CARDIOLOGY
mode and Doppler evaluation should be performed
to evaluate the heart correctly. A full description of the
echocardiographic evaluations is beyond the scope
of this article.
the ventricles contract prematurely and the chamber
is not yet filled with blood - thus there is no bolus of
blood being pushed into the arterial system and thus
no pulse.
Large breed dogs are also predisposed to developing
pericardial effusion. These dogs however have good
body condition as it is not a chronic disease. In these
patients the heart rate may be rapid, but is regular and
there is no pulse deficit. Auscultation reveals softer
heart sounds.
The right heart is compromised first as the myocardium is thinner and thus these animals develop ascites. The radiographs will also show cardiomegaly
and careful evaluation is required to differentiate from
DCM. Ultimately ultrasound is required to confirm a
diagnosis.
The following criteria are used to make a diagnosis
of DCM
• Left ventricular dilation (especially in systole).
There are breed and weight tables for normal values.
• Depressed systolic function. Measurement of
fractional shortening and ejection fractions. Fractional shortening of less than 20-25%. Fractional
shortening does vary slightly between different breeds and there are tables available listing
the expected fractional shortening for different
breeds. Echocardiography of healthy Dobermans
recently found that the average fractional shortening was 26% using a short axis view, and 22.5%
using a long axis view. In other breeds a fractional
shortening of 25% or less in the short axis view is
considered abnormal. This either indicates that a
large percentage of healthy Dobermans have occult DCM or that the Doberman heart at baseline
is not comparable to that of most breeds.
• Left ventricular sphericity. A ratio of less than 1.65
• Left or bi-atrial enlargement.
• Increased E point to septal separation (EPSS)
>6.5mm.
• Arrhythmias such as atrial fibrillation and ventricular arrhythmias. Atrial fibrillation more common
in Irish Wolf Hounds and ventricular arrhythmias
more common in Dobermans and Boxers.
Holter monitors can be used to look of sub-clinical
myocardial disease which may present with episodic
arrhythmias.
Diagnosis of DCM
Radiographic findings in dogs with clinical DCM include cardiomegaly, venous congestion, prominent
left atrium, pulmonary oedema, pleural effusion and
sometimes ascites.
Treatment of DCM
When treating a patient with DCM we need to address
the underlying myocardial dysfunction, the harmful
counter regulatory mechanisms, pulmonary oedema,
arrhythmias, ascites and possible pleural effusion.
Supplementation with taurine, carnitine and free fatty
acids can also be considered.
Echocardiography is required to appreciate increased
chamber size and myocardial failure. It must also be
borne in mind the DCM is not the only cause of increased chamber size and myocardial failure. Doppler echocardiography is required to exclude some
acquired and congenital heart diseases that result in
ventricular dilation and reduced myocardial function.
For example patent ductus arteriosus results in volume over load of the left heart with ventricular dilation. Other differentials include tachycardia induced
cardiomyopathy, doxorubicin induced cardiac damage, taurine/carnitine deficiency and systemic diseases such as hypothyroidism.
Before starting a patient on treatment it must be borne
in mind that the median survival time from diagnosis is
about 19 weeks. The best single variable for assessing
prognosis is the left ventricular diameter at end systole. Other variables negatively associated with survival
include the following
• Presence of pulmonary oedema
• Presence of ventricular premature complexes
• Higher plasma creatinine levels
• Lower plasma protein
• Great Dane breed.
The echocardiogram should be carried out in lateral
recumbency according to the standard views. 2D, M-
Standard therapy includes an Angiotensin converting
enzyme inhibitors (ACE inhibitor), Pimobendan and
furosemide.
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