Sudden Cardiac Arrest Related to Sport in Young and Value of the Genetic Assessment: a French Prospective Register

Background:

The beneficial effects of moderate physical activity on health are well-established. However, it is also well-proven that intense sports participation increases the risk of cardiovascular events by 2.4 to 4.5 times before the age of 35 in individuals with known or unknown heart conditions. Sudden cardiac arrest (SCA), sometimes leading to sudden cardiac death (SCD), is the most dramatic event linked to sports.

Before the age of 35, sports-related SCA/SCD is rare, occurring in 0.7 to 2.7 per 100,000 athletes, which amounts to approximately 80 cases per year according to two French prospective studies. Despite its rarity, these events are often traumatic and highly publicized, presenting a significant public health and safety concern. Non-traumatic sports-related SCA/SCD is primarily of cardiovascular origin, irrespective of the level of sports participation. In most cases, SCA results from ventricular arrhythmia caused by known or undiagnosed arrhythmogenic cardiovascular disease, which varies by the victim's age. After the age of 35, atheromatous coronary artery disease accounts for 80-85% of cases. However, before the age of 35, a wider range of etiologies are observed. Arrhythmogenic genetic heart diseases-structural (e.g., arrhythmogenic right ventricular cardiomyopathy and hypertrophic cardiomyopathy) or non-structural (e.g., channelopathies)-are the most frequent causes. Congenital abnormalities, particularly anomalous connection of coronary artery, represent the second most common cause. Acquired heart diseases, such as fibrous scars (mainly post-myocarditis) and atheromatous coronary lesions, are less frequently involved. In this younger population, classical autopsy often fails to determine the cause in more than 40% of cases, leading to the term "sudden arrhythmic syndrome".

Few prospective studies have combined classical autopsy with systematic genetic analysis to identify the cause of SCA/SCD in the general young population, with no specific link to sports. One Australian study demonstrated the value of genetic testing, identifying a "clinically relevant" cardiac genetic variant for sudden death in 27% of cases. Moreover, the same pathology was identified in 13% of relatives of the victims who underwent clinical and genetic screening. Another small Swedish study (n=15), focusing specifically on channelopathies in cases of negative autopsies, revealed the disease in 40% of victims' families through genetic analysis.

Additionally, the role of acute or chronic toxic substance intake has been suggested, albeit without formal proof, as a factor promoting sports-related SCA/SCD. Toxicological screening is thus recommended as part of the etiological assessment. Including toxicological analysis alongside other etiological evaluations could help clarify the impact of illicit substances on sports-related SCA/SCD.

Justifications for the Study:

No prospective study has systematically combined the recommended hospital assessment in cases of successful resuscitation or the recommended medical autopsy in the event of death with global genetic and toxicological analyses in victims of sports-related SCA/SCD.

This combined approach is justified for several reasons. First, it would enhance our understanding of the etiologies of these events. Notably, so-called idiopathic left ventricular hypertrophy is found in more than 10% of sports-related SCD cases following classical autopsies. Further genetic exploration could help determine whether these anatomical forms are pathological. Additionally, many arrhythmic cardiac diseases are associated with an elevated risk of sports-related SCA/SCD. While arrhythmogenic right ventricular cardiomyopathy is well-documented, other forms of disease are characterized by areas of fibrosis or fatty infiltration in the myocardium, often due to genetic mutations affecting intercellular desmosomes. Comprehensive genetic testing, including whole exome sequencing, could clarify the contribution of various arrhythmogenic heart diseases to unexplained sports-related SCA/SCD.

Improving this knowledge will benefit ongoing discussions about enhancing the content and effectiveness of pre-participation screening for athletes. Moreover, identifying the cause of SCA/SCD is critical for the victims and their families. Understanding the cause may help families come to terms with the event and assist in preventing recurrence for successfully resuscitated individuals. Furthermore, since most hereditary heart diseases follow an autosomal dominant inheritance pattern, each first-degree relative has a 50% chance of carrying the same genetic mutation. Predictive testing, clinical assessment, and, if necessary, preventive treatment can be offered to these family members to reduce the risk of arrhythmic events.

Statistical Analysis:

Data analyses will be performed using specialized software, with a significance threshold set at 5%. Hypotheses will be formulated bilaterally.

A descriptive analysis of the collected population data will be conducted. Qualitative variables will be presented as numbers and percentages, while quantitative variables will be described using the mean, standard deviation, median, interquartile range, minimum, and maximum values.

For the primary analysis of the main outcome, the cause of sports-related SCA/SCD will be described in terms of numbers and percentages, along with the corresponding 95% confidence intervals.

For the secondary analyses, the judgment criteria, both overall and by vital status (survived or deceased), will be described in numbers and percentages, with 95% confidence intervals.