Echocardiographic Evaluation of Pericardial Disease - Casecag.com

Avery EG/Pericardial Disease Page 4 of 10Figure 3. M-mode image (thearrows highlight a thickenedpericardium).Avery EG & Shernan SK.Comprehensive Textbook ofPerioperative TransesophagealEchocardiography 2ed. Chapter39. 2010Pericardial effusion is a collection of fluid within the pericardial sac that can either be diffusely distributed within thepericardium or localized. Depending on patient position and the amount of volume contained in the effusion different patternsof fluid distribution can be seen assuming that the pericardial space does not contain fibrous adhesions, or a mass that mayredirect accumulating fluid. Echocardiographically, a pericardial effusion appears as an echolucent signal immediatelyadjacent to the epicardium. General guidelines on pericardial effusion size and fluid distribution patterns are presented inTable 3 2 . Caution is warranted when diagnosing a pericardial effusion to rule out the presence of epicardial fat which canappear similar to a pericardial fluid collection at first glance. Close observation of epicardial fat demonstrates a weakechogenic signal compared to the more echolucent signal of a pericardial fluid collection.Table 3. Pericardial Effusion CharacteristicsSeverity Width by Echo Volume (mL) Localization RegionSmall < 10 mm < 100 Behind posterior LV wallModerate 10-15 mm 100-150 Expand laterally and apicallyLarge > 15 mm > 500 Evenly distributed around the heartThe clinical significance of a pericardial effusion relates to the amount of fluid present and the time course over which itaccumulates. Large, chronic effusions are frequently associated with excessive antero-posterior heart motion as well ascounterclockwise rotation in the horizontal plane. Effusions can lead to cardiac translation within the pericardial space that cancreate the ECG finding termed electrical alternans (Figure 4) 1 . Electrical alternans is the regular occurrence of alternatingheights of the QRS complex that may also involve the P, T, U waves and ST segments; this finding is not specific to pericardialeffusions 10 .Figure 4 1 . Electricalalternans on the ECG of apatient with a pericardialeffusion.Avery EG & Shernan SK.Comprehensive Textbook ofPerioperativeTransesophagealEchocardiography 2ed.Chapter 39. 2010Pericardial effusions are highly common in cardiac surgical patients (85%) and generally peak by the 10 th postoperative day 1 .The relevance of a pericardial effusion relates to the volume of fluid that accumulates and the chronicity with which itaccumulates (Figure 5a) 2 . Over time the pressure in the pericardial space will increase as the effusion grows in volume andeventually intrapericardial pressure will rise above the cardiac chamber pressures. When intrapericardial pressure increases tothe point that cardiac chamber filling is compromised the patient is considered to have developed tamponade physiologyresulting in the clinical finding of pericardial tamponade. Additionally, when the amount of accumulating fluid causes amore extreme increase in pericardial pressure (i.e. the pressure-volume relationship has reached the steep point on the curvewhich relates these two physiologic variables (Figure 5b)) ventricular interdependence will be manifest 5,11 . Note the adaptivenature of the pericardium that is observed with slowly accumulating effusions in Figure 5b 5 . The mesothelial cells thatcomprise the pericardium have the ability to hypertrophy and over time accommodate greater amounts of pericardial fluidprovided that the fluid is slowly accumulating. With ventricular interdependence as the right ventricle fills the interventricular