Beating Heart Cabg

Beating Heart CABG

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Dr. Saeed Akhtar	Article Submitted by Dr. Saeed Akhtar, MS, MCh (Thoracic & Cardiovascular Surgery)
	E-mail -	drsaeedakhtar@gmail.com
	Post Method -	via E-mail
	Post Date -	20^th, November, 06
	Submission Category -	Doctor's Article

Introduction

Prior to the introduction of Cardiopulmonary bypass (CPB), CABG operations were performed on beating heart. The advent of cardiopulmonary bypass in the latter half of the last century enabled cardiac surgeons to perform a wide range of operations that had previously been impossible. Extracorporeal circulation, however, elicits a series of physiologic derangements causing multiple complications. Theoretically, by eliminating the use of cardiopulmonary bypass, many of the adverse systemic sequelae associated with extracorporeal circulation may be lessened.

Buffolo and Benetti in 1985 showed that beating heart CABG could be performed with similar results as compared to that of On-pump CABG in large number of patients. Today, advances in technology have enabled a near bloodless and near motionless target area to perform an anastomosis on beating heart.

Hazards Of Cardiopulmonary Bypass (CPB):

CPB itself has the potential to cause multiple complications. These complications are:

Neurological complications.
Immunosuppression.
Systemic inflammatory response:

Bleeding complications
Renal insufficiency
Pulmonary insufficiency

Perioperative myocardial infarction.
Delayed recovery.

Advantages of Beating Heart CABG:

Patients undergoing beating heart CABG have benefits in following ways:

Shorter hospital stay.
Shorter ventilatory support.
Less blood transfusion.
Reduced systemic inflammatory response.
Reduced neurological complications.
Less cost.

Preoperative Planning:

Beating heart CABG requires preoperative plan for the revascularization procedure which is different from CABG with CPB. There is global ischemia in CABG with CPB due to aortic cross-clamping and cardioplegic arrest and it is managed by decreasing myocardial oxygen demand. In beating heart CABG, there is regional ischemia which is managed by minimizing the area of ischemia. This preoperative planning includes:

Review of angiogram to assess targets and plan of grafting.
Minimize regional ischemia:

Establish distal flow as soon as possible:

Perform LIMA graft first.
Perform proximal anastomosis first.
Use multivessel cannula to perfuse the grafts.

Perform LIMA graft first.

Perform LIMA graft first.
Perform proximal anastomosis first.
Use multivessel cannula to perfuse the grafts.

Intraoperative Fundamentals For Beating Heart CABG:

In girls, it extends from 11-13 years and in boys from 12-14 years of age. It starts with the onset of puberty and the adolescent becomes more concerned with developing body.

Anesthesia:

The anesthesiologist is integral to the success of beating heart CABG. They have to maintain stable hemodynamics in a rapidly changing environment due to regional ischemia and cardiac manipulation.

Heparinization:

Most centers to give a dose of 1.5mg/kg. BW. Heparin reversal protocols also vary from partial to full doses of protamine.

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Normothermia:

Maintenance of body temperature is very important. This is achieved by:

Warm IV and irrigation fluids.
Heating mattress.
Humidified airway.
Warm OR.

Ischemia Management:

The management of myocardial ischemia requires following considerations:

Decreasing myocardial oxygen consumption by reducing heart rate.
Increasing myocardial blood supply by:

Nitrates.
Maintaining adequate mean arterial pressure (MAP.
Intracoronary shunts (Fig.1).

Intracoronary shunts

Monitoring:

Monitoring is critical during beating heart CABG. Displacement and manipulation of the heart poses unique challenges. Following monitoring techniques are used during surgery:

Pulmonary artery catheter.
EKG.
TEE (Transesophageal Echocardiography).
Direct visual observation of the heart.

Hemodynamic Stability:

Maintaining hemodynamic stability during beating heart CABG is critical. This is achieved by various methods which can be mechanical or pharmacological.

Mechanical interventions:
Trendelenburg position (Fig.2).
Table rotation (Fig.3).
Cardiac manipulation.
Intra-aortic balloon pump (IABP).

Pacing wires.
Pharmacological interventions:
Low-dose norepinephrine infusion.
Dopamoine/dobutamine.
Nitroglycerine infusion.
Alpha agents

Cardiac Manipulation:

Manipulation of a beating heart requires patience and slow, gentle maneuvers. The success of performing the anastomosis is directly related to good exposure and stabilization.

Coronary Artery Exposure:

Exposure of different coronary arteries is achieved by:

Changing the position of operation table.
Opening the pleural cavity.
Using deep pericardial retraction sutures.

Stabilization Of Target Vessels:

Stabilization of target area is important for performing a precise anastomosis on beating heart and this is achieved by using Coronary Stabilizers. There are two types of coronary stabilizers available:

Suction type (Fig.4)
Compression type.

Suction technology provides secure attachment of the stabilizers to the epicardium (e.g. Octopus Device-Figs.5, 6, &7). They are more commonly used now as they isolate and immobilize the target area in a better way than compression stabilizers.

Coronary Occlusion:

In beating heart CABG, proximal occlusion of the target coronary artery is required to stop blood flow for better visibility. This is done by passing a pledgeted Silastic suture around the coronary artery.

Coronary Occlusion:

Bloodless Field:

The anastomosis site must be cleared of blood to allow visualization for accurate suturing. This is done by using Blower/Mister System which blows CO2 jet at the site of anastomosis.

Postoperative Management:

Extubation:

In beating heart CABG, extubation may occur early when the patient is normothermic, stable and bleeding has reduced.

Pain Control:

Pain control methods include both systemic analgesics and regional analgesia by epidural catheter.

General Patient Condition:

Beating heart CABG results in shorter length of ICU stay and overall hospital stay. It also allows the patient to return to normal activities much earlier than patients on CPB.

Conclusion

The treatment of ischemic heart disease in the modern era has been revolutionized with the advent of CABG. Reduction of CPB-related morbidity through the use of beating heart CABG:

Allows some higher- risk patients to safely undergo CABG.
Makes CABG an attractive modality to lowest- risk patients.
Allows faster recovery for all patients.
Costs less to the patients.

References:

Buffalo E, Andrade NCS, Succi JE, et al. Direct myocardial revascularization without extracorporeal circulation: technique and initial results. Tex Heart Inst J. 1985; 12:33-41.
Benetti FJ, Naselli G, Wood M, Geffner L. Direct myocardial revascularization without extracorporeal circulation: Experience in 700 patients. Chest. 1991; 100:312-316.
Puskas JD, Wright CE, Ronson RS, et al. Off-pump multivessel coronary bypass via sternotomy is safe and effective. Ann Thorac Surg.1998; 66:1068-1072.
Calafiore AM, Teodori G, Giammarco GD, et al. Multiple arterial conduits without cardiopulmonary bypass: early angiographic results. Ann Thorac Surg. 1999; 67:450-456.
Arom KV, Flavin TF, Emery RW, Kshettry VR, Janey PA, Petersen RJ. Safety and efficacy of off-pump coronary artery bypass grafting. Ann Thorac Surg. 2000; 69:704-710.