Evaluating tilt table testing in syncope 2: Management options

Authors
Jill Austin, RGN, is junior sister, George Stamp unit, Orpington Hospital, Kent; Aza Abdulla, MBChB, MSc, FRCP, MRCP, is consultant physician, Princess Royal University Hospital, Kent.

The common non-cardiac causes of syncope are:

• Vasovagal syncope;

• Orthostatic hypotension;

• Postural tachycardia syndrome;

• Carotid sinus syndrome.

Vasovagal syncope or neurocardiogenic syncope

Tilt table testing is the definitive investigation for this condition (Frishman et al, 2003).

Vasovagal syncope usually occurs when patients are upright, although it can occur when sitting and is the most common form of syncope in young people. Although there are often no precipitating circumstances, some patients do notice definite triggers, for example heavy meals with alcohol, a warm environment or prolonged standing.

The onset of syncope may be abrupt or gradual with sweating, pallor, nausea, dizziness, lightheadedness and weakness. These symptoms reflect the gradual drop in blood pressure and over-activity of some nerves and muscles to compensate for the decrease in BP. Recovery is rapid once patients are put in a supine position, and they will be unresponsive for less than a minute. This type of syncope is thought to occur due to an exaggerated and inappropriate response of the autonomic nervous system, which responds to a stimuli by a paradoxical lowering of heart rate and BP, resulting in a reduction of blood supply to the brain and loss of consciousness (Grubb, 1999).

Neurocardiogenic syncope can be situational. Episodes are triggered by passing urine, coughing, defecation or swallowing. This is an exaggerated form of fainting, which can be due to a marked drop in BP and/or heart rate. A diagnosis of vasovagal syncope is made if, during head-up tilt testing, the patient experiences a dramatic slowing of the heart rate or even asystole with or without an accompanying precipitous fall in BP, with associated symptoms (Kenny et al, 2000).

The exact pattern of the heart rate and BP changes can help in deciding treatment. Placing the patient in the supine position restores the heart rate and BP to normal and quickly corrects symptoms.

Orthostatic hypotension

Orthostatic hypotension is a common problem, especially in older people. It is due to increased medication usage and decreased physiological function (Frishman et al, 2003). Research shows it is found in 15% of older adults in the community and 52% of nursing home residents (Sclater and Alagiakrishnan, 2004).

Orthostatic hypotension can be:

• Asymptomatic where BP changes without any symptoms;

• Symptomatic, in which symptoms such as dizziness occur with BP changes;

• Acute and often reversible, typically caused by fluid loss or medication use;

• Chronic, usually irreversible, caused by endocrine or neurological factors

Up to 50% of orthostatic hypotension cases are caused by medication use. The most common agents implicated are anti-hypertensives, diuretics, anti-anginal drugs and antidepressants. Their effect is aggravated by alcohol.

Orthostatic hypotension has been defined as a fall of more than 20mmHg in systolic BP within three minutes of standing, associated with symptoms of dizziness, lightheadedness and extreme lethargy (Sclater and Alagiakrishnan, 2004). With severe postural hypotension, syncope can occur. However, even a smaller drop in BP with associated symptoms can be significant. Some patients may have a slow but steady decline in BP over a longer period (10-15 minutes) and are likely to complain of dizziness, lightheadedness, fatigue and blurred vision.

Postural hypotension is more common in the morning and after food (so called post-prandial hypotension). In older people this can lead to symptoms due to the loss of autonomic tone that occurs with ageing.

A diagnosis is made by observing BP and patient response to a change of posture of up to 70 on the tilt table for a period of three minutes or longer in some cases.

Disease or dysfunction of the nervous system can lead to syncope through postural hypotension. These neurogenic reasons can be primary or secondary, associated with a particular disease (see Box 1). One primary cause is Bradbury-Eggleston syndrome, which is a degenerative disorder of the autonomic nervous system, characterised by abnormally low BP on standing. It usually occurs in older men and is thought to be due to failure of a vasoconstrictor sympathetic response to an upright posture.

