Activation becomes highly organized during long-duration ventricular fibrillation in canine hearts

Abstract

Ideker RE. Activation becomes highly organized during long-duration ventricular fibrillation in canine hearts. Am J Physiol Heart Circ Physiol 298: H2046 -H2053, 2010. First published April 9, 2010 doi:10.1152/ajpheart.01196.2009Little is known about the threedimensional (3-D) intramural activation sequences during long-duration ventricular fibrillation (VF), including the role of the subendocardium and its Purkinje fibers (PFs) in long-duration VF maintenance. Our aim was to explore the mechanism of long-duration VF maintenance with 3-D electrical mapping. We recorded 10 min of electrically induced VF in the left ventricular anterior free wall of six 10-kg, open-chest dogs using a 3-D transmural unipolar electrode matrix (9 ϫ 9 ϫ 6, 2-mm spacing) that allowed us to map intramural activation sequences. At 2.5 Ϯ 1.8 min of VF, although the body surface ECG continued to exhibit a disorganized VF pattern, intramurally a more organized, synchronous activation pattern was first observed [locally synchronized VF (LSVF)]. This pattern occurred one or more times in all dogs and was present 33.4 Ϯ 31.4% of the time during 5-10 min of VF. As opposed to the preceding changing complex activation sequences of VF, during LSVF, wavefronts were large and highly repeatable near the endocardium, first exciting the endocardium almost simultaneously and then rapidly spreading toward the epicardium with different levels of conduction block en route. During LSVF, PF activations always preceded working myocardium activations near the endocardium. In conclusion, long-duration VF in dogs frequently becomes highly organized in the subendocardium, with activation fronts arising in this region and passing intramurally toward the epicardium, even though the surface ECG continues to exhibit a disorganized pattern. PFs appear to play an important role during this stage of VF.intramural ventricular fibrillation; locally synchronized ventricular fibrillation; Purkinje fibers SUDDEN CARDIAC ARREST is a leading cause of death in the industrialized world (25). Many lethal cardiac arrests are caused by ventricular fibrillation (VF) (25). The mean time from collapse until defibrillation in the prehospital setting, where most cardiac arrests occur, ranges from 4 to 10 min (21,22). Yet, relatively few studies have dealt with activation sequences during VF lasting Ͼ1 min [long-duration VF (20)], and little is known about the mechanisms of long-duration VF maintenance.Some studies have suggested an important role of Purkinje fibers (PFs) during long-duration VF maintenance (1,4,20,23). As in humans, PFs in canines are primarily located in the subendocardium (19). In canines, an endocardial-epicardial gradient of the activation rate develops during long-duration VF (1, 4, 23), with discrete, regular, rapid deflections persisting in the subendocardium (23), possibly caused by PFs. After endocardial ablation with Lugol's solution to eliminate PF activations, subendocardial PF signals were no longer recorded, and the transmural activation rate gradient dis...

Mechanisms of Long-Duration Ventricular Fibrillation in Human Hearts and Experimental Validation in Canine Purkinje Fibers

“…The criteria for re-entry in this study, however, were only met in 3 instances in LDVF, all on the endocardium or subendocardium ( Table 1). These findings are consistent with those of other studies that have found less reentry and increasingly frequent focal endocardial activations as VF progresses over time (5,10,11,18). We did not look for re-entry in a diagonal line, however, and needle spacing may have failed to identify small re-entry circuits in this study.…”

“…Initially we sought to characterize the transmural activation patterns of VF in 12 cardiomyopathic Langendorff human hearts from onset to LDVF (10 min During VF mapping, the local activation times (LATs) on unipolar recordings were taken as the maximum negative dV/dt (change is voltage/change in time) at each electrode, provided it was at least -0.5 mV/ms (10). Early VF recordings were taken at 3 s after onset (6), and LDVF recordings were taken at up to 10 min (3,4,10).…”

“…Early VF recordings were taken at 3 s after onset (6), and LDVF recordings were taken at up to 10 min (3,4,10). Purkinje fiber activations were initially identified on the left ventricular (LV) septum with the bipolar endocardial balloon during basal pacing.…”

Endocardial Activation Drives Activation Patterns During Long-Duration Ventricular Fibrillation and Defibrillation

“…9, 13, 14 Further details regarding basket catheter data analysis methods can be found in the data supplement of Li et al, 2013. 13 In brief, the VF episodes were broken into 2-second epochs and activations were detected by taking the 9-point first temporal derivative and finding the most negative the local minimum that exceeds -0.3 v/s with a 50-ms search window followed by a 50-ms refractory period subsequent to an identified activation.…”

Verapamil reduces incidence of reentry during ventricular fibrillation in pigs

“…The heart was exposed through a median sternotomy and supported in a pericardial sling. Although intramural mapping can provide more accurate data during VF, it requires more aggressive and time consuming techniques with multiple plunge needle electrode insertions (30). The reentry incidence calculated from intramural (30) and epicardial (4) mapping techniques are comparable and parallel during the early stage of VF.…”