Quantitation of cardiac gross morphology during the development of FZ-induced cardiomyopathy in turkey poults.

Furazolidone (FZ) at a dose of 700 ppm was fed to turkey poults 2-5 weeks posthatch. At 3, 4, and 5 weeks of age, seven poults each were sacrificed from control and FZ-fed groups. A section of ventricular tissue 1 mm thick was excised from the heart distal to the base at a level one-fourth of the distance between the base and apex. Parameters estimated from tracings of each section were area and circumference of both right and left ventricular lumen profile, area and circumference of entire heart profile, area of right ventricular free wall profile, area of left ventricular and septal wall profile, and area of entire heart muscle profile. A major finding was a sequential increase in the area of the ventricular lumina in the FZ-fed poults. Differences between the control and FZ-fed poults were statistically significant for the right lumen profile at 3 and 5 weeks of age and for the left lumen profile at 4 and 5 weeks of age. The area of the heart muscle profile was decreased in FZ-fed poults, but this difference was statistically significant only at 4 weeks of age. Data suggest that the pathogenesis of FZ-induced cardiomyopathy involves a dilation of ventricular lumina resulting in increased intraventricular blood volume and altered ECG patterns. Relationships between gross morphology and ECGs may be seen only in terminal cases of several weeks duration. This explains the inability to correlate ECGs with gross morphologic changes in all poults observed at necropsy.