Dizziness is a common symptom and often not of concern. It also means different things to different people. Occasionally dizziness becomes severe and can lead to blackouts where there is a complete loss of consciousness. Dizziness leading to blackouts always needs investigation.
Cardiologists call a blackout ‘syncope’ and a near blackout ‘pre-syncope’. After epilepsy the heart is the commonest cause of syncope. Changes in the heart rhythm are the most likely reason though blackouts can also occur due to structural heart disease – that is an abnormality of the heart muscle or valves. If the heart goes too slowly, or stops for a few seconds it can lead to syncope and this is very easily treated by the implantation of a pacemaker. Most of the time a pacemaker does nothing – just ‘listens’ to the heart – but it kicks in if the heart goes too slow.
Alternatively if the heart goes very fast in an abnormal rhythm it can drop the blood pressure so much that we pass out. Fast heart rhythms leading to syncope can be dangerous and are likely to need definitive treatment. That treatment may just be simple medication but ranges up to more invasive interventions undertaken by a specialist ‘electrical cardiologist’ called an Electrophysiologist.
We usually investigate blackouts with an ECG, an echocardiogram and a 24 tape of the heart to try and pick up abnormalities in the rhythm.