Ann Thorac Surg 2002;74:1435-1437
© 2002 The Society of Thoracic Surgeons
Editorial
Bilateral internal mammary artery grafting for coronary artery bypass grafting: why men versus women?
Shahbudin H. Rahimtoola, MB, FRCPa*
a George C. Griffith Center, Section of Cardiovascular Medicine, Department of Medicine, and University of Southern California Medical Center and Keck School of Medicine at University of Southern California, Los Angeles, California, USA
* Address reprint requests to Dr Rahimtoola, Keck School of Medicine at University of Southern California, 2025 Zonal Ave, Los Angeles, CA, 90033, USA.
In this issue, Kurlansky and co-workers [1] present 15-years of follow-up data on 261 women and 261 computer-matched men undergoing bilateral internal mammary artery (IMA) coronary artery bypass grafting (CABG) operations between January 1972 and October 1994. Most of the patients were operated on from 1982 to 1994 and 60% were operated on after 1986. There was no significant difference between the two groups in operative mortality and postoperative complications and at 10 and 15 years in survival of patients discharged from hospital. Also there was no significant difference between the two groups in angina, need for reoperation, or percutaneous transluminal coronary angioplasty, and eventfree survival. The very interesting and important findings are (1) that the quality-of-life assessment showed that both men and women scored as well as or better than the general population corrected for age and gender; and (2) although men scored higher in physical health (p = 0.001), women scored higher in mental health (p = 0.011) when compared with their age-adjusted norms.
These are valuable data. However there are several limitations to their study: (1) The number of patients are small and there is no information as to how the 261 women were selected to undergo bilateral IMA; (2) There are no data on the incidence of systolic hypertension and low-density lipoprotein cholesterol at baseline. Of interest is the incidence of unstable angina (73.2% vs 28%), which is said to be statistically nonsignificant; (3) The incidence of hospital mortality of patients who had sternal and mediastinal complications in diabetics and nondiabetics is not given; (4) Criteria and methods used to ascertain cardiac and noncardiac causes of death are not provided, and the actual cardiac causes of death (myocardial infarction, heart failure, and so forth) are not given; (5) Although the lower event-free survival in women was not significant (p = 0.084), the actuarial incidences and p values for the differences of the individual long-term events are not provided; and (6) Long-term management and success of treatment of co-morbid conditions present at baseline are not given, which are almost universal problems in these areas and changes are needed (vide infra).
Areas of concern
Comparison of outcomes: women versus men
- Kurlansky and coworkers [1], and others, have compared long-term outcomes after double IMA CABG in women with those obtained in men with similar baseline characteristics. Is this an appropriate comparison to be undertaken in 2002? Women have a longer expected life span than men and thus it may be preferable to compare their survival with age-matched women in the population. For example, when comparing up to 10 years after CABG in men with different ages at the time of CABG to the expected mortality survival of age- and gender-matched men, these patients in age groups 55 to 64 years and 65 to 74 years had a slightly lower than expected mortality, and in the age group of 75 to 84 years, men had an almost identical expected mortality (Fig 1)
On the other hand, women had a higher mortality than the expected mortality of up to 10 years of follow-up in the age groups 55 to 64 years and 65 to 74 years. However in the age group of 75 to 84 years, women had a much lower mortality than the expected mortality of up to 7 years of follow-up (Fig 1) [2]. Comparison of survival after CABG to the population also is not without problems [3], but in this instance it may be a more appropriate comparison.
- In the last 10 years there have been major advances in the management of patients with coronary artery disease. Appropriate treatment of baseline co-morbid conditions significantly influences long-term survival. For example, in the randomized trial of the Coronary Artery Surgery Study, 10-year survival rates of patients who continued to smoke after CABG was 68%, whereas patients who quit smoking after CABG had a survival rate of 84% (Fig 2)
[4], in other words the mortality rate of patients who continued to smoke was twice that of those who quit smoking. In five large randomized trials published after 1993, of 30,817 patients, HMG–coenzyme A reductase inhibitors (statins) when given for secondary as well as primary prevention have been documented as having beneficial effects on outcome, including longer survival, less subsequent myocardial infarction and less need for angiography and revascularization [5–9]. In the postoperative CABG trial, patients on statins had a reduced progression of atherosclerosis in the coronary bypass grafts than those on placebos [10]. In long-term follow-ups, those patients in the aggressive strategy of statin therapy group had a lower incidence of percutaneous transluminal coronary angioplasty or repeat CABG (Fig 3)
and also a composite end-point of myocardial infarction, stroke, CABG or percutaneous transluminal coronary angioplasty than those in the moderate strategy of statin therapy group [11]. In other words, long-term survival and incidence of angina, myocardial infarction, repeat revascularization, and so forth depends not only on the types of conduits used for CABG but also on how well the associated co-morbid conditions (eg, smoking, hyperlipidemia, hypertension, diabetes, left ventricular dysfunction, heart failure, obesity, renal and pulmonary dysfunction) are treated. It should be noted that use of lipid-lowering therapy after interventions in patients with acute myocardial infarction is very low (Table 1)
[12]; clearly we all have to do better.
- Women with coronary artery disease are being diagnosed later and are treated less aggressively than men. This is now also true for women in the United Kingdom [13]. The largest study that compared outcomes in women versus men showed that the worse outcome in women was due to differences in base line characteristics and not to gender [14]. This was true even though women had smaller coronary arteries; women in general are smaller than men and thus have smaller hearts and smaller arteries.
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Fig 1. Observed mortality after coronary artery bypass grafting compared with the expected age- and gender-matched mortality in the Oregon population in (A) men and (B) women. (CBS = coronary bypass surgery.) (Data from reference 2.)
