Minimally Invasive Heart Surg... Health Article

Definition

Minimally invasive heart surgery refers to surgery performed on the beating heart to provide coronary artery bypass grafting. This technique is often referred to as MIDCAB, minimally invasive direct coronary artery bypass; or OPCAB, off-pump CABG.

Purpose

Minimally invasive heart surgery is performed on the diseased heart to reroute blood around clogged arteries and improve the blood and oxygen supply to the heart. This approach provides patients some benefit in that cardiopulmonary bypass (use of a heart-lung machine) may be avoided, and smaller incisions can be used instead of the standard sternotomy (incision through the sternum, or breast bone) approach. Faster recovery time, decreased procedure costs, and reduced morbidity and mortality are the goals of this technique.

Minimally invasive technique is not new to the field of cardiac surgery. It was performed as early as the 1950s, although the technology associated with stabilizing the cardiac structure during the procedure has become more sophisticated. Also, the anesthesiologist and perfusionist (person monitoring blood flow) have developed better techniques to preserve cardiac function during the procedure to help the surgeon achieve the desired outcome. During the 1990s these new techniques were named: off-pump CABG (OPCAB) and minimally invasive direct coronary artery bypass (MIDCAB). The MIDCAB procedure includes procedures done both with and without cardiopulmonary bypass, the later being referred to as off-pump MIDCAB. Unless otherwise specified, MIDCAB refers to both types of procedures.

Minimally invasive valve surgery has been an outgrowth of the success with minimally invasive coronary artery bypass grafting. Incisions other then the traditional sternotomy allow access to the heart. Minimally invasive valve surgery still requires cardiopulmonary bypass, since this is a true open-heart procedure, (i.e. this is not surgery that is done while the heart is beating). New tools in managing cardioplegic cardiac arrest allow for the smaller incision unobstructed by the required instrumentation. Cannulation of the femoral vessels instead of the larger vessels of the heart also improves visualization.

Demographics

Patients under the age of 70, but not limited by age, with a history of coronary artery disease can be evaluated for this procedure. High risk patients with advanced age, at risk for stroke, or suffering peripheral vascular disease, renal disease, or with poor lung function may benefit from OPCAB and MIDCAB.

Typically disease of the left anterior descending coronary artery is treated with the technique called off-pump
MIDCAB. With sternotomy, disease of the right and left coronary arteries can also be addressed by OPCAB. The significance and location of the coronary artery lesions may limit the success of the MIDCAB or OPCAB procedure. Most practices have at least one surgeon skilled in performing revascularizations without cardiopulmonary bypass. Of all coronary artery bypass grafting procedures, approximately 10–20% are performed in this manner.

Description

The patient receives cardiac monitoring during general anesthesia. Systemic anticoagulation is given to avoid clot formation from foreign surfaces and any periods of artery blockage (occlusion).

MIDCAB

Conversion to a full sternotomy or sternotomy with cardiopulmonary bypass is expected in 1–2% of patients. Redo procedures and reoperation can occur in over 5% of patients, which is still lower than the risk of a second procedure associated with balloon angioplasty and stent placement. Over 90% of all patients are expected to be free of adverse events. Complications most frequently involve rib fracture (over 10% of patients). Mortality associated with MICAB is low and is not seen during the surgical procedure in most instances, but is associated with post-operative complications.

OPCAB

Conversion to cardiopulmonary bypass may be required in patients if anastomosis cannot be completed due to unstable blood pressure, arrhythmia, ischemia, poor anastomosis, or poor surgical access. The same operative mortality is expected when compared to cardiopulmonary bypass patients. The expected decrease in neurological events, renal dysfunction, pulmonary complications, or arrhythmias has not yet been shown to be a consistent benefit, therefore all of these complications can still occur.

Diagnosis/Preparation

An electrocardiogram detects the presence of acute coronary blockage (occlusion). A history of myocardial infarction can also be detected by electrocardiogram. Patients with a history of angina also are evaluated for coronary artery disease. Coronary angiography provides the best diagnostic information about the extent and location of the coronary artery disease.