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Perioperative evaluation of regional aortic wall shear stress patterns in patients undergoing aortic valve and/or proximal thoracic aortic replacement.

ABSTRACT: OBJECTIVES:To assess in patients with aortopathy perioperative changes in thoracic aortic wall shear stress (WSS), which is known to affect arterial remodeling, and the effects of specific surgical interventions. METHODS:Presurgical and postsurgical aortic 4D flow MRI were performed in 33 patients with aortopathy (54 ± 14 years; 5 women; sinus of Valsalva (d_SOV)/midascending aortic (d_MAA) diameters = 44 ± 5/45 ± 6 mm) scheduled for aortic valve (AVR) and/or root (ARR) replacement. Control patients with aortopathy who did not have surgery were matched for age, sex, body size, and d_MAA (n = 20: 52 ± 14 years; 3 women; d_SOV/d_MAA = 42 ± 4/42 ± 4 mm). Regional aortic 3D systolic peak WSS was calculated. An atlas of WSS normal values was used to quantify the percentage of at-risk tissue area with abnormally high WSS, excluding the area to be resected/graft. RESULTS:Peak WSS and at-risk area showed low interobserver variability (?0.09 [-0.3; 0.5] Pa and 1.1% [-7%; 9%], respectively). In control patients, WSS was stable over time (follow-up-baseline differences ?0.02 Pa and 0.0%, respectively). Proximal aortic WSS decreased after AVR (n = 5; peak WSS difference ?-0.41 Pa and at-risk area ?-10%, P < .05 vs controls). WSS was increased after ARR in regions distal to the graft (peak WSS difference ?0.16 Pa and at-risk area ?4%, P < .05 vs AVR). Follow-up duration had no significant effects on these WSS changes, except when comparing ascending aortic peak WSS between ARR and AVR (P = .006). CONCLUSIONS:Serial perioperative 4D flow MRI investigations showed distinct patterns of postsurgical changes in aortic WSS, which included both reductions and translocations. Larger longitudinal studies are warranted to validate these findings with clinical outcomes and prediction of risk of future aortic events.

SUBMITTER: Bollache E

PROVIDER: S-EPMC5955775 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Perioperative evaluation of regional aortic wall shear stress patterns in patients undergoing aortic valve and/or proximal thoracic aortic replacement.

Bollache Emilie E Fedak Paul W M PWM van Ooij Pim P Rahman Ozair O Malaisrie S Chris SC McCarthy Patrick M PM Carr James C JC Powell Alex A Collins Jeremy D JD Markl Michael M Barker Alex J AJ

The Journal of thoracic and cardiovascular surgery 20171116 6

<h4>Objectives</h4>To assess in patients with aortopathy perioperative changes in thoracic aortic wall shear stress (WSS), which is known to affect arterial remodeling, and the effects of specific surgical interventions.<h4>Methods</h4>Presurgical and postsurgical aortic 4D flow MRI were performed in 33 patients with aortopathy (54 ± 14 years; 5 women; sinus of Valsalva (d_SOV)/midascending aortic (d_MAA) diameters = 44 ± 5/45 ± 6 mm) scheduled for aortic valve (AVR) and/or root (ARR) replacemen ...[more]

PMID: 29248286

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Project description:OBJECTIVES:The objectives of this study were to investigate an association between the magnitude of flow-mediated aortic wall shear stress (WSS) and medial wall histopathology in patients with bicuspid aortic valve (BAV) with aortopathy. METHODS:Patients with BAV (n = 27; 52 ± 15 years; 3 women; proximal thoracic aorta diameter = 4.4 ± 0.7 and 4.6 ± 0.5 cm) who underwent prophylactic aortic resection received preoperative 3-dimensional time-resolved phase-contrast magnetic resonance imaging with 3-dimensional velocity encoding to quantify WSS relative to a population of healthy age- and sex-matched tricuspid aortic valve control participants (n = 20). Quantitative histopathology was conducted on BAV aorta tissue samples resected at surgery (n = 93), and correlation was performed between elastic fiber thickness and in vivo aortic WSS as continuous variables. Validation of elastic fiber thickness was achieved by correlation relative to tissue stiffness determined using biaxial biomechanical testing (n = 22 samples). RESULTS:Elastic fibers were thinner and WSS was higher along the greater curvature compared with other circumferential regions (vs anterior wall: P = .003 and P = .0001, respectively; lesser curvature: both P = .001). Increased regional WSS was associated with decreased elastic fiber thickness (r = -0.25; P = .02). Patient stratification with subanalysis showed an increase in the correlation between WSS and histopathology with aortic valve stenosis (r = -0.36; P = .002) and smaller aortic diameters (<4.5 cm: r = -0.39; P = .03). Elastic fiber thinning was associated with circumferential stiffness (r = -0.41; P = .06). CONCLUSIONS:For patients with BAV, increased aortic valve-mediated WSS is significantly associated with elastic fiber thinning, particularly with aortic valve stenosis and in earlier stages of aortopathy. Elastic fiber thinning correlates with impaired tissue biomechanics. These novel findings further implicate valve-mediated hemodynamics in the progression of BAV aortopathy.

