Electrocardiographic, echocardiographic, and left atrial strain imaging features of a dog with atrial flutter and third-degree atrioventricular block.

A 14-year-old American Staffordshire terrier was presented for episodes of exercise-induced syncope. At admission, atrial flutter coupled to third-degree atrioventricular block was diagnosed electrocardiographically. On the second day of hospitalization, surface electrocardiogram revealed spontaneous conversion to sinus rhythm with persistence of atrioventricular block. Complete transthoracic echocardiograms were performed after each electrocardiographic examination. The combined use of conventional echocardiography with tissue Doppler imaging-based modalities allowed to investigate the atrial electromechanical correlation and function during typical atrial flutter and after its resolution.