Ann Thorac Surg 2005;79:1384-1387
© 2005 The Society of Thoracic Surgeons
New technology
A New Method of Temporary Epicardial Atrioventricular Pacing Utilizing Bipolar Pacing Leads
Shafqat Hasan, FRCS(CTh)*,
C. Terence Lewis, FRCS
The South West Cardiothoracic Centre, Plymouth, United Kingdom
Accepted for publication April 14, 2004.
* Address reprint requests to Dr Hasan, Aston Cottage, Heyford Rd, Steeple Aston, Oxon, OX25 4SH UK (E-mail: faizashafqat{at}hotmail.com).
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Abstract
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PURPOSE: We evaluated a convenient method of temporary atrioventricular pacing utilizing bipolar epicardial pacing leads that offer better sensing and pacing performance.
DESCRIPTION: Fifty-one patients undergoing coronary artery bypass grafting had atrial and ventricular bipolar leads implanted. The ventricular leads were inserted onto the front of the right ventricle, and the atrial leads were inserted into the lateral muscular part of the right atrium near the interatrial groove. Sensing values, pacing thresholds, and impedance were measured on all leads on postoperative days 0, 2, and 4, and complications of insertion and removal were noted.
EVALUATION: The method was convenient and there were no complications during insertion or removal. The mean pacing threshold increased from 1.1 V to 1.5 V in both the atrial and ventricular leads from day 0 to day 4 (not significant). The mean sensed p wave amplitude decreased from 2.2 mv to 2.0 mv (not significant), and the mean sensed R wave amplitude decreased from 6.2 mv to 4.1 mv (p = 0.001) from day 0 to day 4. In spite of this significant drop in the sensed R wave amplitude, this value remained in an acceptable range. There was also a significant decrease in impedance, but overall all values were in an acceptable range assuring safe and effective pacemaker function. Only one atrial lead (2%) and three ventricular leads (6.1%) failed to pace on day 4.
CONCLUSIONS: We conclude that this temporary epicardial pacing method is safe, convenient, and less time consuming. Satisfactory pacing and sensing performance was achieved with low thresholds and minimal complications.
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Introduction
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Temporary epicardial pacing has been used in cardiac surgery since the 1960s. The ideal lead should have reliable pacing and sensing capabilities throughout the postoperative period. Also they should be easy to insert and have minimal complications. Temporary bipolar epicardial leads with their localized fixed areas offer superior sensing and pacing performance compared with the traditional multifilament wire electrodes, and their design minimizes the chances of dislodgement. Their electrical properties are important for safe pacemaker function. We evaluated this pacing method of atrioventricular pacing using bipolar leads that were implanted directly into the lateral muscular part of the right atrium near the interatrial groove and the anterior surface of the right ventricle.
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Technology
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Fifty-one consecutive patients undergoing first time coronary artery bypass grafting had bipolar leads implanted using this method. All the patients were elective cases with predominantly preserved left ventricular function, and they underwent two to four grafts on bypass utilizing moderate hypothermia. The method of myocardial protection used was either cardioplegic arrest with blood cardioplegia or cross-clamp fibrillation. Leads were implanted at the end of the procedure after discontinuation of bypass. The surgeons performing the procedure recorded ease of implantation and complications. Sensing values, pacing thresholds (at 0.5 ms pulse duration), and lead impedance (tissue resistance) was checked by an independent pacing technician on the day of implantation and also on postoperative days 2 and 4. All patients were monitored and rhythm strips were taken at the time of removal on postoperative day 4, and all removal complications were noted. There were no mortalities or serious complications; thus no patients were omitted from the study.
The atrial leads were implanted directly into the lateral muscular part of the right atrium near the interatrial groove. No suturing or atrial plication was used. The ventricular leads were implanted into the myocardium on the anterior surface of the right ventricle. The entire noninsulated part of the lead needed to be completely imbedded into the muscle.
As seen in Figure 1 the Medtronic 6495 (Medtronic, Inc, Minneapolis, MN) bipolar temporary pacing lead is a bipolar lead, which means it consists of two discrete electrodes, the distal ring electrode, and the proximal tip electrode. This means that one lead is required instead of two. Electrodes are connected to insulated multifilament leads and there is a polypropylene coil connected to the distal end of the electrodes, which is the fixing mechanism to secure the lead in place. There are atraumatic needles at both ends for implantation. The proximal one breaks into two pins for connection to the pacemaker.
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Fig 1. (1) Distal ring electrode. (2) Proximal tip electrode. (3) Insulated multifilament lead. (4) Polypropylene coil. (5, 6) Atraumatic needles at both ends. (7) Breakable pins.
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Technique
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Threshold values sensed P and R wave amplitudes and impedance are given as the mean plus or minus standard deviation in Tables 1 and 2. The student's t test was used for comparing the changes in values for a period of time. A probability value of <0.05 was considered statistically significant.
