Context: Recent reports suggest an association between hyperthyroidism and pulmonary hypertension (PHT), although the potential mechanisms and clinical implications remain unclear.
Objective: Our objective was to determine the prevalence of PHT related to hyperthyroidism and the associated hemodynamic changes and outcome.
Methods and results: We performed serial echocardiographic examinations in 75 consecutive patients with hyperthyroidism (43 +/- 2 yr, 47 women) to estimate pulmonary artery systolic pressure (PASP), cardiac output (CO), total vascular resistance (TVR), and left ventricular (LV) filling pressure. Examinations were performed at baseline and 6 months after initiation of antithyroid treatment. Results were compared with 35 age- and sex-matched healthy controls. All hyperthyroid patients had normal LV systolic function, and 35 patients (47%) had PHT with PASP of at least 35 mm Hg. There were no significant differences in the clinical characteristics of hyperthyroid patients with or without PHT (all P > 0.05). Nonetheless, those with PHT had significantly higher CO, PASP, peak transmitral early diastolic flow velocity (E), and ratio of E to early diastolic mitral annular velocity (E') compared with those without PHT and controls (all P < 0.05). Hyperthyroid patients with PHT also had significantly lower TVR than controls (P < 0.05). Among the 35 hyperthyroid patients with PHT, 25 (71%) had pulmonary arterial hypertension (PAH) with normal E/E', and 10 (29%) had pulmonary venous hypertension (PVH) with elevated E/E'. Hyperthyroid patients with PAH had a significantly higher CO and a lower TVR compared with those with PVH. In contrast, hyperthyroid patients with PVH had lower E' and a higher E/E' ratio compared with those with PAH. These hemodynamic abnormalities and PHT were reversible in patients with PAH or PVH after restoration to a euthyroid state.
Conclusion: In patients with hyperthyroidism and normal LV systolic function, up to 47% had PHT due to either PAH with increased CO (70%) or PVH with elevated LV filling pressure (30%). Most importantly, hyperthyroidism-related PHT was largely asymptomatic and reversible after restoration to a euthyroid state.