Impact of optimal heart rate on left ventricular reverse remodeling and functional improvement in patients with systolic heart failure

Clinical Implications of Ivabradine in the Contemporary Era

Ivabradine is a recently introduced inhibitor of the If ion channel, which exhibits the capacity to reduce heart rate while preserving hemodynamic stability. At present, ivabradine finds its clinical indication in patients suffering from heart failure with reduced ejection fraction and maintaining a relative sinus rhythm refractory to beta-blockers. To optimize heart rate control, it is recommended to pursue an aggressive up-titration of ivabradine. This approach may ameliorate tachycardia-induced hypotension by incrementally enhancing cardiac output and allow further up-titration of agents aimed at ameliorating heart failure, such as beta-blockers. Both the modulation of heart rate itself and the up-titration of agents targeting heart failure lead to cardiac reverse remodeling, consequently culminating in a subsequent reduction in mortality and morbidity. A novel overlap theory that our team proposed recently has emerged in recent times. Under trans-mitral Doppler echocardiography, the E-wave and A-wave closely juxtapose one another without any overlapping at the optimal heart rate. Employing echocardiography-guided ivabradine for heart-rate modulation to minimize the overlap between the E-wave and A-wave appears to confer substantial benefits to patients with heart failure. This approach facilitates superior cardiac reverse remodeling and yields more favorable clinical outcomes when compared to those patients who do not receive echocardiography-guided care. The next pertinent issue revolves around the potential expansion of ivabradine's clinical indications to encompass a broader spectrum of diseases. It is imperative to acknowledge that ivabradine may not yield clinically significant benefits in patients afflicted by heart failure with preserved ejection fraction, acute heart failure, sepsis, or stable angina. An important fact yet to be explored is the clinical applicability of ivabradine in patients with atrial fibrillation, a concern that beckons future investigation. In this review, the concept of overlap theory it introduced, along with its application to expand the indication of ivabradine and the overlap theory-guided optimal ivabradine therapy.

Doppler Echocardiography-Guided Heart Rate Modulation Therapy Using Ivabradine in a Patient with Systolic Heart Failure

Heart rate reduction using ivabradine, a selective If channel blocker that purely decreases heart rate without affecting hemodynamics, improves clinical outcomes in patients with systolic heart failure. However, the ideal heart rate that should be a target remains unknown. Our team recently proposed a methodology using Doppler echocardiography to estimate ideal heart rate, at which E-wave and A-wave stand adjacent without overlap. However, the implication of Doppler echocardiography-guided heart rate modulation therapy using ivabradine remains uncertain. We had a 72-year-old man with systolic heart failure and sinus tachycardia who initiated ivabradine therapy. Ivabradine dose was adjusted between 5.0 mg/day and 10.0 mg/day and continued for 12 weeks to minimize the overlap between the two echocardiography waves, accompanying improvement in cardiac output, left ventricular ejection fraction, plasma B-type natriuretic peptide, and six-minute walk distance. Doppler echocardiography-guided heart rate regulation therapy using ivabradine may be a promising strategy to improve cardiac function and clinical outcomes in patients with systolic heart failure, although further studies are required to validate this hypothesis.

Personalized Target Heart Rate for Patients with Heart Failure and Reduced Ejection Fraction

The optimal heart rate (HR) in patients with heart failure with reduced ejection fraction (HFrEF) has been ill-defined. Recently, a formula was proposed for estimating the target heart rate (THR), which eliminates the overlap between the E and A wave (E-A overlap). We aim to validate its prognostic significance in the multicenter WET-HF registry. This study used data from 647 patients with HFrEF hospitalized for acute decompensated HF (ADHF). The patients were divided into the 2 groups by THR. The primary endpoint was defined as the composite of all-cause death and ADHF readmission. The THR successfully discriminated the incidence of the primary endpoint, whereas no significant difference was observed in the primary endpoint when dividing the patients by uniform cutoff 70 bpm. HR at discharge ≤ THR was inversely associated with the primary endpoint. Restricted cubic spline analysis demonstrated the difference between HR at discharge, and THR (ΔHR) from -10 to ±0 was associated with a lower risk of primary endpoint and ΔHR from ±0 to +15 was associated with a higher risk. THR discriminated long-term outcomes in patients with HFrEF more efficiently than the uniform cutoff, suggesting that it may aid in tailored HR reduction strategies.

Optimal Heart Rate Modulation Using Ivabradine

Heart rate modulation therapy using ivabradine improves mortality and morbidity in patients with systolic dysfunction. However, a target heart rate remains uncertain. Echocardiography-guided ivabradine therapy, in which we attempt to approach zero overlap between two diastolic filling inflow waves, has recently been proposed to maximize cardiac output, facilitate reverse remodeling, and reduce mortality and morbidity, instead of using an absolute value for the target heart rate. Prospective studies are needed to validate the clinical implication of these therapeutic strategies. Also, this concept should be expanded to other clinical scenarios.