Asian Cardiovasc Thorac Ann 2004;12:53-57
© 2004 Asia Publishing EXchange Ltd
Assessment Based on EuroSCORE of Ministernotomy for Aortic Valve Replacement
Jean-Marie De Smet, MD,
Benoît Rondelet, MD,
Jean-Luc Jansens, MD,
Martine Antoine, MD,
Didier De Cannière, PhD,
Jean-Louis Le Clerc, MD
Cardiac Surgery Service, Erasme Hospital, University of Brussels, Brussels, Belgium
For reprint information contact: Jean-Marie De Smet, MD Tel: 32 2 555 3817 Fax: 32 2 555 6652 Email: jean-marie.de.smet{at}ulb.ac.be Cardiac Surgery Service, Hôpital Erasme, Route de Lennik 808, 1070 Brussels, Belgium.
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ABSTRACT
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To assess the advantages of a ministernotomy over a standard sternotomy for aortic valve replacement, 191 patients were classified as low-, medium-, and high-risk by EuroSCORE. A ministernotomy was carried out in 100 patients, and a standard sternotomy was used in 91. Among low-risk patients, those who had a ministernotomy showed a marginal increase in atrial fibrillation. Of the medium-risk patients, those who had a sternotomy had significantly more atrial fibrillation and slightly more general infections. In the high-risk subgroup, significantly more atrial fibrillation was observed in the sternotomy group, and more neurologic events were observed in the ministernotomy group; the difference became nonsignificant when only severe events were considered. There was a significant benefit in terms of rhythm disturbances in medium- and high-risk patients who underwent a ministernotomy compared to those who had a full sternotomy. Mortality, duration of intensive care, and hospital stay were not influenced by the operative method.
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INTRODUCTION
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When minimally invasive aortic valve replacement was first described, it was postulated that this approach would favorably influence morbidity, mortality, and hospital costs. Several studies have since shown that a ministernotomy (MS) yields comparable results in terms of morbidity and mortality, at the cost of slightly increased crossclamp and cardiopulmonary bypass (CPB) times.1,2 Aris and colleagues3 in a prospective randomized study, were unable to demonstrate a benefit over the conventional sternotomy (S). Szwerc and colleagues4 reached the same conclusion in a retrospective nonrandomized study. They also found higher incidences of superficial wound infection and pericardial and pleural effusions in the MS group, and suggested that younger patients more concerned by the cosmetic aspects and those more likely to face reoperation would benefit most from a reduced approach. A randomized study by Bonacchi and colleagues5 observed reduced blood loss, comparable rates of atrial fibrillation (AF), and better postoperative pulmonary function in the MS group, in contrast to earlier studies showing no benefit of MS over S in terms of postoperative lung performance.3,6
The continuing quest for smaller incisions led to the proposal of peripheral cannulation techniques for CPB.7 This was challenged on the grounds of increased risk of limb ischemia, venous thrombosis, infection, and lymphoid fistulas.8 It seems that additional efforts to reduce the sternal incision for aortic valve replacement with the aid of peripheral cannulation is not warranted. Intuitively, elderly patients with lung problems or high-risk patients more prone to postoperative complications (prolonged immobilization, lung infections, sternal dehiscence) could benefit from a less invasive approach. Although several authors described risk evaluation of S and MS groups by various scoring systems, such methods have been applied to compare groups rather than the performance of higher-risk patients within each group.3,4 We sought to determine which patients classified according to the EuroSCORE system would benefit from a minimally invasive approach.
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PATIENTS AND METHODS
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One hundred consecutive patients who underwent isolated aortic valve replacement by MS since the introduction of this technique in our service in 1998 were compared with a retrospective series of 91 consecutive patients operated on by a full sternotomy immediately before 1998. Although some surgeons in the service continued to operate by the standard method after 1998, it was difficult to compare these patients with the MS group as individual preferences and experience could introduce bias. Also, true randomization is difficult to obtain in a large series of patients over an extended period of time because of the patients’ and referring physicians’ preference for less invasive techniques. Therefore, it was considered preferable to perform a retrospective study as no other technical modification had been introduced during this period.
