Intermittent bradyarrhythmia in a Hispaniolan Amazon parrot (Amazona ventralis). 
A clinically normal 2-year-old Hispaniolan Amazon parrot (Amazona ventralis) was found to have periodic second-degree atrioventricular (AV) block with variable nodal conductions while anesthetized with isoflurane during a thermal-support research project.  Arrhythmias were observed on 5 successive weekly electrocardiograms.  A complete cardiac evaluation, including a diagnostic electrocardiogram, revealed intermittent bradyarrhythmias ranging from a 2:1 to a 7:1 second-degree AV block, with concurrent hypotensive episodes during the nodal blocks.  Results of a complete blood cell count, plasma biochemical profile, blood gas analysis, and atropine-response test, as well as radiography and auscultation, revealed no obvious cause for the arrhythmias.  Echocardiography demonstrated cardiac wall thickness, chamber size, and systolic function similar to other psittacine birds.  On return to the colony, the parrot continued to be outwardly asymptomatic despite the dramatic conduction disturbances.  Although cardiac arrhythmias, including second-degree AV block, have been widely reported in birds, the wide variation of nodal conductions, the intermittent nature, and an arrhythmia with a 7:1 second-degree AV block that spontaneously reverts to normal as seen in this case have not been well documented in parrots.