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Ann Thorac Surg 1999;67:1583-1587
© 1999 The Society of Thoracic Surgeons

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Original Articles

Ministernotomy versus median sternotomy for aortic valve replacement: a prospective, randomized study

^a Departments of Cardiac Surgery, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
^b Department of Anesthesia, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain

Address reprint requests to Dr Aris, Cardiac Surgery Service, Hospital de la Santa Creu I Sant Pau, Avenida San A.M. Claret 167, 08025 Barcelona, Spain
e-mail: aaris{at}hsp.santpau.es

Presented at the Thirty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 25–27, 1999.

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. Minimally invasive aortic valve replacement reduces surgical trauma and, supposedly, postoperative pain, blood loss, and length of stay. A prospective, randomized study was designed to prove these theoretical advantages.

Methods. Forty patients undergoing isolated, elective aortic valve replacement were randomized into two equal groups. Patients in group M underwent aortic valve replacement through a ministernotomy (reversed L or reversed C). In group S, a median sternotomy was used. The anesthetic and surgical protocol was identical for both groups. Pain was evaluated on a daily basis. Pulmonary function tests were performed preoperatively and before hospital discharge in all patients.

Results. There were two deaths in each group. Cross-clamp time was longer in group M: 70 ± 19 minutes versus 51 ± 13 minutes in group S (p = 0.005). There were no statistically significant differences between groups M and S in pump time (95 ± 20 minutes versus 83 ± 19 minutes), extubation time (9.9 hours in both groups), chest drainage (479 ± 274 mL/ 24 hours versus 355 ± 159 mL/ 24 hours), transfusion requirements (27% in both groups), pain evaluation (1.34 ± 1.3 versus 2.15 ± 1.5), length of stay (6.2 ± 2.3 days versus 6.3 ± 2.5 days), and cosmetic appraisal. Forced vital capacity decreased 26% from preoperative reference values in group M and 33% in group S (p = not significant). Forced expiratory volume in 1 second decreased 22% and 35%, respectively (p = not significant).

Conclusions. This study has failed to prove the theoretical advantages of minimally invasive aortic valve replacement. With this technique, cross-clamp time is longer than with a median sternotomy.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
To reduce surgical trauma several techniques of non-videoscopic minimally invasive valve operation have been reported [1–5].

Claims of reduction in costs, length of stay [6, 7], postoperative pain [8], and blood loss have been based on studies with matched population undergoing valvular procedures through a standard median sternotomy. Despite several cautionary articles and editorials claiming for patient randomization [9–13], no studies have been published to date comparing ministernotomy and median sternotomy for aortic valve replacement (AVR) on a randomized fashion. We present our results of a prospective, randomized study comparing both approaches. The study was undertaken after our initial experience with minimally invasive AVR through a transverse sternotomy [14]. Thus, operative times were not affected by a learning curve.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
Forty consecutive patients undergoing first-time, elective, isolated aortic valve replacement were randomized (computer-generated randomization) into two groups. Twenty patients underwent AVR through a ministernotomy (group M) and in the remaining 20 patients the procedure was done through a median sternotomy (group S). Ages ranged between 26 and 76 years, with a mean of 64 ± 11 years. The protocol of the study was approved by the Departmental Research Committee and informed consent was obtained in all patients. None refused to enter the study, which was completed in a period of 4 months. The envelope containing the type of incision for each individual patient was opened by the scrub nurse, before the setting of the instrument table. In group M, 13 patients underwent a reversed "L" ministernotomy, from the sternal notch to the right fourth intercostal space. In the remaining 7 patients, a reversed "C" (or "J") incision between the first or second intercostal space to the fourth or fifth, depending on the shape of the chest, was performed (Fig 1 ).

View larger version (33K): [in this window] [in a new window]   Fig 1. Patients in group M underwent a reversed "L" (left) or a reversed "C" (right) ministernotomy.

Anesthetic protocol consisted in induction with etomidate and fentanyl, with pancuronium used for muscle relaxation and propofol infusion for maintenance of anesthesia to promote early extubation. Pain medication included continuous infusion of metamizol (Nolotil; Europharma, S.A. Barcelona, Spain) at the rate of 4 g/ 12 hours while in the intensive care unit and oral acetaminophen (500 mg) and codeine (30 mg) while on the floor.

