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Post exercise vasovagal syncope: Difference between revisions
Post exercise vasovagal syncope (view source)
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The main point is that PEH is common after moderate-intensity dynamic exercise. In general, this is a benign process and in the majority of individuals PEH is insufficient to cause syncopal symptoms. | The main point is that PEH is common after moderate-intensity dynamic exercise. In general, this is a benign process and in the majority of individuals PEH is insufficient to cause syncopal symptoms. | ||
The magnitude of PEH can be exaggerated in the seated or standing positions (compared to supine) <cite>Kenney</cite><cite>Bjurstedt</cite> and arterial pressure may fall to the level at which pre-syncopal signs or symptoms occur. | The magnitude of PEH can be exaggerated in the seated or standing positions (compared to supine) <cite>Kenney</cite><cite>Halliwill</cite><cite>Halliwill2</cite><cite>Bjurstedt</cite> and arterial pressure may fall to the level at which pre-syncopal signs or symptoms occur. | ||
=== Neurally mediated syncope after exercise === | === Neurally mediated syncope after exercise === | ||
It appears that the underlying mechanism for neurally mediated syncope occurring after the termination of exercise are similar to that of PEH. The sudden removal of the muscle pump activity, decreasing cardiac preload, may be a trigger, along with a rapid return of vagal tone to the heart at the termination of exercise | It appears that the underlying mechanism for neurally mediated syncope occurring after the termination of exercise are similar to that of PEH. The sudden removal of the muscle pump activity, decreasing cardiac preload, may be a trigger, along with a rapid return of vagal tone to the heart at the termination of exercise. <cite>Krediet</cite> | ||
Characteristically, these events occur while the individual is standing motionless during the first 5 to 10 min after exercise <cite>Bjurstedt</cite><cite>Tsutsumi</cite>. Individuals rapidly recover in the supine position. It has been estimated that the incidence rate of neurally mediated syncope after routine treadmill testing may be in the order of 0.3-3 % <cite>Holtzhausen</cite>. However, when treadmill testing is immediately followed by passive head-up tilt testing, this percentage can increase up to 50-70% <cite>Holtzhausen</cite><cite>Sakaguchi</cite>. Neurally mediated syncope after exercise is considered to be a benign occurrence <cite>Krediet</cite>. | Characteristically, these events occur while the individual is standing motionless during the first 5 to 10 min after exercise <cite>Bjurstedt</cite><cite>Tsutsumi</cite>. Individuals rapidly recover in the supine position. It has been estimated that the incidence rate of neurally mediated syncope after routine treadmill testing may be in the order of 0.3-3 % <cite>Holtzhausen</cite>. However, when treadmill testing is immediately followed by passive head-up tilt testing, this percentage can increase up to 50-70% <cite>Holtzhausen</cite><cite>Sakaguchi</cite>. Neurally mediated syncope after exercise is considered to be a benign occurrence <cite>Krediet</cite>. | ||
In a minute minority of cases of syncope during (exertional) exercise the vasovagal reaction is thought to be the underlying pathophysiological mechanism <cite>Krediet</cite>. How the reaction in this circumstance is triggered remains to be elucidated <cite>Krediet</cite><cite>KredietCT</cite>. Nausea prior to such episode is a commonly reported symptom. The following mechanisms may be involved. | In a minute minority of cases of syncope ''during (exertional) exercise'' the vasovagal reaction is thought to be the underlying pathophysiological mechanism <cite>Krediet</cite>. How the reaction in this circumstance is triggered remains to be elucidated <cite>Krediet</cite><cite>KredietCT</cite>. Nausea prior to such episode is a commonly reported symptom. The following mechanisms may be involved. | ||
#Supra-physiological stimulation of ventricular mechanoreceptors in the left ventricle, especially when cardiac filling is decreased at a high heart rate is thought to be a trigger for vasovagal reactions (i.e. the Bezold-Jarisch hypothesis).<cite>Hainsworth</cite> Abrahamsen and Thoren made the observation that such stimulation leads also to reflex gastric dilatation and eventual vomiting in the cat.<cite>Abrahamsson</cite> However many dispute the Bezold-Jarisch hypothesis because evidence for the existence of ventricular mechanoreceptors in man is lacking.<cite>Hainsworth</cite> The newly discovered mechano receptors in the coronaries of the dog could provide an alternative explanation for the results that once were thought to demonstrate the existence of the ventricular mechanoreceptors.<cite>Wright</cite> | #Supra-physiological stimulation of ventricular mechanoreceptors in the left ventricle, especially when cardiac filling is decreased at a high heart rate is thought to be a trigger for vasovagal reactions (i.e. the Bezold-Jarisch hypothesis).<cite>Hainsworth</cite> Abrahamsen and Thoren made the observation that such stimulation leads also to reflex gastric dilatation and eventual vomiting in the cat.<cite>Abrahamsson</cite> However many dispute the Bezold-Jarisch hypothesis because evidence for the existence of ventricular mechanoreceptors in man is lacking.<cite>Hainsworth</cite> The newly discovered mechano receptors in the coronaries of the dog could provide an alternative explanation for the results that once were thought to demonstrate the existence of the ventricular mechanoreceptors.<cite>Wright</cite> | ||
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== References == | == References == | ||
<biblio> | <biblio> | ||
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#Wright pmid=11429656 | #Wright pmid=11429656 | ||
#Holmqvist pmid=3586105 | #Holmqvist pmid=3586105 | ||
<biblio> | </biblio> | ||