INTERPRETATION of ABNORMAL ECGs-
ABNORMAL COMPONENT-
POSSIBLE CAUSES
P waves (abnormal)
Left or right atrial hypertrophy, atrial escape (ectopic) beats
P waves (absent)
Atrial fibrillation, sinus node exit block, hyperkalemia (severe)
P-P interval (varying)
Sinus arrhythmia
PR interval (long)
First-degree atrioventricular block, Mobitz type I atrioventricular block, multifocal atrial tachycardia
QRS complex (wide)
Right or left bundle branch block, ventricular flutter or fibrillation, hyperkalemia
QT interval (long)
MI, myocarditis, hypocalcemia, hypokalemia, hypomagnesemia, hypothyroidism, subarachnoid or intracerebral hemorrhage, stroke, antiarrhythmics (eg, sotalol Some Trade Names
BETAPACE
, amiodarone Some Trade Names
CORDARONE
), tricyclic antidepressants, other drugs
QT interval (short)
Hypercalcemia, hypermagnesemia, Graves' disease, digoxin Some Trade Names
DIGITEK
LANOXIN
ST segment (depression)
Myocardial ischemia; acute posterior MI; digoxin Some Trade Names
DIGITEK
LANOXIN
; ventricular hypertrophy; pulmonary embolism; left bundle branch block; right bundle branch block in leads V1 −V3 +/− II, III, and aVF; hyperventilation; hypokalemia
ST segment (elevation)
Myocardial ischemia, acute MI, left bundle branch block, acute pericarditis, left ventricular hypertrophy, hyperkalemia, pulmonary embolism, digoxin Some Trade Names
DIGITEK
LANOXIN
, normal variation (eg, athletic heart syndrome), hypothermia
T wave (tall)
Hyperkalemia, acute MI, left bundle branch block, stroke, ventricular hypertrophy
T wave (small, flattened, or inverted)
Myocardial ischemia, age, race, hyperventilation, anxiety, drinking hot or cold beverages, left ventricular hypertrophy, certain drugs (eg, digoxin Some Trade Names
DIGITEK
LANOXIN
, pericarditis, pulmonary embolism, conduction disturbances (eg, right bundle branch block), electrolyte disturbances (eg, hypokalemia)
U wave (prominent)
Hypokalemia, hypomagnesemia, ischemia