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Helifix, an electrode suitable for transvenous atrial and ventricular implantation
J
THORAC CARDIOVASC SURG
80:794-799, 1980
Helifix, an electrode suitable for transvenous atrial and ventricular implantation The Helifix endocardial fixation lead can be screwed in between the trabeculae of the right ventricle or the right atrial appendage. The lead was used for ventricular stimulation in 30 patients. In seven of them, the Helifix electrode was used because of dislocation of other leads and in eight patients because acceptable threshold levels could not be obtained with other electrodes. In six patients the Helifix lead had to be inserted in the proximal part of the right ventricle and in one patient in the outflow tract. One patient required replacement of the Helifix lead after 6 weeks because of an excessive threshold rise. There was only one instance of electrode dislodgment (I hour after implantation) in the 30 patients. In 20 patients the Helifix lead was implanted in the right atrial appendage with the aid of a new double stylet. There was no instance of electrode dislodgment or any other complications in the 20 patients. The Helifix lead is therefore recommended as an atrial electrode. This lead is also suitable in patients with frequent dislocations and for better fixation to other parts of the right ventricle than the apex.
Leif Bergdahl, M.D., Stockholm, Sweden
Because of a high incidence of lead dislodgments with ventricular electrodes without anchoring devices, the Helifix fixation lead was introduced at our clinic in March, 1978. Atrial pacing has been performed with J-shaped electrodes in the right atrial appendage or special leads positioned in the coronary sinus. I-a Our experience with the J-shaped electrode, however, has been limited to a few cases. The Helifix lead also can be introduced into the right atrial appendage via the saphenous, the cephalic, or the jugular vein with the aid of a special double-lumen stylet." However, experience with the Helifix electrode for atrial pacing and sensing also has been very limited and the special stylet has been used in only one patient. 4 The results with the Helifix electrode in the first 50 patients at our clinic are reported in the present study.
Material and methods Description of the Helifix lead. The Helifix endocardial lead (Fig. I) was developed by Babotai and From the Thoracic Surgical Clinic, Karolinska Sjukhuset, S-10401, Stockholm. Received for publication May 20, 1980. Accepted for publication July 16, 1980. Address for reprints: Dr. Leif Bergdahl, Department of Surgery, University of Alabama, University Station, Birmingham, Ala. 35294.
794
colleagues I for ventricular stimulation. This lead was specially designed to reduce the risk of lead dislodgment. The helical shape of the electrode makes it possible to screw it in between the trabeculae by clockwise rotation (Fig. 2) for a nontraumatic fixation to reduce postoperative threshold rises. The conductor of the lead is made of Elgiloy and is covered with silicone rubber. The electrode is made from 0.4 mm wire of platinumiridium (90%-10%) (Fig. 3). The spiral has an extended diameter of 2.7 mrn, and the distance between the coils is 1.5 mm. The stimulation area was 23 mrn'' in the first eight patients in this series and 12 mrn- in the remaining 42 patients. Description of the double stylet. A double stylet has been developed by Vitatron (Vitatron Medical B. V., Dieren, The Netherlands). This stylet consists of a hollow straight outer stylet with a diameter of 0.7 mm and a second movable inner stylet. When the inner stylet is pushed out of the straight outer stylet it assumes a J-shape (Figs. 4 and 5). The outer stylet has a small cylinder to provide a firm grip. The inner stylet ends in a thin rod with which it can be pushed forward or retracted. The outer stylet is 67.5 em long and the inner one is about 7 em longer (excluding the rod).
Clinical series Ventricular implantation. During a 2 year period (March, 1978, to February, 1980), the 23 mm'' lead
0022-5223/80/110794+06$00.60/0 © 1980 The C. V. Mosby Co.
