|MP 7.01.62||Minimally Invasive Coronary Artery Bypass Graft Surgery|
|Original Policy Date
|Last Review Status/Date
Reviewed with literature search/10:2010
|Return to Medical Policy Index|
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There are currently variations on techniques that are classified as “minimally invasive” coronary artery bypass graft (CABG) surgery. The surgery can be done under direct vision, with a mini-sternotomy or a mini-thoracotomy approach. These types of direct procedures have been termed minimally invasive direct coronary artery bypass (MIDCAB). MIDCAB is performed without cardiopulmonary bypass by slowing the heart rate to 40 beats per minute to minimize motion in the surgical field. The performance of a coronary bypass on a beating heart increases the technical difficulty of the procedure, particularly in terms of the quality of the vessel anastomosis. In MIDCAB, the predominant re-anastomosis performed uses the native internal mammary artery to bypass the left anterior descending coronary (LAD) artery. Bypass of the right coronary artery may also be possible in patients with suitable anatomy.
The surgery can also be performed endoscopically, whereby the internal structures are visualized on a video monitor, and the entire procedure is performed without direct visualization of the operative field. Cardiopulmonary bypass may or may not be used with this technique. This variation of minimally invasive CABG is called port access coronary artery bypass (PACAB) total endoscopic coronary artery bypass (TECAB). Using this approach, theoretically all sides of the heart can be approached. In many instances, only a single bypass of the LAD artery is performed, although multi-vessel bypass of the left and right coronary artery has been performed.
Minimally invasive CABG is a surgical procedure and, as such, is not subject to regulation by the U.S. Food and Drug Administration (FDA). The procedure can be performed with conventional instruments or instruments specifically designed for this purpose. Special instruments designed for these procedures are subject to FDA marketing clearance and several manufacturers have received 510(k) marketing clearance to market devices intended for use in minimally invasive CABG. One such device for computer-assisted surgery or robotic technology is the da Vinci system (Intuitive Surgical, Inc., Mountain View, CA). The da Vinci system received 510(k) marketing clearance from the FDA in 2004 for assisting in coronary artery bypass surgery.
Minimally invasive direct coronary artery bypass graft surgery (MIDCAB), may be considered medically necessary.
Other techniques for minimally invasive coronary artery bypass graft surgery, including but not limited to PACAB, hybrid CABG, or TECAB techniques, are investigational.
In MIDCAB procedures, the vascular anastomoses are hand-sewn under direct vision.
BlueCard/National Account Issues
Minimally invasive CABG may be coded using existing CPT codes for open CABG using arterial grafts. Therefore, it may be difficult to distinguish minimally invasive CABG from open CABG on the basis of CPT codes. However, the most common minimally invasive CABG procedure involves grafting of a single vessel. In contrast, this is an uncommon open procedure, since the majority of patients with a single-vessel stenosis will undergo angioplasty. Therefore, implementation of the above policy may be facilitated by focusing review, preapproval, or precertification protocols on CPT code 33533 (coronary artery bypass, using arterial graft: single arterial graft).
This policy was originally based on a TEC Assessment that was completed first in 1997 and then reviewed again in 1998. (1, 2) The policy was updated regularly with literature searches using the MEDLINE database, the most recent search was through January 2010.
The 1998 TEC Assessment concluded that the evidence did not permit conclusions on the health outcome effects of minimally invasive CABG, particularly whether these effects compared favorably to conventional CABG or percutaneous transluminal coronary angioplasty (PTCA). Data from the available trials indicated that MIDCAB could be performed successfully on most patients, and that recovery time and length of hospital stay was reduced as compared to open CABG. However, the 1998 TEC Assessment noted that it was not yet clear whether the quality of the bypass done with minimally invasive techniques equaled that achieved with either CABG or PTCA. Numerous reports of acute or subacute vessel stenosis following minimally invasive techniques raise the question of whether short-term stenosis of the bypassed vessel occurs with higher frequency than with other approaches. There were no data on long-term patency rates for these procedures.
Since the TEC Assessment, there has been a shift in emphasis from comparing MIDCAB to open CABG to comparing MIDCAB with PTCA and stenting for patients with isolated stenosis of the left anterior descending (LAD) artery. Over this period of time, PTCA and stenting became more established at treating LAD lesions, and open CABG for this indication became less frequent.
