ABSTRACT
After reading this chapter you should be able to:
draw, label and scale a typical ECG trace, stating the chosen lead (5.1–5.3);
state the origin of the P, QRS and T waves, and the PR and ST intervals (5.2);
explain what a cardiac dipole is (5.4);
sketch out how the cardiac dipole changes with time in the frontal plane during ventricular depolarization (5.5);
explain why different leads record different QRS patterns during the same systole (5.6);
outline the ECG changes caused by ischaemic heart disease (5.9);
state the roles of triggers and substrate in initiating and maintaining arrhythmias (5.10, 3.11);
give the meaning, mechanism and significance of:
heart block;
sinus arrhythmia;
ectopic beat;
atrial tachycardia;
atrioventricular nodal re-entrant tachycardia;
atrioventricular re-entrant tachycardia;
atrial flutter;
atrial fibrillation;
ventricular tachycardia;
ventricular fibrillation.
