Our study in 67 patients with ATAs and ADHF who were treated with intravenous landiolol had the following findings: (1) intravenous landiolol reduced the heart rate without markedly reducing blood pressure or leading to a deterioration in HF or cardiac function, (2) sinus rhythm was spontaneously restored in 15 (22%) patients during landiolol treatment, (3) patients with an LVEF of ≥ 40% showed a greater decrease in heart rate than those with an LVEF of < 40% despite a similar dose of landiolol, (4) approximately 70% of the discharged patients were in sinus rhythm, and (5) several landiolol-related adverse effects, such as hypotension, were observed.
Rate Control in the Acute Setting
In the acute setting of HF with rapid ATAs, β-blockers are useful for rate reduction and are preferred over digoxin due to their effectiveness in the setting of high sympathetic tone [9]. The use of β-blockers clearly requires an incremental dosage to achieve a heart rate that balances the need for rate control with other hemodynamic parameters [9]. Β-Blockers have negative inotropic and blood pressure-lowering effects and are thus of limited use, especially when administered intravenously, in ADHF patients with reduced LV systolic function and/or low blood pressure.
In our study, the maintenance dose of landiolol was attained at a median of 6 h after the start of treatment and significantly reduced the heart rate without markedly reducing blood pressure. Landiolol has high cardioselectivity and exhibits a higher heart rate-lowering potency and a slightly more potent negative chronotropic effect with a less potent negative inotropic effect than esmolol [14]. The effect of landiolol appears early after the initiation of treatment and rapidly stabilizes because of its pharmacokinetic properties, such as its relatively small volume of distribution and short elimination time.
Kobayashi et al. reported that low doses (1.0–2.0 μg/kg/min) of intravenous landiolol reduced the heart rate while maintaining blood pressure in patients with rapid atrial fibrillation and ADHF without adverse events, such as hypotension or HF deterioration [21]. In addition, Adachi et al. reported that intravenous landiolol significantly reduced the heart rate during ATAs in patients with ADHF and a low LVEF despite the frequent concomitant use of intravenous inotropic drugs [22]. Of our patients, three received concomitant administration of intravenous dobutamine, and three received intra-aortic balloon pumping while their heart rates were reduced during landiolol therapy without leading to a marked reduction in blood pressure.
LVEF ≥ 40% Versus LVEF < 40%
The ESC guidelines state that the drug choice for acute heart rate control in AF depends on the LVEF; β-blockers are the first-line treatment for patients with an LVEF of ≥ 40% or < 40% [13]. Our patients with ATAs and ADHF included 24 patients with an LVEF of ≥ 40%. In our study, there was a greater decrease in heart rate in patients with an LVEF of ≥ 40% than in those with an LVEF of < 40% despite a similar maintenance dose of landiolol. Kobayashi et al. reported that HF patients with an LVEF of < 50% experienced a greater decrease in the heart rate than HF patients with an LVEF of ≥ 50% 1–2 h after the start of landiolol treatment, although there was no difference at later time points [21]. Ozaki et al. reported that HF patients with an LVEF of ≥ 40% showed a greater decrease in heart rate than HF patients with an LVEF of < 40% after the start of a similar dose of landiolol [23]. Patients with an LVEF of ≥ 40% are more likely to experience the heart rate-lowering effect of landiolol than those with an LVEF of < 40%. Particularly in patients with severe LV systolic dysfunction (LVEF ≤ 30%) and an inherent increased risk of adverse cardiac events and mortality, landiolol therapy could be continued without hemodynamic worsening, and the LVEF values of these patients were subsequently improved after landiolol therapy.
However, it may be important to characterize LV systolic function when initiating landiolol treatment [19]. Wada et al. reported that an extremely low LVEF (< 25%) was a predictor of inadequate heart-rate lowering during landiolol therapy and was associated with the development of adverse events, such as hypotension [24].
