cardiac injury will have neither symptoms nor abnormal physical examination findings, and therefore a high index of suspicion is required when the mechanism of injury makes cardiac injury possible FIGURE 115.5 Bedside ultrasound showing large pericardial effusion surrounding the heart Pericardial tamponade may initially be difficult to diagnose because of associated injuries obscuring the clinical signs and symptoms Patients may present with distant heart sounds, low blood pressure, poor perfusion, a narrow pulse pressure, or electromechanical dissociation Pulsus paradoxus, blood pressure falling more than 10 mm Hg during inspiration, occurs in less than onehalf of patients with pericardial tamponade and should not be relied on to make the diagnosis Management The evaluation for suspected blunt cardiac injury includes EKG, serum cardiac troponin, echocardiography, and observation with continuous cardiac monitoring A 12-lead EKG may show ST-T-wave changes or arrhythmias The combination of a normal EKG and negative troponin is highly sensitive for ruling out myocardial contusion or other significant blunt cardiac injury For patients with an abnormal EKG, elevated cardiac enzymes, or new findings on physical examination, echocardiography should be performed