Stress echocardiography in regurgitant valve disease

Manual zur Indikation und Durchführung spezieller echokardiographischer Anwendungen

Das zweite Manual zur Indikation und Durchführung der Echokardiographie bezieht sich auf spezifische Anwendungen der Echokardiographie und besondere Fragestellungen bei speziellen Patientengruppen. Dabei stehen v. a. praktische Aspekte im Vordergrund. Methodisch etabliert sind die transösophageale Echokardiographie, die Stressechokardiographie und die Kontrastechokardiographie. Bei nahezu allen echokardiographischen Untersuchungen spielen aktuell 3‑D-Echokardiographie und Deformationsbildgebung eine Rolle. Das gesamte Spektrum der echokardiographischen Möglichkeiten wird derzeit in Notfall- und Intensivmedizin, bei der Überwachung und Führung von Katheterinterventionen, bei strukturellen Herzerkrankungen, bei herzchirurgischen Operationen, bei der Nachsorge von kardialen Unterstützungssystemen, bei kongenitalen Vitien im Erwachsenenalter und bei der Versorgung von hochinfektiösen Patienten in Pandemiezeiten angewandt. Die diagnostischen Fortschritte der konventionellen und modernen echokardiographischen Anwendungen stehen im Fokus dieses Manuals. Die 3‑D-Echokardiographie zur Charakterisierung der kardialen Morphologie und die Deformationsbildgebung zur Objektivierung der kardialen Funktion sind bei vielen Indikationen im klinischen Alltag etabliert. Die Stressechokardiographie zur Ischämie‑, Vitalitäts- und Vitiendiagnostik, die Bestimmung der koronaren Flussreserve und die Kontrastechokardiographie bei der linksventrikulären Wandbewegungsanalyse und kardialen Tumordetektion finden zunehmend klinische Anwendung. Wie für die konventionelle Echokardiographie im ersten Manual der Echokardiographie 2009 beschrieben, erfordert der Einsatz moderner echokardiographischer Verfahren die standardisierte Dokumentation und Akquisition bestimmter Bildsequenzen bei optimierter Geräteeinstellung, da korrekte und reproduzierbare Auswertungen nur bei guter Bildqualität möglich sind.

Multimodality imaging in valvular heart disease: how to use state-of-the-art technology in daily practice

Our understanding of the complexities of valvular heart disease (VHD) has evolved in recent years, primarily because of the increased use of multimodality imaging (MMI). Whilst echocardiography remains the primary imaging technique, the contemporary evaluation of patients with VHD requires comprehensive analysis of the mechanism of valvular dysfunction, accurate quantification of severity, and active exclusion extravalvular consequences. Furthermore, advances in surgical and percutaneous therapies have driven the need for meticulous multimodality imaging to aid in patient and procedural selection. Fundamental decision-making regarding whom, when, and how to treat patients with VHD has become more complex. There has been rapid technological advancement in MMI; many techniques are now available in routine clinical practice, and their integration into has the potential to truly individualize management strategies. This review provides an overview of the current evidence for the use of MMI in VHD, and how various techniques within each modality can be used practically to answer clinical conundrums.

Clinical implications of exercise-induced regional wall motion abnormalities in significant aortic regurgitation

BACKGROUND

Significant aortic regurgitation (AR) is sometimes accompanied by regional wall motion abnormalities (RWMA) during exercise stress echocardiography. The aim of this study was to estimate the association between RWMA after exercise and in the presence of significant AR in patients with coronary artery disease (CAD) or volume overload and to predict the eventual need for aortic valve replacement (AVR).

