Biomedical Engineering Reference
In-Depth Information
Fig. 4.4
Ventricular
arrhythmia [ 24 ] (Used with
permission of C. Cihalik
Palacky University
Olomouc, Czech Republic)
The rate of this tachycardia is 150-200 beats/min. Currently,
the usual method of treatment of AVNRT is radiofrequency
catheter ablation. An acute attack is terminated by vagal
maneuvers or pharmacologically.
include some antiarrhythmic agents, electrical cardioversion,
and overdrive pacing with a rate higher than the flutter rate.
Radiofrequency catheter ablation is also a method of choice.
4.1.2.6 Atrial Fibrillation
Atrial fibrillation is the most common clinically significant
arrhythmia, the prevalence of which increases with age. It is
also based on a reentry mechanism. There is a high risk of
embolism. With a longer duration of atrial fibrillation, elec-
trical and mechanical remodeling of the atrium occurs. No P
waves are discernible on the ECG curve, and the isoelectric
line is irregular. The rate of the fibrillation waves ranges
from approximately 340 to 600/min, with an irregular con-
duction to the ventricles. Treatment with certain antiarrhyth-
mic agents as well as electrical cardioversion is possible.
When classic treatment methods fail, radiofrequency cathe-
ter ablation in the left atrium and pulmonary vein isolation
are the methods of choice.
4.1.2.4 Atrioventricular Reentrant Tachycardia
AV reentrant tachycardia (AVRT) is caused by the presence
of a pathway that actually short-circuits an electrically inert
fibrous ring separating the atria from the ventricles. The ring
is an insulating tissue and electrically separates the atria from
the ventricles. The accessory pathway can cause the develop-
ment of macroreentry by an impulse conducted from the atria
to the ventricles by the AV node and returned to the atrium via
the pathway, or vice versa. The conductive pathway can cause
the development of another supraventricular tachycardia by
conducting atrial activity to the ventricles, with a risk of
developing ventricular fibrillation. On a surface ECG, the P
waves follow the QRS complex. The rate of this tachycardia
is 150-250 beats/min. The method of treatment of AVRT is
radiofrequency catheter ablation. An acute attack can be ter-
minated by vagal maneuvers or pharmacologically.
4.1.2.7 Junctional Rhythm
Junctional rhythm typically occurs only in sinus node abnor-
malities. Its rate is 35-50 beats/min. If faster, it is an active
junctional rhythm or junctional tachycardia. In sustained
forms, treatment is the same as that for bradycardias or AV
blocks (i.e., cardiac pacing).
4.1.2.5 Atrial Flutter
Atrial flutter is a regular monomorphic tachycardia caused by
a reentry mechanism. In its typical form, an impulse circu-
lates in an counterclockwise direction in a defined tissue cir-
cuit in the right atrium. It may often co-occur with another
type of arrhythmia or as a combination of atrial flutter and
fibrillation. An ECG curve with negative saw-tooth flutter
waves is characteristic. The rate of atrial flutter ranges from
approximately 220 to 320 beats/min. Possible treatments
4.1.3
Ventricular Arrhythmias
Ventricular arrhythmias (Fig.
4.4
) include a number of disor-
ders, which often are very serious in terms prognosis. The
