Are outcomes of thoracoabdominal aortic aneurysm repair different in men versus women? A propensity-matched comparison

The intersection of community socioeconomic factors with gender on outcomes after thoracic aortic surgery

OBJECTIVE

We evaluated the relationship among community socioeconomic factors (poverty, income, and education), gender, and outcomes in patients who underwent ascending aortic, root, and arch surgery.

METHODS

For 2634 consecutive patients, we associated patients' ZIP codes with community socioeconomic factors. The composite adverse outcome comprised death, persistent neurological injury, and renal failure necessitating dialysis at discharge. Multivariable analysis and Kaplan-Meier survival curves were used. Men and women from the full cohort and from the elective patients were propensity matched.

RESULTS

Median follow-up was 3.6 years (interquartile range, 1.2-9.3). Men lived in areas characterized by less poverty (P = .03), higher household income (P = .01), and more education (P = .02) than women; likewise, in the elective cohort, all community socioeconomic factors favored men (P ≤ .009). Female gender predicted composite adverse outcome (P = .006). In the propensity-matched women and men (820 pairs), the composite adverse outcome rates were 14.2% and 11%, respectively (P = .06). In 583 propensity-matched pairs of elective patients, men had less composite adverse outcome (P = .02), operative mortality (P = .04), and renal (P = .02) and respiratory failure (P = .0006). The 5- and 10-year survivals for these men and women were 74.2% versus 71.4% and 50.2% versus 48.2%, respectively (P = .06). All community socioeconomic factors in both propensity-matched groups nonsignificantly favored men.

CONCLUSIONS

This study is among the first to examine the association among community socioeconomic factors, gender, and outcomes in patients who undergo proximal aortic surgery. Female gender predicted a composite adverse outcome. In the elective patients, most adverse outcomes were significantly less in men. In the propensity-matched patients, all community socioeconomic factors favored men, although not significantly. Larger studies with patient-level socioeconomic information are needed.

Presentation and outcomes of thoracic and thoracoabdominal aortic aneurysms in females, existing gaps, and future directions: A descriptive review

Thoracic and thoracoabdominal aortic aneurysms are more common in men. Yet, females often have worse outcomes, fewer interventions, and lower treatment rates. Females have also benefited less from the research and treatment of those diseases than men. Understanding sex- and sex-specific differences in thoracic and thoracoabdominal aortic aneurysms can improve care delivery, reduce disparities, and optimize outcomes for females with thoracic aortic aneurysms and thoracoabdominal aortic aneurysms. The authors reviewed the literature on the presentation and outcomes of thoracic and thoracoabdominal aortic aneurysms in females, discussing the existing gaps and future directions to address them.

2022 ACC/AHA guideline for the diagnosis and management of aortic disease: A report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

Comparative Study of Male and Female Patients Undergoing Frozen Elephant Trunk Total Arch Replacement

BACKGROUND

Our aim was to investigate outcomes and long-term survival in male and female patients after frozen elephant trunk (FET) total arch replacement.

METHODS

Between March 2013 and January 2023, 362 patients underwent aortic arch replacement via the FET technique. We compared patient characteristics and intra- and postoperative data between male and female patients.

RESULTS

Male patients were significantly younger (p = 0.012) but revealed a higher incidence of coronary artery disease (p = 0.008) and preoperative dialysis (p = 0.017). More male patients presented with type A aortic dissections (p = 0.042) while more female patients had aortic aneurysms (p = 0.025). The aortic root was replaced in significantly more male patients (p = 0.013), resulting in significantly longer cardiopulmonary bypass duration (p < 0.001) and operative times (p < 0.001). There were no statistically significant differences in postoperative outcome parameters including in-hospital mortality (p = 0.346). However, new in-stent thrombus formation was significantly more frequent in female patients (p = 0.002). Age in years (odds ratio (OR): 1.026, p = 0.049), an acute pathology (OR: 1.941, p = 0.031) and preoperative dialyses (OR: 3.499, p = 0.010) were predictive for long-term mortality in our Cox regression model, sex (p = 0.466) was not. There was no statistical difference in overall survival (log rank: p = 0.425).

CONCLUSIONS

Female patients are older but reveal fewer cardiovascular risk factors; aneurysms are more common in female than male patients. As female patients undergo concomitant surgical procedures less often, their operative times are shorter. While survival and outcomes were similar, female patients suffered from postoperative new in-stent thrombus formation significantly more often.

