Post-exercise Syncope

Syncope after exercise is often neurally mediated, i.e. post-exercise vasovagal syncope. This condition is typically diagnosed in young fit, furthermore healthy young patients. Foremost, the diagnostic workup of all patients presenting with exercise-related syncope is aimed at excluding dangerous cardiac conditions and includes echocardiography and exercise testing [1]. Risk factors for a cardial problem are fainting while sitting or supine and suddenly fainting during exercise without presyncope.
Characteristically, syncope may occur while the individual is standing motionless during the first five to ten minutes after exercise [2]. Especially athletes in the (ultra) endurance sports are at risk for post exercise vasovagal syncope e.g. after marathon swimming [3] or marathon running [4][5][6]. Vasovagal syncope after routine treadmill testing is rare (estimated 0,2% [7]). However, when treadmill testing is immediately followed by passive head-up tilt testing, this percentage can increase up to 50-70% [2]. Vasovagal syncope after exercise is considered to be a benign occurrence [1].

Muscle pump

During exercise, rhythmically contracting skeletal muscles in the lower part of the body reduce the degree of venous pooling by squeezing veins, thereby increasing the venous return of blood to the heart. This phenomenon is known as the ‘muscle pump. The sudden removal of the muscle pump after stopping exercise decreases cardiac preload which, together with a rapid return of vagal tone, may promote vasovagal syncope.

References

1. Krediet CT, Wilde AA, Wieling W, and Halliwill JR. Exercise related syncope, when it's not the heart. Clin Auton Res. 2004 Oct;14 Suppl 1:25-36. DOI:10.1007/s10286-004-1005-1 |
2. Bjurstedt H, Rosenhamer G, Balldin U, and Katkov V. Orthostatic reactions during recovery from exhaustive exercise of short duration. Acta Physiol Scand. 1983 Sep;119(1):25-31. DOI:10.1111/j.1748-1716.1983.tb07301.x |
3. Finlay JB, Hartman AF, and Weir RC. Post-swim orthostatic intolerance in a marathon swimmer. Med Sci Sports Exerc. 1995 Sep;27(9):1231-7.
4. Grady GF, Rodman M, and Larsen LH. Hepatitis B antibody in conventional gamma-globulin. J Infect Dis. 1975 Oct;132(4):474-7. DOI:10.1093/infdis/132.4.474 |
5. Holtzhausen LM and Noakes TD. The prevalence and significance of post-exercise (postural) hypotension in ultramarathon runners. Med Sci Sports Exerc. 1995 Dec;27(12):1595-601.
6. Holtzhausen LM and Noakes TD. Collapsed ultraendurance athlete: proposed mechanisms and an approach to management. Clin J Sport Med. 1997 Oct;7(4):292-301.
7. Done AK, Yaffe SJ, and Clayton JM. Aspirin dosage for infants and children. J Pediatr. 1979 Oct;95(4):617-25. DOI:10.1016/s0022-3476(79)80783-0 |