DH had this after he was real sick(real, real sick, in the hospital sick.) WHen he went in his Heart rate was normal, but by the 4-5th day his heart rate was 25 and the CCU nurses had to keep waking him up. His skin was grey and he was confused by the time they got him down to the cardiac cath lab. They didn't really know what was going on. The cardiac cath revealed something wrong with the sinus node, the main electrical stimulator in the heart. It was not functioning anywhere near normal and the backup system was valiantly trying to keep his heart going. THey immediately put in a pacemake and he came out of the cardiac cath pink, talkative, feeling great and ready for lunch. It was like a miracle!
DH recovered and he still has his pacemaker. It paces about 40% of the time, which is just fine with us. His heart rate is normal now and he really doesn't have any problems with his heart, although he goes to see the cardiologist about every 4 months to check on the pacemaker and touch base with the doctor. Otherwise, the pacemaker has been a non-issue entirely.
Best of luck to your husband. I'm sure the cardiologist will do a thorough workup. I'm glad your GP decided to send him. I think in this situation it's better to seek a specialist sooner than later.