Cardiac causes:
(1) multiple myocardial infarctions
(2) severe post-myocardial infarcton dysynergy
(2) cardiac amyloidosis or other infiltrative cardiomyopathies
(3) myocarditis
(4) reduced cardiac output (from hypovolemia, hemorrhage, etc).
(5) possibly increased hematocrit
(6) change in cardiac position
where:
• An increased hematocrit indicates polycythemia which can occur in COPD.
Pericardial causes:
(1) pericardial effusion
(2) pneumopericardium
(3) thickening of the pericardium
(4) hypothyroidism
where:
• The low voltage QRS in hypothyroidism is usually due to a pericardial effusion but the effect on myocytes may contribute.
Extracardiac causes:
(1) peripheral edema
(2) chronic obstructive pulmonary disease (COPD)
(3) pneumomediastinum
(4) pneumothorax
(5) pleural effusion
(6) subcutaneous emphysema
(7) obesity
(8) pulmonary edema
(9) pneumonia
It can also occur in patients who are otherwise normal (idiopathic).
