When electrical alternans is found on an ECG, further evaluation is needed because treatment will vary based on the underlying pathophysiology. Therefore, a thorough history and examination of the patient are necessary to focus on the cardiovascular and pulmonary exam. In the case of pericardial effusion, patients are usually asymptomatic unless tamponade physiology is present. Signs of tamponade include Becks triad: hypotension, muffled heart sounds, and distended neck veins. Additional signs of tamponade may also include tachypnea and dyspnea in the form of Kussmaul breathing and Pulsus Paradoxus.[6] In the case of arrhythmias, as mentioned above, patients may present with tachycardia and associated symptoms of light-headedness, fatigue, chest pain, shortness of breath, syncope, among others along with a potential history of cardiac conduction abnormalities. Based on this, a further cardiac history, including family history, may need to be obtained.

When electrical alternans is present on an ECG, further evaluation is needed to find the underlying cause as mentioned above. When considering a pericardial effusion, a transthoracic echocardiogram (TTE) is the first-line imaging modality. In the unstable patient, bedside echocardiogram is even more important as TTE provides very high sensitivity (near 100%) in diagnosing pericardial effusion.[7]

Once diagnosed, to treat serious tamponade pathology; you must first address resuscitative measures including intravenous (IV) access, oxygen as needed and cardiac monitoring. Intravenous fluid boluses may be needed to promote right heart filling and function to temporize poor hemodynamics. For definitive treatment of tamponade, however, a pericardiocentesis is necessary. This is typically performed in a cardiac catheterization lab in a non-life-threatening situation. However, in urgent conditions, for example, in patients at risk of arrest or who may have arrested, percutaneous pericardiocentesis may be performed in the emergency department. Once a pericardiocentesis and removal of fluid have been performed, and the patient is stabilized, further investigation is required to determine what pathophysiological process lead to the effusion.

For other causes of alternans including WPW, ventricular arrhythmias, and bundle branch block, therapy must be directed toward the underlying cause, with the early emphasis on hemodynamic stability of the patient as the first step in treatment.

• Alternans bundle branch block

• Aortic stenosis

• Air embolism

• Bigeminy

• Cardiac rupture

• Digoxin toxicity- bidirectional ventricular tachycardia

• Myocardial contusion

• Massive pulmonary embolus

• Wide varying tidal volumes in severe tachypnea

• Ventricular septal defect

Electrical alternans, although considered pathognomonic for pericardial effusion, is not a diagnostic factor for effusion and cardiac tamponade as other pathologies can result in this ECG finding. When present on an ECG, early evaluation of the patient’s vitals and overall presentation are imperative. If and when the patient is stable following resuscitation, further evaluation of the heart, including echocardiogram, is necessary to identify the underlying pathology and rule out tamponade. If tamponade physiology is present on imaging or hemodynamic instability from tachycardic rhythms is present further action needs to be taken with a focus on hemodynamic stability, then correction of the underlying pathophysiology.

Healthcare workers should be aware that Electrical alternans, although considered pathognomonic for pericardial effusion, is not a diagnostic factor for effusion and cardiac tamponade as other pathologies can result in this ECG finding. If the rhythm is noted on the ECG, the next step is to order an echocardiogram and consult with a cardiologist. If the patient is hemodynamically unstable, immediate drainage of the pericardial fluid is required. The most compelling fact is that electrical alternans is not a benign event and one should always rule out cardiac tamponade first.