Abstract 2233: Effects of Restitution in Early In-Vivo Human Ventricular Fibrillation on the Endocardium
Introduction: Classic diastolic interval (DI) restitution, conduction velocity restitution, and cardiac memory may determine action potential duration (APD) variation in ventricular fibrillation (VF). However classic diastolic interval (DI) restitution relationship has not been demonstrated in APD variation of in-situ swine VF.
Objectives: To study APD-DI relationship in early in-vivo human VF on the endocardium.
Methods: Monophasic action potentials (MAP) were recorded with a Franz catheter from the right and/or left ventricular apex in sinus rhythm and during VF induced as part of defibrillator threshold test in patients with an Automatic Implantable Cardioverter Defibrillator (AICD). APD90 was measured in sinus beat immediately preceding induction of VF (Panel A) and its amplitude were used to define 90% repolarization in VF (Panel B). DI was measured from end of APD90 to Vmax of next APD. APD to previous DI intervals were plotted (Panel C).
Results: Six VF episodes from 4 patients were studied. The mean age of the patients was 67 ± 9 years. All were males with ejection fraction less then 20% and 3 had ischemic cardiomyopathy. The mean VF episode lasted for 10.7 ± 5 seconds. Mean APD was 131 ± 17 ms and DI was 76 ± 22 ms. A plot of DI versus APD over the entire VF episode formed a scattered cluster of points with a its linear slope negative for all episodes (Mean slope −0.6 ± −0.3, R2 0.27 ± 0.25). Similar relationship was seen with APD60 also.
Conclusions: In early human VF, similar to in-situ swine, APD-DI relationship does not follow classic diastolic interval (DI) restitution relationship with positive slope.