Right Atrial Septal Electrode for Reducing the Atrial Defibrillation Threshold

Abstract

Background-The atrial defibrillation threshold (ADFT) energy of the standard lead configuration, right atrial appendage (RAA) to coronary sinus (CS), was reduced by Ͼ50% with the addition of a third electrode traversing the atrial septum in a previous study. This study determined whether the ADFT would be lowered by a more clinically practical third electrode placed in the right atrium along the atrial septum (RSP). Methods and Results-Sustained atrial fibrillation was induced in 8 closed-chest sheep with burst pacing and maintained with pericardial infusion of acetyl-␤-methylcholine chloride. A custom-made, dual-defibrillation catheter was placed with electrodes in the lateral RA, CS, and RSP. A separate defibrillation catheter was also placed in the RAA. ADFT characteristics of RAA3 CS and 6 other single-or sequential-shock configurations were determined in random order by using biphasic, truncated-exponential waveforms in a multiple-reversal protocol. The delivered-energy, peak-voltage, and peak-current ADFTs for the sequential-shock configuration CS3 RSP/RA3 RSP (0.53Ϯ0.31 J, 86Ϯ22 V, and 1.6Ϯ0.6 A, respectively) were significantly lower than those of RAA3 CS (1.14Ϯ0.64 J, 157Ϯ34 V, and 2.5Ϯ1.1 A, respectively). The ADFT characteristics of RAA3 CS and RA3 CS were not significantly different, nor were those of CS3 RSP/RA3 RSP and CS3 RSP/RAA3 RSP. Conclusions-The ADFT of the standard RAA3 CS configuration may be markedly reduced with an additional electrode situated at the RSP.

From Mouse to Whale

“…[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] The collected data fall into 4 different categories based on the mode in which they were reported in the literature for each of the 3 parameters (ie, PR, HR, and BM): (1) measurements from single animals, (2) multiple animal measurements reported as mean values without SD, (3) multiple animal measurements reported as means with SDs, and (4) values reported as ranges without means or SDs. For convenience, the allometric equation YϭY 0 · BM b can be transformed into a logarithmic form, lnYϭlnY 0 ϩb · lnBM, which describes a straight line of the form yϭinterceptϩbx.…”

How, Why, and When May Atrial Defibrillation Find a Specific Role in Implantable Devices? A Clinical Viewpoint

“…As in ventricular defibrillation, biphasic shocks are standard, but tolerability still requires improvement. Further reductions in the atrial defibrillation threshold could be achieved by improving lead configuration 22,24,25,47–49 . One possibility that has already been tested in clinical practice is implantation of a dedicated lead in the coronary sinus (Fig.…”

“…One proposed strategy contemplates sequential shocks delivered through a dual‐current pathway: this approach has generated promising experimental results both in animals 50 and humans 47 . A further possibility, which so far has been tested only in animals, involves deployment of an additional shock lead at the interatrial septum 48,49 …”

“…Further reductions in the atrial defibrillation threshold could be achieved by improving lead configuration. 22,24,25,[47][48][49] One possibility that has already been tested in clinical practice is implantation of a dedicated lead in the coronary sinus ( Fig. 1).…”

Intracardiac atrial defibrillation

“…Subsequent studies have confirmed the value of the SP electrode in lowering ADFTs substantially. 25,26 Sequential shocks where the first phases of each shock were delivered at a constant level (rather than unequal shocks from a single capacitor) lowered peak voltage and current even more. 26 Studies in human patients have confirmed that additional shocking electrodes and sequential defibrillation pulses lower ADFTs.…”