DILATED CARDIAC MYOPATHY :- A SILENT KILLER
Dr. Ankita Kumari1, Dr.Sarjna Meena2,Dr.Priyanka3,Dr.Jyoti Pahariya3
Department of Veterinary Medicine, Post Graduate Institute of Veterinary Education and Research, Jaipur
RUVAS ,Jobner
ABSTRACT
Dilated cardiac myopathy is one of the most common acquired cardiac disorder in canines. Although can occur at any age but it is most common in dogs of age ranging from 4-8yrs. Large sized canine breeds(Great dane,German shepherd, Labrador, Doberman) are more predisposed to DCM as compared to smaller breeds. The condition affects the heart so significantly that heart is unable to perform its normal pumping of blood which leads to circulatory failure. As a result there is considerable damage of other organs like Lungs , Kidney and Liver. The signs shown by the animals are of heart failure which include exercise intolerance , dyspnoea, ascites etc. The most important systemic disturbance and perhaps the reason behind the severity of the disease is high Blood pressure(hypertension).Most cases of DCM have already been progressed to an irreversible stage before animal starts showing clinical signs ,thus the term SILENT KILLER. The disease can be diagnosed with the help of radiography, echocardiography and on the basis of clinical signs. The disease is reversible if it is diagnosed in its early phase . Treatment regimen targets correction of the high bp and removal of excess fluid accumulated in body along with it, the drugs that promote the contractility power of myocardium(ionotropic action) are also used.
KEYWORDS:- DCM, myopathy, heart failure, hypertension, ionotropic
INTRODUCTION
Dilated cardiac myopathy is characterized by ventricular chamber enlargement and systolic dysfunction which often leads to congestive heart failure(Gough and Thomas,2010). It is a condition affecting the myocardium in which myocardium loses its contractility and heart is unable to pump sufficient blood in the body and thus cardiac output is reduced leading to heart failure. The disease has 2 forms based on whether the animal shows clinical signs or not.
Occult form:- This form is seen when there are no clinical signs of disease to be seen in the dog but the structural and functional changes in the heart and other organs have already started and can be seen in Xray and Echocardiography Overt form:- This is the commonly observed form of the disease characterized by exhibition of clinical signs along with the changes observed in the organs.
ETIO-PATHOGENESIS
Although most of the cases of dilated cardiac myopathy are of unknown etiology (idiopathic),but factors like heredietary and nutritional deficiency(taurine and carnitine) have also been proposed.
As the name myopathy indicates the disease starts with the weakening of the myocardium, as a result of which the heart is unable to pump blood in the circulation and thus cardiac output is reduced. The body tries to compensate for this reduced blood circulation by adaptations. These adaptations include activation of RAAS(renin angiotensin aldosterone system) by kidney which results in increase in peripheral resistance and blood pressure due to vasoconstriction. Since heart is unable to pump blood there is accumulation of blood in the atrium and ventricles and to accommodate it there is compensatory dilatation of heart chambers. In this way the myopathy slowly progresses to heart failure. There is accumulation of blood and fluid all over the body resulting in congestion which later causes ascites, oedema , haemothorax etc. Since organs like kidney lungs and liver are unable to get the blood supply,their functions are also hampered.
CLINICAL SIGNS
Although various clinical signs are seen but some of them are very common. According to Reddy et al ,2021, these are the clinical signs and physical examination findings:-
Exercise intolerance Abdominal distension
Coughing Tachycardia
Cardiac cachexia Ascites
Pedal oedema Wheezing sound
Syncope Crackles
Open mouth breathing Muffled heart sound
Cyanosis Systolic murmur
DIAGNOSIS
The gold standard test for diagnosis of DCM is radiography(Lateral chest X-ray) but it should be corelated with the clinical signs , history of the dog and echocardiography and biomarkers.
VHS – The vertebral heart score of DCM affected dog will be greater than 11
ECHOCARDIOGRAPHY- The chambers will be enlarged and wall thickness of ventricles will be increased. The most important diagnostic measurement is the ratio of left atrium diameter and aorta diameter:-LA/A0 will be greater than 1.6
BIOMARKER- The most important biomarker for identifying cardiac damage is NTproBNP whose level in DCM affected dog will be greater than 400 pmol/L
TREATMENT
PIMOBENDAN (Vasodilator and ionotropic action) – 0.5mg/kg PO OD
DIGOXIN – (ionotropic and chronotropic action) – 0.0025-0.003mg/kg PO BID
ENALAPRIL-(ACE inhibitor, Anti hypertensive)- 0.25-0.5 mg /kg PO BID
FUROSEMIDE-(Loop diuretic) – 2-4 mg/kg IV,IM BID
L-CARNITINE and TAURINE – Supplementation with these amino acids and compunds have resulted in early recovery and regaining of contracting capacity of myocardium.
SUPPORT THERAPY with multivitamins, fluids, liver tonics , haematinics etc wherever required.
REFERENCES
- Allworth, S. M., Church, D. B., Maddison, J. E., Einstein, R., Brennar, P., Anssein , N. A. and Mathews, R. 1995, Effect of enalapril in dogs with pacing induced heart failure. Am. J. Vet. Res. 56, 86-94.
- Atkins, C. E. 2007, Angiotensin Converting-Enzyme Inhibitors and the Kidney Proceedings, World Small Animal Veterinary Association World Congress Proceedings.
- Calvert, C. A. and John, B. 1986, Use of M-mode echocardiography in the diagnosis of congestive cardiomyopathy in Doberman pincers. J. Am. Vet. Med. Assoc. 189, 293-297