Sex Differences in Thoracic Aortic Disease and Dissection: JACC Review Topic of the Week

Despite its higher prevalence among men, women with thoracic aortic aneurysm and dissection (TAAD) have lower rates of treatment and surgical intervention and often have worse outcomes. A growing number of women with TAAD also desire pregnancy, which can be associated with an increased risk of aortic complications. Understanding sex-specific differences in TAAD has the potential to improve care delivery, reduce disparities in treatment, and optimize outcomes for women with TAAD.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate. Structure: Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease" provides recommendations to guide clinicians in the diagnosis, genetic evaluation and family screening, medical therapy, endovascular and surgical treatment, and long-term surveillance of patients with aortic disease across its multiple clinical presentation subsets (ie, asymptomatic, stable symptomatic, and acute aortic syndromes).

METHODS

A comprehensive literature search was conducted from January 2021 to April 2021, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, CINHL Complete, and other selected databases relevant to this guideline. Additional relevant studies, published through June 2022 during the guideline writing process, were also considered by the writing committee, where appropriate.

STRUCTURE

Recommendations from previously published AHA/ACC guidelines on thoracic aortic disease, peripheral artery disease, and bicuspid aortic valve disease have been updated with new evidence to guide clinicians. In addition, new recommendations addressing comprehensive care for patients with aortic disease have been developed. There is added emphasis on the role of shared decision making, especially in the management of patients with aortic disease both before and during pregnancy. The is also an increased emphasis on the importance of institutional interventional volume and multidisciplinary aortic team expertise in the care of patients with aortic disease.

Cardiac Surgery in Women in the Current Era: What Are the Gaps in Care?

Cardiovascular disease remains the leading cause of morbidity and mortality for women in United States and worldwide. One in 3 women dies from cardiovascular disease, and 45% of women >20 years old have some form of CVD. Historically, women have had higher morbidity and mortality after cardiac surgery. Sex influences pathogenesis, pathophysiology, presentation, postoperative complications, surgical outcomes, and survival. This review summarizes current cardiovascular surgery outcomes as they pertain to women. Specifically, this article seeks to address whether sex disparities in research, surgical referral, and outcomes still exist and to provide strategies to close these gaps. In addition, with the growing population of women of reproductive age with cardiovascular disease and cardiovascular risk factors, indications for cardiac surgery arise in pregnant women. The current review will also address the unique issues associated with this special population.

Sex Differences in Inflammation During Venous Remodeling of Arteriovenous Fistulae

Vascular disorders frequently have differing clinical presentations among women and men. Sex differences exist in vascular access for hemodialysis; women have reduced rates of arteriovenous fistula (AVF) maturation as well as fistula utilization compared with men. Inflammation is increasingly implicated in both clinical studies and animal models as a potent mechanism driving AVF maturation, especially in vessel dilation and wall thickening, that allows venous remodeling to the fistula environment to support hemodialysis. Sex differences have long been recognized in arterial remodeling and diseases, with men having increased cardiovascular events compared with pre-menopausal women. Many of these arterial diseases are driven by inflammation that is similar to the inflammation during AVF maturation. Improved understanding of sex differences in inflammation during vascular remodeling may suggest sex-specific vascular therapies to improve AVF success.

Effect of sarcopenia on survival and spinal cord deficit outcomes after thoracoabdominal aortic aneurysm repair in patients 60 years of age and older

OBJECTIVE

Sarcopenia (core muscle loss) has been used as a surrogate marker of frailty. We investigated whether sarcopenia would adversely affect survival after thoracoabdominal aortic aneurysm repair.

METHODS

We retrospectively reviewed prospectively collected data from patients aged 60 years or older who underwent thoracoabdominal aortic aneurysm repairs from 2006 to 2016. Imaging was reviewed by 2 radiologists blinded to clinical outcomes. The total psoas index was derived from total psoas muscle cross-sectional area (cm²) at the mid-L4 level, normalized for height (m²). Patients were divided by sex-specific total psoas index values into sarcopenia (lower third) and nonsarcopenia (upper two-thirds) groups. Multivariable modeling identified operative mortality and spinal cord injury predictors. Unadjusted and adjusted survival curves were analyzed.

