Original Cardiovascular
Coronary Artery Bypass Surgery in Diffuse Advanced Coronary Artery Disease: 1-Year Clinical and Angiographic Results Luciana Oliveira Cascaes Dourado1 Marcio Sommer Bittencourt2 Alexandre Costa Pereira1 Nilson Tavares Poppi1 Luis Alberto Oliveira Dallan1 José Eduardo Krieger1 Luiz Antonio Machado Cesar1 Luís Henrique Wolff Gowdak1 1 Cardiopneumology department, Heart Institute (InCor), University
of São Paulo Medical School, São Paulo, Brazil 2 Division of Internal Medicine, Center for Clinical and Epidemiological Research, University Hospital, University of São Paulo, São Paulo, Brazil
Address for correspondence Luciana Oliveira Cascaes Dourado, MD, PhD, Heart Institute (InCor), University of São Paulo Medical School, Av. Dr. Enéas Carvalho de Aguiar, 44, 05403-000 São Paulo, Brazil (e-mail:
[email protected]).
Thorac Cardiovasc Surg
Abstract
Keywords
► coronary artery bypass graft surgery ► coronary artery disease ► graft occlusion
received September 27, 2016 accepted after revision February 18, 2017
Background Proper treatment of patients with diffuse, severe coronary artery disease (CAD) is a challenge due to its complexity. Thus, data on the outcomes after coronary artery bypass graft (CABG) in this population is scarce. In this study, we aimed to determine the impact of CABG on the clinical and functional status, as well as graft patency in those individuals. Methods Patients with severe and diffuse CAD who underwent incomplete CABG due to complex anatomy or extensive distal coronary involvement were evaluated preoperatively and 1 year after surgery. Postoperative coronary angiography was performed to evaluate graft patency. Graft occlusion was defined as the complete absence of opacification of the target vessel. Stratified analysis of graft occlusion was performed by graft type and territories, defined as left anterior descending artery (LAD), the left circumflex branch, and the right coronary artery territories; the latter two, grouped, were further classified as non-LAD territory. Results A total of 57 patients were included, in whom 131 grafts were placed. There was a significant improvement in Canadian Cardiovascular Society angina symptom severity (Z ¼ –6.1; p < 0.001) and maximum oxygen uptake (p < 0.001), with a corresponding decrease in the use of long-acting nitrates (p < 0.001). The overall graft occlusion rate was 19.1%, with no significant difference between LAD and nonLAD territories (p ¼ 0.08). However, a significantly lower occlusion rate was noted for the internal mammary artery (IMA) grafts when compared with saphenous vein grafts (p ¼ 0.01), though this difference was only significant in the LAD territory (p ¼ 0.04). Overall, the use of venous graft was the only predictor occlusion at 1 year (odds ratio: 4.03; p ¼ 0.016). Conclusion In patients with diffuse CAD, incomplete CABG surgery resulted in a significant clinical improvement, with acceptable graft occlusion rates at 1 year, particularly for IMA grafts to the LAD territory.
© Georg Thieme Verlag KG Stuttgart · New York
DOI http://dx.doi.org/ 10.1055/s-0037-1601306. ISSN 0171-6425.
Coronary Artery Bypass Surgery in Diffuse Advanced CAD
Introduction Proper surgical treatment for individuals with diffuse severe coronary artery disease (CAD) has been a challenge due to the complex anatomy and its functional and technical implications. Moreover, diffuse CAD is an independent predictor of morbidity and early mortality in patients undergoing coronary artery bypass grafting (CABG),1 particularly due to the overall limited quality of the distal coronary bed, which is known to be critical to for the success of the surgical procedure.2,3 Nevertheless, the data on the impact of the coronary revascularization in territories with diffusely diseased distal coronary beds is limited,1,4,5 though this is particularly important to the long-term graft patency, which is a key parameter of long-term procedural success and outcomes.6 Based on the lack of data evaluating the CABG success in patients with diffuse advanced CAD, this study aimed to determine the 1-year impact of surgical revascularization in patients with unfavorable anatomy, based on clinical improvement and angiographic grafts patency.
Dourado et al. On- and Off-Pump Strategies Conventional coronary artery surgery with cardiopulmonary bypass was accomplished with every effort made to minimize the impact of cardiopulmonary bypass. Patients without diabetes received 1 g of hydrocortisone sodium succinate (SoluCortef, Pharmacia & Upjohn Co., New York, New York, United States) intravenously before anesthesia during onpump technique. Patients were routinely cooled to 34°C, and cold-blood cardioplegia was accomplished with anterograde delivery through the aortic root and retrograde delivery through the coronary sinus. A heparinization protocol of 300 U/kg for on-pump surgery and half-dose heparin for offpump surgery was followed. Protamine was used to reverse the effects of heparinization only for on-pump surgery. All anastomoses were sutured by hand. Off-pump surgery used the Octopus stabilizer. This study was conducted in accordance with the amended Declaration of Helsinki, and the Institutional Ethics and Scientific Committees (3601/11/019) approved the study. All participants gave a signed, written informed consent.
