Drug Effects, Electrolyte Abnormaliites, and Metabolic Disturbances

Question 1

Name some Class 1A drugs and some of their effects in ECG.

Answer 1

Quinidine, Procainamide, Disopyramide. Prolongation of the QRS duration and most importantly QT interval prolongation, leading to increased risk of torsades de pointes and sudden cardiac arrest.

Question 2

Classic ECG findings of tricyclic antidepressants ?

Answer 2

Prolonged QRS and QT interval, along with sinus tachycardia.

Question 3

ECG changes seen with hyperkalemia ?

Answer 3

Narrowing and peaking of the T waves, widening of the QRS complexes eventually leading to a large undulating (sine wave) pattern and asystole, with cardiac arrest.

Question 4

ECG changes seen with hypokalemia ?

Answer 4

ST depressions, prominent U waves and overall prolonged repolarization.

Question 5

Changes seen with Hypercalcemia and Hypocalcemia ?

Answer 5

Ventricular repolarization is shortened by hypercalcemia and lengthened by hypocalcemia. The shortening of the QT interval is due to shortening of the ST segment.

Question 6

Hypomagnesemia has been implicated in which conditions ?

Answer 6

Ventricular arrhythmogenesis with acute MI and also in torsade de pointes. Hypomagnesemia is also important because it may foster hypocalcemia by inhibiting release of parathyroid hormone.

Question 7

Pronnounced elevations of serum magnesium concentration may lead to… ?

Answer 7

Prolonged PR or QRS interval, as well as sinus bradycardia. Extreme elevations may contribute to cardiac arrest.

Question 8

Chnages seen in hypothermia ?

Answer 8

J point elevation (Osborn waves). Hypothermic patients are at increased risk of ventricular fibrillation, which may occur during rewarming.

Question 9

Severe hypothyroidism may lead to ?

Answer 9

Pericardial effusion, thereby causing low voltage QRS complexes.