Mitral Valve Chord Rupture in a Pregnant Patient with Uncontrolled Hyperthyroidism: A Unique Case

Hyperthyroidism can have vital clinical consequence regarding the cardiovascular system. We present a very unusual case of a cardiac complication precipitated by both the hemodynamic changes of uncontrolled hyperthyroidism and pregnancy.

Case Description :

The patient is a 36-year-old female at 13 weeks gestation with uncontrolled Graves’ disease recently started on propylthiouracil. She presented to the hospital with progressive shortness of breath, orthopnea, leg swelling, and palpitations. On presentation she was hemodynamically stable but tachycardic. EKG showed atrial flutter with variable A-V block. Laboratory studies were significant for a suppressed TSH of < 0.01 mcIU/mL (ref 0.35-4.94) and an elevated free T4 of 2.42 ng/dL (ref 0.70-1.48). A 2D echocardiogram showed eccentric moderate mitral regurgitation. Right heart catherization demonstrated elevated right and left filling pressures, mildly elevated pulmonary pressures with venous congestion. Given the severity of the mitral regurgitation, a transesophageal echocardiogram was done revealing severe mitral regurgitation with a ruptured chord and a markedly thickened, highly mobile chord. She was treated conservatively with IV diuresis and counseled about her high-risk pregnancy. She was followed as an outpatient by cardiology and endocrinology and switched to methimazole in her second trimester. She was readmitted secondary to preterm premature rupture of membranes at 23 weeks gestation and after a prolonged hospitalization delivered her baby at 28 weeks without major complication. She is pending a decision for definitive treatment for her Graves’ disease.

Discussion :

There is an association between mitral valve prolapse and hyperthyroidism. Myxomatous degeneration of the valve leaflets causes thickening as well as tissue that can rupture with little stress. In pregnancy, cardiac output increases by around 30%, and there is a reduction in systemic vascular resistance. This is similar to the hemodynamics of uncontrolled hyperthyroidism whereby there is elevated preload, increased heart rate and cardiac output, and reduced systemic vascular resistance. Myxomatous degeneration of the mitral valve combined with the hemodynamic changes of uncontrolled hyperthyroidism and pregnancy, together likely precipitated the chord rupture in this patient. There have been cases described of chord rupturing occurring in context of hyperthyroidism, but this is the first case, to our knowledge to describe mitral valve chord rupture in context of both pregnancy and uncontrolled hyperthyroidism.