Postural tachycardia syndrome

Postural tachycardia syndrome (POTS) manifests itself as an excessive increase in heart rate during standing but with little reduction in BP.

Patients with POTS are unable to adjust effectively to upright posture, and usually experience a heart rate increase of more than 30 beats per minute on standing (Grubb, 2000). This exaggerated increase usually occurs within 10 minutes of standing. These patients use about three times more energy to stand than a healthy person. Their symptoms are often life-altering and can be debilitating - they experience fatigue, dizziness and are intolerant to exercise.

People often develop the syndrome following a virus, giving birth or after great physical stress (for example, surgery). Although patients with POTS tend to be aged 15-50 years, two of our patients were over 75. Women are five times more likely to develop the syndrome than men.

Carotid sinus syndrome

This syndrome is a relatively common cause of syncope in older people. In patients with unexplained falls and dizziness, it is found in up to 48% of cases (McIntosh et al, 1993). It is more common in men and rarely seen under the age of 50. The syndrome is associated with coronary artery disease, hypertension and atherosclerosis.

Common precipitating causes are head movements, wearing a tight collar or shaving, most probably due to transient compression of the carotid sinus. Diagnosis is confirmed when carotid sinus massage results in either or both of the following:

• Three seconds of asystole or longer with symptom reproduction (cardioinhibitory);

• A drop in systolic BP of 50mmHg or more with symptom reproduction (vasodepressor).

Cardioinhibitory carotid sinus syndrome is more common than the vasodepressor type and is found in 70% of cases. CSS can be aggravated by some medications such as beta-blockers.

Management

Patient and family education about causes, consequences and management of symptoms is important (Sclater and Alagiakrishnan, 2004). Simple conservative measures are often all that are needed to treat most people for any of the conditions discussed above (Brignole et al, 2004). These include:

• Increasing daily salt and fluid intake (although not in patients with hypertension and heart failure) to maintain BP;

• Small regular meals, six times a day;

• Avoiding alcohol;

• Plenty of fibre to prevent constipation;

• Increasing caffeine intake;

• Avoiding bending at the waist to pick up things from the floor;

• Using a bedside commode or urinal to prevent the need to get up quickly;

• Sitting on the edge of the bed before standing;

• Avoiding any circumstances known to cause or aggravate symptoms;

• Sitting or lying down if patients experience any warning signs.

Well-fitting compression stockings may be useful for some patients. In addition, it is important to review, reduce and possibly discontinue any medications which could be causing or aggravating the situation. A limited number of drugs are available for treatment, notably fludrocortisone, which increases the volume of blood within the veins, and midodrine, which constricts the veins. These drugs are sometimes used to help prevent patients losing consciousness when they stand up. For those with tachyarrhythmias, beta-blockers or calcium-channel blockers such as diltiazem or verapamil may be helpful. In cases of carotid sinus syndrome where a period of asystole has occurred, referral to a cardiologist for permanent pacemaker insertion is indicated.

Conclusion

Syncope is a symptom, not a diagnosis. It is a common symptom with often dramatic consequences, which deserves thorough investigation and appropriate treatment of its cause, although diagnosis can be difficult because of its unpredictable nature.

Diagnosis depends on a good clinical history, ideally supported by a witness, careful physical examination and, where necessary, referral for further investigations.

Treatment depends on identifying the underlying cause - tilt table testing and carotid sinus massage are useful in determining the underlying cause.

References

Brignole, M. et al (2004) Guidelines on management (diagnosis and treatment of syncope: update). European Heart Journal; 25: 22, 2054-2072.

Frishman, W.H. et al (2003) Drug treatment of orthostatic hypotension and vasovagal syncope. Heart Disease; 5: 1, 49-64.

Kenny, R.A. et al (2000) The Newcastle protocols for head-up tilt table testing in the diagnosis of vasovagal syncope, carotid sinus hypersensitivity and related disorders. Heart; 83: 564-569.

Sclater, A., Alagiakrishnan, K. (2004) Orthostatic hypotension. A primary care primer for assessment and treatment. Geriatrics; 59: 8, 22-27.

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