Cardiac Tamponade Under Positive-Pressure Ventilation: Pathophysiological Insights and Implications for Diagnosis

Fig. 1.. Transthoracic echocardiography (subcostal five-chamber view) showing a circumferential pericardial effusion. Representative subcostal TTE image demonstrating an anechoic pericardial fluid layer surrounding the heart, consistent with circumferential pericardial effusion. This first-line view is commonly used in emergency and ICU settings to rapidly confirm effusion presence and guide escalation to hemodynamic assessment and drainage when tamponade physiology is suspected. ICU, intensive care unit; TTE, transthoracic echocardiography; MI, mechanical index; 2D, two-dimensional echocardiography; bpm, beats per minute.

Fig. 2.. Transthoracic echocardiography (subcostal view) showing a large circumferential pericardial effusion. Subcostal TTE image demonstrating a prominent anechoic pericardial fluid layer encircling the heart; caliper measurement indicates an effusion thickness of approximately 2.92 cm. This view is commonly used at the bedside to rapidly quantify effusion size and support urgent evaluation for tamponade physiology in unstable patients.

Fig. 3.. Transesophageal echocardiography (transgastric short-axis view) showing pericardial effusion with suspected posterior intrapericardial clot. Transgastric mid–short-axis TEE image demonstrating pericardial fluid with echogenic material along the posterior pericardial space, suggestive of organized clot/loculated postoperative collection. TEE, transesophageal echocardiography.

Fig. 4.. Transesophageal echocardiography (mid-esophageal four-chamber view) showing pericardial effusion with intrapericardial clot causing right-sided chamber compression. Mid-esophageal four-chamber TEE image demonstrating pericardial fluid with echogenic organized material consistent with clot, associated with focal external compression of the right atrium and right ventricle—an imaging pattern typical of regional/loculated postoperative tamponade and one that may be underestimated on transthoracic windows.

Fig. 5.. Pericardial effusion on TEE in a mechanically ventilated patient. Mid-esophageal four-chamber TEE view demonstrating a pericardial effusion with predominant distribution around the apical/peri-ventricular region (maximal separation ≈22 mm). This example illustrates how clinically relevant effusions may be incompletely characterized on TTE in ventilated/postoperative patients and supports early TEE when TTE is nondiagnostic or when regional/loculated disease is suspected. LV, left ventricle; PPV, positive-pressure ventilation .

Fig. 6.. Blunted transmitral respiratory variation under positive-pressure ventilation. Transesophageal pulsed‐wave Doppler of mitral inflow in a mechanically ventilated ICU patient with pericardial tamponade, showing fused E/A waves and minimal beat-to-beat (respiratory) variation in peak diastolic velocity under positive-pressure ventilation. Classic respirophasic transmitral cut-offs are therefore not met despite hemodynamically significant tamponade, illustrating the limited reliability of Doppler “pulsus paradoxus” criteria in patients receiving PPV. Abbreviations: E/A, early (E) and late atrial (A) diastolic inflow waves; ICU, intensive care unit.

Fig. 7.. Blunted tricuspid respiratory variation under positive-pressure ventilation. Transesophageal pulsed-wave Doppler of tricuspid inflow in the same mechanically ventilated ICU patient with pericardial tamponade, showing only minimal respiratory variation in diastolic flow velocities, illustrating how positive-pressure ventilation can blunt the classic respirophasic Doppler changes of cardiac tamponade.

Fig. 8.. Pathophysiological vicious cycle of cardiac tamponade under positive-pressure ventilation. PPV increases intrathoracic pressure and reduces venous return, leading to impaired RV filling, increased pulmonary vascular resistance and RV afterload, ventricular interdependence with reduced LV output, and a fall in stroke volume and blood pressure culminating in hypotension or shock. The circular arrows indicate the self-reinforcing sequence by which PPV and subsequent escalation of airway pressures may progressively amplify hemodynamic compromise in the setting of pericardial constraint. Further escalation of PEEP/airway pressures and fluid loading worsens pericardial constraint and congestion, producing pericardial effusion/cardiac tamponade with masked pulsus paradoxus. Abbreviations: LV, left ventricle; PEEP, positive end-expiratory pressure.

Fig. 9.. LVOT VTI under positive-pressure ventilation in cardiac tamponade physiology. Pulsed-wave Doppler of the LVOT shows marked respiratory variation in systolic ejection, consistent with exaggerated ventricular interdependence and ventilator-phase–dependent hemodynamic fluctuation. Abbreviations: LVOT, left ventricular outflow tract; VTI, velocity–time integral.