The options for revascularization in patients with coronary artery disease (CAD) increasingly appear to be in direct competition with each other.
The long-established role of coronary artery bypass graft (CABG) surgery is being challenged by the outcomes achieved with percutaneous coronary intervention (PCI) deploying drug-eluting stents (DESs).
The ongoing SYNTAX (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) Trial comparing CABG to PCI with DES for patients with multivessel CAD or left main CAD has shown, in early follow-up, similar early survival in both treatment groups. The trial does recognize the limitations of PCI in patients with complex anatomy in the coronary lesions (calcification, sequential lesions, bifurcation lesions, and so on) and suggests more limited durability of PCI.
There may be a better way to approach this evolving field. From the patient's perspective, it is not a question of one technique (provided by one type of specialist) winning out over another technique (provided by another type of specialist). Rather, patients expect the best treatment approach based on their coronary disease, anatomy, and comorbid conditions with the goals of a good outcome while minimizing risk and allowing early return to their normal activities.
"A hybrid approach that would combine the advantages of CABG and the advantages of PCI might be the optimal approach available for treating CAD today," according to Richard C. Daly, M.D., a cardiovascular surgeon at Mayo Clinic.
PCI has the obvious advantage of being minimally invasive with minimal patient discomfort and allowing early return to normal activity. The approach may also minimize risk of some potential complications.
The results of the SYNTAX Trial have suggested that the risk of stroke with PCI is less than that with CABG, although the two treatment groups received different antiplatelet medical therapy. There has been concern in the past that the durability of PCI may be less than that with CABG, with increased need for later interventions.
Although DESs have not been compared directly with saphenous vein graft (SVG) conduits, current stents may provide durability that is at least as good as SVG conduits. Indeed, the 1-year patency rate of SVG conduits is probably about 85% to 90%, while that for DESs may be slightly better than 90%. Data on follow-up with actual angiography are limited, so this conclusion is inferred from data on the need for reintervention, but would seem to be reasonably accurate.
Finally, new technology and evolving skills of interventional cardiologists have allowed a percutaneous approach to multivessel disease, left main disease, and more-complex coronary lesions.
The clear advantage and most important aspect of CABG is the use of the left internal mammary artery (LIMA) bypass graft to the left anterior descending coronary artery (LAD). The LIMA-to-LAD graft has been shown to be crucial for optimal long-term survival. If patent early, the LIMA graft is probably patent indefinitely, and 10- and 20-year patency rates exceed 90%.
Bypass grafts treat the culprit lesions but also provide prophylaxis against future proximal lesions and protect the entire zone of vulnerable myocardium in diffusely unstable coronary endothelium. The complexity of the coronary lesions is not a factor as it is in PCI because bypass grafts can be placed around any type of proximal lesion.
CABG can be performed off-pump, and LIMA-to-LAD anastomosis lends itself to an off-pump approach because the heart position does not need to be manipulated excessively. Although it is controversial, an off-pump approach to CABG probably does reduce risk of renal insufficiency, pulmonary injury, and bleeding. Many studies have also shown a reduced length of hospital stay with off-pump CABG. Single LIMA-to-LAD grafting performed off-pump does not require any manipulation of the aorta, and thus the risk of stroke is minimized.
Single bypass graft of the LIMA to the LAD can be performed in a minimally invasive manner and off-pump. The approach is called a minimally invasive direct coronary artery bypass (MIDCAB) and involves mobilization of the LIMA with a thoracoscopic or robotic technique and direct anastomosis of the LIMA to the LAD through a minimally invasive, 4- to 5-cm left anterior thoracotomy. Following this procedure, patients can return to work early, the result is cosmetically acceptable, and length of hospital stay is usually short.
A hybrid approach to coronary revascularization would combine the advantages of both CABG and PCI. The hybrid approach involves a MIDCAB, which provides the patient with the benefits of LIMA-to-LAD bypass graft, performed in a minimally invasive manner using thoracoscopic or robotic mobilization of the LIMA and a small left anterior thoracotomy for the LIMA-to-LAD anastomosis.
This procedure is either proceeded by or follows PCI of the non-LAD coronary lesions with DES. The patient avoids the need for sternotomy and cardiopulmonary bypass and has complete revascularization in a minimally invasive manner, maintaining the advantage of the LIMA-to-LAD graft.
The hybrid technique may be either a two-stage approach with the MIDCAB preceding or following PCI by days or weeks or a single-stage procedure in which all steps are performed during a single surgical session. A single-stage approach would require a specialized operating room containing all the fluoroscopic equipment necessary for PCI.
The single-stage approach would have better patient satisfaction and would potentially have a reduced length of hospital stay. Nevertheless, the two-stage approach does have specific advantages. With a two-stage approach, the antiplatelet therapy could be timed to reduce bleeding at MIDCAB and allow adequate antiplatelet therapy dosing for PCI. A functioning LIMA-to-LAD graft would allow subsequent PCI to be performed safely for ostial circumflex lesions, complex left main lesions, and perhaps other lesions. A two-stage approach would eliminate the need for a costly specialized operating room and also would allow the PCI to be performed in a catheterization laboratory with full available functionality.
Patients with multivessel CAD—including LAD disease, a graftable LAD, and non-LAD lesions amenable to PCI—could be considered for a hybrid approach. Candidates could include patients who normally might not be considered for PCI, including those with:
Other patients who might benefit are those who have minimal conduits available for CABG. This approach may also pose reduced risk in patients with:
A hybrid approach would be contraindicated in patients who are not good candidates for MIDCAB, including those with a nongraftable or a deep intramyocardial LAD. Also, patients who have had previous left thoracotomy or left subclavian artery stenosis or who are unable to tolerate single-lung ventilation should not have MIDCAB.
Patients with severe obesity are not good candidates for this approach because of the difficulty identifying the LAD and mobilizing it with a thoracoscopic or robotic approach. A hybrid approach is also contraindicated in patients who are not candidates for PCI, possibly including those with:
A few groups have reported outcomes with a limited number of patients using a hybrid approach. The group from Emory University has reported on a hybrid approach in 106 patients, with no mortalities or strokes. One patient had a perioperative myocardial infarction. All LIMA grafts were patent. All reports are small and nonrandomized but have shown safety and efficacy. Long-term outcomes are unknown.
The hybrid approach to revascularization of CAD is promising. For low-risk patients, it allows the benefit of a minimally invasive approach along with the long-term benefit of the LIMA-to-LAD bypass. Potential early return to work and reduced need for further intervention may contribute to cost-effectiveness in this group over time, but those advantages are speculative.
Select high-risk patients may benefit from a minimally invasive approach. Complex LAD lesions are readily bypassed but may be difficult to treat with PCI. A functioning LIMA-to-LAD graft allows a percutaneous approach to complex left main and ostial circumflex lesions with more safety. DESs in non-LAD lesions are likely at least as durable as SVG, at least in the medium term. A two-stage approach does not require a specialized operating room with fluoroscopic capabilities.
The approach does require collaboration between surgery and cardiology and willingness on the part of surgeons to continue to adapt to less invasive techniques. Although clinical data on outcomes are very limited at this stage, improvements in technology and the changing population with CAD will increasingly make the hybrid approach to treatment the optimal choice for many patients.