Dilated Cardiomyopathy, also known as an enlarged heart, is a heart muscle disease where the chambers of the heart become enlarged leading to a the heart that does not function properly. When the lower chamber of the heart becomes enlarged it is unable to pump blood effectively to the lungs which leads to a build up of fluid around the lungs, the heart becomes overloaded and leads to Congestive Heart Failure (CHF). Although the exact "cause" of DCM is unknown, in general, DCM appears to be caused by either a nutritional deficit (Nutritionally Mediated DCM) or a genetic susceptibility to the disease. Frequently with Nutritionally Mediated DCM, blood tests show low blood levels of the amino acids taurine and carnitine which are vital to keeping heart muscle cells strong. Low levels of these amino acids have been implicated in DCM in dogs, cats and humans. In other cases, dogs eating grain-free high legume kibble have developed DCM but have not have low blood taurine levels.
Symptoms of Dilated Cardio Myopathy in dogs that an owner may notice include heavy breathing in the absence of exercise, exercise intolerance, lack of appetite, coughing, bloated appearance, and fainting. Other symptoms may be found by a veterinarian during a complete physical exam, but a veterinary cardiologist will make a definitive diagnosis based on the results of an echocardiograph. Treatment of DCM, regardless of whether it is Nutritionally Mediated DCM or solely based on genetics, includes medications that help the heart to function, medications to control symptoms and diuretics to reduce the build up of fluid in the chest. Dietary supplementation with taurine and carnitine can help with either type of DCM, but with Nutritionally Mediated DCM, it has along with the other medications mentioned above, been shown to reverse the disease with some owners being able to reduce the amount of medication they are giving their dogs and some dogs returning to a close to normal life. The prognosis for dogs who do not respond favorably to supplementation and whose disease progresses, the prognosis is poor with life expectancy being around six to eighteen months.
If you are reading about Nutritionally Mediated Dilated Cardiomyopathy or you are speaking to your vet you may hear them use different terms for the disease. They describe different different aspects of the disease, but are not mutually exclusive. Nutritionally Mediated DCM is more of a blanket term for DCM that is caused or related to what the dog is eating (or not eating). Taurine Deficient DCM is a term used for dogs with DCM that have low blood taurine levels. Taurine Responsive DCM is used for dogs whose DCM has improved when on taurine supplementation. A dog who is diagnosed with Taurine Deficient DCM whose heart improves on supplementation will also have Taurine Responsive DCM and of course since the DCM was caused by the food he ate, he will also have Nutritionally Mediated DCM. A dog who did not have a low initial taurine level but improves with taurine supplementation will have Taurine Responsive DCM but technically not Taurine Deficient DCM. Furthermore, a dog may test low for taurine and have Taurine Deficient DCM but not improve with supplementation so not have Taurine Responsive DCM.
If you are concerned that your dog may be at risk for taurine deficiency, please see your vet and have them send a blood sample to the UC Davis Veterinary School testing laboratory. Currently they charge $76 for taurine level analysis although you will need to pay for the blood draw and shipping.