Patient and Pacemaker Survival after Pacemaker Implantation

CLINICAL INVESTIGATIONS

Patient and PacemakerSurvivalafter PacemakerImplantation* Paul D. Levin, M.D.,#{176}#{176} Robert W. Sessions,j Mitchell Passovoy,tf and Richard A. Carleton, M.D., F.C.C.P.

One hundred thirty patients have had 244 pacemakers of five types implanted at Presbyterian-St. Luke’s Hospital in the past eight years. There has been I 0.50 probabilIty of successful unit function at only 12 months with epicardial units. All transvenous units used have had a 0.50 probabilIty of unit success at more than 17 months. This fact, combined with the lower frequency of early death with fransvenous units, has led to our opinion that epicardial units no longer have a place unless a thoracotomy is mandatory for other reasons.The data of the present study suggestan augmented early mortality with fixed rate transvenous units compared with a unit which synchronizes with the intrinsic ventricular rhythm. This, with the comparable unit reliability, will lead us to use ventricular synchronous *rans,enous units increasingly in the future.

C ardiac pacing has progressed rapidly from the early experimental observations of Hyman,’ the

DESCRIPTION OF PATIENTS AND PACEMAKEBS

The patients ranged in age between 5 and 89 years. Three

first clinical application by Weirich and associates,2 and the first pacemaker implantation perfonned by Chardack and co-workers.3 The world experience has been carefully reviewed and presented by Siddons and Sowton.4 The present report is a r#{233}sum#{233} of eight years of experience with implanted cardiac pacemakers in 130 patients involving 244 pacemaker units of five types. This review was undertaken to analyze both patient survival and comparative pacemaker unit longevity.

were under

40 years of age and 97 were between the ages of 60 and 79 years. Three patients had pacemakers implanted to prevent asystolic episodes due to transient atrial arrest. All other patients had brndycardia secondary to intermittent or sustained high grade A-V block. Twelve patients had A-V block in conjunction with idiopathic royoeardiopathy. Nine patients had had a documented rnyocardial infarction. Four patients developed A-V block as a consequence of ventricular septal defect closure or aortic valve replacement. The remaining patients had no identifiable cause for their A-V block and were presumed to have degeneration of the cardiac fibrous supporting structures as described by Lev.5 Each patient with A-V block had experienced StokesAdams episodes, congestive failure, or both, prior to pacemaker implantation. Fives types of implantable pacemakers have been used. Two are indigenous to the institution and have been described previously.’#{176} The epicardial (A) and endocardial (B) models of the Presbyterian-St. Luke’s Hospital pacemakers differ only in the configuration of the myocardial electrodes. The third type is the model 5870 pacemaker manufactured by the Medtronic Corporation, Minneapolis, Minnesota (C) Two types of pacemakers, both of which synchronize with endogenous electrical impulses, have been used. These are the Ectocor (D) and the Atricor (E), both made by the Cordis Corporation, Miami, Florida. Type A pacemakers were used esclusively between May, 1961, and September, 1965. Since that time, type B units have been used increasingly and are now used almost exclu-

From the Section of Cardio-Respiratory Diseases. Depart. ment of Medicine, Presbyterian-St. Luke’s Hospital and the Department of Medicine, University of Illinois College of 1’,ledicine, Chicago,Illinois. Supported in part by NIH Training grant No. HE 05714 from the United States Public Health Service. USPHS Trainee in Cardiology, Section of Cardio-Respiratory Diseases, Department of Medicine, Presbyterian-St. Luke’s Hospital and Research Assistant in Medicine, University of Illinois College of Medicine. tDirector, Electronics Laboratory, Department of Medicine, Presbyterian-St. Luke’s Hospital. ttDirector, Section of Biostatistics and Experimental Design, Department of Medicine,Presbyterian-St. Luke’s Hospital. §Direetor, Section of Cardio-Respiratory Diseases, Department of Medicine, Presbyterian-St. Luke’s Hospital and Professor of Medicine, University of Illinois College of Medicine.

