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ЗАДАТЬ ВОПРОС РЕДАКТОРУ РАЗДЕЛА (ответ в течение нескольких дней)
18 февраля 2002 00:00 | Lawrence H. Cohn, MD
Minimally Invasive Valve Surgery
CTSNet Grand Rounds on the Web April 20, 1999 Brigham and Women's Hospital Boston, Massachussetts
Resident Case Presentation
Hello, I’m Doctor Lishan Aklog, chief resident in cardiac surgery under Dr. Lawrence Cohn at Brigham and Women’s Hospital in Boston. I’ll be presenting a case of severe myxomatous mitral regurgitation which is repaired using a minimally invasive parasternal approach.
The patient is a 47 year-old software engineer. He has had a long history of mitral valve prolapse which has been asymptomatic and followed by serial echocardiograms. His last echocardiogram was 8 months ago in April. It showed severe mitral regurgitation with myxomatous change and prolapse of both the anterior and posterior leaflets. The left atrium was markedly enlarged, measuring 64 millimeters Early signs of left ventricular overload were noted, including moderate dilatation with an end systolic dimension of 58 millimeters and mildly decreased global systolic function with an ejection fraction of 45−50 percent.
The patient now reports worsening symptoms of congestive heart failure including fatigue, dyspnea on exertion after two flights and paroxysmal nocturnal dyspnea. He denied chest pain, palpatations or syncope. His only significant past medical history is congenital heart block for which a VVI pacemaker was placed in 1991. His only medication is omeprazole. On physical examination he was noted to have fine bibasilar rales and a III/VI holosystolic murmur best heard at the apex and radiating to the left axilla, consistent with mitral regurgitation.
Preoperative evaluation included a cardiac catheterization. We perform routine cardiac cathaterization on all patients over 40 years of age to rule out any unsuspected coronary artery disease. The patient, in fact, had normal coronary arteries. His right heart catheterization was consistent with chronic mitral regurgitation, including mild pulmonary hypertension with a pulmonary artery pressure of 46/26, and a moderately elevated pulmonary wedge pressure of 25 with significant v waves to 41. His electrocardiogram was 100% ventricularly paced and the remainder of his preoperative studies were normal.
The patient was taken to the operating room for repair of his mitral valve. After induction of general anesthesia and prior to making an incision, a complete transesophageal echocardiogram was performed to delineate his anatomy. The findings were similar to his last echocardiogram eight months ago. As you can see in this echo, severe mitral regurgitation with reversal of flow in the pulmonary veins is readily apparent. Both anterior and posterior leaflets appear myxomatous and prolapse above the plane of the annulus. However, no ruptured chordae were identified. In addition, the left ventricle again showed signs of hypertrophy and dilatation with mildly decreased global systolic function. The aortic root was mildly dilated at 37 millimeters.
The patient’s body habitus and chest x-ray were then carefully reviewed, and it was felt that the patient would be a good candidate for this approach. The chest x-rays are very important in determining the placement of the incision relative to the intercostal spaces. In this patient, the ascending aorta and right atrium appear slightly more cephalad than usual. A small vertical incision was made along the right edge of the sternum from the bottom of the second rib to the top of the fourth rib. The pectoralis muscle was then mobilized for a good distance off of the chest wall, almost as a formal flap. It was extended cephalad, caudad and lateral, exposing the third costal cartilage. An approximately 1.5cm piece of cartilage was removed at the stern0costal junction. The pleural space is usually entered, although, occasionally the mediastinal pleura can be peeled off the pericardium without having to enter the plural space.
A small incision was made in the pericardial well, well anterior to the phrenic nerve, and the position of the right atrial appendage and aortic root was palpated. It was felt that the exposure in this patient would be best obtained by resecting a portion of the second cartilage and extending the incision cephalad. The total length of the incision was six centimeters. The right internal mammary artery was then doubly ligated at the first and third intercostal space, and the intercostal muscles were incised for a good distance laterally. This allowed the detached ribs, in this case the second and third ribs, to be easily retracted laterally like an open book, while minimizing the amount of resected cartilage. The pericardium was then widely opened and the edges were pulled up firmly and secured to the dermis.
