<unk>  in an ECG (arrows)<unk> s occur in healthy persons of any age, but are more prevalent in the elderly and in men. In a very significant proportion of people they occur spontaneously with no known cause. Some possible underlying causes of<unk> s include: * Adrenaline excess * High blood calcium * Cardiomyopathy, hypertrophic or dilated * Certain medicines such as tricyclic antidepressants * Chemical (electrolyte) problems in the blood (for example hypokalemia, which can occur in those taking diuretics ("water pills") and hypomagnesaemia). * Contact with the carina (trachea/bronchi) when performing medical suctioning stimulates vagus nerve * Drugs such as: * Alcohol * Caffeine * Cocaine * Nicotine * Theobromine * Myocardial infarction * Hypercapnia (CO2 poisoning) * Hypertension (high blood pressure) * Hypoxia * Lack of sleep/exhaustion * Mitral valve prolapse * Myocardial contusion * Myocarditis * Sarcoidosis * Smoking * Stress
Premature ventricular contraction
Premature atrial contraction
Benign early repolarization
Pre-excitation syndrome
Ectopic beat
Ectopic pacemaker
Premature junctional contraction
Drug-induced QT prolongation