I can feel my heart racing and thumping, and the rate is irregular. Am I having a heart attack?
Heart palpitations are the uncomfortable feelings when you feel that your heartbeat becomes noticeable. Each onset could last seconds, minutes or longer. They may feel alarming, but do not always reflect a serious heart condition.
Symptoms of heart palpitations:
Fluttering in the chest
Pounding heartbeat
Skipped or extra beats
Chest discomfort
Shortness of breath
Light-headedness
Dizziness
Possible causes/triggers include:
Strenuous exercise
Lack of sleep
Stress and Anxiety
Acid reflux
Panic attack
Certain medication
Alcohol, caffeinated drinks and nicotine
Heart palpitations can also be caused by iron deficiency anaemia, an overactive thyroid (hyperthyroidism) or a heart rhythm problem (arrhythmia).
In Traditional Chinese Medicine, heart palpitation is “心悸” (xin1 ji4). There are at least five causes and seven symptoms of xin1 ji4, and chest pain (angina) should be included in the differential diagnosis of heart palpitations. The many causes include “久病体虚，劳累过度，耗伤气血，心神失养” which is loosely translated as “weakness due to long illnesses, prolonged strenuous activities/lifestyle, deficiency of energy and blood, and impaired nourishment of the heart“.
Consult a doctor if you have heart palpitations and:
they keep recurring or they are getting worse
they last longer than a few minutes
you have a heart condition or a history of heart problems
you have family members with medical conditions of the heart
Although heart palpitations are typically harmless and can resolve on their own even without treatment, please do not ignore your symptoms or self-medicate. You might require an electrocardiogram (ECG) to help find out the real cause of your discomfort.
References:
The National Health Service (NHS)