Over the past six months we have been avoiding a groin incision by cannulating the ascending aorta directly using a specially wire-guided cannula and a long percutaneous femoral venous catheter. This patient, however, had an enlarged aortic root that was not well positioned for direct cannulation. We therefore proceeded to expose the right femoral vessels with a small transverse incision above the groin crease. The femoral artery was cannulated with a short 20 Fr cannula, the femoral vein was cannulated through a purse-string at the saphenofemoral junction using a long 25 Fr Biomedicus cannula. Partial cardiopulmonary bypass was initiated before canuulating in the superior vena cava with a 24 Fr right angle cannula. Vacuum assisted venous drainage was utilized.
Once on full bypass, the patient was cooled to 28 degrees. The ascending aorta was cross-clamped and cold blood cardioplegia was administered through the aortic root and repeated every 20 to 30 minutes. In most cases, the mitral valve has been approached through the right atrium and the atrial septum, the so-calledtrans-septal approach. However, in this patient, the left atrium was large enough that the valve could be approached directly through Sondergards’ groove. Exposing the mitral valve at this point requires some patience and a gradual stepwise approach. The anterior edge of the atriotomy and the atrial septum is retracted anteriorly. Retraction sutures are also placed in the annulus and the trigone to improve exposure of the mitral valve.
The mitral valve is then carefully inspected and analyzed to determine the specific anatomic deficiency and plan the repair. Both leaflets were myxomatous; they were quite floppy and redundant, with significant prolapse above the plane of the annulus. The height of the posterior leaflet was well over three centimeters. No ruptured chordae were identified and the annulus itself was moderately dilated, but with loss of its naturally elliptical shape and into a more circular configuration.
Mitral valve repair was then performed. A large quadrangular resection of the middle scallop of the posterior leaflet (P-2) was performed. The width of the resected leaflet was nearly 50 percent of the circumference of the annulus. The leaflet edges were then advanced along the annulus over a long distance using a running 4−0 Prolene suture. The height of the posterior leaflet was further decreased by rolling part of the cut edge of the leaflet down onto the anulus. The remaining leaflet edges were re-approximated using a double running 4−0 Prolene suture. The posterior leaflet now had a height of approximately 1 centimeter.
The valve repair was tested by forcefully infusing saline into the left ventricle. The valve leaflets opposed much better now, but there was still a residual amount of regurgitation primarily at the anterolateral commissure. This was due to redundancy and prolapse of this scallop of the anterior leaflet (A1). A commisuroplasty suture was placed using a running 4−0 Prolene suture. This suture incorporated redundant anterior leaflet tissue and limited its ability to prolapse. Repeat testing revealed only minimal residual regurgitation. A 30 millimeter Cosgrove-Edwards annuloplasty band was then inserted using wide 2−0 Ethibond horizontal mattress sutures in the annulus. The size was determined in the usual fashion, by the height of the anterior leaflet and the intertrigonal distance.
The atriotomy was then closed and a single ventricular wire was placed. This is always done before removing the cross clamp because it can be very difficult to do through this incision with the ventricle full. With the patient in Trendelenburg position, the heart was de-aired through the cardioplegia site in the aortic root as well as through the left atriotomy. The patient was weaned off bypass without difficulty, ventricularly paced but on no inotropes. Two right angle chest tubes were placed and the incision was closed, reapproximating the mobilized pectoralis muscle carefully back to the sternum. The cross-clamp time was 122 minutes and the overall bypass time was 153 minutes. Repeat transesophageal echocardiography was then performed after separation from cardiopulmonary bypass. As you can see, it shows significant improvement in the mitral regurgitation, with only mild residual regurgitation. In addition, no mitral stenosis was observed. There was mild septal hypokinesis,but the overall left ventricular function remained unchanged.
The patient was extubated in the intensive care unit approximately 12 hours postoperatively. A minority of younger patients, those with simpler repairs or shorter bypass runs, have been extubated immediately postop, either in the ICU or in the operating room. This patient was transferred to the intermediate-care step down unit on postoperative day one. Except for one dose of morphine just prior to extubation, the patient’s pain was well controlled without narcotics, using ibuprofen alone. The patient was ready for discharge on the fifth postoperative day.
This case demonstrates several key points in the use of the right parasternal approach for minimally invasive mitral valve repair. The patient had a particularly complex and extensive bileaflet repair through this small 6 centimeter incision. This was a result of careful attention in identifying the anatomic landmarks before making the incision and patience while gradually obtaining the exposure one step at a time. Flexibility is also important to this approach and this patient also demonstrates that specific details must be tailored to the individual patient’s anatomy. In this case, we extended the incision cephalad to the second intercostal cartilage instead of caudad to the fourth. In addition, we chose to cannulate the femoral vessels because of the size and position of the ascending aorta. Finally, the limited exposure in this approach makes transesophageal echo critical for defining the anatomy, completely de-airing the heart and assessing the repair.
