Hypothyroidism - A cause for dilated cardiomyopathy in dogs; four year study 2008-2011

Abstract

Aim : The study was carried out to understand the thyroid dysfunction and its association with dilated cardiomyopathy in dogs. Materials and Methods: The study was done at Teaching Veterinary Hospital, Bhoiguda, College of Veterinary Science, Hyderabad for four years, i.e., from 2008 to 2011. A total of 256 dogs of various breed, age and sex were presented with typical skin and coat abnormalities. Few were also exhibiting signs of low metabolic rate. Skin sample analysis was done to rule out the causes of dermatitis. Thyroid profile was estimated to diagnose hypothyroidism. Selected cases were also subjected for echocardiography to study the association of cardiomyopathy. Based on thyroid profile, hypothyroid dogs were treated with levothyroxine @20mcg/kg wt, once daily, orally on empty stomach and dilated cardiomyopathy (DCM) associated patients were additionally supplemented with enalapril @0.5 mg/kg, twice daily, orally for 6 months. The hemato biochemical and echocardiographic aspects are discussed. Results: The classical signs that were recorded in almost all the thyroid dysfunction dogs (231) were bilateral alopecia, rat tail and pigmentation and whereas, dyspnoea at rest, exercise intolerance, obesity, pale mucosae and corneal lipidosis were the significant low metabolic rate signs noticed in 42 dogs. However, syncope and seizures were also recorded in 31 of these hypothyroid dogs. Echocardiographic evaluation revealed significantly (P<0.01) increased LVEDd and LVEDs along with decreased IVS and LVPW both at systole and diastole among 33 dogs. Normocytic, normochromic and non-regenerative anemia and significantly (P<0.05) low T3, fT4, tT4 along with elevated serum cholesterol, triglycerides, TSH, CKMB, LDH and ALP were the hemato -biochemical findings among these dogs. After the initiation of therapy, improvement in clinical signs was noticed from day 7 and complete clinical recovery by the end of therapy. However, a non significant improvement was recorded with respect to left ventricle dimensions. Conclusions: From the present study it may be concluded that thyroid dysfunction is presented by manifestations of two different systems, i.e., skin and coat and metabolic abnormalities. Echocardiography is the more sensitive diagnostic aid to ascertain the involvement of cardiovascular system and to assess the therapeutic response. Further, supplementation of ACE inhibitors along with the specific thyroid supplements helps to resolve the disorder.

Characterization of Cardiac Diseases in Dogs Prevalent in Indian Conditions

“…There was reduced contractility of chambers manifested by low EF% (30.11±3.23%) and FS% (13.43 ±1.62%). Present findings were in agreement with earlier studies Karlapudi et al (2012)…”

Review of canine dilated cardiomyopathy in the wake of diet-associated concerns

“…These conditions can contribute to an enlarged left atrium and ventricle and can resemble a DCM phenotype ( Saunders and Gordon, 2015 ). The FDA Vet-LIRN report also stated 9% ( n = 18) had concurrent hypothyroidism, which has been known to increase the risk of cardiovascular disease ( Karlapudi et al, 2012 ). Lastly, 8% ( n = 17) of the dogs had a concurrent diagnosis of tick-borne diseases, such as Lyme or Anaplasmosis.…”

“…Historically, dilated cardiomyopathy ( DCM ) has been considered to be primarily an inherited disease, with higher prevalence in specific dog breeds ( Dukes-McEwan et al, 2003 ; Sammarco, 2008 ). However, other causes of DCM include specific nutrient deficiencies ( Freeman et al, 2001 ; Backus et al, 2003 ) and concurrent diseases, such as endocrine ( Karlapudi et al, 2012 ; Janus et al, 2014 ), myocarditis, and chronic tachycardia ( Calvert et al, 1997 ). Recently, there has been concern regarding the relationship of diets with specific characteristics, such as, but not limited to, grain-free diets and those containing legumes, novel protein diets, and those produced by small manufacturers to DCM in dogs ( Freeman et al, 2018 ); however, no definitive link has been established at this time.…”

The prevalence of dilated cardiomyopathy in the Weimaraner dog breed

“…The effect of hypothyroidism as a metabolic aetiology for secondary cardiomyopathy was also described as another possible causative factor in the development of DCM (Karlapudi et al 2012). However, in Doberman Pinchers, the role of hypothyroidism in the aetiology or progression of DCM was not confirmed (Beier et al 2015).…”

“…It has been suggested that hypothyroidism can play a role in the development of DCM in dogs. In some studies, the therapy of hypothyroidism led to an increased fraction shortening and ejection fraction of the left ventricle (Tidholm et al 2001;Karlapudi et al 2012).…”