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A technique for postoperative application of a newly designed temporary bipolar dual-chamber pacemaker electrode
J
THoRAc CARDIOYASC SURG
89:456-458, 1985
Current Technique
A technique for postoperative application of a newly designed temporary bipolar dual-chamber pacemaker electrode Victor Parsonnet, M.D., * and Muhammad Bhatti, M.D., ** Newark, N. J.
At
the completion of a cardiac operation it is common practice to implant temporary pacing electrodes in the right atrium and the right or left ventricle. This permits pacing of the atria and ventricles, either alone or sequentially, and also the recording of myocardial electrograrns, particularly atrial, to assist in the diagnosis and treatment of certain hard-to-interpret arrhythmias. When the electrodes are no longer needed, they are either removed or cut flush with the skin and allowed to remain in place. We do not consider the latter alternative to be desirable because the retained wires may become infected and produce a draining sinus, or they may become a focus for psychological distress. Ideally, the wire must be positioned and affixed easily, must maintain satisfactory pacing and sensing thresholds for as long as needed (usually days but on occasion weeks), and must allow painless removal. We have tried a number of methods in the past, such as incorporating the electrode into the suture-ligature of the stump of the atrial appendix, affixing the wire to the epicardium with absorbable ligatures, or tangling it in the epicardium by taking V-shaped bites with the wire itself. With any of these methods there may be occasional instances of pacing or sensing failure, usually because of displacement of the electrode. Also the wire cannot always be removed. From the Departments of Surgery and Thoracic and Cardiovascular Surgery, Newark Beth Israel Medical Center, Newark, N. J. 07112. *Director of Surgery, Newark Beth Israel Medical Center, and Clinical Professor of Surgery, University of Medicine and Dentistry, New Jersey Medical School, Newark, N. J. **Chief Resident, Thoracic and Cardiovascular Surgery, Newark Beth Israel Medical Center, Newark, N. J.
456
Although one wire per chamber is often sufficient when used in combination with a remote ground wire, failure to pace or sense is common, so that for backup purposes we place two unipolar electrodes in each chamber. Two-chamber bipolar electrodes are also needed for sequential pacing, an essential mode in the postoperative state. We believe that we have simplified postoperative pacing by using a newly designed temporary bipolar electrode, held in place with absorable polydioxanone (PDS) clips.* Material and methods
The electrodes are two bared braided stainless steel wires 1 em long and 1 em apart. They are swadged 2 em from the end of a stainless steel needle, 0.032 inches in diameter with a 3jg inch long curved tapered point. The wires are electrically isolated from each other. There is one black Teflon marker between the proximal and distal electrodes. The 61 em long leads are insulated by FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene). They are swadged at the end to a Keith skin needle, which permits passage of the wire through the chest wall. Next to the needle the wires are separated from each other and each is provided with a No. 304 stainless steel tube connector to be attached to the clip-leads of an external pulse generator (Fig. 1). The atrial lead is sewn to the lateral wall of the right atrium by placement of two in-line bites (Fig. 2), each deep enough to catch the full thickness of the atrial wall. *The electrodes are produced by the Cordis Corporation, Miami, Fla.; the PDS (polydioxanone) absorbable clips (Absolok AC-200) are produced by Ethicon, Inc., Somerville, N. J.
Volume 89 Number 3 March, 1985
Temporary bipolar pacemaker electrode
457
Fig. 1. Temporary bipolar electrode wire (see text for description). Arrows indicate the electrodes themselves on each side of the blank marker.
