Low QRS voltage

Low QRS voltage is a non-specific electrocardiographic finding in which the voltage (the height) of the QRS complexes is reduced.

• If the total amplitude above and below the isoelectric line is < 5 mm in all 3 standard leads.
• An average voltage in the limb leads of < 5 mm with an average of < 10 mm in the chest leads.
• Should be at least 5 mm in V₁ and V₆ , 7 mm in V₂ and V₅ and 9 mm in V₃ and V₄.

Low voltage on the ECG tracing generally comes from either Low Power within the myocardium or Low Conduction from the heart to the ECG leads. There are three general processes that contribute to low QRS voltage:

1. Damping of the electrical signal due to excess air (emphysema, COPD), fluid (pericardial effusion, pericardial constriction, pleural effusion), edema (anasarca), fat (obesity), or amyloid cardiomyopathy
2. Electrically inert myocardium due to a loss of viable myocardium such as in myocardial infarction and Chagas disease]]
3. Infiltration of the myocardium (myxedematous, Chagas disease)

The presence of low voltage on the EKG should prompt an evaluation to rule out life threatening emergencies such as cardiac tamponade or a large pericardial effusion. These two diagnoses are suggested by the presence of tachycardia and electrical alternans along with the low QRS voltage. In alphabetical order the differential diagnosis includes^[1]:

• Alcoholic cardiomyopathy
• Amyloidosis
• Anasarca^[2]
• Dilated cardiomyopathy^[3]
• Beriberi heart disease
• Cardiomyopathy
• Chagas disease
• Diffuse coronary artery disease
• Congestive heart failure
• Constrictive pericarditis
• COPD
• Dilated cardiomyopathy
• Generalized edema and pedal edema^[2]
• Emphysema
• Hemochromatosis
• Hypothermia
• Hypothyroidism
• Ischemic cardiomyopathy
• Prior myocardial infarction
• Myocarditis^[4]
• Myxedema
• Obesity
• Pericardial effusion
• Pneumothorax
• Rejection after heart transplantation
• Restrictive cardiomyopathy
• Sarcoidosis
• Scleroderma
• Tamponade
• Technical error in the settings on the ECG apparatus (sensitivity should be at 10 mm/mV)