Defibrillation of German shepherds with inherited ventricular arrhythmias and sudden death.
ABSTRACT 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.
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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.Pacing and Clinical Electrophysiology 06/2006; 23(2):253 - 258. DOI:10.1111/j.1540-8159.2000.tb00807.x · 1.25 Impact Factor