Effectiveness of pre-surgery ivabradine treatment in patients with manifested thyrotoxicosis

Abstract

Aim. To assess the effectiveness of ivabradine in tachycardia reduction, as a part of the complex pre-surgery treatment of the patients with manifested thyrotoxicosis (TT) and limited indications for β-adrenoblockers (BAB).
Material and methods. In total, the study included 60 patients (23 men, 37 women; mean age 30,1±2,9 years) with manifested TT and limited indications for BAB. After signing the informed consent, all patients were administered ivabradine in the dose of 5-7,5 mg/d for 7-14 days, followed by 5 mg/d for the rest of the pre-surgery period (on average, for 3-4 weeks). In all participants, the following parameters were assessed: blood pressure (BP), mechanic cardiac function, pre-capillary patency, heart rate variability and its mathematical, time, and frequency parameters (cardiointervalography method).
Results. To our knowledge, it was demonstrated for the first time that in patients with manifested thyrotoxicosis, ivabradine therapy decreased sinus node (SN) automatism, improved myocardial contractility and peripheral vascular resistance, and resulted in eukinetic hemodynamic shift. The latter manifested in reduced cardiac ejection volume, left ventricular contractility power, and pulse rate velocity, combined with increased total peripheral vascular resistance and unchanged BP. The change in autonomous heart regulation manifested in substantially increased heart rate frequency oscillations, total heart rate variability, and fast changes in heart rate, as well as in reduced sympatho-parasympathetic index values, which points to the decrease in sympathetic activity due to reduced SN automatism.
Conclusion. Due to selective inhibition of If channels, ivabradine improves cardiac function and also decreases sympathetic activity. In patients with manifested TT, ivabradine could be used as an adequate alternative for BAB in the pre-surgery period.