Retrospective evaluation of hypertrophic cardiomyopathy in 68 dogs

Abstract

Background: There is a lack of clinical data on hypertrophic cardiomyopathy (HCM) in dogs.

Hypothesis/objectives: To investigate signalment, clinical signs, diagnostic findings, and survival in dogs with HCM.

Animals: Sixty-eight client-owned dogs.

Methods: Retrospective multicenter study. Medical records were searched between 2003 and 2015. The diagnosis of left ventricular (LV) hypertrophy was made by echocardiographic examination.

Results: Three hundred and forty-five dogs with LV hypertrophy were identified, of which 277 were excluded. The remaining 68 dogs were 0.3 to 14 years old and predominantly <10 kg (85%), and without a sex predilection. Twenty-four % were Shih Tzu and 24% terrier breeds. Most (80%) had a systolic heart murmur. Owner-determined exercise intolerance (37%) and syncope (18%) were most commonly reported signs. The majority (84%) of dogs had symmetrical LV hypertrophy, whereas asymmetrical septal and LV free wall hypertrophy was observed in 9% and 6% of dogs, respectively. Isolated basal interventricular septal hypertrophy was not observed. Commonly recorded were systolic anterior motion of the mitral valve (60%) and LV diastolic dysfunction (89% of dogs where diastolic function was evaluated). Six dogs died unexpectedly, and 3 developed congestive heart failure. Known survival times were between 1 day and 114 months after diagnosis.

Conclusions and clinical importance: Hypertrophic cardiomyopathy in dogs should be considered as a differential diagnosis if LV hypertrophy is identified. Small breed dogs are overrepresented, and it is uncommon for dogs with HCM to develop CHF although sudden death can occur.

Keywords: HCM; LV hypertrophy; canine; dynamic outflow tract obstruction; veterinary.

FIGURE 1

Age distribution of study dogs. The age numbers on the X‐axis represent ranges (eg, 1 indicates ≤1 year; 2 indicates >1 year and ≤2 years; 3 indicates >2 years and ≤3 years)

FIGURE 2

Body weight distribution of study dogs. The numbers on the X‐axis represent ranges (eg, 5 indicates ≤5 kg; 10 indicates >5 kg and ≤10 kg; 15 indicates >10 kg and ≤15 kg)

FIGURE 3

Echocardiographic images of an 8‐year old 8.6 kg female Cairn terrier with hypertrophic cardiomyopathy. Concentric left ventricular (LV) hypertrophy, increased systolic function, and abnormal transmitral flow indicating LV diastolic dysfunction are present. Systolic blood pressure was 140 mm Hg. (A) Right parasternal long‐axis 4‐chamber image. Thickness of the interventricular septum in diastole (IVS) was 15.3 mm (normalized 0.95; matched control dog 0.44) and of the left ventricular (LV) free wall (LVFW) 16.2 mm (normalized 0.98; matched control dog 0.46). Left ventricular dimension in diastole was 24.2 mm (normalized: 1.30; matched control dog 1.45). (B) Right‐parasternal short‐axis image recorded at the level of the papillary muscles. (C) LV M‐mode echocardiogram displaying increased LV systolic function. Segmental shortening fraction was 55% (matched control dog 37%). (D) Pulsed wave Doppler transmitral flow pattern displaying decreased velocity of early LV diastolic filling flow (E) and a ratio of E to late diastolic flow velocity (A) of 0.52 (matched control dog 1.48) indicating presence of mild LV diastolic dysfunction (delayed‐relaxation filling pattern)

FIGURE 4

Body weight‐normalized (allometrically scaled) end‐diastolic wall thickness measurements of the interventricular septum (IVS) and left ventricular free wall (LVFW) recorded from a right‐parasternal long‐axis 4‐chamber view and measured from 2‐dimensional still frames in matched control dogs (c) and study dogs (s). Individual data points and the mean are displayed. There was a significant difference between control and study dogs for both the IVS and the LVFW (all P < .001). The overlap between control and study dogs relates to both the presence of asymmetrical LV wall thickening in some dogs and the fact that measurements of only right‐parasternal long‐axis images (as opposed to both long‐axis and short‐axis images) are displayed. Both short and long‐axis images were considered in the diagnosis of HCM