Chapter 5: CARDIOLOGY

EKG FINDINGS

RIGHT ATRIAL ENLARGEMENT (RAE)

In right atrial enlargement, the P wave is peaked in V1.

LEFT ATRIAL ENLARGEMENT (LAE)

Left atrial enlargement has a broad, bifid P wave in lead II. Right atrial enlargement (RAE) has a peaked P wave in V1 but may also show peaking in the inferior leads (II, III and aVF).

MNEMONIC: M = MITRAL = LEFT side of the heart. So, an “M” shaped P wave refers to LEFT ATRIAL ENLARGEMENT. P = PULMONIC VALVE = RIGHT side of the heart. So PEAKED P waves in V1 refers to RIGHT ATRIAL ENLARGEMENT.

NEGATIVE T WAVE

Newborns are born with right axis deviation leading to upright T waves in the V1 (right precordial leads). The T waves become negative in V1 (right precordial leads) within the first week of life as the pulmonary vascular resistance decreases. The T wave in V1 should remain negative until at least 6 years of age, and it may remain negative into adolescence. A positive T-wave prior to 6 years of age indicates right ventricular strain.

PREMATURE ATRIAL COMPLEXES (PACs)

This is common in neonates and mostly benign. If a patient is on Digoxin, this could potentially be a concerning finding.

PREMATURE VENTRICULAR COMPLEXES (PVCs)

If PREMATURE VENTRICULAR COMPLEXES (PVCs) are described/shown as monomorphic (of the same morphology), and they diminish with exercise, these are BENIGN.

EKG CHANGES DUE TO ELECTROLYTE DISTURBANCES

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 or HypERmagnesemia: 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 QT.
• MNEMONIC: LOW electrolytes result in a sLOW interval