To characterize defibrillation success in German shepherd (GS) dogs with inherited ventricular arrhythmias and sudden death.
Ventricular tachycardia (VT) degenerates to ventricular fibrillation (VF) as the cause of death in GS dogs. To test the hypothesis that GS dogs are more difficult to defibrillate than other dogs, we sought to compare defibrillation success of induced VF in affected GS dogs to a control group of beagles.
ECG and monophasic action potential (MAP) recordings were acquired during VF and transthoracic defibrillation in anesthetized GS dogs (n=13) and normal beagles (n=7). Shock efficacy, energy requirements, VF frequency and post-defibrillation rhythms were compared between the 2 groups.
First shock success of all episodes of VF was lower in GS dogs (10 of 18) than beagles (46 of 47) (p<0.0001). However, when evaluated by dog, shock success was not different between GS and beagles (7 of 13 and 6 of 7, respectively; p=0.15). Multiple shock success (</=3 consecutive shocks) resulted in a poorer defibrillation success of all episodes of VF in GS dogs (15 of 18) as compared to beagles (47 of 47) (p<0.02). Multiple shock success evaluated by dog was similar between GS (11 of 13) and beagles (7 of 7) (p=0.11).
Affected GS dogs had lower defibrillation success than beagles; however, defibrillation was possible in the majority of cases.
[Show abstract][Hide abstract] ABSTRACT: During temperature-controlled radiofrequency (RF) ablation a popping sound sometimes occurs. This popping phenomenon is known to be associated with unwanted effects like blood boiling, endocardial rupture, catheter dislocation, and impedance rise. The present in vitro study determined the influence of cooling, electrode contact, and tip temperature on the occurrence of popping phenomena. Pieces of porcine ventricle were immersed in a bath of saline solution at 37°C, Forty-two RF ablations were performed with different electrode-tissue contact forces (i.e., 0.0–0.44N) in a temperature-controlled mode (70°C setpoint, 30 s, 50 W maximum power output, 4-mm tip, thermocouple). Half of the 42 ablations were performed with fluid flow (0,1 m/s, group I), the other half without flow (group II). In group I, mean tip temperature and power were 55.6 ± 8.5°C and 36.2 ± 13.8 W, resulting in a lesion volume of 121 ± 57 mm. In group II, the respective values were 67.3 ± 1.5°C and 9.9 ± 5.2 W resulting in a volume of 42 ± 18 mm3. The differences between groups were statistically significant. Overall, ten popping phenomenas occurred in group I and none in group II. Pops occurred significantly more often when the contact force was <0.1 N (8/10) and the tip temperature was <60°C (8/10). Two endocardial ruptures occurred, both were associated with a popping phenomenon. Using temperature control, the probability of pops is significantly higher when the ablation electrode and the endocardial tissue surface are exposed to fluid flow and the electrode-tissue contact is poor. Under these conditions the tissue temperature can be much higher than the temperature measured at the tip electrode and can potentially reach 100°C causing in-tramyocardial steam formation and a popping phenomenon.
[Show abstract][Hide abstract] ABSTRACT: Ventricular arrhythmias (VA) and sudden death are inherited in German Shepherd Dogs (GSDs).
To estimate the genetic parameters (heritabilities and correlations) of 3 traits of VA (single premature ventricular complexes (PVCs), 2 consecutive PVCs (couplets), and 3 or more consecutive PVCs-ventricular tachycardia [VT]).
Three hundred and ninety-eight GSDs. Methods: Prospective, observational, case control study. Dogs were phenotyped by 24-hour ambulatory ECG from 6 to 45 weeks of age. Edited ECG records included the number of incidents of (1) single PVCs, (2) couplets, and (3) VT.
A data set of 1,239 Holter records from 398 GSDs was used to estimate genetic variables. Phenotypic correlations for affectedness (binarily coded 0/1) of the 3 traits ranged from 0.55 to 0.74, whereas correlations for severity (continuous values of 24-hour VA counts) ranged from 0.26 to 0.39. Estimates of genetic correlation among the severity traits were 0.06 to 0.27. Estimated heritabilities were 0.54, 0.54, and 0.46 for affectedness and 0.33, 0.69, and 0.69 for severity of PVCs, couplets, and VT, respectively. Month and year of birth and age at ECG recording had significant effects on all 3 traits. Season of ECG recording had a significant effect on the number of single PVCs, but not couplets or incidents of VT. Age of onset differed, with single PVCs appearing an average of 4 days earlier than couplets and VT.
These results imply a strong genetic component for this disease but suggest that differences in the 3 traits should be taken into consideration in studies to identify the underlying genes.
Journal of Veterinary Internal Medicine 03/2009; 23(2):264-70. DOI:10.1111/j.1939-1676.2009.0265.x · 1.88 Impact Factor
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