Why does the right ventricle collapse under pericardial effusion?

From the Guidelines

The right ventricle collapses under pericardial effusion due to its thinner wall structure and lower pressure system compared to the left ventricle, making it more vulnerable to external compression from the accumulating fluid in the pericardial space. When fluid accumulates in the pericardial space during pericardial effusion, it creates increased pressure within the confined pericardial sac, as described in the 2015 ESC guidelines for the diagnosis and management of pericardial diseases 1. This elevated pressure compresses the heart chambers, with the right ventricle being most vulnerable to collapse because it normally operates at lower pressures (15-30 mmHg systolic) than the left ventricle (100-140 mmHg systolic) 1.

Some key points to consider:

• The right ventricle has a thinner muscular wall (3-5 mm) compared to the left ventricle (13-15 mm), making it less resistant to external compression 1.
• The crescent shape of the right ventricle also provides less structural integrity against external pressure compared to the circular left ventricle.
• This collapse of the right ventricle impairs diastolic filling, reducing cardiac output and potentially leading to cardiac tamponade, a life-threatening condition characterized by decreased cardiac output, elevated systemic venous pressure, and hypotension, as noted in the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.
• The collapse typically occurs during diastole when right ventricular pressures are at their lowest, and can be identified by echocardiography, which is the single most useful diagnostic tool to identify pericardial effusion and estimate its size, location, and degree of hemodynamic impact 1.

Overall, the right ventricle's collapse under pericardial effusion is a critical condition that requires prompt diagnosis and treatment to prevent cardiac tamponade and its potentially fatal consequences, as emphasized in the 2015 European Association of Cardiovascular Imaging and the Acute Cardiovascular Care Association recommendations 1.

From the Research

Right Ventricle Collapse under Pericardial Effusion

The right ventricle collapse under pericardial effusion can be attributed to several factors, including:

• Higher myocardial fiber stress on the interventricular septum 2
• An extensible pericardium that reduces motion of ventricular chambers, with the right ventricle being particularly restrained 2
• Pressure equalization between the right ventricle and the pericardial effusion, leading to reduced right ventricular myocardial stress 2
• Diastolic filling of the right ventricle being particularly restricted due to the pericardial effusion 2

Mechanisms of Pericardial Effusion

Pericardial effusion is a pathological accumulation of fluid within the pericardial cavity, which can compress heart chambers and lead to hemodynamic impairment 2. The mechanics underlying the physiology of hemodynamic impairment due to pericardial effusion can be understood through patient-specific computational modeling 2.

Clinical Implications

The diagnosis of pericardial effusion and tamponade relies on a strong clinical suspicion and is confirmed by echocardiography or other pericardial imaging modalities 3, 4, 5. The treatment of tamponade involves drainage of the effusion and prevention of reaccumulation 3, 5.

Diagnostic Approaches

Echocardiography is usually the primary diagnostic tool when pericardial effusion is suspected, as it is accurate, non-invasive, widely available, and feasible also with pocket-size devices 4. Focused cardiac ultrasound (FOCUS) can be performed by non-cardiologists in emergency settings or at bedside to detect pericardial effusion 4.