This patient is typical of some of the more than 200 patients we have now operated on with this approach. What I’d like to do for the next several minutes is show first some data on the first 100 patients through the direct access mitral valve approach by some slides, a brief videotape of some of the things Dr. Aklog has mentioned, go over another group of almost 100 patients who have had aortic valve replacement, and then some summary remarks.
I want to go through with you the first 100 patients we have done at the Brigham beginning in July 1996 and analyzed up through October 1997. There were 100 patients, 56 males and 44 females, ranging in age from 30 to 83 with a mean of 59 years. The mean functional class was 2.4. The etiology of these patients showed that there were 74 with myxomatous degeneration, 14 with rheumatic, 7 with infectious endocarditis, 3 with ischemic and 2 had congenital malformations.
As Dr. Aklog has explained, our general approach has been a parasternal approach for mitral valve surgery. With the increased interest in minimally invasive valve surgery, all the major manufacturing companies have moved ahead and made some interesting and quite flexible and useful cannulae that if you have the right anatomic situation, you can cannulate entirely within the chest cavity. We often use the femoral vessel approach, but in a slightly different way than heretofor. You will notice that the incision is very short, about 5 centimeters, and it parallels the diagonal groin crease and is superior to it. It does not go into the groin crease, and it does not go up and down, which obviously leads to a lot of wound problems. In this 100 patient cohort, there has been a very low incidence of any groin complications whatsoever. The arterial cannula used retrograde is always checked with transesophageal echo to make sure the descending aorta is free of severe atherosclerotic lesions. The femoral vein is cannulated primarily by a purse-string rather than an incision.
This slide shows the way to develop Sondergards’ plane if the left atrium is huge we would go directly into the left atrium through Sondergards’ groove through the 6 centimeter incision. Once you expose the valve, you can do the repair as we will see. This slide shows the right atrial approach. At this point you need both cavae isolated, the aorta crossclamped, and antegrade cardioplegia. You go down through the right atrium and the atrial septum and approach the mitral valve in this manner. Once the septum is incised as you see here, it is retracted so that all you are focused on looking at is the mitral valve and its pathology, shown here with ruptured chordae in the posterior leaflet.
Similar to what we did in this case, a large section of P2 is resected and a rolling leaflet advancement is done so that the heightened areas of P1 and P3 are brought down with a running 4−0 Prolene. The two parts of P1 and P3 are now totally approximated in the midline and a simple running suture of 4−0 Prolene is brought down. At the conclusion of this valvuloplasty, you essentially have two knots: one here at the termination of P3 and one here at the termination of P1. We think this is one of the reasons why the incidence of thromboemboli in this series is extremely low, because the valve area is very smooth. Once this is completed, then the valve is sized by the use of trigone stitches and we prefer to use the Cosgrove ring annuloplasty, as we feel that most of the annular pathology is due to posterior annular dilatation, and this accounts for that extremely well. It also reduces operating time by not having to put stitches in the anterior leaflet.
The closing of the septum is then carried out, the patient is de-aired, and the right atrial wall is closed as well. It should be noted that if you consider putting a temporary pacing wire in, it should be done before you take the cross clamp off, so that the structures are flaccid and can be easily seen and brought into the wound.
To go over some of the details of the mitral valve surgery we have done at the Brigham in this manner, one patient was a reoperative patient and 17 patients had replacement of their mitral valve. Eighty-three had a variety of complex repairs to the mitral valve. The ischemia time and the pump time is a little bit longer using these minimally invasive approaches, but we believe that it is well worth the added time.
The types that we used were 76 Cosgrove rings, 13 St. Jude valves, 14 Hancock porcine valves, 3 Carpentier-Edwards rings, and in some of the cases of endocarditis, we used no ring or prosthetic material at all, a sound surgical principle. Only 39 of 100 patients were transfused. The mean use of red cells was 1.3 units. There were 0 operative deaths in the 100 patients. New postoperative atrial fibrillation occurred in 13 patients. The length of stay was 3 to 30 days with a mean of 5 days. Only 7 patients required postoperative rehabilitation, quite a difference from our usual cohort of valve patients.
There were two late deaths and one patient required reoperation due to a failed repair several months after his initial repair. There was one TIA, one CVA, and no wound infections. Two patients had small postoperative myocardial infarctions of the subendocardial variety. No patients were taken back for bleeding.
