Page 35 - Medicine and Surgery

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Chapter 2: Clinical 31

procedures and they may also become infected from any suitable interval by a ventricular beat if the atrium
source of bacteraemia. does not contract spontaneously.

Procedure
Permanent pacemakers The pacemaker is inserted under local anaesthetic nor-
mally taking 45 minutes to 1 hour. A small diagonal
Cardiac pacemakers are used to maintain a regular incision is made a few centimetres below the clavicle and
rhythm, by providing an electrical stimulus to the heart the electrodes are passed transvenously to the heart. The
through one or more electrodes that are passed to the pacemaker box is then attached to the leads and im-
rightatrium and/or ventricle. planted subcutaneously. The procedure is covered with
Common indications for a permanent pacemaker: antibiotics to reduce the risk of infection.
Complete heart block.

Sick sinus syndrome with symptomatic bradycar- Complications

dia. The procedure is generally low-risk. The most impor-
tant complications are pneumothorax due to the venous
access and surgical site infection. As long as aspirin and
Types of permanent pacemaker anti-coagulants are stopped prior to the procedure, sig-
There are several types of pacemaker, most pacemak- nificant haematoma or bleeding is unusual.
ers are programmable through the skin by radio trans- The pacemaker function is checked within 24 hours
mission. Pacemakers may be single chamber, i.e. single of implantation. Annual follow-up is required to ensure
electrode usually to the right ventricle, or dual cham- that the battery life is adequate and that there has not
ber, i.e. one electrode to the right ventricle and one to been lead displacement. Patients are allowed to drive
the right atrium. The descriptive code for the most com- after 1 month (current DVLA rules), i.e. after the 4-week
monly used pacemakers consists of up to four letters (see pacemaker check. Most pacemakers last 5–10 years.
Table 2.3). In electromagnetic fields such as in airport security
Common types of pacemakers are as follows: most pacemakers are now programmed to go into a de-
VVI is a single chamber pacemaker that senses and fault pacing mode so as not to fail. Even so patients are

paces the ventricle. If it senses a beat, the paced beat advised to avoid close proximity to strong electromag-
is Inhibited. It is often used in patients with atrial netic fields. MRI scanning is contraindicated and pace-
fibrillation with AV block. makers must be removed postmortem, if the patient is
DDD is a dual chamber pacemaker that is capable to be cremated.

of sensing and pacing both the atrium and ventricle.
It is used in complete heart block in the absence of Echocardiography
atrial fibrillation. It can sense if an atrial beat is not
followed by a ventricular beat (due to lack of AV node Echocardiography essentially means ultrasonography of
conduction), in which case it will trigger a ventricular the heart. It is a very useful, non-invasive method by
beat. It can also trigger an atrial beat followed at a which the heart and surrounding structures can be

Table 2.3 Descriptive codes for pacemakers
Code position
1 2 3 4
Category Paced chamber Sensed chamber Pacemaker response Program functions
V(Ventricle) V (Ventricle) T (Triggered) P (Programmable)
A (Atrium) A (Atrium) I (Inhibited) M (Multi-programmable)
D (Dual) D (Dual) D (Dual) 0 (none)
0 (none) R (Reverse) R (Rate responsive)