Tachycardias (rapid beating)
If ectopic beats come in runs and occur rapidly they are called
tachycardias, taking their name from the site of origin of the ectopic e.g.,
atria, AV node or ventricular tachycardias. These tachycardias cause
symptoms because the heart rate is increased to approximately 200 beats a
minute. At this rate the heart doesn’t work efficiently and the patient may
sweat, feel weak, become short of breath or even collapse.
AV nodal and ventricular tachycardias cause more symptoms than
atrial tachycardia. Persistence of these rhythms directs the doctor to look for
underlying heart disease.
Atrial fibrillation (irregular beats lacking any pattern)
When the muscle in the atria does not contract together but flutters it
is called fibrillation. This often does not cause symptoms as the ventricles
still contract at a slow though slightly disorganised rate. If the electrical
impulses from the atria enter the AV node, a rapid irregular rhythm causing
palpitations can occur. This can be treated with drugs at an early stage.
Bradycardias (slow beating)
When the pacemaker is diseased the heart rate may fall to very low
levels. Sometimes periods of bradycardia occur with tachycardia and this is
known as sick sinus syndrome.
Slow beating also occurs when there is disease at the AV node
(junction box). This is called heart block when all the impulses do not get
Sometimes the patient is aware of a slow
through to the ventricles.
ponderous beating of the heart associated with dizziness. This is treated
with an artificial pacemaker. (See Heart Information Research Series
Chapter No. 9 ‘Pacemakers’.)