The total hospital length of stay is shown here. Thirty-nine of the 100, or close to 40%, had a length of stay equal to or less than 4 days. Another 37 had a length of stay of 5 or 6 days, and less than a quarter of the patients stayed more than 6 days, testifying to the fact that these patients recovered very nicely.
To show you some of the data we have on aortic valve surgery through the minimally invasive approach, in this group over the same time period from July 1996 to October 1997, we did 80 patients who had aortic valve pathology. You might wonder what is the percentage of minimally invasive valve surgery that we now do. In the last six months, it is now almost 80% of all isolated valves that we do. We do not do valves plus coronary bypass, but we do almost every valve this way, except for the exceptions previously mentioned; that is, body habitus being a predominant factor in using this approach as well as in patients that are acutely ill and we want to minimize operative time and bypass time.
In this group of 80 patients, 46 males and 34 females ranging in age from 32 to 90 with a mean of 63 years, the mean functional class was 2.5. Most of these were degenerative or congenital in the sense of calcific aortic stenosis. There were 8 rheumatics, 6 patients had SBE, 4 patients had myxomatous valves, and 4 patients had structural valve degeneration on a porcine valve and were reoperative on through this incision.
Now we have used two approaches here and I will describe both of them. This is the parasternal approach, similar to that of the mitral, but slightly higher in terms of resection of costal cartilage. Femorofemoral bypass, antegrade blood cardioplegia, and transaortic vent with a small pediatric vent are all used. The setup is very similar but you will notice that the incision is slightly higher.
Once the costal cartilages are removed, the aorta comes right up into the wound. As you remember from your physical diagnosis, the aortic second sound is best heard in the right parasternal area at about the second or third intercostal space. An incision is made in the aorta in the usual manner with the hockey stick going down into the noncoronary cusp, and the aortic clamp is applied. Traction sutures on the commissures are often very helpful to elevate the valve into the wound for resection, which is shown here in the usual fashion.
The other approach that we use, and I would say is now our most common approach, is the use of the hemisternotomy, or ministernotomy, which has been popularized by Gundry and colleagues at Loma Linda. The advantage of this technique is that you can almost always use intrathoracic cannulation rather than using the groin, which avoids a second incision. The incision is brought down on the top part and then «T»-d off, or usually «Y»-d off, into the third or fourth interspace. To make it truly minimally invasive, we have tended to use the third interspace. In this exposure, you can see that the ascending aorta can be cannulated and we have used a variety of different cannulation techniques to cannulate the right side of the heart. This slide shows an innominate vein cannula which has been put through a purse string and slid into the right atrium. The right atrium can be directly cannulated by right angle cannula, or, alternatively, one can use in the right femoral vein, a percutaneous approach using a 25 Fr Biomedicus, which works extremely well with assisted venous circulation. The valve replacement is then carried out and the aorta is closed in the usual fashion.
The types of valves we have used are shown here. There were 34 pericardial valves, 28 St. Judes, 11 homograft root replacements, 3 Hancock porcine valves, 2 stentless Freestyle Medtronic valves, and 2 patients had repair. It is important to emphasize once again that you cannot do, in my opinion, minimally invasive valve surgery without the ability to place a transesophageal echo probe down the patient’s esophagus. This ensures air monitoring and prevention of massive air embolus which might occur if you were not able to access the intracardiac images and look at the air.
Eight of these patients were reoperations. Two patients had a right coronary bypass associated with the aortic valve. Mean ischemic time was 100 minutes and bypass time was 129 minutes. Of these first 80 patients, 49 had the ministernotomy and 31 had the parasternal approach. Forty-three of the 80, a little bit more than in the mitral group, were transfused. There were two operative deaths in this group for an operative mortality of 2.5%. One died about three weeks postop from multisystem organ failure, and we learned that in patients who are very acutely ill, you do not want to use this approach because you want to minimize bypass and operative time. The second patient died 4 days postop and was one of the reoperative patients who had had prior coronary bypass grafting. The patient had malignant arrhythmias develop spontaneously on the fourth postoperative day and could not be resuscitated.
In this group, because many of the patients were older, 17 of the 80 required rehabiliation and there were no late deaths in the early followup period. There were no TIAS, one CVA, and one patient developed a sternal infection. This was a woman who had had prior radiation for breast cancer to her mediastinum and that area, which was almost expected to be a wound problem, did become infected. Fortunately, it was only to the third intercostal space; this was skin grafted and the patient did fine. There was one groin infection and one patient was reoperated on for bleeding.
