Enhanced left ventricular diastolic function in hyperthyroidism: noninvasive assessment and response to treatment

Area of Science:

• Cardiology
• Endocrinology
• Physiology

Background:

• Hyperthyroidism significantly impacts the cardiovascular system, with potential links to heart conditions like cardiomegaly and heart failure.
• While systolic function may be enhanced in hyperthyroidism, the effects on diastolic function have been less clear.

Purpose of the Study:

• To noninvasively assess diastolic ventricular performance in newly diagnosed, untreated hyperthyroid patients.
• To compare diastolic function parameters between hyperthyroid patients and a control group.
• To evaluate the effects of beta-adrenergic blockade and achieving a euthyroid state on diastolic function.

Main Methods:

• Studied nine untreated hyperthyroid patients and an age/sex-matched control group.
• Measured diastolic flow velocities, isovolumic relaxation time (IVRT), and diastolic flow deceleration rate.
• Repeated measurements after beta-adrenergic blockade and upon achieving a euthyroid state.

Main Results:

• Untreated hyperthyroid patients showed a significantly shorter IVRT (33.0 ms vs. 57.9 ms) and enhanced left ventricular relaxation.
• Beta-adrenergic blockade reduced heart rate but did not significantly alter IVRT.
• Euthyroid patients exhibited normal IVRT (51.7 ms) and diastolic performance comparable to controls.

Conclusions:

• Hyperthyroidism is associated with enhanced, not compromised, cardiac diastolic performance.
• The findings do not support the hypothesis of impaired left ventricular function in thyrotoxicosis.
• Cardiac symptoms in hyperthyroidism might arise from noncardiac mechanisms.