We analyzed all cases with AF in the German Armed Forces over a 34-year period from a clinical and occupational perspective. To the best of our knowledge, this is the largest analysis of AF in military aircrew in Europe. The United States Air Force Aerospace Waiver Guide Compendium mentions a five-year review by the Aeromedical Information Management Waiver Tracking System through 2020 including 76 cases of AF/atrial flutter, 10 of which were disqualified. According to the same source, there is an Aeromedical Consultation Service Atrial Fibrillation Working Group currently following 168 cases [28]. In 2013, Hunter et al. published a five-year review of AF in the British Royal Air Force with 23 AF cases [15]. Military aircrew are highly selected for medical fitness and occupational aptitude, and they are regularly screened for disease incompatible with flight safety. The incidence of AF is therefore much lower than in an unselected general population [2, 9, 18]. Regarding record identification numbers and yearly examination numbers, it can roughly be estimated that between 20,000 and 25,000 aircrew were examined at the GAFCAM in the analyzed 34-year period. Out of these, 42 had AF. The incidence of AF increases with age [22], and none of the analyzed aircrew was older than 62 years at initial diagnosis. Besides differences in AF incidence, the peculiarity of the analyzed collective also led to differences in AF characteristics. Most of our cases were single AF episodes, often caused by an identifiable precipitant, or paroxysmal AF. Stroke risk was mostly low, and only few aircrew needed permanent anticoagulation.

Aeromedical concerns of AF include palpitations, dizziness, shortness of breath, presyncope, syncope, exercise intolerance, haemodynamic instability, and stroke risk. The loss of atrial contribution to cardiac output, loss of atrioventricular synchrony, and the rapid ventricular response during an episode may impair cardiac performance, especially during exertion, and can be acutely distracting or incapacitating [10].

Aeromedical regulations for aircrew with AF are complex and vary between civilian and military licensing authorities of different countries. According to European Union regulations [5] professional pilots (class 1) with AF must be referred to the licensing authority, private pilots (class 2) must be assessed in consultation with licensing authority. For initial class 1 and ATCO applicants, a fit assessment should be limited to those with a single episode of arrhythmia which is considered by the medical assessor of the licensing authority to be unlikely to recur. For revalidation, applicants may be assessed as fit, class 1 pilots with an OML, if cardiological evaluation is satisfactory and the stroke risk is sufficiently low [7]. Anticoagulation is allowed with vitamin K antagonists and with direct oral anticoagulants (DOAC). Class 2 applicants with AF may be assessed as fit if cardiological evaluation is satisfactory and the stroke risk is sufficiently low. In case of anticoagulation with a vitamin K antagonist a safety pilot limitation is required. If anticoagulated with DOACs, such a limitation is not necessary. After catheter ablation class 1 pilots are primarily unfit for flying. A fit assessment may be considered following successful catheter ablation and should require an OML for at least one year, unless an electrophysiological study, undertaken at a minimum of two months after the ablation, demonstrates satisfactory results. For ATCO a fit assessment may be considered after a minimum of two months following successful catheter ablation provided an electrophysiological study has demonstrated satisfactory results [6]. For class 2 pilots a fit assessment may be considered following successful catheter ablation subject to satisfactory cardiological review undertaken at a minimum of two months after the ablation [7].

According to the regulations issued by the US Federal Aviation Authority (FAA) in most cases a deferral and a FAA decision is required. The aeromedical examiner (AME) has to provide detailed information by a Non-Valvular Atrial Fibrillation Initial or Recertification Status Report. In case of a positive decision a Special Issuance is issued by the FAA [8].

In the German Armed Forces all aircrew with atrial fibrillation with or without catheter ablation are unfit for flying [17]. Based on an individual decision, a waiver can be granted by the GAFCAM.

In the US Air Force, a history of atrial fibrillation is disqualifying for all flying classes and retention. The one exception is a single episode of atrial fibrillation clearly associated with a reversible cause. Additionally, the use of maintenance medications for the treatment or prevention of major rhythm disturbances including atrial flutter or atrial fibrillation requires a waiver for retention and all flying classes. A history of catheter ablation is also disqualifying for all flying classes [28]. Waivers for recurrent AF without hemodynamic symptoms may be granted for trained aircrew, but not for initial pilot applicants.

