Max was diagnosed with Boxer arrhythmogenic right ventricular cardiomyopathy (ARVC) based on the finding of malignant ventricular arrhythmias of right ventricular origin in a Boxer with a structurally normal heart.
Propranolol was discontinued and Max was started on sotalol 40 mg PO BID. Sotalol is a class III antiarrhythmic agent with additional beta-blocking properties, making it an appropriate first-line choice for ventricular arrhythmias in Boxer ARVC.
The owner was instructed to monitor for further episodes of collapse and to return for a recheck Holter monitor in one week.
One Week Later
A recheck Holter monitor was performed.
Results showed persistent ventricular ectopy, though the sustained VT runs were less frequent than on the initial Holter.
The sotalol dose was increased to 80 mg PO BID.
One Month Later
Max has been doing well at home on sotalol 80 mg BID with no further episodes of collapse.
A recheck Holter monitor showed improvement: 9,451 PVCs over 24 hours, but the majority were single PVCs rather than the sustained runs of ventricular tachycardia seen on the initial Holter.
The owner was counseled that while the arrhythmia burden has improved, complete elimination of PVCs is unlikely, and the goal of therapy is to reduce the frequency and complexity of the arrhythmias (i.e., prevent sustained VT) and prevent syncope and sudden death.
Two Months Later
The owner reported that Max has collapsed again — three episodes in the past two weeks.
This represents sotalol breakthrough, which is unfortunately common in Boxer ARVC. The disease is progressive, and antiarrhythmic therapy may become less effective over time.
Options discussed with the owner included increasing the sotalol dose, adding mexiletine as combination therapy, or considering other antiarrhythmic agents.