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Clinical Experience
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The group of 51 patients in the trial had a mean age of 62 years, with a male to female ratio of 6 to 1. The leads were easy to implant, and this technique was less time consuming than the traditional method, as one lead was implanted instead of two and there was no stitching involved. One ventricular lead required a stitch to stop bleeding; apart from this there were no other complications at implantation. Two atrial leads and two ventricular leads were accidentally dislodged during the course of the study.
Table 1 shows the mean sensed p wave amplitudes, atrial pacing thresholds, and impedance values recorded on postoperative days 0, 2, and 4. All three of these values were in an acceptable range assuring safe pacing function. As seen, there was no statistically significant decrease in p wave amplitude or increase in pacing threshold, but there was a significant decrease in impedance. Pacing thresholds could not be measured in 4 patients (8.1%) on days 2 and 4 because the patients were in atrial fibrillation. One (2.0%) of 51 leads failed to pace on day 4. Atrial sensitivity was found to be inadequate in 50% of the patients who developed atrial fibrillation. Phrenic nerve stimulation and twitching of the diaphragm was noted in four leads (8.1%). This problem was overcome by placing the leads slightly deeper into the atrial muscle and by ensuring that the noninsulated part of the lead electrode was completely imbedded into the muscle.
Table 2 shows the results of the ventricular lead evaluation. Again, overall the values were in an acceptable range ensuring safe pacing function. There was no statistically significant increase in the mean pacing threshold from day 0 to day 4. Although a decrease in sensed R wave amplitude and impedance was significant, the values remained in an acceptable range. Pacing threshold could not be calculated in four leads (8.1%) because the patient was in fast atrial fibrillation. Two patients (4.0%) complained of twitching of the diaphragm due to phrenic nerve stimulation. Pacing failure was seen in 3 patients (6.1%) on day 4, and intermittent sensing failure occurred in four leads (8.1%) at various times due to faulty implantation. The problem was solved again by ensuring that all of the noninsulated part of the lead was imbedded.
All surgeons found this method to be safe, convenient, and less time consuming. All wires were completely removed very easily, and there was no retained material. There were no bleeding complications. Rhythm strips recorded at the time of removal showed no sustained arrhythmias. One patient (2.0%) had three ventricular ectopic beats and 21 patients (42.8%) had one to two ventricular ectopic beats on removal of ventricular wires. Thirteen patients (26.5%) had one to two atrial ectopics on atrial wire removal.
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Comment
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Temporary pacing leads are invaluable in the diagnosis and treatment of arrhythmia after cardiac surgery. The ideal lead has reliable pacing and sensing capabilities throughout the postoperative period. Ease of handling and low complication rates are essential. The traditional method of insertion of atrial leads consists of stitching two multifilament wire electrodes to the right atrial appendage with 4-0 Prolene (Ethicon, Somerville, NJ). This can be laborious; thus a lot of surgeons only insert ventricular wires, even when atrioventricular pacing is more appropriate because atrioventricular synchrony offers better hemodynamics. Furthermore, the multifilament wire electrodes have a high failure rate both for sensing of heart activity and safe cardiac stimulation [1, 2]. Temporary epicardial leads with localized fixed surface areas offer superior sensing and pacing performance [3, 4]. The bipolar leads have been shown to have better pacing and sensing function compared with the unipolar leads. We evaluated this atrioventricular pacing method in which the bipolar leads were implanted directly into the lateral muscular part of the right atrium near the interatrial groove and the front of the right ventricle. Temporary epicardial atrial leads are more effective when leads are placed in the atrial body of the right atrium than if they are wrapped within the purse string of the right atrial appendage [5].
These leads were easy to implant as their pliable texture and small diameter provided for smooth surgical handling. They were introduced directly into the myocardium with the thin distal needle, which assured minimal surgical trauma. Only one ventricular lead required a stitch to stop bleeding and apart from that there were no other complications. This method was less time consuming than the traditional method as only one lead instead of two were inserted and no stitching or any other fixing mechanism was used, as the retaining coil fastened to the distal electrode maintained the lead position. Only two ventricular and two atrial leads were accidentally dislodged during the course of the study, which was also due to operator error as they were not properly secured to the skin. These leads were easy to remove and minimal force was needed to extract both the atrial and ventricular leads. All leads were removed completely and there was no indication of bleeding or any other complication after removal. The retaining coil did not result in any damage to the tissue. There were no reported sustained arrhythmias on removal [6], although one to two ectopic beats were recorded on removing 43% of ventricular leads and 27% of atrial leads.