Volume 80 Number 5 November, 1980
was used in eight patients and the 12 mrn" lead in 22 patients for ventricular pacing . (In one other patient the Helifix lead was used in the atrium and ventricle for an atrial-triggered pacemaker.) The Helifix lead was used in 13 routine cases, because of dislocation of other leads without anchoring devices in seven cases , and because acceptable threshold values could not be obtained with other electrodes in eight cases . Atrial fibrillation developed in two patients when the lead was manipulated in the right atrium in order to be placed in the appendage. Measurements of P-wave potentials and pacing thresholds were impossible becau se of persisting atrial fibrillation; therefore the Helifix lead was implanted in the right ventricle instead. There were 16 men with a mean age of 69 years (range 54 to 77 years) and 14 women with a mean age of 72 years (range 50 to 86 years). The indication for operation was complete heart block in 19 patients, sinus bradycardia in six, and sick sinus syndrome in five . The route of insertion was the right cephalic vein in 26 patients, the right external jugular vein in three, and the right internal jugular vein in one patient. The pacemaker was implanted subcutaneously in the pectoral region in 29 patients and in the abdominal region in one patient. The Helifix lead was screwed in between the trabeculae of the apex of the right ventricle in 23 patients. In six patients acceptable threshold values could not be obtained in the apical region despite multiple repositionings. In these patients the electrode was screwed in in the proximal part of the right ventricle just distal to the tricuspid valve (Fig . 6). One patient had had exit block with three earlier electrodes in the apex of the right ventricle. Acceptable threshold values could not be obtained in the apex or the proximal part of the right ventricle, and therefore the Helifix lead had to be implanted in the outflow tract of the right ventricle (Fig. 7). The Helifix lead could be used in all the patients in whom it was tried . Atrial implantation. The Helifix lead was implanted in ( 18 cases) or near the base (two cases ) of the right atrial appendage with the aid of the special stylet during the period May, 1979, to February, 1980. The electrode was positioned between the trabeculae by manipulating the stylet cylinder and, if necessary, altering the J-shape by partially retracting the inner stylet (Fig. 8). The Helifix lead was anchored to the trabeculae by turning it clockwise about three times while holding the cylinder with the free hand. A stable position was unaffected by deep breathing and coughing. The electrode was introduced via the right cephalic vein in six patients. In two other patients in whom the
Helifix endocardial fixation lead
795
Fig. 1. The Helifix lead.
Fig. 2. The Helifix electrode between the trabeculae .
cephalic vein was used, atrial fibrillation developed and the Helifix lead had to be positioned in the right ventricle . Thereafter the route of insertion was changed and the Helifix lead was introduced via the right external jugular vein in three patients and the right internal jugular vein in II patients. I recommend using the external (when possible) or internal jugular vein approach for all types of atrial electrodes. There were 13 women and
79 6
The Journal of Thoracic and Cardiovascular Surgery
Bergdahl
Stainless steel 316
Ha la r
Platinum iridi um (90%-10 %)
Silicone rubber
E igiloy w ire
Stainless steel 316 L
- - T"
I
;>.7 mm '
--
-
----
5mm
7 mm
-
-
-
-
~
I
10 mm
Fig . 3. Helifix electrode with surface area of 12 mm",
,I
"--------~:'-----~
,
. .t-~
§
!--==~c===o
""j ti
1/
"
Fig. 4. Atrium stylet in normal position and with extruding inner stylet.
Table I. Data on 13 pati ents with Helifix electrode implanted in the right atrial appendage for atrial pacing Sex . age F.68 F.5 1 F.60 F.66 M . 76 M .75 F. 74 M.68 F. 79 F. 77 F. 70 F.49 F. 77
Route of insertion Cephalic Cephalic El V Cephalic Cephalic IJV Cephalic IJV Cephalic IJV El V IJ V IJ V
vein vein vein vein vein vein
Diagnosis SA block Sinus bradycar dia SA block Sinus bradycardia Sinus bradycard ia Sinus arrest SA block Sinus bradycardia Sinus arrest SA block SA block Sinus bradycardia Brady-tachycardia sy ndro me
Legend: ElY , External jugular vein, IlY . Internal jugular vein.
