W.M. Hartung, D. Hartung, A.
Auricchio, C. Geller, A. Goette, H.-D. Esperer, S. Hobrack, H. Klein.
University Hospital Magdeburg, Department of Internal Medicine, Division of Cardiology,
Magdeburg, Germany
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BIMOS pacing allows two options of splitting the
electrical field between the three electrodes (Fig. 1): 1. "parallel splitting"
- where the two parts of the electrical field have the same direction during impuls
overlapp; 2. "opposite splitting" - where the two parts of the electrical fields
are in opposite direction. BIMOS-1 configuration uses an indifferent patch electrode as
the third electrode, whereas BIMOS-2 configuration has a third ring electrode. Figure 2
shows 6 different possibilities of electrode connections during each of the two
stimulation configurations. Configuration A and B cause an opposite splitting of the
electrical field. Current flow spreads from the middle electrode to both lateral
electrodes (A) or in the opposite direction (B). Four configurations (C, D, E, F) cause
parallel splitting. The current flow goes from one lateral electrode to both other
electrodes (C, E) or in the opposite direction (D, F). Using all electrodes, there are 6
conventional unipolar and 6 conventional bipolar pacing configurations possible. There
are, however, only two possibilities of current flow at the three different electrode
levels of the atrium.
 
Fig. 1: There are two possibilities to split an electrical field between three
electrodes. "Opposite splitting": two parts of the electrical field have the
opposite direction during overlapping. "Parallel splitting": two parts of the
electrical field have the same direction during overlapping. For details see text.
Fig. 2: Connection configurations for BIMOS-1 and BIMOS-2 pacing. BIMOS-1: an
indifferent patch electrode is used as the third electrode. BIMOS-2: a third atrial ring
electrode is used as the third electrode. With each BIMOS configuration (BIMOS-1 and
BIMOS-2) 6 different electrode connections are possible. Two configurations using an
opposite splitting (configuration A and B), four configurations using a parallel splitting
(configurations C to F). For details see text.
Animal studies: 6 female mini pigs (27.5 ± 3.5 kg) were sedated with
morphine and anesthetized thereafter with pentobarbital. Arterial pressure was
continuously monitored via a femoral arterial catheter, and leads I, II and a VF of the
surface ECG were recorded. A modified 7F VDD-Lead (CPI) containing three 1 mm atrial ring
electrodes with an interelectrode distance of 10 mm was placed under fluoroscopic guidance
via the right internal jugular vein into the right ventricle so that the ring electrodes
were floating at the level of the high and mid right atrium. A metallic indifferent
electrode (2 cm2) was placed under the skin over the right fossa
infraclavicularis. Atrial capture thresholds were measured twice at a pacing rate of 100
bpm and pulse duration of 0.5 ms using decreasing stimulus output technique.
Patient study: 28 patients undergoing routine electrophysiologic study (14
men and 14 women with a mean age of 56 ± 14 years, 16 patients with documented
supraventricular tachycardia and 12 with ventricular tachycardia) were included. A
conventional quadripolar catheter with 5 mm interelectrode distance was placed under
fluoroscopic guidance via the femoral vein into the right atrium. The ring electrodes 1
and 3 were floating in the mid right atrium. An adhesive cutaneous patch electrode (HP
M1749A) was attached over the right fossa infraclavicularis functioning as an indifferent
electrode. Atrial capture thresholds were measured twice using the decreasing stimulus
output technique for all 6 bipolar, unipolar and BIMOS-configurations. Thresholds were
measured at pacing rates of 100 bpm using identical pulse durations of 0.6 ms.
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