LAUSR

Right ventricular (RV) rapid pacing with a dedicated temporary pacing wire remains a stalwart technique to help stabilize cardiac position during transcatheter aortic valve replacement (TAVR), particularly with balloon expandable devices. Although rapid pacing is required for balloon expandable TAVR, the use of RV pacing has been associated with a small but recognized rate of serious morbidity [1–3]. It also necessitates an additional venous access point, which adds time and expense to the procedure. In an effort to streamline TAVR procedures and avoid attendant complications, there has been a growing interest in utilizing the required 0.03500 left ventricular (LV) delivery wire as a pacemaker [4]. Though this concept is appealing in practice, the use of existing guidewires for pacing may be challenging since such wires are not insulated against current loss in the blood pool and therefore: (1) cannot be tested for ventricular capture unless they are insulated within the body with a valvuloplasy balloon or a TAVR device; (2) cannot provide obligate pacing following TAVR without the delivery system left in place; (3) can only provide unipolar pacing in conjunction with a grounding needle in the subcutaneous tissue and a non-dedicated connection to an electrical source; and (4) generally have higher pacing capture thresholds and less safety margin due to unipolar pacing [4]. Thus, a purpose built TAVR delivery wire with intrinsic pacing system with insulated bipoles capable of consistent LV pacing at low thresholds with or without a delivery system in place may improve procedural safety and efficiency without compromising traditional pacing characteristics. We tested such a concept utilizing a series of novel Bipolar Temporary Pacing Guidewires (Vascular Solutions, Minneapolis, MN) in a swine model. These 0.035” pre-shaped wires positioned positive and negative nodes in different configurations along the distal aspect of the wire. The wire has a dedicated connector that interlocks the positive and negative outputs from a standard pacing cable to the TAVR delivery wire’s electrical contacts distally. The TAVR delivery pacing wires were tested for capture threshold in two different locations—the apex and mid-left ventricle—and with positive and negative polarities reversed sequentially. Rapid pacing ability and functionality during inflation of a 20 mm Edwards’ Sapien 3 valve delivery system (Edwards LifeSciences, Irvine, CA) was also tested. The primary objective was to demonstrate consistently acceptable rapid pacing capture thresholds and persistent pacing induced hypotension under a series of unique conditions and positions. Three separate wires were tested in a porcine model. Capture thresholds were evaluated with the wire positioned in the LV apex and mid-cavity at a rate of 130 beats per minute (bpm) using both positive and negative polarity at the distal node. Rapid pacing ability was confirmed at 180 bpm with balloon inflation. Additionally, the pacing wires were tested with the Sapien 3 delivery sheath in different positions in relation to the electrodes on the LV pacing wire. Pacing of the porcine heart was conducted with zero, one, and two of the electrodes covered. Thresholds were tested in each of these conditions and data was recorded (Table 1). As a control, unipolar LV pacing was tested in a second porcine model using an Amplatz Super Stiff (Boston Scientific, Boston, MA) and a subcutaneous ground using a 22 gauge needle in the subcutaneous tissue as previously described [4]. The wire was insulated with a 5 French AR1 diagnostic catheter. We then repeated capture threshold testing in the mid-cavity and apical LV positions and rapid pacing at 180 bpm. Among the novel bipolar wires, capture thresholds were 1.26 0.36 mA when the wire was positioned at the apex, and 1.7560.25 mA when positioned in the LV mid-cavity, out of contact with the apex. There was no meaningful difference in capture threshold based on polarity of the distal pole. Rapid pacing at 180 bpm was then successfully achieved with all wires at 23 capture threshold. We subsequently introduced an S3 delivery system and re-confirmed consistent rapid pacing ability at 23 capture threshold during delivery system inflation (Figure 1). The system appeared to be stable and capture was not lost during minor manipulations of the valve during deployment. In the control arm, capture thresholds were 6.0 and 5.0 mA with the Super Stiff wire in the mid-cavity and LV apical positions respectively. Rapid pacing at 180 bpm was also confirmed at 23 capture threshold in both positions. We report for the first time the use of a novel purpose-built 0.03500 bipolar pacing delivery guidewire (Vascular Solutions, Minneapolis, MN) designed to potentially improve the safety and efficiency profile of TAVR. Our data in a porcine model suggests capture thresholds on par with traditional temporary RV pacing wires and significantly lower than those seen with standard guidewires acting as a unipolar system in the left ventricle. Unlike standard guidewires, this wire does not require insulation in the form of an over-the-wire device to function, and therefore threshold testing can be carried out immediately after placement. Furthermore, the mechanical properties of this novel wire, including its preshaped tip (Figure 2), demonstrated no preliminary safety concerns during delivery of a balloon-expandable valve delivery system from the femoral artery to native aortic valve.