We have found the best position to be just anterior to the interatrial groove and pulmonary veins, where the epicardium is somewhat thicker and there is little chance of tearing a thin atrium. A PDS clip (medium size) has already been placed at one end of the electrode pair to prevent the lead from being pulled too far into the heart or from advancing spontaneously at any time; a distal clip is then applied at the level of the epicardium just beyond the distal electrode. The needle and extra wire are cut off. It is not necessary to place electrodes entirely within the myocardium: They may lie partially within the myocardium or on the epicardial surface, or a combination of the two. After the pacing threshold has been tested with an external pacemaker, the distal end of the lead is passed through the skin to the right of the median sternotomy, and the lead is then affixed to the skin with an appropriate nonabsorbable suture. Redundant wire is allowed to lie within the pericardial cavity. No extra clips or sutures are needed. The skin needle is cut off next to the connectors. The ventricular wire is sewn to an avascular area of the anterior wall of the right (or left) ventricle, by means of a long single bite, as shown in Fig. 2. This lead is brought out to the left of the incision. Results Forty-four bipolar electrodes were tested, 22 in the atrium and 22 in the ventricle. Pacing thresholds were approximated at implant and explant using a Medtronic Model 5330 external atrioventricular sequential pulse generator by adjusting the gain control. The point of loss of capture was read from the gain control (more precise measurements were not made). The gain was calibrated in milliamperes; the output pulse duration was 1.8 msec.
Sensing thresholds were not measured, although inhibition during pacing was observed in the operating and recovery rooms in eight cases. The degree of difficulty of extracting the leads was judged in all cases (1+ for simple to 4+ for difficult); in 10 cases the force required to extract the electrodes was measured on a spring gauge graduated from 0 to 10 pounds. In vitro studies were performed on the test electrodes as well as several other commercially available unipolar models. They were allowed to soak in human plasma with the PDS clips applied for 3 and 7 days. * Pull-off force for removing the clip that had been applied either to the bare wire or to the Teflon insulation was measured by an Instron device. After 3 or 7 days' exposure of the electrode to plasma, the pull-off force was lower than baseline. After 7 days in plasma, no wire required more than 1,000 gm to pull it free of a clip that had been applied either to the coated or bared wire of the lead. Typical pull-off forces were 100 grn for one clip and 200 gm for two. In the past year we have used the absorbable clip method of fixation in approximately 3,600 unipolar electrode insertions. In almost every case we were able to remove the leads by the fifth or sixth postoperative day. On the rare occasion that the wire was too difficult to remove, it was left in place another day or two longer, at which time it was removqi easily. A few wires had been cut short and left in ~ace permanently before we realized that the wires would loosen a few days later; this *These studies were conducted by Ethicon, Inco Wires tested included Medtronic myocardial Lot T-201. Ethicon temporary pacing wire Lot LS-221, and Davis & Geck Flexon pacing wire Lot 259243.
458
The Journal of Thoracic and Cardiovascular Surgery
Parsonnet and Bhatti
from 0.5 to 4.0 rnA (mean 1.7 rnA); thresholds at explant in 21 cases were 1.0 to 3.0 rnA (mean 1.9). One lead apparently displaced in the early postoperative period. Sensing thresholds were satisfactory at implant in all cases but were not measured at explant. Extractions were easy (1 +) in all cases. The force required was less than 2 pounds in all cases (less than 1 pound in one case, less than 1Y2 in three cases, and less than 2 in eight). It was not measured in 10. Discussion VENTRICLE
ATRIUM
Fig. 2. Diagram of method of placing temporary bipolar leads in ventricle (top) and atrium (bottom).
practice then was abandoned and all wires were removed thereafter. Prototypes of the bipolar wires were used in 22 patients between January and August, 1984. All of the patients had standard elective' aorta-coronary bypass operations performed by one of us (V. P.). All survived the operation. The electrodes were explanted on the fifth to the eleventh postoperative day. Atrial leads. Initial pacing thresholds ranged from 0.5 to 4.5 rnA (mean 2.0 rnA); thresholds at explant in 17 cases (two unipolar when bipolar pacing was not effective) were 1.7 to 3.0 rnA (mean 2.0). In five cases thresholds could not be determined because of the presence of atrial fibrillation. Sensing was satisfactory in all eight cases in which it was tested, but it was not checked at the time of explant. All extractions were considered to be easy (I +). The force of extraction was less than 2Y2 pounds in all cases (less than 1Y2 in eight cases, less than 2 in two cases, and less than 2Yz in two). The force was not measured in 10.* Ventricular leads. Initial pacing thresholds ranged *The black Teflon marking band ca;he off in 28 of 44 leads. No untoward results were observed. The manufacturer has modified the design to avoid this problem in the future.
