Hello. Welcome to HCM and thank you for your question. I understand your concern. Normal heart rate accepted in the worldwide population is from 60 to 100 heart beats per minute. In highly trained athletes and people that some time in their life were highly physically active, even heart rate in the 40s is acceptable and considered normal. Normally, heart rate, during a phisyologically and psychologically delicate procedure such as colonoscopy, tends to go higher and not remain in the 40s. The palpitation you are sensing is probably because of an occasional extrasystole (premature ventricular contraction - PVC) which is an ectopic heart beat, that comes from elsewhere in the cardiac muscle, not from the original pacemaker of the heart - the sinus node. These are almost always not worrisome events. This long-standing bradicardia if not accompanied by symptoms - dizziness, blurry vision, dark vision, near-fainting episodes etc. - then is probably nothing to worry about and no further treatment is warranted. However, I would recommend you to be put on a 24-hour rhythm monitor, to register the heart rate in a whole day, and see if there are even lower heart rate figures registered. If yes and if the extrasystoles result more than 10.000 in number, in the 24-hour registration, I suggest you to discuss with your cardiologist, about the possibility of implanting a definitive pacemaker. I hope this helps. Take care. My regards, Dr. Meriton