Hello, I understand your concerns but there is no reason to worry. These heavy heartbeats are a result of anxiety, tension or stress at work, home or personally. It is a bit of psychological assessment before you proceed further. Some people feel it while lying down .If there is an underlying medical condition; it has to be assessed by your doctor and treat it according to the cause. Hence you should give a complete history, physical examination, Pulse, BP, heart rate monitoring and other systemic examination that might play a contributing factor to produce these kinds of instances. It would best if you could get an ECG monitoring and check your thyroid levels in your body. This can also occur due to stress and anxiety and this can relive by yoga or meditation. I would suggest you to get an ECG done and consult your cardiologist with the reports. Thank you.