Experiences with a new myocardial electrode for permanent cardiac pacing BY STURE LARSSON
Department of Thoracic Surgery Sahlgren’s Hospital, University of Gdleboug, Gdteborg, Sweden
ABSTRACT The first experiences with a new myocardial sutureless screw-in electrode for cardiac pacing are reported. A brief description of the technique is given. The electrode can be inserted quickly and safely under direct vision through a small anterior thoracotomy using a special inserter tool. The heart can be brought under pacemaker control in less than 5 minutes. The technique was employed in 1 5 patients. Results to date are promising and it is suggested that this method should be resorted to in cases of unstable pacing or recurrent dislocation of an endocardial lead, or when there are difficulties in the proper positioning of an electrode transvenously. In Sweden endocardial electrodes for transvenous insertion predominate. In many countries, especially the U.S.A., there is extensive experience of epior myocardial pacing leads ( 2 , 4 , 5 ) . Some authors consider epicardial pacemakers safer than endocardial pacemakers for permanent cardiac pacing (8).
W e have observed defective or unstable pacing with an endocardial electrode in a high proportion of patients in our series early after the implantation and even after many years of perfect pacing. When there are problems with an endocardial lead an epi- or myocardial electrode can be used. This paper reports experiences with a new sutureless myocardial electrode (Medtronic model 6917).
44
MATERIAL The transvenous technique has been used as the first method for implantation of a stimulating electrode in patienlts with non-surgical heart block. Endocardia1 electrodes were implanted in 1973 and 1974 in 320 new pacemaker patients. Reoperation was done in 81 patients (25 per cent) du- to poor position of the electrode, recurrent dislocation, pacing or sensitivity problems, infection etc. More than two adjustments were performed in 20 caFes. In 1 5 patients where endocardial pacemaker systems did not work satisfactorily a new myocardial sutureless electrode was implanted through a small thoracotomy. There were 10 men and 5 women. The average age was 65,5 years. Three patients were above 80 years.
TECHNIQUE The electrode and the special accessories are shown in fig. 1 and fig. 2. The tip of the electrode is coated with silicone rubber except for the last 3/4 turn, which is the stimulating portion of the electrode. The electrode is screwed into the myocardium. Additional anchoring is provided by a Dacron mesh netting at the base of the electrode head. The mesh attaches to the ventricular surface by inducing connective tissue formation. The implantation technique is shown in figures 3, 4 and 5 . The electrode should b: screwed into the myo-
Pig. 1. The electrode model 5917 with a special handle which is used to screw in the electrode into the myocardium, cnd n tunneler.
Fig. 3. T h e lead is affixed to the myocardium with three clockwise turns.
Fig. 2. The electrode head mounted on the handle.
cardium during systole to avoid the risk of forcing the electrode through the myocardial wall. The selected ventricular attachment site should be an avascular area free of infarcts and fibrosis. The lead is passed subcutaneously to the pacemaker pocket with a special tunneler. A very small incision in the thoracic wall is required. The peri-
Fig. 4. The electrode head with the Dacron mesh at the base has been affixed to the myocardzum. The lead is peeled from the handle and passed using the tunneler to the pacemaker pocket.
cardium is adapted with a few sutures and the pleural cavity drained with a tube. No myocardial incision or sutures are required. 45
Fig. 6 . Chest radiogram (side view) from a patierit with an atridtriggered parema&er. Two niyocardid elertrodes. Fig. f j . A very limited anterior left-sided thorarotomy i s rryuired. The pleural cavity is drained with a rubber tube.
