One result of the cardiac compression is an increased diastolic pressure. A narrowing pulse pressure will develop as systolic pressure falls with reduced cardiac output but diastolic pressure remains high because of cardiac compression. JVD may develop secondary to decreased venous return to the right side of the heart, though it may be absent when there is significant bleeding from other injuries. In addition to the reduced cardiac output, cardiac tamponade reduces myocardial perfusion via compression of the coronary arteries, decreasing myocardial oxygen supply during a period of increased myocardial oxygen demand, further stressing the heart.
Clinical exam findings
The classic clinical exam findings associated with cardiac tamponade include hypotension, JVD and muffled heart tones, a trio of signs known collectively as Beck’s triad. This triad is difficult to identify in the prehospital environment, as auscultation of heart sounds, and the identification of muffled ones, can prove difficult in noisy environments. As the tamponade evolves, hypotension and tachycardia will be present, as will a narrowing pulse pressure and possibly pulsus paradoxus (a drop in systolic blood pressure of more than 10 mmHg during inspiration).
Management of pericardial tamponade centers on airway control, oxygenation, and support of ventilation and circulation. Signs and symptoms of pericardial tamponade can mimic those of tension pneumothorax, although the presence of bilateral lung sounds can rule out the latter. For patients who are hypotensive, rapid volume expansion with isotonic crystalloid will increase venous pressures, resulting in increased preload and increased cardiac output, elevating systolic pressures. In some systems, pericardiocentesis can be performed for patients in extremis; however, this is most safely performed in the hospital with ultrasound guidance. In this procedure a needle is inserted into the pericardial space to withdraw blood. Aspiration of as little as 5–10 mL may result in dramatic clinical improvement.6
Blunt Cardiac Trauma
Blunt cardiac trauma is a term that represents a spectrum of myocardial injury that includes myocardial concussion, myocardial contusion and myocardial rupture. The term myocardial concussion, or commotio cordis, describes an acute form of blunt cardiac trauma that does not result in direct injury to the myocardium. Myocardial contusion occurs when the myocardium is bruised, most often by blunt force trauma. Myocardial rupture is the acute traumatic rupture of the atrial or ventricular wall.
Myocardial concussion is usually produced by a sharp, direct blow to the sternal area that stuns the myocardium and results in brief dysrhythmia, hypotension and possibly loss of consciousness. If the dysrhythmia resolves spontaneously, the patient will likely survive with no discernable damage to the myocardium. Alternatively, sudden cardiac death can occur secondary to a more severe or prolonged dysrhythmia. This has been observed in athletes who are struck in the chest with baseballs or other objects. In these cases, the treatment is rapid defibrillation followed by standard ACLS care.
A myocardial contusion usually results from blunt force trauma to the sternal area that compresses the heart between the sternum and spinal column, resulting in injury to the myocardium. Myocardial injury can include hemorrhaging within the myocardium, edema, ischemia and necrosis, all resulting in cardiac dysfunction.
Myocardial rupture occurs when blunt force trauma results in an increase of intraventricular or intra-arterial pressure significant enough to rupture the myocardial wall. It is most often the result of high-speed motor vehicle crashes; it is almost always immediately fatal.10
Clinical exam findings
The clinical exam of the patient with a cardiac contusion will reveal soft tissue injury (e.g., abrasions, contusions, ecchymosis) and possibly skeletal injury (fractured ribs, flail segment, flail sternum) on the anterior chest wall near the sternum. Sinus tachycardia and cardiac dysrhythmia are possible, and hypotension can present in severe cases. The most common signs of cardiac rupture include hypotension; tachycardia; JVD; cyanosis of the head, neck, arm and upper chest; unresponsiveness; distant heart sounds; and concomitant chest trauma.6
Blunt Aortic Injury
The term blunt aortic injury describes a spectrum of injury that ranges from small tears in the aortic intima (the innermost layer of an artery) to complete transection of the aorta, which is almost always fatal. Up to 90% of patients with blunt aortic injury die at the site of the accident or within hours of hospital admission. Wherever it falls on the spectrum, blunt aortic injury is a life-threatening injury, and is usually the result of an unrestrained frontal collision or violent lateral blunt impact to the chest.