Cardiovascular risk assessment in divers: Toward safer diving.

Similar to aviation, diving is performed in an environment in which acute incapacitation may lead to a fatal outcome. In aeromedicine, a pilot is considered "unfit to fly" when the cardiovascular event risk exceeds one percent per annum, the so-called 1% rule. In diving no formal limits to cardiovascular risk have been established. Cardiovascular risk of divers can be calculated using the modified Canadian Cardiovascular Society (CCS) Risk of Harm formula: risk of harm (RH: cardiovascular fatality rate per year during diving: number × 10-5/divers/year) = time diving (TD: number of dives × 10-4) × sudden cardiac incapacitation (SCI: cardiovascular diver event rate per year (number × 10-5/year). The SCI and thus the RH are strongly dependent on age. Using the CCS criterion for RH, 5 × 10-5 divers/year, and considering an average of 25 dives per year per diver, the calculated maximum acceptable SCI is 2%/year, consistent with current practice for dive medical examinations. If the SCI were to exceed 2%/year, a diver could be considered "unfit to dive," which could particularly benefit older (≥ 50 years) divers, in whom cardiovascular risk factors are often not properly treated. For the prevention of fatal diving accidents due to atherosclerotic cardiovascular disease, a dive medical examination is of limited value for young (≺ 50 years) divers who have no cardiovascular risk factors. Introducing a cardiovascular risk management system for divers may achieve a reduction in fatal diving accidents that result from cardiovascular disease in older divers engaged in both recreational and professional diving.

Unravelling the grey zone: cardiac MRI volume to wall mass ratio to differentiate hypertrophic cardiomyopathy and the athlete's heart.

BACKGROUND: Differentiating physiological left ventricular hypertrophy (LVH) in athletes from pathological hypertrophic cardiomyopathy (HCM) can be challenging. This study assesses the ability of cardiac MRI (CMR) to distinguish between physiological LVH (so-called athlete's heart) and HCM. METHODS: 45 patients with HCM (71% men and 20% athletic) and 734 healthy control participants (60% men and 75% athletic) underwent CMR. Quantitative ventricular parameters were used for multivariate logistic regression with age, gender, sport status and left ventricular (LV) end-diastolic volume (EDV) to ED ventricular wall mass (EDM) ratio as covariates. A second model added the LV EDV : right ventricular (RV) EDV ratio. The performance of the model was subsequently tested. RESULTS: LV EDM was greater in patients with HCM (74 g/m2) compared with healthy athletes/non-athletes (53/41 g/m2), while LV EDV was largest in athletes (114 ml/m2) as compared with non-athletes (94 ml/m2) and patients with HCM (88 ml/m2). The LV EDV : EDM ratio was significantly lower in patients with HCM compared with healthy controls and athletes (1.30/2.39/2.25, p<0.05). The LV EDV : RV EDV ratio was significantly greater in patients with HCM (1.10) than in healthy participants (non-athletes/athletes 0.94/0.93). The regression model resulted in high sensitivity and specificity levels in all and borderline-LVH participants (as defined by septal wall thickness). Corresponding areas under the receiver operator characteristic (ROC) curves were 0.995 (all participants) and 0.992 (borderline-LVH participants only). Adding the LV EDV : RV EDV ratio yielded no additional improvement. CONCLUSIONS: A model incorporating the LV EDV : EDM ratio can help distinguish HCM from physiological hypertrophy in athletes. This also applies to cases with borderline LVH, which present the greatest diagnostic challenge in clinical practice.

Retrospective analysis of challenging cases for medical examiners of diving.

Introduction: Assessing a diver's fitness to dive enhances diving safety, with medical examiners of diving (MED) being entrusted with this responsibility. However, the effectiveness of MED training in preparing physicians for this task remains underexplored. In the Netherlands, where any physician can pursue MED qualification, challenging cases can be presented to a board of experts. Methods: This retrospective analysis included all cases presented to a board of experts in the period 2013-2023. Aside from baseline information, cases were coded using the International Classification of Diseases 11th Revision (ICD-11). Additionally, the type of advice given by the board was also recorded. Results: A total of 291 cases could be included, 62.5% were male divers with a median age of 47 years old (interquartile range 29-55). Circulatory (20.9%), respiratory (16.2%), neurologic (14.4%), psychiatric (9.6%) and endocrine (6.5%) disease comprised more than two-thirds of all presented cases. Problems for the MED included multimorbidity, knowledge of guidelines and interpretation of diagnostic data. Conclusions: These results could be used to improve MED courses or serve as a topic for continuing medical education for MEDs, however, further research into generalisability is required.

