Valve replacement is needed after an average of approximately 25 years.

Echocardiography, family history, and clinical examination. Secondary forms must be excluded.

Typical midsystolic click can be heard in approximately 80% of cases. Common features of functional MVP are recurrent chest pain, dyspnea episodes, palpitations, syncopes, and an increased anxiety level. Individuals with this form of MVP typically have a lean body stature. Complications from functional MVP are rare and include endocarditis, arrhythmias, and probably a slightly increased risk of thromboembolic events. Arrhythmias are of supraventricular origin, or they manifest as premature ventricular contractions. A higher incidence of preexcitation syndromes has been reported. Fortunately, malignant ventricular arrhythmias are rare. In an analysis of 50 patients with sudden cardiac death related to surgery and/or anesthesia, 47 (94%) had cardiac lesions on autopsy, but MVP was found in only one (2%). Atrial fibrillation is common in patients with progressive myxomatous degeneration. Symptoms and complications of pulmonary hypertension and left ventricular dysfunction become more pronounced in advanced disease stages. One child had a cerebrovascular event in a follow-up study of 119 children with MVP. Electrocardiographic recordings were abnormal in 63%, with premature ventricular contraction and T-wave inversion noted most commonly. There was no case of sudden death.

Personal medical history should include palpitations, syncope, anesthesia, and current medication (e.g., beta-blocking agents, anxiolytics, anticoagulants). The electrocardiogram might identify patients with atrial fibrillation or preexcitation syndromes, but is unreliable in terms of predicting arrhythmias during anesthesia. Electrolytes should be in the normal range. Adequate anxiolysis reduces palpitations. The degree of MR and any additional cardiac anomalies should be known; when in doubt, echocardiography may be necessary.

Adequate intravascular filling reduces symptoms of functional MVP. However, fluid administration must be carefully titrated to prevent deterioration of MR. For the same reason, an increase of systemic afterload (vasoconstriction) must be prevented, and vasodilators might be considered as long as normotension is maintained. ...

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