Congestive heart failure (CHF) was evaluated by retrospective review of case records of 66 Doberman Pinschers presenting with overt signs of 2 weeks' duration or less. Left-sided CHF was predominant, the majority of dogs were male, most were 5 to 10 years of age, and CHF tended to occur in females at an older age. Sudden death occurred in 13 dogs (20%). The mean and median survival times of all dogs were 9.65 and 6.5 weeks, respectively. Both atrial fibrillation and bilateral CHF at the time of presentation were associated with significantly shorter survival times.

Results of high-quality Holter recordings may be used to identify overtly healthy Doberman Pinschers that are at a high risk for dilated cardiomyopathy.

Results suggested that along with echocardiography, 24-hour ambulatory electrocardiography can be used to help identify overtly healthy Doberman Pinschers with cardiomyopathy.

Tocainide was administered t o 23 cardiomyopathic Doberman Pinschers at doses of 15 t o 25 rnglkg tid. These doses produced peak (2-hour) serum concentrations of 6.2 t o 19.1 mg/L and trough (&hour) serum concentrations of 2.3 t o 11.1 mg/L. Anorexia and gastrointestinal disturbances occurred in 8 dogs (35%) at doses (15.6 t o 25.0 mg/kg) that were not different from those (16.0 t o 26.0 mg/kg) received by dogs that did not experience toxicity. Doses producing peak serum concentrations that were either greater or less than 14 mg/L were not different. Likewise, doses producing trough values that were either greater or less than 6 mg/L were not different. The mean dose that produced peak serum concentrations of 10 t o 13.6 mg/L and trough concentrations of 4.2 t o 10.0 mg/L was 17.9 mglkg, and was associated with anorexia in 4 dogs. Mean peak serum concentrations associated with toxicity (14.4 mg/L) were significantly higher ( P = .02) than dogs not experiencing ocainide is an orally administered lidocaine analog that T is indicated for the treatment of severe, potentially lifethreatening ventricular tachyarrhythmias (VTA). In humans, tocainide has been proven effective in treating symptomatic VTA in some patients unresponsive to other antiarrhythmic drugs.'-3 At recommended doses and serum concentrations, tocainide causes little hemodynamic ~h a n g e .~.~ The recommended therapeutic plasma concentration range is 4 to 10 mg/L, although a trough value of 6 mg/L is referr red.^.^ Cardiomyopathy in Doberman Pinschers is a chronic, slowly progressive disease characterized by VTA of variable seventy, sudden death, or end-stage congestive heart failre.^-'* Early in the disease, ventricular tachyarrhythmias usually are not severe, but by 1.5 to 2 years after their onset and the detection of early echocardiographic abnormalities, the VTA often become severe and this exacerbation is associated with significant reductions of ejection fra~tion.~.~"' The prevalence of sudden death in Dobermans with cardiomyopathy is approximately 20% to 30%.9.'0 Tocainide is a relatively recent addition to the antiarrhythmic group of drugs available for treating VTA. The purpose of this report is to describe doses, toxicity, and efficacy of tocainide in occult cardiomyopathy of Doberman Pinschers. MethodsFrom June 1986 through May 1990,23 Doberman Pinschers ranging in age from 1 to 11 years (mean, 8.0 yrs) that had occult cardiomyopathy and VTA were treated with tocainide. Tocainide was administered because of one or more of the following: VTA (13 dogs), a history of syncope attributable to VTA (5 dogs), and to determine drug efficacy (9 dogs). Two dogs received 2 separate courses of therapy. In all instances, arrhythmia quantification was accompllished by 24-hour ambulatory EKG (Holter) recordings.We defined occult cardiomyopathy as echocardiographic abnormalities and VTA in dogs without overt evidence of congestive heart failure (CHF); the diagnosis was based on cardiac ultrasound measurements and long-term ambulatory EKG (Holter) record...

Paradoxical sinus bradycardia and cardiac asystole resulted in episodic weakness, syncope, or aborted sudden cardiac death during exertion in 8 cardiomyopathic Doberman Pinschers. Bradycardias persisted for 1 to 2 minutes in 5 of 8 dogs, and were often followed by sinus tachycardia.yncope and sudden cardiac death are common in cardio-S myopathic Doberman Pinschers. Ventricular tachyarrhythmias of variable, but generally progressive severity typically are present in cardiomyopathic Doberman Pinschers, and ventricular tachycardia-fibrillation have been observed at the time of the dogs' death.'-5 Syncope and sudden cardiac death are also important problems in humans with dilated cardiomyopathy.6-21 Regardless of the underlying etiology, ventricular tachyarrhythmias (ventricular tachycardia-fibrillation) are most commonly implicated in sudden death?4,25 However, severe bradycardia has been associated with cardiovascular collapse in some human patient^.?^.*^ The purpose of this report is to describe the clinical findings and long-term ambulatory EKG (Holter) recordings in 8 cardiomyopathic Doberman Pinschers that experienced recurrent syncope and episodic weakness.Collapse followed by rapid recovery is termed fainting or syncope. Protracted syncope with loss of cardiopulmonary function, followed by recovery, can be termed aborted sudden death?," When an individual dies within minutes of collapse, it is called sudden or instantaneous death. Because of the unpredictable and transient nature of such events, substantiation of the diagnosis is d i f f i~u l t .~~~~' Thus, relatively few episodes of syncope and sudden death have been documented electrocardiographically; in humans, these are most often the result of ventricular tachycardia-fibrillation,24,?S Case ReportsSeven Doberman Pinschers with occult cardiomyopathy and 1 Doberman Pinscher with acute left-sided congestive heart failure were examined. Physical examinations, thoracic radiographs, cardiac ultrasound, EKG, and 24-hour ambulatory EKG (Holter) recordings were performed on each dog. Dog 1A 5-year-old, 39-kg, male was examined because of 2 episodes of ataxia, weakness, and incoordination associated with severe exertion. No abnormalities were found on physical examination, static EKG, or thoracic radiographs. Results of cardiac ultrasonography were equivocal, with a left ventricular shortening fraction (SF) of approximately 27% to 28%, an E-point to septal separation of 8 mm, a maximum left-ventricular end-diastolic dimension (LVIDd) of 47 mm, and a mean velocity of circumferential shortening (Vcf) of 1.56 circumferences per second (circudsec). In our experience, the left-ventricular SF in normal Doberman Pinschers should be at least 3096, the E-point to septal separation should be less than 9 mm, the LVlDd should be less than 46 mm in dogs weighing less than 39 kg but may possibly be up to 49 mm in larger dogs, and the mean Vcf should be 21.5 circudsec.*' O'Grady and Home have reported similar values.z9 There was no evidence of atrial enlargement. The septal a...