There is 1 reason to lose consciousness when being choked - you are not getting enough oxygen to your brain. Either your airway is cut off & you eventually pass out due to lack of oxygen to the lungs and then the brain, you can breath but your carotid arteries are blocked limiting blood and therefore oxygen from the lungs to the brain, or a combo of both. Some people can adapt and live with both carotid arteries closed off by plaques. Blood gets to their brain through the vertebral arteries. Heart issues are triggered by the airway being cutoff and a lack of oxygen in the blood going to the heart muscle, by a sympathetic (adrenaline) surge increasing oxygen demand on the heart which the heart can no longer meet, or a combo of both.