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Eur J Cardiothorac Surg 1998;14:S117-S121
© 1998 Elsevier Science NL

S-shaped in comparison to L-shaped partial sternotomy for less invasive aortic valve replacement ¹

Universität Leipzig, Herzzentrum, Klinik für Herzchirurgie, Russenstrasse 19, 04289 Leipzig, Germany

^* Corresponding author. Tel.: +49 341 8651422; fax: +49 341 8651452.

	Abstract

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion 5. Conclusions References

 
Objective: Evaluation of less invasive aortic valve replacement to minimize surgical trauma and achieve a better postoperative quality of life. Methods: Thirty-three patients had aortic valve replacement using a 4–6 cm small incision and partial sternotomy only. Partial sternotomy was performed proximal (16), S-shaped (14) or horizontal (3). Access for cardiopulmonary bypass was via sternotomy (24) or the right femoral vessels (9). Patient age was 58±13 years, 21 had aortic stenosis and 12 aortic incompetence. Results: Surgical exposure was sufficient and allowed for uncomplicated AVR in all patients. Mechanical valves (20), conventional bioprostheses (3), stentless bioprostheses (9) or a homograft (1) were implanted. Crossclamp time was not prolonged in comparison to the conventional technique. Intensive care stay and hospital stay were 1 and 10 days, respectively. One patient had to be reoperated for paravalvular leakage, two patients (horizontal sternotomy) had sternal dehiscence. Postoperative pain was low in most patients. Conclusion: Less invasive aortic valve replacement is feasible with good functional results. The S-shaped sternotomy approach is advantageous whereas the horizontal sternotomy is no longer performed due to a high rate of instability. This new technique will be further evaluated in comparison to the conventional approach.

Key Words: Aortic valve replacement • S-shaped partial sternotomy • L-shaped partial sternotomy

	1. Introduction

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion 5. Conclusions References

 
Aortic valve replacement (AVR) is currently performed in a standard fashion using a median sternotomy approach [1–3]. Despite standardization there is a considerable trauma for the patient that results from the incision itself as well as the use of extracorporal circulation and cardiac arrest [4]. Recently minor invasive techniques were introduced for AVR in an attempt to reduce trauma and thereby improve the outcome for the patient at a comparably low risk. By minimizing the surgical trauma and the number of postoperative transfusions the operation is supposed to have less impact on the patients general health status. A fast and uneventful postoperative recovery is expected. The use of several different new techniques by different surgeons during the last months reflects that less invasive cardiac surgery currently is an evolving field. All techniques consist of a smaller incision but there are several differences. Cosgrove described a right parasternal thoracotomy from the third to the fourth costal cartilage [5]. Other groups perform a proximal partial median sternotomy [6]or a horizontal sternotomy as well. In addition to these techniques we are describing a new approach that has been developed in order to preserve the continuity of both the upper and the lower bony thoracic circumference [7]. Aim of this study was to prospectively analyze the perioperative feasibility using different approaches for minor invasive AVR as well as to evaluate the postoperative outcome and quality of life for the patients.

	2. Methods

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion 5. Conclusions References

 
2.1 Less invasive approach
In this study the less invasive in comparison to the conventional approach for AVR were a smaller cutaneous incision, a ministernotomy, retrograde or antegrade perfusion and deairing primarily via the aortic root. Three different methods were evaluated as shown in Fig. 1 : group 1, upper partial sternotomy in 16 patients; group 2, S-shaped sternotomy in 14 patients; group 3, horizontal sternotomy in three patients. The upper partial sternotomy (group 1) is performed using a usual sternal saw for the proximal half of the sternum, then it is completed by moving to the fifth right intercostal space. The S-shaped approach was developed at our institution to retain maximum stability of the upper and lower thoracic rim. The oscillating saw is used to perform a partial median sternotomy from the second to the fifth intercostal space. Then it is completed by a left horizontal incision to the second intercostal and a right horizontal incision to the fifth intercostal space. Intraoperatively, all conventional instruments and a specially designed smaller spreader were used to facilitate the approach through the smaller sternotomy. Cold crystalloid selective cardioplegia (Bretschneider HTK solution) and moderate hypothermia were applied. Valve implantation was performed using a standard technique with interrupted pledgeted sutures in a supraannular position for all stented valves. Stentless bioprostheses were implanted in a subcoronary position with interrupted sutures and a running suture line at the top using the freehand technique. Approval from the local ethical committee was obtained and all patients gave written informed consent after the study had been outlined in detail.

View larger version (95K): [in this window] [in a new window]   Fig. 1. The three different approaches for sternotomy are shown. These are upper median sternotomy (group 1), S-shaped sternotomy (group 2), or horizontal sternotomy (group 3).

2.3 Intra/postoperative treatment
All patients were treated according to standard intraoperative regimen. Anesthesia was performed using fast acting drugs (propofol and sufentanil). Patients had short-term postoperative ventilation with early extubation and fast-track intensive care therapy if possible. Mobilization was begun immediately after extubation. Postoperative in-hospital stay was attempted to be short and took about 1 week according to the German standard of early inhospital rehabilitation.

