Aeromedical cardiology: sudden incapacitation risk

A 55-year-old captain, who flies a commercial aircraft with two pilots, tells the doctor that for a few weeks he has felt chest pressure from time to time. The pain has no clear relation to exertion, sometimes appears at rest and goes away on its own. He was a smoker until age 40, his cholesterol has been called high and his father had a heart attack. He feels well, does not want to stop flying and asks if he can "do a treadmill test and get it sorted out quickly". The scene is fictional and was written for teaching.

This text uses the setting as a scenario for clinical reasoning. The focus is not the passenger with heart disease who is going to travel, but the pilot, who carries the responsibility for everyone on board. The clinical question changes: besides knowing whether he has coronary disease, the doctor needs to estimate the chance that this disease will cause an incapacity in flight. The text is not a summary of any regulator's rules, does not replace the cardiological assessment and does not bring doses, because the sources read do not define them for pilots. If you play the case of the day on NEXO, you will recognize the logic: each clue changes the probability, and the common mistake is to decide too early.

Key points

• Cardiovascular disease is one of the main causes of medical leave for pilots.
• The doctor's question is about the risk of sudden incapacity, and not only about diagnosis.
• The one-in-one-hundred-per-year rule came from reasoning about two-pilot operations.
• The exercise test alone has low predictive value in those with a low chance of disease.
• Anatomical imaging of the coronary arteries helps classify risk more precisely.
• Treating the patient comes before the decision about flying.

Why the pilot's heart is a reasoning scenario

Cardiovascular disease rarely brings down a pilot in flight, but accounts for 50 out of every 100 licenses denied or withdrawn for medical reasons in Western Europe (Nicol et al., 2019).

The same European authors recall that the risk of cardiovascular complications grows with age and includes acute ischemic pain, thromboembolic events and rhythm disturbances, which matter both for distracting and for suddenly incapacitating (Nicol et al., 2019). With pilots flying later in life, the burden of silent disease above age 40 becomes a real issue.

What the scene teaches

The captain brings three kinds of clue: a symptom that is not typical, risk factors that add up and pressure to resolve things quickly. The scenario trains you to separate what changes the probability of disease from what only increases the anxiety of the person deciding. The post on signs, symptoms and history shows how to read the complaint before ordering tests.

The right question: risk of incapacity, not just diagnosis

In ordinary clinical practice, the doubt is whether the pain is coronary and whether it deserves treatment. In aviation medicine, a second question comes in: what is the annual chance of an event that takes the pilot out of action, whether suddenly or subtly. The European authors sum up the order of priorities in one sentence: the patient comes first, the crew member comes later (Nicol et al., 2019).

This has practical consequences. The same finding may not call for intervention under the clinical guideline and still keep the pilot from flying. The authors cite stenosis above 50 out of every 100 of the diameter, which can take someone out of flying even when below the usual threshold for intervention (Nicol et al., 2019). The reverse reasoning also holds: treating the patient well does not, by itself, guarantee a return to flying.

Sudden and subtle incapacity

Sudden incapacitation is the complete loss of the ability to act, as in a heart attack with arrhythmia. The subtle kind is more treacherous: pain, malaise or a drop in performance that distract the pilot without them realizing how compromised they are. Both count, and that is why ischemic pain appears on the list of relevant complications alongside arrhythmia (Nicol and colleagues, 2019).

The one-in-a-hundred-per-year rule

The most cited rule on the subject says that a pilot with a chance of incapacitation below 1 in every 100 per year can keep flying in two-pilot operations. The introductory article in the European series explains the logic in a box: the rule assumes that only about 10 in every 100 of flight time happens in critical phases, such as takeoff and landing, and that the copilot can take over in 99 out of 100 times (Nicol and colleagues, 2019). Multiplying these chances gives a safety target of one fatal event for medical reasons per billion flight hours (Nicol and colleagues, 2019).

The clinical point is that the rule is a model, not a law of nature. The same authors say that, in some contexts, a risk of up to 2 in every 100 per year could be acceptable, and that for single-pilot aircraft the threshold should be lower (Nicol and colleagues, 2019). They also acknowledge that the evidence base in this area is mostly expert consensus.

What changes if the copilot is not there

The whole calculation depends on there being someone ready to take over. When the pilot flies alone, there is no second barrier, and the same individual risk becomes a greater risk for the flight.

The risk matrix

The NATO working group proposed a matrix that crosses the severity of the event with its annual probability, in four bands: probable above 2 percent per year, possible between 1 and 2, improbable between 0.5 and 1 and very improbable below 0.5 (Gray and colleagues, risk, 2019). A third dimension considers the person's role on board, because the same risk weighs differently for someone flying alone, for someone sharing the cockpit and for someone who is not flying (Gray and colleagues, risk, 2019).

