Advances in Animal Cardiology

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The present study was designed to assess QTc and the relationship between the QT and the RR intervals in beagle dogs. Standard limb lead ECGs were recorded using a canine autoanalyzing electrocardiograph in 77 dogs.
The results obtained were as follows ;
1. The RR intervals had a large variation in 6-second ECG tracings, while the variation in the QT interval was negligible on each ECG.
2. Significant positive correlations were observed between any type of RR intervals (longest, shortest, mean and just before the QT interval measured by the autoanalyzing ECG) and the QT interval in 70 dogs. The greatest correlation was seen between the mean RR interval and the QT interval.
3. Repeated ECG recording in 7 dogs revealed a significant positive correlation between the RR and the QT intervals in 6 dogs, and the greatest correlation was also between the mean RR interval and the OT interval among the 4 defined RR intervals. One dog in which a correlation was not found had a high CV-RR value and showed a ventricular premature beat on ECG.
4. To address the problem that the QT interval value corrected for RR interval (QTc=QTc₆₀) is larger than the uncorrected value in many dogs, comparisons of QTc₆₀ and QTc₁₀₀ were made. The QTc₁₀₀ values were closer to the uncorrected QT intervals than were the QTc₆₀ value.

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A Congenital portosystemic shunt was found in a 59-day-old female Holstein calf. The portal vein joining the splenic and cranial mesenteric veins communicated with the caudal vena cava through a large shunt vessel caudal to the liver. The portal vein ran toward the porta of liver and continued to the left ramus of the portal vein. The right ramus of the portal vein could not be detected. The liver was small and intrahepatic portal branches were hypoplastic. Hepatocytes exhibited mild degenerative changes in the peripheral zone of the lobule.

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