Asian Cardiovasc Thorac Ann 1999;7:33-36
© 1999 Asia Publishing EXchange Pte Ltd
Surgery for Combined Rheumatic Valve and Coronary Artery Disease
Birol Yamak, MD,
A Tulga Ulus, MD,
S Fehmi Katircio
lu, MD,
Binali Mavita
, MD,
Ahmet Sarita, MD,
Ouz Tademir, MD,
Kemal Bayazit, MD
Department of Cardiovascular Surgery Türkiye Yüksek  htisas Hospital Sihhiye, Ankara, Turkey
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For reprint information contact: Birol Yamak, MD Tel: 90 312 310 3080 Ext. 1247 Fax: 90 312 466 3202 email: ulus{at}escortnet.com Department of Cardiovascular Surgery, Türkiye Yüksek htisas Hospital, Sihhiye, Ankara 06100, Turkey.
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Abstract
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Between 1986 and 1996, 147 patients underwent valve replacement combined with coronary artery bypass grafting. The mitral valve was replaced in 104 patients, the aortic valve in 34, and both mitral and aortic valves were replaced in 9. One hundred and twenty-two (83%) were male with a mean age of 56 ± 5 years (range, 38 to 77 years). The mean age for female patients was 57.9 ± 5 years (range, 38 to 70 years). All of the patients had rheumatic valve disease. Preoperatively, 68% were in New York Heart Association functional class III or IV and 32% were in class II. A total of 252 distal anastomoses were performed (mean, 1.71 per patient) in these patients of whom 48.9% had single-vessel disease, 45% had two-vessel or three-vessel disease, and 6.1% had left main coronary artery disease. The hospital mortality rate was 10.2%. Three patients died during the follow-up period and the overall actuarial survival rate at 10 years was 96.6% ± 1.9%. Operations that combine both valve replacement and coronary artery bypass are performed more frequently because perioperative risk has decreased through more effective myocardial protection. If untreated, both coronary artery disease and significant valve disease may reduce patient survival.
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Introduction
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Aortic valve replacement (AVR) combined with coronary artery bypass grafting (CABG) has a slightly higher operative mortality than isolated CABG.1 Mitral valve disease may be rheumatic, degenerative, or ischemic and the etiology and severity of the disease influence the results of the combined operation.2 Patients with rheumatic heart disease have an operative mortality rate of 3% to 20% for combined mitral valve replacement (MVR) and CABG.2
In circumstances where coronary artery disease and significant aortic valve disease coexist, either of these if left untreated may reduce patient survival.2 Survival of patients surgically treated for valvular heart disease may be compromised by the presence of associated coronary artery disease. Reliable assessment of the results of isolated mitral valve surgery in patients with coexisting coronary artery disease is not available.3 Approximately 15% to 20% of patients undergoing mitral valve replacement for nonischemic mitral valve disease in recent years have undergone concomitant coronary artery bypass grafting.4,5
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Materials and Methods
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Between 1986 and 1996, 147 patients underwent combined valve replacement and CABG at the Türkiye Yüksek htisas Hospital. The mitral valve was replaced in 104 patients, the aortic valve in 34, and both mitral and aortic valves were replaced in 9. Patient characteristics are listed in Table 1
. Previous operations included closed mitral valvotomy in 3 patients, open mitral valvotomy in one, and mitral valve replacement with a bioprosthesis in 3. All of the patients had rheumatic valve disease. Preoperatively, 68% were in New York Heart Association (NYHA) functional class III or IV and 32% were in class II. Coronary angiography was routinely performed in male patients over the age of 40 years and in female patients over 45 years. The incidence of CABG among young rheumatic patients was 5.7%. Scoring for left ventricular performance was carried out according to the modified Cleveland Clinic method. The left ventricle was divided into 7 segments and points were allocated according to segmental movement: normal = 1; hypokinetic = 2; akinetic = 3; dyskinetic = 4; aneurysmal = 5. Thus, a score of 7 implies normal ventricular function, 8 to 14 is considered mild ventricular impairment, 15 to 21 is moderate impairment, and 22 to 35 is severe impairment.