METHODS AND RESULTS

We retrospectively reviewed 182 patients with significant AR who underwent exercise echocardiography. In addition, we investigated patients with AR who underwent coronary angiography (CAG) or coronary computed tomography angiography (CCTA) and were diagnosed with CAD. The presence of RWMA after exercise was defined as newly developed RWMA after exercise and included all changes in wall motion. Patients were divided into two groups according to the presence of RWMA after exercise: the RWMA group (n = 42) and non-RWMA group (n = 140). In the RWMA group, 31 patients (73.8%) underwent coronary artery evaluation by CAG or CCTA. Only two patients in the RWMA group were diagnosed with current CAD and underwent percutaneous coronary intervention. Patients with RWMA were older (61.6 ± 10.8 vs 52.0 ± 13.7 years, P < .001), had more severe AR (54.8% vs 32.9%), and underwent AVR more frequently (40.5% vs 14.3%, P = .001) than patients without RWMA. METs (odds ratio [OR], 0.796; P = .019), difference between rest and postexercise left ventricular end-diastolic volume (OR, 0.967; P = .001), and the difference between pre- and postexercise left ventricular end-systolic volume (OR, 1.113; P < .001) were identified as independent factors associated with RWMA after exercise according to multivariable logistic regression analysis. The majority of wall motion changes were seen in the lateral and inferior segments, and the locations of wall motion changes were relatively consistent with the direction of the AR jet. The relationship between RWMA after exercise and time to AVR was investigated by simple linear regression (hazard ratio [HR], 3.402; P < .001). After adjusting for baseline parameters of diastolic blood pressure, left ventricular end-systolic dimension (LVESD), aorta size, deceleration time, and METs, the presence of RWMA after exercise was not predictive of time to AVR (HR, 1.106; P = .81). On the other hand, without forcible entry of RWMA after exercise, LVESD (HR, 1.119; P < .001) and METs (HR, 0.828; P = .006) independently predicted the eventual need for AVR as an outcome.

CONCLUSION

The degree of change in wall motion from rest to exercise in those with significant AR was not correlated with CAD, but was correlated with the severity of volume overload and exercise-induced preload changes, as well as the direction of the AR jet. In addition, RWMA after exercise had no role in predicting the need for AVR.

Valve Disease in Heart Failure: Secondary but Not Irrelevant

Secondary regurgitation caused by the remodeling and dysfunction of the left or right heart chamber may complicate heart failure, worsening both symptoms and prognosis. Outcome studies have shown that patients' prognosis worsened as the severity of secondary regurgitation increases. Imaging and more specifically echocardiography plays a central role for diagnosis and serial assessment of secondary regurgitation as well as for timing the intervention and guiding the procedure.

Can stress echocardiography identify patients who will benefit from percutaneous mitral valve repair?

The aim of the current study was to investigate whether stress echocardiography improves selection of patients who might have clinical benefit from percutaneous mitral valve repair with the MitraClip. In total, 39 patients selected for MitraClip implantation underwent preprocedural low-dose stress (dobutamine or handgrip) echocardiography from which stroke volume, ejection fraction and MR grade were measured. Outcome after MitraClip implantation was determined by New York Heart Association classification and Quality of Life questionnaires. Clinical benefit from MitraClip treatment was defined as survival and NYHA class I–II at 6 months follow-up. In total, 36 patients with a technically successful procedure were included in the analysis (mean age 79 ± 8 years, 47% male, 50% functional MR). Clinical benefit was achieved in 18 patients. All seven patients with MR decreasing during stress remained in NYHA III–IV or died within 6 months, while 62% (18 out of 29) of the patients with stable or increased MR during stress had clinical benefit (p = 0.008). Significant increase in Quality of Life on 4/8 subscales of the RAND Short Form-36 questionnaire was observed: Physical Functioning (p < 0.001), Social Functioning (p < 0.001), Mental Health (p = 0.022) and Vitality (p = 0.026) was seen in patients with an increase in stroke volume during stress echocardiography. Patients with a decreased MR during preprocedural stress echocardiography remained more symptomatic than patients with a stable or increased MR during stress. Stress echocardiography may support patient selection for percutaneous mitral valve repair.

Stress ECHO beyond coronary artery disease. Is it the holy grail of cardiovascular imaging?

Stress echocardiography (SE) is a very useful method in clinical practice, because it offers important information of both the patient's functional status and hemodynamic changes during stress. Therefore, SE provides strong diagnostic and prognostic data in a wide spectrum of cardiovascular diseases. This review summarizes the clinical applications of SE in conditions beyond coronary artery disease (CAD) and highlights practical recommendations and key issues for each condition that need further investigation. SE is an established method for the evaluation of symptomatic and asymptomatic patients with valvular heart disease (VHD) and cardiomyopathies, and provides important information regarding prognosis and management of patients with congenital heart disease, pulmonary hypertension or diastolic dysfunction. Moreover, when one or multiple VHD and cardiomyopathy or CAD coexist in one patient, SE is a very useful clinical tool for the evaluation of etiology and symptomatology.

