Background
Heart failure is a chronic condition in which the heart cannot pump blood as effectively as the body needs. Many patients with heart failure also experience abnormal heart rhythms, or arrhythmias, such as atrial fibrillation, slow heart rhythms, or dangerous fast rhythms from the ventricles. These rhythm problems can worsen symptoms, lead to hospitalizations, and sometimes require procedures such as pacemaker or defibrillator implantation, medication changes, or ablation.
Despite this importance, the true arrhythmia burden in ambulatory patients with symptomatic heart failure who do not already have a cardiac implantable electronic device is not well defined. A related question is whether a device-guided congestion-management strategy, designed to help clinicians respond earlier to fluid overload, can also influence how often arrhythmias occur.
The ALLEVIATE-HF trial addressed this gap by using continuous insertable cardiac monitor, or ICM, surveillance in patients with recent symptomatic heart failure events.
Study Design
ALLEVIATE-HF enrolled patients with New York Heart Association functional class II to III heart failure, any left ventricular ejection fraction, and a recent heart failure event. Importantly, participants did not have prior cardiac implantable electronic devices.
All patients received an insertable cardiac monitor. They were then randomized to one of two approaches: ICM-guided, physician-directed, nurse-facilitated congestion management, or usual care. In both groups, investigators could access rhythm data, and any arrhythmia-related treatment decisions were made by clinicians rather than by an automated protocol.
The study assessed arrhythmia occurrence over time using Kaplan-Meier methods. It also evaluated whether ICM-detected arrhythmias were associated with later clinical actions, such as medication changes, ablation, or device implantation, and with clinical outcomes including hospitalization and heart failure events. Time-varying Cox models were used to study these relationships.
Who Participated
The analysis included 711 patients. The mean age was 70.5 years, with a standard deviation of 10.4 years, and 45.7% were women. Average follow-up was 17.3 months, with a standard deviation of 8.9 months.
Most participants had heart failure with preserved ejection fraction: 67.9% had an ejection fraction of 50% or greater. At baseline, 60.2% were in NYHA functional class II, meaning they had mild limitation of physical activity but were not severely symptomatic at rest.
Main Findings: Arrhythmia Burden
During the 13-month randomized phase, the occurrence of arrhythmias did not differ between the congestion-management arms. In other words, the study protocol’s device-guided congestion strategy did not appear to reduce or increase arrhythmia burden compared with usual care.
However, the overall arrhythmia burden was substantial when patients were followed longer.
The 3-year overall occurrence of atrial fibrillation was 66.6%, and 25.4% of patients developed new-onset atrial fibrillation. Bradyarrhythmia, meaning abnormally slow heart rhythms, occurred in 47.1% of patients. Ventricular tachycardia or ventricular fibrillation, both potentially serious fast rhythms originating from the ventricles, occurred in 20.1%.
These rates show that clinically relevant rhythm disorders are common in patients with symptomatic heart failure even when they are being followed as outpatients and do not already have implanted rhythm devices.
Clinical Meaning of ICM-Detected Arrhythmias
One of the most important findings was that arrhythmias detected by the insertable cardiac monitor were strongly associated with later clinical action.
Compared with periods without detected arrhythmia, ICM-recorded arrhythmia was associated with a higher likelihood of arrhythmia-related intervention overall, with a hazard ratio of 3.81. Specific associations were even stronger in some rhythm categories: ventricular tachycardia or fibrillation was linked to VT/VF-related interventions with a hazard ratio of 7.04; atrial fibrillation was linked to AF-related interventions with a hazard ratio of 3.28; and bradyarrhythmia was linked to bradyarrhythmia-related interventions with a hazard ratio of 7.22. All of these associations were highly significant.
In practical terms, rhythm events detected by continuous monitoring often led clinicians to take action, such as changing medications, considering anticoagulation for atrial fibrillation, adjusting rate-control therapy, evaluating reversible causes, or referring for electrophysiology procedures.
Association With Hospitalization and Heart Failure Events
ICM-detected arrhythmia was also associated with worse clinical outcomes. Patients with recorded arrhythmias had a higher risk of all-cause hospitalization, with a hazard ratio of 1.79, and a higher risk of heart failure events, with a hazard ratio of 1.69.
This does not prove that the arrhythmias directly caused the events in every case, but it strongly suggests that arrhythmia burden is a marker of clinical instability and a meaningful part of the overall disease course in heart failure.
Therapeutic Procedures
Over follow-up, therapeutic cardiac device implantation occurred in 22.7% of patients, and ablation procedures occurred in 26.1%.
These numbers highlight an important real-world point: continuous rhythm monitoring in heart failure often identifies abnormalities that eventually lead to escalation of care. For some patients, that means implantation of a pacemaker or defibrillator; for others, it means catheter ablation to treat atrial fibrillation or another arrhythmia.
Differences by Ejection Fraction
The study also found important differences in arrhythmia type according to ejection fraction.
Bradyarrhythmias were more common in patients with ejection fraction of 50% or greater. Ventricular tachycardia or fibrillation occurred more often in those with ejection fraction below 50%. Atrial fibrillation was common in both groups, with no major difference in occurrence between them.
These findings fit with the broader understanding that heart failure with preserved ejection fraction and heart failure with reduced or mildly reduced ejection fraction may have somewhat different rhythm profiles, even though atrial fibrillation remains a major issue across the spectrum.
What This Means for Patients and Clinicians
This study suggests that continuous monitoring can uncover a large burden of arrhythmias in patients with recent symptomatic heart failure events, even in the outpatient setting. The arrhythmias were not changed by the study’s congestion-management strategy, but they were clearly linked to subsequent treatment decisions and clinical outcomes.
For clinicians, the findings support close rhythm surveillance in appropriate heart failure patients, especially those with recent decompensation. For patients, the study reinforces that symptoms such as palpitations, dizziness, fainting, worsening shortness of breath, or unexplained fatigue should be taken seriously, because rhythm problems may be contributing even when they are not obvious on a standard office ECG.
At the same time, the results do not mean that every detected arrhythmia requires invasive treatment. The best response depends on the arrhythmia type, symptom burden, stroke risk, heart failure status, and the patient’s overall goals of care. For example, atrial fibrillation may require rate or rhythm control and anticoagulation depending on stroke risk; bradyarrhythmias may require pacing; and ventricular arrhythmias may require more urgent evaluation.
Study Strengths and Limitations
A major strength of ALLEVIATE-HF is the use of continuous insertable cardiac monitoring in a large group of patients with heart failure and recent symptoms. This approach provides much more complete rhythm information than occasional ECGs or short-term monitoring.
There are also limitations. Because arrhythmia data were available to investigators in both trial arms, the study was not designed to isolate the pure effect of blinded monitoring on treatment decisions. Also, while the associations between arrhythmias and outcomes are strong, the observational nature of some analyses means causality cannot be fully confirmed. Finally, the study population was older and predominantly had preserved ejection fraction, so the findings may not apply equally to all heart failure populations.
Conclusion
In ambulatory patients with recent symptomatic heart failure events, a protocol-directed congestion-management strategy did not change arrhythmia burden during the randomized phase. However, continuous insertable cardiac monitoring revealed a high burden of clinically important arrhythmias, including atrial fibrillation, bradyarrhythmia, and ventricular tachyarrhythmia.
These arrhythmias were strongly associated with therapeutic interventions, hospitalization, and heart failure events. The study supports the value of continuous rhythm monitoring as part of comprehensive heart failure care, especially when symptoms or recent decompensation raise concern for clinically meaningful arrhythmias.