Outcomes
Landiolol has a role in reliably lowering the heart rate and improving hemodynamics and the condition of ADHF. As a result, 22% of the patients exhibited a spontaneously restored sinus rhythm, and when defibrillation was added, 42 of the 67 patients showed a restored sinus rhythm during hospitalization. In HF patients, sympathetic activity is increased, and the stimulation of β-adrenergic receptors alters the activity of several ion channels and transporters and leads to arrhythmogenesis related to cardiomyocyte Ca2+ handling [25, 26]. Β-Blockers operate through multiple antiarrhythmic mechanisms via changes in action potentials or membrane currents induced by the suppression of various ion channels. Landiolol may be effective in treating ATAs caused by an increased sympathetic drive in HF.
After landiolol therapy, further enhancements to the basic therapy for HF, such as the use of β-blockers and renin-angiotensin-system inhibitors, pharmacological or electrical cardioversion, and additional rhythm control strategies, such as oral amiodarone administration and catheter ablation, were provided. Forty-one (69%) of the 59 patients who were alive at discharge were in sinus rhythm. Of these patients, 24 (59%) patients experienced a recurrence of ATAs after discharge. However, since there was no difference in the incidence of rehospitalization due to worsening HF between patients with and without recurrent ATAs (3/24 vs. 2/17), recurrent AF might not be associated with a poorer prognosis of patients with recurrent ATAs. In patients with ATAs and ADHF, the restoration of sinus rhythm improves hemodynamics and cardiac function, and additional therapy for the restoration and preservation of sinus rhythm may lead to the prevention of HF exacerbation and the subsequent improvement in prognosis.
In the acute setting, there is a high recurrence in patients in whom initial cardioversion is successful [12]. In this situation, landiolol may be useful as the first-line therapy for improving the hemodynamic status by lowering the heart rate. After the cardiac status is stabilized, subsequent cardioversion and rhythm control therapy, such as catheter ablation, will be effective, although sinus rhythm cannot be restored during landiolol treatment. Of our patients who were alive at discharge, approximately 70% were in sinus rhythm; these patients showed a lower frequency of subsequent rehospitalization due to worsening HF. The restoration of sinus rhythm is essentially related to prognosis in patients after discharge. However, it is difficult to restore and maintain sinus rhythm in patients with deteriorated hemodynamics. It is necessary to stabilize hemodynamics by rapidly controlling the rate of ATAs in ADHF. Landiolol may reliably lower the heart rate during ATAs in ADHF patients without the deterioration of hemodynamics.
Patients with ATAs and ADHF often have a concomitant systemic illness, such as an infectious disease. Among our patients, more than half of the deaths that occurred were from non-cardiac causes. In these cases, the treatment of ATAs and HF does not necessarily improve the prognosis; however, it may contribute to stabilizing the circulation.
Adverse Effects
Wada et al. reported that hypotension was often observed (in approximately 10% of cases) as an adverse effect in patients with arrhythmia who received intravenous landiolol, and that hypotension was associated with a lower LVEF [24]. In our study, two patients experienced hypotension during therapy; however, their blood pressure recovered after the discontinuation of landiolol. During the use of landiolol, blood pressure should be carefully monitored in patients with low blood pressure or a low LVEF. Therefore, landiolol is useful as a rate control treatment for rapid ATAs in the acute setting of ADHF.
Study Limitations
There are several limitations in this study. First, this study was a single-center non-comparative, retrospective observational study. Therefore, treatment bias existed. We could not evaluate the relationship between the recurrence of ATAs and the outcome. It is difficult to obtain the exact time to the recurrence of ATAs or the frequency of ATAs based on the patient’s symptoms and routine ECGs in clinical practice. Second, landiolol has been used only in Japan for 15 years, and the generalizability of our results to Japanese patients is limited to clinical practice in Europe and other countries. Third, the clinical characteristics of the subjects varied, and the number of subjects was small. Therefore, a subgroup analysis was not feasible.