What makes your dog’s heart tick? A dog’s four-chambered heart is a complex, synchronized network of electrical circuits that weaves through the cardiac muscle. The heart is the pump at the center of the circulatory system. This system delivers vital oxygen to the tissues in the body and carries wastes from the tissues back to the lungs to be exhaled. Problems within the circulatory system may involve abnormal: 1)blood flow (heard as a murmur), as in congenital defects and valve degeneration; 2) heart muscle function, termed cardiomyopathies; and 3) electrical signals in the heart muscle (e.g.: ventricular tachycardia), causing uncoordinated contractions of the heart. Indications that your dog may have a heart problem include: coughing, exercise intolerance, cold extremities, weakness, collapse, and/or changes in breathing patterns.