2.4 Follow-up and statistics
Follow-up consisted of daily visits during the intraoperative stay with physical examination and a modified standard questionaire for postoperative quality of life including the Nottingham Health Questionnaire [8]. Transthoracic echocardiography was performed at 1 week as well as at 6 months postoperatively and is being performed annually thereafter. Valve related morbidity and mortality is reported according to standard guidelines [9]. All patients had pre- and postoperative transthoracic echocardiography at standard views and hemodynamically stable conditions. Pressure gradients were calculated according to the Bernoulli formula with correction for left ventricular outflow tract velocities. For calculation of valve orifice areas the continuity equation was used. Statistical analysis was performed using the SPSS statistical package (SPSS, Chicago, IL, USA), the Student's t-test was applied. Data are the mean±SD.

	3. Results

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion 5. Conclusions References

 
3.1 Surgery
The surgical exposure of the aortic valve was sufficient in all patients. Thus valve replacement was performed without any restrictions resulting from the smaller surgical access. Nevertheless three patients had to be converted to a conventional sternotomy (two in group 1 and one in group 2). Conversion was required due to a tear of the ascending aorta, additional venous bypass grafting to the right coronary artery when calcific emboli was suspected and reconstruction of the aortic annulus, respectively. Conversion was easily possible without any additional complications for the patients. Intraoperative conversion to a complete sternotomy could be performed immediately in all patients. The aortic valve procedure could be performed as scheduled in all patients. Twelve patients received a biological aortic valve (conventional, 3; stentless biological, 9). Twenty patients had mechanical AVR and one patient received a homograft. Extracorporeal circulation was initiated via the femoral vessels in nine and by direct thoracic cannulation in 24 patients, respectively. Direct thoracic cannulation was possible if the sternotomy was extended beyond 5.5 cm, as such it was performed in all patients of group 1, in seven patients of group 2 and in one patient of group three.

Femoral cannulation in the remaining 9 patients was initiated by a small horizontal incision after preoperative ultrasound scanning and absence of atherosclerosis. There were no postoperative complications from femoral cannulation in any patient. The whole operation lasted 143±34 min, extracorporeal circulation took 104±28 min and aortic crossclamp times were 69±15 min, respectively. During the conduct of the study there was a learning curve and a trend towards shorter crossclamp times. Recently they were in the range of 50–55 min.

3.2 Postoperative course
The immediate postoperative course was uneventful in all patients. All patients were in a hemodynamically stable condition requiring only minimal doses of inotropic support in the very first postoperative hours. Overall postoperative blood loss was low at an average of 310+75 ml. Patients were extubated after an average of 9 h (range 4–42). Duration of intensive care stay was one day on average, it took 19 h (6–53). In-hospital stay was 10 days (range 8–16). Postoperative complications were as follows: rethoracotomy using the minithoracotomy had to be performed in one patient for excessive bleeding of 950 ml, recovery was uneventful. One patient had to re-intubated on the third postoperative day for 48 h due to pneumonia. At 1 week postoperative echocardiographic control paravalvular leakage was diagnosed in two patients. Both had an heavily calcified aortic annulus intraoperatively. Reoperation had to be performed in one of these patients with grade 3 valvular incompetence whereas the other patient who had only moderate incompetence and was in NYHA-class 1 could be discharged.

A sternal dehiscence was seen in three patients at 5–7 days, postoperatively. Two of these patients had a horizontal sternotomy (group 3). Both had no significant clinical symptoms and breathing was not impaired. Therefore they could be discharged. The third patient had an upper proximal sternotomy (group 1) and had transitional psychosis postoperatively. He was reoperated, later on his course was uneventful.

3.3 Follow-up/quality of life
Postoperative quality of life was comparable to a control group having conventional AVR. On average mobilization was performed half a day earlier after less invasive AVR which resulted in a slightly better functional state on the seventh postoperative day. Postoperative pain levels were comparable in both groups as shown in Fig. 2 . Nevertheless all but one patient were happy with their decision to have less invasive AVR and would choose the same approach again when asked at follow up. At follow up transthoracic echocardiography revealed normal valve function in all patients.

View larger version (85K): [in this window] [in a new window]   Fig. 2. Postoperative pain during the first week postoperatively and measured on a daily basis using the visual analogue scale (0, no pain; 10, maximal pain the patient could ever imagine). The lower curve represents all patients after less invasive AVR; measurements for a similar group after conventional AVR are shown in the upper curve. There were no statistically significant differences between groups.

	4. Discussion

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion 5. Conclusions References

Any new surgical technique has to be evaluated in comparison to standard treatments. As such, other studies as well as our own data underline, that less invasive AVR, which has been used for a few months only thus far, is technically feasible at similar results than the conventional approach. Comparably high safety of a new procedure is of utmost importance for the patients and necessary to justify the further use of these techniques.

