Boxer ARVC is distinguished from other ventricular arrhythmias primarily by the combination of left bundle branch block (LBBB)-morphology ventricular premature complexes (VPCs) on ECG, a VPC count ≥300/24 hours on Holter monitoring, absence of other identifiable cardiac disease, and breed predisposition — with genetic testing for the striatin mutation providing additional confirmation.
The hallmark ECG finding is VPCs with LBBB morphology — a positive net deflection in leads II, III, and aVF — consistent with right ventricular origin.Journal of the…+1 Multiple VPC morphologies (both LBBB and right bundle branch block patterns) have been reported, and polymorphic ventricular tachycardia can occur.Journal of the… The key differential to exclude is idiopathic outflow tract ventricular tachycardia (OTVT), which also produces LBBB-pattern VAs but is nonfamilial and lacks histopathological abnormalities; OTVT is adrenergically mediated via triggered activity (delayed afterdepolarizations), whereas ARVC arises from fibrofatty replacement providing a reentrant substrate.Journal of Vete…
Holter monitoring is the cornerstone of antemortem diagnosis. ARVC is defined as ≥300 VPCs/24 hours in the absence of other disease; dogs with ≤20 VPCs/24 hours of right ventricular origin are classified as unaffected.Veterinary Reco…+1 VPC frequency is relatively constant throughout the day, though slightly higher during 0800–1200 and 1600–2000 hours, and lowest between midnight and 0400 hours — a pattern that supports full 24-hour recording rather than spot ECG.Journal of Vete… Because day-to-day arrhythmia variability is recognized, a single Holter result may not capture the full arrhythmia burden.Veterinary Scie…
Exercise testing improves diagnostic classification. Dogs with >100 VPCs/24 hours show greater increases in both VPC count and high-sensitivity cardiac troponin-I (hs-cTnI) after brief moderate-intensity exercise compared with dogs with ≤100 VPCs/24 hours.Journal of Vete… Dogs carrying the striatin mutation show greater post-exercise increases in both VPC count and hs-cTnI than non-mutation carriers, making exercise a useful unmasking tool in equivocal cases.Journal of Vete… Physical activity should be controlled as a variable during all Holter recordings.Journal of Vete…
Echocardiography supports but does not establish the diagnosis. Most affected Boxers have apparently normal echocardiograms, though a subset develops myocardial dysfunction.Journal of Vete… Tricuspid annular plane systolic excursion (TAPSE) and pulsed-wave tissue Doppler-derived lateral tricuspid annular systolic velocity (S') are both reduced in ARVC-affected Boxers compared with healthy controls, and each has an area under the ROC curve of 0.77 for distinguishing healthy Boxers from those with ARVC.Journal of Vete… A minority of affected dogs develop left ventricular systolic dysfunction in addition to arrhythmias; fractional shortening <20% was documented in 2 of 49 ARVC dogs in one natural history cohort.Journal of Vete…
Genetic testing for the striatin mutation stratifies risk but does not replace Holter monitoring. Of 49 ARVC dogs in a prospective natural history study, 36 of 43 genotyped dogs were striatin-positive; 7 were striatin-negative yet met arrhythmia criteria, confirming that mutation-negative Boxers can still have ARVC.Journal of Vete… Homozygous dogs carry a worse prognosis than heterozygotes.Veterinary Clin… Striatin-negative Boxers with frequent LBBB VAs on Holter should still be considered affected.Journal of Vete…
Endomyocardial biopsy with plakoglobin (PG) immunofluorescence can differentiate advanced ARVC from other myocardial diseases. Reduced PG signal at the intercalated disc is present in dogs with advanced, clinically apparent ARVC but is absent in the occult (early arrhythmia-only) phase.Veterinary Scie… In one cohort, 3 of 8 histopathologically confirmed ARVC dogs with clinical signs showed reduced PG, while 40 of 41 dogs with non-ARVC cardiac disease had preserved PG signal — making PG reduction a useful confirmatory marker when advanced disease is suspected.Veterinary Scie… Definitive diagnosis remains histopathologic identification of transmural fibrofatty replacement of the right ventricle.Veterinary Scie…
Anti-desmoglein-2 (DSG2) autoantibodies are not diagnostically useful. DSG2 autoantibodies are detectable in healthy controls, preclinical ARVC dogs, and clinical ARVC dogs alike, and do not reliably discriminate between groups.Veterinary Reco…
| Feature | Finding in ARVC | Diagnostic Cutoff / Value | Key Caveat |
|---|---|---|---|
| VPC morphology (ECG) | LBBB pattern (positive leads II, III, aVF) | — | Multiple morphologies possible; OTVT is a mimic Journal of the…+1 |
| Holter VPC count | ≥300 VPCs/24 h = affected; ≤20 = unaffected | 300 VPCs/24 h | Day-to-day variability; single recording may underestimate Veterinary Reco…+1 |
| Exercise testing | Greater VPC and hs-cTnI rise post-exercise in affected dogs | >100 VPCs/24 h threshold | Activity must be controlled during all Holter recordings Journal of Vete… |
| TAPSE / S' (echo) | Both reduced vs. healthy controls | AUC 0.77 for each | Most affected dogs have normal echocardiograms Journal of Vete…+1 |
| Striatin mutation | Present in majority of affected dogs | — | Mutation-negative dogs can still have ARVC Journal of Vete… |
| PG immunofluorescence (biopsy) | Reduced in advanced/clinical ARVC | — | Not reduced in occult phase Veterinary Scie… |
| Anti-DSG2 autoantibodies | Present in affected and healthy dogs | — | Does not discriminate between groups Veterinary Reco… |
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