Abstract
Objective: To evaluate the effect of patients’ sex on selection of pacemakers.
Design: Retrospective univariate and multivariate analysis of a large database.
Setting: German central pacemaker register.
Subjects: Records collected at the register for 1992 and 1993 (n=31 913), covering 64% of all implantations in Germany.
Main outcome measure: Probability of receiving a single chamber, dual chamber, or rate responsive pacemaker in relation to sex.
Results: Univariate analysis showed that women were more likely to receive single chamber pacemakers and less likely to receive dual chamber or rate responsive systems than men. After demographic and clinical variables were controlled for, women were still more likely to receive a single chamber system (atrial pacing: odds ratio 0.89, 95% confidence interval 0.74 to 1.07; ventricular pacing: 0.85, 0.80 to 0.92) and less likely to receive a dual chamber (1.20, 1.12 to 1.30) or a rate responsive system (1.26, 1.17 to 1.37) than men.
Conclusions: The data suggest sex differences in the selection of a pacemaker system which cannot be explained by the underlying cardiac disorder. Further research is needed to evaluate why guidelines for implanting pacemakers are not better adhered to.
Key messages
Use of pacemakers varies despite guidelines, and the reasons for this are unclear
In this study women were more likely to receive single chamber pacemakers and less likely to receive dual chamber and rate responsive pacemakers than men
Demographic and clinical variables cannot fully explain these differences
Prospective studies are needed to evaluate the effect of sex and other non-medical variables on the selection of pacemakers
Introduction
Pacemakers are the standard treatment for symptomatic bradyarrhythmia. Professional societies have issued guidelines for the implantation of cardiac pacemakers.1–3 Although these guidelines have all been similar, considerable differences have been reported in the frequency of implantation of pacemakers and in the system selected.4 Relatively little is known about the reasons for these differences.5 There is some evidence that patients’ sex might play a part in clinical decision making.6–8 We used a large database to analyse whether sex can explain differences in the selection of pacemaker systems.
Subjects and methods
Doctors who perform implants transfer information available from the European pacemaker patient identification card to the German central pacemaker register on a voluntary basis. Customs’ statistics and manufacturers’ sales figures suggest that the register comprises 64% of all implantations in Germany. Of the 880 German hospitals in which implants are done (number estimated by a survey), 634 (72%) sent their reports to the register.9 Our analysis is based on complete data for the years 1992 and 1993. We excluded cases that had classification errors (for example, non-existent categories) from the total of 15 914 patients in 1992 and 15 999 patients in 1993. Table 1 gives the characteristics of the patients.
Table 1.
Men
|
Women
|
|||||||
---|---|---|---|---|---|---|---|---|
No (%) | Mean age | Median age | No (%) | Mean age | Median age | P value† | ||
Age (years) | n=15 648 | n=15 110 | ||||||
Mean (SD) | 73.8 (12.1) | 77.6 (10.9) | <0.001 | |||||
Median (interquartile range) | 73.6 (65.8-80.8) | 77.4 (70.4-82.4) | ||||||
Type of pacemaker | n=15 884 | n=15 389 | ||||||
Single chamber atrial | 429 (2.7) | 67.5 | 68.3 | 492 (3.2) | 70.9 | 72.8 | <0.005 | |
Single chamber ventricular | 10 499 (66.1) | 73.2 | 76.4 | 11 065 (71.9) | 75.8 | 78.7 | <0.001 | |
Dual chamber | 4892 (30.8) | 67.7 | 70.1 | 3770 (24.5) | 69.8 | 72.4 | <0.001 | |
Rate responsive‡ | 4273 (26.9) | 68.1 | 70.5 | 3186 (20.7) | 70.0 | 72.8 | <0.001 | |
Symptoms | n=12 005 | n=11859 | ||||||
Syncope | 4154 (34.6) | 71.8 | 74.5 | 4554 (38.4) | 75.4 | 78.3 | <0.001 | |
Dizziness | 3229 (26.9) | 72.1 | 73.7 | 3368 (28.4) | 74.3 | 77.0 | <0.01 | |
Bradycardia | 2389 (19.9) | 71.8 | 73.3 | 2063 (17.4) | 73.9 | 77.3 | <0.001 | |
Heart failure | 708 (5.9) | 73.1 | 76.2 | 629 (5.3) | 75.8 | 78.7 | <0.05 | |
Electrocardiographic result | n=11 874 | n=11 788 | ||||||
Atrioventricular block | 4346 (36.6) | 71.5 | 74.0 | 3902 (33.1) | 74.1 | 78.0 | <0.001 | |
Sick sinus syndrome | 3930 (33.1) | 72.0 | 73.7 | 4644 (39.4) | 74.8 | 77.2 | <0.001 | |
Atrial fibrillation/flutter | 2209 (18.6) | 73.4 | 75.8 | 2181 (18.5) | 76.1 | 78.7 | 0.814 | |
Aetiology | n=1 397 | n=11 263 | ||||||
Ischaemic | 3932 (34.5) | 73.7 | 75.5 | 3627 (32.2) | 76.1 | 78.5 | <0.001 | |
Fibrosis | 878 (7.7) | 71.7 | 73.8 | 969 (8.6) | 74.9 | 77.5 | <0.01 | |
Carotid sinus syndrome | 524 (4.6) | 71.0 | 72.4 | 338 (3.0) | 75.9 | 78.3 | <0.001 |
Categories with small numbers and cases labelled unknown are not included in the table.
