Page 58 - Medicine and Surgery

P1: JYS
BLUK007-02 BLUK007-Kendall May 25, 2005 17:25 Char Count= 0

54 Chapter 2: Cardiovascular system

Ventricular arrhythmias Management
Ventricular ectopic beats do not require treatment al-
Ventricular ectopic beats though any underlying cause should be identified and
managed.
Definition
Aventricular ectopic/extrasystole/premature beat is an
extramyocardial depolarisation triggered by a focus in Prognosis
the ventricle. Ventricular ectopics worsen the prognosis in patients
with underlying ischaemic heart disease but there is no
evidence that anti-arrhythmic drugs improve this.
Aetiology/pathophysiology
Ventricular ectopics are not uncommon in normal indi-
viduals and increase in incidence with advancing age.
Common causes include ischaemic heart disease and Ventricular tachycardia
hypertension. Ectopic beats may arise due to any of Definition
the mechanisms of arrhythmias, such as a re-entry cir- Tachycardia of ventricular origin at a rate of 120–220
cuit or due to enhanced automaticity (which may occur bpm.
with electrolyte abnormalities, alcohol or nicotine ex-
cess, anaemia, medications such as β agonists or hypox-
Aetiology
aemia). When ventricular ectopic beats occur regularly
Ventricular tachycardia is normally associated with un-
after each sinus beat, it is termed bigeminy, which is fre-
derlying coronary, ischaemic or hypertensive heart dis-
quently due to digoxin.
ease, or cardiomyopathies.
Clinical features
Patients are usually asymptomatic but may feel uncom- Pathophysiology
fortable or beaware of an irregular heart or missed beats. The underlying mechanism is thought to be enhanced
On examination the pulse may be irregular if ectopics automaticity,leadingtore-entrycircuitasinothertachy-
are frequent. cardias. In ventricular tachycardia there is a small (or
sometimes large) group of ischaemic or electrically non-
homogeneouscells,typicallyresultingfromanacutemy-
Investigations
ocardial infarction.
ECGshowsbroadbizarreQRScomplexeswithoutpre-

ceding P, followed by an inverted T wave and then a
pause before the next sinus beat (see Fig. 2.9). Clinical features
Echocardiography and exercise testing may be used The condition is episodic with attacks usually lasting

to look for underlying structural or ischaemic heart minutes. Patients may experience palpitations, short-
disease. ness of breath, chest pain and if there is a resultant

Sinus beat Pause

Rhythm strip
(II) Ectopic beat

Figure 2.9 Ventricular ectopic beat.