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Minimally Invasive Direct Coronary Artery Bypass

Marco Zenati, MD
VA Boston Healthcare System

Abstract

Minimally invasive direct coronary artery bypass (MIDCAB) utilizes a small (4-5 cm) left anterior thoracotomy incision for direct visualization of the diseased coronary artery on the anterior wall of the left ventricle without the use of cardiopulmonary bypass (CPB). Since its first description in 1967 by Kolesov, many variations have been described including single left internal mammary artery (LIMA) to left anterior descending (LAD) coronary bypass, multivessel (including complete) revascularization, robotics and video-based endoscopic techniques for IMA harvest and revascularization. Finally, hybrid approaches for revascularization (ie, surgical bypass of the LAD coronary artery followed by percutaneous coronary intervention (PCI) of non-LAD targets) utilize the same approach for complex patients needing coronary revascularization.

In this article, we will describe the basics of the MIDCAB surgery, emphasising both the left anterior thoracotomy for the harvest of LIMA and direct anastomosis on a beating heart without CPB. This procedure is done on a 72-year-old patient who had significant long LAD stenosis and presented with effort angina. Following a multidisciplinary “heart team” conference, he underwent a successful MIDCAB and was discharged home on postoperative day 4.

Case Overview

Background

Ischemic heart disease (IHD) is a major cause of death and disability in developed countries. Although there is persistent decline in mortality rates from coronary artery disease worldwide over the past four decades, IHD is accountable for about one-third or more of all deaths in individuals over age 35. It has been estimated that nearly one-half of all middle-aged men and one-third of middle-aged women in the United States will develop some manifestation of IHD.

Coronary artery bypass grafting (CABG) is among the most important surgical procedures in the history of medicine. Since its initial development more than a century ago by Alexis Carrel, which resulted in his Nobel prize in physiology in 1912, several modifications of this important surgery were done. Notably, in the era of minimally invasive surgery where more and more innovations are being developed, the establishment of minimally invasive direct coronary artery revascularization deserves special attention.

Focused History of the Patient

We present an active 72-year-old male in overall good condition who had no significant comorbidities. Four months prior to his presentation to our team, he experienced chest discomfort and palpitation during exercise at the gym where he used to train 3-4 times a week.

Physical Exam

Following presentation to his Primary care, he was sent for exercise tolerance test. Following the test, he again experienced chest pain and discomfort. Physical examination was not contributory at that time.

Electrocardiogram showed frequent premature ventricular contractions and he was referred to exercise tolerance test. Stress test demonstrated ST segment depressions in the inferior electrocardiographic leads including V4-V6, and 2 mm ST elevations in aVR and aVL. Nuclear imaging at that time demonstrated large, moderate to severe reversible defects involving the anterior, septal, and apical walls. Following the test, he was sent to the emergency department to rule out acute myocardial infarction. Left cardiac catheterization demonstrated a right-dominant coronary arterial system with 1-vessel coronary artery disease (left main- patent, left anterior descending showed diffuse long segment of 95% stenosis in the proximal part and 80% diffuse disease with TIMI 2 flow in the mid LAD territory). Circumflex and right coronary artery had normal fluoroscopic morphology with non-significant stenosis. Echocardiography showed preserved ejection fraction (70%) with no diastolic dysfunction and no valvular disease. The patient presented in a multidisciplinary “heart team” discussion and expert consensus elected to offer the patient MIDCAB LIMA-LAD revascularization.

Natural History

Left untreated high grade stenosis in the proximal coronary artery may progress and cause complete obstruction leading to devastating ischemic heart disease sequelae.

Options for Treatment

The gold standard for complete coronary revascularization is coronary artery bypass grafting, especially the use of arterial bypass with left internal mammary artery (LIMA) to left anterior descending artery (LAD). This has been proved in multiple meta-analyses to relieve symptoms, improve survival, and decrease the need for further revascularization besides decrease recurrence of adverse cardiac events.1,2 The alternative in patients who need revascularization is PCI.

The use of cardioplegia with CPB has resulted in superior clinical results by allowing the surgeon to work in arrested heart, thus maximizing exposure that permits precise complex revascularization. The downside of using cardioplegia is the need for aortic instrumentation (ie, cannulation and decannulation), initiation and termination of CPB with circulatory arrest, and hypothermia and anticoagulation that prepare the patient for intense inflammatory mediated response and hemodynamic changes.

On one hand, the use of median sternotomy for exposure yields excellent visualization of the mediastinum and the heart, but on the other hand, it exposes the patient to pain and infection risks that can be devastating.

As the alternative of coronary artery bypass surgery, PCI is limited in multiple occlusion sites and has high reintervention rates due to in-stent restenosis, especially in diabetic subjects.

In 1967, Kolessov first described the procedure of grafting the left anterior descending artery using LIMA on a beating heart through left anterior thoracotomy.3 This was the first description of the procedure as it is used today, though many years elapsed until it was known and accepted among cardiac surgeons.4 Alternative approaches for more complete revascularization can utilize this limited thoracotomy incision for the use of a free segment of right IMA, radial artery, saphenous vein, or inferior epigastric artery Y’d or T’d to accessible coronary arteries (diagonal or circumflex branches).5

