- Email: [email protected]
A multiprogrammable pacemaker with unipolar or bipolar option
412
Brief
Communications
Table
II. Postoperative catheterization data
American
A multiprogrammable pacemaker with unipolar or bipolar option
Adoon (0,)
Pressure (mm Hg)
56 32 86 84 63
7 7 7514 70145, w 70/50, E
87 46 46
z 7514 75145, m
Sat.
Site
svc RA RV Ao Ao (desc) PV LA LV PA RPA
Qp = 2.57 ml/min/m’; PVR = 21.80 units/m2; Table
occlusion PDA (mm
of Hg)
Qs = 3.86
In (mm
02 Hgj
Nicholas P. D. Smyth, M.D., M.S., and Diane Sager, R.N., MS. Washington,
75150 ml/min/m2;
SVR = 15.30
units/m?.
Qep = 3.46
Abbreviations
August. 1983 Heart Journal
75145,
5-5
ml/min/m”;
as in
1.
PDA during cardiac catheterization, and (3) no change in pulmonary vascular resistance following 0, administration. The grade IV (irreversible) pulmonary vascular changes noted in the lung biopsy corroborated the hemodynamic data. Provided the aorticopulmonary communication could be demonstrated to be adequate, it was felt that there were certain advantages to using the ductus as the modus to decompress the pulmonary vascular bed in association with atria1 rerouting. First, the need for ventriculotomy was eliminated; second, decompression distal to the brachiocephalic vessels would seem to reduce the risk of cerebrovascular accident due to paradoxical embolization. In the absence of a PDA, a prosthetic or biologic conduit between the pulmonary artery and the descending aorta would be an attractive alternative to the creation of a VSD. Our patient had irreversible changes in the pulmonary vascular bed. Following the Senning procedure, he has a right-to-left shunt but the desaturation of arterial blood begins at the level of the descending aorta while preoperatively the descending aorta was more saturated than the ascending aorta. The present situation is preferable in a growing child with better cerebral oxygen saturation, although the long-term prognosis remains unclear. REFERENCES
1. Rudolph AM: Cardiac catheterization and angiocardiographv. Chicago, 1974, Year Book Medical Publishers, Inc. b i55. .. 2. Mair DD, Ritter DD, Danielson GK, Wallace RB, McCoon DC: The palliative Mustard operation: Rationale and results. Am J Cardiol 37:762, 1976. _ 3. Newfeld EA, Paul MH, Muster JH, Idriss F: Pulmonary vascular disease in complete transposition of the great arteries. A study of 200 patients. Am J Cardiol 34:75, 1974. 4. Lindesmith GG, Stiles QR, Tucker BL, Gallaher ME, Stanton RE, Meyer BW: The Mustard operation as a palliative procedure. J Thorac Cardiovasc Surg 63:75, 1972. 5. Stark J, deLeva1 MR, Taylor JFN: Mustard operation and creation of ventricular septal defect in two patients with transposition of the great arteries, intact ventricular septum and pulmonary vascular disease. Am J Cardiol 36:524, 1976.
D.C.