SCUBA Diving in Adult Congenital Heart Disease.

Conventionally, scuba diving has been discouraged for adult patients with congenital heart disease (ACHD). This restrictive sports advice is based on expert opinion in the absence of high-quality diving-specific studies. However, as survival and quality of life in congenital heart disease (CHD) patients have dramatically improved in the last decades, a critical appraisal whether such restrictive sports advice is still applicable is warranted. In this review, the cardiovascular effects of diving are described and a framework for the work-up for ACHD patients wishing to engage in scuba diving is provided. In addition, diving recommendations for specific CHD diagnostic groups are proposed.

A new electric method for non-invasive continuous monitoring of stroke volume and ventricular volume-time curves.

BACKGROUND: In this paper a new non-invasive, operator-free, continuous ventricular stroke volume monitoring device (Hemodynamic Cardiac Profiler, HCP) is presented, that measures the average stroke volume (SV) for each period of 20 seconds, as well as ventricular volume-time curves for each cardiac cycle, using a new electric method (Ventricular Field Recognition) with six independent electrode pairs distributed over the frontal thoracic skin. In contrast to existing non-invasive electric methods, our method does not use the algorithms of impedance or bioreactance cardiography. Instead, our method is based on specific 2D spatial patterns on the thoracic skin, representing the distribution, over the thorax, of changes in the applied current field caused by cardiac volume changes during the cardiac cycle. Since total heart volume variation during the cardiac cycle is a poor indicator for ventricular stroke volume, our HCP separates atrial filling effects from ventricular filling effects, and retrieves the volume changes of only the ventricles. METHODS: ex-vivo experiments on a post-mortem human heart have been performed to measure the effects of increasing the blood volume inside the ventricles in isolation, leaving the atrial volume invariant (which can not be done in-vivo). These effects have been measured as a specific 2D pattern of voltage changes on the thoracic skin. Furthermore, a working prototype of the HCP has been developed that uses these ex-vivo results in an algorithm to decompose voltage changes, that were measured in-vivo by the HCP on the thoracic skin of a human volunteer, into an atrial component and a ventricular component, in almost real-time (with a delay of maximally 39 seconds). The HCP prototype has been tested in-vivo on 7 human volunteers, using G-suit inflation and deflation to provoke stroke volume changes, and LVot Doppler as a reference technique. RESULTS: The ex-vivo measurements showed that ventricular filling caused a pattern over the thorax quite distinct from that of atrial filling. The in-vivo tests of the HCP with LVot Doppler resulted in a Pearson's correlation of R = 0.892, and Bland-Altman plotting of SV yielded a mean bias of -1.6 ml and 2SD =14.8 ml. CONCLUSIONS: The results indicate that the HCP was able to track the changes in ventricular stroke volume reliably. Furthermore, the HCP produced ventricular volume-time curves that were consistent with the literature, and may be a diagnostic tool as well.

Sport category is an important determinant of cardiac adaptation: an MRI study.

BACKGROUND: Physiological cardiac adaptation in athletes is influenced by body surface area, gender, age, training intensity and sport type. This study assesses the influence of sport category and provides a physiological reference for sport category and gender. METHODS: Three hundred and eighty-one subjects (mean age 25±5 years, range 18 to 39 years; 61% men) underwent cardiac MRI and ECG: 114 healthy non-athletes (≤3 training h/week) and 267 healthy elite athletes (mean 17±6.6 training h/week). Athletes performed low-dynamic high-static (LD-HS, n=42), high-dynamic low-static (HD-LS, n=144) or high-dynamic high-static sports (HD-HS, n=81). RESULTS: Left ventricular (LV) end-diastolic volume (EDV) index (ml/m(2)) for non-athletes/LD-HS/HD-LS/HD-HS, respectively, was 101/107/122/129 in men and 90/103/106/111 in women. LV end-diastolic mass (EDM) index (g/m(2)) for non-athletes/LD-HS/HD-LS/HD-HS was, respectively, 47/49/57/69 for men and 34/38/42/51 for women. Left or right ventricular EDV ratios were alike in all groups. LV EDV/EDM ratios were similar in non-athletes/LD-HS/HD-LS athletes, and only lower in HD-HS athletes, disproving selective ventricular wall thickening in LD-HS athletes. Multivariate linear regression demonstrated HD-LS and HD-HS sport category coefficients (p<0.01) larger than those of training hours, gender and age (LV EDV/EDM coefficients for sport category LD-HS 6/0.75, HD-LS 16/7, HD-HS 21/17). ECG abnormalities were most frequent in HD-HS athletes and in male subjects. CONCLUSIONS: This study demonstrates a balanced cardiac adaptation with preserved ratios of LV/right ventricular volume (in all sport categories) and LV volume/wall mass (in LD-HS and HD-LS sports). Sport category has a strong impact on cardiac adaptation. HD-HS sports show the largest changes, whereas LD-HS sports show dimensions similar to non-athletes.