Practical guidance for the implementation of stress echocardiography

Exercise stress testing has been widely undertaken for the diagnosis of heart diseases. The accurate assessment of clinical conditions can be conducted by comparing the findings obtained from the results of stress echocardiography with the changes in the blood/heart rate and electrocardiograms. Numerous overseas studies have reported the utility of stress echocardiography in diagnosing myocardial ischemia; in Japan, the use of this modality for this purpose was included in the national health insurance reimbursable list in 2012. Nevertheless, stress echocardiography is far from being a widespread practice in Japan. This might be due to insufficient equipment (e.g., ergometers, space for test implementation) at each medical institution, shortage of technicians and sonographers who are well experienced and who are responsible for obtaining images during stress testing. The other possible reasons include the limited evidence available in Japan and the lack of a standardized testing protocol. Further dissemination of the practice of exercise stress echocardiography in this country is deemed necessary to establish satisfactory evidence for the use of stress echocardiography in the Japanese population. To this end, efforts are underway to develop a standardized protocol and report format to be adopted throughout Japan. We here present a guideline created by the Guideline Development Committee of the Japanese Society of Echocardiography that describes safe and effective stress echocardiography protocols and report formats. The readers are encouraged to perform exercise stress echocardiography using the proposed template for consensus document and report attached to this guideline.

Stressing the Cardiopulmonary Vascular System: The Role of Echocardiography

The cardiopulmonary vascular system represents a key determinant of prognosis in several cardiorespiratory diseases. Although right heart catheterization is considered the gold standard for assessing pulmonary hemodynamics, a comprehensive noninvasive evaluation including left and right ventricular reserve and function and cardiopulmonary interactions remains highly attractive. Stress echocardiography is crucial in the evaluation of many cardiac conditions, typically coronary artery disease but also heart failure and valvular heart disease. In stress echocardiographic applications beyond coronary artery disease, the assessment of the cardiopulmonary vascular system is a cornerstone. The possibility of coupling the left and right ventricles with the pulmonary circuit during stress can provide significant insight into cardiopulmonary physiology in healthy and diseased subjects, can support the diagnosis of the etiology of pulmonary hypertension and other conditions, and can offer valuable prognostic information. In this state-of-the-art document, the topic of stress echocardiography applied to the cardiopulmonary vascular system is thoroughly addressed, from pathophysiology to different stress modalities and echocardiographic parameters, from clinical applications to limitations and future directions.

Stress echocardiography in patients with native valvular heart disease

Valve stress echocardiography (VSE) can be performed as exercise stress echocardiography (ESE) or dobutamine stress echocardiography (DSE) depending on the patient’s clinical status, severity and type of valve disease. ESE combines exercise testing with two-dimensional grey scale and Doppler echocardiography during exercise. Thus, it provides objective assessment of symptomatic status (exercise test), as well as exercise-induced changes of a series of echocardiographic parameters (different depending on the valve disease type), which yield prognostic information in individual patients and help in a better treatment planning. DSE is useful in symptomatic patients with low-gradient aortic stenosis. It clarifies its severity and helps in assessing surgical risk in patients with severe disease and systolic dysfunction. It can be also used to test valve haemodynamics in asymptomatic patients with significant mitral stenosis unable to perform an exercise test or to test the left ventricle response, namely to test viability, in patients with ischaemic secondary mitral regurgitation. VSE has taught us that history taking, clinical examination and resting echocardiography give an ‘incomplete picture’ of the disease in patients presenting with a severe valve disease. Therefore, its use should be encouraged in such patients.

Baseline mitral regurgitation predicts outcome in patients referred for dobutamine stress echocardiography

A number of parameters recorded during dobutamine stress echocardiography (DSE) are associated with worse outcome. However, the relative importance of baseline mitral regurgitation (MR) is unknown. The aim of this study was to assess the prevalence and associated implications of functional MR with long-term mortality in a large cohort of patients referred for DSE. 6745 patients (mean age 64.9 ± 12.2 years) were studied. Demographic, baseline and peak DSE data were collected. All-cause mortality was retrospectively analyzed. DSE was successfully completed in all patients with no adverse outcomes. MR was present in 1019 (15.1%) patients. During a mean follow up of 5.1 ± 1.8 years, 1642 (24.3%) patients died and MR was significantly associated with increased all-cause mortality (p < 0.001). With Kaplan-Meier analysis, survival was significantly worse for patients with moderate and severe MR (p < 0.001). With multivariate Cox regression analysis, moderate and severe MR (HR 2.78; 95% CI 2.17-3.57 and HR 3.62; 95% CI 2.89-4.53, respectively) were independently associated with all-cause mortality. The addition of MR to C statistic models significantly improved discrimination. MR is associated with all-cause mortality and adds incremental prognostic information among patients referred for DSE. The presence of MR should be taken into account when evaluating the prognostic significance of DSE results.

