Estimated PASP=RVSP+RAP…..What now??
So you have worked out your estimated right ventricular systolic pressure (RVSP), added your estimated right atrial pressure (RAP), and now have an estimated pulmonary arterial systolic pressure. In fact, you are feeling pretty chuffed as you have made your first diagnosis of pulmonary hypertension. So what now?
Pulmonary hypertension on an echo can be a perplexing finding. You first have to decide – is this significant? And what are the consequences? Finally what is the underlying cause?
Answering these questions can be very difficult for even experienced scanners. The YMJE 2010 Lawrence G Rudski MD ASE 2010 guidelines suggest a TR velocity >2.9m or a PASP>40mmHg is significant elevated. However, these numbers are derived from stable outpatients, and their applicability to critically ill patients undergoing mechanical ventilation is not clear.
The consequences of pulmonary hypertension effect predominantly the right side of the heart, but may also lead to left sided heart failure if severe. A key feature of how the right heart responds is the duration – the right ventricle is poor at coping with sudden changes in afterload, and decompensation is common after of acute severe pulmonary hypertension. The wall remains thin (<5mm in subcostal view), and pressures are rarely >70mmHg. A more gradual onset is often accompanied by RV hypertrophy (RV>5mm), PASP may be >70mmHg, and there is relative preservation of function until quite late.
Identifying the cause of the pulmonary hypertension often presents a challenge, but the good news is your echo is uniquely placed to answer the question. Working sequentially backwards, the causes include LVF, mitral valve disease, pulmonary venous or pulmonary arterial hypertension. A more useful way clinically is to divide the causes into acute and chronic. Acute causes include acute pulmonary embolus, acute RV infarction, acute heart failure. Chronic causes include pulmonary arterial hypertension, left to right shunts, LVF and mitral valve disease.
The following example was recorded in a lady who presented with dysponoea over one week. It shows evidence of severe pulmonary hypertension (RVSP 70). Her images revealed severely dilated RV, with severely reduced function. There was thickening of the right ventricle, and dilatation of the RA, consistent with chronic pulmonary hypertension. There was also a small pericardial effusion, which carries a poor prognosis in pulmonary hypertension.
She was referred to a pulmonary hypertension specialist, and commenced on sildenofil and bosentan.