Age analysed by t test, all other variables by χ2 test.
Percentage of the above pacemaker systems with rate responsive function.
Statistical analysis
We examined the pooled data for 1992 and 1993 according to patient characteristics (age, sex, clinical symptoms, underlying disease, electrocardiographic findings), type of pacemaker (single chamber, dual chamber), and rate responsive systems. The χ2 test was used to analyse discrete variables and Student’s t test used for continuous variables.
For logistic regression we defined the type of pacemaker as the dependent variable and age, sex, clinical symptoms, underlying disease, and electrocardiographic findings as independent variables. Explanatory variables for the selection of a specific pacemaker were first determined in a univariate logistic regression. We then used a multivariate model adjusting for age, clinical symptoms, underlying disease, and electrocardiographic findings to determine the effect of sex on choice of pacemaker. Cases with more than one missing value were excluded from univariate regression, and only complete datasets were used in the multivariate regression. All data were processed with sas 6.08 software. Α P value <0.05 was considered significant. All tests were two tailed.
Results
Table 1 shows that single chamber systems were implanted in a higher proportion of women (atrial 492 (3.2%), ventricular 11 065 (71.9%)) than men (atrial 429 (2.7%), ventricular 10 499 (66.1%)). In contrast, men received more dual chamber (4892 (30.8%)) and rate responsive systems (4273 (26.9%)) than women (3770 (24.5%), 3186 (20.7%)). Sex differences were also found for various clinical variables.
In the univariate analysis, where 21 858 patients could be included (68.5% of the sample), age, sex, several clinical symptoms, underlying disease, and electrocardiographic findings were significantly associated with the pacemaker system selected for implantation (table 2). After the effects of age, clinical symptoms, underlying disease, and electrocardiographic findings had been adjusted for in a multivariate analysis (n=16 289 (51.0% of the data)), women were still more likely to receive a ventricular single chamber pacemaker and less likely to receive a dual chamber or rate responsive system than men (table 3).
Table 2.