A multiprogrammable VVIM pulse generator was recently introduced (Multicor 336A, Cordis Corporation, Miami, Fla.) with the unusual feature of a programmable choice of unipolar or bipolar modes. In general, we prefer the unipolar mode because of the smaller leads required, the supposedly better sensing, and the larger pacer spike which makes ECG and especially transtelephonic followup much easier. However, recent reduction in bipolar lead size, the demonstration that there may be little difference or even improved sensing in the bipolar mode,’ and the greater immunity to electromagnetic interference (EMI)-especially the type caused by muscle potentialshave made the bipolar mode as attractive if not more attractive than the unipolar mode.2 We implanted 14 of these pacemakers, planning to study their function in both modes. The Multicor Gamma 336A is a VVIM unit with four output levels, eight sensitivities, fourteen rates, and three modes. It also has programmable polarity. Specific values are-Weight: 43 grams; Height: 57 mm; Diameter: 48 mm; Thickness: 10 mm; Output: High = 7 Ma, Medium = 4 Ma, Low = 2 Ma; Rate range: 25 to 120 ppm; Sensitivity range: 0.8 to 5.5 mV; Modes: VVI, VVT, and VOO; Polarity: Unipolar and bipolar; Circuitry used: CMOS and VMOS technology. The pulse generator can accept a standard unipolar lead (not recommended for reasons discussed later) or a bipolar lead of the same size with a linear (coaxial) connector. In this connector the pin is the cathodal connector and a metal sleeve is the anodal connector (Fig. 1). An adaptor is available for conversion of the old style bifurcated bipolar lead connector to the linear (coaxial) type. The programming technique and circuitry for this pacemaker are fully described in technical manuals.“, 1 We implanted 14 of these units as initial implants (Table I). The Cordis bipolar lead with linear (coaxial) connector (No. 325161) was used in all cases (Fig. 1). Both unipolar and bipolar intracavitary electrograms (with the tip electrode as cathode in all cases) were obtained in all patients using either an optical recorder (Electronics for Medicine, White Plains, N.Y.) or a direct writer (EKG Monitor and Recorder No. 2300; American Optical Co., From the Departments of Surgery, The Washington Hospital Center, and the George Washington University School of Medicine. Supported by the Research Foundation of the Washington Hospital Center and by the Potomac Fund for Cardiovascular Research, Washington. D.C. Received for publicalion May 17, 1982; revision received July 6. 1982; accepted .July 9, 1982. Reprint requests: Nicholas P. D. Smyth, M.D., Suite No. 220, 106 Irving St.. N.W.. Washington. DC 20010.
Volume 106 Number 2
Brief
Communications
4 13
14 patients n = current 0 = voltage
,
.15
1. Photograph of the bipolar lead used with the Multicor pulse generator. The stabilizing fins and linear (coaxial) connector are shown.
1
’
.30
SO Pulse
Fig.
Table
.7s duration
1.0
1.25
1.5
fms)
2. Unipolar pacing thresholds (average values).
Fig.
I. Clinical and pacemaker characteristics Muscle inhibition
Patient
Age
M.H. C.D.
85 80
K.D. J.M. S.H. W.M.
77 72 71 68
M.B.
77
J.W. A.L. IS. H.W. CM. W.S. M.F.
87 69
*Intrinsic
Sick sinus syndrome Atria1 fibrillation with slow ventricular response Complete heart block Sinus bradycardia Complete heart block Intermittent complete heart block Intermittent complete heart block Complete heart block Sick sinus syndrome Sinus bradycardia Complete heart block Sinus bradycardia Complete heart block Sick sinus syndrome
66 66 66 64 65 rhythm
faster
Polarity
Diagnosis
than
was programmed
to take advantage
of
the larger R wave or lower thresholds. A complete test of all pulse generator parameters was carried out 1 week postoperatively and 1 month postoperatively. Available sensitivities, rates, and pulse widths were checked and recorded. The magnet rate was recorded and an isometric test for muscle inhibition was done. Based on this test, at 1 month postoperatively the patient was programmed to bipolar mode if the muscle inhibition test was positive in the unipolar mode. The same tests were then carried out every 3 months.
mode
Current
status
Bipolar Bipolar
Not tested* Negative
Normal pacing Normal pacing
Bipolar Bipolar Bipolar Bipolar
Negative Positive Negative Negative
Normal Normal Normal Normal
Bipolar
Not tested*
Patient died
Bipolar Bipolar Unipolar Bipolar Bipolar Unipolar Bipolar
Negative Negative Negative Positive Negative Negative Negative
Normal Normal Normal Normal Normal Normal Normal
pacing pacing pacing pacing
pacing pacing pacing pacing pacing pacing pacing
pacer.
