MINIMALLY INVASIVE DIRECT CABG SURGERY

MINIMALLY INVASIVE DIRECT CABG SURGERY

Minimally invasive direct CABG surgery (MIDCABG surgery) is defined as CABG surgery performed via the minithoracotomy approach (ie, left anterior thoracotomy) without cardiopulmonary bypass.

Advantages of the MIDCABG procedure include:

elimination of cardiopulmonary bypass and its associated adverse effects; avoidance of the median sternotomy incision and aortic manipulation; shorter operating time; and shorter hospital length of stay, with resultant reduction in costs.

Limitations of MIDCABG Surgery include:  limitation of access and exposure; technical difficulty in operating on a beating heart with blood in the field, and the associated learning curve; and limited data on long-term patency when the MIDCABG technique is used.

Two critical elements in MIDCABG surgery are

 (1) harvesting an adequate length of the internal mammary artery of excellent quality

to allow a tension-free anastomosis and

 (2) achieving a technically perfect anastomosis.

OFF-PUMP CABG SURGERY VIA A MEDIAN STERNOTOMY APPROACH

Off-pump CABG and MIDCABG surgery have similar advantages, except that the former

requires a median sternotomy incision.

Advantages of off-pump CABG

·        surgery via the sternotomy approach include the ability to do limited multivessel revascularization and less pain for patients than with minithoracotomy incisions.

·        Rapid recovery

·        Avoidance of cardiopulmonary bypass and associated adverse effects

·        Shorter hospital length of stay

·        Reduced morbidity

·        Faster return to routine activity/faster recovery

·        Lower costs8

·        Shorter duration of operation

·        Less blood loss

·        Shorter duration of ventilator support

·        Avoidance of aortic manipulation

·        Ability to achieve revascularization of multivessel lesions

·        Affords use of internal mammary artery conduits, which appear to be more resistant to atherosclerosis and have superior patency rates over saphenous vein grafts (20 years vs 6-10

·        years)

·        Low operative morbidity and mortality in patients with left ventricular dysfunction, acute myocardial infarction, and cardiogenic shock

·        Preservation of normal septal movement (compared with conventional surgery, which results in paradoxical movement of the interventricular septum)

·        Superior patency results with coronary artery bypass grafting vs angioplasty (>10-year patency of 85%-90% of grafts of left internal mammary artery to left anterior descending

·        artery vs 33%-60% restenosis in angioplasty patients at 6 months) .

·        Elimination of median sternotomy and risk of sternal wound infection, if minithoracotomy approach is used.

Indications

Indications for off-pump CABG surgery include (1) multivessel disease requiring revascularization;

(2) contraindications or increased risk for cardiopulmonary bypass,

such as severe myocardial dysfunction; immunosuppression; history of transient ischemic attacks or cerebrovascular accidents; heavily calcified aortas; aortic disease with increased risk of dissection, rupture, or embolization; impaired renal function or need for dialysis;

and history of previous cardiac surgery; (3) patients who are Jehovah’s Witnesses who refuse transfusions of blood and blood products; and (4) other high-risk patients such as those with advanced age, respiratory problems, or other systemic disease.

Contraindications

·        Small LAD with diameter <1.5 mm

·        Calcified LAD or RCA

·        Intramyocardial LAD

·        Previous use of IMA

·        Median sternotomy contraindicated in patients with history of radiation therapy to the chest wall.

·        Obesity

·        Rightward displacement of the LAD

·        Inadequate IMA

·        Severe pulmonary hypertension with large left ventricle (graft occlusion more likely to occur).

·        Relative contraindication for parasternal incision for anastomosis of right IMA to RCA because of higher degree of technical difficulty and less exposure because the RCA lies deep in the pericardial cavity and is buried in the right atrioventricular groove.

Preoperative consideration

A detailed history and physical examination must be conducted, along with preoperative testing, explanation of the procedure, discussion of the possibility of conversion to conventional CABG surgery if necessary, and surgical risks.

The 2 main indications and risk factors for conversion of off-pump to conventional CABG surgery are hemodynamic instability or compromise during off-pump CABG surgery and inability to access the areas that require revascularization.

Careful preoperative evaluation of candidates for off-pump CABG surgery and a thorough

assessment of patients’ needs, discharge planning, and patients’ education are essential to a successful and rapid recovery and early discharge from the hospital.

Intraoperative Phase

Intraoperative monitoring of patient undergoing off-pump CABG surgery typically includes

a combination of the following:

arterial pressure monitoring,  lead electrocardiographic (ECG) monitoring, transesophageal

echocardiography to detect wall motion abnormalities and optimize preload, and assessment of flow velocity and graft patency.

Anesthesia management includes

use of short-acting agents, aggressive pain control, and single-lung ventilation (of the right lung) to improve access and reduce cardiac movement caused by inflation and deflation of the left lung.

The induction of anesthesia is determined by the patient’s status at the time and the aim to extubate the trachea at the end of the case. Etomidate or propofol are most often used for induction, along with a loading dose of opioid. For most patients a fentanyl dose of 7.5 to 10 mcg/kg (or sufentanil 0.5-1.0 mcg/kg) has been adequate to help blunt the surgical stimulus of incision and sternotomy, yet also allow for timely tracheal extubation. Anesthesia is maintained using a volatile agent, and occasionally, a propofol infusion is also used. Any of the intermediate-acting neuromuscular blockers adequately provide muscle relaxation, while also being readily reversible.

The heparin dose we use for OPCAB is 1.5-2 mg/kg, aiming to keep the activated clotting time (ACT) greater than 300 seconds during vessel anastamoses. Reports of systemic anticoagulation vary considerably in the literature, with heparin doses varying between 1 and 3 mg/kg, and ACTs usually targeted in the 200-300 range.  

Conventional immobilization techniques include use of pharmacological agents, such as β-blockers and calcium channel blockers (to induce bradycardia) and/or adeno sine (to produce temporary cardiac standstill), to help to reduce the technical difficulty of performing surgery on a beating heart.

Postoperative

Day of surgery:

·        Extubation per weaning protocols.

·        Pain management to reduce myocardial oxygen consumption and facilitate activity

·        progression and pulmonary toilet.

·        Electrocardiographic monitoring (leads II, III, aVF if anastomosis of right internal mammary artery to right coronary artery; precordial V leads if anastomosis of left internal mammary artery to left anterior descending artery; lateral leads I, aVL, V5, V6 for circumflex anastomoses; ST-segment depression, tall R waves, and T-wave inversion in anterior leads, especially V1)

Postoperative day 1:

·        Nonsteroidal anti-inflammatory therapy if postpericardiotomy syndrome present

·        Discontinuation of chest tubes if output low

·        Discontinuation of Foley and arterial catheters

·        Electrocardiographic monitoring and pulmonary toilet

·        Continuation of activity progression

·        Transfer to step-down unit or regular unit with telemetry monitoring

Postoperative day 2:

 Continuation of pain management, pulmonary toilet, and activity progression

Discharge to home if stable.