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Fig 2. Survival after coronary artery bypass grafting in patients who continued to smoke versus those who quit smoking from the 10-year results of the Coronary Artery Surgery Study randomized trial. (Reprinted with permission from the American College of Cardiology [Journal of the American College of Cardiology, 1992, 20, 287–94].)
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Fig 3. Cumulative life table rates for percutaneous transluminal coronary angioplasty or repeat coronary artery bypass grafting (CABG) with different lipid-lowering strategies from the post-CABG Trial. (Reprinted from Knatterud GL, et al, Circulation; 2000; 102:157–65 [11], with permission.)
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The 2002 continued comparison of outcomes in women after CABG with those of men without data on appropriate treatment of co-morbid conditions and the incorrect stating that women have worse outcomes is likely contributing to the problem of late diagnosis and treatment of coronary artery disease in women, which is counterproductive. The conclusion of the 1993 study that CABG "should not be delayed or denied to women who have the usual indications for surgery" [14] should be repeatedly emphasized.
Why double IMA?
A single IMA (left IMA) plus saphenous vein grafts is associated with a better survival and better outcome than with the use of only saphenous vein grafts. If one IMA is good, are two better? In the Oregon study from 1974 through 1991, of 1,979 women and 6,927 men undergoing CABG, most patients received only saphenous vein grafts from 1974 through 1982, and subsequently left internal mammary arteries were used with increasing frequency [15], yet the outcomes were similar to patients reports in the study of Kurlansky and colleagues [1] with use of double IMAs (Table 2). This suggests that additional well designed and properly analyzed studies of double IMAs versus single IMA are needed in patients who are also appropriately treated for their co-morbid conditions.
In summary, the data of Kurlansky and colleagues’ [1] comparison outcomes (particularly quality of life and physical and mental health) in women versus men after double IMAs are of considerable interest. It is clear that differences in outcomes after CABG in women and men are not statistically significant or, if significant, they can be accounted for by differences in co-morbid conditions at base line. Continued statements that women have worse outcomes than men after CABG is counterproductive to the care of women with coronary artery disease. More studies that evaluate the benefits of double IMAs are needed. In 2002, evaluation and comparison outcomes after CABG should take into account the different expected survival of men and women, smoking status, and appropriate and adequate therapy of co-morbid conditions.
References
- Kurlansky PA, Traad EA, Galbut DL, Singer S, Zucker M, Ebra G. Coronary bypass surgery in women: a long-term comparative study of quality of life following bilateral internal mammary artery grafting in men and women. Ann Thorac Surg 2002;74:1517–25
- Rahimtoola S.H., Grunkemeier G.L., Starr A. Ten-year survival after coronary artery bypass surgery for angina in patients aged 65 years and older. Circulation 1986;74(3):509-517.[Abstract/Free Full Text]
- Rahimtoola S.H. Coronary bypass surgery for chronic angina—1981: a perspective. Circulation 1982;65(2):226-241.
- Cavender JB, Rogers WJ, Fisher LD, Gersh BJ, Coggin CJ, Myers WO. Effects of smoking on survival and morbidity in patients randomized to medical or surgical therapy in the Coronary Artery Surgery Study (CASS): 10-year follow-up. J Am Coll Cardiol 1992;20:287–94.
- Scandinavian Simvastatin Survival Study Group. Randomized trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian Simvastatin Survival Study. Lancet 1994;344:1383-1389.[Medline]
- Shepherd J., Cobbe S.M., Ford I., et al. Prevention of coronary heart disease with pravastatin in men with hypercholesterolemia. N Engl J Med 1995;333:1301-1307.[Abstract/Free Full Text]
- Sacks F.M., Pfeffer M.A., Moye L.A., et al. The effect of pravastatin on coronary events after myocardial infarction in patients with average cholesterol levels. N Engl J Med 1996;335:1001-1009.[Abstract/Free Full Text]
- LIPID Study Group. Prevention of cardiovascular events and death with pravastatin in patients with coronary heart disease and a broad range of initial cholesterol levels. N Engl J Med 1998;339:1349-1357.[Abstract/Free Full Text]
- Downs J.R., Clearfield M., Weis S., et al. Primary prevention of acute coronary events with lovastatin in men and women with average cholesterol levels: results of AFCAP/Tex CAPS. JAMA 1998;279:1615-1622.[Abstract/Free Full Text]
- The Post Coronary Artery Bypass Graft Trial Investigators. The effect of aggressive lowering of low-density lipoprotein cholesterol levels and low-dose anticoagulation on obstructive changes in saphenous-vein coronary-artery bypass grafts. N Engl J Med 1997;336:153-162.[Abstract/Free Full Text]
- Knatterud G.L., Rosenberg Y., Campeau L., et al. Long-term effects on clinical outcomes of aggressive lowering of low-density lipoprotein cholesterol levels and low-dose anticoagulation in the Post Coronary Artery Bypass Graft Trial. Circulation 2000;102:157-165.[Abstract/Free Full Text]
- Fonarow G.C., French W.J., Parsons L.S., Sun H., Malmgren J.A. Use of lipid-lowering medications at discharge in patients with acute myocardial infarction. Data from the National Registry of Myocardial Infarction 3. Circulation 2001;103:38-44.[Abstract/Free Full Text]
- Dobson R. Doctors put women at back of heart bypass queue. The Sunday Times of United Kingdom. May 12, 2002:1.7.
- Rahimtoola S.H., Bennett A.J., Grunkemeier G.L., Block P., Starr A. Survival at 15 to 18 years after coronary bypass surgery for angina in women. Circulation 1993;88(Part 2):71-78.
- Rahimtoola S.H., Fessler C.L., Grunkemeier G.L., Starr A. Survival 15 to 20 years after coronary bypass surgery for angina. J Am Coll Cardiol 1993;21:151-157.[Abstract]
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