Blunt Cardiac Injury
Blunt cardiac injury is blunt chest trauma that causes contusion of myocardial muscle, rupture of a cardiac chamber, or disruption of a heart valve. Sometimes a blow to the anterior chest wall causes cardiac arrest without any structural lesion (commotio cordis).
(See also Overview of Thoracic Trauma.)
Manifestations vary with the injury.
Myocardial contusion may be minor and asymptomatic, although tachycardia may be present. Some patients develop conduction abnormalities and/or dysrhythmias.
Ventricular rupture is usually rapidly fatal, but patients with smaller, particularly right-sided, lesions may survive to present with cardiac tamponade. Tamponade due to atrial rupture may manifest more gradually.
Valve disruption may occur, causing a heart murmur and sometimes manifestations of heart failure (eg, dyspnea, pulmonary crackles, sometimes hypotension), which may develop rapidly.
Septal rupture may not cause symptoms initially, but patients may present later with heart failure.
Commotio cordis is sudden cardiac arrest that follows a blow to the anterior chest wall in patients who do not have pre-existing or traumatic structural heart disease. Typically this blow involves a fast, hard projectile (eg, baseball, hockey puck) with relatively low kinetic energy. Pathophysiology is unclear, but the timing of the blow in relation to the cardiac cycle may be important. Initial rhythm is usually ventricular fibrillation.
Cardiac injury should be suspected in patients with significant chest or multiple blunt trauma and any palpitations, dysrhythmia, new cardiac murmur, or unexplained tachycardia or hypotension.
Most patients with significant blunt chest trauma should have 12-lead ECG. With myocardial contusion, ECG may reveal ST segment changes that mimic cardiac ischemia or infarction. The most common conduction abnormalities include atrial fibrillation, bundle branch block (usually right), unexplained sinus tachycardia, and single or multiple premature ventricular contractions. Echocardiography is sometimes done during the initial resuscitation and may show wall motion abnormalities, pericardial fluid, or chamber or valvular rupture. Patients suspected of having blunt cardiac injury because of clinical or ECG findings should have formal echocardiography to evaluate function and anatomic abnormalities.
Cardiac markers (eg, troponin, CPK-MB) are most useful to screen for and thus help exclude blunt cardiac injury. If cardiac markers and ECG are normal and there are no arrhythmias, blunt cardiac injury can be safely excluded.
Patients with myocardial contusion causing conduction abnormalities require cardiac monitoring for 24 h because they are at risk for sudden dysrhythmias during this time. Treatment is mainly supportive (eg, treatment of symptomatic dysrhythmias or heart failure) and is seldom needed. Surgical repair is indicated for rare cases of myocardial or valvular rupture.
Patients with commotio cordis are treated for their dysrhythmia (eg, resuscitation with CPR and defibrillation followed by in-hospital observation).
Blunt cardiac injury should be suspected in patients with significant chest or multiple blunt trauma and any palpitations, dysrhythmia, new cardiac murmur, or unexplained tachycardia or hypotension.
ECG and cardiac markers are useful to screen for injury, and echocardiography is helpful to evaluate function and anatomic abnormalities.
Patients with conduction abnormalities or dysrhythmias require cardiac monitoring.