Guidewire Pacing Safely and Effectively Treats Bradyarrhythmias

Induced by Rheolytic Thrombectomy and Precludes the Need for Transvenous Pacing: The Scott & White Experience

ABSTRACT: Rheolytic thrombectomy (RT) is useful in certain percutaneous coronary interventions but may be associated with transient bradyarrhythmias. Clinicians have devised numerous strategies to deal with these arrhythmias apart from transvenous right ventricular pacing, some of which are described in other parts of this supplement. We report the Scott & White experience utilizing guidewire pacing to quickly and safely pace the heart in the event of bradyarrhythmia. We found this method to be safe and reliable (96.2% successful) during RT and now use this technique almost exclusively in the cardiac catheterization lab to deal with transient bradyarrhythmias during RT or due to any other cause. We also report an increased incidence of bradyarrhythmia occurring during RT when it is performed in the right coronary artery, with a trend toward an increased incidence during the clinical presentation of ST elevation myocardial infarction. J INVASIVE CARDIOL 2008;20:5A–8A Rheolytic thrombectomy (RT) using the AngioJet® System (Possis Medical, Inc., Minneapolis, Minnesota) effectively and efficiently removes intra-arterial thrombus and may lead to improved outcomes when percutaneous coronary intervention (PCI) is performed.1–5 The use of RT is associated with the transient appearance of bradyarrhythmias including sinus bradycardia, atrioventricular (AV) block and even asystole. While the mechanisms of bradyarrhythmias are not completely understood, the local release of adenosine has been postulated as a potential cause. Because of this risk, placement of a temporary transvenous pacemaker is recommended during coronary use. Recognizing the potential risks of temporary pacing in patients undergoing coronary intervention, many experienced users of RT have adopted alternative strategies for preventing or managing these bradyarrhythmias, and these are presented separately in this supplement. In 2004, we presented the alternative strategy of guidewire pacing6 that precludes the need for a transvenous pacemaker. In this article, we review our 5-year experience with this technique during RT with attention to predictors for the need of pacing, safety, effectiveness and tips for success using this technique. Methods We reviewed each case of RT performed at the Scott & White Hospital from August 2002 through December 2007 and extracted demographic, angiographic and pacing data. Peripheral and pulmonary artery cases were excluded. The first 26 cases were reported previously in our initial cohort where we showed feasibility and safety of this procedure.6 On the basis of that experience and previously published work,7,8 we adopted guidewire pacing as our preferred route of temporary pacing during PCI to include most cases of RT. Guidewire pacing procedure. After cannulation of the coronary artery ostium with a guiding catheter, a Luge™ (Boston Scientific, Natick, Massachusetts) 300-cm length, 0.014" diameter angioplasty guidewire was advanced into the distal aspect of the coronary artery. To perform guidewire pacing, 3 additional items were required: 1) an external pulse generator (Medtronic 5348, Medtronic Inc., Minneapolis, Minnesota), 2) adaptive alligator clips (Medtronic 5833SL, Medtronic Inc.) and 3) a steel monofilament suture (3-0 surgical steel monofilament B&S 30) (Figure 1). One end of the alligator clips (negative pole) was attached to the back of the coronary guidewire outside the body, while the other end (positive pole) was attached to the steel monofilament that anchored in the subcutaneous space in the groin area. (Initially, the alligator clip for the anode was attached to the skin using a large skin surface electrode. However, we found the required current unacceptably high using the skin electrode. Therefore, to improve tissue contact this was revised early in the protocol with the positive pole attached to a steel monofilament suture anchored in the subcutaneous tissue near the anesthetized access site. This steel monofilament suture is routinely used by cardiac surgeons to ground temporary epicardial pacing wires after cardiac surgery and allows lower pacemaker capture thresholds.) This allowed the guidewire to function as a single-lead unipolar pacemaker (Figure 2). Ventricular pacing was initiated at a rate faster than the underlying sinus rate and capture threshold determined by progressively lowering the output current until ventricular capture was lost. After threshold testing, the output current was set 2 to 3 times above the capture threshold output to provide a safety margin. The pacing system was then put in demand mode (most commonly at a rate of 50–60 beats per minute) or