Buffalo, N.Y.), and a digital measurement of the R wave amplitude using the Cordis PSA No. 209A was obtained in every case. Pacing thresholds were measured at pulse widths of 0.15, 0.3, 0.5, 0.75, 1.0, 1.25, and 1.5 msec, using the same Cordis PSA (Figs. 2 and 3). Programmable settings were adjusted as needed at the time of implantation, and polarity
in unipolar
Follow-up has been from 1 to 2 years for 13 patients. One patient died early in the postoperative period, apparently
from
pulmonary
embolism.
In 14 patients
the R
wave amplitude in the unipolar mode ranged from 3.0 to 17.0 mV, with an average of 6.6 mV. In the bipolar mode the comparable figures were 3.0 to 25.0 mV and an average of 6.73 mV. The pacing threshold values were remarkably similar in unipolar and bipolar modes (Figs. 2 and 3). In all patients polarity was chosen on the basis of the muscle inhibition test, the R wave size, and/or the threshold values (Tables I and II). Bipolar sensing was generally slightly better than unipolar sensing, although the difference cannot be considered significant in such a small series. Pacing thresholds were not significantly different. The programmable polarity feature, however, allowed the better choice in each patient. The bipolar mode was definitely of value in two
414
Brief
Communications
14 1.5
American
.- currmt 0 = voltbob
2 ; z g 1
1.0
_
E : 0.5 3
_
Primary intramural cardiac tumor: Long-term follow-up
pathlts
_
Yzhar Charuzi, M.D., Harold Mills, Neil A. Buchbinder, M.D., and Lorraine A. Marshall, R.N. Los Angeles, Calif.
z
01
.¶5
.30
.50
.75
Pulse duration
Fig.
Table
3.
Bipolar
II. Polarity
pacing
1.0
1.25
1.5
(ms)
thresholds
(average
values).
choice
Patient
Polarity
M.H. C.D. K.D. J.M. S.H. W.M. M.B. J.W. A.L. IS. H.W.
Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar linipolar Bipolar
C.M. W.S. M.F.
Bipolar Unipolar Bipolar
August, 1983 Heart Journal
Reason for polarity choice
Larger R wave Larger R wave Lower thresholds Muscle inhibition Larger R wave Larger R wave Larger R wave Lower thresholds Larger R wave Larger R wave Lower thresholds; muscle inhibition Lower thresholds Lower thresholds Larger R wave
patients who exhibited muscle inhibition in the unipolar mode. This pulse generator will accept a unipolar lead but must be used with a bipolar lead. Otherwise programming to the bipolar mode with a unipolar lead will cause loss of pacing which could be serious in a pacer-dependent patient. Programmable polarity is a useful feature in a multiprogrammable pacemaker and it should be considered as a possible standard in future multiprogrammable units. Some sort of safeguard should be developed to avoid the consequences of mistakenly connecting such a pulse generator to a unipolar lead and programming it to the bipolar mode with resulting loss of pacing.