All patients were evaluated preoperatively according to the EuroSCORE risk system. This additive score of predicted mortality was developed from a database of 19,030 patients, and identified 16 risk factors by univariate and logistic regression analysis. Each factor has a weight from 1 to 3, allowing the classification of patients into low-risk (score 0–2, expected mortality 1.27%–1.29%), medium-risk (score 3–5, expected mortality 2.90%–2.94%), and high-risk (score 
6, expected mortality 10.93%–11.54%).9 Mortality and morbidity were evaluated in accordance with the guidelines published by the Ad Hoc Committee for Standardizing Definitions of Prosthetic Heart Valve Morbidity.10 Data are presented as mean value ± standard deviation. Comparison between S and MS data were made by unpaired t test. Differences were considered significant when p values were less than 0.05.
Contraindications to MS included poor ventricular function, enlarged aortic root, and extensive aortic calcification.11 The operation was conducted similarly in both groups, except for the sternal incision. After opening the sternum and suspending the pericardial edges, the aorta and right atrium were cannulated with a 24F DLP straight-tip cannula (Medtronic, Inc., Minneapolis, MN, USA) and a RMIdual-stage drainage cannula (Baxter Healthcare, Irvine, CA, USA), respectively. The CPB was conducted at 2.4 L·m-2 with moderate hypothermia (34°C rectal). A left vent was inserted through the right superior pulmonary vein. The aorta was crossclamped and 800 mL of St. Thomas’ Hospital cardioplegic solution was infused into the aortic root, in conjunction with topical cooling. Additional doses of cardioplegia were infused into the coronary ostia after opening the aorta. Retrograde cardioplegia was not used in the MS group, and applied in only a few cases in the S group. After aortic valve excision and annulus debridement, a prosthetic valve was inserted with interrupted braided sutures. In the MS group, the sternal incision was skewed in a J shape towards the 3rd or 4th right costal interspace, according to the surgeon’s preference. Transesophageal echocardiography was routinely used in all patients to facilitate left-side deairing and to monitor weaning from CPB.
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RESULTS
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The S and MS groups were comparable in terms of age, overall EuroSCORE, CPB and crossclamp times (Table 1
). The male/female ratio was statistically different (1.39 in the S group vs. 0.92 in the MS group, p = 0.02), possibly reflecting a choice of more cosmetic incisions in the female group. Blood loss was similar in the S and MS groups. A root enlargement procedure was necessary in 2 cases in the MS group (Manougian’s method). In one MS case, a tear at the level of the aortic clamp was repaired under a brief period of deep-hypothermic circulatory arrest. In another MS case, malfunction of a bileaflet prosthesis was corrected by repositioning. These additional procedures were performed without extending the sternotomy. Five patients in the MS group required conversion to a full sternotomy: 3 for control of bleeding (aortic suture line in 1, left vent insertion in 2), one for anterior ischemia treated by coronary bypass, and one for foreign body retrieval. No mortality occurred in these 5 patients and they were not included in further analysis of the postoperative complications.
Reoperation for bleeding or pericardial drainage was necessary in 3 patients in the MS group and in 2 patients in the S group. Overall mortality, intensive care unit (ICU) stay, and hospital stay were similar for both groups.
Morbidity in the MS and S groups is compared in Table 2. Postoperative morbidity was classified as any event requiring a specific diagnostic or therapeutic intervention. Infection was recorded as the need for antibiotic administration. Atrial fibrillation was defined as new onset of supraventricular arrhythmias at any time during the postoperative period, recorded by continuous monitoring. The incidence of new-onset postoperative AF was significantly higher in the S group than the MS group (Table 1
). Among the high-risk patients, those in the S group experienced substantially more AF than those in the MS group (Table 2). In contrast, AF in low-risk patients was found predominantly in the MS group. The small sample size makes comparison difficult within the high-risk subgroup. All cases of new-onset AF were treated with intravenous amiodarone (900 mg per day) followed by oral amiodarone (1200 mg per day). All patients reverted to normal sinus rhythm before discharge.