Type of pacemaker (odds ratio (95% CI))
|
||||
---|---|---|---|---|
Single chamber atrial | Single chamber ventricular | Dual chamber | Rate responsive | |
Age | 0.84 (0.80 to 0.88) | 1.35 (1.33 to 1.39) | 0.75 (0.70 to 0.80) | 0.80 (0.78 to 0.82) |
Sex | 0.84 (0.71 to 0.98) | 0.76 (0.72 to 0.81) | 1.38 (1.30 to 1.47) | 1.38 (1.29 to 1.47) |
Symptoms: | ||||
Syncope | 1.04 (0.87 to 1.21) | 1.15 (1.08 to 1.23) | 0.85 (0.79 to 0.91) | 0.65 (0.60 to 0.69) |
Dizziness | 1.64 (1.39 to 1.90) | 0.78 (0.73 to 0.83) | 1.20 (1.13 to 1.29) | 1.19 (1.10 to 1.27) |
Bradycardia | 0.74 (0.58 to 0.91) | 1.11 (1.03 to 1.20) | 0.93 (0.85 to 1.01) | 1.09 (1.00 to 1.18) |
Heart failure | 0.15 (0.07 to 0.25) | 1.09 (0.95 to 1.23) | 1.03 (0.90 to 1.18) | 1.54 (1.35 to 1.75) |
Electrocardiographic results: | ||||
Atrioventricular block | 0.06 (0.04 to 0.09)† | 0.35 (0.32 to 0.38) | 3.85 (3.57 to 4.16) | 0.93 (0.87 to 1.01) |
Sick sinus syndrome | 13.29 (11.11 to 15.42) | 0.89 (0.84 to 0.94) | 0.80 (0.75 to 0.85) | 1.19 (1.12 to 1.27) |
Atrial fibrillation/flutter | 0.11 (0.07 to 0.17)† | 14.28 (12.48 to 16.08) | 0.06 (0.05 to 0.07)‡ | 1.01 (0.92 to 1.08) |
Aetiology: | ||||
Ischaemic | 0.71 (0.59 to 0.83) | 1.43 (1.33 to 1.52) | 0.71 (0.66 to 0.77) | 0.68 (0.63 to 0.74) |
Fibrosis | 0.03 (0.02 to 0.04) | 0.81 (0.73 to 0.90) | 1.28 (1.15 to 1.43) | 1.04 (0.93 to 1.16) |
Carotid sinus syndrome | 0.59 (0.35 to 0.88) | 2.63 (2.13 to 3.17) | 0.37 (0.30 to 0.45) | 0.34 (0.27 to 0.43) |
Categories used in logistic regression were age: older patients/younger patients (10 year intervals); sex: men/women; and symptoms, electrocardiography, and aetiology: yes/no.
n<25.
n=119—cases with rare indications, low degree of disorder (atrioventricular block), or intermittent disorder.
Table 3.
Type of pacemaker | No (%) receiving treatment
|
Multivariate adjusted odds ratio* (95% CI) | |
---|---|---|---|
Men | Women | ||
Single chamber atrial | 2226 (2.8) | 260 (3.2) | 0.89 (0.74 to 1.07) |
Single chamber ventricular | 5680 (69.6) | 6069 (74.6) | 0.85 (0.80 to 0.92) |
Dual chamber | 2252 (27.6) | 1802 (22.1) | 1.20 (1.12 to 1.30) |
Rate responsive† | 1852 (22.7) | 1482 (18.2) | 1.26 (1.17 to 1.37) |
Adjusted for age, electrocardiographic results, symptoms, and aetiology; the ratios are men/women.
Number of above pacemaker systems with rate responsive function.
Discussion
Analysis of data from over 15 000 patients suggests a sex bias in choice of a pacemaker system. Women were more likely to receive single chamber systems and less likely to receive dual chamber or rate responsive systems than men. Can these findings be explained by differences in the underlying cardiac disorders or demographic data? In our cohort a higher proportion of men presented with an atrioventricular block than women. It is generally accepted that dual chamber pacemakers achieve better haemodynamic results than single chamber systems in atrioventricular block.2,10 Women, on the other hand, had a higher frequency of sinus node dysfunction. In this disorder a single chamber system often seems to be sufficient, although several authors have found that dual chamber pacemakers produce better outcomes in terms of haemodynamics, subjective symptoms, the development of atrial fibrillation, and prognosis.11 Finally, cardiovascular diseases occur at a later age in women than in men.12 In our cohort women were on average 3.8 years older than men. Doctors generally implant single chamber pacemakers in elderly patients rather than dual chamber systems.13
Several studies of factors influencing cardiovascular interventions showed that sex was no longer a determinant once demographic and clinical variables had been adjusted for.14,15 In our study, however, even after we controlled for demographic and various clinical variables sex remained independently associated with the selection of a pacemaker system. Our results agree with two retrospective studies in the United States in which women were found to receive a dual chamber system less frequently than men.16,17 The clinical importance of the suggested undertreatment of women with dual chamber and rate responsive pacemakers is not easy to evaluate. In addition to the advantages of dual chamber pacemakers in patients with atrioventricular block and sinus node dysfunction mentioned above, rate responsive systems have been shown to offer haemodynamic advantages over fixed rate systems in patients with chronotropic incompetence receiving ventricular single chamber pacing or dual chamber pacing.18 Although there is evidence that patients treated by advanced pacing have a better quality of life,19 it is not known whether this improvement is equal in men and women.
