Excercise physiology has been studied most extensively in the last century.The hemodynamic impact of excercise in various disorders of heart has been well established.
Dyspnea on exertion is the commonest symptom in clinical cardiology practice. It is well-known pulmonary stretch receptors located in pulmonary vasculature is one of the major mechanism of dyspnea.
Excercise increases the cardiac output manyfold.Transporting up to 10-12 litres of blood every minute across the lungs with a narrow pressure head (about 10 mmhg ) is not an easy job . It needs lot of lung discipline .
It is surprising to note, there is little data on excercise induced pulmonary hypertension in the evaluation of patients with unexplained dyspnea.
We know, excercise increases the systemic blood pressure ,we presume it should not raise the PAP (however severe the exertion is 1 )as pulmonary circulation is a high compliant low pressure system.
Is our presumption correct ?
Exercise induced PAH can occur in both health and disease
In patients with preexisting disease
- Stress induced LV dysfunction and resultant raise in LVEDP-PCWP-PAP .This is the most common mechanism in valvular and myocardial disease.
Apparently healthy population
- Excercise induced PAH as a marker for silent CAD .
- Transient Hyperkinetic PAH* (Note :Here PCWP is usually normal )
This is similar to hypertensive response to EST in systemic circulation.Existence of this entity , is controversial, But this may reflect reduced pulmonary vascular reserve or reduced pulmonary nitric oxide secretion.
*The main difference here is the PAH is more often an isolated systolic PAH. While LV dysfunction induced PAH is a combined diastolic and systolic PAH .
How to assess excercise induced PAH ?
It is not an easy job. Invasive catheter derived pressure measurements have been done ,but it is not practical .
The simplest way is to look for the TR /PR jet in echo in both pre and post excercise phase.
Excercise induced PAH is an inadequately studied entity in cardiology , in spite it’s great significance .
This phenomenon is observed in both diseased and normal heart.
The quantum of excercise induced PAH is widely variable depending upon the cardiac status especially LV function and the functional integrity of pulmonary microvasculature .