concurrent atrioventricular block, sinus arrest and pneumothorax in a dog secondary to vehicle accident

in human several kinds of electrocardiographic findings have been reported in association with pneumothorax such as decreased and/or alternating qrs amplitude (electrical alternans). however, electrocardiographic changes concurrent with pneumothorax have rarely been discussed in veterinary literature. a 3-year-old male crossbreed dog was presented with a history of car accident. thoracic auscultation revealed decreased lung sounds. heart sounds were also markedly muffled bilaterally. an electrocardiogram revealed sinus arrest in association with first degree atrioventricular block. pneumothorax was the main finding in thoracic radiographs. seven days after initial admission, thoracic radiographs revealed that pnuemothorax was resolved and all electrocardiographic abnormalities returned to normal limits.