At least 5 randomized controlled trials have been published that compare MIDCAB for isolated LAD lesions with PTCA and stenting. These trials were all relatively small, ranging from 100 to 220 enrolled patients. They were performed in Europe or Asia, with no randomized controlled trials (RCTs) having been completed in the United States. Only 1 of these 5 trials used drug-eluting stents, the other trials used bare metal stents in comparison to MIDCAB.
In the largest RCT competed to date, Diegeler et al. (3) randomized 220 patients to MIDCAB or PTCA plus stenting and reported outcomes up to 6 months following treatment. In the MIDCAB group, 2 deaths occurred within 30 days of surgery compared with none for PTCA (p =0.99). At 6 months, the combined rate of death and myocardial infarction (MI) was 6% for MIDCAB and 3% for PTCA (RR 2.33 for MIDCAB); this difference had a wide confidence interval and was not statistically significantly different from PTCA (95% CI: 0.34–43.73, p =0.50). A greater percentage of MIDCAB patients were angina-free after surgery (79% vs. 62%, p =0.03), and the MIDCAB patients required fewer reinterventions at 6 months (5% vs. 27%, p =0.02).
Thiele et al. (4) published a 5-year follow-up of this RCT comparing clinical outcomes between groups. Mortality was similar in patients who had undergone MIDCAB and those who had undergone percutaneous coronary intervention (PCI; 12% vs. 10%, p =0.5). There were also no differences in cardiac death (5% vs. 4%, p =0.60) or myocardial infarction (MI; 7% vs. 5%, p =0.71). Target vessel revascularization was significantly lower for the MIDCAB group compared to PCI (10% vs. 32%, p <0.001).
Drenth and colleagues reported the results of a trial that randomized 102 patients with isolated high-grade stenosis of the proximal LAD to either MIDCAB or stenting. (5) At 6 months, quantitative coronary angiography showed an anastomotic stenosis rate of 4% after MIDCAB compared to 29% after stenting, although the clinical outcomes in the two groups were similar. Two patients died after MIDCAB compared to none after stenting.
Reeves et al. randomized 100 patients to MIDCAB or PTCA and found no significant differences when evaluating angina symptoms or disease-specific or generic quality of life. (6) The authors estimated 12-month cumulative hazard rates for MIDCAB were 7.1% and 9.2% for PTCA and concluded that there was no evidence that MIDCAB was more effective than PTCA.
Kim et al. randomized 100 patients with LAD stenosis >70% and stable or unstable angina to MIDCAB or PTCA with bare metal stents (7). There were a small number of in-hospital events, with no difference between groups. At 1 year, mortality was equal at 4%, and more patients in the PCI group required target vessel revascularization (7 vs. 1, p <0.001).
Hong et al. enrolled 189 symptomatic patients with isolated high-grade stenosis of the LAD artery to MIDCAB or PCI with drug-eluting stents. (8) The in-hospital complication and death rates did not differ among the groups. At 6 months’ follow-up, there were no significant differences in death, MI, or target vessel revascularization.
Cisowski et al. randomized 100 patients with Canadian Cardiovascular Society (CCS) angina class II-IV and isolated stenosis of the LAD of greater than 70% to MIDCAB or PCI with bare metal stenting (9). At 30-day follow-up there were no deaths and 1 MI in the PCI group. Freedom from angina at 30 days was 98% in the MIDCAB group and 88% in the PCI group, a difference that was not statistically significant. At 6 months, fewer patients in the MIDCAB group required target vessel revascularization (2% vs. 18%, p <0.01). At 1-year follow-up there was no difference in mortality or other adverse cardiac events between groups. Freedom from angina was greater in the MIDCAB group (100% vs. 75%, p <0.01).
None of the trials reviewed were designed or powered to test equivalence between groups; therefore, studies reporting equivalent outcomes are prone to a type II error. The main limitation to this evidence is the possibility of a type II error, i.e., that these trials do not contain adequate power to demonstrate a meaningful clinical difference that might be present. In addition, it should also be noted that drug-coated stents, designed to reduce the restenosis rate, are now commercially available and widely used. Thus, the restenosis rates associated with bare metal stenting reported in these trials may not reflect the current practice. It is notable that the only trial that used drug-eluting stents (8) reported no difference in target vessel revascularization at 6 months.
