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Ann Thorac Surg 2002;74:2016-2021
© 2002 The Society of Thoracic Surgeons

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Original article: cardiovascular

Aortic valve disease with severe ventricular dysfunction: stentless valve for better recovery

^a Institute of Clinical Physiology, Cardiac Surgery Department, Massa, Italy
^b Cardiovascular Department, Ospedali Riuniti, Bergamo, Italy
^c Cardiac Surgery Department, Private Hospital Poliambulanza, Brescia, Italy

Accepted for publication July 8, 2002.

* Address reprint requests to Dr Bevilacqua, Ospedale G. Pasquinucci CNR-CREAS, Via Aurelia Sud, Località Montepepe 54100 Massa, Italy
e-mail: bevilacqua{at}ifc.cnr.it

	Abstract

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
BACKGROUND: Stentless bioprostheses and homografts show better hemodynamic profiles compared with conventional stented bioprostheses and mechanical valves. Few data are available on stentless aortic valve implantation for patients with severe left ventricular dysfunction. The aim of this retrospective study was to assess the potential benefits of stentless aortic valve implantation for patients undergoing isolated aortic valve replacement with left ventricular ejection fraction 35%.

METHODS: From November 1988 through March 2000, 53 patients (45 men and 8 women, aged 64.2 ± 15.2 years) with a LVEF 35% (mean EF, 28.7 ± 5.4%) underwent isolated, primary aortic valve replacement for chronic aortic valve disease. Twenty patients received stentless aortic valves and 33 patients received conventional stented bioprostheses and mechanical valves. Predictive factors for LVEF recovery at echocardiographic follow-up (36.2 ± 32.1 months) were analyzed by simple and multiple regression analysis.

RESULTS: There were no significant differences between groups in early and late mortality. Stentless aortic valve implantation required a longer aortic cross-clamp time (p = 0.037). The stentless aortic valve group showed a better LVEF recovery (p = 0.016). Stentless aortic valves had a larger indexed effective orifice area compared with conventional stented bioprostheses and mechanical valves (p < 0.0001). A smaller indexed effective orifice area (p = 0.0008), chronic obstructive pulmonary disease (p = 0.015), and implantation of a conventional stented bioprosthesis or mechanical valve (p = 0.016) were related to reduced LVEF recovery by univariate analysis. A larger indexed effective orifice area (p = 0.024) was an independent predictive factor for a better LVEF recovery by multivariate analysis.

CONCLUSIONS: Stentless aortic valve implantation for patients with severe left ventricular dysfunction, even if technically more demanding, is a safe procedure that warrants a larger indexed effective orifice area leading to an enhanced LVEF recovery.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Conservative therapy for patients with severe aortic valve disease and congestive heart failure carries a high mortality rate, with a 5 year-survival of 28% for aortic regurgitation [1] and a 2-year survival 10% for aortic stenosis [2]. Aortic valve replacement is the best therapeutic choice for this group of patients, even if left ventricular dysfunction (LVD) is associated with an increased operative risk [3, 4]. An incomplete relief of afterload overload by implanting an aortic prosthesis with a poor hemodynamic profile could jeopardize left ventricular ejection fraction (LVEF) recovery in these patients [5]. Stentless aortic valves (SAVs), (ie, homografts and stentless porcine bioprostheses) show a significant hemodynamic benefit [6, 7, 8] compared with conventional stented bioprostheses (CSBs) and mechanical valves (MVs). Nevertheless, few data are available on SAV implantation for patients with LVD [5, 9]. This retrospective study compared SAVs with CSBs and MVs in consecutive patients undergoing isolated aortic valve replacement with LVEF 35%.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Study population
Between November 1988 and March 2000, 1,571 patients underwent aortic valve replacement at Ospedali Riuniti in Bergamo, Ospedale G. Pasquinucci, National Research Council in Massa, Italy, and Private Hospital Poliambulanza in Brescia, Italy. Of this population, we identified all patients with LVEF 35% and severe aortic valve disease. Associated coronary artery disease, combined coronary bypass graft operation, and history or clinical evidence of previous acute myocardial infarction were considered exclusion criteria. Associated procedures on other heart valves or ascending aorta, previous cardiac operation, endocarditis, and aortic dissection were also exclusion criteria.