Pathophysiology: why small plaque matters too

Most acute coronary syndromes in younger adults arise without warning, and few crew members involved in accidents had symptomatic coronary disease beforehand (Gray and colleagues, screening, 2019). The reason lies in the vulnerable plaque. Mixed or non-calcified plaques, with inflammatory infiltrate, are more likely to rupture and form a thrombus, and they may sit in a vessel whose narrowing, if stable, would cause neither symptoms nor ischemia (Davenport and colleagues, 2019).

Older pathology studies suggest that a stenosis of 30 to 40 in every 100 of the diameter can already precipitate a fatal coronary event (Davenport and colleagues, 2019). That is why aeronautical reasoning is not satisfied with the question "is there ischemia?". It wants to know how much plaque there is, where it is and what type it is.

Exertion, G and medications

The flight environment adds load to the cardiovascular system. In military and aerobatic aviation, acceleration demands high cardiac output and optimal coronary perfusion, and a valve stenosis, even mild, can limit that output (Nicol and colleagues, 2019). The authors note that medications that lower heart rate can hinder the physiological tachycardia needed to tolerate acceleration. For an airline pilot, this load is smaller, but the reasoning about medication effects still applies.

Pretest probability: Bayesian reasoning

Before any test, the doctor estimates the chance of disease from age, sex, type of pain and risk factors. This is the starting point of Bayes, and the NATO group places it at the center of crew screening (Gray and colleagues, screening, 2019). The post on base rate in diagnosis explains why ignoring this starting point leads to predictable errors.

Classic pretest probability models use age, sex and type of pain. The 2021 American guideline on chest pain advises against calling the pain "atypical" and prefers to describe it as cardiac, possibly cardiac or non-cardiac (Gulati et al., 2021). The case commander is a man, 55 years old, with risk factors and a pain that does not fit the classic picture, which places him in the range where pretest probability decides the value of each test.

What the risk factors add

For people without symptoms, the NATO group suggests starting with a risk calculator suited to the population and a resting ECG (Gray et al., screening, 2019). The same text proposes that an estimated risk of 10 in 100 over ten years be the threshold for expanded screening. The resting ECG does not discriminate coronary disease well on its own, but it can reveal left bundle branch block, long QT, Brugada syndrome and cardiomyopathies that raise the risk of sudden death (Gray et al., screening, 2019).

The differential diagnosis

In the commander, the differential has two levels. The first is the common clinical one: whether or not the pain is of coronary origin. The second is the safety one: whether there is any condition capable of incapacitating him, even if it does not explain the pain. The list below follows what the aeronautical cardiology sources describe, and the next section covers the non-cardiac causes.

• Obstructive coronary disease, with flow-limiting stenosis.
• Non-obstructive coronary disease, with plaque that can rupture.
• Rhythm and conduction disorders, which may appear on the resting ECG.
• Cardiomyopathies and hereditary syndromes, such as long QT and Brugada.
• Valvular disease, which weighs more in high-acceleration environments.
• Absence of heart disease, when the investigation is negative.

In aircrew, palpitations, dizziness, presyncope or syncope should raise suspicion of arrhythmia. The European group notes that presyncope and syncope can incapacitate, and that palpitations or dizziness can distract the pilot and harm flight safety. Frequent ventricular extrasystoles, non-sustained ventricular tachycardia and atrial fibrillation are the arrhythmias most seen in this group (Guettler et al., 2019).

In cardiomyopathies, the main aeromedical concerns are arrhythmias and left ventricular dysfunction. Sustained acceleration can worsen the arrhythmia, suddenly reduce cardiac output and lead to G-induced loss of consciousness (D'Arcy et al., 2019).

The non-cardiac causes

The 2021 American guideline notes that more than half of the people seen in the emergency department with chest pain have a non-cardiac cause, and that the life-threatening causes to rule out first are acute coronary syndrome, pulmonary embolism, aortic dissection and esophageal rupture (Gulati et al., 2021). Among the non-ischemic causes the guideline cites are:

• Pericarditis.
• Esophagitis and peptic ulcer.
• Pneumonia and pneumothorax.
• Costochondritis and Tietze syndrome.
• Herpes zoster.

The same guideline describes features that make ischemia less likely: pleuritic pain or pain that changes with position, pain that lasts a few seconds and pain localized to one point. Pain on palpation of the chest or on inspiration greatly reduces the chance of acute coronary syndrome, and relief with nitroglycerin does not serve to make the diagnosis (Gulati et al., 2021). In the commander, these questions enter the history before any test, because a well-characterized non-cardiac cause changes the pretest probability.

Closing too early

The commander's request, "a treadmill test and done", invites ending the reasoning too soon, one of the cognitive errors described by Croskerry, in which the search stops as soon as an acceptable explanation appears (Croskerry, 2003). The text on differential diagnosis with clues shows how to keep hypotheses open, and the post on diagnostic pause helps recognize the moment to stop and review.

