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What is Cardiac Surgery?
Cardiac surgery, or surgery of the heart and tissues surrounding the heart, is done to treat complications of the heart such as ischemic heart disease, also known as coronary artery bypass grafting (CABG), correct congenital heart disease, or treat valvular heart disease from various causes including endocarditis, rheumatic heart disease and atherosclerosis.
Heart surgeries are performed on both children and adults. The most common type for adults is CABG, where a healthy artery or vein from the body is connected, or grafted, to a blocked artery. The grafted artery goes around (byapsses) the blocked portion of the coronary artery. This creates a new path for oxygen-rich blood to flow to the heart muscle. CABG can relieve chest pain and lowers the risk of having a heart attack.
Doctors also use heart surgery to repair or replace heart valves and damaged structures in the heart, implant medical devices to control heartbeat or support heart function and blood flow and also to replace a damaged heart with a healthy heart from a donor.
Traditional heart surgery, often called open-heart surgery, is done by opening the chest wall to operate on the heart. The surgeon cuts through the breastbone to open the chest, which is connected to a bypass machine. The machine takes over the heart’s pumping action and moves blood away from the heart. This allows surgeon to operate on a heart that isn't beating.
Another type of heart surgery is called off-pump, or beating heart, surgery. The heart does not stop beating and a heart-lung bypass machine is not used. Off-pump heart surgery is limited to CABG.
Surgeons can also make small cuts between the ribs to perform other types of heart surgery. The breastbone is not opened to reach the heart, and a machine may or may not be connected to the heart. This is called minimally invasive heart surgery.
Newer methods of heart surgery (such as off-pump and minimally invasive) may reduce risks and speed up recovery time.
Advances in Cardiac Surgery
Recent advances in cardiac surgery have been observed in the areas of valvular disease, coronary artery disease, atrial fibrillation, and congenital heart disease.
New Devices and Techniques used in Cardiac Surgery
Mitral Valve Regurgitation
Severe mitral valve regurgitation can be symptomatic or asymptomatic. It is associated with reduced survival in the absence of adequate treatment. Mitral valve repair generates a favorable outcome as compared to mitral valve replacement in severe degenerative mitral valve regurgitation. However, the effect of mitral valve repair is questionable for functional mitral valve regurgitation. Percutaneous transcatheter procedures are effective to treat functional mitral valve regurgitation. Mitral valve implantation, leaflet procedures, paravalvular leak closure, annuloplasty techniques are examples of percutaneous transcatheter procedures based on the anatomical target.
Mitral Valve Implantation: This is not a routine procedure due to the complications in the mitral valve anatomy, however, many devices are being developed, such as the Lutter prosthesis and the Endovalve-Hermann prosthesis.
Leaflet Procedures: In this procedure leaflets are sutured using advanced technology, such as the MitraClip system. Another form of repairing leaflets is by using the off-pump adjustable chordal implantation approach. Devices that use this approach are currently being developed.
Paravalvular Leak Closure: One of the side-effects of prosthetic valve implantation is paravalvular leakage and this occurs in 5% to 15% of the cases. Paravalvular leak closure or transcatheter mitral leak closure is a useful procedure for atrial septal defects, vascular plugs, and patent ductus arteriosus.
Annular remodeling is recommended for transcatheter procedures. This procedure resizes and fixes leaky valves. There are many devices that are currently being developed to aid in annular remodeling. Direct annuloplasty (Mitralign device, Accucinch system), indirect annuloplasty (CARILLON), energy-mediated annuloplasty (delivery of differing energies to reduce the annular length), and cinching devices (Mardil BACE, Ample PS3 system) are some of the methods of annular remodeling.
Individuals with aortic stenosis suffer a high death rate in the absence of treatment. Recent advances in the treatment of aortic stenosis includes transcatheter aortic valve replacement (TAVR). This procedure is effective for high-risk patients that show poor functioning of the left ventricle, and old age individuals, among others. There are 3 types of TAVR, transaortic, transfemoral, and transapical (Edwards SAPIEN valve) implantation. Paravalvular leakage and aortic regurgitation are some of the drawbacks of the TAVR technique. Aortic valve prosthetics are used to avoid the drawbacks of TAVRs. Some examples of prosthetics that are being developed are the St. Jude Medical® Portico Aortic valve, Direct Flow Medical Aortic valve, among others.
Coronary Artery Disease
This is the leading cause of cardiac arrests and can be treated conventionally with the cardiac artery bypass surgery. However, with the advent of minimally invasive procedures, there are other techniques to deal with the condition.
Percutaneous Coronary Intervention (PCI): This is a technique used to treat patients with refractory myocardial ischemia. Drug-eluting stents (DES) are used in this procedure. However, a large number of postoperative medications are required for this procedure.
