Answers

Short answers

1 This patient has carotid sinus syndrome (predominantly cardioinhibitory subtype) causing convulsive syncope.

2 He should have a full history and examination (orthostatic blood pressure and cardiac and carotid auscultation) with 12 lead electrocardiography.

3 General treatments are education and avoidance of triggers. Specific treatments are reserved for difficult cases: for pure cardioinhibition, a permanent pacemaker; for pure vasodepression, midodrine; for mixed cases, trial of pacing with repeat carotid sinus massage.

Long answers
Cause of loss of consciousness
This 78 year old man described frequent and troublesome episodes of transient loss of consciousness. He also noted associated involuntary movements of his limbs consistent with convulsive activity. The rapid onset and recovery would not be consistent with epilepsy as a cause for these episodes. The episodes were occasionally associated with head rotation, which suggests carotid sinus syndrome as a cause for his symptoms.¹ The underlying mechanism is cerebral hypoperfusion caused by the drop in blood pressure recorded during carotid sinus massage (see figure).

Carotid sinus massage is performed in patients who do not have evidence of carotid disease and have not had a recent transient ischaemic attack or stroke. Continuous electrocardiography and non-invasive blood pressure monitoring are mandatory. Continuous blood pressure monitoring is done with the Penaz technique of photoplethysmography (most commonly with Finapres, Finometer, and TaskForce devices). A small cuff is placed around the finger; a light emitting diode within it shines a light through the finger and this is detected on the other side. A computer attached to the cuff analyses the amount of light absorbed during its passage through the finger and provides a real time waveform of the patient’s blood pressure.²

During carotid sinus massage, the right carotid artery is firmly massaged for 5-10 seconds at the anterior margin of the sternocleomastoid muscle at the level of the cricoid cartilage. If massage on the right fails to yield a positive result after two minutes, massage is performed on the left. If testing is normal after massage with the patient supine, massage will usually be repeated with the patient semi-upright (70° head-up tilt). If an asystolic response is evoked, to assess the contribution of the vasodepressor component the massage is usually repeated after intravenous atropine is given.³

Carotid sinus massage is considered positive if symptoms occur during or immediately after the massage in the presence of asystole longer than 3 seconds or a fall in systolic blood pressure 50 mm Hg. A positive response is diagnostic of the cause of syncope in the absence of any other competing diagnosis.³

The response is classified as cardioinhibitory if the predominant response to carotid sinus massage is asystolic. It is classified as vasodepressor if the predominant response is hypotensive or as mixed if both contribute equally.³

Complications of carotid sinus massage are rare. They are usually neurological and almost always transient. One series of 5000 massage episodes resulted in two permanent neurological complications, and the total incidence of adverse events was 0.14%.⁴

Convulsive movement during syncope does not imply a diagnosis of epilepsy. Jerky movements of the arms and legs during syncope are not unusual. They are usually of shorter duration than the involuntary movements associated with grand mal epilepsy and tend to occur after the loss of consciousness has set in rather than before, and they are jerkier and do not have the "tonic-clonic" features of a true grand mal epileptic seizure.^{5 6}

Assessment before carotid sinus massage
Current European Society of Cardiology guidelines state that carotid sinus massage should be performed in patients over the age of 40 years with syncope of unknown aetiology after the initial evaluation.³ The initial evaluation includes history, physical examination, supine and upright blood pressure measurement and 12 lead electrocardiography. If structural heart disease has been identified by either history or examination, a full cardiac evaluation should be performed before carotid sinus massage. This should include echocardiography, ambulatory electrocardiography, stress testing, and electrophysiological studies.

If the full history indicates that the patient has had a stroke or transient ischaemic attack in the past three months, carotid sinus massage should be avoided (unless carotid Doppler studies exclude significant stenosis). If a bruit is discovered on carotid auscultation the patient should have carotid Doppler studies.³

Treatment options
All patients should receive education regarding their condition and should be told to avoid any provoking factors that have been identified, such as avoiding tight collars and vigorous head movements and being careful while shaving. Patients who experience presyncopal symptoms should be advised about counter-manoeuvres to abort the episode (for example, supine posture, leg crossing, and arm tugging). Troublesome episodes that risk injury to the patient or others need specific treatment.⁷

Specific treatment is guided by the results of the carotid sinus massage. Dual chamber cardiac pacing helps in cardioinhibitory carotid sinus syndrome.⁸ The European Society for Cardiology guidelines recommend cardiac pacing in patients with cardioinhibitory vasovagal syncope who are aged over 40 and have more than five attacks per year or severe physical injury or accident.⁷

The management of vasodepressor carotid sinus syndrome is more complex. Small series have shown benefits for midodrine⁹ and selective serotonin reuptake inhibitors.^{10 11} Chronic vasodilator therapy has been shown to enhance susceptibility to carotid sinus syndrome,¹² so these drugs should be discontinued or reduced in susceptible patients.

Cite this as: BMJ 2008;337:a2703