RESULTS An x-ray film from a patient with an atrialtriggered pacemaker is shown in fig. 6. The patient has two myocardial electrodes one of which is a reserve electrode. The detector electrode was placed in the mediastinum by mediastinoscopy. The indication for implantation of a myocardial electrode was defective pacing with an endocardial pacemaker system despite adjustment of the electrode position in 1 3 cases, and difficulties in proper positioning of an endocardial electrode in two cases. At the time of operation the threshold was 1 volt or less in 11 cases, 1-2 volts in 3 cases, and 4 volts in one case. Unipolar threshold should not exceed 2 volts. High threshold primarily may be due to the electrode having been placed in a fibrotic area of the myocardium or the electrode having been screwed in too deeply so the stimulating tip of the electrode enters the cavity of the ventricle. One patient was given an atrial-triggered pacemaker, the others QRS-triggered or QRSinhibited pacemakers. The patients have been follow up for from a few days to one year. Sensitivity problems were observed in one case. The 46
pacemaker was changed to a QRS-triggered type, which has functioned well. Defective pacing has not been observed. One patient was re-operated becauses of bleeding from at small pericardial artery. In one patienlt with a myocardial infarction proper placement of an endocardial electrode could not be achieved. There was a fall in blood pressure and the operation was discontinued. Despite intensive care she did not improve and because of very slow heart rate it was decided to implant a myocardial electrode in this poor-risk patient. There was blood in the pericardium and a perforation of the heart was found at operation, but without current bleeding. She has been observed for a few days only after the operation. One patient became severely decompensated postoperatively. H e had symtoms of a myocardial infarction and during the attempt to insert an endocardial electrode recurrent asystole occurred. The decompensation was treated successfully. The patient left hospital two months after the operation in good condition but he died suddenly one week later. Postmortem examination showed severe arteriosclerosis of the coronaries but no other finding which could explain sudden death. The other patients are alive with wellfunctioning pacemakers.
DISCUSSION lmplantaition of Medtronic’s new myocardial screw-in electrode is a very simple and rapid method of achieving stable pacing. Less than 5 minutes is required to open the chest and implant the electrode. The whole procedure takes no more than 30-40 minutes for an experienced surgeon. There is no difficulty in positioning the eleotrode properly. In the beginning we implanted two myocardial electrodes despite using a unipolar pacemaker system. Nowadays we do not implant a reserve electrode. We prefer a small thoracotomy but other approaches have been described, by which the implantation can be performed under local anaesthesia (1, 3 , 7 , 9 ) . Good experience with this type of electrode has been reported by other authors (2, 6, 7 , 9). However, the hazards of thoracotomy for the insertion of‘ permanent epicardial leads have been well documented in the litterature (2, 4, 5 , 9 ) . Based on reports in the literature and on our own experience we use the new myocardial sutureless electrode in the following indications: 1. Failure of pacing or defective sensitivity despite two adjustments of an endocardial electrode. 2. In patients who have been referred from another hospiital where the position of the endocardial lead has been adjusted twice, we perform one adjustment and if a furthed adjustment is required a myocardial electrode is implanted. 3 . If the patient has two electrodes within the heart and a further electrode is needed a myocardial electrode is used.
4. Unsatisfactory position of the endocardial electrode with the transvenous technique despite one hour’s attempt once the tip of the electrode has entered the right atrium if there are no contraindications to thoracotomy. REFERENCES 1. Calvin J. W., Stcmmer E. A,, Steedman R. A,, Con-
nolly J. E. Clinical application of parasternal mediastinotomy. Arch Surg 102:322-325, 1971.
W. M., Gage A. A,, Frederico A. J., et al. Five years’ clinical experience with an implantable pacemaker: An appraisal. Surgery 58:915-922, 1965.
2 . Chardack
3. Dixon S. H., Perryman R. A,, Morris J. J., Young W. G. Transmediastinal permanent ventricular pacing. Ann. Thorac Surg 14:206-213, 1972. 4. Dxmoyer T. L., D e Sanctis R. W., Austin W. G.
Experience with implantable pacemakers using myocardial electrodes in the management of heart block. 1967. Ann Thorac Surg 3:218-227, 5 . Furman B., Escher D. J. W., Solomon N. Experiences with myocardial and transvenous implanted cardiac 1969. pacemakers. Amer J Cardiol 23:66-72, 6. Hunter S. W., Bolduc L., Long V., Quattlebaum F. W. Technical communication. A new myocardial pacemaker lead (sutureless). Chest 63:430-433, 1973. 7. Mansnor K. A., Fleming W. H., Hatcher C. R. Initial experience with a sutureless screw-in electrode for cardiac pacing. Ann. Thorac Surg 16:127--135, 1973. 8. Morris J. J., Whalen R. E., McIntosh H. D., Thomp son H. K., Brown I. W., Young W. G. Permanent ventricular pacemakers: Comparison of transthoracic and transvenous implanation. Cirkulation 36:587597, 1967. 9. Mulch J., Pahutan P., Hehrlein F. W. Erste Erfahrungen mit einer neuen myokardialen Schrittmacherelektrode. Thoraxchir 22:113-116, 1974.
