Hi friend, Welcome to Health Care Magic Standard ECG records the electrical activity of the heart, for a few seconds. It can detect the arrhythmia occurring during that time only. If the episode occurs randomly or precipitated by a specific activity like exercise, one needs Holter or event monitor. Holter records for days; Event monitor for weeks / Holter records continuously / Event monitor only at certain times . Anaemia / Anxiety / Alcohol / Tobacco (smoking) / Caffeine (too much tea, coffee, cola) / Fever / Infection / Pain / Stress / Thyroid / Vitamin D, calcium, magnesium / Medicines like Phenylephrine used for ‘cold’; Salbutamol used for asthma and so on - may be responsible.... / Illicit ‘drugs’ like Amphetamine are notorious to cause abnormal beats / At times, abnormal nerve paths in the heart (bypass tracts) or disease of the conduction system may be responsible! Take care Wishing speedy recovery God bless Good luck