2017 – PAGE 108 – CARDIOLOGY
In right atrial enlargement, the P wave is peaked in V1.
In left atrial enlargement, the P wave is shaped like an “m” in V1, or it is > 3 mm.
The T wave is negative in newborns in lead V1. The T wave becomes positive/upright after the first week of life.
This is common in neonates and mostly benign. If a patient is on Digoxin, this could potentially be a concerning finding.
If PREMATURE VENTRICULAR COMPLEXES (PVCs) are described/shown as monomorphic (of the same morphology), and they diminish with exercise, these are BENIGN.
EKG changes related to hypokalemia, hyperkalemia, hypocalcemia, and hypomagnesemia are electrolyte disturbances that are fairly “testable” for the boards. Potassium changes would be most likely tested.
- HypOkalemia: Prolonged QT, flattened T-waves, ST segment depression, U-waves, and PVCs
- HypERkalemia: Peaked T waves, absent or flat P waves, widened QRS, and Ventricular Tachycardia. This could be associated with electromechanical dissociation. Treat with potassium-lowering drugs (sodium polystyrene, insulin + glucose infusion) and give CALCIUM GLUCONATE.
- MNEMONIC: If you imagine the PQRST of a single beat having a little P, a wide QRS, and a large T, it’s almost as though the extra height in the peaked T waves is causing the QRS complex and the P to be stretched out!
- PEARL/SIDE NOTE: HypERmagnesemia is also treated with CALCIUM GLUCONATE infusions. MAG sulfate is used as a tocolytic and can cause prolonged hypOcalcemia in babies.
- HypOcalcemia: Prolonged QT interval. HypOcalcemia can also result in muscle weakness and tetany.
- HypERcalcemia: Shortens the ST segment, therefore it also shortens the QT interval. The T-wave may be widened.
- HypOmagnesemia: Prolonged QT interval and prolonged PR interval.
- SODIUM CHANGES: There are NO EKG changes with hyponatremia or hypernatremia.
- MNEMONIC: “MELT PC’s because they take too LONG! Buy an Apple instead.” Problems with low Magnesium, Erythromycin, Levofloxacin, TCAs, low Potassium, and low Calcium can result in a LONG
- MNEMONIC: LOW electrolytes result in a sLOW interval