Assessment of aortic valve disease - a clinician oriented review

Aortic valve disease [aortic stenosis (AS) and aortic regurgitation (AR)] represents an important global health problem; when severe, aortic valve disease carries poor prognosis. For AS, aortic valve replacement, either surgical or interventional, may provide definite treatment in carefully selected patients. For AR, valve surgery (either replacement or - in selected cases - aortic valve repair) remains the gold standard of care. To properly identify those patients who are candidates for surgery, the clinician has to carefully assess the severity of valve disease with an understanding of the potential pitfalls involved in these assessments. This review focuses on the practical issues concerning the evaluation of patients with AS and AR from a general cardiologist’s perspective. The most important issues regarding the documentation of the severity of AS and AR are summarized. More specific issues, such as the role of stress echocardiography, other imaging techniques and details regarding the treatment options (medical, surgical, or interventional), are mentioned briefly.

The Role of Stress Echocardiography in Valvular Heart Disease: A Current Appraisal

Stress echocardiography is a widely available, safe, low-cost, versatile imaging modality which is becoming increasingly recognized as a valuable tool in the assessment of patients with native and prosthetic left-sided valvular heart disease. It provides a quantitative assessment to help guide clinical decision-making when discordance exists between symptoms and severity of valve disease. Exercise (treadmill or bicycle) remains the preferred stress modality, but pharmacological augmentation with dobutamine can be used if needed. Low-dose dobutamine stress echocardiography is specifically valuable in patients with low-flow, low-gradient aortic stenosis when attempting to differentiate true severe aortic stenosis from pseudo-severe aortic stenosis. Stress echocardiography not only identifies high-risk features that indicate need for earlier surgery, it also provides useful information for the peri- and postoperative period, including long-term outcome, risk stratification to guide monitoring frequency, and offers guidance for eligibility in competitive sports participation. As research continues to expand the utility of stress echocardiography in the management of patients with valvular heart disease, future research should focus on the recognition of newer parameters identifying high-risk features including subsequent validation in a large population.

Timing surgery in mitral regurgitation: defining risk and optimising intervention using stress echocardiography

Mitral regurgitation (MR) is the second most common form of valvular disease requiring surgery. Correct identification of surgical candidates and optimising the timing of surgery are key in management. For primary MR, this relies upon a balance between the peri-operative risks and rates of successful repair in patients undergoing early surgery when asymptomatic with the potential risk of irreversible left ventricular dysfunction if intervention is performed too late. For secondary MR, recognition that this is a highly dynamic condition where MR severity may change is key, although data on outcomes in determining whether concomitant valve intervention is performed with revascularisation has raised questions regarding timing of surgery. There has been substantial interest in the use of stress echocardiography to risk stratify patients in mitral regurgitation. This article reviews the role of stress echocardiography in both primary and secondary mitral regurgitation and discusses how this can help clinicians tackle the challenges of this prevalent condition.

Pulmonary Hypertension in Aortic Stenosis and Mitral Regurgitation: Rest and Exercise Echocardiography Significance

Valvular heart disease is a common cause of increased mean pulmonary artery pressure (PAP). Aortic stenosis and mitral regurgitation are frequently accompanied by pulmonary hypertension (PH), especially when they are severe and symptomatic. In asymptomatic patients, PH is rare, though the exact prevalence is unknown and mainly stems from the severity of the valvular heart disease and the presence of diastolic dysfunction. Exercise echocardiography has recently gained interest in depicting PH. In these asymptomatic patients, exercise PH is observed in about >40%. Either PH at rest (systolic PAP >50 mmHg) or during exercise (systolic PAP >60 mmHg) is a powerful determinant of outcome and is independently associated with reduced survival, regardless of the severity of the underlying valvular pathology.

