Transient loss of consciousness ('blackouts') in over 16s

Why this is important

Patient and witness accounts of TLoC are essential to a correct diagnosis. Information is an important part of the patient journey and central to the overall quality of each patient's experience of the NHS. Improving information for patients was a commitment in the NHS Plan (2000) and more recently in Lord Darzi's review of the NHS, 'High quality care for all' (2008). There is a need to improve and monitor the effectiveness of information provided across the NHS. Good-quality trials in people with TLoC are needed to establish whether providing specific information to people with TLoC and their carers helps healthcare professionals to reach a correct diagnosis more quickly, and improves outcomes for the patient. The information should address which details of a TLoC event are required to aid diagnosis. This would also identify those patients who have been inadvertently sent down the wrong TLoC pathway.

Such studies should consider a number of delivery mechanisms including advice-specific information leaflets or visual data (information given in pictorial form).

Why this is important

The prevalence of syncope during the lifetime of a person living 70 years is estimated to be approximately 42%. The Framingham study on incidence and prognosis of syncope identified people with cardiac syncope to have a poorer prognosis than those with neurally mediated syncope or those in whom the cause of TLoC was uncertain. Risk-stratification studies undertaken in emergency departments in patients with TLoC have identified that an abnormal resting 12-lead ECG at presentation is a marker of high risk of death. A 12-lead ECG is cheap, widely available and can be performed quickly at the patient's bedside. In the past, all recorded ECGs were manually read and interpreted. The quality of interpretation depended on the skill of the interpreter. Most of the ECGs recorded today are digitally acquired and automatically read. Scientific studies have been undertaken to compare the accuracy of this automatic interpretation with expert interpretation in the general population. However, no published scientific studies are available in a population selected for TLoC. It is therefore recommended that studies be undertaken in adults who had TLoC to assess the accuracy of automatically interpreted ECGs versus those interpreted by experts in diagnosing the cause of TLoC, including in people with long QT syndrome.

Why this is important

Current consensus opinion suggests that a single assessment approach has the same diagnostic yield as serial assessments for high-risk cardiac arrhythmias in patients presenting with TLoC, despite there being little evidence to support this approach during the critical phase of a presentation. Variable length QTc and changes in T-wave morphology can occur with heart rates as low as 90 beats per minute and may be paroxysmal in nature. Undertaking a serial assessment approach may therefore be more sensitive in detecting QTc length variability for high-risk patients with potential long QT syndrome during initial presentations than a single recording of an ECG.

Why this is important

Uncomplicated fainting is a very common cause of TLoC. It has a good prognosis and, in most cases, can be diagnosed accurately from the person's history and from observations made by witnesses or healthcare professionals, without the need for any tests. Most healthy people who faint have a normal ECG; in a few, ECG features of no importance may generate unnecessary concern and further tests.

Much less commonly, relatively rare heart conditions cause TLoC in otherwise healthy young people who are at risk of dying suddenly unless the condition is recognised and treated. In many of these people, an abnormal ECG will provide evidence of the heart condition. Although TLoC in these conditions is not usually typical of an uncomplicated faint, the diagnosis has been missed in some people, with disastrous consequences.

It is important that research is conducted to establish whether:

Why this is important

This guideline recommends that people with a suspected cardiac cause of TLoC, who have infrequent episodes (every 1 to 2 weeks or less), should be offered an implantable cardiac event recorder. It is unclear when it would be more cost effective to use a strategy of alternative investigation (for example, external event recording).