A number of meta-analyses have been published analyzing this body of RCT’s (10-12). While the studies included varied slightly, the conclusions of these analyses were relatively consistent. None of the analyses established any peri-operative or in-hospital differences in mortality, MI, or other adverse events. Even with pooling of the studies, however, there were only a small number of clinical events to be compared, and these meta-analysis were not likely to have adequate power to detect small- to moderate-sized differences in peri-operative outcomes. Similarly, none of the meta-analyses demonstrated any differences in long-term clinical adverse events such as mortality or MI. All 3 meta-analyses concluded that medium- to long-term target vessel revascularization was less commonly required for patients receiving MIDCAB than for patients receiving PCI, and 2 concluded that angina recurrence was less for the MIDCAB group. Accordingly, combined outcomes that included revascularization and/or angina recurrence were significantly better for the MIDCAB group while combined outcomes that did not include revascularization or angina recurrence showed no significant difference between groups. As noted previously, only 1 of the randomized trials used drug-eluting stents.
In a randomized trial using non-inferiority analysis from Europe, Thiele and colleagues evaluated MIDCAB versus sirolimus-eluting stents (SES) for isolated proximal left anterior-descending artery (LAD) disease. (13) Sixty-five patients were randomized to each group between 2003 and 2007. Approximately 25% of both groups had diabetes; average age was 66 years and 70% were males. In total, 3.1% of stent patients had at least one post-procedure event compared to 16.9% after MIDCAB (p = 0.02). Median length of hospitalization was 3 days in the stenting group and 13 days in the MIDCAB patients (p < 0.001). At 12 months, the rate of major adverse cardiac events (MACE) was equivalent; 7.7% for stenting and 7.9% for MIDCAB. There were no cardiac deaths in either group at 12 months. There were more revascularizations in the stent group (6.2% vs. 0%), but more acute myocardial infarctions (all within 30 days) in the MIDCAB group (1.5% vs. 7.7%). The authors concluded that at 12 months, SES is non-inferior to MIDCAB with respect to MACE at a similar relief in clinical symptoms.
No new comparative trials were identified during the 2010 literature search. Kofidis and colleagues published follow-up on 390 patients who had MIDCAB for LAD coronary artery disease beginning in 1996. (14) The average age was 61 years, 69% were males. Early postoperative mortality was 0.8% and myocardial infarction occurred in 1.3%. The authors report a 97.5% patency rate based on 238 of the 390 patients (61%), and that 74% had no stenosis at late angiography based on results for 78 patients. The authors concluded that MIDCAB is a safe procedure with long-term anastomotic patency rates comparable with those of open-chest left-internal-mammary-artery to LAD bypass.
Kettering performed a literature search for all published outcome studies of MIDCAB grafting for the period from January 1995 through October 2007. (15) Seventeen articles were identified for this analysis. The data presented in the studies was analyzed with regard to clinical and angiographic results. Early and late (> 30 days after MIDCAB) death rates were 1.3% (51/4081 patients) and 3.2% (130/4081 patients), respectively. The infarct rate was 0.8% (32/4081 patients; non-fatal myocardial infarction). Other minor or major complications (e.g., reoperation for management of bleeding, chest wound problems, arrhythmias, cerebrovascular accident, pericardial effusion, pulmonary complications) were reported in 781 cases. The conversion rate to sternotomy/cardiopulmonary bypass was 1.8% (74/4081 patients). A re-intervention due to graft failure was necessary in 134/4081 patients (3.3%). A total of 2556 grafts were studied angiographically immediately after surgery. One hundred and six grafts (4.2%) were occluded and 169 grafts (6.6 %) had a significant stenosis (50-99%). At 6-month follow-up, 445 grafts were studied angiographically. Sixteen grafts (3.6%) were occluded and 32 grafts (7.2%) had a significant stenosis. The authors concluded that clinical outcomes and immediate graft patency after MIDCAB are acceptable; however, long-term follow-up results and further randomized prospective clinical trials comparing this technique with standard revascularization procedures in large patient cohorts are needed.
