Minimally invasive cardiac surgery is becoming popular nowadays. The term is ambiguous and there have been many ideas since its inception with gradual evolutionary modifications. There is no standard for a particular procedure and an attitudinal intent of the surgeon is necessary. Certainly, the procedure is time-consuming, difficult, and possible only in selected cases. The surgeons are still not in a situation where mortality is accepted in a way it is accepted in the standard methods. Specially designed retractors and instruments help to a great extent. In a particular case and a specific design of a particular instrument is necessary, the type of operation alongside the nature of tissues that have to be dealt with is needed. Thoracoscopy, which has become very popular recently, in most cases does not require gas, and most of the time long-handled laparoscopic instruments are used. Adaptation of these instruments was done in most cases. One should remember that in true minimal access, the basic procedure is the same, but even though the access is small, lesser pain and other advantages are there, the access is different for different processes. Standardization is difficult and still, such procedures are operator-dependent and not done everywhere.
Traditionally minimally invasive cardiac surgery refers to a situation where almost all the gamut of cardiopulmonary bypass is employed and either a repair or replacement of a valve or defects or revascularization is done through limited access. The recent interest is in sparing the sternum, as this is not only cosmetic but also adds certain recovery benefits. The pain is less and the tendency of the scar to form an unsightly keloid is not there.
In traditional surgery, the whole heart is in front of the surgical team and this is a huge psychological feeling of safety for emergencies that may happen. This safe feeling is absent in limited access surgery as there is only partial exposure or only the operating target is exposed. The misery of sternotomy and that of uncompromised access is more than the actual surgery itself. This is still a belief in cardiac surgery. Limiting access may, in a way, lessen this misery. So far this form of cardiac surgery is available to adults in a limited number of situations where cosmesis is an issue, and where age or comorbidities contradict the stress of unwarranted large access. Complex congenitals require adequate access for repairs and hence minimal invasive surgery should not be attempted.
Conventionally cardiac surgery is a major procedure needing a big incision for access and involves major stress. Since the very early days, researchers and operators have been troubled by the burden of trauma and stress. A sincere attempt was made to reduce this and the best way was finding out a solution to modify the approach. The physicians always had it at the back of their minds that the heart was compromised. The belief that the trauma of access was more than the trauma of the actual procedure, made the surgeons think about whether the same operation could be done with limited access. Of course, this involved a sacrifice of the feeling of safety, limited access, increased time, and redesigned sophisticated instruments. Minimally invasive cardiac surgery was the outcome.
Cosgrove and Sabik first described a limited-access mini-sternotomy for the replacement of an aortic valve. Soon elderly subjects with comorbidities were increasingly offered limited sternotomy.
Intraoperative TEE and its improvements had a major role in the visualization of the rest of the heart. Action is taken if anything untoward happens.
There was a period when only limited sternotomy for cardiac surgery was practiced. Femoro-femoral cannulation was relearned and modifications were made to suit the procedure. A balloon-tipped aortic cannula came to the market and helped with cross-clamping and cardioplegia delivery in addition to systemic perfusion. However, the surgeon was ready to devote the increased time required for direct femoral cannulation, the availability, the prohibitive price, and, more importantly, the increased incidence of endothelial damage did not make such a catheter popular. TEE also helped in the correct placement of cannulas and localizing injuries if they happened. Femoral cannulation also helped in removing the clutter of multiple tubes and other ancillary instruments away from the actual operating field. The initial attitude was operating with the existing instruments and appliances till a gradual realization occurred that limited access, for better operative performance and ease, required long-handled modified instruments and there is a long learning curve. The transition was difficult, but still, the effort was worth it.
At the start modified partial sternotomy was attempted in various forms. Even a para-sternal approach with resection of costochondral cartilages with the sacrifice of internal mammary arteries was done in a few cases. The approach was different for different situations – thus for procedures on the aortic valve, a superior approach was preferred. The mitral valve or ASDs were best accessible by a lower partial thoracotomy or the many forms of mini-sternotomy with a limited skin incision. Sternal-sparing mini-thoracotomies had been added later. Certain concepts about sternotomy need to be cleared and the following is an account of the same:
Median sternotomy: an incision down the midline of the entire sternum Hemi-sternotomy: an incision in the midline of half the sternum on the upper or lower part.
Clamshell sternotomy (bilateral thoraco-sternotomy): a partial sternotomy with a horizontal incision on both sides of the sternum in the fifth or sixth intercostal space (space between the ribs) with the ribs retracted for a wider view.
Hemi-clamshell sternotomy (thoraco-sternotomy): a partial sternotomy with a horizontal incision on either side of the sternum in the fifth or sixth intercostal space for anterior thoracotomies.