Rationale for Treatment

Patient selection is of great importance in MIDCAB surgery. The patient should be selected carefully with the ideal candidate having severe stenosis in the anterior coronary vessels - mainly the proximal portion of the left anterior descending artery with the distal vessel relatively free from diffuse disease and calcification.6,7 Other patients that should undergo MIDCAB surgery are those with multivessel disease in whom complete surgical revascularization is contraindicated (given structural aortic disease that prohibit cannulation or anastomosis), sternotomy is contraindicated (given prior surgery or mediastinal condition, such as s/p sternal wound infection, mediastinitis, or mediastinal radiation), or cardiopulmonary bypass is contraindicated (given multiple comorbidities or high risk conditions such as calcified ascending aorta or diffuse atherosclerosis).8 MIDCAB surgery is also a good choice when PCI cannot be performed due to a contrast allergy or technical difficulties such as excessive stenotic length, angulation, tortuosity, complex lesions, total vessel occlusion, and diabetes.9 Compared to Sternotomy with CPB, MIDCAB patients experience less postoperative pain, have shorter convalescence periods, need fewer blood transfusions, and exhibit less atrial fibrillation.10,11

However, MIDCAB is a technical demanding procedure given the limited exposure and the beating heart. Specific disadvantages include: the exposure of the anterior coronary vessels as the revascularization of other vessels, such as the posterior descending artery and right coronary artery, require the manipulation of the heart; the difficulty of complete revascularization (residual CAD should be treated with PC or hybrid approach with PCI added to the other occluded vessels should be considered); the technical challenges of LIMA/RIMA skeletonized harvesting; the possibility that intramyocardial vessels (< 1.5mm) and a diffuse, calcified target require complex and extensive endarterectomy; the need for single-lung ventilation; the use of a double-lumen endotracheal tube or bronchial-blocker with bronchoscopy to confirm correct placement; and the need to treat for postoperative thoracotomy pain with epidural, intercostal nerve cryoablation, etc. If possible, myocardial stabilization devices (e.g. Octopus device) should be used to improve the accuracy and ease of distal anastomosis on a beating heart.

Special Considerations

There are few contraindications regarding this procedure. For obese patients, LIMA harvest is feasible, but the lateral pressure exerted on the wound with the retractor might cause necrosis and prompt infection in the edges of the wound. Similarly, females with large breast tissue also have increased risk for wound necrosis and infection (relative). Prior thoracotomy and extensive chest adhesions are relative contraindications as they limit the exposure and thus decrease the benefit of a minimally invasive approach. Contraindications also include intramyocardial (relative), calcified small size (< 1.5mm) lesions in the LAD in the preoperative CT coronography or angiography. Left subclavian artery stenosis or occlusion limits the use of LIMA. Certain moribund patients should not undergo this procedure, specifically those in whom cardiogenic shock or ischemia is too severe to permit snaring of the vessels or who cannot tolerate single lung ventilation (eg severe COPD with emphysema) or the decrease in heart rate / blood pressure that is induced by anesthesia to assist the surgeon for the endarterectomy and anastomosis.12

Discussion

CAD remains the leading cause of death in North America. Besides primary prevention, optimal medical therapy and percutaneous or surgical revascularization showed to improve survival and quality of life.13,14 The use of LIMA as a graft showed substantial survival advantage in CABG when anastomosed to the LAD. Studies showed 10 year graft patency rates that exceed 95%.15,16

In most institutes, patients who need CPB and median sternotomy must undergo 24 hour monitoring in an intensive care unit followed by a median hospital stay of 6-7 days.17 The alternative for CABG in less complicated cases or limited coronary vascular disease is PCI, which has the benefit of a same-day discharge procedure, minimal postprocedural observation with good outcomes due to angiography based stenting. However, despite the reduced invasiveness of PCI, the major disadvantage is the need for repeated revascularization despite a newer generation of drug-eluting stents (i.e, DES). Hybrid approaches that combine the benefits of PCI and CABG are recognized as feasible alternatives in well selected patients.

Several recent studies compare the gold standard of revascularization, CABG with CPB via full sternotomy, and MID CABG or hybrid procedures (MIDCAB+PCI). All these studies demonstrate equal survival and long term outcome of minimally invasive procedures compared to full sternotomy. In the case of hybrid approaches, more revascularization was used as expected.17,18,19,20,21 An additional benefit of MIDCAB or hybrid minimally invasive approaches is the use of off-pump techniques instead of on-pump coronary artery revascularization. In 2015, two separate meta-analyses arrived at the same conclusion that off-pump surgery can significantly reduce the risk for stroke rates specifically in high risk patients.22,23 Additional studies showed that patients with LIMA-to-LAD grafting return to normal daily function quickly and get discharged from hospital on postoperative day 4.24,25 Graft patency after single vessel small thoracotomy showed 100% patency in 6 months in two separate studies as well.26,27

Patient selection is prudent for this highly demanding procedure. Three factors should be considered when choosing the right revascularization procedure to the right patients: 1) angiographic factors, 2) patient related factors, and 3) clinical factors.

High grade single vessel long stenosis and other vessel anatomic limiting factors for PCI such as tortuosity, angulation, etc, make MIDCAB a good alternative to PCI. Multivessel disease should be treated surgically unless the patient cannot tolerate CPB due to an anatomic aortic condition or his/her status as described earlier in the special considerations section. Prior sternotomy, severe mediastinal infection, or radiation therapy gives this approach an advantage in the appropriate patient. Finally, the need for single lung ventilation, severe cardiogenic shock, and poor myocardial perfusion (which limits the relative ischemic time while snaring the myocardium) limits the use of this technique. We recommend using the fifth ICS rather than the fourth to allow better utilization of the LIMA harvest as well as better mid-LAD exposure.

In conclusion, beating heart coronary artery bypass grafting is a technically challenging procedure. Adding the limited exposure via left anterior thoracotomy makes the procedure even more challenging. Advancements in technology, such as MIDCAB retractors for LIMA harvest and heart stabilizers, make the procedure feasible. Comprehensive understanding of the LAD anatomy is vital for successful performance of the anastomosis. As always, patient selection should be optimal, and the surgeon should feel competent enough to perform this kind of operation.

Equipment

No special equipment was used.

Disclosures

The authors have no relevant disclosures.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.

Citations

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