In summary, the data from these clinical trials demonstrate that MIDCAB can be performed with low surgical morbidity and mortality and with a high percentage of patients reporting relief from angina. Compared with PTCA and stenting (bare metal), MIDCAB reduces the future occurrence of angina and reduces the need for future revascularization procedures. However, the data do not demonstrate differences in other clinical outcomes such as MI or mortality; but, studies were not large enough to detect potential meaningful differences. The relevance of decreased angina and revascularization to current clinical practice is lessened by the fact that the majority of these trials employed bare metal stents, as opposed to drug-eluting stents.
PACAB, TECAB and Hybrid CABG
There is scant evidence from clinical trials on the impact of PACAB or total endoscopic CABG (TECAB, an alternative term for PACAB) on health outcomes. Dogan and colleagues reported on the results of a trial that randomized 40 patients who required multivessel revascularization to undergo either conventional CABG or PACAB. (16) However, this study only reported short-term outcomes of the procedure, i.e., intraoperative time, cardiopulmonary bypass time, hospital stay, etc., and not long-term outcomes.
TECAB is an alternative name for PACAB. Some centers have instituted robotic-assisted TECAB with the da Vinci® robotic system, which can be performed either with cardiopulmonary bypass (on-pump) or on the beating heart (off-pump). To date, studies of this procedure consist of pilot studies intended to demonstrate feasibility (17), and a number of single-arm case series that report clinical outcomes (18-20). Some of these series report outcomes that may be comparable to conventional CABG (18), but others report clinical outcomes that may be inferior to those expected with conventional CABG (20). No clinical trials were identified that directly compare TECAB with alternatives such as conventional CABG, MIDCAB, or PTCA.
A multicenter randomized trial was conducted in the VA system comparing on-pump to off-pump CABG. (21) This trial involved randomly assigning 2203 patients who were scheduled for urgent or elective CABG to an on-pump or off-pump procedure. In some cases, complete revascularization was performed for all areas of the heart. About two-thirds of cases involved intervention on 3 vessels. At 1 year of follow-up, patients in the off-pump group had worse composite outcomes and poorer patency than those in the on-pump group. Fewer grafts were completed than had been planned for those in the off-pump group. In this study, there were no differences in neuropsychological outcomes. While this study does not support use of off-pump CABG, a number of concerns have been raised about this study including the relative level of skill in those doing the on-pump compared to the off-pump procedures. (22)
Another variation on PACAB is “hybrid” or “integrated” CABG, in which PACAB is combined with PTCA and stenting to treat multivessel CAD. Studies to date on this approach consist mainly of small case series intended to demonstrate feasibility and safety of this procedure. (23)
Thus, none of the MEDLINE searches of peer-reviewed literature for the period of April 2005 through January 2010 identified clinical trials that would alter the conclusions reached above for either PACAB, TECAB (including robotically assisted), or hybrid CABG. As a result, the evidence remains insufficient to determine whether PACAB, TECAB, and/or hybrid CABG improve outcomes compared to conventional procedures. The policy statement for these procedures therefore remains unchanged. Additional randomized comparative studies are needed that compare the relevant short and long-term outcomes from these new techniques with outcomes obtained using the current approaches.
Clinical Input Received through Physician Specialty Societies and Academic Medical Centers
While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.
In response to requests, input was received from 1 physician specialty society and 4 academic medical centers while this policy was under review in 2010. All of those providing input agreed with the conclusions of this policy regarding TECAB. The MIDCAB procedure was supported by a majority of those providing input.
Given the clinical data summarized earlier in this document and the clinical support, MIDCAB (CABG with anastomoses hand sewn under direct vision) may be considered medically necessary. Given both the limited clinical data and the lack of clinical support, other minimally invasive approaches to CABG such as TECAB are considered investigational.
A search for relevant clinical studies of these procedures identified 1 trial. It is a non-comparative trial involving 50 patients, entitled Coronary Stenting and Coronary Bypass Grafting [TECAB] at the Same Time in a Specialty Built Operating Room. (24) This trial is being conducted by the Lawson Health Research Institute under the Canadian Foundation for Innovation, Ontario Innovative Trust. While results were expected in early 2009, the information on clinicaltrials.gov was last updated October 2008. No U.S.-based trials were identified.
- Blue Cross and Blue Shield Association Technology Evaluation Center (TEC). Minimally invasive coronary artery bypass graft surgery. TEC Assessments 1997; Volume 12, Tab 13.