47
Department of Thoracic Surgery Sahlgren’s Hospital, University of Gdleboug, Gdteborg, Sweden
ABSTRACT The first experiences with a new myocardial sutureless screw-in electrode for cardiac pacing are reported. A brief description of the technique is given. The electrode can be inserted quickly and safely under direct vision through a small anterior thoracotomy using a special inserter tool. The heart can be brought under pacemaker control in less than 5 minutes. The technique was employed in 1 5 patients. Results to date are promising and it is suggested that this method should be resorted to in cases of unstable pacing or recurrent dislocation of an endocardial lead, or when there are difficulties in the proper positioning of an electrode transvenously. In Sweden endocardial electrodes for transvenous insertion predominate. In many countries, especially the U.S.A., there is extensive experience of epior myocardial pacing leads ( 2 , 4 , 5 ) . Some authors consider epicardial pacemakers safer than endocardial pacemakers for permanent cardiac pacing (8).
W e have observed defective or unstable pacing with an endocardial electrode in a high proportion of patients in our series early after the implantation and even after many years of perfect pacing. When there are problems with an endocardial lead an epi- or myocardial electrode can be used. This paper reports experiences with a new sutureless myocardial electrode (Medtronic model 6917).
44
MATERIAL The transvenous technique has been used as the first method for implantation of a stimulating electrode in patienlts with non-surgical heart block. Endocardia1 electrodes were implanted in 1973 and 1974 in 320 new pacemaker patients. Reoperation was done in 81 patients (25 per cent) du- to poor position of the electrode, recurrent dislocation, pacing or sensitivity problems, infection etc. More than two adjustments were performed in 20 caFes. In 1 5 patients where endocardial pacemaker systems did not work satisfactorily a new myocardial sutureless electrode was implanted through a small thoracotomy. There were 10 men and 5 women. The average age was 65,5 years. Three patients were above 80 years.
TECHNIQUE The electrode and the special accessories are shown in fig. 1 and fig. 2. The tip of the electrode is coated with silicone rubber except for the last 3/4 turn, which is the stimulating portion of the electrode. The electrode is screwed into the myocardium. Additional anchoring is provided by a Dacron mesh netting at the base of the electrode head. The mesh attaches to the ventricular surface by inducing connective tissue formation. The implantation technique is shown in figures 3, 4 and 5 . The electrode should b: screwed into the myo-
Pig. 1. The electrode model 5917 with a special handle which is used to screw in the electrode into the myocardium, cnd n tunneler.
Fig. 3. T h e lead is affixed to the myocardium with three clockwise turns.
Fig. 2. The electrode head mounted on the handle.
cardium during systole to avoid the risk of forcing the electrode through the myocardial wall. The selected ventricular attachment site should be an avascular area free of infarcts and fibrosis. The lead is passed subcutaneously to the pacemaker pocket with a special tunneler. A very small incision in the thoracic wall is required. The peri-
Fig. 4. The electrode head with the Dacron mesh at the base has been affixed to the myocardzum. The lead is peeled from the handle and passed using the tunneler to the pacemaker pocket.
cardium is adapted with a few sutures and the pleural cavity drained with a tube. No myocardial incision or sutures are required. 45
Fig. 6 . Chest radiogram (side view) from a patierit with an atridtriggered parema&er. Two niyocardid elertrodes. Fig. f j . A very limited anterior left-sided thorarotomy i s rryuired. The pleural cavity is drained with a rubber tube.