Cardiovascular risk in high-hazard occupations: the role of occupational cardiology.

Work is beneficial for health, but many individuals develop cardiovascular disease (CVD) during their working lives. Occupational cardiology is an emerging field that combines traditional cardiology sub-specialisms with prevention and risk management unique to specific employment characteristics and conditions. In some occupational settings incapacitation through CVD has the potential to be catastrophic due to the nature of work and/or the working environment. These are often termed 'hazardous' or 'high-hazard' occupations. Consequently, many organizations that employ individuals in high-hazard roles undertake pre-employment medicals and periodic medical examinations to screen for CVD. The identification of CVD that exceeds predefined employer (or regulatory body) risk thresholds can result in occupational restriction, or disqualification, which may be temporary or permanent. This article will review the evidence related to occupational cardiology for several high-hazard occupations related to aviation and space, diving, high altitude, emergency workers, commercial transportation, and the military. The article will focus on environmental risk, screening, surveillance, and risk management for the prevention of events precipitated by CVD. Occupational cardiology is a challenging field that requires a broad understanding of general cardiology, environmental, and occupational medicine principles. There is a current lack of consensus and contemporary evidence which requires further research. Provision of evidence-based, but individualized, risk stratification and treatment plans is required from specialists that understand the complex interaction between work and the cardiovascular system. There is a current lack of consensus and contemporary evidence in occupational cardiology and further research is required.

Cardiopulmonary assessment prior to returning to high-hazard occupations post-symptomatic COVID-19 infection: a position statement of the Aviation and Occupational Cardiology Task Force of the European Association of Preventive Cardiology.

This article provides an overview of the recommendations of the Aviation and Occupational Cardiology Task Force of the European Association of Preventive Cardiology on returning individuals to work in high-hazard occupations (such as flying, diving, and workplaces that are remote from healthcare facilities) following symptomatic Coronavirus Disease 2019 (COVID-19) infection. This process requires exclusion of significant underlying cardiopulmonary disease and this consensus statement (from experts across the field) outlines the appropriate screening and investigative processes that should be undertaken. The recommended response is based on simple screening in primary healthcare to determine those at risk, followed by first line investigations, including an exercise capacity assessment, to identify the small proportion of individuals who may have circulatory, pulmonary, or mixed disease. These individuals can then receive more advanced, targeted investigations. This statement provides a pragmatic, evidence-based approach for those (in all occupations) to assess employee health and capacity prior to a return to work following severe disease, or while continuing to experience significant post-COVID-19 symptoms (so-called 'long-COVID' or post-COVID-19 syndrome).

Diving with hypertension and antihypertensive drugs.

Hypertension is a common condition, which is highly prevalent amongst scuba divers. As a consequence, a substantial proportion of divers are hypertensive and/or on antihypertensive drugs when diving. In this article, we review available literature on the possible risks of diving in the presence of hypertension and antihypertensive drugs. Guidelines are presented for the diving physician for the selection of divers with hypertension suitable for diving, along with advice on antihypertensive treatment best compatible with scuba diving.

South Pacific Underwater Medicine Society guidelines for cardiovascular risk assessment of divers.

The South Pacific Underwater Medicine Society (SPUMS) diving medical for recreational scuba divers was last reviewed in 2011. From 2011 to 2019, considerable advancements have occurred in cardiovascular risk assessment relevant to divers. The SPUMS 48th (2019) Annual Scientific Meeting theme was cardiovascular risk assessment in diving. The meeting had multiple presentations updating scientific information about assessing cardiovascular risk. These were distilled into a new set of guidelines at the final conference workshop. SPUMS guidelines for medical risk assessment in recreational diving have subsequently been updated and modified including a new Appendix C: Suggested evaluation of the cardiovascular system for divers. The revised evaluation of the cardiovascular system for divers covers the following topics: 1. Background information on the relevance of cardiovascular risk and diving; 2. Defining which divers with cardiovascular problems should not dive, or whom require treatment interventions before further review; 3. Recommended screening procedures (flowchart) for divers aged 45 and over; 4. Assessment of divers with known or symptomatic cardiovascular disease, including guidance on assessing divers with specific diagnoses such as hypertension, atrial fibrillation, cardiac pacemaker, immersion pulmonary oedema, takotsubo cardiomyopathy, hypertrophic cardiomyopathy and persistent (patent) foramen ovale; 5. Additional cardiovascular health questions included in the SPUMS guidelines for medical risk assessment in recreational diving; 6. Updated general cardiovascular medical risk assessment advice; 7. Referencing of relevant literature. The essential elements of this guideline are presented in this paper.

