Update on bedside ultrasound diagnosis of pericardial effusion.

Pericardial effusion (PE) is the presence of an excess of fluid in the pericardial cavity. PE symptoms depend from the rate of fluid accumulation, ranging from mild dyspnea on exertion to shock due to cardiac tamponade. Echocardiography is usually the primary diagnostic tool when PE is suspected, as it is accurate, non-invasive, widely available, and feasible also with pocket size devices. Studies have shown a high degree of sensitivity and specificity in the detection of PE using focused cardiac ultrasound (FOCUS), which can be performed also by non-cardiologist in emergency setting or at bedside. A PE is visualized as an echo-free space between the heart and the parietal layer of the pericardium. A semi-quantification of the PE may be obtained measuring the distance between the two pericardial layers. Once PE diagnosis has been made, characterization of fluid and search for signs of possible cardiac tamponade have to be performed. While unechogenic space is usually associated with serous fluid, hemorrhagic, and purulent effusions may be suspected in the presence of corpuscolated/echogenic fluid. Echocardiography may identify cardiac tamponade before it is clinically evident, and can guide pericardiocentesis. B-mode echocardiographic signs of cardiac tamponade include cardiac chambers collapse (with right chambers collapse occurring at earlier stages), opposite changes in right and left cardiac chamber filling during respiratory cycle, inferior vena cava and hepatic vein plethora. Doppler analysis of tricuspidalic and mitral flow velocities are used for a more detailed analysis of ventricular interdependence, even though more advanced operator expertise is required.