Pswave
Voltage threshold ( V)
ampl itude (mV)
Pulse generator
0 .8 1.5 0 .9 0 .7 0 .6 0 ,5 0 ,6 1.2 0.9 0.8 1.5 1.2 1.7
1.8 3.5 2. 1 2.7 5.0 1.5 3.6 2.4 2.2 3.0 1.5 2.3 0 .8
Vitatron S 61 Cordis 190 E Cordis 190 E Cordis 190 E Cordis 190 E Interrnedics 253 Vitatron S 6 1 Interrnedics 253 Interrnedics 253 Intermedi cs 253 lntermedi cs 253 lntermed ics 253 Intermed ics 253
Volume 80
Helifix endocardial fixation lead
Number 5
7 97
November, 1980
Fig. 5. The l-shape of the Helifix electrode. seven men in this group . The mean age for women was 66 years (range 49 to 79 years) and that for men, 68 years (range 62 to 76 years) . The Helifix lead was used for atrial pacing in 13 patients (Table I). In seven patients with atrioventricular block the Helifix lead was used as an atrial lead for atrial-triggered pacemakers (Table II) . Results Ventricular implantation. The average threshold value 5 to 10 minutes after fixation (pulse duration 1.0 msec) was 0 .91 V (range 0 .6 to 1.5 V) in eight patients with the 23 rnm" electrode. (Threshold measurements were made with Elema-Schonander Troskelvardesrnatare.) The average threshold value in 22 patients with the 12 mm- lead 5 to 10 minutes after fixation was 0.81 V (range 0.35 to 1.9 V) . The stimulation thresholds measured immediately after implantation were generalIy higher and decreased about 50 % after IO minutes . One patient died of cardiac infarction after 5 weeks and another died of carcinoma after 15 months. There was only one instance of electrode dislodgment ( I hour
Fig. 6. Postoperative chest film showing the Elema lead at the apex of the right ventricle and the Helifix leadjust distal to the tricuspid valve. This patient had been operated upon earlier with resection of a left ventricular aneurysm and patch closure of a postinfarction ventricular septal defect. Table II. Data on seven patients with atrial-triggered pacemakers Pswave Sex, age
P,66 M,65 P.62 M,62 P,58 M,66 M,66
amplitude (mVj
BY BY BY IJY IJY BY ElY
0.9 1.8 2.2 6.0 7.0 3.3 2.3
Elema Elema Elema Elema Elema Elema
Helifix
For legend see Table I.
Table III. Threshold measurements in eight patients with the 23 mm? lead and eight patients with the 12 mmi lead Electrode area
23 rnm! 12 mm"
After J yr
0.91 Y (0.6- 1.5) 0.86 Y (0.5- 1.4)
42% (23-90) 30% (10-50)
38% (25-72%) 36% (18-60)
35% (20-45) 38% (25-65)
The Journal of
798
Ber gdahl
Thoracic and Cardiovascular Surgery
Fig. 7. The Helifix lead in the outflow tract of the right ventricle and Elema leads in the apex.
Fig. 8. Lateral roentgenogram of the thorax showing the Helifix lead in the right atrial appendage.
