This monthly series of electrocardiograms (ECG) for physicians interested in electrocardiography will be presented to demonstrate basic electrocardiographic and electrophysiologic principles. Initial issues will provide a foundation upon which we shall build as more complex arrhythmias are discussed. Occasionally, we will include pertinent references and briefly mention therapy when appropriate.
The ladder diagram will be employed frequently to depict depolarization and conduction schematically. Straight lines drawn on a tiered framework beneath an ECG trace represent electrical events occurring in the various cardiac structures (Fig 1).
Certain features of the ladder diagram need further explanation. Since the ECG, and, therefore, the ladder diagram, record electrical activity against a time base, conduction is indicated by the sloping lines of the ladder diagram in a left to right direction. A less steep line depicts slower conduction; a short bar drawn perpendicular to a sloping line represents blocked conduction (Fig 2).
On occasion, activity
Zipes DP, Fisch C. IntroductionPremature Ventricular Beats. Arch Intern Med. 1971;128(1):140–142. doi:10.1001/archinte.1971.00310190144018