Is there sex discrimination?
What other reasons could there be for doctors deciding in favour of a single chamber pacemaker in women? Firstly, there are some “soft” indications for implanting pacemakers (class II indications in the American College of Cardiology/American Heart Association guidelines2 and corresponding recommendations in many countries, including Germany) Furthermore, guidelines are not always unanimously adhered to in clinical practice.5,20 Doctors are known to behave differently towards men and women as far as both diagnostic and therapeutic strategies are concerned.21 Doctors seeing women with “soft” indications may tend to implant single chamber pacemakers whereas they choose dual chamber for men. Some of the “hard” indications may also be being neglected in women. Women often present their symptoms differently from men.22 They are more likely to receive the same treatment as men if they present their symptoms as men do.23 Finally, we found some published evidence that women sometimes reject sophisticated care in favour of more simple treatments. They may therefore choose not to have dual chamber systems.24
The database we used represents two thirds of the implantations performed in Germany. Since the percentage of reporting hospitals slightly exceeds the percentage of reported implantations, hospitals with a lower frequency of implantations may be overrepresented. However, for this majority of hospitals (72%) sex differences were present in selection of pacemakers. Sex was an independent determinant of choice of pacemaker, with women receiving roughly 20% fewer rate responsive and dual chamber systems then men. Missing data meant that we could include only 16 289 of the 31 913 records in the multivariate logistic regression analysis, and we could not control our data for variables such as left ventricular function, intermittent dysrhythmia, or multimorbidity that might have contributed to the differences found. In addition, our results do not necessarily apply to other countries. However, a similar sex bias has been shown to be likely in the United States at least.16,17 Study limitations and the retrospective design of our analysis do not allow a definite explanation for the sex bias. Prospective studies that include clinical endpoints such as survival or quality of life are needed to investigate this difference in more detail and reveal its potential implications.
Footnotes
Funding: None.
Conflict of interest: None.
References
- 1.Working Party of the British Pacing and Electrophysiology Group. Recommendations for pacemaker prescription for symptomatic bradycardia. Br Heart J. 1991;66:185–191. [PMC free article] [PubMed] [Google Scholar]
- 2.Dreifus LS, Fisch C, Griffin JC, Gilette PC, Mason JW, Parsonnet V. Guidelines for implantation of cardiac pacemakers and antiarrhythmia devices: a report of the American College of Cardiology/American Heart Association Task Force on the assessment of diagnostic and therapeutic cardiovascular procedures (committee on pacemaker implantation) J Am Coll Cardiol. 1991;18:1–13. doi: 10.1016/s0735-1097(10)80209-8. [DOI] [PubMed] [Google Scholar]
- 3.Stangl K, Schüller H, Schulten HK. Recommendations for pacemaker therapy. Herzschrittmacher Elektrophysiol. 1990;1:42–51. [Google Scholar]
- 4.European Working Group on Cardiac Pacing. Cardiac pacing. Eur Heart J. 1987;8(suppl F):21–22. [Google Scholar]
- 5.Ray SG, Griffith MJ, Jamieson S, Bexton RS, Gold RG. Impact of the recommendations of the British Pacing and Electrophysiology Group on pacemaker prescription and on the immediate costs of pacing in the Northern region. Br Heart J. 1992;68:531–534. doi: 10.1136/hrt.68.11.531. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Ayanian JZ, Epstein AM. Differences in the use of procedures between women and men hospitalized for coronary heart disease. N Engl J Med. 1991;325:221–225. doi: 10.1056/NEJM199107253250401. [DOI] [PubMed] [Google Scholar]