after fixation) among 30 patients during the follow-up period . One patient required replacement of the Helifix lead after 6 weeks because of excessive threshold rise. This patient had had a similar rise earlier with an electrode without an anchoring device. The first 16 consecutive patients received Vitatron pacemakers, and thus the relative stimulation thresholds could be monitored with the Vitatron MPA I pacemaker analyzer. One patient with a septal cardiac infarction preoperatively had a rise in threshold up to 90 % after 2 weeks . The threshold thereafter declined to 40% after 5 months and wa s 48 % after I year. The pacemaker was functioning well during the whole follow-up period. The remaining patients (except one who died of cardiac infarction after 5 weeks) were all followed for a minimum of I year. All the patients had acceptable threshold values during the follow-up period (mean period 15 months , range 12 to 25 months) (Table III) . Atrial implantation. In 20 patients the Helifix electrode was implanted in the right atrial appendage (or near the ba se of it) with the aid of the double stylet. In two patients this was not possible because of the onset
of atrial fibrillation with movement of the lead . No fibrillation was seen when the Helifix electrode was screwed into position in the whole series . The average voltage threshold at implantation in 13 patients with atrial pacing was 0.99 V (range 0.5 to 1.7 V). These thresholds were measured 5 to to minutes after fixation. P-wave amplitudes were measured from intracavitary electrograms. The average amplitude measured from peak to peak in 20 patients was 2.8 m V (range 0.8 to 7 .0 m V) (Tables I and II) . All recorded P waves showed an injury pattern with ele vations of the P-Ta segment. There were no instances of electrode dislodgment or any other complications, such as penetration or thrombosis, in the 20 patients. The relative or absolute stimulation thresholds have been acceptable in all the patients during the short follow-up period (average period 5 months, range I to II months) . REFERENCES Kleinert M, Bock M, Wilhelmi L: Clinical use of a new transvenous atrial lead. Am J Cardiol 40:237-242, 1977 2 Moss AJ, Rivers RJ: Atrial pacing from the coronary vein.
Volume 80 Number 5
Helifix endocardial fixation lead
799
November. 1980
Ten year experience in 50 patients with implanted pervenous pacemakers. Circulation 57: 103-106, 1978 3 Smyth NPD, Citron P, Keshishian 1M, Garcia 1M, Kelly LC: Permanent pervenous atrial sensing and pacing with a new f-shaped lead. 1 THoRAc CARDIOVASC SURG 72:565-
570, 1976 4 EI Gamal M, van Gelder B: Preliminary experience with
the Helifix electrode for transvenous atrial implantation. PACE 2:444-454, 1979 5 Babotai I, Meier WE, Scholzel E: Tierexperimentelle Erfahrungen mit einer neuen intrakardialen PacemakerElektrode. Langenbecks Arch Chir (Suppl Chir Forum)
144-147, 1976
THORAC CARDIOVASC SURG
80:794-799, 1980
Helifix, an electrode suitable for transvenous atrial and ventricular implantation The Helifix endocardial fixation lead can be screwed in between the trabeculae of the right ventricle or the right atrial appendage. The lead was used for ventricular stimulation in 30 patients. In seven of them, the Helifix electrode was used because of dislocation of other leads and in eight patients because acceptable threshold levels could not be obtained with other electrodes. In six patients the Helifix lead had to be inserted in the proximal part of the right ventricle and in one patient in the outflow tract. One patient required replacement of the Helifix lead after 6 weeks because of an excessive threshold rise. There was only one instance of electrode dislodgment (I hour after implantation) in the 30 patients. In 20 patients the Helifix lead was implanted in the right atrial appendage with the aid of a new double stylet. There was no instance of electrode dislodgment or any other complications in the 20 patients. The Helifix lead is therefore recommended as an atrial electrode. This lead is also suitable in patients with frequent dislocations and for better fixation to other parts of the right ventricle than the apex.
Leif Bergdahl, M.D., Stockholm, Sweden
Because of a high incidence of lead dislodgments with ventricular electrodes without anchoring devices, the Helifix fixation lead was introduced at our clinic in March, 1978. Atrial pacing has been performed with J-shaped electrodes in the right atrial appendage or special leads positioned in the coronary sinus. I-a Our experience with the J-shaped electrode, however, has been limited to a few cases. The Helifix lead also can be introduced into the right atrial appendage via the saphenous, the cephalic, or the jugular vein with the aid of a special double-lumen stylet." However, experience with the Helifix electrode for atrial pacing and sensing also has been very limited and the special stylet has been used in only one patient. 4 The results with the Helifix electrode in the first 50 patients at our clinic are reported in the present study.
