There are interesting things that can occur with pacemakers and 3rd degree heart block.
I had a pacer placed after my aneurysm surgery when I developed complete block (3rd degree). It was a standard R ventricle lead pacer that had a max pacing rate of 150. On my bike at that time I would exceed that heart rate at times and my rate would suddenly drop to 100. So I would go from 160 to 100 suddenly. Not fun. There is a phenomenon called pacemaker Wankebach which causes this. Basically if the heart rate exceeds the max pacemaker rate the pacer suddenly drops some of the beats. Since the pacer was electronically constrained to 150 max I had it removed for a new pacer that would go to 180. Problem solved.
Problem two. Most pacers are set up with a lead in the right atrium to pick up the normal atrial signal and then there is a lead to the right ventricle to cause the ventricle to contract. The ventricular contraction goes from the right to left ventricle. This is not physiological. Normally there are two pathways that go to the right and left ventricles so that they contract very close together. With right ventricular pacing there is a delay for the left to contract.
A number of years ago pacers were placed with leads in both the right and left ventricles in people who had heart failure. The ventricular contractions could be altered and the heart could be made more efficient. This was named Cardiac Resynchronization treatment.
https://www.medtronic.com/us-en/healthcare-professionals/products/cardiac-rhythm/crt-systems.htmlAnyway to make a long story shorter just pacing the right ventricle is not optimal in the long run. I had the usual right ventricular pacing for about six years when I realized that my cardiac output was slowly declining. I looked into it and found that in patients that were not in failure that there was evidence that biventricular pacing was superior to right ventricular pacing. One of the first studies came out of Hong Kong on this topic.
I spoke with my electrophysiologist and he agreed to place a new biventricular pacer with a lead added to the left ventricle.
My ejection fraction improved from 45% (it had started 6 years earlier at around 55%+) back to 55-60%.
I have never gotten a straight answer why biventricular pacers are not used routinely with complete block. It may be that at least right now primarily electrophysiologists are more comfortable in placing the left lead which is a bit tricky since it is placed in the coronary sinus which is a giant vein. Other leads are screwed into the heart muscle. Non electrophysiologist cardiologists are not generally comfortable placing this type of lead. It may be the cost is more. It has not hit prime type yet. Or other reasons that I am not aware of.
So those of you who have or will have long standing need for pacing due to complete heart block you may want to discuss this issue with your physicians to see what they have to say.