Clinical Assessment
Methods Study Population We included patients with diffuse and severe CAD scheduled for CABG included in the “Multicenter randomized trial of cell therapy in cardiopathies – MiHeart Study.” The rationale, purpose, study design, and research methods were previously published elsewhere.7 In brief, the study tested the hypothesis that stem cells and hematopoietic progenitor cells increases regional perfusion in patients with severe and diffuse CAD undergoing CABG. Diffuse CAD was defined as diffuse atherosclerosis from proximal to distal beds, leading to a threadlike appearance with small (< 1 mm) distal runoff, usually (but not necessarily) involving the three coronary arteries and their major branches simultaneously. All individuals included in the study presented with coronary obstructive lesions not eligible for complete CABG revascularization in the surgeon’s opinion due to the complex anatomical pattern, length of disease, and/or extensive distal coronary bed involvement.
Surgical Technique CABG was performed in accordance with current best practices following the institutional Cardiovascular Surgery Department routine. The surgical technique including performance of on- or off-pump surgery and the total number of saphenous vein and left internal mammary artery (LIMA) bypass grafts used was left to the surgeon’s discretion. The use of a LIMA graft in the left anterior descending artery (LAD) territory was always preferred, except when the LAD territory presented an extensive and diffuse atherosclerotic involvement (in which surgeon anticipated an unsatisfactory surgical result) and/or if LIMA was already used in a previous CABG procedure. Surgical access to the heart was through a standard median sternotomy in all cases. Thoracic and Cardiovascular Surgeon
Medical visits were scheduled preoperatively and every 3 months during the first year after surgery. Each visit consisted of a careful cardiovascular assessment based on a detailed medical history and physical examination including systolic and diastolic blood pressure, heart rate, and body mass index measurements. Angina functional class was evaluated according to the Canadian Cardiovascular Society (CCS) classification.8 Maximum oxygen uptake (VO2 max) was measured by treadmill cardiopulmonary exercise testing. Left ventricular ejection fraction (LVEF) was determined by transthoracic echocardiography.
Angiographic Assessment Per protocol, coronary angiographies were performed 1 year after surgery, regardless of symptoms or noninvasive test results. Graft occlusion was defined as the complete absence of opacification of the target vessel. The rate of graft occlusion was determined by the coronary artery territory grafted following the distribution of the coronary tree: LAD, the left circumflex branch (LCX) of the left coronary artery, and the right coronary artery (RCA); the latter two territories were also analyzed grouped as non-LAD territory.
Statistical Analysis Continuous variables are presented as mean standard deviation, and categorical variables are presented as percentages. For comparison of independent categorical variables, we used the chi-square test. For comparison between time points, we used the paired Student’s t test, McNemar test, or Wilcoxon signed ranks test as appropriate. Logistic regression was used to determine variables independently associated with graft occlusion. Statistical significance was set at p-value of less than 0.05. Statistical analyses were performed using SPSS software version 17.0 for Windows.
Coronary Artery Bypass Surgery in Diffuse Advanced CAD Surgical Performance
Results From the 63 patients initially evaluated, 9 were excluded: 1 died before discharge after surgery (1.6% early mortality) and 5 were lost to follow-up. Therefore, the final sample comprised 57 patients. The baseline demographic and clinical characteristics of patients are shown in ►Table 1. Our population was fairly representative of patients commonly seen with CAD as it basically comprised middle-aged men with a high prevalence of cardiovascular risk factors. CAD severity could be ascertained by a significant proportion of patients having a previous revascularization procedure (percutaneous coronary intervention and/or CABG), and almost all patients with threevessel disease. ►Fig. 1 shows a representative angiographic pattern of one patient included in the study.
Clinical Results At 1-year follow-up, there was a significant improvement in CCS angina functional class, as shown in ►Fig. 2, with reduction of CCS’s 3 and 4 frequency from 29 (51%) patients to 3 (5%) (Z ¼ –6.1; p < 0.001) as well as an increase in VO2 max (►Table 2). These clinical improvements occurred accompanied by a significant decrease in the use of longacting nitrates (►Table 3).
Table 1 Baseline demographic and clinical characteristics of patients Variables
Dourado et al.
N ¼ 57
Male sex (%)
82.5
Age, years (mean SD)
58 9
Past medical history
►Table 4 shows selected aspects of the surgical techniques used during CABG. A total of 131 grafts (2.3 1.1 grafts per patient) were performed distributed as follows: 48 patients received 73 grafts to the LAD territory (43 LIMA grafts and 30 saphenous vein grafts [SVGs]), 33 patients received 34 grafts to the LCX territory (6 LIMA grafts and 28 SVGs), and 24 patients received 24 grafts to the RCA territory (1 LIMA graft and 23 SVGs).