inactivated until needed. If reliable pacing was established, a temporary right ventricular pacemaker was not placed. Rheolytic thrombectomy. RT was performed by one of 4 experienced interventional cardiologists (TAM, GJD, DSG, MEL). The technique of RT was at the discretion of the operator regarding the number of passes, total duration of thrombectomy and aspiration during antegrade or retrograde catheter passage. For each case, we reviewed the procedural report to determine pacing strategy chosen, thresholds (if recorded) and need for pacing during thrombectomy. Since guidewire pacing imposes a minimal intrusion on the procedure, liberal use of pacing during RT has become our norm, avoiding frequent and recurrent inactivations of the device. Statistics. Differences in the proportions between groups were assessed with a Chi-square test. A p value Results Between August 2002 and December 2007 we performed RT during 174 procedures in 175 arteries. Among these cases, 25% (n = 43) were performed in women, and 75% (n = 132) were performed in men. The mean age of the cohort was 61 ± 12 years (range 21–86 years). Indications for RT included ST elevation acute myocardial infarction (STEMI) in 119 (68%), unstable angina (UA) or non-ST elevation MI (NSTEMI) in 45 (26%) and stable angina in 10 (6%). For each use during unstable angina, NSTEMI and stable angina, angiographic findings were consistent with thrombus at some point during the procedure. Among the 174 cases, guidewire pacing was planned and initiated before the first use of RT in 105 (60%) and pacing actually became necessary in 52% (n = 55) of these, resulting in a 33% requirement among all RT cases. The indication for pacing was the appearance of severe sinus bradycardia, high-grade AV block or asystole. Among 69 cases when guidewire pacing was not planned, significant bradyarrhythmias were seen in 2 patients after initiation of RT. One case occurred during PCI of a saphenous vein graft (SVG) supplying the right coronary artery (RCA). A FilterWire EZ™ (Boston Scientific) was in place, but capture of the ventricle was not possible. We have paced successfully through an embolic protection device wire, but we consider this unreliable and extremely dependent on position of the filter, as there is only a short section of wire extending beyond the basket to contact the arterial wall. Frequently, the entire filter and wire will lie within the vein graft, which is technically extra-cardiac. The other case involved use of RT in the left anterior descending artery (LAD) in which pre-interventional backup pacing had not been established due to perceived low likelihood of developing bradycardia. Guidewire pacing was successful in 96.2% of patients (101/105) in whom it was attempted, with only 4 instances of pacing failure. Two failures involved a native vessel intervention using a Luge wire in which adequate capture was never obtained. One of these two developed transient bradycardia during RT, which was managed with atropine and inactivation of the device. An additional failure occurred during a native vessel PCI using a Luge wire in which the initial capture threshold was adequate at 12 mA. During RT, retraction of the wire inadvertently occurred with loss of capture, emphasizing the necessity of maintaining appropriate distal wire position. While the patient did experience transient bradycardia, RT was inactivated, and the heart rate recovered spontaneously with no adverse outcome. We have found that a distal location typical of guidewire placement for routine PCI is adequate for pacing. To maintain pacing, the wire must not be allowed to slip back into the mid vessel, but excessive distal placement is not necessary and poses an unnecessary risk of vessel perforation. With placement of the guidewire in the standard distal location, the risk of vessel perforation is small, especially with the nonhydrophilic guidewires fit for pacing. The final failure involved PCI in a SVG with a SpiderFX™ (ev3 Inc., Plymouth, Minnesota) embolic protection device, in which case adequate capture could not be established, but pacing was not required during RT. A backup transvenous pacemaker was placed for RV pacing and used in 7 cases. These occurred either during our early experience when the reliability of the guidewire was uncertain or due to pre-existing bradyarrhythmias that were deemed likely to be present after the procedure thus representing a need for continued temporary pacing after leaving the catheterization lab. Predictors of the need for pacing. RT was used in the LAD (n = 47), left circumflex artery (LCX) (n = 23) and RCA (n = 80) and in 25 SVG interventions. During RT, pacing was necessary in 19%, 22% and 49% of the LAD, LCX and RCA interventions, respectively (p = 0.001). Pacing was not necessary during RT in any of the