A new temporary bipolar electrode has been described, as well as a method of fixing it in place. This electrode has been easy and reliable to use. Two leads, rather than four, are needed; there are therefore fewer punctures of the atrium and ventricle and less surgical trauma. Only two absorbable clips need be applied to the lead after it is sewn to the heart; one of the clips is attached beforehand. The PDS clips lose strength over 5 to 11 days and become soft enough to permit the lead to slide through them. The clips remaining in situ are absorbed completely within 6 months. To attest to the safety of the PDS clips, we have seen no untoward reaction to them in more than 3,600 standard unipolar electrodes or in the 44 prototype bipolar leads. The electrodes themselves functioned well. Pacing was rarely lost in the 5 to 11 days that their progress was monitored. Only one of the ventricular leads became ineffective at 5 days, presumably because of early displacement. Two of the atrial leads could be utilized only in a unipolar configuration. (Tests on reversing the poles were not performed.) In all 17 cases tested, pacing was still functional at explant. The force required to remove the leads was judged to be minor; it was typically 1Y2 pounds, and it was less than 2Y2 pounds in all cases. After using this method with thousands of unipolar leads, and after further tests of this type of fixation with 44 newly designed bipolar pacing leads, we have found this to be the best technique for fixing temporary pacing leads to the heart. We can recommend this simple routine for postoperative cardiac pacing. PDS clips may be used for temporary fixation of unipolar or bipolar temporary electrodes. The bipolar electrodes described are preferable to unipolar ones because only two rather then four are required for effective temporary dual-chamber bipolar pacing.
THoRAc CARDIOYASC SURG
89:456-458, 1985
Current Technique
A technique for postoperative application of a newly designed temporary bipolar dual-chamber pacemaker electrode Victor Parsonnet, M.D., * and Muhammad Bhatti, M.D., ** Newark, N. J.
At
the completion of a cardiac operation it is common practice to implant temporary pacing electrodes in the right atrium and the right or left ventricle. This permits pacing of the atria and ventricles, either alone or sequentially, and also the recording of myocardial electrograrns, particularly atrial, to assist in the diagnosis and treatment of certain hard-to-interpret arrhythmias. When the electrodes are no longer needed, they are either removed or cut flush with the skin and allowed to remain in place. We do not consider the latter alternative to be desirable because the retained wires may become infected and produce a draining sinus, or they may become a focus for psychological distress. Ideally, the wire must be positioned and affixed easily, must maintain satisfactory pacing and sensing thresholds for as long as needed (usually days but on occasion weeks), and must allow painless removal. We have tried a number of methods in the past, such as incorporating the electrode into the suture-ligature of the stump of the atrial appendix, affixing the wire to the epicardium with absorbable ligatures, or tangling it in the epicardium by taking V-shaped bites with the wire itself. With any of these methods there may be occasional instances of pacing or sensing failure, usually because of displacement of the electrode. Also the wire cannot always be removed. From the Departments of Surgery and Thoracic and Cardiovascular Surgery, Newark Beth Israel Medical Center, Newark, N. J. 07112. *Director of Surgery, Newark Beth Israel Medical Center, and Clinical Professor of Surgery, University of Medicine and Dentistry, New Jersey Medical School, Newark, N. J. **Chief Resident, Thoracic and Cardiovascular Surgery, Newark Beth Israel Medical Center, Newark, N. J.
