Arrhythmogenic Right Ventricular Cardiomyopathy in English Bulldog with Brachycephalic Obstructive Airway Syndrome (BOAS)

Abstract

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a hereditary disorder where right ventricular cardiomyocytes are replaced by fibrofatty tissue, disrupting myocardial electrical continuity. Causes may include mutations in the striatin gene or cardiac ryanodine receptor gene. Brachycephalic Obstructive Airway Syndrome (BOAS) involves congenital abnormalities in brachycephalic dogs, such as stenotic nares and elongated soft palate, which can lead to right-sided cardiac remodeling and heart failure. This report aimed to present a case of category III ARVC in an English Bulldog with BOAS.

Case: A 9-year-old male English Bulldog, presented with episodes of syncope, postprandial cyanosis, and respiratory difficulty. The dog exhibited severe stenosis of the nares, characteristic of BOAS, along with signs of heart failure. Physical and complementary exams revealed chronic respiratory acidosis, hyponatremia, hypochloremia, and anemia. Echocardiography indicated significant remodeling of the cardiac chambers, particularly in the right ventricle, with tricuspid and pulmonary valve insufficiency, suggesting ARVC. Myocardial biopsy could not be performed. The electrocardiogram showed sinus tachycardia and other irregularities. Thoracic radiographs revealed cardiomegaly and signs of congestive heart failure (CHF). Analysis of abdominal transudate revealed significant peritoneal effusion. The dog succumbed 1 month after initial presentation, without a definitive ante mortem diagnosis and without authorization for necropsy.

Discussion: The definitive diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) is made through myocardial biopsy, a procedure often performed post mortem due to its difficulty in living animals. ARVC presents in 3 clinical forms: Category I is asymptomatic with few arrhythmias; Category II involves syncope and easy fatigue with monomorphic extrasystoles; and Category III, which is rare, includes signs of congestive heart failure (CHF), ventricular tachyarrhythmias, and occasionally atrial fibrillation. In English Bulldogs, ARVC is more likely to cause supraventricular arrhythmias. This breed often shows CHF signs such as edema and syncope, with a high prevalence of arrhythmias and CHF symptoms. Most ARVC cases have normal left ventricular function, but any deviations can significantly impact survival. Echocardiography typically reveals right heart chamber enlargement and tricuspid valve insufficiency. Conventional ECG detects premature ventricular complexes but may miss some arrhythmias, making Holter monitoring a better tool for long-term assessment. Thoracic radiography may show cardiomegaly and CHF signs, while abdominal imaging can reveal effusion indicating right-sided CHF. Although definitive diagnosis usually requires myocardial biopsy, complementary tests and clinical findings in this case suggest Category III ARVC. Treatment involves managing arrhythmias with antiarrhythmics like sotalol or mexiletine and addressing any CHF with standard protocols. Prognosis varies based on disease presentation, with a generally reserved to unfavorable outlook due to risks of sudden death or worsening heart function. This case underscores the complexity of diagnosing and managing ARVC in brachycephalic dogs with BOAS. Early and accurate identification of these conditions is crucial for effective interventions, although achieving a definitive in vivo diagnosis remains challenging. The case highlights the necessity for continuous monitoring and a multidisciplinary approach in managing dogs with multiple cardiac and respiratory comorbidities.

Keywords: cardiac remodeling, congestive heart failure, cyanosis, echocardiography, electrocardiogram, peritoneal effusion.