Minimally Invasive Direct Coronary Artery Bypass Grafting (MIDCAB): This procedure is the standard of care for most coronary artery diseases, such as left main coronary artery disease and three-vessel coronary artery disease. In this procedure, the left internal thoracic artery is grafted through a left anterolateral thoracotomy onto the left anterior descending coronary artery. Other grafts from the left mammary artery or the saphenous vein onto the left anterior descending coronary artery are performed. Complications are low, the success rate is high, and the mortality is low in this minimally invasive procedure.
Hybrid MIDCAB: This technique combines the left internal mammary artery-left anterior descending coronary artery procedure with either PCI or the transcatheter procedure.
Atrial fibrillation or arrythmia is observed in aging individuals. Some of the techniques used to treat atrial fibrillation include hybrid surgery, percutaneous transcatheter ablation, and surgery.
Hybrid Surgery: This technique combines transcatheter radiofrequency ablation with surgical cryoablation (extreme cold to damage cells or tissue). It is effective in the treatment of AF with a long follow-up. Another procedure that is being investigated for its efficacy is the combination of percutaneous endocardial ablation with thoracoscopic epicardial ablation.
Percutaneous Transcatheter Ablation: This procedure serves to treat the endocardial pulmonary vein and the linear lesions in the left atrium. The level of recurrence of atrial fibrillation is low with this procedure. Individuals also experience a good quality of life following the procedure. Radiofrequency energy or cryothermy are some of the energy sources used for the ablation procedure.
Surgery: The most common surgical procedure is the cut-and-sew Cox-Maze procedure. Currently, cryothermy is used for ablation in the Cox-Maze procedure, creating a minimally invasive procedure. This has resulted in an extended life span for individuals.
Congenital Heart Disease
Structural abnormalities in the heart and associated coronary vessels at birth, results in congenital heart disease. This condition can cause death due to abnormalities or a block to the blood flow.
Double-outlet Right Ventricle with Pulmonary Artery Hypertension: In this condition, the double-outlet right ventricle intracardiac channel surgery is performed along with different procedures, such as the Senning procedure, the Switch procedure, the Rastelli procedure, among others.
Double-patch Procedure to Create Septation in a Single Ventricle: In this case, individuals are born with both the arteries connected to only one ventricle. In order to connect the second ventricle to the arteries, the double-patch procedure is performed.
Devices to Repair Structural Defects: Valves and patches are used to treat structural defects. These devices are made of long-lasting material to prevent reoperation in the individual. The material used for these patches involves the extracellular membrane of organisms, such as the pig, and consists of glycans, and elastin, among others. Porcine SIS-ECM, and CorMatrix are some of the examples of patches.
Ebstein’s Anomaly: This condition involves various defects ranging from the ventricle to the tricuspid valve to the whole heart. The most effective treatment is the anatomical repair of the affected sites as compared to valve replacement.
Robotic Techniques in Cardiac Surgery
Robot-assisted cardiac procedures for closures of atrial septal defects, revascularization in the heart, mitral valve replacement, atrial fibrillation, implantation of lead in the left ventricle, and tumor resection within the heart, are now being performed. The da-Vinci™ surgical system is a US food and drug administered- approved robotic procedure for cardiac surgeries. Some of the advantages of this procedure are tremor-free operations and improved dexterity.
Cardiac Cell Therapy for Heart Diseases
Cardiac myoplasty is a process of cardiac myocyte regeneration or replacement. This therapy is utilized to treat myocardial infarction that leads to heart failure. Stem cells are utilized for this therapy and currently, the most common source of stem cells is the bone marrow. Other sources of stem cells include the amniotic sac, the embryonic stem cells, and the umbilical cord stem cells. However, this form of therapy is only used in conjunction with a bypass surgery or with a percutaneous coronary intervention since it does not generate large vessels in the heart, but smaller capillaries.
Mechanical Assist Devices for Patients Waiting for Heart Transplant
These are artificial devices that control the function of the heart. One example of a mechanical device is the left ventricular assist device (LVAD). Small mechanical pumps were being widely used to assist individuals who were waiting for a suitable donor. However, currently there are approved continuous flow LVADs that can maintain a patient for a year. Efforts are being undertaken to develop such devices for individuals who are ineligible for a transplant.
Left Ventricular Remodeling
This procedure is performed to restore the shape of the heart following a cardiac arrest. During a cardiac arrest, the heart develops scar tissue due to damage. The left ventricle is damaged in the process and hence, by remodeling the left ventricle, the heart shape is restored and the blood is pumped efficiently.