Operative Technique
All operations were performed using standard techniques of cardiopulmonary bypass using a membrane oxygenator (Terumo-Capiox E; Terumo Corp., Tokyo, Japan). Moderate total body hypothermia (28oC to 30oC), cold potassium cardioplegia, and topical cooling were used for myocardial protection. All valve replacements were performed with St. Jude Medical heart valve prostheses (St. Jude Medical, St. Paul, MN, USA) using simple interrupted sutures. Pledget-supported U-sutures were used if the annulus was heavily calcified. Concomitant procedures comprised tricuspid annuloplasty in 3 patients, open aortic valvotomy in 2, atrial septal defect closure in 2, and a composite graft (replacement of the aortic arch by the elephant trunk technique) in one patient.
Hemodynamically stable patients were extubated as soon as they recovered from the anesthesia. These patients received 2.5 mg per day of sodium warfarin following extubation. In addition, they received dipyridamole (225 mg per day) and aspirin (250 mg per day) following removal of the mediastinal tubes. All patients continued to use this regimen of oral anticoagulation after discharge from the hospital.
Statistical Methods
Standard actuarial (life-table method) and linearized statistical techniques were used to calculate the actuarial survival rate with 95% confidence limits. The incidence of valve-related events and their consequences were calculated as described by Grunkemeier and Starr6 and Bodnar and colleagues.7 In addition, we calculated the actuarial survival rate and freedom from valvular dysfunction at 10 years. Definitions of valve-related events were analyzed according to the guidelines for reporting morbidity and mortality after cardiac valvular operations.8 Valve-related events were classified as valvular dysfunction, thromboembolism, anticoagulant-related hemorrhage, and paravalvular leak.
During the statistical calculations and analyses of the follow-up data, patients who died during the operation or before their discharge from the hospital were included in the hospital mortality. Patients who died later due to unknown causes were not added to the number of valve-related deaths but were included in the actuarial survival rate calculations. Patients with inoperable valvular dysfunction diagnosed at their last follow-up examination and patients who were lost to follow-up were added to the withdrawal group and valve-related complication calculations. In calculating event-free survival rates, thromboembolism, valvular dysfunction, and anti-coagulant-related hemorrhages were included whether or not the event ended in death. Cox and Kaplan-Meier tests were used to detect the differences. A p value of less than 0.05 was considered statistically significant. All values are reported as mean ± standard deviation.
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Results
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A total of 252 distal anastomoses were performed (mean, 1.71 per patient). Internal mammary artery grafts were used in 79 distal anastomoses (Table 1
). The mean cross-clamp time was 82.3 minutes and mean total perfusion time was 131 minutes. Left ventricular scoring showed that 38 patients (26%) had normal left ventricular performance, 88 (60%) had mild impairment, 14 (10%) had moderate impairment, and 7 (5%) had severe impairment.
Fifteen patients died early after surgery or before discharge giving an overall hospital mortality of 10.2%. The early mortality for AVR was 8.7%, for MVR it was 8.8%, and for double-valve replacement it was 33%. Most of the deaths were attributed to low cardiac output. Four of these patients had a previous operation and the others had severe pulmonary hypertension. All 15 patients were in NYHA functional class III or IV; 9 were female and 6 were male. Female gender was found to be an independent risk factor (p < 0.05) for early mortality. The type and number of conduits were not found to be incremental risk factors for mortality and they did not affect the late survival curves. However, aortic cross-clamp time was found to be a significant risk factor for hospital mortality.
Follow-up information was obtained mainly from the outpatient clinic at our institute and patient questionnaires. The follow-up was complete for 96% of the study group. The total cumulative follow-up was 479.31 patient-years with a mean follow-up of 1.42 ± 1.2 years (range, 2 months to 8.3 years). Three patients died during the follow-up period. Two of these deaths resulted from prosthetic valve thrombosis and the other was due to an unknown cause. The linearized rate of late mortality was 0.63% per patient-year and the overall actuarial survival rate for 10 years was 96.6 ± 1.9% (Figure 1).