- Blue Cross and Blue Shield Association Technology Evaluation Center (TEC). Minimally invasive coronary artery bypass graft – update. TEC Assessments 1998; Volume 13, Tab 15.
- Diegeler A, Thiele H, Falk V et al.Comparison of stenting with minimally invasive bypass surgery for stenosis of the left anterior descending coronary artery. N Engl J Med 2002; 347(8): 561-6.
- Thiele H, Oettel S, Jacobs S et al. Comparison of bare-metal stenting with minimally invasive bypass surgery for stenosis of the left anterior descending artery; a five-year follow-up. Circulation 2005; 112(22):3445-50.
- Drenth DJ, Winter JB, Veeger NJ et al.Minimally invasive coronary artery bypass grafting versus percutaneous transluminal coronary angioplasty with stenting in isolated high-grade stenosis of the proximal left anterior descending artery: six months’ angiographic and clinical follow-up of a prospective randomized study. J Thorac Cardiovasc Surg 2002; 124(1):130-5.
- Reeves BC, Angelini GD, Bryan AJ et al.A multi-centre randomised controlled trial of minimally invasive direct coronary bypass grafting versus percutaneous transluminal coronary angioplasty with stenting for proximal stenosis of the left anterior descending coronary artery. Health Technol Assess 2004; 8(16):1-43.
- Kim JW, Lim DS, Sun K et al. Stenting or MIDCAB using ministernotomy for revascularization of proximal left anterior descending artery? Int J Cardiol 2005;99(3):437-41.
- Hong SJ, Lim D-S, Seo HS et al. Percutaneous coronary intervention with drug-eluting stent implantation vs. minimally invasive direct coronary artery bypass (MIDCAB) in patients with left anterior descending coronary artery stenosis. Catheter Cardiovasc Interv 2005; 64(1):75-81.
- Cisowski M, Drzewiecki J, Drzewiecka-Gerber A et al. Primary stenting versus MIDCAB: preliminary report - comparison of two methods of revascularization in single left anterior descending coronary artery stenosis. Ann Thorac Surg 2002; 74(4):S1334-9.
- Aziz O, Rao C, Panesar SS et al. Meta-analysis of minimally invasive internal thoracic artery bypass versus percutaneous revascularization for isolated lesions of the left anterior descending artery. BMJ 2007; 334(7594):617-24.
- Bainbridge D, Cheng D, Martin J et al. Does off-pump or minimally invasive coronary artery bypass reduce mortality, morbidity, and resource utilization when compared with percutaneous coronary intervention? A meta-analysis of randomized trials. J Thorac Cardiovasc Surg 2007;133(3):623-31
- Jaffery Z, Kowalski M, Weaver WD et al. A meta-analysis of randomized control trials comparing minimally invasive direct coronary bypass grafting versus percutaneous coronary intervention for stenosis of the proximal left anterior descending artery. Eur J Cardiothorac Surg, 2007;31(4):691-7.
- Thiele H, Neumann-Schniedewind P, Jacobs S et al. Randomized comparison of minimally invasive direct coronary artery bypass surgery versus sirolimus-eluting stenting in isolated proximal left anterior descending coronary artery stenosis. J Am Coll Cardiol 2009; 53(25):2324-31.
- Kofidis T, Emmert MY, Paeschke HG et al. Long-term follow-up after minimal invasive direct coronary artery bypass grafting procedure: a multi-factorial retrospective analysis at 1000 patient-years. Interact Cardiovasc Thorac Surg 2009; 9(6):990-4.
- Kettering K. Minimally invasive direct coronary artery bypass grafting” a meta-analysis. J Cardiovasc Surg (Torino) 2008; 49(6):793-800.
- Dogan S, Graubitz K, Aybek T et al. How safe is the port access technique in minimally invasive coronary artery bypass grafting? Ann Thorac Surg 2002; 74(5):1537-43.
- Mishra YK, Wasir H, Sharma KK. Totally endoscopic coronary artery bypass surgery. Asian Cardiovasc Thorac Ann 2006; 14(6):447-51.
- de Canniere D, Wimmer-Greinecker G, Cichon R et al. Feasibility, safety, and efficacy of totally endoscopic coronary artery bypass grafting: multicenter European experience. J Thorac Cardiovasc Surg 2007; 134(3):710-6.
