Crucial to establishing the correct diagnosis is a detailed and accurate history preferably from both the patient and eyewitnesses - unfortunately eye witnesses are not always reliable or available and patient recollections may be sketchy!
The following points are suggestive of a cardiac aetiology - loss of consciousness preceding convulsions, precipitation by exercise or by being startled, family history of sudden and unexplained death, family history of deafness in the patient or other family member, patients whose convulsions respond to anticonvulsants but continue to have episodes of loss of consciousness, some medications can cause arrhythmias.
A syncopal attack or faint is a sudden loss of consciousness and postural tone associated with a drop in cerebral blood flow, usually as a consequence of peripheral vascular reflex mechanisms, and much more rarely as a consequence of primary cardiac events. It can be difficult to distinguish faints from convulsions. Faints are rare in a young child unless precipitated by a painful stimulus (reflex anoxic seizures but common from early puberty to late adolescence. A faint usually occurs on change of posture or on prolonged standing (as in school assembly) whilst a convulsion may occur at any time (particularly on awakening or going to sleep). Loss of colour or limpness can occur with either a faint or convulsion. Loss of consciousness is more gradual in a faint than in a convulsion and is commonly associated with preceding pallor, sweating and blurred vision. Convulsive movements can occur during a faint. Severe and recurrent faints are often called neuro-cardiogenic syncope (neurally-mediated syncope or vasodepressor syncope) - profound bradycardia including asystole may occur and may be accompanied by a range of clinical manifestations including almost all the seizure types associated with epilepsy although their duration is usually shorter than their epileptic equivalents.
Syncopal attacks can occur due to arrhythmias such as heart block (congenial or acquired), the sick-sinus syndrome, paroxysmal tachycardia and the prolonged QT interval (with or without deafness) or to structural cardiac disease e.g. severe aortic stenosis and pulmonary stenosis, tetralogy of Fallot (spells) and cardiomyopathy – both hypertrophic and dilated, primary and severe secondary pulmonary hypertension.
Investigations will be dependent upon the history and examination but should include an ECG and echocardiogram. Those with exercise induced symptoms should have an exercise test. A 24 Holter monitor should be considered for those in whom an arrhythmia is strongly suspected. Tilt testing may also be appropriate.