RESULTS

Of 392 patients identified, those with sarcopenia (n = 131) were older than nonsarcopenic patients (n = 261) (70.0 years vs 68.0 years; P = .02) and more frequently presented with aortic rupture or required urgent/emergency operations. Operative mortality was comparable (sarcopenia 13.7% vs nonsarcopenia 10.0%; P = .3); sarcopenia was not associated with operative mortality in the multivariable model (odds ratio, 1.40; 95% confidence interval, 0.73-2.77; P = .3). Sarcopenic patients experienced more frequent delayed (13.0% vs 4.6%; P = .005) and persistent (10.7% vs 3.4%; P = .008) paraplegia. Sarcopenia independently predicted delayed paraplegia (odds ratio, 3.17; 95% confidence interval, 1.42-7.08; P = .005) and persistent paraplegia (odds ratio, 3.29; 95% confidence interval, 1.33-8.13; P = .01) in the multivariable model. Adjusted for preoperative/operative covariates, midterm survival was similar for sarcopenic and nonsarcopenic patients (P = .3).

CONCLUSIONS

Sarcopenia did not influence early mortality or midterm survival after thoracoabdominal aortic aneurysm repair but was associated with greater risk for delayed and persistent paraplegia.

Sex Differences in Ascending Aortic and Arch Surgery: A Propensity-matched Comparison of 1153 Pairs

BACKGROUND

We investigated the relationship of sex with clinical outcomes after proximal aortic (ascending and arch) operations, and whether sex-specific preoperative factors are associated with mortality.

METHODS

Of 3745 patients who underwent elective, urgent, and emergency proximal aortic operations over a 20-year period, 1153 pairs of men and women were propensity-matched, and their early and long-term outcomes were compared. Kaplan-Meier survival analysis was used to estimate late survival.

RESULTS

Women and men had similar operative mortality (9.1% vs 8.8%, P=0.8), stroke (5.7% vs 5.6%, P=0.9), and renal failure rates (7.0% vs 6.6%, P=0.7). Thirty-day mortality was 7.5% versus 5.6% (P=0.06), respectively. Results were less favorable for women than for men regarding respiratory failure (34.3% vs 29.2%, P=0.008) and intensive care unit length of stay (9.11±11.9 vs 7.87±12.48 days; P=0.023). Long-term survival was not significantly different between women and men: 66.3% (95%CI 62.8-69.5) versus 67.1% (95%CI 63.6-70.4) at 5 years, and 45.9% (95%CI 41.76-50.0) versus 46.2% (95%CI 41.7-50.6) at 10 years (P=0.4). Preoperative factors including diabetes, prior stroke, prior renal insufficiency, and peripheral vascular disease were associated with operative mortality in men, whereas chronic obstructive pulmonary disease was the main risk factor in women.

CONCLUSIONS

No differences were seen between the sexes in life-changing adverse outcomes after ascending aortic and arch procedures, although specific preoperative variables were associated with specific adverse events. Recognizing differences in preoperative risk factors for mortality between the sexes may facilitate targeted preoperative assessment, preparation, and counseling.

Sex-related outcomes after fenestrated-branched endovascular aneurysm repair for thoracoabdominal aortic aneurysms in the U.S. Fenestrated and Branched Aortic Research Consortium

OBJECTIVE

Fenestrated-branched endovascular aneurysm repair (FBEVAR) has expanded the treatment of patients with thoracoabdominal aortic aneurysms (TAAAs). Previous studies have demonstrated that women are less likely to be treated with standard infrarenal endovascular aneurysm repair because of anatomic ineligibility and experience greater mortality after both infrarenal and thoracic aortic aneurysm repair. The purpose of the present study was to describe the sex-related outcomes after FBEVAR for treatment of TAAAs.

METHODS

The data from 886 patients with extent I to IV TAAAs (excluding pararenal or juxtarenal aneurysms), enrolled in eight prospective, physician-sponsored, investigational device exemption studies from 2013 to 2019, were analyzed. All data were collected prospectively, audited and adjudicated by clinical events committees and/or data safety monitoring boards, and subject to Food and Drug Administration oversight. All the patients had been treated with Cook-manufactured patient-specific FBEVAR devices or the Cook t-Branch off-the-shelf device (Cook Medical, Brisbane, Australia).

RESULTS

Of the 886 patients who underwent FBEVAR, 288 (33%) were women. The women had more extensive aneurysms and a greater prevalence of diabetes (33% vs 26%; P = .043) but a lower prevalence of coronary artery disease (33% vs 52%; P < .0001) and previous infrarenal endovascular aneurysm repair (7.6% vs 16%; P < .001). The women had required a longer operative time from incision to surgery end (5.0 ± 1.8 hours vs 4.6 ± 1.7 hours; P < .001), experienced lower technical success (93% vs 98%; P = .002), and were less likely to be discharged to home (72% vs 83%; P = .009). Despite the smaller access vessels, the women did not have an increased incidence of access site complications. Also, the 30-day outcomes were broadly similar between the sexes. At 1 year, no differences were found between the women and men in freedom from type I or III endoleak (91.4% vs 92.0%; P = .64), freedom from reintervention (81.7% vs 85.3%; P = .10), target vessel instability (87.5% vs 89.2%; P = .31), and survival (89.6% vs 91.7%; P = .26). The women had a greater incidence of postoperative sac expansion (12% vs 6.5%; P = .006). Multivariable modeling adjusted for age, aneurysm extent, aneurysm size, urgent procedure, and renal function showed that patient sex was not an independent predictor of survival (hazard ratio, 0.83; 95% confidence interval, 0.50-1.37; P = .46).