456
Although one wire per chamber is often sufficient when used in combination with a remote ground wire, failure to pace or sense is common, so that for backup purposes we place two unipolar electrodes in each chamber. Two-chamber bipolar electrodes are also needed for sequential pacing, an essential mode in the postoperative state. We believe that we have simplified postoperative pacing by using a newly designed temporary bipolar electrode, held in place with absorable polydioxanone (PDS) clips.* Material and methods
The electrodes are two bared braided stainless steel wires 1 em long and 1 em apart. They are swadged 2 em from the end of a stainless steel needle, 0.032 inches in diameter with a 3jg inch long curved tapered point. The wires are electrically isolated from each other. There is one black Teflon marker between the proximal and distal electrodes. The 61 em long leads are insulated by FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene). They are swadged at the end to a Keith skin needle, which permits passage of the wire through the chest wall. Next to the needle the wires are separated from each other and each is provided with a No. 304 stainless steel tube connector to be attached to the clip-leads of an external pulse generator (Fig. 1). The atrial lead is sewn to the lateral wall of the right atrium by placement of two in-line bites (Fig. 2), each deep enough to catch the full thickness of the atrial wall. *The electrodes are produced by the Cordis Corporation, Miami, Fla.; the PDS (polydioxanone) absorbable clips (Absolok AC-200) are produced by Ethicon, Inc., Somerville, N. J.
Volume 89 Number 3 March, 1985
Temporary bipolar pacemaker electrode
457
Fig. 1. Temporary bipolar electrode wire (see text for description). Arrows indicate the electrodes themselves on each side of the blank marker.
We have found the best position to be just anterior to the interatrial groove and pulmonary veins, where the epicardium is somewhat thicker and there is little chance of tearing a thin atrium. A PDS clip (medium size) has already been placed at one end of the electrode pair to prevent the lead from being pulled too far into the heart or from advancing spontaneously at any time; a distal clip is then applied at the level of the epicardium just beyond the distal electrode. The needle and extra wire are cut off. It is not necessary to place electrodes entirely within the myocardium: They may lie partially within the myocardium or on the epicardial surface, or a combination of the two. After the pacing threshold has been tested with an external pacemaker, the distal end of the lead is passed through the skin to the right of the median sternotomy, and the lead is then affixed to the skin with an appropriate nonabsorbable suture. Redundant wire is allowed to lie within the pericardial cavity. No extra clips or sutures are needed. The skin needle is cut off next to the connectors. The ventricular wire is sewn to an avascular area of the anterior wall of the right (or left) ventricle, by means of a long single bite, as shown in Fig. 2. This lead is brought out to the left of the incision. Results Forty-four bipolar electrodes were tested, 22 in the atrium and 22 in the ventricle. Pacing thresholds were approximated at implant and explant using a Medtronic Model 5330 external atrioventricular sequential pulse generator by adjusting the gain control. The point of loss of capture was read from the gain control (more precise measurements were not made). The gain was calibrated in milliamperes; the output pulse duration was 1.8 msec.
Sensing thresholds were not measured, although inhibition during pacing was observed in the operating and recovery rooms in eight cases. The degree of difficulty of extracting the leads was judged in all cases (1+ for simple to 4+ for difficult); in 10 cases the force required to extract the electrodes was measured on a spring gauge graduated from 0 to 10 pounds. In vitro studies were performed on the test electrodes as well as several other commercially available unipolar models. They were allowed to soak in human plasma with the PDS clips applied for 3 and 7 days. * Pull-off force for removing the clip that had been applied either to the bare wire or to the Teflon insulation was measured by an Instron device. After 3 or 7 days' exposure of the electrode to plasma, the pull-off force was lower than baseline. After 7 days in plasma, no wire required more than 1,000 gm to pull it free of a clip that had been applied either to the coated or bared wire of the lead. Typical pull-off forces were 100 grn for one clip and 200 gm for two. In the past year we have used the absorbable clip method of fixation in approximately 3,600 unipolar electrode insertions. In almost every case we were able to remove the leads by the fifth or sixth postoperative day. On the rare occasion that the wire was too difficult to remove, it was left in place another day or two longer, at which time it was removqi easily. A few wires had been cut short and left in ~ace permanently before we realized that the wires would loosen a few days later; this *These studies were conducted by Ethicon, Inco Wires tested included Medtronic myocardial Lot T-201. Ethicon temporary pacing wire Lot LS-221, and Davis & Geck Flexon pacing wire Lot 259243.
