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CLINICAL RESEARCH: THYROID HEART DISEASE

Cardiovascular Manifestations of Hyperthyroidism Before and After Antithyroid Therapy

A Matched Case-Control Study

Division of Medical Sciences, University of Birmingham, Edgbaston, Birmingham, England.

Manuscript received July 5, 2006; revised manuscript received August 8, 2006, accepted August 17, 2006.

^_* Reprint requests and correspondence: Dr. Michael D. Gammage, Department of Cardiovascular Medicine, University Hospital Birmingham NHS Trust, Queen Elizabeth Hospital, Edgbaston Birmingham B15 2TH, England. (Email: m.d.gammage{at}bham.ac.uk).

OBJECTIVES: This study sought to prospectively evaluate the prevalence of cardiovascular abnormalities in patients with overt hyperthyroidism before and after antithyroid therapy.

BACKGROUND: Overt hyperthyroidism is associated with recognized cardiovascular effects believed to be reversed by antithyroid therapy; however, increasing data suggest significant long-term cardiovascular mortality.

METHODS: A total of 393 (312 women, 81 men) consecutive unselected patients with overt hyperthyroidism were recruited and compared with 393 age- and gender-matched euthyroid control subjects. Hyperthyroid patients were re-evaluated after antithyroid therapy. Findings in patients and matched control subjects were compared at presentation, after treatment when patients had subclinical hyperthyroidism biochemically, and when patients were rendered biochemically euthyroid. All had a structured cardiovascular history and examination, including measurements of blood pressure (BP) and pulse rate. All had resting 12-lead electrocardiogram and 24-h digital Holter monitoring of cardiac rhythm.

RESULTS: A higher prevalence of cardiovascular symptoms and signs, as well as abnormal hemodynamic parameters, was noted among hyperthyroid patients at recruitment compared with control subjects. Cardiac dysrhythmias, especially supraventricular, were more prevalent among patients than among control subjects. Palpitation and dyspnea, postural decrease in systolic pressure, and atrial fibrillation (AF) remained more prevalent in treated hyperthyroid subjects with subclinical hyperthyroidism compared with control subjects, and remained more prevalent after restoration of euthyroidism. Predictors for successful reversion to sinus rhythm in those with AF associated with hyperthyroidism were lower BP measurements at recruitment and an initial hypothyroid state induced by antithyroid therapy. Mortality was higher in hyperthyroid subjects than in control subjects after a mean period of follow-up of 66.6 months.

CONCLUSIONS: Cardiovascular abnormalities are common in patients with overt hyperthyroidism at presentation, but some persist despite effective antithyroid therapy.

Abbreviations and Acronyms   AF = atrial fibrillation   BP = blood pressure   ECG = electrocardiogram   IQR = interquartile range   LVH = left ventricular hypertrophy   nsVT = nonsustained ventricular tachycardia   PAF = paroxysmal atrial fibrillation   SVT = supraventricular tachycardia   T4 = thyroxin   T3 = tri-iodothyronine   TSH = thyrotropin

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