4

PATIENT AND PACEMAKERSURVIVAL

5

sively. Type C units have been used without selection of patients when the supply of available type A or B pacemakers has beer. temporarily exhausted. Types D and E pacemakers have been used in individuals known or suspected to have intermittent A-V block. l’vpes A, C and E have been implanted through a left thoracotoiny. Types B and V have been implanted through a single suhclavicular incision, usually on the right, using a cephalic vein to introduce the transvenous electrode. In either instance, a pocket is constructed in subcutaneous tissue for implantation of the pulse generator superficial to the pectoralis muscles. Earlier experience with skin erosion over three units has led to implantation deep to the pectoralis major muscle in slender patients. Antibiotics have not been used routinely, hut have been administered to the four patients ‘hr. developed infected implant SiteS. Skin sutures of various siithetic materials have been left in for 10 to 12 days; neither important suture infections nor wound dehiscence has occurred. Separate analyst’s have lx,en conducted of pacemaker unit survival and of patient sitnival. For the former, replacement of a unit for any reason terminated the follow-up of that unit and started the follow-tip of another unit at time zero. For the latter, only patient survival is considered in the life-table analysis, regardless of how many pacemaker units have been used to permit patient survival. Units or patients which have been follosvetl for a period of time, eg, nine months, hint not as long as the nest tabulated time, eg, 12 months, are listed in the tal,les as insufficient exposure and represent a decrement in the units subsequently at risk. In the calculation of probability of surviving to a given time, entries under insuffident exposure headings are assumed to have survived an average of one half the next time interval. All patients who tiled temiinated a pacemaker nmnitexposure. All deaths are assumed to reflect pacemaker failure. All patients were observed through May, 1969. RESULTS

The probability

Pacemaker Unit Functional Status Table 1 presents the numerical results of experience with pacemaker types A through E. Type A: The use of epicardial units of type A has been associated with seven deaths within three months after surgery.

Four were directly

attrihut-

able to complications of the thoracotomy. Three occurred within the subsequent six weeks. One is known and two are presumed to reflect competition between the pacemaker stimuli and the intrinsic cardiac

rhythm.

Electronic

component

failure

oc-

curred preferentially earl in our experience with pacemakers and reflected the use of an epoxy potting compound which imbibed small but harmful amounts of water. The correction of this problem is reflected in the lack of component failure in units of type B, all of which have been manufactured since August, 1965. Pacemaker unit failure because of faulty mvocardial contact has occurred for several reasons. One wire became dislodged from the epicardium because an inadequate loop of wire permitted

direct

traction

patients developed myocardial stimulation thresholds in excess of four volts for a 2-msec impulse. Several of these patients at autopsy had dense fibrous tissue surrounding the epicardial electrodes. Premature battery failure, defined as failure before 15 months, terminated the life of nine units. These also reflect the early use of an imperfect epoxy. Two causes of pacemaker failure are included under “other.” Three units eroded through the skin overlying the subcutaneous pocket. Three patients developed infections of the subcutaneous pocket, necessitating implantation of a new unit at a different site. The cumulative probability of unit function of only 0.52 at 15 months predominantly reflects early deaths and faulty myocardial Contact. Type B: The use of the endocardial route for permanent pacing has been associated with a predictably lower death rate. The two early deaths represent patients in whom a pacemaker did not reverse preexisting severe heart failure. Two of the six deaths between three and six months occurred in patients known to have pacemaker-intrinsic rhythm competition. A single patient with severe myocardiopathy had a myocardial threshold of four volts at the initial implantation and paced only intermittently seven months after implantation. Exploration of the right ventricle with a new endocardial electrode demonstrated a threshold greater than five volts at all sites. This patient is presumed to have diffuse endocardial fibrosis.7 No component or premature battery failures occurred.

on the electrode.

CHEST, VOL. 58, NO. 1, JULY 1970

Two

of unit function,

including

pa.

tients who died, reaches the 0.50 level at approximately 20 months after implantation. Type C: The patients in the small series of type C units experienced two instances of premature battery failure, two broken wires, and one instance of an infected pacemaker pocket. No deaths occurred. A 0.50 probability of unit function is reached at approximately

23 months,

a value not significantly

different from that for type B units. Type D: Our experience with type 0 units is more recent. Accordingly, the number of units at risk after 12 months is small. No deaths occurred. One catheter electrode became dislodged three months after implantation. One patient developed a high stimulation threshold ten months after iniplantation; pacing was successfully reestablished with a new pacemaker. One premature battery failure occurred. The small number of units at risk limits the precision of estimation, hut the 0.50 probability level of unit function occurs behveen the 18th and 21st months after implantation. Type E: Each unit of this type was implanted

