Low-Pressure Pericardial Tamponade: Case Report and Review of the Literature.

BACKGROUND: Focused cardiac ultrasound (FoCUS) is accurate for determining the presence of a pericardial effusion. Using FoCUS to evaluate for pericardial tamponade, however, is more involved. Many experts teach that tamponade is unlikely if the inferior vena cava (IVC) shows respiratory variation and is not distended. CASE REPORT: A 53-year-old woman presented to the emergency department (ED) with severe orthostatic hypotension, exertional dyspnea, and hypoxia. The evaluation did not reveal an acute cardiopulmonary etiology, but FoCUS demonstrated a pericardial effusion, with several signs consistent with tamponade. The IVC, however, was not distended. She was believed to be hypovolemic, but fluid therapy provided minimal benefit. The patient's condition improved only after aspiration of the effusion. The patient's presentation was likely a "low-pressure" pericardial tamponade. Patients with this subset of tamponade often do not have significant venous congestion, but urgent pericardial aspiration is still indicated. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Pericardial tamponade may not manifest with IVC plethora on ultrasound. Patients with low-pressure tamponade do not present with the most florid signs of tamponade, but they nonetheless fulfill diagnostic criteria for tamponade. If a non-plethoric IVC is used to rule out tamponade, the clinician risks delaying comprehensive echocardiography or other tests. Furthermore, the potential for deterioration to frank shock could be discounted, with inappropriate disposition and monitoring.