The medical charts of 53 consecutive patients (3.4%) who fulfilled the inclusion criteria were retrospectively reviewed and processed in a structured database, with consideration of preoperative clinical data, echocardiographic measurements, and operative and postoperative data.

Preoperative data
Demographics, comorbidities, and clinical preoperative data are described in Table 1. All patients received both transthoracic echocardiography and cardiac catheterization with selective coronary angiography before the operation.

Surgical procedure
Standard moderate hypothermic (28° to 32°C) cardiopulmonary bypass was used in all patients, with a conventional approach through a median sternotomy. Myocardial protection strategy varied according to surgeon preference. Continuous or intermittent hyperkalemic retrograde blood cardioplegia was administered in most cases (96.2%), whereas in others, cold antegrade St. Thomas II cardioplegia was used. All aortic homografts were harvested from brain dead multiorgan donors or heart transplant recipients, antibiotic sterilized, and cryopreserved at -80°C in liquid nitrogen. Aortic homografts and stentless porcine valves (Freestyle aortic root bioprosthesis; Medtronic Inc, Minneapolis, MN) were implanted with a free-hand technique in the subcoronary position, using single stitches for the proximal (annular) suture and three continuous suture for the distal (subcoronary) rim. Stented biologic valves (Carpentier-Edwards porcine, 2625; Edwards Lifesciences, Irvine, CA) were implanted in a supra-annular position using pledgetted mattress sutures. Mechanical heart valves (Carbomedics, R series, Sulzer-Carbomedics, Inc, Austin, TX; St Jude, standard, A101, St Jude Medical, Inc, St Paul, MN; Sorin, Bicarbon, Sorin-Biomedica Cardio SpA, Saluggia, VC, Italy) were implanted using interrupted simple sutures or pledgetted mattress sutures. In 47 patients (88.7%) the aortic annulus was measured at operation by means of a Hegar dilator. The aortic annulus diameter (Richard Martin Medizin-Technik GmbH, D-78532, Tuttlingen, Deutschland), divided for the patient’s body surface area, was defined as an indexed annulus diameter.

Postoperative and follow-up data
Operative death was defined as any death occurring within 30 days after the operation. Follow-up was conducted during a 2-month interval (ending in May 2000) by a visit or telephone interview, including a physical examination and an echocardiogram. Deaths attributed to acute myocardial infarction, congestive heart failure, and arrhythmia were considered as cardiovascular deaths, as were sudden deaths without any other specific cause, and deaths related to the prosthetic valve. Cause of death was established from hospital charts, autopsy reports (when available), or family physician interviews.

At follow-up, LVEF was evaluated by echocardiography with the volumetric method. Late recovery of left ventricular function was assessed comparing preoperative and follow-up values of LVEF. Implanted valve effective orifice area was evaluated by continuity equation. Indexed effective orifice area (iEOA) was defined as the ratio of the effective orifice area to the patient’s body surface area. Patient–prosthesis mismatch (PPM) was defined as iEOA 0.85 cm²/m² [1].