The following data was prospectively collected: cross-clamp and pump times, time to extubation, chest drainage during the first 24 hours, number of blood transfusions (for hemoglobin below 7.7 g/dL), intensive care unit and total postoperative length of stay. In addition, pain was evaluated on a daily basis by a visual analog scale [15]. All patients underwent preoperative pulmonary function tests, which were repeated before hospital discharge. At this point, patients were asked to evaluate subjectively the cosmetic effect of the incision. A numerical scale ranging from horrible (1) to wonderful (5) was used for this purpose. Statistical analysis was performed using the Student’s unpaired t test. For comparison of qualitative variables, the ² test was applied. A p value less than 0.05 was considered significant. Results are expressed as mean ± standard deviation.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Both groups were similar in age, body surface area, number of cases of aortic stenosis versus aortic regurgitation, left ventricular ejection fraction, and estimated operative risk [16] (Table 1). Results in group M include both inverted L and C incisions because a preliminary statistical analysis showed no differences among them (p values ranging from 0.27 to 0.8).

Operative times
Aortic cross-clamp time was 70 ± 19 minutes in group M and 51 ± 13 minutes in group S (p = 0.005). Pump time was 95 ± 20 minutes in group M and 83 ± 19 in group S (p = 0.1). (Patients who died were excluded from this calculation.)

Postoperative course
Patients were extubated a mean of 9.9 ± 8 hours after operation in group M and 9.9 ± 4.5 hours in group S (p = 0.8). During the first 24 hours postoperatively, chest drainage was 479 ± 274 mL in group M and 355 ± 159 mL in group S (p = 0.11). When divided by body surface area, these differences were even less significant (263 ± 148 mL/m² versus 200 ± 76 mL/m², respectively).

Five of the survivors in each group required blood transfusion, as defined by a serum hemoglobin below 7.7 g/dL. Number of red cell units per patient was 0.37 in group M and 0.33 in group S (p = 0.20).

Mean postoperative intensive care unit stay was 1.83 ± 0.7 days in group M and 1.94 ± 1 days in group S (p = 0.76). Total postoperative length of stay was 6.3 ± 2.3 days for group M and 6.3 ± 2.4 days for group S (p = 0.8). All patients were discharged with anticoagulation levels within the therapeutic range.

Postoperative pain
Daily evaluation of pain by a visual analog scale allowed numerical calculation of the degree of pain. Six patients in group M and 4 in group S did not experience any pain on the first postoperative day. Two patients in each group rated zero the amount of pain for their total hospital stay. Average pain values were 1.34 ± 1.3 in group M and 2.03 ± 1.5 in group S (p = 0.22).

Complications
Atrial fibrillation was the most common complication. Four patients (22%) in group M and 2 in group S (11%) developed new, rapid atrial fibrillation in the postoperative period. Three and 1 patient, respectively, required electric cardioversion. The remaining 2 patients reverted to sinus rhythm with pharmacologic treatment. One patient in group M presented mental confusion that cleared before discharge and other a pericardial effusion that required surgical drainage. There were no wound or sternal complications.

Pulmonary function tests
Forced vital capacity (FVC) decreased substantially during the postoperative period. Preoperative FVC was 79% (± 14) of reference values in group M and 79.5% (± 20) in group S. Postoperatively, FVC fell to 60% (± 17) and 53% (± 12), respectively (p = 0.20).

Preoperative forced expiratory volume in 1 second (FEV₁) was 79% (± 14) and 81% (± 21) in each group. Postoperatively, FEV₁ decreased to 62% (± 16) and 52.6% (± 12), respectively (p = 0.08) (Fig 2 ).

View larger version (16K): [in this window] [in a new window]   Fig 2. Changes in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) in group M (solid line) and in group S (dashed line) after operation. The differences were not statistically significant.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
At the World Congress on Minimally Invasive Cardiac Surgery, which took place in Paris at the end of May 1997, 12 papers or posters were presented on minimally invasive AVR [17]. Five different incisions were used to approach the aortic valve: transverse sternotomy (3), superior hemisternotomy (3), inverted T (2), reversed L (2), and parasternal (2). Some investigators compared their results with matched population undergoing standard AVR and claims of potential advantages with their techniques were not substantiated. The lack of randomized studies on the subject prompted us to undertake the present study. After an initial experience with the transverse sternotomy approach [14], we elected to use the reversed L (or j [4]) or the reversed C [18] (or J) ministernotomy because standard cannulation and instrumentation are used and there is no sacrifice of the internal mammary arteries. The slight difference between both incisions (reaching the sternal notch or not) did not alter the overall results of the study.

Our results show that there is not significant differences between ministernotomy and median sternotomy in terms of bleeding, length of stay, pain, and cosmetic effect. Results may be limited by the number of patients. With larger numbers, some differences could have reached statistical significance.

