Case Studies

These case studies contain detailed information on the diagnostic and treatment process for each individual animal.

Asa

Case Background

Name: Asa
Age: 7 years
Sex: Male, Neutered
Breed: Domestic Shorthair

Clinical History

Please review Asa’s clinical history.

Asa has a history of chronic vomiting and a recent full body radiograph provided concern for cardiomegaly. There are no clinical signs at home suggestive of heart disease and cardiac auscultation is unremarkable. An ECG was recorded as part of his cardiovascular evaluation.    

ECG

View Asa’s electrocardiogram (black bar equals 1 second)
What abnormalities are present on this ECG?
Relevant Findings: The correct answer is sinus rhythm with ventricular pre-excitation (possibly related to an accessory pathway). The underlying rhythm is sinus rhythm. This is determined via calculation of the heart rate, determination of the cardiac rhythm, and inspection of the relationship of the P waves and QRS complexes. The average heart rate is 200 beats per minute. The rhythm is regular. There is a P wave for every QRS complex and a QRS complex for every P wave providing a diagnosis of sinus rhythm. The primary alterations with this ECG are the shortened PR interval, the abnormal morphology of the QRS complexes with a rapid upstroke (or delta wave) most easily appreciated in lead I (inset, black arrow), and the associated deviation of the mean electrical axis to 330 degrees (or -30 degrees). The shortened PR interval and delta wave suggest ventricular pre-excitation wherein an accessory pathway (bypass tract) enables supraventricular impulses to depolarize the ventricles without traversing the AV node. View an annotated image of Asa’s ECG highlighting the relevant findings.

 

Discussion & Treatment

 
Discussion:  It is unlikely the ECG alterations are related to the primary complaint of chronic vomiting. If the presumed accessory pathway is associated with an intermittent atrio-ventricular re-entry tachycardia, this could contribute to a tachycardia-induced cardiomyopathy. An echocardiogram is recommended to further investigate the ECG abnormalities and the radiographic impression of cardiomegaly. Treatment/management: This ECG requires no treatment and as stated above is not associated with the cat’s history of chronic vomiting.  However, this ECG suggests that there is an accessory pathway that may be associated with intermittent atrioventricular re-entry tachycardia. An echocardiogram would be indicated to determine the presence of underlying myocardial changes that may suggest persistent tachycardia (e.g. tachycardia induced cardiomyopathy). While not commonly performed in cats, a Holter may be helpful to document a reciprocating tachycardia especially if myocardial dysfunction is identifed on an echocardiogram.  Antiarrhythmics may be able to help resolve reciprocating tachycardia or in some instances dogs have undergone successful ablation of their accessory pathways. In this particular case Asa’s heart was echocardiographically normal and a Holter was unable to document periods of tachycardia.

    The CEG is funded through an educational grant from Boehringer Ingelheim Vetmedica, Inc., IDEXX Laboratories, Inc. and Nestle Purina PetCare.

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