A Comparison of 2 Mitral Annuloplasty Rings for Severe Ischemic Mitral Regurgitation: Clinical and Echocardiographic Outcomes

Controversies regarding the choice of annuloplasty rings for treatment of ischemic mitral regurgitation still exist. Aim of the study is to compare early performance of 2 different rings in terms of rest and exercise echocardiographic parameters (transmitral gradient, systolic pulmonary artery pressure, and mitral valve area), clinical outcomes, and recurrence of mitral regurgitation. From January 2008 till December 2013, prospectively collected data of patients who underwent coronary artery bypass grafting and undersizing mitral valve annuloplasty for severe chronic ischemic mitral regurgitation at our Institution were reviewed. A total of 93 patients were identified; among them 44 had semirigid Memo 3D ring implanted (group A) whereas 49 had a rigid profile 3D ring (group B). At 6 months, recurrent ischemic mitral regurgitation, equal or more than moderate, was observed in 4 and 6 patients in the group A and B, respectively (P = 0.74). Group A showed certain improved valve geometric parameters such as posterior leaflet angle, tenting area, and coaptation depth. Transmitral gradient was significantly higher at rest in the group B (P < 0.0001). During exercise, significant increase of transmitral gradient and systolic pulmonary artery pressure was observed in group B (P < 0.0001). Mitral valve area was not statistically significantly smaller at rest in between groups (P = 0.09); however, it significantly decreased with exercise in group B (P = 0.01). At midterm follow-up, patients in group B were more symptomatic. In patients with chronic ischemic mitral regurgitation, use of semirigid Memo 3D ring when compared to the rigid Profile 3D may be associated with early improved mitral valve geometrical conformation and hemodynamic profile, particularly during exercise. No difference was observed between both groups in recurrent mitral regurgitation.

[Structure and function of the mitral valve. Eligibility criteria for surgical and interventional approaches]

Mitral valve disease, especially severe mitral valve insufficiency, is an increasing issue in our population. Older patients with multiple comorbidities in particular are often denied surgery due to an increased perioperative risk. Because conservative medical treatment of mitral valve disease is often unsatisfactory, interventional techniques to treat mitral valve disease have emerged in recent years as serious alternatives to surgical treatment. Innovative developments in cardiovascular imaging have opened up new ways of looking at the mitral valve for improved diagnostic and therapeutic management of patients with mitral valve disease. These advantages of imaging are important for correct patient selection with either surgical or interventional strategies. This review describes the diagnostic capabilities of echocardiographic techniques for a precise diagnosis of the mitral valve structure and function for planning and performing interventional or surgical procedures.

Stress-echocardiography is underused in clinical practice: a nationwide survey in Austria

BACKGROUND

The wide area of application, including coronary artery disease, valvular heart disease, or pulmonary hypertension makes stress echocardiography (SE) a powerful, cost-effective imaging modality in cardiology. The role of this technique in clinical practice in Austria is unknown.

METHODS

A nationwide survey included all departments for cardiology and/or internal medicine in the years 2008 and 2013. By electronic questionnaire demographics, indication for the test, the numbers of examined cases per year, operators, and various applied techniques of SE were interrogated and completed by telephone interviews.

RESULTS

Data could be obtained from all 117 departments. In the year 2007 in 58 (50%) and in 2012 57 (49%) departments SE was available in Austrian hospitals. More than 100 SEs per year were performed by only four (7%) units in the year 2007 and by five (8%) in 2012. Physical exercise, dobutamine, and dipyridamole SE were available in 27 (46%), 52 (90%), and six (10%) units in 2007, and in 15 (27%), 52 (91%), and five (9%) units in 2012, respectively. In 2007 41 (71%) and in 2012 26 (46%) echo-labs administered contrast agents during SE. Transesophageal SE and 3D-echo was performed in one (2%) and three (5%) units in 2007, and in six (10%) and four (7%) echo-labs in 2012.

CONCLUSIONS

This representative survey demonstrates the underuse of SE in clinical practice in Austria. Even in established application fields performance is low, examination frequencies as recommended by the cardiology societies are fulfilled only by a minority of institutions.

