Heart Defects

Canine Congenital Heart Disease 
http://www.tctc.com/~maplerg/sas-.htm

Cardiomyopathy
http://www.flourishingfairies.co.za/Cardiomyopathy.htm

Heart disease
http://www.heartydog.co.uk/index.shtml

Acquired Heart Diseases
http://www.ah.novartis.com/cab/en/dog_heart_failures.shtml

Dog Heart Disease
http://pethealth.petwellbeing.com/wiki/Dog_Heart_Disease