This is, to the best of our knowledge, the largest analysis of screening ECGs of initial applicants for aircrew duties and of active aircrew members. The study retrospectively analyzed 8275 resting 12-lead ECGs of initial applicants for aircrew duties and 25,829 ECGs of active-duty aircrew in the German Air Force, Army and Navy, registered between 2007 and 2020. In summary, this analysis shows that only very few applicants show abnormal ECGs disqualifying for aircrew duties. Screening ECGs of active aircrew also revealed very few disqualifying results registered in aircrew of advanced age.
The use of ECG screening is commonplace not only in aviation medicine but also in other high-hazard occupations such as law-enforcement, commercial diving, offshore working, fire fighting, and professional driving. Additionally, it is used for screening of professional athletes [11, 12]. In the occupational setting of aircrew, failing to identify silent cardiac disease may have catastrophic consequences. International recommendations for cardiological screening and ECG interpretation have therefore been published [1]. Criteria for normal and abnormal ECG changes were taken from guidelines and literature on ECG interpretation, but they are often based on the Seattle criteria for athletes [8,9,10]. According to these criteria, some ECG changes can be regarded as normal variants in young people because of their training, whilst others require further examination. The difference found between pilot and non-pilot applicants (Table 3) cannot be fully explained. It may be due to the younger average age, and/or better cardiopulmonary fitness and training condition in pilot applicants.
There are different requirements for ECG screening between civilian licensing authorities. The European Union, for example, requires ECG screening for a class 1 medical certificate (professional pilots), at the initial examination, then every 5 years until age 30, every 2 years until age 40, annually until age 50, and at all revalidation or renewal examinations thereafter. For a class 2 medical certificate (private pilots), it has to be carried out at the initial examination, at the first examination after age 40 and then at the first examination after age 50, and every 2 years thereafter [3]. According to the regulations issued by the Federal Aviation Administration (FAA) in the US, a 12-lead resting ECG is required for first-class medical certification (airline transport pilot) at the first application after reaching the 35th birthday, on an annual basis after reaching the 40th birthday, and on a clinical indication. Without a clinical indication, second-class (commercial pilot) and third-class (private pilot) medical certification does not require a routine ECG [4].
Although most screening ECGs in asymptomatic individuals show normal results or likely normal physiological changes, there is a minority of individuals with ECG changes that are suggestive of genuine cardiac pathology, that may lead to disqualification or restriction [5, 13, 14]. False-positive results from ECG screening, however, should be minimized, as they may lead to unnecessary, time-consuming, and costly downstream, evaluations. Additionally, labelling individuals with an uncertain diagnosis originating from a false-positive ECG finding can lead to psychological effects, as well as possible impact on insurance policies and employment. To avoid misinterpretation of screening ECGs, the published standardized criteria should strictly be followed [1, 9].
In our cohort, the prevalence of abnormal ECG findings requiring further investigation in applicants was comparatively low at 0.21 and 0.25% respectively, in pilots and non-pilot aircrew. Only a fraction of these findings led to disqualification from aircrew duties. However, civilian applicants for a military pilot career, as well as active soldiers applying for aircrew duties, are pre-selected personnel. They must undergo a basic medical examination, which does not include an ECG, but may exclude applicants with a cardiac disease by means of medical history and physical examination. Other studies evaluating the prevalence of abnormal ECG screening results in young and healthy soldiers found a prevalence between 0.6 and 7.0% [14, 15]. In a group of 32,652 young athletes (median age 17 years) undergoing pre-participation ECG screening, the prevalence of abnormal results was 11.8% [16]. Electrocardiographic parameters vary across different ethnicities and in comparison with international norms [15, 17]. It can be assumed that the prevalence of abnormal ECG results in our study was reduced by the basic medical examination prior to the aeromedical assessment in our institution. However, the detected abnormal results, such as the ventricular pre-excitation (delta wave), show that resting ECG screening for this high risk occupation can detect abnormalities that are likely to increase the risk of a sudden incapacitation in flight or other catastrophic events [18].
As in applicants for aircrew duties, screening ECGs of active pilot and non-pilot aircrew also revealed a low percentage of abnormalities that led to disqualification from aircrew duties (0.6%). This may be because aircrew are preselected personnel having passed the initial examination. They also have a distinctive health awareness because of the continuous health education by the local flight surgeon and the GAFCAM, and because of their annual PMEs undertaken throughout their whole career. In the very few cases with disqualifying abnormalities in our cohort the ECG turned out to be a useful tool, which possibly prevented sudden incapacitation in flight. These abnormalities, however, were seen in aircrew of nearly 50 and nearly 60 years of age, respectively.
There is also a risk of false-negative ECG results, for example if cardiac pathology does not cause an ECG abnormality, such as premature coronary artery disease or anomalous coronary anatomy. Other examples that may not be detected on resting 12-lead ECGs include inherited cardiac conditions, that have not developed sufficiently to show an abnormal ECG; ECG abnormalities presenting intermittently or on provocation, such as borderline QT prolongation or Brugada ECG; or ECG abnormalities that are not seen at rest, e.g., rate related bundle branch block. It is generally difficult to verify false-negative ECG results; and with the data in our study, it is impossible. However, there have been a number of autopsy studies in which coronary artery disease was detected in pilots post mortem, which was previously undetected [19, 20].
It is also very difficult to perform a cost benefit analysis that includes false-negative ECG results. However, due to its low sensitivity and specificity, it has been calculated that each air accident prevented by ECG screening costs over 100 million euro [13, 21]. Despite of this poor cost benefit relationship, many authors argue for resting ECG screening because it has been shown to be more sensitive in detecting cardiovascular disease than medical history or physical examination either alone or in combination, and because sudden incapacitation and/or sudden cardiac death of a pilot commanding an aircraft is a devastating event [14].
Based on our assessment, it may be reasonable to perform an ECG at the initial examination at least of pilots, then for all aircrew at the age of 40 years, 45 years, and 50 years, and every 2 years thereafter. As in other studies [14,15,16,17] the proportion of abnormal findings in screening ECGs was higher than in our cohort, significantly more data would be needed to completely abandon initial screening ECGs in young pilot applicants.
The presented study has strengths and some limitations. One of the strengths is the comprehensive analysis of a large sample of resting ECG results over a long period of time. The examinations were performed under constant and standardized conditions. As a 12-lead resting ECG is an obligatory part of every aeromedical assessment for aircrew, every single proband was captured. An additional strength of the study was the measurement of ECG intervals and heart rate leading to the detection of ECG changes, which in our cohort were regarded as normal variants and did not cause disqualification or restriction.
A limitation of this study is the bias that is inherent in the preselection of the applicants by a basic medical examination prior to aeromedical assessment. This preselection, mainly consisting of a medical history and a basic physical examination, may have reduced the prevalence of abnormal results compared to other studies. It may be assumed, however, that individuals with known cardiovascular diseases would probably not apply for a career as a military pilot. This kind of preselection may therefore be typical for aeromedical assessment. One additional important limitation of our study may be the fact that ECG intervals were measured automatically, but the overall ECG interpretation had to be done by the AME. Although all the AMEs were experienced in ECG interpretation, their skills and experience might have been variable. Modern computerized algorithms for ECG assessment might be useful to obtain objective results. The accuracy and plausibility of these automated results, however, should be verified by an experienced physician.
