ABC of Clinical Electrocardiography
Chapter One
Introduction. I-Leads, Rate, Rhythm, and
Cardiac Axis
Steve Meek, Francis Morris
Electrocardiography is a fundamental part of cardiovascular
assessment. It is an essential tool for investigating cardiac arrhythmias
and is also useful in diagnosing cardiac disorders such as
myocardial infarction. Familiarity with the wide range of patterns
seen in the electrocardiograms of normal subjects and an understanding
of the effects of non-cardiac disorders on the trace are
prerequisites to accurate interpretation.
The contraction and relaxation of cardiac muscle results from
the depolarisation and repolarisation of myocardial cells. These
electrical changes are recorded via electrodes placed on the limbs
and chest wall and are transcribed on to graph paper to produce
an electrocardiogram (commonly known as an ECG).
The sinoatrial node acts as a natural pacemaker and initiates
atrial depolarisation. The impulse is propagated to the ventricles
by the atrioventricular node and spreads in a coordinated fashion
... read full excerpt from ABC of Clinical Electrocardiography (ABC Series #93) ebook