CONCLUSIONS

Women undergoing FBEVAR demonstrated metrics of increased complexity and had a lower level of technical success, especially those with extensive aneurysms. Compared with the men, the women had similar 30-day mortality and 1-year outcomes, with the exception of an increased incidence of sac expansion. These data have demonstrated that FBEVAR is safe and effective for women and men but that further efforts to improve outcome parity are indicated.

US women in thoracic surgery: reflections on the past and opportunities for the future

Herein, we examine the state of women in thoracic surgery from the United States (US) perspective in terms of our past, present, and opportunities for the future. We explore the achievements of the first three women certified in thoracic surgery in 1961 and describe the progress made resulting in the current state. Women constitute slightly more than 50% of all medical students in the US, yet women remain underrepresented in thoracic surgery. The disparity is most notable for female representation in senior academic leadership positions, reflecting stagnation in progress. The lack of gender equity has important implications for projected workforce shortages and patient safety in cardiothoracic surgery. Recent organized efforts in scholarships and leadership training, as well as increasing awareness and mentorship, may herald progress on the horizon. Ultimately, however, engagement of leadership and top-down change are needed to achieve equity and, thereby, to improve patient health and satisfaction.

Female Sex Portends Worse Long-Term Survival after Open Type I-III Thoracoabdominal Aneurysm Repair

BACKGROUND

Although outcomes after infrarenal abdominal aortic aneurysm surgery are worse in females, sex-specific differences in outcomes after open thoracoabdominal aortic aneurysm (TAAA) repair are less clear. The goal of this study was to identify sex-based disparities in short- and long-term outcomes after open type I-III TAAA surgery.

METHODS

All open type I-III TAAA repairs performed from 1987 to 2015 were evaluated using an institutional database. Charts were retrospectively evaluated for perioperative outcomes: major adverse events (MAEs), in-hospital death, and long-term survival. Univariate analysis was performed using the Fisher's exact test for categorical variables and the Wilcoxon rank-sum test for continuous variables. Logistic regression was used for in-hospital end points; survival analyses were performed with Cox proportional hazards modeling and Kaplan-Meier techniques. Sensitivity analyses were performed for relevant multivariable models, one with ruptures removed and another evaluating only repairs performed before 2006 to account for any selection bias due to wider use of complex endovascular technology.

RESULTS

Five-hundred sixteen patients underwent open type I-III TAAA repair during the study period. Females accounted for 54.3% (n = 280) of the cohort. Women were older, less likely to have a chronic dissection etiology, more likely to present with a symptomatic/ruptured lesion, and had a lower admission creatinine than men. Perioperative death occurred in 23 men (9.8%) and 19 women (6.8%) (P = 0.26); 133 women (47.3%) and 116 men (49.2%) suffered an MAE (P = 0.72). Multivariable analyses revealed no sex-based difference in perioperative death (Female sex adjusted odds ratio (AOR): 0.72, 95% confidence interval (CI): 0.4-1.4, P = 0.34) or MAE (AOR: 1.0 CI: 0.7-1.5, P = 0.82). Unadjusted survival at five years was 50% for women and 67% for men (log-rank P < 0.001). Female sex was an independent predictor of decreased survival (hazard ratio (HR): 1.5 95% CI: 1.2-1.9, P = 0.001) when adjusted for age, aneurysm extent, creatinine, chronic obstructive pulmonary disease, and ruptures. After removing all ruptures, female sex remained nonpredictive of perioperative death (AOR: 1.1, 95% CI 0.5-2.5, P = 0.75) or MAE (AOR: 1.2, CI: 0.8-1.9, P = 0.31) and predictive of decreased long-term survival (HR: 1.5, 95% CI: 1.2-2.0, P = 0.001).

CONCLUSIONS

Those undergoing open type I-III TAAA repair have similar rates of perioperative mortality and MAEs, regardless of sex. However, female sex is an independent risk factor for decreased long-term survival.

