Implications of Doppler Echocardiography-guided Heart Rate Modulation Using Ivabradine

Effect of Ivabradine on Left Ventricular Reverse Remodeling in Relatively Stable Heart Failure Outpatients With Reduced Ejection Fraction

Background: Elevations of resting heart rate (HR) in patients with heart failure (HF) with reduced ejection fraction (HFrEF) are often missed, resulting in some patients with an indication for ivabradine reportedly being missed. Methods and Results: We studied 30 relatively stable HFrEF outpatients, and ivabradine was administered when regular follow-up echocardiography showed a resting HR ≥75 beats/min. Significant left ventricular reverse remodeling was observed 10.1±3.9 months after administration of ivabradine. Conclusions: This finding may well make this procedure a potential new approach for preventing worsening of HF for relatively stable patients with HFrEF.

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.

Successful β-blocker introduction under intra-aortic balloon pumping and ivabradine in a patient with new-onset dilated cardiomyopathy and pulsus alternans: a case report

Background

Pulsus alternans has been considered a sign of poor prognosis in patients undergoing treatments for heart failure. However, it may be overlooked in patients with intra-aortic balloon pumps (IABPs). The use of IABP and ivabradine for a β-blocker introduction in a patient with dilated cardiomyopathy (DCM) and pulsus alternans and its consequence have never been reported.

Case summary

In a 16-year-old high school boy with idiopathic DCM [left ventricular end-diastolic diameter (LVDd), 72 mm; left ventricular ejection fraction (LVEF), 18%], the introduction of carvedilol therapy failed, causing cardiogenic shock under inotropes. Therefore, an IABP support was provided, and he was transferred to our hospital. The arterial pressure waveform under IABP demonstrated pulsus alternans with sinus tachycardia at 135/min. Ivabradine reduced the heart rate to ∼100/min and eliminated the pulsus alternans neither decreasing the cardiac index nor increasing the pulmonary artery wedge pressure. Subsequently, carvedilol was reintroduced, and IABP and inotropes were discontinued. Then, 112 days after his transfer to our hospital, left ventricular reverse remodelling was confirmed (LVDd, 54 mm; LVEF, 44%), and he returned to school. The carvedilol dose reached 20 mg/day in 4 months after discharge, and further improvement was observed a year after discharge (LVDd, 54 mm; LVEF, 52%).

Discussion

Pulsus alternans is considered a predictor of poor prognosis. However, IABP and ivabradine may stabilize the haemodynamics in pulsus alternans, leading to a successful β-blocker introduction.

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.

Implication of Ivabradine Therapy in Up-Titrating Beta-Blocker Dose in Patients with Systolic Dysfunction

Ivabradine, which reduces heart rate (HR) without affecting sympathetic nerve activity, improves mortality and morbidity in patients with systolic dysfunction. However, its impact on up-titrating a concomitant beta-blocker dose in such a cohort, via increasing cardiac output and blood pressure and improving tolerability to beta-blockers, remains unknown. In this single-center, prospective, randomized control trial, patients with systolic dysfunction, defined as left ventricular ejection fraction < 50%, sinus rhythm, heart rate > 75 bpm, systolic blood pressure between 90 and 110 mmHg, and New York Heart Association functional class III or IV, who are refractory to up-titration of a beta-blocker due to symptomatic hypotension, dizziness, or worsening heart failure, were assigned to the 20 ivabradine arm or the 20 conventional therapy arm and followed-up for 6 months. The primary outcome is the daily dose of beta-blocker at 6-months follow-up. The secondary outcomes are echocardiographic parameters including overlap between E-wave and A-wave in transmitral diastolic filling flow, plasma B-type natriuretic peptide level, 6-minute walk distance, and heart failure readmission rate. By conducting this study, we hope to demonstrate the clinical benefit of ivabradine therapy in up-titrating beta-blockers and improving clinical outcomes in patients with systolic dysfunction.

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.