Tests: why the stress test alone misleads

The Europeans do not recommend the exercise ECG as the only test in the assessment of aircrew (Nicol et al., 2019). The NATO group explains the reason with Bayes: the specificity of the test is, at best, 60 to 70 in 100, and in a population with a low chance of disease a positive result is more likely to be false than true (Gray et al., screening, 2019).

The US Air Force data cited in the same text illustrate the scale of the problem. To detect stenosis above 70 in every 100, sensitivity was 53 in every 100 with the treadmill, 67 with thallium and 76 with fluoroscopy, and the positive predictive value was only 8, 13 and 18 in every 100 (Gray and colleagues, screening, 2019).

What the SUSPECT study showed

The Dutch SUSPECT study assessed asymptomatic military aircrew aged 40 or older with CT angiography. Clinically relevant coronary disease appeared in 12 in every 100, and disease relevant to flying in 13 in every 100 (Frijters and colleagues, 2025). The exercise ECG was abnormal in 7 people, and only one of them had relevant disease. Some aircrew with a zero calcium score had relevant disease, and the CT proved safe.

Calcium, CT angiography and catheterization

The NATO proposal is a three-step ladder: first a risk calculator and resting ECG, then a calcium score with or without CT angiography for those at increased risk, and finally secondary investigation when something shows up (Gray and colleagues, screening, 2019). Coronary calcium usually accounts for about 20 in every 100 of the total atheroma burden, and so a low score does not rule out non-calcified plaque (Davenport and colleagues, 2019).

The same authors ask that the label of "presumed" coronary disease from a functional test be avoided. To decide about flying, the disease must be confirmed by anatomy, with CT angiography or invasive angiography (Davenport and colleagues, 2019).

From anatomy to risk: how stenosis becomes a decision

The European group published a table that translates the degree of stenosis into annual risk of a major cardiovascular event and into action for flying. The numbers below come from that table, and the action column is an example of the reasoning, not a rule from any country (Davenport and colleagues, 2019).

Anatomical finding	Estimated annual risk of a major event	Reasoning for flying
Stenosis of 70 in every 100 or more, or flow reserve below 0.8 (Davenport, 2019)	Above 3 percent per year (Davenport, 2019)	Removal from flying
Stenosis of 50 to 69 in every 100	Between 1 and 3 percent per year	Flying with restrictions
Stenosis of 30 to 49 in every 100	Between 1 and 3 percent per year	Flying with restrictions
Stenosis of up to 30 in every 100	Between 0.5 and 1 percent per year (Davenport, 2019)	Flying possible, with follow-up
Left main coronary artery with 50 in every 100 or more	High	Removal from flying

The authors add that the sum of stenoses, when it reaches 120 or more, also leads to removal, and that the American and European approaches differ in details (Davenport and colleagues, 2019). They use the risk of a major cardiovascular event as a marker of the risk of sudden incapacitation, because death, infarction and the need for revascularization describe people with lesions capable of causing limiting symptoms or sudden collapse.

When the clinical guideline and flying diverge

The same authors give an example. A single stenosis above 70 in every 100 in an asymptomatic patient can be treated with medication or with revascularization under the clinical guideline, but only the second option would allow a return to flying, to reduce long-term risk (Davenport and colleagues, 2019). That decision requires the patient's consent, and the patient must understand that the choice has an occupational component.

Action: the patient first, flying later

In the captain's case, the first step is to care for him as a patient: investigate the pain under the clinical guideline, treat risk factors and, if there is disease, treat the disease. The decision about flying comes in parallel, with the same information. Temporary removal while the investigation proceeds protects both things.

If the investigation confirms disease with infarction or revascularization, the European group describes a return to flying no earlier than six months, restricted to operation with two pilots in an aircraft without high performance (Davenport and colleagues, after infarction, 2019). The proposed follow-up is annual, with ECG, echocardiogram and Holter.

Medications cited, without doses

The same text mentions aspirin indefinitely, dual antiplatelet therapy for 12 months after angioplasty, statin for everyone and mandatory smoking cessation (Davenport and colleagues, after myocardial infarction, 2019). The sources read do not provide doses, and this text does not either. The introduction to the series adds that anticoagulation keeps many pilots from flying and that some cardiovascular medications have effects that matter in the air (Nicol and colleagues, 2019).

A possible conversation with the captain

• Explain that the pain deserves investigation, regardless of flying.
• Show why a normal treadmill test does not close the case in him.
• Talk about the possibility of anatomical imaging of the coronary arteries.
• State clearly what happens to flying while the case is open.
• Agree on treating risk factors right away.