The threshold for stimulation was measured in voltage at pulse duration of 0.5 ms in all the leads at days 0, 2, and 4. The mean atrial pacing threshold increased from 1.1 V to 1.5 V from day 0 to day 4. This change was not statistically significant and the thresholds remained low allowing for safe pacing function. The ventricular lead threshold also slightly increased again from a mean of 1.1 V to 1.5 V, which again was not statistically significant and allowed for safe effective pacing. Thresholds could not be measured in four atrial and four ventricular leads (8.1%) on days 2 and 4, due to patients who were in fast atrial fibrillation. Only one atrial lead (2%) and three ventricular leads (6.1%) failed to pace on day 4. The failure rate was very low, especially considering the fact that these leads were inserted by different surgeons as part of a study. Phrenic nerve stimulation was a problem with four atrial leads and two ventricular leads. This problem was eliminated by inserting the leads slightly deeper into the muscle and by ensuring that the entire non-insulated part of the lead was covered. Thus the overall pacing function of the lead was found to be satisfactory in both the atrial and ventricular positions with the thresholds remaining low for the duration of the study.
The sensed electrocardiogram amplitude of p waves in case of the atrial wire decreased from a mean of 2.2 mv to a mean of 2.0 mv from day 0 to day 4. This change was not statistically significant and was higher than 1 mv, which is considered to be the least acceptable value [1]. The mean sensed R wave in the case of the ventricular lead decreased from a mean of 6.2 mv to 4.1 mv from day 0 to day 4. This was statistically significant (p = 0.001). Still the value remained greater than the least acceptable value of 4 mv [1]. Atrial lead sensing was found to be inadequate in 50% of the 10 patients who developed fast atrial fibrillation. This function would have to be improved if this wire were to be used for atrial pacing therapies. Intermittent sensing failure occurred in four ventricular leads at various times, which was due to faulty implantation rather than any lead problem. Overall these values were comparable with values found for temporary and permanent pacemaker leads [3, 7]. The ventricular leads had a high sensitivity margin, although there was a drop in amplitude during the observed period. This drop has been observed in other studies [8, 9].
Tissue resistance of the atrial leads decreased from a mean of 971 ohms to 769 ohms and that of the ventricular lead decreased from a mean of 1,118 ohms to 809 ohms. These changes were both significant, but the values still remained in the acceptable range [3, 9] demonstrating integrity of the leads and ensuring that current drain from the generator is minimal. This is important as it ensures an adequate current waveform during cardiac stimulation and secures optimal pacemaker function.
The main limitation of this study is the absence of a control group receiving traditional pacing wires. However, this pacing method appears simple, safe, and effective, and it can be routinely used in the cardiac surgery setting.
We conclude that this temporary epicardial pacing method is safe, convenient, and less time consuming. Satisfactory pacing and sensing performance was achieved with low thresholds and minimal complications. The only aspect that was suboptimal was the inadequate atrial sensing in 50% of the patients that were in atrial fibrillation. This will have to be improved if this method is to be used for atrial pacing therapies.
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Disclosures and Freedom of Investigation
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This was part of a larger study conducted by the cardiologists in which these wires were used to monitor patients to study the onset of atrial fibrillation postoperatively. The study was funded by Dr A. J. Marshall's research fund. The authors had full control of the design of the study, methods used, outcome measurements, analysis of data, and production of the written report.
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Acknowledgments
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We would like to thank Drs A. J. Marshall and A. D. Taylor and S. L. Thorn for helping us in conducting this study by collecting data and providing technical expertise.
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Footnotes
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Disclaimer The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
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References
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- Ohm OJ, Morkid L, Skagseth E. Temporary pacemaker treatment in open heart surgeryvariation in myocardial threshold, tissue and interface impedances in man. PACE 1979;2:162-174.
- Ohm OJ, Skagseth E. Temporary pacemaker treatment in open heart surgerypre- to postoperative changes in the electrogram characteristics. PACE 1980;3:150-158.
- Breivik K, Engedal H, Segadal L, Ohm OJ. New temporary pacing lead for use after cardiac operations J Thorac Cardiovasc Surg 1982;84:787-794.[Abstract]
- Breivik K, Engedal H, Resch F, Segadal L, Ohm OJ. Bipolar atrial application of a new temporary pacing lead after cardiac operations J Thorac Cardiovasc Surg 1983;85:625-631.[Abstract]
- Samuels LE, Samuels FL, Kaufman MS, Morris RJ, Brockman SK. Temporary epicardial atrial pacing electrodesduration of effectiveness based on position. Am J Med Sci 1998;315(4):248-250.[Medline]
- Carroll KC, Reeves LM, Andersen G, et al. Risks associated with removal of ventricular epicardial pacing wires after cardiac surgery Am J Crit Care 1998;7(6):444-449.
- Ohm OJ, Breivic K, Hammer EA, Hoff PI. Intraoperatives electrical measurements during pacemaker implantation Clin Prog Pacing Electrophysiol 1984;2:1-2.
- Ohm OJ, Breivik K, Sagadal L, Engedal H. New temporary atrial and ventricular pacing leads after cardiac operations J Thorac Cardiovasc Surg 1995;110(6):1725-1731.[Abstract/Free Full Text]
- Halldorsson AO, Vigneswaran WT, Podbielski FJ, Evans DM. Electrophysiological and clinical comparison of two temporary pacing leads following cardiac surgery Pacing Clin Electrophysiol 1999;22(8):1221-1225.[Medline]
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Abstract
Introduction
