valsava maneuver to treat paroxysmal supraventricular tachycardia - USMLE Forums
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Old 08-13-2011
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Default valsava maneuver to treat paroxysmal supraventricular tachycardia

Hi all:

Please help me explain why valsava maneuver can be used in the treatment of paroxysmal supraventricular tachycardia?

valsava maneuver decreases preload, so this leads to increased heart rate, right?

Thank you!
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Old 08-13-2011
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Default PSVT and Vagal Maneuvers

In patients with paroxysmal supraventricular tachycardia, vagal stimulation can end tachycardia by slowing down conduction through AV node and can potentially interrupt the reentrant circuit.
Valsalva is the first vagal maneuver to try in stable conscient patients, it works by increasing intra-thoracic pressure and affecting baro-receptors within the arch of the aorta, thus, stimulating the vagus to slow down the AV node through parasympathetic activity.
Valsalva maneuver affects preload, but this effect has nothing to do with cardiac electrical conduction.
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Old 08-13-2011
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Default

Thank you for your reply:

But there is one thing i am confused:

Since valsava affects preload, if we decrease preload, we are supposed to see increased reflex heart rate
and since like what you said: valsava acts on the aortic arch to increase parasympathetic rate, if we decrease preload, there is less blood flow to the aortic arch, how can we increase aortic arch vagal parasympathetic firing rate in order to decrease heart rate via prolonging AV node refractory period?

Thank you for your patience!










QUOTE=NGaleas;60643]In patients with paroxysmal supraventricular tachycardia, vagal stimulation can end tachycardia by slowing down conduction through AV node and can potentially interrupt the reentrant circuit.
Valsalva is the first vagal maneuver to try in stable conscient patients, it works by increasing intra-thoracic pressure and affecting baro-receptors within the arch of the aorta, thus, stimulating the vagus to slow down the AV node through parasympathetic activity.
Valsalva maneuver affects preload, but this effect has nothing to do with cardiac electrical conduction.[/QUOTE]
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Old 08-13-2011
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Default Intrathoracic Pressure

I understand your confusion. In the early states of valsalva maneuver, there is a decrease in preload, which as you have written, increases heart rate due to a reflex sympathetic response (preload decreases because increase intrathoracic pressure limits IVC blood to drain into the right atrium.

BUT, in late stages of valsalva maneuver, this same increase in intrathoracic pressure will affect Baroreceptors in the arch of the aorta, which as its name imply are affected by pressure, not by the blood itself. This effect predominates.

This explains why carotid massage also decreases blood pressure, the pressure is exerted by the outside as we massage the carotid in the neck, and baroreceptors sense this pressure and also sen information through IX and X nerve to reduce blood pressure and decrease heart rate (also used for paroxysmal supraventricular tachycardia)
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