Hi friend, Welcome to Health Care Magic THE FIRST STEP IS TO SEE A CARDIOLOGIST It is advisable to have it investigated. The nerves of the heart may be diseased . There is a condition called Sick Sinus Syndrome – fast or slow rates at different times. At times, abnormal nerve paths in the heart (bypass tracts) are responsible! A thorough history and physical examination is the first step - ECG (Electrocardiogram / EKG) – Routine 12-lead – is part of clinical examination. If a routine ECG does not show, 24 to 48 hour ambulatory monitoring (HOLTER) is done to analyse and plan for further management. ECHOcardiogram is necessary to see the heart valves (Mitral Valve Prolapse) / heart muscle (Cardiomyopathy) and heart function (Ejection fraction, wall motion abnormality). TMT (Treadmill exercise ECG) is done to exclude Ischemia (reduced blood flow). LABORATORY work-up is routine - like blood counts, sugar, urea, electrolytes (potassium in particular), thyroid (over-active) and so on. Your Internist shall suggest based on the situation. There are advanced techniques of investigations of increasing complexity – Electro Physiological Studies (EPS) it resembles angio – a catheter is put inside the heart / electrical activity recorded / stimulation and suppression tests are carried out / suitable medicine tested and so on. Though the test is the gold standard, it is INVASIVE and has a risk (though minimal) and is not generally done unless there are compelling indications. This super-speciality expert is called ELECTRO-PHYSIOLOGIST. The treating doctor may suggest them depending on need, based on his assessment of the situation. Take care Wishing speedy recovery God bless Good luck