6

LEVIN ET AL Table I-Pacernaker

Type A Units at risk Inaufficierit expostirt. I’uceniaker component failures Battery Myocardini contact Components Death Other Probability of unit function TYPE B Units at risk Insufficient exposure Pacemaker component failures Battery Myocardial contact Components Death Other Probability of unit function TYPE C I’aits at risk Insufficient exposure Pacemaker component failures Bat terv Myocarthal contact Components Death Other Probability of unit function

0

3

113 2

104

7

IS

7

0 1.00

IS 2 0 0 0 2 0

6

Months after Pacemaker Implantation 12 15 18 2! 24 27

9

14 2 9 I I 1 6 13 9 9 2 3 1 5 0 0 2 I 2 0 0 1 0 4 2 1 2 1 0 0 2 3 1 0 0 0 0 0.94 0.78 0.69 0.62 0.52 0,31 0.16

o

0 0 0

84

Unit Function after Implantation.

64

7 8 0 0 0 6 2 0.97

1,00

86

75

62

2

5

5

#{182}18

9

42 5 1 0 0 1 0 0 0 0 0 I 0 0.81 0.83

49

6

1

36 5 3 0 0 0 3

28 2 4 4 0 0 0 0 0 0.8! 0.73

0 0 0 0 0 0.05

0 0 0 0 0 0 I .1 0 0 0.05 0.03

3 0 2 2 0 0 0 0 0.70

1 0 1 0 0 0 0 0 0 0.23

4 0 0 0 0 0 0 0 0.75 0.75

1 0 0 0 0 0 0 0 0.75

4 0 I I 0 0 0 0 0.75

3 0 2 2 0 0 0 0 0.56

1

0 0.86

1.001.00

39

I 0 0 0 0 0.02

14 16 0 I I 7 5 7 5 0 0 0 0 0 0 0 0 0.47 0.23

4 I 0 0 0 0 0 0 0.70

0 0 0

0

2 0 I

8 4 0 0 0 0 0 0 0.70

I

0 0 0

I 0 I

3

16 14 II 1 2 1 I I 2 0 1 0 1 0 I 0 0 0 0 0 0 0 0 I 1.00 0.94 0.86

0 0 0 0 0

0 0

36

0 I

0.71

0

33

0

0.86

12

0 2

o

10 0 1 1 0 0 0 0

22 3 5 4 0 0 1 0 0.62

3 0

0.86

14

0

12 0 2 1 1 0 0 0

28 0 14 13

9 0 1 0 1 0 0 0 0.64

14

12 0 0 0 0 0 0 0

48 I 19

30

8 2 I I 0 0 0 0 0.57

5 0 0 0 0 0 0 0 0.4)

5 0 2 2 0 0 0 0 0,49

3 0 2 2 0 0 0 0 0.29

1 0 0 0 0 0 0 0 0.10

I 0 0 I 1 0 0 0 0 0,10

TYPE D Units at risk Insufficient exposure Pacemaker component failures Battery Mvoeardial contact Components Death Other Probaliilitv of unit function

25 9 0 0 0 0 0 0 1.00

TYPE E Units at risk Insufficient exposure Pacemaker component failures Buttery \Ivocardial contact (‘omwnents Death Other Prolmahilit v of unit function

8 0 1 0 0

7 0 1 0 0

o

I 0 0.88

o

1.00

o

6 I 0 0 0 0 0 0 0.75

during thoracotomy. One operative death occurred. A second early death occurred in a patient with an aortic valvular prosthesis. Neither premature battery failure, myocardial threshold problems nor component failure occurred in the small number of units.

5 1 0 0 0 0 0 0

1 0 0 1 1 0 0 0 0 0.19

The 0.50 probability of unit function occurred at approximately 21 months. Patient Survival Table 2 presents the patient experience after the

CHEST, VOL. 58, NO. 1, JULY 1970

PATIENT AND PACEMAKERSURVIVAL Table Time Since First Implant (years

At Risk at Start of Period

0 I 2 3 4 6

2-Patient

Insuffieient li XI)OSU re

130

27

84

29

49 26 13 5 I

5

7

Dea t us 19 6

4 0 3 1 0

19 13 5 3 1

time of each initial pacemaker implantation. These data do not reflect the disability caused by diverse complications discussed previously, but show only survival or death. As shown, there is greater than a 0.71 probability of surviving for any single year starting from an%’ anniversary date after initial implantation. The likelihood of surviving four years after the initial implant is 0.50. Co1MT