- 7.Kjellstrand CM. Age, sex, and race inequality in renal transplantation. Arch Intern Med. 1988;148:1305–1309. [PubMed] [Google Scholar]
- 8.Steingart RM, Packer M, Hamm P, Coglianese ME, Gersh B, Geltman EM, et al. Sex differences in the management of coronary artery disease. N Engl J Med. 1991;325:226–230. doi: 10.1056/NEJM199107253250402. [DOI] [PubMed] [Google Scholar]
- 9.Irnich W, Batz L. Annual report 1993 of central pacemaker register. Herzschrittmacher. 1994;14:239–248. [Google Scholar]
- 10.Alpert MA, Curtis JJ, Sanfelippo JF. Comparative survival after permanent ventricular and dual chamber pacing for patients with chronic high degree atrioventricular block with and without pre-existing congestive heart failure. Am Heart J. 1987;113:958–965. doi: 10.1016/0002-8703(87)90057-3. [DOI] [PubMed] [Google Scholar]
- 11.Hesselson AB, Parsonnet V, Bernstein AD, Bonavita GJ. Deleterious effects of long-term single-chamber pacing in patients with sick sinus syndrome: the hidden benefits of dual-chamber pacing. J Am Coll Cardiol. 1992;19:1542–1549. doi: 10.1016/0735-1097(92)90616-u. [DOI] [PubMed] [Google Scholar]
- 12.Wenger NK, Speroff L, Packard B. Cardiovascular health and disease in women. N Engl J Med. 1993;329:247–256. doi: 10.1056/NEJM199307223290406. [DOI] [PubMed] [Google Scholar]
- 13.Aggarwal RK, Ray SG, Conelly DT, Coulshed DS, Charles RG. Trends in pacemaker mode prescription 1984-1994: a single centre study of 3710 patients. Heart. 1996;75:518–521. doi: 10.1136/hrt.75.5.518. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Khan SS, Nessim S, Gray R, Czer LS, Chaux A, Matloff J. Increased mortality of women in coronary artery bypass surgery: evidence for referral bias. Ann Intern Med. 1990;112:561–567. doi: 10.7326/0003-4819-112-8-561. [DOI] [PubMed] [Google Scholar]
- 15.Mark DB, Shaw LK, DeLong ER, Califf RM, Pryor DB. Absence of sex bias in the referral of patients for cardiac catheterization. N Engl J Med. 1994;330:1101–1106. doi: 10.1056/NEJM199404213301601. [DOI] [PubMed] [Google Scholar]
- 16.Lamas GA, Prosser AP, Edery TP, Lee MT, Berman KE, Levine PA. Age and sex bias in pacemaker selection. Circulation. 1992;86(suppl I):449. [Google Scholar]
- 17.Lamas GA, Pashos CL, Normand SLT, McNeil B. Permanent pacemaker selections and subsequent survival in elderly Medicare pacemaker recipients. Circulation. 1995;91:1063–1069. doi: 10.1161/01.cir.91.4.1063. [DOI] [PubMed] [Google Scholar]
- 18.Proctor EE, Lemann RB, Mann DL. Single versus dual chamber sensor-driven pacing: comparison of cardiac outputs. Am Heart J. 1991;122:728–732. doi: 10.1016/0002-8703(91)90518-m. [DOI] [PubMed] [Google Scholar]
- 19.Lau CP, Tai YT, Lee PWH, Cheung B, Tang MO, Lam WK. Quality-of-life in DDDR-pacing. PACE. 1994;17:1838–1843. doi: 10.1111/j.1540-8159.1994.tb03759.x. [DOI] [PubMed] [Google Scholar]
- 20.Greenspan AM, Kay HR, Berger BC, Greenberg RM, Greenspon AJ, Gaughan MJS. Incidence of unwarranted implantation of permanent cardiac pacemakers in a large medical population. N Engl J Med. 1988;318:158–163. doi: 10.1056/NEJM198801213180306. [DOI] [PubMed] [Google Scholar]
- 21.Armitage KE, Schneiderman LJ, Bass RA. Response of physicians to medical complaints in men and women. JAMA. 1979;241:2186–2187. [PubMed] [Google Scholar]
- 22.Shaw LJ, Miller DD, Romeis JC, Kargl D, Younis LT, Chaitman BR. Gender differences in the noninvasive evaluation and management of patients with suspected coronary artery disease. Ann Intern Med. 1994;120:559–566. doi: 10.7326/0003-4819-120-7-199404010-00005. [DOI] [PubMed] [Google Scholar]
- 23.Healy B. The Yentl syndrome. N Engl J Med. 1991;325:274–276. doi: 10.1056/NEJM199107253250408. [DOI] [PubMed] [Google Scholar]
- 24.Horton HL, Marinchak RA, Rials SJ, Kowey PR. Gender differences in device therapy for malignant ventricular arrhythmias. Arch Intern Med. 1995;155:2342–2345. [PubMed] [Google Scholar]