Sex-related outcomes after open type IV thoracoabdominal aortic aneurysm repair

OBJECTIVE

Although outcomes after infrarenal abdominal aortic aneurysm surgery are worse in women, sex-specific differences in outcomes after open type IV thoracoabdominal aortic aneurysm (TAAA) surgery are undefined. The goal of this study was to define sex-based disparities in short- and long-term outcomes after open type IV TAAA surgery.

METHODS

All open type IV TAAA repairs performed during 27 years were evaluated using a single institutional database. Charts were retrospectively evaluated for major adverse events (in-hospital death, other major in-hospital complication) and long-term complications (graft- and aortic-related events and death). Univariate analyses were performed using the Fisher's exact test for categorical variables and Wilcoxon rank-sum testing for continuous variables. Logistic multivariable regression was used for the in-hospital end points death and major complication, and survival analyses were performed with Cox proportional hazards modeling and Kaplan-Meier techniques.

RESULTS

During the 27-year study period, 234 patients had an open type IV TAAA repair; 85 were female and 149 were male. There were 26 (17.5%) men and 16 (18.8%) women who suffered a major in-hospital complication/death. There were eight (3.4%) in-hospital deaths, all occurring in men. Unadjusted survival at 5 years was 67.9% for women and 58.4% for men. Multivariable analyses revealed no sex-based difference in combined major in-hospital events and death (female: odds ratio [OR], 1.8; confidence interval [CI], 0.83-4.0; P = .13) or any complication (OR, 1.0; CI, 0.55-1.8; P = .99). However, women were less likely than men to be discharged to home (OR, 0.28; CI, 0.13-0.60; P = .001) and had decreased survival compared with men after discharge (hazard ratio, 2.1; CI, 1.2-3.5; P = .008).

CONCLUSIONS

No sex-based differences were found for the in-hospital outcomes of death or major complication after open type IV TAAA repair. However, women are less likely than men to be discharged home. Among those who survive the index operation, female sex portends decreased survival following discharge after repair.

Gender differences in outcomes after aortic aneurysm surgery should foster further research to improve screening and prevention programmes

Background Gender-related biases in outcomes after thoracic aortic surgery are an important factor to consider in the prevention of potential complications related to aortic diseases and in the analysis of surgical results. Methods The aim of this study is to provide an up-to-date review of gender-related differences in the epidemiology, specific risk factors, outcome, and screening and prevention programmes in aortic aneurysms. Results Female patients affected by aortic disease still have worse outcomes and higher early and late mortality than men. It is difficult to plan new specific strategies to improve outcomes in women undergoing major aortic surgery, given that the true explanations for their poorer outcomes are as yet not clearly identified. Some authors recommend further investigation of hormonal or molecular explanations for the sex differences in aortic disease. Others stress the need for quality improvement projects to quantify the preoperative risk in high-risk populations using non-invasive tests such as cardiopulmonary exercise testing. Conclusions The treatment of patients classified as high risk could thus be optimised before surgery becomes necessary by means of numerous strategies, such as the administration of high-dose statin therapy, antiplatelet treatment, optimal control of hypertension, lifestyle improvement with smoking cessation, weight loss and careful control of diabetes. Future efforts are needed to understand better the gender differences in the diagnosis, management and outcome of aortic aneurysm disease, and for appropriate and modern management of female patients.

Hybrid thoracoabdominal aortic aneurysm repair: is the future here?

Open surgical repair has been the gold standard for thoracoabdominal aortic aneurysm (TAAA) repair for more than 6 decades, but 2 additional options have emerged: total endovascular TAAA repair and a hybrid approach that combines open and endovascular repair. Despite the optimism for an endovascular approach, long-term results for these repairs are still lacking. Some of the issues with this emerging technology include the risk of paraplegia after extensive endovascular repair, the need for multiple reinterventions, continuous stent-graft surveillance, endograft branch stenosis, as well as the significant learning curve. Interest in a hybrid approach has resurged despite the non-superior results compared to open TAAA. Commonly, the focus of the hybrid approach is now on performing a less extensive open TAAA repair, which is then extended with a stent-graft or vice versa. Moreover, this approach is now often performed in two stages in an effort to decrease the associated spinal cord ischemia. Open surgical repair after endovascular aortic repair is increasingly being performed to address serious complications, such as infection or fistula, that cannot be repaired by further endovascular intervention. As with any new technology, there will be an increase in the number of procedure-related complications and a decrease in the number of surgeons who can perform the traditional open operation with good results.