Material and methods Description of the Helifix lead. The Helifix endocardial lead (Fig. I) was developed by Babotai and From the Thoracic Surgical Clinic, Karolinska Sjukhuset, S-10401, Stockholm. Received for publication May 20, 1980. Accepted for publication July 16, 1980. Address for reprints: Dr. Leif Bergdahl, Department of Surgery, University of Alabama, University Station, Birmingham, Ala. 35294.
794
colleagues I for ventricular stimulation. This lead was specially designed to reduce the risk of lead dislodgment. The helical shape of the electrode makes it possible to screw it in between the trabeculae by clockwise rotation (Fig. 2) for a nontraumatic fixation to reduce postoperative threshold rises. The conductor of the lead is made of Elgiloy and is covered with silicone rubber. The electrode is made from 0.4 mm wire of platinumiridium (90%-10%) (Fig. 3). The spiral has an extended diameter of 2.7 mrn, and the distance between the coils is 1.5 mm. The stimulation area was 23 mrn'' in the first eight patients in this series and 12 mrn- in the remaining 42 patients. Description of the double stylet. A double stylet has been developed by Vitatron (Vitatron Medical B. V., Dieren, The Netherlands). This stylet consists of a hollow straight outer stylet with a diameter of 0.7 mm and a second movable inner stylet. When the inner stylet is pushed out of the straight outer stylet it assumes a J-shape (Figs. 4 and 5). The outer stylet has a small cylinder to provide a firm grip. The inner stylet ends in a thin rod with which it can be pushed forward or retracted. The outer stylet is 67.5 em long and the inner one is about 7 em longer (excluding the rod).
Clinical series Ventricular implantation. During a 2 year period (March, 1978, to February, 1980), the 23 mm'' lead
0022-5223/80/110794+06$00.60/0 © 1980 The C. V. Mosby Co.
Volume 80 Number 5 November, 1980
was used in eight patients and the 12 mrn" lead in 22 patients for ventricular pacing . (In one other patient the Helifix lead was used in the atrium and ventricle for an atrial-triggered pacemaker.) The Helifix lead was used in 13 routine cases, because of dislocation of other leads without anchoring devices in seven cases , and because acceptable threshold values could not be obtained with other electrodes in eight cases . Atrial fibrillation developed in two patients when the lead was manipulated in the right atrium in order to be placed in the appendage. Measurements of P-wave potentials and pacing thresholds were impossible becau se of persisting atrial fibrillation; therefore the Helifix lead was implanted in the right ventricle instead. There were 16 men with a mean age of 69 years (range 54 to 77 years) and 14 women with a mean age of 72 years (range 50 to 86 years). The indication for operation was complete heart block in 19 patients, sinus bradycardia in six, and sick sinus syndrome in five . The route of insertion was the right cephalic vein in 26 patients, the right external jugular vein in three, and the right internal jugular vein in one patient. The pacemaker was implanted subcutaneously in the pectoral region in 29 patients and in the abdominal region in one patient. The Helifix lead was screwed in between the trabeculae of the apex of the right ventricle in 23 patients. In six patients acceptable threshold values could not be obtained in the apical region despite multiple repositionings. In these patients the electrode was screwed in in the proximal part of the right ventricle just distal to the tricuspid valve (Fig . 6). One patient had had exit block with three earlier electrodes in the apex of the right ventricle. Acceptable threshold values could not be obtained in the apex or the proximal part of the right ventricle, and therefore the Helifix lead had to be implanted in the outflow tract of the right ventricle (Fig. 7). The Helifix lead could be used in all the patients in whom it was tried . Atrial implantation. The Helifix lead was implanted in ( 18 cases) or near the base (two cases ) of the right atrial appendage with the aid of the special stylet during the period May, 1979, to February, 1980. The electrode was positioned between the trabeculae by manipulating the stylet cylinder and, if necessary, altering the J-shape by partially retracting the inner stylet (Fig. 8). The Helifix lead was anchored to the trabeculae by turning it clockwise about three times while holding the cylinder with the free hand. A stable position was unaffected by deep breathing and coughing. The electrode was introduced via the right cephalic vein in six patients. In two other patients in whom the
Helifix endocardial fixation lead
795
Fig. 1. The Helifix lead.
