Preexcitation alternans in a dog

Pre-excitation alternans in a cat

A nine-year-old male neutered domestic Shorthair cat presented on referral for evaluation. The cat presented to its primary veterinarian for acute onset vomiting, panting, and weakness. An electrocardiogram performed at the regular veterinarian was concerning for ventricular tachycardia, and the cat was referred for further evaluation. An echocardiogram revealed hypertrophic cardiomyopathy, and a review of the electrocardiogram revealed findings suggestive of ventricular pre-excitation alternans with the suspect pre-excited complexes appearing to alternate with sinus complexes. This is the first reported case of pre-excitation alternans in a cat.

Ventricular pre-excitation in cats: 17 cases

OBJECTIVES

Atrioventricular accessory pathways are abnormal electrical connections between the atria and ventricles that predispose to ventricular pre-excitation (VPE) and tachycardias.

ANIMALS

Seventeen cats with VPE and 15 healthy matched-control cats.

MATERIAL AND METHODS

Multicenter case-control retrospective study. Clinical records were searched for cats with VPE, defined as preserved atrioventricular synchrony, reduced PQ interval, and increased QRS complex duration with a delta wave. Clinical, electrocardiography, echocardiographic, and outcome data were collated.

RESULTS

Most cats with VPE were male (16/17 cats), non-pedigree cats (11/17 cats). Median age and mean body weight were 5.4 years (0.3-11.9 years) and 4.6 ± 0.8 kg, respectively. Clinical signs at presentation included lethargy (10/17 cats), tachypnea (6/17 cats), and/or syncope (3/17 cats). In two cats, VPE was an incidental finding. Congestive heart failure was uncommon (3/17 cats). Nine (9/17) cats had tachyarrhythmias: 7/9 cats had narrow QRS complex tachycardia and 2/9 cats had wide QRS complex tachycardia. Four cats had ventricular arrhythmias. Cats with VPE had larger left (P < 0.001) and right (P < 0.001) atria and thicker interventricular septum (P = 0.019) and left ventricular free wall (P = 0.028) than controls. Three cats had hypertrophic cardiomyopathy. Treatment included different combinations of sotalol (5/17 cats), diltiazem (5/17 cats), atenolol (4/17 cats), furosemide (4/17 cats), and platelet inhibitors (4/17 cats). Five cats died, all from cardiac death (median survival time 1882 days [2-1882 days]).

CONCLUSIONS

Cats with VPE had a relatively long survival, albeit showing larger atria and thicker left ventricular walls than healthy cats.

Reversible myocardial injury aggravated by complex arrhythmias in three Toxoplasma gondii-positive dogs

Although Toxoplasma gondii represents an oft-cited cause of myocarditis in veterinary medicine, the existing literature on the pre-mortem demonstration of T. gondii-associated myocardial injury (MI) in dogs is scant. In this case series, we provide detailed clinical, laboratory, echocardiographic and electrocardiographic description of three T. gondii-positive dogs diagnosed with MI. In all cases, etiological diagnosis was based on the antibody screening test (all dogs had IgM titres ≥1:64) and MI was demonstrated by a concomitant increase of the serum concentration of cardiac troponin I (0.25–9.6 ng/ml, upper hospital limit <0.15 ng/ml). In all dogs, MI was aggravated by complex arrhythmias (ventricular in two dogs, and either ventricular and supraventricular in the remaining dog). In one case, left ventricular systolic dysfunction was also present. All dogs underwent an extensive diagnostic work-up aimed at excluding additional comorbidities, either cardiac and extra-cardiac, possibly able to contribute to MI, arrhythmias and systolic dysfunction. All dogs received appropriate antiprotozoal (i.e., clindamycin) and antiarrhythmic (i.e., amiodarone, sotalol) therapy. This was systematically followed by a simultaneous decline in T. gondii serology titres, normalisation of troponin level and left ventricular systolic function, and the resolution of clinical and electrocardiographic abnormalities. In light of this result, therapies were interrupted and subsequent controls ruled out any disease relapse. In these cases, the clinical and instrumental findings obtained at admission and rechecks strongly supported the clinical suspicion of toxoplasmic myocarditis.