I am far from an expert on this subject matter, but the past research I've done shows different groups for Pulmonary Hypertension:
1) PAH - Pulmonary Arterial Hypertension - This group is more idiopathic as the cause or sometimes genetic or drug induced. There are drugs that can help folks in this group.
2) Group 2 - PH due to left sided heart disease. This is the most common reason for PH. Left sided heart disease can be caused by numerous reasons, but this can lead to PH due to higher pressures and fluid back up in the lungs. This in turn causes the right side of the heart to work harder and ultimately can lead to right sided heart failure.
3) Group 3 - PH due to lung disease - COPD, Emphysema, Interstitial restrictive lung disease, sleep apnea, etc. can eventually lead to a PH condition.
4) Group 4 - PH due to Pulmonary Embolism - This is the only group beside group 1 that has some level of treatment. Remove the embolism and PH should improve.
Most times addressing root cause should help with PH. For example, if there's a bad mitral valve, fixing that should help with many things including PH..
I also agree that so many things are interconnected. For example sleep apnea can be a direct cause of both AFib and PH. AFib can cause (and vice versa) Atrial Myopathy, which can then influence diastolic dysfunction and eventually lead to some level of PH, etc..
The pressures you've listed are mild and cannot be confirmed without a right heart catheter procedure. There is both over and under estimations of PH on Echo's. One pulmonologist I heard on Dr Radio stated they wouldn't even consider a right heart catheter procedure unless the Echo was showing well into the 40's mm/hg and the person was symptomatic. The hallmark symptom of PH is usually shortness of breath initially on exertion. People with moderate or severe PH have pressure numbers more than twice what yours are and usually have failed lung function tests, etc.
Not sure if the ASD (hole between the two atria) can contribute to pressures and PH. Have you had a sleep apnea test done? That can be a direct cause.