case1 dizziness

CASE 1: DIZZINESS

History
A 75-year-old man is brought to hospital with an episode of dizziness. He still feels unwell
when he is seen 30 min after the onset. He was well until the last 6 months, since when
he has had some falls, irregularly. On some occasions he lost consciousness and is unsure
how long he has been unconscious. On a few occasions he has fallen, grazing his knees,
and on others he has felt dizzy and has had to sit down but has not lost consciousness.
These episodes usually happened on exertion, but once or twice they have occurred while
sitting down. He recovers over 10–15 min after each episode.

He lives alone and most of the episodes have not been witnessed. Once his granddaughter
was with him when he blacked out. Worried, she called an ambulance. He looked so pale
and still that she thought that he had died. He was taken to hospital, by which time he had
recovered completely and was discharged and told that he had a normal electrocardiogram
(ECG) and chest X-ray.

There is no history of chest pain or palpitations. He has had gout and some urinary fre-
quency. A diagnosis of benign prostatic hypertrophy has been made for which he is on no
treatment. He takes ibuprofen occasionally for the gout. He stopped smoking 5 years ago.
He drinks 5–10 units of alcohol weekly. The dizziness and blackouts have not been asso-
ciated with alcohol. There is no relevant family history. He used to work as an electrician.

Examination
He is pale with a blood pressure of 96/64mmHg. The pulse rate is 33/min, regular. There
are no heart murmurs. The jugular venous pressure is raised 3 cm with occasional rises.
There is no leg oedema; the peripheral pulses are palpable except for the left dorsalis pedis.
The respiratory system is normal.

INVESTIGATIONS

Questions
• What is the cause of his blackout?
• What does the ECG show?

ANSWER 1
The blackouts do not seem to have had any relationship to posture. They have been a mix-
ture of dizziness and loss of consciousness. The one witnessed episode seems to have been
associated with loss of colour. This suggests a loss of cardiac output usually associated with
an arrhythmia. This may be the case despite the absence of any other cardiac symptoms.
There may be an obvious flushing of the skin as cardiac output and blood flow return.
The normal ECG and chest X-ray when he attended hospital after an episode do not rule out
an intermittent conduction problem. On this occasion the symptoms have remained in a
more minor form. The ECG shows third-degree or complete heart block. There is complete
dissociation of the atrial rate and the ventricular rate which is 33/min. The episodes of loss
of consciousness are called Stokes–Adams attacks and are caused by self-limited rapid tachy-
arrhythmias at the onset of heart block or transient asystole. Although these have been
intermittent in the past he is now in stable complete heart block and, if this continues, the
slow ventricular rate will be associated with reduced cardiac output which may cause
fatigue, dizziness on exertion or heart failure. Intermittent failure of the escape rhythm may
cause syncope.

On examination, the occasional rises in the jugular venous pressure are intermittent ‘can-
non’ a-waves as the right atrium contracts against a closed tricuspid valve. In addition,
the intensity of the first heart sound will vary.

!
The differential diagnosis of transient loss of consciousness splits into neurological
and vascular causes. A witness is very helpful in differentiation. Neurological causes
are various forms of epilepsy, often with associated features. Vascular causes are
related to local or general reduction in cerebral blood flow. Local reduction may
occur in transient ischaemic attacks or vertebrobasilar insufficiency. A more global
reduction, often with pallor, occurs with arrhythmias, postural hypotension and
vasovagal faints.

The treatment should be insertion of a pacemaker. If the rhythm in complete heart block
is stable then a permanent pacemaker should be inserted as soon as this can be arranged.
This should be a dual-chamber system pacing the atria then the ventricles (DDD, dual
sensing and pacing, triggered by atrial sensing, inhibited by ventricular sensing) or pos-
sibly a ventricular pacing system (VVI, pacing the ventricle, inhibited by ventricular sens-
ing). If there is doubt about the ventricular escape rhythm then a temporary pacemaker
should be inserted immediately.