The length of stay is shown here. Twenty-seven patients had a length of stay equal to or less than 4 days. Another 24 stayed 6 days or less, and 29 patients, a little bit longer because of the increased age of the patients, stayed greater than 6 days.
Because of the fact that this has been so very successful and so completely accepted by the patients we have done it in, it has been very hard to do a so-called prospective randomized study. What we did do was go back in the fall of 1996 and in our very first experience, compare our first 50 minimally invasive valve patients who were our first patients versus 50 conventional isolated valve patients done at the same time by the same surgeons in the same hospital to get some idea regarding patient satisfaction, the cost, the length of stay, and the morbidity and mortality. This is not a prospective randomized study, it is a concurrent study, and I think it offers some comparison.
No patient had coronary disease in this group and I think this is a reasonable comparison group. You will note here on the operative results that the operative mortality was the same. Ischemic time and bypass time are longer than in the conventional approach. However, note that red cells used are considerably less than in the conventional group, especially for mitral valve surgery, as noted here. Length of stay averaged one day less.
We had one of our nurse managers who follows all of our patients do a study on whether there was pain and patient return to normality. Looking at pain alone in the minimally invasive versus conventional, there was not a lot of difference in the hospital. At 2 weeks, however, there was a considerable difference on a scale of pain within the entire thoracic cage. Looking at pain medicine usage, 23% of the conventional versus 7% of the minimal group finished their pain medicines and 14% of the minimal group took no medications whatsoever.
In terms of patient satisfaction, there was a clear advantage toward the minimal group, which returned to normal activity considerably faster, almost half as fast as the conventional group. When the question was asked, «When did you feel like yourself?», this was quite strongly in favor of the minimally invasive group. You might be interested to know that costs on a comparative basis were 10−20% less with both mitral and aortic valve minimally invasive direct approach compared to the conventional. Some of this had to do with more blood utilization, more lab tests, and a slightly longer length of stay.
What can we conclude about minimally invasive valve surgery? Certainly at the Brigham and Women’s Hospital we feel pretty committed to this approach. At this time of this Grand Rounds, we have done over 200 patients with this approach. We think it reduces the length of stay and the cost. We definitely believe it requires less blood and blood products and probably, although not conclusively, stimulates less atrial fibrillation postop. We believe that is because there is less trauma involved. We believe overall, counting all the pain sources, as you know that with sternotomy, there is pain not only at the incision, but also in the back and thoracic cage, from the springing-open effect, we believe that pain is less, productivity is up, and the patients feel like themselves much faster.
Most importantly, though, and I think with any of these minimally invasive techniques, and this has got to be the bottom line, that the quality of a valve operation is not affected by the incision size as long as you have the proper monitors to monitor the valve surgery. We also think this minimally invasive valve surgery is a paradigm for the future. As you note on the summary of this slide, there is an increase in patient satisfaction by decreasing pain, increased mobility, and improvement in cosmesis, not an insignificant factor, particularly in female patients. There is decreased length of stay, decreased cost, not only of the in-hospital costs but also of the post-hospital rehabilitation costs, and increase in productivity. Again, there is the same quality of care.
What is the future of this particular area? The HeartPort endoaortic balloon system is now in operation for a couple of years. We think this is a valuable system in some situations. It may be helpful to consider something like this, which may be the ultimate in minimally invasive surgery in the next century. This system is essentially a robotic cardiac system where the surgeon sits at a console manipulating hand controls which manipulate the robotic arms, actually sewing and cutting inside the patient’s chest and heart, and is visualized on the screen.
I think that it is fair to say that minimally invasive cardiac valve surgery is here to stay and will be increasingly accepted. I think it will be accepted more right at the moment than coronary bypass surgery because the quality of the operation can be objectively evaluated by intraoperative transesophageal echo. I think it is important for residents training in cardiothoracic surgery to understand these principles and understand these operations because I think they will become relatively standard in a very rapid way. I think you should also know there is an increase in technology there by virtually every company that manufactures cardiac surgical devices. They recognize this is an important trend and there are remarkable developments under way even as we speak in terms of perfusion technology, cardiopulmonary bypass equipment, retracting systems to handle the increasing desire of patients and surgeons to perform minimally invasive direct access valve surgery. Thank you very much.
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