An introduction to aviation cardiology.

The management of cardiovascular disease (CVD) has evolved significantly in the last 20 years; however, the last major publication to address a consensus on the management of CVD in aircrew was published in 1999, following the second European Society of Cardiology conference of aviation cardiology experts. This article outlines an introduction to aviation cardiology and focuses on the broad aviation medicine considerations that are required to manage aircrew appropriately and optimally (both pilots and non-pilot aviation professionals). This and the other articles in this series are born out of a 3 year collaborative working group between international military aviation cardiologists and aviation medicine specialists, many of whom also work with and advise civil aviation authorities, as part of a North Atlantic Treaty Organization (NATO) led initiative to address the occupational ramifications of CVD in aircrew (HFM-251). This article describes the types of aircrew employed in the civil and military aviation profession in the 21st century; the types of aircraft and aviation environment that must be understood when managing aircrew with CVD; the regulatory bodies involved in aircrew licensing and the risk assessment processes that are used in aviation medicine to determine the suitability of aircrew to fly with medical (and specifically cardiovascular) disease; and the ethical, occupational and clinical tensions that exist when managing patients with CVD who are also professional aircrew.

Assessing aeromedical risk: a three-dimensional risk matrix approach.

Early aeromedical risk i was based on aeromedical standards designed to eliminate individuals ii from air operations with any identifiable medical risk, and led to frequent medical disqualification. The concept of considering aeromedical risk as part of the spectrum of risks that could lead to aircraft accidents (including mechanical risks and human factors) was first proposed in the 1980s and led to the development of the 1% rule which defines the maximum acceptable risk for an incapacitating medical event as 1% per year (or 1 in 100 person-years) to align with acceptable overall risk in aviation operations. Risk management has subsequently evolved as a formal discipline, incorporating risk assessment as an integral part of the process. Risk assessment is often visualised as a risk matrix, with the level of risk, urgency or action required defined for each cell, and colour-coded as red, amber or green depending on the overall combination of risk and consequence. This manuscript describes an approach to aeromedical risk management which incorporates risk matrices and how they can be used in aeromedical decision-making, while highlighting some of their shortcomings.

Management of established coronary artery disease in aircrew without myocardial infarction or revascularisation.

This paper is part of a series of expert consensus documents covering all aspects of aviation cardiology. In this manuscript, we focus on the broad aviation medicine considerations that are required to optimally manage aircrew with established coronary artery disease in those without myocardial infarction or revascularisation (both pilots and non-pilot aviation professionals). We present expert consensus opinion and associated recommendations. It is recommended that in aircrew with non-obstructive coronary artery disease or obstructive coronary artery disease not deemed haemodynamically significant, nor meeting the criteria for excessive burden (based on plaque morphology and aggregate stenosis), a return to flying duties may be possible, although with restrictions. It is recommended that aircrew with haemodynamically significant coronary artery disease (defined by a decrease in fractional flow reserve) or a total burden of disease that exceeds an aggregated stenosis of 120% are grounded. With aggressive cardiac risk factor modification and, at a minimum, annual follow-up with routine non-invasive cardiac evaluation, the majority of aircrew with coronary artery disease can safely return to flight duties.

The challenge of asymptomatic coronary artery disease in aircrew; detecting plaque before the accident.

Coronary events remain a major cause of sudden incapacitation, including death, in both the general population and among aviation personnel, and are an ongoing threat to flight safety and operations. The presentation is often unheralded, especially in younger adults, and is often due to rupture of a previously non-obstructive coronary atheromatous plaque. The challenge for aeromedical practitioners is to identify individuals at increased risk for such events. This paper presents the NATO Cardiology Working Group (HFM 251) consensus approach for screening and investigation of aircrew for asymptomatic coronary disease.A three-phased approach to coronary artery disease (CAD) risk assessment is recommended, beginning with initial risk-stratification using a population-appropriate risk calculator and resting ECG. For aircrew identified as being at increased risk, enhanced screening is recommended by means of Coronary Artery Calcium Score alone or combined with a CT coronary angiography investigation. Additional screening may include exercise testing, and vascular ultrasound imaging. Aircrew identified as being at high risk based on enhanced screening require secondary investigations, which may include functional ischaemia, and potentially invasive coronary angiography. Functional stress testing as a stand-alone investigation for significant CAD is not recommended in aircrew. Aircrew identified with coronary disease require further clinical and aeromedical evaluation before being reconsidered for flying status.

