Cardiac Electrophysiological Consequences of Neuromuscular Incapacitating Device Discharges
Kumaraswamy Nanthakumar, MD*,
Ian M. Billingsley, MD,
Stephane Masse, MASc,
Paul Dorian, MD,
Douglas Cameron, MD,
Vijay S. Chauhan, MD,
Eugene Downar, MD and
Elias Sevaptsidis, DEC
University of Toronto, Toronto, Ontario, Canada.
View larger version (36K):
[in a new window]
|
Figure 1 Nonthoracic neuromuscular incapacitating device (NID) discharge. This figure illustrates a typical episode of NID discharge in the nonthoracic vector configuration, which does not result in the stimulation of the myocardium. The surface electrocardiogram lead 1, intracardiac electrograms from the coronary sinus (CS) and the right ventricular (RV) apex, and blood pressure (BP) recording from the MILLAR catheter in the descending aorta are shown. (A) The rhythm before the NID discharge. This shows regular rhythm. It is very similar to the rhythm and rate in (C). Interestingly, in B, the surface electrocardiograms are corrupted by the high voltage discharge. However, the intracardiac electrograms, as shown in D and E, do not show any significant change in rate morphology and are not phase locked (no temporal relationship between stimuli and the electrogram) with the NID discharge. Note also the lack of perturbation of blood pressure during the discharge. The rate and morphology are not significantly different between D and E, further illustrating the lack of myocardial stimulation.
|
|
View larger version (40K):
[in a new window]
|
Figure 2 Thoracic neuromuscular incapacitating device (NID) discharge. This figure shows a typical example of an NID (model X26) discharge in the thoracic vector configuration. This shows again the corruption of surface electrocardiographic leads in B; however, in the intracardiac electrograms, electrical activity is noted. In C, after the NID discharge, spontaneous return of regular sinus rhythm and blood pressure are shown. Note the immediate return of the rhythm, similar to A. In D and E, the intracardiac electrograms have been magnified and the same duration is shown in both. It is evident in E that the rate is much faster and the rhythm is wider compared with D. The morphology of the tachycardia in E is wider than the morphology in D. There is a constant NID stimulus artifact to electrogram duration as shown in E, with every third NID discharge resulting in stimulation of the heart. Note the loss of blood pressure during the stimulation and the recovery of blood pressure once the discharge is completed. Abbreviations as in Figure 1.
|
|
View larger version (27K):
[in a new window]
|
Figure 3 Ventricular fibrillation during simulated stress and neuromuscular incapacitating device (NID) discharge. This shows an NID discharge in the thoracic configuration that resulted in ventricular fibrillation during epinephrine infusion (A). In B, as noted by the arrowheads, during the discharge there was a 3:1 phase lock of NID discharge that progressed to a 2:1 phase lock resulting in rapid ventricular tachycardia (VT), and in C this tachycardia degenerates into polymorphic VT that results in ventricular fibrillation. Abbreviations as in Figure 1.
|
|
View larger version (28K):
[in a new window]
|
Figure 4 Ventricular tachycardia during simulated stress and neuromuscular incapacitating device (NID) discharge. This shows an NID discharge in the thoracic configuration that resulted nonsustained ventricular tachycardia that spontaneously reverted back to sinus rhythm. In the enlargement, the time of onset of tachycardia shows the possibility that the penultimate NMI discharge was delivered at the vulnerable period of the T-wave, resulting in the arrhythmia. Abbreviations as in Figure 1.
|
|
|
