Study on prevalence and clinical features of dilated cardiomyopathy in dogs in Mhow and Indore

Introduction

Canine cardiac diseases are common, and complex. Any cardiac abnormality needs to be dealt with priority to avoid morbidity and mortality (Kumar et al., 2014) [6] . Dilated cardiomyopathy (DCM) is one of the most common acquired cardiovascular diseases of dogs, which is characterized by impaired myocardial contractility with dilation of the chambers of heart. The chambers of the heart increase in size and the muscles forming the walls of the heart become thinner, resulting in weakened contractions and poor pumping ability (Sisson, 2010) [11] . Cardiomegaly, as a consistent sign of heart disease, can be seen in cases of hypertrophic or dilated cardiomyopathy (Litster and Buchanan, 2000) [7] . Dilated cardiomyopathy is characterized by a weakened cardiac contractile force, dysfunction of the myocardium involving systolic and/or diastolic impairment, dilation of the ventricles, and the frequent presence of tachyarrhythmias. Several studies suggest that giant and large breed dogs are more predisposed to DCM. Sex has also been identified as a predisposing factor for dilated cardiomyopathy, with male dogs showing a greater incidence of the disease. DCM in dogs is characterized by a prolonged preclinical stage, and dogs with DCM are difficult to diagnose in the preclinical stage. Once clinical signs develop, the period prior to referral is typically brief, and the associated survival outcomes are generally unfavourable.

In routine clinical settings, outside of organized breedscreening programs, dogs with dilated cardiomyopathy are most often identified only after they begin to show clinical signs or when abnormalities are detected during physical examination. Therefore, improved awareness of breed predispositions, characteristic clinical manifestations and key diagnostic indicators obtained through electrocardiography, radiography and echocardiography can facilitate earlier detection of this condition, which is typically associated with a brief symptomatic period. Considering the background study, the present study was planned to study the prevalence and clinical features of DCM in dogs in Mhow and Indore.

Materials and Methods

The present study was carried out during a period from July 2025 to December 2025 in the Department of Veterinary Medicine, College of Veterinary Science and Animal Husbandry, Mhow, Madhya Pradesh, India. A total of 1829 dog cases were presented and 147 dogs were suspected with clinical signs involving exercise intolerance, Laboured breathing, tachpnoea, limb oedema, ascites, coughing and lethargy for various cardiac diseases. Then these suspected cases were screened further for confirmatory diagnosis with electrocardiography (Using 3-channel ECG machine Hygeia 3SV), radiography (Using MedRay 40) and echocardiography (using Wipro GE LOGIQ 5 colour Doppler ultrasound machine). ECG was performed using the standard limb leads and chest lead at 25 mm/s paper speed and interpreted as per the guidelines by Tilley et al. (2008) [15] . Thoracic radiograph was taken in right lateral recumbency and was based on the general principles outlined by Buchanan and Bucheler (1995) [2] and then Vertebral heart score is measured. The vertebral heart score more than 10.5 was considered for cardiomegaly. The M-Mode echocardiography was performed with a frequency range between 5.0 to 8.0 MHz as per standard protocols (Tilley et al., 2008) [15] . All the information related to age, sex, breed and clinical signs was collected. The vital parameters were evaluated by one-way ANOVA as per the standard procedure outlined by Snedecor and Cochran (1994) [12] .

Results

A total of 1829 dog cases were presented at the Veterinary Clinical Complex (VCC), College of Veterinary Science and A.H., Mhow and Indore. The prevalence of DCM was found to be 0.82%. The age-wise prevalence was found to be higher in dogs over 8 years of age (1.27%), followed by the age group of 5-8 years (0.95%) and then no positive case of DCM in the age group of 0-4 years (Table 01). The sex wise prevalence was recorded as 0.98% in males and 0.62% in females (Table 02). Among the total dogs, the breed-wise distribution indicated that Labrador retriever was more prone to DCM (0.27%), followed by German shepherd (0.22%), Golden retriever (0.11%) and Indian spitz (0.11%), Beagle (0.05%) and Doberman pinscher (0.05%) (Table 03). On clinical examination, the history of lethargy was recorded in 93.33% of cases followed by exercise intolerance (86.66%), inappetence (66.66%), laboured breathing (60%), weight loss (40%), tachypnoea (26.66%), coughing (20%), ascites (13.33%) and limb oedema (6.66%) (Table 04) (figure 123).

The mean value of rectal temperature (°F) was 101.81 ± 0.11, which was within the normal range. The mean value of heart rate (bpm) was 127.00 ± 4.07, which was higher than the normal physiological range. The mean values of pulse rate (bpm) and respiration rate were 123.75 ± 4.06 and 32.50 ± 1.92, respectively, which were higher than the normal physiological range (Table 05).

Discussion

In the present study the overall prevalence was found to be 0.82%, which aligns with the previous reports of overall prevalence of DCM between 0.5-1.1% as reported by Martin et al. (2009) [8] . Thirunavukkarasu (2019) also reported that the DCM in dogs is below 1%, which agrees with the present study. The prevalence of DCM in dogs was higher in age group of more than eight years, that aligns with the findings of Wess et al. (2010) [19] , whose study revealed that out of the positive cases, 88.7% were above six years of age, while 22.4% were identified in dogs between two and six years, with the condition being least frequent (3.3%) in those younger than two years. While Ben (2010) found increased occurrence in middle aged dogs. Among the confirmed cases, males were more susceptible to DCM than females. Male predominance was suggested by Serfass et al. (2006) [10] . However, Wess et al. (2010) [19] reported equal percentage of both male and female dogs affected. Among the different breeds, a higher prevalence of DCM was observed in Labrador Retriever followed by German shephard and golden retriever. The observation of higher incidence in Labrador Retriever is in agreement with Pai 2009 [9] and Thangapandiyan et al. (2016) [14] . Most of the animals presented with this disease were pure pedigree dogs, this observation was similar to that made by Dukes-McEwan et al. (2003) [4] . The prevalence of DCM in certain breeds like Deerhounds, Dobermans, Irish Wolfhounds, Great Danes and Boxers was high in the other countries. The differences in the prevalence of breeds can be due to more population of certain breed in particular area.

Clinically DCM affected dogs showed several clinical signs such as exercise intolerance, lethargy, laboured breathing, coughing, ascites, tachypnoea and limb oedema. The similar clinical signs were observed by Van et al. (1981) [16] and Varshney et al. (2011) [17] . The onset of signs such as exercise intolerance, fainting episodes, coughing and vomiting is commonly associated with left-sided cardiac failure, while abdominal distension or the development of ascites is more indicative of right-sided heart failure (Ettinger and Feldman, 2005) [5] . Non significant changes were observed in rectal temperature. The similar findings were also observed by DeFransesco (2002) [3] . Increased heart rate, pulse rate and respiration rate was observed in the initial presentation of dogs affected with DCM, Similar findings were observed by Sreenesh (2015) [13] . Increased heart rate is may be to compensate for the reduction stroke volume, the body activates the sympathetic nervous system, resulting in an increased heart rate, the pulse deficit can be because all heartbeats may not produce palpable pulses, leading to pulse deficits (Ettinger and Feldman, 2005) [5] . The increased respiration rate observed can be due to reduction in congestion and pulmonary oedema, these findings align with those reported by Pai (2009) [9] .

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