Reasoning: what remains from the case

The captain does not have a diagnosis yet, and that is the central point. The scenario shows three ideas that work in any specialty. The first is that the value of a test depends on the chance of disease before it. The second is that the decision may depend on a risk the patient does not feel. The third is that the patient's haste does not change the math.

The same reasoning applies to the doctor evaluating the passenger, but with another question: there, the focus is the body's tolerance to the flight environment, not the safety of the person being carried. Separating these questions avoids confusing two scenarios that use the same words.

Common mistakes

Four mistakes appear often in this type of case. The first is ordering an exercise test alone and accepting a normal result as proof of absence of disease. The second is confusing "does not need intervention" with "can fly". The third is using the one-in-a-hundred rule as if it were an exact number, when the authors themselves treat it as a model. The fourth is forgetting that the role on board changes the weight of the same risk.

How NEXO helps train this reasoning

To use the case of the day as training, try three habits. Before the first guess, estimate the chance of the main hypothesis. With each new clue, ask whether it raises or lowers that chance. After the result, note whether you closed the case too early.

Three exercises with cases

Estimate before testing. Write down the probability you would give the main hypothesis before reading the next clue.

Look for the test that changes the decision. Ask which information would change management and which would only provide reassurance.

Separate patient and role. Write down the clinical management and, next to it, what would change if the person had a safety role.

The post about case-based learning in clinical practice shows how cases help cement this habit.

The limits of using the game are described on the NEXO economy page. If you research teaching of clinical reasoning, the page for researchers explains how to get in touch. Professionals who write or review cases find information in curation and in creators, and institutions can learn about the proposal on the partnerships page.

Frequently asked questions

Is cardiovascular disease an important cause of pilots being grounded?

Yes. It accounts for 50 out of every 100 licenses denied or withdrawn for medical reasons in Western Europe (Nicol and colleagues, 2019).

Does the one-in-a-hundred-per-year rule depend on having two pilots?

Yes. The logic of the rule assumes that the co-pilot takes control almost always, and the authors suggest a lower threshold for those who fly alone (Nicol and colleagues, 2019).

Does the pre-test probability change the value of the exercise test?

Yes. In those with a low chance of disease, a positive test is more likely to be false (Gray and colleagues, screening, 2019).

Does CT angiography help classify risk?

Yes. In the SUSPECT study, it found relevant disease in crew members without symptoms and was safe (Frijters and colleagues, 2025).

Can a pilot return to flying after a myocardial infarction?

Yes, in many cases. The European group describes return after at least six months, with restrictions and annual follow-up (Davenport and colleagues, after infarction, 2019).

Final checklist

• I estimated the pre-test probability before ordering tests.
• I considered age, sex, type of pain and risk factors.
• I read the resting ECG also looking for conduction changes and hereditary syndromes.
• I treated the exercise test alone as insufficient to rule out disease.
• I considered the calcium score and CT angiography according to risk.
• I confirmed the anatomy before labeling the disease.
• I separated clinical management from the decision about the flight.
• I took into account function on board and the type of operation.
• I addressed the risk factors from the first consultation.
• I remembered that certification rules vary between countries.

Want to practice reasoning with progressive clues? Play the case of the day.

References

1. Croskerry P. The importance of cognitive errors in diagnosis and strategies to minimize them. Acad Med. 2003. PMID 12915363.
2. D'Arcy JL, Manen O, Davenport ED, et al. Heart muscle disease management in aircrew. Heart. 2019. PMID 30425086.
3. Davenport ED, Gray G, Rienks R, et al. Management of established coronary artery disease in aircrew without myocardial infarction or revascularisation. Heart. 2019. PMID 30425083.
4. Davenport ED, Syburra T, Gray G, et al. Management of established coronary artery disease in aircrew with previous myocardial infarction or revascularisation. Heart. 2019. PMID 30425084.
5. Frijters E, Nathoe H, Grobben R, et al. Prevalence and severity of coronary artery disease in asymptomatic military air crew in the Netherlands: a prospective, cross-sectional study (SUSPECT). BMJ Open. 2025. PMID 40550709.
6. Gray G, Bron D, Davenport ED, et al. Assessing aeromedical risk: a three-dimensional risk matrix approach. Heart. 2019. PMID 30425081.
7. Gray G, Davenport ED, Bron D, et al. The challenge of asymptomatic coronary artery disease in aircrew; detecting plaque before the accident. Heart. 2019. PMID 30425082.
8. Guettler N, Bron D, Manen O, et al. Management of cardiac conduction abnormalities and arrhythmia in aircrew. Heart. 2019. PMID 30425085.
9. Gulati M, Levy PD, Mukherjee D, et al. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain. Circulation. 2021. PMID 34709879.
10. Nicol ED, Rienks R, Gray G, et al. An introduction to aviation cardiology. Heart. 2019. PMID 30425080.