Sudden cardiac death in athletesBMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h1218 (Published 18 March 2015) Cite this as: BMJ 2015;350:h1218
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We thank Dr Bapat for his comments regarding sudden cardiac death in athletes. There should be no doubt that immediate bystander CPR and early defibrillation are the two most important first steps which provide the best chance of survival following a cardiac arrest during sports. We agree that factors such as dehydration, hyperthermia and hypoxia are also present and so early intubation and ventilation, as well as fluid and electrolyte replacement, are important subsequent measures following CPR and defibrillation. We support the notion that ongoing research is critical to improve our understanding of the causes, treatment and prevention of sudden cardiac death in athletes.
Competing interests: No competing interests
We read with interest the review by Semsarian et al 1 on the subject of sudden cardiac deaths in athletes. They have stated that increased awareness, and access to automated external defibrillators (AED) and early cardiopulmonary resuscitation (CPR) can help reduce the number of sudden cardiac deaths. However it is not often appreciated that despite early CPR and use of AED, the survival rate is only 29% and drops to 7% in athletes younger than 40 years of age.2 The likely reason for such poor survival is that a majority of younger athletes have undiagnosed genetic cardiovascular abnormalities, particularly cardiomyopathies.2
Are there ways to improve outcome in these otherwise healthy individuals ?
Semsarian et al.1 rightly point out that “underlying condition such as hypertrophy or fibrosis provides a “substrate”, and the exercise provides a trigger such as increased catecholamine levels, acidosis or dehydration”.
Athletes performing at their peak may consume up to 5100 ml oxygen per minute and develop an oxygen debt, which has to be repaid once the exercise is over. Their temperature also rises and may reach to 40 0 C. Athletes may also lose up to 3-5 Kg of fluids in an hour because of sweating. Their skeletal muscle blood vessels are also maximally dilated.3 Essentially, when they collapse, the athletes are likely to be hypermetabolic, hyperthermic, acidotic, hypoxic, and hypovolaemic.
The traditional view is that cardiac arrests in adults are primarily because of a cardiac cause and hence during CPR, circulation produced by chest compressions is paramount. In contrast cardiac arrest in children is most often asphyxial, requiring both ventilation and chest compressions for optimal results.4 We have postulated earlier that because of the pathophysiology described above, cardiac arrest during extreme exertion needs to be treated similarly to that in children and the treatment of hypoxia, hypovolaemia and possible hyperthermia should be considered early during their resuscitation.5 In a study on out of hospital cardiac arrests, Wang et al 6 reported improved outcomes with endotracheal tubes compared to supraglottic airways. It is possible that early endotracheal intubation and ventilation may be important in athletes.
Furthermore, in young athletes with possible cardiomyopathy, use of magnesium may prove to be beneficial. Magnesium is a physiological antagonist of calcium. During cardiac arrest, sustained hypoxia allows calcium to accumulate in cytosol. Magnesium drives calcium back into sarcoplasmic reticulum, reduces mitochondrial overload and competes with calcium for binding with troponin-C. 7 It also increases threshold stimulus required to provoke arrhythmias.8 It is possible that administration of 4-5 g magnesium in these cases could be beneficial. It is unlikely to cause any harm and worth a trial in a situation where the prognosis is otherwise bleak.
Considering all these factors, we believe that if standard ALS and defibrillation are not successful immediately, then early endotracheal intubation and ventilation with oxygen, rapid rehydration with 1-2 litres of Lactated Ringer’s solution and administration of magnesium may improve the likelihood of success.
Present Advanced Life Support (ALS) guidelines do not have any advice on how best to treat athletes having a cardiac arrest. Given the high stakes, it may be worth investing in further research on this subject.
1 Semsarian C, Sweeting J, Ackerman MJ. Sudden cardiac deaths in athletes. BMJ 2015; 350: h1218.
2 Kim JH, Malhotra R, Chiampas G et al. Cardiac arrest during long-distance running races. N Engl J Med 2012; 366: 130-40.
3 Hall JE. Sports Physiology. In: JE Hall (ed.) Guyton and Hall Textbook of Medical Physiology 12th ed. Philadephia: Elsevier Saunders, 2011, pp. 1031-41.
4 Travers A, Rea T, Bobrow B, et al. Part 4: CPR overview: 2010 American Heart Association Guidelines For Cardiovascular Resuscitation and Emergency Cardiovascular Care. Circulation 2010; 122 (Suppl 3): S676-84.
5 Bapat PP, Bapat A, Gupta D. Cardiac arrest in athletes and resuscitation. JICS 2015; 16 (1): 85-6.
6 Wang HE, Szydlo D, Stouffer J. et al. Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest. Resuscitation 2012; 83: 1061-66.
7 Piper HM, Meuter K, Schafer C. Cellular mechanisms of ischaemia-reperfusion injury. Ann Thorac Surg 2003; 75: S644-48.
8 Fawcett WJ, Haxby EJ, Male DA. Magnesium: physiology and pharmacology. Br J Anaesth 1999; 83: 302-20.
Competing interests: No competing interests