SVGs supplying the LAD or LCX distributions but was necessary in 25% of cases involving a SVG supplying the RCA distribution. Overall, the need for pacing was increased (p = 0.02) when RT was performed in the distribution of the RCA either via the native vessel or bypass graft. Pacing was necessary in 39% of cases in which RT was utilized during STEMI, 20% of cases of RT used in patients with UA/NSTEMI and only 10% of cases in which thrombus formed during PCI in a patient with stable angina (p = 0.11). A requirement for pacing during RT was not related to patient age (Table 1) and was not significantly more frequent in men compared with women (36% vs. 23%, p = 0.27). Safety. No safety issues were identified. Rarely did the patient even notice that pacing was occurring; occasionally, however, in cases in which relatively high currents were required to capture the ventricle, patients would report an electrical sensation similar to that experienced during transcutaneous pacing. Discussion In this article, we present the Scott & White experience utilizing guidewire pacing during RT to treat bradyarrhythmias when they occur, precluding the need for venous access and right ventricular pacing or premature termination of RT. Meier et al7 first described guidewire pacing in 1985. Few subsequent reports appeared in the literature.8,9 It is not mentioned in standard cardiac catheterization or interventional textbooks and seems to be a technique that is underutilized. As we expanded our experience with this technique, we learned that the pacing capabilities of different wires vary. The Luge wire, which has long served as our “workhorse” wire, is an excellent pacing wire. In our original manuscript, we tested the conduction properties of many commonly used wires and found many to be adequate for guidewire pacing.6 By performing bench-top testing on many wires, we were able to predict which wires would perform adequately for guidewire pacing. It should be noted that in the current reported series the great majority of cases were done with the Luge wire. A few cases utilizing a Platinum Plus™ (Boston Scientific) heavy support wire were also successful. Notably, a hydrophilic wire in which the tip is a long polymer sleeve, such as the Choice PT (Boston Scientific), is ineffective for pacing. In cases where such a wire is required to cross a lesion, we simply exchange (via a balloon catheter or exchange catheter) for a Luge wire or alternative acceptable wire before initiation of RT. With care and creativity, this form of pacing can be used to treat bradyarrhythmias associated with some cases of rotational atherectomy (RA). If RA is performed in the mid or distal portion of the LAD or LCX, a second guidewire can be placed in the alternative left sided artery (away from the rotating burr) and used as a temporary pacemaker.10 We also have found this technique helpful in combating the bradyarrhythmias seen during primary PCI in patients with inferior myocardial infarction, those that develop the no re-flow phenomenon and those associated with vasovagal reactions. In general, we have found wires associated with embolic protection devices inadequate for pacing, probably due to their required positioning in the SVG with minimal, if any, wire extending into the native coronary arteries. Nonetheless, a second wire could be placed in a buddy fashion beyond the filter into the native coronary artery to allow pacing. However, care would be required to assure that the buddy wire does not compromise the efficacy of the embolic protection device. Conclusion We report on the Scott & White experience with guidewire pacing as a safe and effective strategy for combating transient bradyarrhythmias associated with RT. Among the 174 coronary cases over a 5-year period, guidewire pacing was effective in 96.2% of cases attempted, was required in 33% of all cases and was associated with no apparent adverse effects. Our experience confirms that bradyarrhythmias during RT are more commonly observed when the treated vessel is the RCA or a vein graft to this territory. Additionally, there is a trend toward a higher likelihood for the development of bradyarrhythmias when RT is performed during STEMI compared with other clinical scenarios. In our practice, guidewire pacing has replaced transvenous RV pacing in nearly all cases of PCI-related bradyarrhythmias, including those associated with RT. We have shown the technique of guidewire pacing to be safe and effective. Furthermore, we believe this technique is cost effective and has the potential to reduce complications (access site complications and RV perforation), to lower barriers to wider adoption of RT utilization and to allow longer periods of thrombectomy that may prove to be more efficacious.

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