Biomedical Engineering Reference
In-Depth Information
Fig. 4.1
Overview
of arrhythmias
Arrhythmia
Disorders of impulse initiation
Disorders of impulse conduction
Sinus
Sinus bradycardia
Sinus tachycardia
Sinus arrhythmia
Sinus arrest
Sick sinus syndrome
First, second, and third-degree sinoatrial block
First, second, and third-degree atrioventricular block
Bundle branch blocks
Fascicular blocks
Supraventricular
Supraventricular extrasystoles
Atrial tachycardia (focal, multifocal)
Atrioventricular nodal reentrant tachycardia (typical, atypical)
Atrioventricular reentrant tachycardia (orthodromic, antidromic)
Macroreentrant atrial tachycardia (typical and atypical atrial flutter)
Atrial fibrillation
Junctional rhythm
Ventricular
Ventricular asystole
Idioventricular rhythm
Ventricular extrasystoles
Ventricular tachycardia
Torsades de pointes
Ventricular fibrillation
4.1.1.2 Sinus Tachycardia
Sinus tachycardia is a heart rhythm that has a rate of more
than 100 beats/min. Physiologically, it occurs with physical
or mental exertion. It may have a pharmacological cause. If
it is more frequent,
Another arrhythmogenic mechanism, and the most common,
is reentry, that is, a reentrant (circulating) impulse. It may
occur when two sites in the myocardium are connected by
two pathways having different velocities of impulse propa-
gation. This circulating impulse has a higher rate than the
sinus node and is thus a predominant impulse generator.
According to the size of the potential circuit, reentry is
divided into macroreentry (large, occurring around the orifice
of large vessels, the atrioventricular (AV) junction, or an
ischemic focus) and microreentry (small, occurring in the
area of Purkinje fibers). Reentry gives rise to all atrial and
ventricular flutters, tachycardia, and fibrillation.
b
-blockers are the treatment of choice.
4.1.1.3 Sinus Arrhythmia
Sinus arrhythmia is a markedly irregular heart rhythm.
Physiologically, it occurs as respiratory sinus arrhythmia in
which the heart rate accelerates during inspiration and slows
during expiration.
4.1.1.4 Sinus Arrest
Sinus arrest is a transient complete loss of sinus node activ-
ity. Arrests lasting more than 3 s are considered pathological.
When there are significant symptoms, pacing therapy is used
for treatment.
4.1.1
Sinus Arrhythmias
Sinus arrhythmias (Fig.
4.2
) originate in the sinoatrial
node [ 25 ] .
4.1.1.5 Sick Sinus Syndrome
Sick sinus syndrome is a combination of sinus bradycardia
and another arrhythmia, most commonly supraventricular
tachycardia. It occurs in older age because of degenerative
changes in the sinus node, more common ischemia and car-
diac surgery, etc. It may even be caused pharmacologically.
When a patient is symptomatic, pacing therapy is used for
treatment.
4.1.1.1 Sinus Bradycardia
Sinus bradycardia is a heart rhythm that has a rate of under
60 beats/min. Physiologically, it occurs in trained athletes
or during sleep. It can occur in cases of hypothermia,
treatment with
-blockers, or intracranial hypertension.
In symptomatic bradycardias, pacing therapy is the treat-
ment of choice.
b