Fig. 2. The Helifix electrode between the trabeculae .
cephalic vein was used, atrial fibrillation developed and the Helifix lead had to be positioned in the right ventricle . Thereafter the route of insertion was changed and the Helifix lead was introduced via the right external jugular vein in three patients and the right internal jugular vein in II patients. I recommend using the external (when possible) or internal jugular vein approach for all types of atrial electrodes. There were 13 women and
79 6
The Journal of Thoracic and Cardiovascular Surgery
Bergdahl
Stainless steel 316
Ha la r
Platinum iridi um (90%-10 %)
Silicone rubber
E igiloy w ire
Stainless steel 316 L
- - T"
I
;>.7 mm '
--
-
----
5mm
7 mm
-
-
-
-
~
I
10 mm
Fig . 3. Helifix electrode with surface area of 12 mm",
,I
"--------~:'-----~
,
. .t-~
§
!--==~c===o
""j ti
1/
"
Fig. 4. Atrium stylet in normal position and with extruding inner stylet.
Table I. Data on 13 pati ents with Helifix electrode implanted in the right atrial appendage for atrial pacing Sex . age F.68 F.5 1 F.60 F.66 M . 76 M .75 F. 74 M.68 F. 79 F. 77 F. 70 F.49 F. 77
Route of insertion Cephalic Cephalic El V Cephalic Cephalic IJV Cephalic IJV Cephalic IJV El V IJ V IJ V
vein vein vein vein vein vein
Diagnosis SA block Sinus bradycar dia SA block Sinus bradycardia Sinus bradycard ia Sinus arrest SA block Sinus bradycardia Sinus arrest SA block SA block Sinus bradycardia Brady-tachycardia sy ndro me
Legend: ElY , External jugular vein, IlY . Internal jugular vein.
Pswave
Voltage threshold ( V)
ampl itude (mV)
Pulse generator
0 .8 1.5 0 .9 0 .7 0 .6 0 ,5 0 ,6 1.2 0.9 0.8 1.5 1.2 1.7
1.8 3.5 2. 1 2.7 5.0 1.5 3.6 2.4 2.2 3.0 1.5 2.3 0 .8
Vitatron S 61 Cordis 190 E Cordis 190 E Cordis 190 E Cordis 190 E Interrnedics 253 Vitatron S 6 1 Interrnedics 253 Interrnedics 253 Intermedi cs 253 lntermedi cs 253 lntermed ics 253 Intermed ics 253
Volume 80
Helifix endocardial fixation lead
Number 5
7 97
November, 1980
Fig. 5. The l-shape of the Helifix electrode. seven men in this group . The mean age for women was 66 years (range 49 to 79 years) and that for men, 68 years (range 62 to 76 years) . The Helifix lead was used for atrial pacing in 13 patients (Table I). In seven patients with atrioventricular block the Helifix lead was used as an atrial lead for atrial-triggered pacemakers (Table II) . Results Ventricular implantation. The average threshold value 5 to 10 minutes after fixation (pulse duration 1.0 msec) was 0 .91 V (range 0 .6 to 1.5 V) in eight patients with the 23 rnm" electrode. (Threshold measurements were made with Elema-Schonander Troskelvardesrnatare.) The average threshold value in 22 patients with the 12 mm- lead 5 to 10 minutes after fixation was 0.81 V (range 0.35 to 1.9 V) . The stimulation thresholds measured immediately after implantation were generalIy higher and decreased about 50 % after IO minutes . One patient died of cardiac infarction after 5 weeks and another died of carcinoma after 15 months. There was only one instance of electrode dislodgment ( I hour
Fig. 6. Postoperative chest film showing the Elema lead at the apex of the right ventricle and the Helifix leadjust distal to the tricuspid valve. This patient had been operated upon earlier with resection of a left ventricular aneurysm and patch closure of a postinfarction ventricular septal defect. Table II. Data on seven patients with atrial-triggered pacemakers Pswave Sex, age
P,66 M,65 P.62 M,62 P,58 M,66 M,66
amplitude (mVj
BY BY BY IJY IJY BY ElY
0.9 1.8 2.2 6.0 7.0 3.3 2.3
Elema Elema Elema Elema Elema Elema
Helifix
For legend see Table I.