All these regulations focus on several criteria which are important for disposition. First of all, underlying or concomitant cardiac or non-cardiac disease that may be incompatible with flying has to be excluded by thorough evaluation. The detection of other arrhythmias associated with AF is also important. As some of the regulations allow for flying in case of a single episode with an identifiable cause, triggers or precipitants of single AF episodes have to be identified and the likelihood of recurrence estimated. As AF is a progressive disease [3, 24], it has often been discussed if freedom of recurrence after single episodes is realistic. But in our collecive, this was frequently observed.

In Europe, symptom severity is often characterized using the European Heart Rhythm Association (EHRA) symptom scale [14, 30]. Symptoms (palpitations, fatigue, dizziness, dyspnea, chest pain, and anxiety during AF) are evaluated with regard to how they affect the patient´s daily activity. EHRA 1 would mean no symptoms, EHRA 2a means mild symptoms (normal daily activity not affected), EHRA 2b moderate symptoms (normal daily activity not affected, but patient troubled by symptoms), EHRA 3 means severe symptoms (normal daily activity affected), and EHRA 4 means disabling symptoms (normal daily activity discontinued). Characterization of symptom severity is not only helpful for treatment decisions, but also for aeromedical assessment, e. g. if recurrence prevention should fail in the long term.

Common stroke risk factors are summarized in the clinical risk-factor-based CHA2DS2VASc score [19]. In our exclusively male collective, a score of 0 meant that permanent anticoagulation was not required, with a score of 1 it had to be considered, if ≥ 2 anticoagulation was mandatory. But stroke risk scores have to balance simplicity and practicality against precision. For many risk factors, stroke risk is a continuum rather than an artificial low-, moderate- or high-risk category. It has been shown that in the definition of “vascular disease”, angiographically significant CAD [27] and complex aortic plaque in the descending aorta [31] should also be included as a risk factor. This, however, does not occur in many tables. CHA2DS2VASc score results are dynamic and change over time, regular reevaluations are required.

DOACs have entered EASA regulations in 2019, before only vitamin K antagonists were allowed for anticoagulation. In a meta-analysis DOACs have shown to be non-inferior in the prevention of stroke compared to warfarin, but they were associated with a 10% reduction of all-cause mortality, a non-significant (14%) reduction in major bleeding risk, significant (52%) reduction in intracranial haemorrhage, but 25% increase in gastrointestinal bleeding [25]. In many air forces, anticoagulation is not compatible with military flying because of the increased risk of injuries in combat scenarios and the sometimes impaired medical treatment in missions abroad.

For more than ten years now, catheter ablation has been accepted as a first-line treatment for rhythm control alternative to drug treatment. It is often preferred by aircrew as many side effects of antiarrhythmic drugs are incompatible with flying [10, 11]. After catheter ablation for AF, however, recurrences requiring reablation are not rare and may occur even years after primary procedure. One year of OML or, alternatively, a diagnostic electrophysiological testing after a minimum of two months to ensure ablation success, as recommended by EASA, are therefore not always helpful.

The commercialization of space is moving forward and will increasingly provide opportunities for older and less selected individuals to fly into space. Many of these individuals will be at increased risk of cardiovascular disease or arrhythmia. Knowledge about the pathophysiology and triggers of AF under the conditions of such flights as well as management of the arrhythmia will therefore be of increasing importance. Further studies on AF in environments comprising acceleration forces, possible hypoxia etc., and including older individuals and a higher ratio of females are warranted.

There are some strengths and limitations of our study that have to be mentioned in this manuscript. One of the strengths is the comprehensive analysis of a large number of aircrew over a long duration. In addition to the very long observation time, it is also a strength that there is only one center in the German Armed Forces for aeromedical assessment of military aircrew of all services (Air Force, Army, and Navy). So, the analysis included every aircrew with AF within the last 34 years. On the other hand, it is a limitation that the total number of aircrew examined in the 34-year period is not exactly known. Therefore, the incidence cannot be calculated, but it is certainly much lower than in the general population. Another limitation is that only German data were analyzed. Combining data from other countries’ military flying health data repositories might bolster the sample size. Additionally, this study only provided data on male aircrew, as only males were affected by AF during the observation period. It is not clear if databases of licensing authorities worldwide, e. g. the FAA, have been reviewed to exclude or include females as part of their comparisons and critical thoughts.