I have a small pericardial effusion. is this life threatening?

Usually no: However, dependent on the time it took to collect the effusion, even a small effusion can be life-threatening. In other words, if the fluid collects over a short period of time, it can lead to a catastrophic event, but if it takes a long time, the heart copes with it for a while. The best way to tell what effect the fluid has, is to evaluate you with an echocardiogram.