458
The Journal of Thoracic and Cardiovascular Surgery
Parsonnet and Bhatti
from 0.5 to 4.0 rnA (mean 1.7 rnA); thresholds at explant in 21 cases were 1.0 to 3.0 rnA (mean 1.9). One lead apparently displaced in the early postoperative period. Sensing thresholds were satisfactory at implant in all cases but were not measured at explant. Extractions were easy (1 +) in all cases. The force required was less than 2 pounds in all cases (less than 1 pound in one case, less than 1Y2 in three cases, and less than 2 in eight). It was not measured in 10. Discussion VENTRICLE
ATRIUM
Fig. 2. Diagram of method of placing temporary bipolar leads in ventricle (top) and atrium (bottom).
practice then was abandoned and all wires were removed thereafter. Prototypes of the bipolar wires were used in 22 patients between January and August, 1984. All of the patients had standard elective' aorta-coronary bypass operations performed by one of us (V. P.). All survived the operation. The electrodes were explanted on the fifth to the eleventh postoperative day. Atrial leads. Initial pacing thresholds ranged from 0.5 to 4.5 rnA (mean 2.0 rnA); thresholds at explant in 17 cases (two unipolar when bipolar pacing was not effective) were 1.7 to 3.0 rnA (mean 2.0). In five cases thresholds could not be determined because of the presence of atrial fibrillation. Sensing was satisfactory in all eight cases in which it was tested, but it was not checked at the time of explant. All extractions were considered to be easy (I +). The force of extraction was less than 2Y2 pounds in all cases (less than 1Y2 in eight cases, less than 2 in two cases, and less than 2Yz in two). The force was not measured in 10.* Ventricular leads. Initial pacing thresholds ranged *The black Teflon marking band ca;he off in 28 of 44 leads. No untoward results were observed. The manufacturer has modified the design to avoid this problem in the future.
A new temporary bipolar electrode has been described, as well as a method of fixing it in place. This electrode has been easy and reliable to use. Two leads, rather than four, are needed; there are therefore fewer punctures of the atrium and ventricle and less surgical trauma. Only two absorbable clips need be applied to the lead after it is sewn to the heart; one of the clips is attached beforehand. The PDS clips lose strength over 5 to 11 days and become soft enough to permit the lead to slide through them. The clips remaining in situ are absorbed completely within 6 months. To attest to the safety of the PDS clips, we have seen no untoward reaction to them in more than 3,600 standard unipolar electrodes or in the 44 prototype bipolar leads. The electrodes themselves functioned well. Pacing was rarely lost in the 5 to 11 days that their progress was monitored. Only one of the ventricular leads became ineffective at 5 days, presumably because of early displacement. Two of the atrial leads could be utilized only in a unipolar configuration. (Tests on reversing the poles were not performed.) In all 17 cases tested, pacing was still functional at explant. The force required to remove the leads was judged to be minor; it was typically 1Y2 pounds, and it was less than 2Y2 pounds in all cases. After using this method with thousands of unipolar leads, and after further tests of this type of fixation with 44 newly designed bipolar pacing leads, we have found this to be the best technique for fixing temporary pacing leads to the heart. We can recommend this simple routine for postoperative cardiac pacing. PDS clips may be used for temporary fixation of unipolar or bipolar temporary electrodes. The bipolar electrodes described are preferable to unipolar ones because only two rather then four are required for effective temporary dual-chamber bipolar pacing.