M.D.,
Primary cardiac tumors occur infrequently, are generally benign, yet may cause disability or even death.‘,2 Intracavitary myxomas are the most frequent primary cardiac tumors, and their clinical manifestation results from interference with intracardiac blood flow or from embolic phenomena.” Primary intramural cardiac tumors occur less frequently, vary in location and size, and lack a characteristic clinical pattern.‘, ‘. 4-fi Establishment of the diagnosis of intramural cardiac tumors is important because of the potential for surgical resection.7-‘Z However, while resection of a myxoma provides a cure, resection of an intramural cardiac tumor is palliative. Therefore, surgical intervention is recommended only when specifically indicated by the clinical manifestations, the type of tumor, its localization, and its size. Echocardiography has become a very effective noninvasive tool for the diagnosis of myxomas, while its role in the diagnosis of intramural cardiac tumors has not been fully established.“‘-“’ There is a paucity of knowledge about the natural history of intracavitary and intramural cardiac tumors. In this report we present a unique case in which an intramural cardiac tumor was diagnosed by two-dimensional echocardiography and also was evaluated retrospectively and prospectively over a period of 15 years. A &year-old Caucasian female was referred to one of us (HM) in April, 1978, complaining of easy fatigability. At age 11 she began experiencing episodes of palpitation, and the diagnosis of congenital heart disease was SUSpetted. At age 18, because of a sustained bout of ventricular tachycardia, quinidine therapy was initiated for conversion to and maintenance of sinus rhythm. At age 35, following weakness and palpitation, cardiac catheterization was performed in another institution. The contrast left ventriculogram and coronary arteriogram were reported to be normal. The patient had continued on quinidine therapy and had not experienced any further significant episodes of palpitation or other cardiac symptoms. The patient appeared to be in good general health. The heart rate was 80 bpm and regular and the blood pressure was 120/80 mm Hp. Cardiac examination revealed a left precordial heave. The first heart sound was normal, and the second heart sound was physiologically split with AS
REFERENCES
DeCaprio V, Hurzeler P, Furman S: Comparison of unipolar and bipolar electrograms for cardiac pacemaker sensing. Circulation 56~750, 1977. 2. Hauser RG: Bipolar leads for cardiac pacing in the 1980’s: A reappraisal provoked by skeletal muscle interference. PACE 534, 1982. 3. Cordis technical bulletin No. 149-3650-1A. 4. Cordis technical bulletin No. 149-3919-1. 1.
From the Ilivision (>I’cardiology, Department of Medicine, Cedars-Sinai Medicaf Center and the LJCLA School of Medicine. Supported in part hy Save A Heart Foundation. Received for publication March 11, 1982; accepted Apr. 28, 1982. Reprint requests: Publications Office, Halper 321, Diviwn of Cardiology. Cedars-Sinai Medical Center, 8700 Beverly Blvd., Los Angeles. CA 90048.
Brief
Communications
Table
II. Postoperative catheterization data
American
A multiprogrammable pacemaker with unipolar or bipolar option
Adoon (0,)
Pressure (mm Hg)
56 32 86 84 63
7 7 7514 70145, w 70/50, E
87 46 46
z 7514 75145, m
Sat.
Site
svc RA RV Ao Ao (desc) PV LA LV PA RPA
Qp = 2.57 ml/min/m’; PVR = 21.80 units/m2; Table
occlusion PDA (mm
of Hg)
Qs = 3.86
In (mm
02 Hgj
Nicholas P. D. Smyth, M.D., M.S., and Diane Sager, R.N., MS. Washington,
75150 ml/min/m2;
SVR = 15.30
units/m?.
Qep = 3.46
Abbreviations
August. 1983 Heart Journal
75145,
5-5
ml/min/m”;
as in
1.
