The pacemaker will enable his heart to beat at a normal rate, it won't necessarily make him more alert or less drowsy unless that is caused by his heart. Does the temporary pacemaker have one or two pacing wires?
Pacemakers come in various types and can be programmed differently. The type of pacemaker fitted depends on:
a) what rhythm his heart is in - for total heart block he will have at least 2 'pacing wires' one in the right ventricle and one in the right atrium.
b) age of patient
c) lifestyle
d) preference of cardiologist or cardiac tech.
The pacemaker itself is usually put in the top of the chest and wires from it go to the heart.
With a very elderly patient you don't really want to put in a fancy pacemaker because you want it to last as long as possible, most pacemakers last at least 5 years, then the 'box' is changed but the wires are left in situ and attached to the new pacemaker.
Reprogramming a pacemaker can extend the life of it so for a 90 year old, realistically you only want to fit one pacemaker.
Lifestyle - there is a lot you can program, basic program for complete heart block the wire in the atria will sense the atrial contraction and basically give the ventricle a kick to make it beat. The heart rate is determined by the natural atrial rate.
Different settings can be set for night time and for exercise, generally you want the heart rate lower when you are asleep and if the heart (or part of it) isn't controlling this then the program will tell the pacemaker to take over.
To program/reprogram the pacemaker a programmer is used, it basically involves a part that is an electromagnet and that sits over the pacemaker itself.
The second part often looks like a laptop computer and the tech will be able to change settings.
For most people once the program is set they just come back for check ups every 6 months or every year - depends on the centre.
If there are any problems the tech can change the settings so if there are any problems don't forget to note symptoms and let the tech know at check ups.