How sweet you are! I just love little chihuahuas. We had little Pixie for just about 2.5 years. Then we had little Patsy and she lived past 17 years. Next we had little Mitzi and she lived over 12 years. They were cute little reddish brown colors - all three of them. They were such sweethearts. If I could handle more than one doggie at a time, I would love to have another chihuahua.
Whispersmom has given you some good info.
All I found was this:
Heart murmur
Heart murmurs are relatively uncommon in Chihuahuas and even those that have one usually have the functional type. As in people, that means they can be as active and athletic as they want and live long, normal lives.
http://www.dummies.com/WileyCDA/Dumm...e/id-2062.html