Clinical significance of exercise pulmonary hypertension in secondary mitral regurgitation

In patients with heart failure, exercise echocardiography can help in risk stratification and decision making. The prognostic significance of exercise pulmonary hypertension (PH) in patients with secondary mitral regurgitation (MR) remains unknown. The aim of the present study was to assess the prognostic value of exercise PH in patients with secondary MR and narrow QRS intervals. From 2005 to 2012, 159 consecutive patients with secondary MR, narrow QRS intervals, left ventricular dysfunction (mean ejection fraction 36 ± 7%), and measurable systolic pulmonary arterial pressure (SPAP) during exercise echocardiography were included. Resting and exercise PH were defined as SPAP >50 and >60 mm Hg, respectively. Exercise PH was more frequent than resting PH (40% vs 13%, p <0.0001). On multivariate logistic regression, the independent determinants of exercise PH were resting SPAP (p <0.0001), exercise MR severity (p <0.0001), and e'-wave velocity (p = 0.004). The incidence of cardiac events during follow-up was significantly higher in patients with exercise PH compared with those without exercise PH (4 years: 40 ± 7% vs 20 ± 5%, p <0.0001). Patients with exercise PH exhibited higher rates of cardiac events and death than those with resting PH. In a multivariate Cox proportional hazards model, exercise PH was independently associated with the occurrence of cardiac events (p <0.0001). In conclusion, in patients with secondary MR, exercise PH is determined mainly by resting SPAP, left ventricular diastolic burden, and exercise MR severity. Exercise PH is a powerful predictor of poor outcomes, with a 5.3-fold increased risk for cardiac-related death during follow-up. These results highlight the added value of exercise echocardiography in secondary MR.

Therapeutic decision-making for patients with fluctuating mitral regurgitation

Mitral regurgitation (MR) is a common, progressive, and difficult-to-manage disease. MR is dynamic in nature, with physiological fluctuations occurring in response to various stimuli such as exercise and ischaemia, which can precipitate the development of symptoms and subsequent cardiac events. In both chronic primary and secondary MR, the dynamic behaviour of MR can be reliably examined during stress echocardiography. Dynamic fluctuation of MR can also have prognostic value; patients with a marked increase in regurgitant volume or who exhibit increased systolic pulmonary artery pressure during exercise have lower symptom-free survival than those who do not experience significant changes in MR and systolic pulmonary artery pressure during exercise. Identifying patients who have dynamic MR, and understanding the mechanisms underlying the condition, can potentially influence revascularization strategies (such as the surgical restoration of coronary blood flow) and interventional treatment (including cardiac resynchronization therapy and new approaches targeted to the mitral valve).

Decision Making in Asymptomatic Aortic Regurgitation in the Era of Guidelines

Background—

The decision-making role of exercise echocardiography in the surgical timing for aortic regurgitation remains a matter of debate because of limited data on its link with outcome. The aim of this study was to assess the role of echocardiographic measurements at rest and during exercise as predictors of valve surgery in asymptomatic aortic regurgitation.

Methods and Results—

Comprehensive resting and exercise echocardiography was performed in 159 consecutive patients (50±15 years; 80% male) with isolated moderately severe to severe aortic regurgitation and preserved left ventricular (LV) function (LV ejection fraction >50%, LV end-diastolic dimension ≤70 mm, LV end-systolic dimension ≤50 mm or ≤25 mm/m 2 ) in whom initial management was expectant. Echocardiographic measurements were performed at rest and during exercise. LV and right ventricular (RV) longitudinal strain was analyzed at rest using velocity vector imaging. Valve surgery was performed in 50 patients (31%) during 30±21 months. After adjustment for age and sex in a multivariable Cox proportional-hazards model, exercise tricuspid annular plane systolic excursion (TAPSE; hazards ratio [HR], 0.48; P =0.001) was associated with valve surgery-free, independent of resting LV strain (HR, 1.63; P =0.005), exercise LV end-diastolic volume (HR, 1.38; P =0.048), and resting RV strain (HR, 1.69; P =0.002). In sequential Cox models, a model based on clinical data (χ 2 , 20.4) was improved by resting LV strain (χ 2 , 30.1; P =0.001), resting RV strain (χ 2 , 49.7; P <0.001), and further increased by exercise TAPSE (χ 2 , 64.4; P <0.001).

Conclusions—

In asymptomatic aortic regurgitation, resting LV strain, resting RV strain, and exercise TAPSE were independently associated with the need for earlier aortic surgery.