Palpitation are feelings or sensations that your heart is pounding or racing. You can feel them in your chest, throat, or neck. You may experience an unpleasant awareness of your own heartbeat, that your heart is beating too fast, fluttering, pumping harder than usual, and/or feel like your heart skipped or stopped beats. The heart's rhythm may or may not be normal when palpitations occur.
The most common culprits of palpitations in otherwise healthy individuals are:
Anxiety, stress, panic attack, or fear
Caffeine intake
Nicotine intake
Cocaine or other illegal drugs
Diet pills
Exercise
Fever
Palpitations could however be an indication of an underlying condition, including:
Arrhythmia or abnormal heart rhythm (tachycardia is fast heart rhythm; bradycardia is slow heart rhythm)
Abnormal heart valve, such as mitral valve prolapse
Abnormal blood level of potassium (usually low potassium levels, such as after prolonged severe diarrhea, or due to potassium depletion by some drugs, including those used to treat asthma, high blood pressure, or heart problems
Overactive thyroid
Low level of oxygen in your blood
Palpitations that occur infrequently and last only a few seconds are usually benign and do not need medical evaluation. These are usually easily managed by the home care and lifestyle changes, including:
Lowering caffeine and nicotine intake. This will often reduce heart palpitations.
Reducing stress and anxiety. This can help prevent palpitations and help you better manage them when they occur.
Trying deep relaxation or breathing exercises (yoga for example).
Exercising regularly.
Quitting tobacco smoking.

If however you have a history of heart disease, or any of your 1st degree relatives does, and you are having frequent palpitations or palpitations that are getting worse over time, you are advised
to be seen by your doctor, especially if you are an athlete. He or she may suggest heart-monitoring tests (electrocardiogram or ECG) to check if your palpitations are caused by a more serious heart problem.

Alarming signs of serious conditions include:
Chest discomfort or pain
Fainting
Severe shortness of breath
Severe dizziness