Posts Tagged ‘exertional dyspnea in tof’

It is a combination of biochemical and  pulmonary receptor mediated dyspnea.

1. Hypoxia gets accentuated on exertion and it stimulates  chemoreceptors  located  in brainstem  as well as  aortic arch and its branches.

2. Equally important is the ventilation /perfusion mismatch that occur during exertion as the pulmonary blood flow significantly drops while the lung will continue with normal ventilation .This  increases the  Vp/Vq   (> 1) and  worsen the hypoxia  and   can independently trigger the sensation of dyspnea due to stretching of airway mechanoreceptors..

(It is  prudent to recall ,the later mechanism (Vp/Vq mismatch ) is  explicitly involved in  isolated  valvular pulmonary stenosis .Here , there is no admixture  mediated hypoxia , still the patient experience significant dyspnea  due  to meager  reduction  in pulmonary blood flow.)

3. Further ,  there are some morphological changes that occur in pulmonary vasculature in patients with TOF.This is due to chronic hypoxia as well as  “chronic low flow” mediated vascular reactivity. Micro vascular dysfunction in the alveolar capillary bed  is  possible in TOF. There  is  some evidence to suggest pulmonary gaseous exchange is impaired when compared to normal lungs.This can also contribute to the dyspnea in TOF.


The following article excellently describes the pulmonary dysfunction  that occurs in patients with TOF .It is prudent to note  ,the abnormal  lung function fails to get corrected even after total surgical correction in many.


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