Background: Evidence is needed on the risks and benefits of combination therapy with levothyroxine (LT4)+liothyronine (LT3) for the treatment of hypothyroidism. Objective and Methods: We performed a randomized, double-blind placebo-controlled study to assess the effects of LT4+LT3 therapy versus LT4+placebo in a homogeneous group of athyreotic patients, without cardiovascular risk factors during long-term replacement monotherapy with LT4. The primary objective of the study was to assess the effects of combination LT4+LT3 therapy on heart rate, cardiac rhythm, and sensitive cardiovascular parameters of cardiac morphology and function by means of electrocardiography and Doppler echocardiography. The secondary objective of the study was to evaluate patient compliance, tolerability, and potential adverse events. Results: Thirty-eight patients with postsurgical hypothyroidism satisfying the inclusion criteria were selected from a group of 300 patients with low-risk thyroid cancer followed for a routine follow-up; they were randomized to receive LT4+LT3 or LT4+placebo. Twenty-four patients were evaluated after 1 year of treatment. All clinical and laboratory parameters were compared with the results obtained from 50 healthy euthyroid volunteers without comorbidities, matched for gender, age, physical activity, and lifestyle. Participants and clinicians remained blinded to the treatment allocation. After 1 year of combination therapy, a significant improvement in the diastolic function, evidenced by a significant reduction in the E/e′ ratio ( p = 0.046) and its positive trend over time, was observed in the LT4+LT3 group versus the LT4+placebo group. In addition, the univariate analyses showed a significant relationship between free triiodothyronine (fT3) levels (in pg/mL) with Δ of variation of the E/e′ ratio in the LT4+LT3 group (standardized β coefficient = 0.603 [confidence interval: 0.001–1.248], p = 0.050) after combination therapy. No adverse events including tachycardia, arrhythmias, atrial fibrillation, or other important events occurred between the first administration and the end of the study. Conclusions: In this preliminary report, combination treatment with LT4+LT3 induced favorable changes in cardiovascular parameters of diastolic function without any adverse cardiovascular events. Trial Registration: EUDRACT number: 2017-001261-25.

Background: Bruton’s tyrosine kinase inhibitors, particularly ibrutinib, have improved outcomes in patients with chronic lymphocytic leukemia but are associated with an increased risk of atrial fibrillation. The early identification of patients with increased susceptibility to atrial fibrillation remains a major challenge in cardio-oncology. Methods: This prospective pilot study included 45 patients with chronic lymphocytic leukemia treated with ibrutinib. All patients underwent comprehensive transthoracic echocardiography at baseline and after 6 months. Left atrial structure and function were assessed, with particular emphasis on speckle-tracking-derived left atrial strain parameters, including peak atrial longitudinal strain and peak atrial contraction strain. Results: At follow-up, a modest but significant increase in indexed left atrial volume was observed, while left atrial functional parameters remained stable. Patients who developed atrial fibrillation showed significantly lower baseline Peak Atrial Contraction Strain values compared with those who remained in sinus rhythm, whereas no significant differences in Peak Atrial Longitudinal Strain were detected. Conclusions: Ibrutinib-related atrial fibrillation appears to be driven primarily by pre-existing atrial vulnerability rather than early drug-induced atrial dysfunction. The baseline impairment of left atrial contractile function may represent a candidate echocardiographic marker of atrial functional vulnerability and may inform cardiovascular surveillance and monitoring strategies in patients treated with ibrutinib.