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Chapter 2: Cardiac arrhythmias 51

Figure 2.6 ECG in atrial flutter showing flutter waves revealed by carotid sinus massage.

Incidence rate,in the elderly who depend on atrial function to
Common achieve sufficient ventricular filling, or if there is associ-
ated significant cardiac damage. Abnormal atrial blood
Age flow predisposes to thromboembolism.
Increases with age: 1% in people aged 60 years and 5%
over 70 years. Clinical features
Atrial fibrillation is often asymptomatic. Patients may
Sex present with palpitations, acute cardiac failure or the
M > F gradual onset of increasing shortness of breath. On ex-
amination there is an irregularly irregular pulse with
Aetiology varying pulse volume. There is also loss of the ‘a’ wave of
Causes may be divided into cardiac and systemic. Lone the JVP.
atrial fibrillation is when no structural or organic cause
can be found. Investigations
Cardiac: Atrial enlargement is a common mecha- ECG shows fine irregular oscillations of the base line,

nism for the onset of atrial fibrillation. Various car- with a QRS totally irregular in timing normally at a
diac and systemic conditions cause a chronic rise in rate of between 100 and 160 bpm (see Fig. 2.7).
atrial pressure and in time lead to atrial enlargement, Thyroid function tests should be performed in all pa-
e.g. ischaemic, hypertensive and rheumatic heart dis- tients.Inacuteatrialfibrillation,underlyingischaemia
ease, mitral valve disease, cardiomyopathies and pul- such as a recent myocardial infarction or unstable
monary disease. angina should be excluded.
Systemic causes include thyrotoxicosis, alcohol and

acute infections especially pneumonia. Management
Restorationofsinusrhythmmaybeachievedwithsyn-

Pathophysiology chronised DC cardioversion or by use of amiodarone
Atrial fibrillation is the result of multiple re-entrant cir- or other drugs. DC cardioversion has a high relapse
cuits in the atria (see above). Since each of these nu- rate. The longer the atrial fibrillation has been present,
merous circuits have different cycle times, the result is a the less the likelihood of restoring sinus rhythm.
constant train of irregular impulses of various amplitude Maintenance of sinus rhythm may be achieved with
reaching the AV node, resulting in a very irregular ven- anti-arrhythmic drugs, but long-term use of amio-
tricular response. The AV node blocks some of the trans- darone has significant side effects. Digoxin does not
missions, but an irregularly irregular pulse of between prevent recurrence.
100 and 160 per minute usually results. Atrial fibrilla- Control of the ventricular rate is achieved with drugs
tion may be paroxysmal with attacks lasting minutes to such as digoxin, calcium channel blockers and/or β-
hours. Symptoms may arise if there is a high ventricular blockers.