Palpitations — the sensation of the heart racing, thumping or skipping — are extremely common, and most of the time they are not dangerous. The difficulty is that they are intermittent, so the challenge is catching the rhythm while the symptom is actually happening.

That is what the monitoring tests are for. A standard ECG records about ten seconds. A Holter monitor records continuously for a day or more. Longer-term monitors extend that further when symptoms are infrequent.

Blackouts and near-blackouts are assessed differently and more urgently, because the question there is whether the heart is responsible at all.

What to expect

For a Holter monitor, several small electrodes are stuck to the chest and connected to a small recorder you wear under your clothes.
You go about your normal day and keep a short diary of any symptoms and when they happened.
The recorder is returned to the rooms afterwards and the recording is analysed against your diary.