Ventricular arrhythmias in Rhodesian Ridgebacks with a family history of sudden death and results of a pedigree analysis for potential inheritance patterns.

OBJECTIVE To evaluate a group of related Rhodesian Ridgebacks with a family history of sudden death for the presence of arrhythmia and to identify possible patterns of disease inheritance among these dogs. DESIGN Prospective case series and pedigree investigation. ANIMALS 25 Rhodesian Ridgebacks with shared bloodlines. PROCEDURES Pedigrees of 4 young dogs (1 female and 3 males; age, 7 to 12 months) that died suddenly were evaluated, and owners of closely related dogs were asked to participate in the study. Dogs were evaluated by 24-hour Holter monitoring, standard ECG, echocardiography, or some combination of these to assess cardiac status. Necropsy reports, if available, were reviewed. RESULTS 31 close relatives of the 4 deceased dogs were identified. Of 21 dogs available for examination, 8 (2 males and 6 females) had ventricular tachyarrhythmias (90 to 8,700 ventricular premature complexes [VPCs]/24 h). No dogs had clinical signs of cardiac disease reported. Echocardiographic or necropsy evaluation for 7 of 12 dogs deemed affected (ie, with frequent or complex VPCs or sudden death) did not identify structural lesions. Five of 6 screened parents of affected dogs had 0 to 5 VPCs/24 h (all singlets), consistent with a normal reading. Pedigree evaluation suggested an autosomal recessive pattern of inheritance, but autosomal dominant inheritance with incomplete penetrance could not be ruled out. CONCLUSIONS AND CLINICAL RELEVANCE Holter monitoring of Rhodesian Ridgebacks with a family history of an arrhythmia or sudden death is recommended for early diagnosis of disease. An autosomal recessive pattern of inheritance in the studied dogs was likely, and inbreeding should be strongly discouraged.

Calculation of pressure half-time.

Doppler echocardiography is useful in assessing the severity of obstructive cardiac lesions, such as mitral valve stenosis. The Doppler study can be used to calculate pressure half-time (PHT), which is defined as the time required for the pressure gradient across an obstruction to decrease to half of its maximal value. Thus, PHT increases as the severity of stenosis increases. In this report, we describe the methodology involved in measuring PHT in a dog with mitral valve stenosis before and after balloon valvuloplasty.