PDA during cardiac catheterization, and (3) no change in pulmonary vascular resistance following 0, administration. The grade IV (irreversible) pulmonary vascular changes noted in the lung biopsy corroborated the hemodynamic data. Provided the aorticopulmonary communication could be demonstrated to be adequate, it was felt that there were certain advantages to using the ductus as the modus to decompress the pulmonary vascular bed in association with atria1 rerouting. First, the need for ventriculotomy was eliminated; second, decompression distal to the brachiocephalic vessels would seem to reduce the risk of cerebrovascular accident due to paradoxical embolization. In the absence of a PDA, a prosthetic or biologic conduit between the pulmonary artery and the descending aorta would be an attractive alternative to the creation of a VSD. Our patient had irreversible changes in the pulmonary vascular bed. Following the Senning procedure, he has a right-to-left shunt but the desaturation of arterial blood begins at the level of the descending aorta while preoperatively the descending aorta was more saturated than the ascending aorta. The present situation is preferable in a growing child with better cerebral oxygen saturation, although the long-term prognosis remains unclear. REFERENCES
1. Rudolph AM: Cardiac catheterization and angiocardiographv. Chicago, 1974, Year Book Medical Publishers, Inc. b i55. .. 2. Mair DD, Ritter DD, Danielson GK, Wallace RB, McCoon DC: The palliative Mustard operation: Rationale and results. Am J Cardiol 37:762, 1976. _ 3. Newfeld EA, Paul MH, Muster JH, Idriss F: Pulmonary vascular disease in complete transposition of the great arteries. A study of 200 patients. Am J Cardiol 34:75, 1974. 4. Lindesmith GG, Stiles QR, Tucker BL, Gallaher ME, Stanton RE, Meyer BW: The Mustard operation as a palliative procedure. J Thorac Cardiovasc Surg 63:75, 1972. 5. Stark J, deLeva1 MR, Taylor JFN: Mustard operation and creation of ventricular septal defect in two patients with transposition of the great arteries, intact ventricular septum and pulmonary vascular disease. Am J Cardiol 36:524, 1976.
D.C.
A multiprogrammable VVIM pulse generator was recently introduced (Multicor 336A, Cordis Corporation, Miami, Fla.) with the unusual feature of a programmable choice of unipolar or bipolar modes. In general, we prefer the unipolar mode because of the smaller leads required, the supposedly better sensing, and the larger pacer spike which makes ECG and especially transtelephonic followup much easier. However, recent reduction in bipolar lead size, the demonstration that there may be little difference or even improved sensing in the bipolar mode,’ and the greater immunity to electromagnetic interference (EMI)-especially the type caused by muscle potentialshave made the bipolar mode as attractive if not more attractive than the unipolar mode.2 We implanted 14 of these pacemakers, planning to study their function in both modes. The Multicor Gamma 336A is a VVIM unit with four output levels, eight sensitivities, fourteen rates, and three modes. It also has programmable polarity. Specific values are-Weight: 43 grams; Height: 57 mm; Diameter: 48 mm; Thickness: 10 mm; Output: High = 7 Ma, Medium = 4 Ma, Low = 2 Ma; Rate range: 25 to 120 ppm; Sensitivity range: 0.8 to 5.5 mV; Modes: VVI, VVT, and VOO; Polarity: Unipolar and bipolar; Circuitry used: CMOS and VMOS technology. The pulse generator can accept a standard unipolar lead (not recommended for reasons discussed later) or a bipolar lead of the same size with a linear (coaxial) connector. In this connector the pin is the cathodal connector and a metal sleeve is the anodal connector (Fig. 1). An adaptor is available for conversion of the old style bifurcated bipolar lead connector to the linear (coaxial) type. The programming technique and circuitry for this pacemaker are fully described in technical manuals.“, 1 We implanted 14 of these units as initial implants (Table I). The Cordis bipolar lead with linear (coaxial) connector (No. 325161) was used in all cases (Fig. 1). Both unipolar and bipolar intracavitary electrograms (with the tip electrode as cathode in all cases) were obtained in all patients using either an optical recorder (Electronics for Medicine, White Plains, N.Y.) or a direct writer (EKG Monitor and Recorder No. 2300; American Optical Co., From the Departments of Surgery, The Washington Hospital Center, and the George Washington University School of Medicine. Supported by the Research Foundation of the Washington Hospital Center and by the Potomac Fund for Cardiovascular Research, Washington. D.C. Received for publicalion May 17, 1982; revision received July 6. 1982; accepted .July 9, 1982. Reprint requests: Nicholas P. D. Smyth, M.D., Suite No. 220, 106 Irving St.. N.W.. Washington. DC 20010.
Volume 106 Number 2
Brief
Communications
4 13
14 patients n = current 0 = voltage
,
.15
1. Photograph of the bipolar lead used with the Multicor pulse generator. The stabilizing fins and linear (coaxial) connector are shown.