Neurologic events occurred in slightly more patients in the MS group, and all of these events occurred in high-risk patients. Among the 3 cases in the MS group, one temporary deficit resolved after 24 hours, and one was diagnosed after auditory loss; both patients had negative brain computed tomography scans. The only severe deficit with a positive computed tomography scan occurred in a 77-year-old patient who died on postoperative day 30 due to sepsis after wound dehiscence. In the only neurologic event in the S group, severe brain injury was confirmed by computed tomography and a permanent deficit was present at discharge. Infection requiring specific antibiotic treatment was more prevalent in the S group. No infections occurred in the low-risk patients in either group. In the medium-risk patients, there was one wound infection in each group, 2 patients had a pulmonary infection, and 2 had a urinary tract infection in the S group. In high-risk patients, wound infection occurred in 2 patients in each group. One patient in each group required an intervention for wound drainage and sternal rewiring.
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DISCUSSION
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This study confirms the previous findings of similar outcomes in terms of operative parameters, ICU stay, and hospital stay in MS and S patients, even when classification into risk subgroups is performed. The high-risk patients showed a trend towards reduced morbidity after the MS, in terms of rhythm disturbances and overall infection rates. Wound infection rates were not affected by the surgical approach. Neurologic events occurred more frequently in high-risk patients in the MS group. However, when only severe brain injuries on computed tomography were considered, the difference was not significant. The effect of the operative procedure on adequate deairing is only speculative as no neurologic incidents were recorded in the other subgroups.
Our data concur with those of other series as no striking differences were found between MS and S groups in terms of serious operative or perioperative events. Bonacchi and colleagues5 stressed the advantages of the MS in terms of postoperative pulmonary function tests, which should favorably influence the outcome in patients with compromised lung function. However, this theoretical benefit did not translate into significant results in the present study, even when the higher-risk groups were considered. The lower overall morbidity in the medium- and high-risk MS patients can be almost entirely ascribed to a reduction in postoperative rhythm disturbances, and this contrasts with other series. Although the cannulation techniques and thus the extent of right atrial manipulation were similar, a plausible explanation suggested by Machler and colleagues1 is the more limited pericardial incision, possibly influencing the level of postoperative pericardial irritation and inflammatory response; they found supraventricular arrhythmias in 26% of S patients and only 1.6% of MS patients. Another hypothesis concerns the amount of postoperative drainage, although no significant difference was found in our series. Bonacchi and colleagues5 noted a significant reduction of postoperative blood drainage, but the incidence of AF was similar in each group (7.5% in S group vs. 10% in MS patients). A favorable influence of MS on durations of ICU and hospital stay was reported by some authors, but denied by others.3,5,12 These parameters can be influenced by institutional policies such as the implementation of "fast-track" programs, rehabilitation facilities, or financial considerations. The mean age of our MS patients was 69.7 years, and these elderly patients often regard early discharge with anxiety. The role of the caring physician is central when pressure for early discharge, before full rehabilitation, is caused by financial factors.
The findings in this study focusing on patients classified into risk subgroups according to the EuroSCORE system, showed that the only significant advantage of MS over S was in a reduction in supraventricular arrhythmias in the medium- and high-risk groups. This advantage did not influence mortality, length of ICU stay, or hospital stay. Thus, the intuition that the oldest and most debilitated patients might present less pulmonary, infectious, or sternal complications is not supported by our data. The retrospective nature of the study has inherent limitations, and the splitting of the studied population into subgroups limits the statistical power of our data by lowering the sample sizes. However, in the higher-risk subgroup containing 51 MS and 40 S patients, the absence of significant differences in overall infections, wound infections, and sternal dehiscence confirms the suspicion that less invasive surgery by MS does not influence the postoperative course in these patients. The fact that the surgeons were free to select the type of procedure could have introduced a bias, as more experienced surgeons tended to prefer MS over S. Interestingly, even this did not influence the results in favor of MS when comparing retrospectively the series of patients operated on by all surgeons via the standard method. This tends to indicate an absence of benefit due to the minimally invasive procedure. Other issues such as the cosmetic result, degree of postoperative pain, and incidence of paravalvular leaks have been debated also without conclusive results, and they were not considered in this study. The potential advantage of a previous MS when undertaking later reoperations awaits long-term follow-up studies.
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ABSTRACT
INTRODUCTION
