Inducible ventricular arrhythmias in a naturally occurring model of cardiomyopathy

This study examined inducibility of ventricular tachyarrhythmias in turkeys with and without naturally occurring dilated cardiomyopathy. Using a transvenously positioned electrode catheter, 32 cardiomyopathy and 12 control unsedated turkeys aged 2 to 4 months were studied by right ventricular endocardial extrastimulus testing at basic pacing cycle lengths of 200 and 170 ms with both 1 and 2 extrastimuli and burst pacing at progressively shorter cycle lengths (200 to 100 ms). Following study, a dilatation index (determined as the ratio of left ventricular endocardial and epicardial diameter at level of the apex-base midpoint) was utilized to assess the functional severity of cardiomyopathy. All control turkeys had a dilatation index less than 0.3. In cardiomyopathic turkeys, dilatation index was normal (less than 0.3) in 3/32, showed mild to moderate dilatation in 25/32 (0.3 to 0.6), and severe dilatation in 4/32 (greater than 0.6). Results showed no difference in right ventricular effective or functional refractory periods between control and cardiomyopathic turkeys. Control turkeys had no inducible ventricular tachyarrhythmias, but 16/32 cardiomyopathic turkeys (p