The crucial question concerning pacemaker implantation is whether life is being prolonged. A related question, which the present study can only answer semiquantitatively, is whether the quality of life is improved. Probably the best information available concerning survival of patients with A-V block without pacing is that presented by Friedberg and colleagues. In this series, the probability of surviving one year was 0.50 after a diagnosis of AV block. In this context, the four-year 50 percent survival of the present series represents a clear improvement

attributable

to the use of pacemakers,

and is comparable to the clinical success reported by others. The quality of life permitted by pacemakers has generally

been improved

among

the survivors,

as

has been lucidly described by Greene and Moss.9 This improvement has been only briefly interrupted for those few patients who have developed infection and for the brief periods required for unit replacement. The improvement in both patient and unit survivat since our earlier summation of results 6 reflects both improved pacemaker manufacture and the transition from epicardial to endocardial units. Pacemakers which synchronize with atrial depolarization are hemodvnamically preferable,8IO but have the major drawback that thoracotomv is required. It is our present opinion that the function of these units is reliable, and that pacemakers of type E are preferable when a thoracotomy is mandatory for other reasons. The cause of the early deaths after implantation of type B units cannot be ascertained because they

CHEST, VOL. 58, NO. 1, JULY 1970

Surm’im’oI Esperienr.e. Probability of Surviving One Add it ionn I Year 0.8,5 0.91

0.90 1.00 0.7! 0.7!

I’rol,ahilitv of Surviving from Ii rst Iin i,ta ri 0.85 0,77 0.69 0.69

0,50 0.35

occurred at home without clear causes established. The strong suspicion continues to exist that pacemaker-intrinsic rhythm competition presents a hazard to life.1 1 The equivalent reliability of types B and D pacemakers makes it likely that we shall increasingly use type 0 units in all patients when suspicion exists that the A-V block may be pennanent. ACKNOWLEDGMENTS: We are indebted to Dr. NI. \Veinberg, Jr., Dr. 0. C. Julian, Dr. H. Javid, Dr. \V. S. Dye, Dr. J. A. Hunter amid Dr. H .N ajafi for their success with the stirgery and for their assistance in obtaining infonnation aixitit many of the patients in this study. Sir. James Davis, premedical student, made an invaluable contribution in the eniIection and analysis of these data. REFERENCES 1 Hyman AS: Resuscitation of the stopped heart by intracardial therapy. II. Experimental use of an artificial pacemaker, .Arch lotern Med 50:283, 1932 2 Weirich WL, Paneth SI, Cott VL and Lillehei C’: Control of complete heart block by use of an artificial pacemaker and a mvocardial electrode, Circ Res 6:41t), 1958 3 Chardack WM, Gage AA, Federico AJ, Schimert C and C;reatbuch \V: Five years’ clinical experience with an implantable pacemaker: an appraisal, Surgery 58:915,

1965 4 Siddons I-I and Sowton E: Cardiac Pacemakers, Springfield, Illinois, Charles C Thomas, 1967 S Lev I: The normal anatomy of the conduction system in man and its pathology

in atrioventrienlar

block, Ann NY

Acad Sci 111:817, 1964 6 Carleton BA, Sessions RW, \Veinberg NI and Hunter JA: Four years’ experience with implanted cardiac pacemakers, Presbyterian-St Luke’s Hosp Sled Bufl 6:2, 1967 7 Clark JG, Bucheleres HG and Carleton BA: Emidoeardial fibrosis: detection by cardiac pacing, Circulation 38:1136, 1968 8 Friedherg CK, Donoso E and Stein \VG: Nonsmirgieal acquired heart block, Ann Ni Ac’ad Sd 111835, 1964 9 Greene VA and SIoss AJ: Psychosocial factors in the adjustment of patients with pennanentlv implanted cardiac pacemakers. Ann Intern Sled 70:897, 1969 10 Carleton BA and Graettinger JS: The hemodynamnic role of the atria with and vithotrt mitral stenosis, Amer J Sled 42:532, 1967 11 Sowton E: Artificial pacemaking and sinus rhythm, Brit HeartJ27:311, 1965 Reprint requests: Dr. Carleton, 1753 Vest Congress Parkway, Chicago, Illinois 60612.