- Argenziano M, Katz M, Bonatti J et al. Results of the prospective multicenter trial of robotically assisted totally endoscopic coronary artery bypass grafting. Ann Thorac Surg 2006; 81(5):1666-75.
- Kappert U, Tugtekin SM, Cichon R et al. Robotic totally endoscopic coronary artery bypass: a word of caution implicated by a five-year follow-up. J Thorac Cardiovasc Surg 2008; 135(4):857-62.
- Shroyer AL, Grover FL, Hattler B et al. On-pump versus off-pump coronary-artery bypass surgery. N Engl J Med 2009; 361(19):1827-37.
- Puskas JD, Mack JM, Smith CR. Letter to the editor. On-pump versus off-pump CABG. N Engl J Med 2010; 362(9):851.
- Bonatti J, Schachner T, Bonaros N et al. Simultaneous hybrid coronary revascularization using totally endoscopic left internal mammary artery bypass grafting and placement of rapamycin eluting stents in the same interventional session. The COMBINATION pilot study. Cardiology 2008; 110(2):92-5.
- http://clinicaltrials.gov/ct2/show/NCT00366015. Accessed February 26, 2010.
||Coronary artery bypass, using arterial graft(s); single arterial graft|
|33534||Coronary artery bypass, using arterial graft(s); two coronary arterial grafts|
|33535||Coronary artery bypass, using arterial graft(s); three coronary arterial grafts|
|33536||Coronary artery bypass, using arterial graft(s); four or more coronary arterial grafts|
|ICD-9 Procedure||17.44||Endoscopic robotic assisted procedure (new code 10/01/08)|
||Aortocoronary bypass of one coronary artery|
|36.12||Aortocoronary bypass of two coronary arteries|
|36.13||Aortocoronary bypass of three coronary arteries|
|36.14||Aortocoronary bypass of four or more coronary arteries|
|36.15||Single internal mammary coronary artery bypass|
|36.16||Double internal mammary coronary artery bypass|
|ICD-9 Diagnosis||414.00 – 414.07||Coronary atherosclerosis code range|
|HCPCS||S2205||Minimally invasive direct coronary artery bypass surgery involving mini-thoracotomy or mini-sternotomy surgery, performed under direct vision; using arterial graft(s), single coronary arterial graft|
|S2206||Minimally invasive direct coronary artery bypass surgery involving mini-thoracotomy or mini-sternotomy surgery, performed under direct vision; using arterial graft(s), two coronary arterial grafts|
|S2207||Minimally invasive direct coronary artery bypass surgery involving mini-thoracotomy or mini-sternotomy surgery, performed under direct vision; using venous graft only, single coronary venous graft|
|S2208||Minimally invasive direct coronary artery bypass surgery involving mini-thoracotomy or mini-sternotomy surgery, performed under direct vision; using single arterial graft and venous graft(s), single venous graft|
|S2209||Minimally invasive direct coronary artery bypass surgery involving mini-thoracotomy or mini-sternotomy surgery, performed under direct vision; using two arterial grafts and single venous graft|
|Type of Service||Cardiac Surgery|
|Place of Service||Inpatient|
CABG, Minimally Invasive
Coronary Artery Bypass Graft, Minimally Invasive
Minimally Invasive CABG
Port Access Coronary Artery Bypass
|01/16/98||Add to Surgery section||New policy|
|10/08/02||Replace policy||Policy reviewed, references added; no change in policy statement
|02/25/04||Replace policy||Policy updated with literature review; references added; no change in policy statement
|06/27/05||Replace policy||Literature review update for the period of November 2003 through April 2005; reference number 5 added. Policy statement unchanged
|07/20/06||Replace policy||Literature review update for the period of April 2005 through June 2006; policy statement unchanged. Information on robotic CABG added to the discussion section. References numbers 10 and 11 added
|09/11/08||Replace policy||Policy updated with literature review in August 2008; new reference numbers 4, 7, 8, 10 to 12, 14, 15, 17 to 19 added, other references renumbered. TECAB added to policy statement; no other changes to policy statement.|
|04/08/10||Replace policy||Policy updated with literature search; reference numbers 13-15, 21-22 added; other references renumbered. Policy statement unchanged|
|10/08/10||Replace policy||Clinical input reviewed, policy statement changed to indicated that MIDCAB may be considered medically necessary, other procedures still considered investigational|