Management of established coronary artery disease in aircrew with previous myocardial infarction or revascularisation.

This manuscript focuses on the broad aviation medicine considerations that are required to optimally manage aircrew with established coronary artery disease (CAD) without myocardial infarction (MI) or revascularisation (both pilots and non-pilot aviation professionals). It presents expert consensus opinion and associated recommendations and is part of a series of expert consensus documents covering all aspects of aviation cardiology.Aircrew may present with MI (both ST elevation MI (STEMI) and non-ST elevation MI (NSTEMI)) as the initial presenting symptom of obstructive CAD requiring revascularisation. Management of these individuals should be conducted according to published guidelines, ideally with consultation between the cardiologist, surgeon and aviation medical examiner. Return to restricted flight duties is possible in the majority of aircrew; however, they must have normal cardiac function, acceptable residual disease burden and no residual ischaemia. They must also be treated with aggressive cardiac risk factor modification. Aircrew should be restricted to dual pilot operations in non-high-performance aircraft, with return to flying no sooner than 6 months after the event. At minimum, annual follow-up with routine non-invasive cardiac evaluation is recommended.

Management of cardiac conduction abnormalities and arrhythmia in aircrew.

Cardiovascular diseases i are the most common cause of loss of flying licence globally, and cardiac arrhythmia is the main disqualifier in a substantial proportion of aircrew. Aircrew ii often operate within a demanding physiological environment, that potentially includes exposure to sustained acceleration (usually resulting in a positive gravitational force, from head to feet (+Gz)) in high performance aircraft. Aeromedical assessment is complicated further when trying to discriminate between benign and potentially significant rhythm abnormalities in aircrew, many of whom are young and fit, have a resultant high vagal tone, and among whom underlying cardiac disease has a low prevalence. In cases where a significant underlying aetiology is plausible, extensive investigation is often required and where appropriate should include review by an electrophysiologist. The decision regarding restriction of flying activity will be dependent on several factors including the underlying arrhythmia, associated pathology, risk of incapacitation and/or distraction, the type of aircraft operated, and the specific flight or mission criticality of the role performed by the individual aircrew.

Heart muscle disease management in aircrew.

This manuscript focuses on the broad aviation medicine considerations that are required to optimally manage aircrew with suspected or confirmed heart muscle disease (both pilots and non-pilot aviation professionals). ECG abnormalities on aircrew periodic medical examination or presentation of a family member with a confirmed cardiomyopathy are the most common reason for investigation of heart muscle disease in aircrew. Holter monitoring and imaging, including cardiac MRI is recommended to confirm or exclude the presence of heart muscle disease and, if confirmed, management should be led by a subspecialist. Confirmed heart muscle disease often requires restriction toflying duties due to concerns regarding arrhythmia. Pericarditis and myocarditis usually require temporary restriction and return to flying duties is usually dependent on a lack of recurrent symptoms and acceptable imaging and electrophysiological investigations.

Contemporaneous management of valvular heart disease and aortopathy in aircrew.

Valvular heart disease (VHD) is highly relevant in the aircrew population as it may limit appropriate augmentation of cardiac output in high-performance flying and predispose to arrhythmia. Aircrew with VHD require careful long-term follow-up to ensure that they can fly if it is safe and appropriate for them to do so. Anything greater than mild stenotic valve disease and/or moderate or greater regurgitation is usually associated with flight restrictions. Associated features of arrhythmia, systolic dysfunction, thromboembolism and chamber dilatation indicate additional risk and will usually require more stringent restrictions. The use of appropriate cardiac imaging, along with routine ambulatory cardiac monitoring, is mandatory in aircrew with VHD.Aortopathy in aircrew may be found in isolation or, more commonly, associated with bicuspid aortic valve disease. Progression rates are unpredictable, but as the diameter of the vessel increases, the associated risk of dissection also increases. Restrictions on aircrew duties, particularly in the context of high-performance or solo flying, are usually required in those with progressive dilation of the aorta.