At each follow-up examination, hemoglobin, hematocrit values, prothrombin time, and international normalized ratios were measured. During the follow-up period, the mean international normalized ratio was 1.61 ± 0.61 (range, 1 to 2.8), the mean prothrombin time was 14.66 ± 2.27 (range, 12.0 to 18.4), mean prothrombin activity was 58% ± 25% (range 28% to 95%), and mean hematocrit was 40.1 ± 4.4 (range, 31 to 45).
There were two thrombotic events during the follow-up period (incidence, 0.42% per patient-year). Both cases were peripheral arterial thromboembolism. The actuarial estimate of the probability of freedom from thrombo-embolism was 94.7% ± 3% at 10 years (Figure 2).
There was one anticoagulant-related hemorrhage (gastrointestinal) in a patient who had inadvertently taken warfarin in doses 3 or 4 times higher than that prescribed. The linearized occurrence rate of anticoagulant-related hemorrhage was 0.2% per patient-year and the probability of freedom from oral anticoagulant-related bleeding was 96.5% ± 2.4% at 10 years (Figure 3).
All valve-related complications, which included valve-related death, reoperation, thromboembolism, and anticoagulant-related hemorrhage were taken into account in the linearized rate of 0.63% per patient-year. Paravalvular leak was not identified during the follow-up period. In the 10 years of follow-up, 3 patients underwent reoperation (0.63% per patient-year). In two cases, this was due to mechanical valve dysfunction and the other reoperation was for a dissecting aneurysm of the ascending aorta.
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Discussion
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Valve replacement in patients who require CABG for associated coronary artery disease presents a unique problem in achieving and maintaining adequate myocardial protection. Earlier studies of simultaneous valve replacement and CABG showed a higher risk for the combined procedure.9 More recent experience has shown improved results in terms of early mortality, approaching that for valve operation alone.10 Our results were similar to published data for overall (10.2%), MVR (8.8%), and AVR (8.7%) early mortality rates.3,10
Pulmonary artery hemodynamics, especially pulmonary vascular resistance, can affect early mortality and late survival after combined MVR and CABG. Rheumatic mitral disease is a chronic condition and most patients had extremely high pulmonary artery pressure and pulmonary vascular resistance. High pulmonary vascular resistance and advanced NYHA functional class are associated with less favorable early and late survival.11,12
Although sex had little influence in most series, female sex was found to be an independent risk factor for early mortality in our study. A report from the Mayo Clinic showed that female gender, renal impairment, ejection fraction less than 0.35, and chronic obstructive pulmonary disease were the most important risk factors.12 Skupin and colleagues13 also found that mortality among female patients was higher than male patients.
Replacement of both the mitral and aortic valves combined with CABG was associated with a high hospital mortality rate (33%). Double-valve replacement and concomitant CABG requires a long aortic cross-clamp time that may explain this high operative mortality. Preoperative left ventricular function has been found to be a determinant of late survival in most studies on isolated valve replacement, valve replacement with CABG, and CABG alone.13 We calculated the left ventricular performance score for all patients. Those with normal or mildly impaired left ventricular function had a better early postoperative period and a higher rate of late survival. Although the performance score was not found to be a statistically significant risk factor for the early mortality in this study, patients who died and those in NYHA functional class IV in the late postoperative period had severely impaired left ventricular function.
The presence of single-vessel or multiple-vessel disease at coronary angiography did not effect early survival in this study. The prevalence of a good functional status (NYHA class I or II) among patients surviving at least intermediate-term after mitral valve replacement and concomitant CABG is as high as after isolated MVR.4 Although late survival in some of the large reported series was influenced by the extent of coronary artery disease, the impact of this factor is somewhat unpredictable. Late survival in patients undergoing valve replacement together with CABG is similar to that of patients having isolated valve replacement once coronary artery disease is corrected.2,3
We recommend that patients with rheumatic heart valve disease who are over 40 years of age should be investigated for coronary artery disease by coronary angiography. Combined valve replacement and CABG should be performed when the distal coronary artery is suitable for grafting. If untreated, both coronary artery disease and significant valve disease may reduce patient survival.
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Acknowledgments
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Statistical analyses were made by Kenan Köse from the Department of Biostatistics, University of Ankara.
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References
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Abstract
Introduction
