It is well known that an adequate and immediate response is key to improve survival rates in sudden cardiac arrest (SCA) in sports. Improving our understanding on the causes, mechanisms and characteristics of these uncommon but tragic events is also considered essential to improve outcomes. In this novel observational study the authors analyzed the intensity of the activity prior to the SCA, the position, facial features, presence of seizure-like limb movements and agonal respirations of the victims; and the timing (≤1 min=quick, >1 min=delayed) and specifics of the emergency intervention in the video recordings of 35 cases of SCA in sports.
Twenty six of the 35 videos corresponded to professional sports, 19 to football, and 29 to athletes of < 35 years of age. Twenty one out of the 35 victims had a positive outcome, surviving after the SCA.
Among the 28 videos where it was possible to assess the physical activity prior to the event, the intensity was low (standing, walking or slow jogging) in 19 events, moderate (jogging-running) in 6 and high (sprinting, jumping, start and stop) in 3. In 9 of the 19 low intensity cases, the SCA was preceded by high intensity activity more than 5 seconds before collapse.
Resuscitation was carried out in 20 of the 26 cases in which it was possible to observe if any Cardiopulmonary resuscitation (CPR) manoeuvres were provided: 8 with CPR alone, 10 with CPR + defibrillation, 1 with a cardiac thump and 1 more with a shock from an implantable cardioverter defibrillator. Survival was higher when intervention occurred within 1 min of collapse (12/13), compared to those who received delayed (3/5) or no intervention (1/6). Associated signs of SCA were observed in 23 (66%) cases: agonal respirations in 12 and seizure-like movements in 7; but went often unrecognized and without early intervention within 1 min of collapse (15/23).
The main finding of this study is that, as expected, those who receive a quick resuscitation within 1 minute of collapse have a higher survival rate. This reinforces all secondary prevention strategies addressed to improve CPR training to all those involved in any athletic activity and automated external defibrillator (AED) availability in sports facilities.
The conclusions also highlight an essential aspect to avoid delaying a quick intervention: adequate and prompt recognition of all associated signs of SCA. This should be always included in any CPR training activities and educational resources.
Trying to find out the relationship between the intensity of the activity and the SCA is one of the strengths of this study. As according to the methodology, most cases of SCA (19/28) occurred in a low intensity phase (9/19 preceded by vigorous activity more than 5 seconds before collapse), the authors question the role of adrenergic stimuli and hypothesize that parasympathetic stimuli in that early phase of recovery may play a significant role in the pathophysiological mechanisms of SCA. This hypothesis remains to be confirmed by further research, but it might be challenging, especially in stop and go sports, due to the overlap between the autonomic nervous stimulation and the constant changes in exercise intensity.
From my personal point of view, the 5 seconds cut-off limit may be too short in high intensity intermittent sports like football (19/35), basketball (4/35) and ice hockey (3/35), in which average heart rates are around 85% of maximum heart rate. Considering this, we might think that a significant proportion of the 19 cases included in the low intensity category, at least the 9 preceded by vigorous activity, could be more related with the adrenergic surge inherent to high intensity exercise.
Until further research elucidates the relationship between exercise intensity, the autonomic nervous stimulation and SCA, our efforts should focus on increasing survival rates by improving the quality and quantity of CPR trained individuals and the number of available AEDs.
Note: The content of this article reflects the personal opinion of the author and is not necessarily the official position of the European Society of Cardiology.