The mortality of this series is higher than expected in AVR and does not reflect our reported mortality in AVR. In a previous report on valve procedures by our group [19], operative mortality for AVR was 2.9% and in our 7 years’ experience with the Monostrut prosthesis (Alliance Medical, Irvine, CA) [20], first-time isolated AVR carried a mortality of 0.37% (1 of 266 patients). Deaths in group M were attributable to coagulopathy in a 74-year-old man with extreme fragile aorta and to improper myocardial protection in a patient with a right coronary anomaly. Two such patients have been reported recently [21, 22]. In retrospect, this patient and the 2 patients who died in group S, could have benefited from retrograde cardioplegia. Since operating on these patients, we now routinely combine antegrade and retrograde cardioplegia in all AVR. Nevertheless, the estimated operative risk for both groups, according to the original score developed by Parsonnet and colleagues [16], was between 5% and 10%. Age more than 70 years, female gender, high transvalvular gradient (> 119 mm Hg), and concomitant diseases (diabetes, hypertension) accounted for a rather high Parsonnet score in many patients. Blood loss was not reduced with ministernotomy. The differences between both groups were not significant and are in consistent with the numbers reported by Cosgrove and associates [6] in AVR through a right parasternal approach. Thirty percent of their patients received a mean of 1.1 units of blood, similar to 27% in our two groups. However, patients in group M received only a mean of 0.37 units of blood. Svensson and D’Agostino [8] reported 0.86 units with the J/j incision and Cohn and colleagues [7] reported 2.2 units in 66% of their patients with a parasternal or a reversed T incision. In a study from our institution comparing aprotinin and desmopressin in patients undergoing operations with cardiopulmonary bypass [23], average chest drainage in aprotinin-treated patients, during the first 24 hours was 195 mL/m², very similar to 263 and 200 mL/m² found in both groups of the present study. Reduction of postoperative pain is a theoretical advantage of minimally invasive valvular procedures. This was not proven in hospitalized patients with ministernotomy when compared with other patients operated during the same period through median sternotomy [7]. Svensson and D’Agostino [8] found less morphine requirements with the J/j incision, but there were no differences as far as requirements for oral pain medication. In their article, they wisely stated: "A more sophisticated method of quantifying patients’ postoperative pain and discomfort in a randomized study would be required to prove pain is less in the hospital with minimal-access procedures." Our study suits well their request. The visual analogue scale [15] is a validated system of quantifying pain and it was applied to our patients on a daily basis. There was a tendency toward less postoperative pain in group M, although it did not reach significant differences. A larger group of patients may have yielded different results.

Postoperative atrial fibrillation remains a problem even with minimally invasive AVR. In our initial experience with AVR through a transverse sternotomy [14] we found an incidence of 20% despite the fact that femoral vein cannulation was used and the right atrial appendage was not manipulated. Cohn and colleagues [7] found 27% of new postoperative atrial fibrillation in patients undergoing AVR through a ministernotomy and Weinschelbaum and associates [24], 12.6% in valvular operations through a parasternal approach. In our study, atrial fibrillation developed in 4 of the 18 survivors of group M and in 2 of group S. The numbers are too small to be significantly different, but it shows that despite a limited pericardial incision and minimal cardiac manipulation, postoperative arrhythmias may occur. Length of stay was not affected by ministernotomy. Hospital stays of 5 to 6.5 days have been reported [6, 7, 24], but we do not favor early discharge during the process of adjusting anticoagulation dosage, especially in older patients. Nevertheless, one-third of the patients in each group were discharged on the fifth postoperative day.

Reports of pulmonary function studies after AVR are scarce and most of the reported series are related to patients undergoing coronary operations. Cohen and colleagues [25] found a reduction of 40% in FVC and 39% in FEV₁ postoperatively in patients undergoing median sternotomy without dissection of the internal mammary artery, whereas Shapira and associates [26] found a similar reduction of 33% and 32%, respectively.

We did not find any beneficial effect of a minimally invasive approach on postoperative ventilatory dysfunction. All patients presented a nearly normal FVC preoperatively (above 60% of reference values) and only 2 patients in group S had a FEV₁ below 60% of reference values. However, patients showed a reduction of 26% and 33% in FVC and of 22% and 35% in FEV₁ in groups M and S, respectively. Again, a larger number of patients could have shown statistically significant differences.

Subjective evaluation of cosmetics was not influenced positively by ministernotomy. Patients did not react enthusiastically to smaller incisions, and female patients were more critical than male patients. The fact that most of them were elderly (nearly half were septuagenarians) and not particularly cosmetic-oriented may have played a role in their appraisal.

In conclusion, the present study has failed to show the theoretical advantages of ministernotomy over conventional median sternotomy for AVR. Future studies, with larger number of patients may be needed to prove the superiority of minimally invasive techniques.

	References

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Alejandro Aris Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Aris, A. Articles by Litvan, H. Search for Related Content PubMed PubMed Citation Articles by Aris, A. Articles by Litvan, H.