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Usefulness of L-thyroxine to improve cardiac and exercise performance in idiopathic dilated cardiomyopathy
P Moruzzi1, E Doria, P G Agostoni
1Istituto di Cardiologia, University of Milan, Italy.
Insights
Short-term L-thyroxine improved cardiac function and exercise capacity in idiopathic dilated cardiomyopathy patients. This thyroid hormone treatment enhanced heart performance without altering adrenergic support or peak exercise hemodynamics.
Area of Science:
- Cardiology
- Endocrinology
- Pharmacology
Background:
- Idiopathic dilated cardiomyopathy (IDC) is a chronic heart failure condition.
- The role of thyroid hormones in heart failure is complex and not fully understood.
- Short-term interventions are crucial for managing IDC symptoms and improving quality of life.
Purpose of the Study:
- To evaluate the short-term effects of L-thyroxine on cardiac function and exercise performance in patients with IDC.
- To compare L-thyroxine's efficacy against a placebo in IDC patients.
- To investigate the impact of L-thyroxine on hemodynamic parameters and adrenergic support.
Main Methods:
- A randomized, placebo-controlled study involving 20 patients with IDC.
- Hemodynamic assessments (control and dobutamine infusion) and cardiopulmonary exercise tests were performed.
- Echocardiography and plasma thyroid hormone levels were measured before and after treatment.
Main Results:
- L-thyroxine significantly improved left ventricular ejection fraction and cardiac contractility.
- Systemic vascular resistance decreased, and cardiac output increased with L-thyroxine treatment.
- Exercise capacity improved, independent of changes in adrenergic support or peak exercise hemodynamics.
Conclusions:
- Short-term L-thyroxine administration enhances cardiac and exercise performance in IDC patients.
- The observed benefits are independent of adrenergic influences.
- L-thyroxine represents a potential therapeutic option for improving outcomes in chronic heart failure.
Abstract:
The short-term effects of L-thyroxine (100 micrograms/day, 10 patients) and placebo (10 patients) on idiopathic dilated cardiomyopathy were compared. Before and at the end of the treatment, a hemodynamic study was performed in the control state and during dobutamine infusion. A cardiopulmonary exercise test was also performed with hemodynamic monitoring. An echocardiogram was recorded in the control state and during acute changes of left ventricular afterload. Plasma levels of triiodothyronine, thyroxine, thyroid-stimulating hormone and norepinephrine were measured. Placebo was ineffective. After administration of L-thyroxine all patients had normal thyroid function. The increase in left ventricular ejection fraction and the rightward shift of the slope of left ventricular ejection fraction/end-systolic stress relation (p < 0.05) indicated an improvement in the cardiac inotropic state. This proved to be independent of adrenergic influences by the unchanged beta 1 response to dobutamine. A decrease in resting systemic vascular resistances and an increase in cardiac output (p < 0.05) were also observed. Cardiopulmonary effort parameters improved (p < 0.05) without hemodynamic changes at peak exercise. It is concluded that L-thyroxine short-term administration improves cardiac and exercise performance in patients with chronic heart failure, without modifying the adrenergic support to the heart and the circulatory parameters at peak exercise.