4.1 Surgery
When using a less invasive approach for aortic valve replacement good exposure it is essential to be able to perform valve replacement procedure as exact as possible. Due to the fact that the ascending aorta anatomically is relatively anterior with little distance from the sternum, an almost perfect exposure can be anticipated from a partial sternotomy. In addition, the pericardium that is not completely opened in less invasive operations keeps the heart and the ascending aorta in an anterior position.

4.2 Sternotomy
The rationale for a smaller incision with less dissection of the bony thorax is to achieve better postoperative stability as well as possibly less pain and lower risk of infection due to the smaller wound itself. In this study a upper median (group 1) or a S-shaped partial sternotomy approach (group 2) were used most frequently. With both techniques the lower circumference of the bony thorax remains intact. The S-shaped approach is advantageous because the upper bony circumference remains intact as well. Nevertheless exposure is not as good as in group 1. Due to the smaller access in group 2 half of the patients required femoral cannulation. However this did not lead to any procedure-related problems for the patients. At present we would recommend the S-shaped approach in patients having a relatively low body weight whereas the upper median sternotomy should be used in all obese patients and in circumstances where femoral cannulation is contraindicated. After horizontal sternotomy bony dehiscence was a frequent problem. Therefore the horizontal approach cannot be recommended and is not used in our series any more. The parasternal approach seems to have the disadvantages of cartilage resection that might result in costal instability and considerable postoperative pain and discomfort for the patient. In addition the right internal thoracic artery is commonly sacrificed which is not justified in younger patients.

4.3 Perioperative monitoring
As the complete heart and especially the left and right ventricles are not exposed, a Swan–Ganz catheter as well as intraoperative transesophageal echocardiography (TEE) were routinely used in this series of less invasive AVR. TEE allows monitoring of left ventricular function, filling status, valve function as well as administration of cardioplegia and deairing in all patients. It can easily be performed in parallel by one of the surgical residents or by any trained anesthesiologist. After this experience we consider TEE monitoring sufficient and retain a Swan–Ganz catheter for patients having decreased ventricular function.

4.4 Conversion
Intraoperative problems were rare in the present study, mostly because of the good exposure that could be achieved. If necessary, conversion to conventional sternotomy can be performed quickly without problems. This further contributes to the safety of the procedure.

4.5 Quality of life
As yet no differences in postoperative pain were seen in the patients having less invasive AVR in comparison to a group of patients after a conventional operation. This could be anticipated because spreading of some ribs might cause the same pain as usual. Nevertheless earlier mobilization could be achieved in patients after less invasive AVR. This is advantageous for general recovery. Furthermore faster and better recovery lead to a shorter in-hospital stay and may reduce overall costs. The patient himself might be a trigger for early mobilization: If patients realize a smaller incision, this may make them think that the operation itself was less invasive and leads to earlier active mobilization.

4.6 Advantages
This study shows that less invasive AVR is a useful technique for reduction of perioperative trauma and blood loss. There are less reasons for potential infection or blood loss when a smaller incision is made. The intact pericardium is of great value to keep the heart in a fixed position as well as to facilitate any reoperation if necessary.

	5. Conclusions

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion 5. Conclusions References

 
Less invasive AVR is a promising new technique. It has a low perioperative risk and can be applied with acceptable results in almost all patients. Future efforts should be directed to further improve of the surgical access, maybe in conjunction with the development of some special surgical instruments. Alternative techniques of implantation, for example staplers, would be useful to reduce crossclamp times. Nevertheless all new developments have to be as safe as any conventional technique. Overall costs and long-term benefit for the patients have to be assessed in the future. Due to the sufficient surgical access in future the indication for less invasive operations could be extended to all different procedures on the aortic valve itself as well as complex procedures as aortic valve reconstruction. As such less invasive techniques for aortic valve operations are a promising new approach. Advanced techniques will be further developed and less invasive AVR is worth pursuing.

	Footnotes

 
¹ Presented at the World Congress on Minimally Invasive Cardiac Surgery, Paris, May 1997.

	References

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion 5. Conclusions References

 

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3. Collins JJ. The evolution of artificial heart valves (Editorial). N Engl J Med 1991;324:624-626.[Medline]
4. Diegeler A, Falk V, Walther T, Mohr FW. Minimally invasive coronary artery bypass surgery without extracorporeal circulation (Letter). N Engl J Med 1997;336:1454.[Free Full Text]
5. Cosgrove DM, Sabik JF. Minimally invasive approach for aortic valve operations. Ann Thorac Surg 1996;62:596-597.[Abstract/Free Full Text]
6. Konertz W, Waldenberger F, Schmutzler M, Ritter J, Liu J. Minimal access valve surgery through superior partial sternotomy: a preliminary study. J Heart Valve Dis 1996;5:638-640.[Medline]
7. Autschbach R, Walther T, Falk V, Diegeler A, Schilling L, Metz S, Mohr FW. Minimal invasiver Aortenklappenersatz. Z Kardiol 1997;86(Suppl. 2):298.[Medline]
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