Modified thoraco-sternotomy: a clamshell sternotomy with a modified sternal incision closure technique of the sternum with crossed wires.
The following are schematic pictures of partial sternotomy in the various forms they are practiced in different conditions:
Whether the lower aspect of an upper hemi-sternotomy or the upper aspect of a lower partial sternotomy is going to end like an arrowhead or T, was the surgeon's choice. J-shaped extension was preferred by many.
In the first few cardiac surgery cases, till the superiority of midline sternotomy was established, anterior thoracotomies on either side joined by a transverse sternotomy were done. This involved sacrifice of internal mammaries on both sides and this was appreciated as a defect at that time. Midline sternotomy became the gold standard for cardiac exposure soon and still is in favor. As midline sternotomy is related directly to invasiveness, minimizing the approach became the subject of interest. The surgeons were capable of taking on the burden of the associated difficulties, and operations by the partial sternotomies in carefully selected cases began.
We joined this bandwagon in the late ‘90s and did ASDs, mitral valve replacements, and aortic valve replacements by partial sternotomies. We were having a spate of infections at that time, and maintaining the sterno-costo-vertebral stability by preserving a portion of the sternum along with the ribs and the vertebrae was important. Sternal closure was a bit tricky. We found that preserving the manubrium in a lower partial sternotomy or the body of the sternum in a manubriotomy with a limited extension into the body of the sternum had good results. The other advantages included less pain, less intense infections, a stable chest, cosmetic smaller incisions, less drainage with lower blood and blood-product administration, and a shorter hospital stay. The stress of the surgery was also less. A limited sternotomy approach was seen as appropriate in patients with dominant comorbidities. Careful selection was required and it was observed that the rate and frequency of conversion to a conventional full sternotomy were always lower in hypo-sthenic individuals. The introduction of adhesive defibrillator paddles solved the problem of the direct application of large metallic paddles to the heart.
Soon aortic valve and related procedures became a routine with the upper partial sternotomy approach and skillful surgeons even added Bentall procedure in selected cases.
We had our own experiences and found that it was possible to do selected cases with the usual clutter of tubings in the operative field and the usual instruments used for conventional heart surgery. The following photographs are a testimony of what we achieved at the Department of Cardiothoracic & Vascular Surgery at SSKM Hospitals and IPGME&R, Kolkata.
Surgeons doing MICS.
A Mitral Valve replacement.
How it looks like.
A post-operative photo with submammary incision and groin cannulation.
A photo of operative aortic exposure.
The introduction of sternal-sparing mini-thoracotomies was gradual. Mostly ASDs and mitral valve procedures were done. Some skillful surgeons introduced lateral 2nd or 3rd intercostal space mini-thoracotomies for approaching the aortic valve. Axillary thoracotomy was another route having the advantage of cosmesis, however, the prospect of using long-handled instruments and a perception that the target is distant, has not made this approach popular even among those practicing MICS. The present-day students are trained in endoscopic surgery so it is easier for them to handle the instruments designed for such approaches, tie distant secure knots, and take a suture where needed.
Multivessel revascularization was a challenge and the widely advertised McGinn technique helped in its spread. Specially designed stabilizers and certain improvised methods also helped in making CABG a reality in selected cases.
A few words about robotic CABG need to be mentioned. Almost all who venture with the available robotic systems praise the procedural ease and the availability of a three-dimensional magnification. However, the fact that the surgeon is away at a place where the console is, the need for several trained personnel to introduce the specially designed arms through the ports created, specially designed operating rooms, and the prohibitive cost, are all factors against a mass use in the general population.
The advent of tissue stabilizers protected the retracted soft tissue and there was some incorporation of the port-access techniques. VATs and robotic methods are still new, practiced by a handful, and have not yet found an answer to certain problems.
Recently catheter-based TAVI, EVAR, and TAVER procedures have become the talk of the day. TAVI is transcatheter valve implantation where a crimped and folded bio-prosthetic valve is introduced, housed in a catheter sheath, positioned, and implanted at a diseased, disorganized, and primarily stenosed native valve. EVAR and TAVER refer to endoscopic obliteration of aneurysms. A hybrid approach is necessary for exposure of the arteries through which the catheter sheath containing the walled stent is to be introduced. In TAVI for the aortic Valve also Guiradon proposed trans-aortic and trans-apical surgical introduction methods. These methods cut down the time required drastically. The indications are gradually encompassing cases hitherto considered a contraindication and, though a matter of concern to the cardiothoracic surgeon, becoming popular.
MICS offers several advantages and is endearing to the patient because people tend to think less invasion means less pain. The cosmetic nature of the scar and a faster recovery greatly add to this fact. The surgeon also is intrigued by the challenge and wants to rise to the occasion.