Angiographic Outcomes The 1-year overall graft occlusion rate was 19.1% (25 grafts) on invasive angiography, including 10 (13.7%) grafts to the LAD territory, 10 (29.4%) grafts to the LCX, and 5 (20.8%) grafts to the RCA. Although the graft occlusion rate in the non-LAD territory (25.9%) was twice as high as in the LAD territory (13.7%), this difference did not reach statistical significance (p ¼ 0.08) due to the limited power of our sample size (►Fig. 3). When the analysis was stratified by the graft used, there was a significant lower occlusion rate for LIMA grafts when compared with SVGs (8.0 vs. 25.9%; p ¼ 0.01) (►Fig. 4). When this was further stratified by the grafted coronary territory, a significantly lower occlusion rate was noted for LIMA grafts (7.0%) compared with SVGs (23.3%) in the LAD territory (p ¼ 0.046), though this difference did not reach statistical in significance in the non-LAD territory (14.3 vs. 27.5%; p ¼ 0.5). Conversely, the graft occlusion rate was not influenced by the coronary territory being, as the occlusion rates for LIMA or SVGs were similar across LAD and non-LAD territories (►Fig. 5). In an exploratory analysis to identify factors related to grafts’ occlusion, only graft type was independently associated with graft occlusion. The use of an SVG had a fourfold increased risk for occlusion compared with the LIMA graft (odds ratio ¼ 4.025; 95% confidence interval: 1.29–12.54; p ¼ 0.016).
Previous angioplasty (%)
24.6
Previous CABG (%)
33.3
Previous myocardial infarction (%)
40.4
Discussion
Previous stroke (%)
3.6
This study demonstrates that CABG surgery performed in patients with diffuse advanced CAD has adequate 1-year clinical and angiographic results, despite the complex unfavorable anatomy of the target vessels. Our data suggest a significant overall clinical improvement, with a decrease in symptoms, use of long-acting nitrates, and an improvement in cardiopulmonary performance measured by the VO2 max. Surgical revascularization is an established treatment to relieve angina, reduce the use of antianginal drugs, and improve exercise capacity. Despite the well-documented reduction in all-cause and cardiovascular-specific mortality,9 as well as improvement in the quality of life10 for the general population of surgical candidates, considerably less data are available for individuals with advanced, diffuse CAD. Our study included a group of patients with severe, advanced CAD (90% prevalence of three-vessel disease), with diffuse involvement of the distal coronary bed, and preserved LVEF, in which a complete revascularization was
Hypertension (%)
91.2
Diabetes mellitus (%)
40.4
Smoking (previous or current) (%)
61.4
Hyperlipidemia (%)
87.7
Obesity (%)
47.4
Family history of CAD (%)
36.8
Peripheral arterial disease
7.0
Chronic renal failure
3.5
CAD obstructive pattern (%) One-vessel disease
3.5
Two-vessel disease
7.0
Three-vessel disease
89.5
Abbreviations: CABG, coronary artery bypass graft; CAD, coronary artery disease; SD, standard deviation.
Thoracic and Cardiovascular Surgeon
Coronary Artery Bypass Surgery in Diffuse Advanced CAD
Dourado et al.
Fig. 1 Example of a patient’s angiographic coronary pattern.
Fig. 2 One-year postoperative improvement in angina functional Canadian Cardiovascular Society status.
not deemed possible preoperatively due to the unfavorable anatomy. Although diffuse CAD is considered an independent predictor of morbidity and early mortality in patients undergoing CABG surgery,1 our 1-year mortality of 1.6%, was low
compared with that of McNeil et al,1 who found 7.9% of inhospital mortality and 15.5% of 2-year mortality in patients with diffuse CAD. As planned, the vast majority of the LIMA grafts (43 out of 50) were used in the LAD territory. However, because more than one graft was used in the LAD territory (73 grafts to the LAD territory in total), 30 SVGs had to be used. The surgeon’s decision for using the five remaining LIMA available in nonLAD territories probably reflects the poor quality of the distal coronary bed, which likely impacted on the surgeon’s decision to pursue the LIMA to non-LAD territories. Our arterial graft occlusion of 8% is slightly higher than the LIMA occlusion rate reported in other studies (5% in the first year and 5–10% in 10 years).3,6 This is likely due to the severity and widespread atherosclerotic involvement of the distal target vessels, one of the major determinants of a successful CABG. Similarly, our occlusion rate of 26% in SVGs at 1 year is in accordance with what is found in the literature, from 14 to 30% in 1 year,11–13 and reaching between 40 and 50% in 10 years.3,14 Venous graft occlusion is related to several factors, including the quality, size, and diameter of the saphenous vein, the size and diameter of target coronary artery, the surgeon’s skill and postoperative clinical management.14
Table 2 Comparison of clinical parameters during follow-up Clinical parameters
Preoperative (mean SD)
Postoperative (mean SD)
p-Value
CCS
2.28 1.14
0.36 0.86
0.003
VO2 max (mL/kg/min)
13.9 3.9
16.7 4.1
