An ECG is a recording of the heart's electrical activity. Electrode patches are attached to the skin to measure the electrical impulses given off by the heart. It is not painful and takes about ten minutes. The result is a trace that can be read by a doctor. It can give information about risk of heart rhythm disturbance - such as the length of the QT interval.

An ECG done when resting may be normal even when heart problems are present. During an exercise ECG the heart is made to work harder and signs of heart disease may be unmasked. This test involves walking on a treadmill while the heart is monitored. The treadmill gets faster with time but can be stopped at any time. This test is supervised and interpreted by a doctor. The test is helpful to detect many forms of inherited heart disease, especially long QT syndrome and CPVT (catecholaminergic polymorphic ventricular tachycardia). These conditions can sometimes cause sudden collapse and sudden death in young people, and are difficult to diagnose - the exercise test can help.

Echocardiography is also referred to as cardiac ultrasound. This test is performed by a specially trained technician. It is a test that uses high frequency sound waves to generate pictures of the heart. During the test, the patient will generally lie on their back; gel is applied to their skin to increase the conductivity of the ultrasound waves. A technician then moves the small, plastic transducer over the chest. The test is painless and can take from 10 minutes to an hour. The machine then analyses the information and develops images of your child's heart. These images are seen on a monitor. This is referred to as an echocardiogram. Echocardiography can help in the diagnosis of many heart problems including hypertrophic cardiomyopathy or dilated cardiomyopathy.

The heart rate is controlled by a complex electrical system within the heart muscle which drives it to go faster when you exert yourself and slower when you rest. A number of conditions can affect the heart rate or rhythm. Heart rate simply refers to how fast the heart is beating. Heart rhythm refers to the electrical source that is driving the heart rate and whether or not it is regular or irregular. Some common terms Sinus rhythm is the normal rhythm Arrhythmia means abnormal rhythm Fibrillation means irregular rhythm or quivering of one part of the heart Bradycardia means slow heart rate Tachycardia means fast heart rate Paroxysmal means the arrhythmia comes and goes Tachycardia The most common of these in inherited heart disease is ventricular tachycardia. The usual presenting symptom is sudden collapse with loss of consciousness, particularly during or after exercise and also at night, when there may also be a seizure (fit). These can usually be prevented with regular medication such as a beta blocker. Sometimes a defibrillator pacemaker is needed. Bradycardia The most common form of this is called heart block. This is because messages from the electrical generator of the heart don't get through efficiently to the rest of the heart and hence it goes very slowly or can pause. Symptoms of the heart going too slowly include feeling tired, breathless or fainting. Tests Tests to diagnose what sort of arrhythmia is present include: an electrocardiogram (ECG). This trace of the heart's electrical activity gives the diagnosis of the source of the arrhythmia. This is often normal at rest and more extensive testing is needed to try and catch the arrhythmia especially if it is intermittent. an Ambulatory ECG. This can be performed with a Holter monitor which monitors the heart for rhythm abnormalities during normal activity for an uninterrupted 24-hour period. During the test, electrodes attached to the chest are connected to a portable recorder - about the size of a paperback book - that's attached to a belt or hung from a shoulder strap. Treatment Most treatments for tachycardias consist of medication to stop the abnormal rhythm or make it slower if and when it occurs. If bradycardia is diagnosed, a pacemaker may be fitted. This requires a small operation where a battery powered device is placed under the skin with wires that lead to the heart and provide it with electrical stimulation to prevent it from going too slowly.

In some forms of inherited heart diseases, genetic tests can be helpful when trying to identify which family members may be at risk of developing or carrying the condition. Testing for a range of cardiac inherited conditions is available, including Long QT syndrome (LQTS) and Hypertrophic Cardiomyopathy (HCM). Genetic testing involves a blood or saliva test, from which the lab extracts DNA. The lab looks at the genes linked to the condition suspected. The DNA from the first family member to be tested has to undergo a sequencing of the genes - in effect looking for spelling errors in a number of genes. The test is highly specialised and time consuming. In 2023 this can take up to 3 months. Once a genetic variant has been identified, in one or more genes, these can be looked for in the other family members. These tests can take between 6 weeks to 3 months. Each person having the test must be counselled carefully first, by a specialist or clinical geneticist or associate, and the patient must give their written informed consents. GPs and patients themselves may not order such tests, however GPs can refer their patients and families to the service for evaluation if there is a strong family history of cardiac inherited disease or young sudden deaths that appear to run in the family.