Bedside echocardiogram
Echocardiography is a non-invasive test that can be performed quickly to confirm the diagnosis. Whilst routinely four views are obtained (parasternal long and short axis; four chamber and subcostal), in an emergency the subcostal view usually confirms the diagnosis. The main findings are fluid in the pericardial sac and collapse of the chambers. Each chamber will collapse when pericardial pressure is above its internal pressure.
This will initially occur during each respective chamber’s phase of relaxation in the cardiac cycle and with respiration. Right atrial collapse is often observed in early systole. Left atrial collapse also occurs in systole but rarely in isolation. Right ventricle collapse occurs in diastole initially. Left ventricular collapse is the last to be observed. As tamponade worsens, collapse of each chamber will be noted throughout longer phases of the cardiac cycle and is associated with increased severity [2][3].
Other important findings are exaggerated interventricular dependence during the respiration cycle; collapsibility of the IVC and “septal bounce”.
Additional investigations and findings/their justification are listed in the table below:
Myocardial infarction with ventricular rupture and trauma are the most common causes for unstable cardiac tamponade whereby only small volumes of blood are required to compress the heart. Other causes include uraemia, viral such as HIV, malignancy, and autoimmune conditions so a broad set of investigations are required. These conditions tend to require larger volumes of fluid due to a slower accumulation of fluid in the pericardium [2].
