Lifespan and Causes of Death in the Irish Wolfhound - Vetsuisse ...

mitochondrial hyperplasia, disruption of myofibrils and Z band thickening. All of these
features (except Z band thickening) can also be found in the heart muscle of clinically
healthy dogs, although to a much smaller degree. Mitochondrial hyperplasia and
disruption of myofibrils were described as having a similar extent in 46 sections from
eight DCM cases in giant dogs. These findings are not specific for DCM, however,
but rather reflect long standing ventricular hypertrophy with subsequent congestive
heart failure (Bishop 1986).
A more recent study found that giant breed DCM is characterised by thin attenuated
wavy myocardial fibres as opposed to the “fatty infiltration degenerative” type seen in
Doberman Pinschers and Boxers (Tidholm and Jonsson 2005).
Additionally, some animals seem to exhibit high-grade panarteriitis of the larger
cardiac arteries, especially in the left ventricular wall and the interventricular septum,
leading to particular obstruction of the lumen (Broschk 2004).
3.3.1.2 Symptoms
In Wolfhounds, DCM goes through a long subclinical stage that is mainly
characterised by atrial fibrillation (AF) as mentioned above. Contrary to “lone atrial
fibrillation” in humans, this seems to be an objective risk factor for the eventual
development of DCM to the point that it can be said that Wolfhounds with AF can be
considered to likely be in a stage of “occult DCM” (Koch, Pedersen et al. 1996;
Vollmar 1996; Brownlie and Cobb 1999).
Weight loss, combined with extreme tachycardia, dyspnoea and ascites are reported
to be the typical symptoms of clinically manifest Wolfhound DCM. These and other
signs of progressive cardiac failure, such as exercise intolerance, coughing and
general apathy are usually indicative of an advanced stage of the disease (Brownlie
and Cobb 1999).
3.3.1.3 Diagnosis
While fully developed clinical DCM is comparably easy to diagnose, it is important for
optimal treatment to catch the disease in an early stage. On auscultation, low-pitched
protodiastolic gallop sounds are indicative of DCM, as are pulse deficits, absolute
arrhythmia and tachyarrhythmia. In about half of the dogs with DCM, a soft
regurgitant systolic murmur can also be heard (Fox, Sisson et al. 1999).
Electrocardiographically, AF is the most consistent ECG sign found in Wolfhounds
with DCM. Other abnormities may include ventricular and supraventricular premature
contractions (VPC’s and SVPC’s), P mitrale and 1 st and 2 nd degree AV-block.
Bigeminal rhythm and paroxysmal tachycardia can also be observed. It is also
possible for a Wolfhound with DCM to have an entirely normal ECG, although this
must be considered rare (Brownlie 1991; Harpster 1994; Brownlie and Cobb 1999;
Vollmar 2000).
Echocardiography is the gold standard for the diagnosis of canine DCM (Fox, Sisson
et al. 1999). Reference values for healthy Wolfhounds and exact values for
diagnostic parameters were published in 1999 (Vollmar 1999 a; Vollmar 1999 b).
Parameters with highly significant variability between the groups of normal dogs,
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