Drugs and Metabolic Disorders

This section will provide an in-depth coverage of the ECG changes associated with various drugs and metabolic disorders.

To be covered:

• A general approach to drug effects based on mechanism of action. For example, we review the classes of medications that slow down or hasten spontaneous diastolic depolarization, or prolong the QT.

• An in-depth review of antiarrhythmics, from Class I (and its subtypes) to Class IV. We will talk about toxic effects, such as QRS widening or QTc prolongation, and talk about common therapies. We also talk about specific issues, such as use dependence or reverse use dependence, and associated proarrhythmias (such as slow atrial flutter with 1:1 conduction, torsades de pointes, and so on). 

• The ECG effects of digitalis, and the underlying mechanisms, such as delayed afterdepolarizations. This includes findings such as the digitalis effect or shortened QT, and the various manifestations of digitalis toxicity such as increased ectopy, atrial arrhythmias, AV block, and ventricular arrhythmias (such as the classic bidirectional ventricular tachycardia).

• The ECG effects of miscellaneous drugs, such as beta agonists, atropine, adenosine, tricyclic antidepressants, and anesthetic agents.

• The ECG effects of the most common electrolyte abnormalities, such as hypokalemia or hypomagnesemia, hyperkalemia, hypocalcemia, and hypercalcemia. In addition, we will instruct on how to use the ECG to guide management, like monitoring narrowing of the QRS complex with administration of intravenous calcium in patients with severe hyperkalemia.

• The ECG effects of hypothermia, such as Osborne waves, bradyarrhythmia, ventricular arrhythmias, and interval prolongation.

• The ECG effects of miscellaneous metabolic disorders, such as acid-base disorders (i.e. severe acidosis) and endocrine disorders (i.e. hypothyroidism, hyperthyroidism).