Statistical analysis
Categorical variables were compared between groups by the ² test for independence or by Fisher’s exact test when appropriate. For the comparison of continuous variables, independent sample t tests were performed when the variable distribution was found to be normal by the Kolmogorov–Smirnov test, otherwise a nonparametric Mann–Whitney U test was used. Group data were summarized by mean and standard deviation or by frequency percentages. Confidence limits (CL) of percentages were computed by means of a quadratic approximation to binomial distribution and continuity correction. The relationships, both univariate and multivariate, of potential predictive factors for LVEF recovery were evaluated by single and multiple linear regression analysis. Those variables with a univariate p value 0.1 or those of known biologic significance, but failing to meet the critical level, were submitted for consideration to multiple regression analysis. The variables included in the multiple regression analysis were age, gender, chronic obstructive pulmonary disease, preoperative New York Heart Association functional class, predominant valve lesion, preoperative LVEF, type of implanted prosthesis (SAVs or CSBs and MVs), iEOA, and patient–prosthesis mismatch (iEOA 0.85 cm²/m²). Overall survival was estimated by the Kaplan–Meier method and comparison between unadjusted overall group survival relative to baseline characteristics was assessed by the log rank test. Receiver operating characteristic curves were calculated to single out the best cutoff value of iEOA in predicting postoperative LVEF 50%. The accuracy of the test was assessed measuring the area under the receiver operating characteristic curve. Statistical significance was considered for a probability value 0.05. Statistical elaboration was conducted using SPSS software version 10.1 (SPSS Inc, Chicago, IL).

	Results

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Preoperative and operative data
Twenty patients (37.8%) received an SAV and 33 (62.2%) received a CSB or an MV (Table 2). The two groups were similar with most preoperative and operative characteristics. Preoperative renal dysfunction (serum creatinine > 2 mg/dL) was found to be more prevalent in the SAV group (p = 0.022). In the CSB and MV group there was a higher percentage of patients with chronic obstructive pulmonary disease (p = 0.056). Considering the negative prognostic impact of low gradient aortic stenosis [12, 13], 1 patient in the SAV group had a mean pressure gradient 30 mmHg compared with 3 patients in the CSB and MV group (p > 0.999).

Postoperative course, early, and late mortality
The 30-day mortality was 5.7% (3 of 53 patients) (CL90%: 1.75–14.58). All patients died of low cardiac-output syndrome and multiorgan failure. Postoperative complications are described in Table 3. There was no significant difference in the operative mortality (SAVs, 1 of 20 patients [5.0%] vs CSBs and MVs, 2 of 33 patients [6.1%]; p > 0.999) and postoperative course between the two groups. Mean follow-up (98% complete) was 36.2 ± 32.1 months. Only 1 patient living abroad was lost to follow-up. Two patients died during a median follow-up of 29.3 months (up to 136.5 months); one patient died of congestive heart failure; and the other patient’s death was not cardiac related. The 3-year overall survival was 88.3% (CL90%: 78.1–95.5). The implanted prosthesis type showed no significant influence on the 3-year overall survival (SAVs, 86.4%; CL90%: 76.23–93.36 vs CSBs and MVs, 90.5%; CL90%: 80.71–95.96; p = 0.989) (Fig 1).

View larger version (18K): [in this window] [in a new window]   Fig 1. Kaplan-Meier survival curve stratified for the type of implanted prosthesis: stentless aortic valves (SAVs) versus conventional stented bioprostheses and mechanical valves (CSBs/MVs).

Univariate analysis identified three predictive factors for a reduced LVEF recovery: (1) chronic obstructive pulmonary disease (p = 0.014), (2) CSB and MV implantations (p = 0.016), and (3) a smaller iEOA (p = 0.0008) (Table 5). The predominant valve lesion was not correlated to LVEF recovery at univariate analysis (p = 0.849). A larger iEOA (p = 0.024) was the sole independent predictive factor for a better LVEF recovery by multivariate analysis (Table 5). The best threshold value of iEOA for predicting a follow-up LVEF 50% was 0.942 cm²/m² (receiver operating characteristic area, 0.735; CL90%: 0.627–0.821; p = 0.002) (Fig 2). This cutoff value showed a sensitivity of 88.0% and a specificity of 59.1%.

View larger version (14K): [in this window] [in a new window]   Fig 2. Receiver operating characteristic curve for the prediction of follow-up left ventricular ejection fraction 50%. Rhomboid points () show indexed effective orifice area (iEOA) by steps of 0.10 cm2/m2. The square point () shows the best predictive value of iEOA (cm2/m2). *p = 0.002.

