What are the mechanisms of “Pulmonary Arterial Hypertension” in Dilated cardiomyopathy ?
Posted Feb 18 2012 10:13am
Pulmonary arterial hypertension (PAH ) is an uncommon manifestation of dilated cardiomyopathy .While pulmonary venous hypertension of some degree is expected in most patients with DCM, it is rare for these patients to go for severe arterial hypertension.
The reason for this may be the natural history of DCM do not allow these patients to live that longer to manifest severe PAH. Still , we encounter this problem atleast in tertiary hospitals. Presence of moderate to severe PAH (> 50mm peak PAP) is a sinister sign in DCM. They not only do badly , they also make the transplant outcome dismal .
What causes this severe PAH in DCM ? The following observations are made in our institute .
Now we know , isolated systolic dysfunction is rarely associated with PAH .It is the presence of LV diastolic dysfunction (Often restrictive ) that raises the pulmonary pressures. PAH of DCM is rarely progressive.
One important suggestion is the DCMs which are associated with severe PAH may indeed represent late stages of RCM , when the LV begin to dilate.
Associated mitral regurgitation contributes to PAH
Atrial fibrillation has a significant impact on elevating pulmonary venous and arterial pressures in DCM.
Hypoxic PAH can occur in any medical situation in susceptible population . DCM is no exception
For some reason idiopathic DCM is more often result in PAH than ischemic DCM . (Is that possibel , some form of idiopathic PAH and DCM are etiologically related ?)
Further , the positive inotropic agents when liberally used will worsen the diastolic properties of LV.
Finally involvement of right ventricle in the cardiomyopathy process can have an ameliorating effect on PAH. A good RV function is essential to lift the PA systolic pressure. If RV failure is causing a low PAP , do not be happy .It simply means RV is going to say good bye . . . for the final time !
How to manage PAH in DCM ?
There is no specific management strategy .
We do not know yet whether Sildenafil , Bosentan, and Epoprostenol have any role in this form of PAH. These are all basically vasodilators. It’s use in DCM is vested with a risk of catastrophic hypotension . Of course , we do have a role for balanced vasodilators in cardiac failure .(As most of these patients would be already on adequate ACEI )
Presence of PAH should be considered as an independent indication for anticoagulants as in situ pulmonary thrombus is common.
The effect of cardiac resynchronisation therapy in reducing the PAH of DCM is not convincing.
PAH in DCM is an unwelcome development. It makes the situation tough . The mechanisms are diverse .Understanding the mechanism would help us deal this problem better . Conventional anti failure treatment may help ,but it is wiser to try reserve drugs.