RESULTS An x-ray film from a patient with an atrialtriggered pacemaker is shown in fig. 6. The patient has two myocardial electrodes one of which is a reserve electrode. The detector electrode was placed in the mediastinum by mediastinoscopy. The indication for implantation of a myocardial electrode was defective pacing with an endocardial pacemaker system despite adjustment of the electrode position in 1 3 cases, and difficulties in proper positioning of an endocardial electrode in two cases. At the time of operation the threshold was 1 volt or less in 11 cases, 1-2 volts in 3 cases, and 4 volts in one case. Unipolar threshold should not exceed 2 volts. High threshold primarily may be due to the electrode having been placed in a fibrotic area of the myocardium or the electrode having been screwed in too deeply so the stimulating tip of the electrode enters the cavity of the ventricle. One patient was given an atrial-triggered pacemaker, the others QRS-triggered or QRSinhibited pacemakers. The patients have been follow up for from a few days to one year. Sensitivity problems were observed in one case. The 46
pacemaker was changed to a QRS-triggered type, which has functioned well. Defective pacing has not been observed. One patient was re-operated becauses of bleeding from at small pericardial artery. In one patienlt with a myocardial infarction proper placement of an endocardial electrode could not be achieved. There was a fall in blood pressure and the operation was discontinued. Despite intensive care she did not improve and because of very slow heart rate it was decided to implant a myocardial electrode in this poor-risk patient. There was blood in the pericardium and a perforation of the heart was found at operation, but without current bleeding. She has been observed for a few days only after the operation. One patient became severely decompensated postoperatively. H e had symtoms of a myocardial infarction and during the attempt to insert an endocardial electrode recurrent asystole occurred. The decompensation was treated successfully. The patient left hospital two months after the operation in good condition but he died suddenly one week later. Postmortem examination showed severe arteriosclerosis of the coronaries but no other finding which could explain sudden death. The other patients are alive with wellfunctioning pacemakers.
DISCUSSION lmplantaition of Medtronic’s new myocardial screw-in electrode is a very simple and rapid method of achieving stable pacing. Less than 5 minutes is required to open the chest and implant the electrode. The whole procedure takes no more than 30-40 minutes for an experienced surgeon. There is no difficulty in positioning the eleotrode properly. In the beginning we implanted two myocardial electrodes despite using a unipolar pacemaker system. Nowadays we do not implant a reserve electrode. We prefer a small thoracotomy but other approaches have been described, by which the implantation can be performed under local anaesthesia (1, 3 , 7 , 9 ) . Good experience with this type of electrode has been reported by other authors (2, 6, 7 , 9). However, the hazards of thoracotomy for the insertion of‘ permanent epicardial leads have been well documented in the litterature (2, 4, 5 , 9 ) . Based on reports in the literature and on our own experience we use the new myocardial sutureless electrode in the following indications: 1. Failure of pacing or defective sensitivity despite two adjustments of an endocardial electrode. 2. In patients who have been referred from another hospiital where the position of the endocardial lead has been adjusted twice, we perform one adjustment and if a furthed adjustment is required a myocardial electrode is implanted. 3 . If the patient has two electrodes within the heart and a further electrode is needed a myocardial electrode is used.
4. Unsatisfactory position of the endocardial electrode with the transvenous technique despite one hour’s attempt once the tip of the electrode has entered the right atrium if there are no contraindications to thoracotomy. REFERENCES 1. Calvin J. W., Stcmmer E. A,, Steedman R. A,, Con-
nolly J. E. Clinical application of parasternal mediastinotomy. Arch Surg 102:322-325, 1971.
W. M., Gage A. A,, Frederico A. J., et al. Five years’ clinical experience with an implantable pacemaker: An appraisal. Surgery 58:915-922, 1965.
2 . Chardack
3. Dixon S. H., Perryman R. A,, Morris J. J., Young W. G. Transmediastinal permanent ventricular pacing. Ann. Thorac Surg 14:206-213, 1972. 4. Dxmoyer T. L., D e Sanctis R. W., Austin W. G.
Experience with implantable pacemakers using myocardial electrodes in the management of heart block. 1967. Ann Thorac Surg 3:218-227, 5 . Furman B., Escher D. J. W., Solomon N. Experiences with myocardial and transvenous implanted cardiac 1969. pacemakers. Amer J Cardiol 23:66-72, 6. Hunter S. W., Bolduc L., Long V., Quattlebaum F. W. Technical communication. A new myocardial pacemaker lead (sutureless). Chest 63:430-433, 1973. 7. Mansnor K. A., Fleming W. H., Hatcher C. R. Initial experience with a sutureless screw-in electrode for cardiac pacing. Ann. Thorac Surg 16:127--135, 1973. 8. Morris J. J., Whalen R. E., McIntosh H. D., Thomp son H. K., Brown I. W., Young W. G. Permanent ventricular pacemakers: Comparison of transthoracic and transvenous implanation. Cirkulation 36:587597, 1967. 9. Mulch J., Pahutan P., Hehrlein F. W. Erste Erfahrungen mit einer neuen myokardialen Schrittmacherelektrode. Thoraxchir 22:113-116, 1974.
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