Since LA pressure tends to be higher than RA pressure, LA collapse can withstand a higher pericardial pressure and collapses later than RA. For this reason, LA collapse is a less sensitive but more specific sign for tamponade than RA collapse. In patients with pre-existing pulmonary hypertension (with or without RV hypertrophy), it may be possible for LA collapse to occur in the absence of RA or RV collapse (figure below on left). Rarely, LA or LV collapse can also occur in isolation from regional tamponade after trauma or cardiac surgery (figure below on right).