1
’
.30
SO Pulse
Fig.
Table
.7s duration
1.0
1.25
1.5
fms)
2. Unipolar pacing thresholds (average values).
Fig.
I. Clinical and pacemaker characteristics Muscle inhibition
Patient
Age
M.H. C.D.
85 80
K.D. J.M. S.H. W.M.
77 72 71 68
M.B.
77
J.W. A.L. IS. H.W. CM. W.S. M.F.
87 69
*Intrinsic
Sick sinus syndrome Atria1 fibrillation with slow ventricular response Complete heart block Sinus bradycardia Complete heart block Intermittent complete heart block Intermittent complete heart block Complete heart block Sick sinus syndrome Sinus bradycardia Complete heart block Sinus bradycardia Complete heart block Sick sinus syndrome
66 66 66 64 65 rhythm
faster
Polarity
Diagnosis
than
was programmed
to take advantage
of
the larger R wave or lower thresholds. A complete test of all pulse generator parameters was carried out 1 week postoperatively and 1 month postoperatively. Available sensitivities, rates, and pulse widths were checked and recorded. The magnet rate was recorded and an isometric test for muscle inhibition was done. Based on this test, at 1 month postoperatively the patient was programmed to bipolar mode if the muscle inhibition test was positive in the unipolar mode. The same tests were then carried out every 3 months.
mode
Current
status
Bipolar Bipolar
Not tested* Negative
Normal pacing Normal pacing
Bipolar Bipolar Bipolar Bipolar
Negative Positive Negative Negative
Normal Normal Normal Normal
Bipolar
Not tested*
Patient died
Bipolar Bipolar Unipolar Bipolar Bipolar Unipolar Bipolar
Negative Negative Negative Positive Negative Negative Negative
Normal Normal Normal Normal Normal Normal Normal
pacing pacing pacing pacing
pacing pacing pacing pacing pacing pacing pacing
pacer.
Buffalo, N.Y.), and a digital measurement of the R wave amplitude using the Cordis PSA No. 209A was obtained in every case. Pacing thresholds were measured at pulse widths of 0.15, 0.3, 0.5, 0.75, 1.0, 1.25, and 1.5 msec, using the same Cordis PSA (Figs. 2 and 3). Programmable settings were adjusted as needed at the time of implantation, and polarity
in unipolar
Follow-up has been from 1 to 2 years for 13 patients. One patient died early in the postoperative period, apparently
from
pulmonary
embolism.
In 14 patients
the R
wave amplitude in the unipolar mode ranged from 3.0 to 17.0 mV, with an average of 6.6 mV. In the bipolar mode the comparable figures were 3.0 to 25.0 mV and an average of 6.73 mV. The pacing threshold values were remarkably similar in unipolar and bipolar modes (Figs. 2 and 3). In all patients polarity was chosen on the basis of the muscle inhibition test, the R wave size, and/or the threshold values (Tables I and II). Bipolar sensing was generally slightly better than unipolar sensing, although the difference cannot be considered significant in such a small series. Pacing thresholds were not significantly different. The programmable polarity feature, however, allowed the better choice in each patient. The bipolar mode was definitely of value in two
414
Brief
Communications
14 1.5
American
.- currmt 0 = voltbob
2 ; z g 1
1.0
_
E : 0.5 3
_
Primary intramural cardiac tumor: Long-term follow-up
pathlts
_
Yzhar Charuzi, M.D., Harold Mills, Neil A. Buchbinder, M.D., and Lorraine A. Marshall, R.N. Los Angeles, Calif.
z
01
.¶5
.30
.50
.75
Pulse duration
Fig.
Table
3.
Bipolar
II. Polarity
pacing
1.0
1.25
1.5
(ms)
thresholds
(average
values).
choice
Patient
Polarity
M.H. C.D. K.D. J.M. S.H. W.M. M.B. J.W. A.L. IS. H.W.
Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar Bipolar linipolar Bipolar
C.M. W.S. M.F.
Bipolar Unipolar Bipolar
August, 1983 Heart Journal
Reason for polarity choice
Larger R wave Larger R wave Lower thresholds Muscle inhibition Larger R wave Larger R wave Larger R wave Lower thresholds Larger R wave Larger R wave Lower thresholds; muscle inhibition Lower thresholds Lower thresholds Larger R wave
patients who exhibited muscle inhibition in the unipolar mode. This pulse generator will accept a unipolar lead but must be used with a bipolar lead. Otherwise programming to the bipolar mode with a unipolar lead will cause loss of pacing which could be serious in a pacer-dependent patient. Programmable polarity is a useful feature in a multiprogrammable pacemaker and it should be considered as a possible standard in future multiprogrammable units. Some sort of safeguard should be developed to avoid the consequences of mistakenly connecting such a pulse generator to a unipolar lead and programming it to the bipolar mode with resulting loss of pacing.
M.D.,
Primary cardiac tumors occur infrequently, are generally benign, yet may cause disability or even death.‘,2 Intracavitary myxomas are the most frequent primary cardiac tumors, and their clinical manifestation results from interference with intracardiac blood flow or from embolic phenomena.” Primary intramural cardiac tumors occur less frequently, vary in location and size, and lack a characteristic clinical pattern.‘, ‘. 4-fi Establishment of the diagnosis of intramural cardiac tumors is important because of the potential for surgical resection.7-‘Z However, while resection of a myxoma provides a cure, resection of an intramural cardiac tumor is palliative. Therefore, surgical intervention is recommended only when specifically indicated by the clinical manifestations, the type of tumor, its localization, and its size. Echocardiography has become a very effective noninvasive tool for the diagnosis of myxomas, while its role in the diagnosis of intramural cardiac tumors has not been fully established.“‘-“’ There is a paucity of knowledge about the natural history of intracavitary and intramural cardiac tumors. In this report we present a unique case in which an intramural cardiac tumor was diagnosed by two-dimensional echocardiography and also was evaluated retrospectively and prospectively over a period of 15 years. A &year-old Caucasian female was referred to one of us (HM) in April, 1978, complaining of easy fatigability. At age 11 she began experiencing episodes of palpitation, and the diagnosis of congenital heart disease was SUSpetted. At age 18, because of a sustained bout of ventricular tachycardia, quinidine therapy was initiated for conversion to and maintenance of sinus rhythm. At age 35, following weakness and palpitation, cardiac catheterization was performed in another institution. The contrast left ventriculogram and coronary arteriogram were reported to be normal. The patient had continued on quinidine therapy and had not experienced any further significant episodes of palpitation or other cardiac symptoms. The patient appeared to be in good general health. The heart rate was 80 bpm and regular and the blood pressure was 120/80 mm Hp. Cardiac examination revealed a left precordial heave. The first heart sound was normal, and the second heart sound was physiologically split with AS
REFERENCES
DeCaprio V, Hurzeler P, Furman S: Comparison of unipolar and bipolar electrograms for cardiac pacemaker sensing. Circulation 56~750, 1977. 2. Hauser RG: Bipolar leads for cardiac pacing in the 1980’s: A reappraisal provoked by skeletal muscle interference. PACE 534, 1982. 3. Cordis technical bulletin No. 149-3650-1A. 4. Cordis technical bulletin No. 149-3919-1. 1.
From the Ilivision (>I’cardiology, Department of Medicine, Cedars-Sinai Medicaf Center and the LJCLA School of Medicine. Supported in part hy Save A Heart Foundation. Received for publication March 11, 1982; accepted Apr. 28, 1982. Reprint requests: Publications Office, Halper 321, Diviwn of Cardiology. Cedars-Sinai Medical Center, 8700 Beverly Blvd., Los Angeles. CA 90048.