Table III. Threshold measurements in eight patients with the 23 mm? lead and eight patients with the 12 mmi lead Electrode area
23 rnm! 12 mm"
After J yr
0.91 Y (0.6- 1.5) 0.86 Y (0.5- 1.4)
42% (23-90) 30% (10-50)
38% (25-72%) 36% (18-60)
35% (20-45) 38% (25-65)
The Journal of
798
Ber gdahl
Thoracic and Cardiovascular Surgery
Fig. 7. The Helifix lead in the outflow tract of the right ventricle and Elema leads in the apex.
Fig. 8. Lateral roentgenogram of the thorax showing the Helifix lead in the right atrial appendage.
after fixation) among 30 patients during the follow-up period . One patient required replacement of the Helifix lead after 6 weeks because of excessive threshold rise. This patient had had a similar rise earlier with an electrode without an anchoring device. The first 16 consecutive patients received Vitatron pacemakers, and thus the relative stimulation thresholds could be monitored with the Vitatron MPA I pacemaker analyzer. One patient with a septal cardiac infarction preoperatively had a rise in threshold up to 90 % after 2 weeks . The threshold thereafter declined to 40% after 5 months and wa s 48 % after I year. The pacemaker was functioning well during the whole follow-up period. The remaining patients (except one who died of cardiac infarction after 5 weeks) were all followed for a minimum of I year. All the patients had acceptable threshold values during the follow-up period (mean period 15 months , range 12 to 25 months) (Table III) . Atrial implantation. In 20 patients the Helifix electrode was implanted in the right atrial appendage (or near the ba se of it) with the aid of the double stylet. In two patients this was not possible because of the onset
of atrial fibrillation with movement of the lead . No fibrillation was seen when the Helifix electrode was screwed into position in the whole series . The average voltage threshold at implantation in 13 patients with atrial pacing was 0.99 V (range 0.5 to 1.7 V). These thresholds were measured 5 to to minutes after fixation. P-wave amplitudes were measured from intracavitary electrograms. The average amplitude measured from peak to peak in 20 patients was 2.8 m V (range 0.8 to 7 .0 m V) (Tables I and II) . All recorded P waves showed an injury pattern with ele vations of the P-Ta segment. There were no instances of electrode dislodgment or any other complications, such as penetration or thrombosis, in the 20 patients. The relative or absolute stimulation thresholds have been acceptable in all the patients during the short follow-up period (average period 5 months, range I to II months) . REFERENCES Kleinert M, Bock M, Wilhelmi L: Clinical use of a new transvenous atrial lead. Am J Cardiol 40:237-242, 1977 2 Moss AJ, Rivers RJ: Atrial pacing from the coronary vein.
Volume 80 Number 5
Helifix endocardial fixation lead
799
November. 1980
Ten year experience in 50 patients with implanted pervenous pacemakers. Circulation 57: 103-106, 1978 3 Smyth NPD, Citron P, Keshishian 1M, Garcia 1M, Kelly LC: Permanent pervenous atrial sensing and pacing with a new f-shaped lead. 1 THoRAc CARDIOVASC SURG 72:565-
570, 1976 4 EI Gamal M, van Gelder B: Preliminary experience with
the Helifix electrode for transvenous atrial implantation. PACE 2:444-454, 1979 5 Babotai I, Meier WE, Scholzel E: Tierexperimentelle Erfahrungen mit einer neuen intrakardialen PacemakerElektrode. Langenbecks Arch Chir (Suppl Chir Forum)
144-147, 1976