Project description:ObjectiveGuidelines for repair of bicuspid aortic valve-associated ascending thoracic aortic aneurysms have been changing, most recently to the same criteria as tricuspid aortic valve-ascending thoracic aortic aneurysms. Rupture/dissection occurs when wall stress exceeds wall strength. Recent studies suggest similar strength of bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms; thus, comparative wall stress may better predict dissection in bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms. Our aim was to determine whether bicuspid aortic valve-ascending thoracic aortic aneurysms had higher wall stresses than their tricuspid aortic valve counterparts.MethodsPatients with bicuspid aortic valve- and tricuspid aortic valve-ascending thoracic aortic aneurysms (bicuspid aortic valve = 17, tricuspid aortic valve = 19) greater than 4.5 cm underwent electrocardiogram-gated computed tomography angiography. Patient-specific 3-dimensional geometry was reconstructed and loaded to systemic pressure after accounting for prestress geometry. Finite element analyses were performed using the LS-DYNA solver (LSTC Inc, Livermore, Calif) with user-defined fiber-embedded material model to determine ascending thoracic aortic aneurysm wall stress.ResultsBicuspid aortic valve-ascending thoracic aortic aneurysms 99th-percentile longitudinal stresses were 280 kPa versus 242 kPa (P = .028) for tricuspid aortic valve-ascending thoracic aortic aneurysms in systole. These stresses did not correlate to diameter for bicuspid aortic valve-ascending thoracic aortic aneurysms (r = -0.004) but had better correlation to tricuspid aortic valve-ascending thoracic aortic aneurysms diameter (r = 0.677). Longitudinal stresses on sinotubular junction were significantly higher in bicuspid aortic valve-ascending thoracic aortic aneurysms than in tricuspid aortic valve-ascending thoracic aortic aneurysms (405 vs 329 kPa, P = .023). Bicuspid aortic valve-ascending thoracic aortic aneurysm 99th-percentile circumferential stresses were 548 kPa versus 462 kPa (P = .033) for tricuspid aortic valve-ascending thoracic aortic aneurysms, which also did not correlate to bicuspid aortic valve-ascending thoracic aortic aneurysm diameter (r = 0.007).ConclusionsCircumferential and longitudinal stresses were greater in bicuspid aortic valve- than tricuspid aortic valve-ascending thoracic aortic aneurysms and were more pronounced in the sinotubular junction. Peak wall stress did not correlate with bicuspid aortic valve-ascending thoracic aortic aneurysm diameter, suggesting diameter alone in this population may be a poor predictor of dissection risk. Our results highlight the need for patient-specific aneurysm wall stress analysis for accurate dissection risk prediction.

Project description:Background Patients undergoing surgery for thoracic aortic aneurysms receive statin therapy out of proportion to cardiovascular comorbidity. We sought to determine the prevalence of statin use among patients presenting for thoracic aortic aneurysm surgery and investigate its effect on outcomes.Methods From January 1, 2005 to January 1, 2011, 1,839 consecutive patients underwent aortic replacement for degenerative thoracic aortic aneurysm at Cleveland Clinic. Of these, 771 (42%) were on statins preoperatively. Statin users (vs. nonstatin users) were older (65 ± 11 vs. 56 ± 16 years) and had more hypertension (78 vs. 59%). Propensity matching based on 56 preoperative variables other than lipid levels was used to compare outcomes among 570 matched patient pairs (74% of possible pairs).Results Propensity-matched statin and nonstatin users were aged 64 ± 11 years, 394 (69%) versus 387 (68%) were male, and 437 (77%) versus 442 (78%) had ascending aortic aneurysms, respectively. Overall, 25% of patients were followed for more than 8.2 years and 10% for more than 10 years. Perioperative outcomes were similar, including hospital mortality (11 [1.9%] vs. 5 [0.88%]) and stroke (22 [3.9%] vs. 13 [2.3%]), but 16 statin users (2.8%) versus 5 nonstatin users (0.88%) required temporary dialysis after surgery (p = 0.02). At 6 years, 3.7% of statin users versus 5.1% of nonstatin users (p[log-rank] = 0.5) underwent further aortic surgery, and at 10 years, mortality was 25% in both groups (p > 0.5).Conclusion Patients presenting for thoracic aortic aneurysm surgery frequently receive unnecessary statins. Additionally, statin use was associated with more postoperative renal failure, but not less intermediate-term risk for aortic reintervention or all-cause mortality after surgery. Therefore, presence of a thoracic aortic aneurysm should not be considered an indication for statin therapy in the absence of well-established indications.

Dataset Information

Perioperative evaluation of regional aortic wall shear stress patterns in patients undergoing aortic valve and/or proximal thoracic aortic replacement.

Publications

Perioperative evaluation of regional aortic wall shear stress patterns in patients undergoing aortic valve and/or proximal thoracic aortic replacement.

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