	Comment

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Aortic valve replacement appears to be the gold standard for the treatment of patients with aortic valve disease and severe left ventricular dysfunction. Previous reports have demonstrated that SAVs show a better hemodynamic performance that implies a better outcome in terms of left ventricular mass reduction and LVEF recovery [6, 7, 8, 14]. Nevertheless, most of the reported series of patients with severe left ventricular dysfunction show a very small number of patients receiving an aortic homograft or a stentless bioprosthesis [4, 12, 13]. This underuse actually comes from a more demanding surgical technique with longer operative times and potentially higher risks of postoperative valve dysfunction. It is a common opinion that the best procedure for these ill patients is the quickest one. Therefore, this conception has led to a relative contraindication of stentless valve implantation for patients with severe LVD [15].

Early outcomes
The present study demonstrates that an appropriate perioperative management does not actually preclude the use of stentless aortic valve for these high-risk patients; in our series there was no difference in the 30-day mortality and the hospital morbidity between the two groups. A careful myocardial protection strategy permits to break down the potential risk of a slightly longer aortic cross-clamp time, wiping out the unconscious fear that a quick operation is the best way to improve the operative outcome. Furthermore, a correct implantation technique for SAVs actually avoids the occurrence of significant early regurgitation; in our series only 3 patients showed a moderate regurgitation caused by the late degeneration of aortic homografts. The exclusion of patients with associated coronary artery disease and the small number of patients with low gradient aortic stenosis can explain the better operative mortality of this series (5.3%) compared with previous reports (9% to 21%) [12, 13].

Left ventricular recovery
The patient selection was made to avoid any confounding factor related to ischemic heart disease, (ie, jeopardized myocardial viability and completeness of revascularization) that could influence LVEF recovery. In the present report, aortic homografts and stentless bioprostheses showed a better hemodynamic profile with a significant reduction of PPM incidence. Although contrasting data are reported on the clinical impact of these favorable characteristics [16, 17], in our population the sole independent predictor of an enhanced LVEF recovery at late follow-up was a larger iEOA, even excluding all the patients with iEOA 0.85 cm²/m² from the analysis. Furthermore, the better threshold of iEOA for predicting a follow-up LVEF 50% was 0.94 cm²/m². This means that the larger iEOA, the better the LVEF recovery, and even a mild mismatch, can jeopardize the functional recovery of bad ventricles.

Long-term survival
As previously reported by other authors [16, 17], the kind of implanted prosthesis in the present study did not show any significant influence on 3-year survival. On the contrary, other series that enrolled a larger population of patients with a longer follow-up reported a survival benefit related to SAV implantation [18, 19], also for patients with CHF [20].

Limitations of the study
In this retrospective study, data about diastolic left ventricular function, ventricular mass, or adjunctive data for better defining systolic function and ventricular geometry, unfortunately were not available for a percentage of patients large enough to have a statistical value; this lack of data must be considered when interpreting the results. Furthermore, most of SAVs were aortic homografts, and all CSBs were porcine Carpentier-Edwards prostheses. Thus these results should be cautiously extrapolated to stentless porcine valves and pericardial stented bioprostheses, which a recent randomized study showed to be comparable with regard to hemodynamic performance and mass regression at 1-year follow-up [21][11].

Conclusions
Isolated aortic valve replacement with SAVs is a safe procedure for patients with severe left ventricular dysfunction, showing an early and mid-term outcome comparable with CSB and MV. Stentless aortic valve implantation allows the largest effective orifice area compatible with the patient’s annulus to be obtained, and actually reduces the occurrence of PPM. A larger iEOA is independently related with an enhanced LVEF recovery at follow-up. Larger prospective and randomized studies are needed to completely assess the benefits and potential limits of SAV implantation for patients with severe left ventricular dysfunction.

	Acknowledgments

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
We are very grateful to Lorraine Abbey and Susan Gwynne for their assistance in manuscript editing.

	References

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 

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