Blood flow assessment technology in aortic surgery: a narrative review.

Background and Objective: Blood flow assessment is an emerging technique that allows for assessment of hemodynamics in the heart and blood vessels. Recent advances in cardiovascular imaging technologies have made it possible for this technique to be more accessible to clinicians and researchers. Blood flow assessment typically refers to two techniques: measurement-based flow visualization using echocardiography or four-dimensional flow magnetic resonance imaging (4D flow MRI), and computer-based flow simulation based on computational fluid dynamics modeling. Using these methods, blood flow patterns can be visualized and quantitative measurements of mechanical stress on the walls of the ventricles and blood vessels, most notably the aorta, can be made. Thus, blood flow assessment has been enhancing the understanding of cardiac and aortic diseases; however, its introduction to clinical practice has been negligible yet. In this article, we aim to discuss the clinical applications and future directions of blood flow assessment in aortic surgery. We then provide our unique perspective on the technique's translational impact on the surgical management of aortic disease. Methods: Articles from the PubMed database and Google Scholar regarding blood flow assessment in aortic surgery were reviewed. For the initial search, articles published between 2013 and 2023 were prioritized, including original articles, clinical trials, case reports, and reviews. Following the initial search, additional articles were considered based on manual searches of the references from the retrieved literature. Key Content and Findings: In aortic root pathology and ascending aortic aneurysms, blood flow assessment can elucidate postoperative hemodynamic changes after surgical reconfiguration of the aortic valve complex or ascending aorta. In cases of aortic dissection, analysis of blood flow can predict future aortic dilatation. For complicated congenital aortic anomalies, surgeons may use preoperative imaging to perform "virtual surgery", in which blood flow assessment can predict postoperative hemodynamics for different surgical reconstructions and assist in procedural planning even before entering the operating room. Conclusions: Blood flow assessment and computational modeling can evaluate hemodynamics and flow patterns by visualizing blood flow and calculating biomechanical forces in patients with aortic disease. We anticipate that blood flow assessment will become an essential tool in the treatment planning and understanding of the progression of aortic disease.

Open, endovascular, or hybrid repair of aortic arch disease: narrative review of diverse strategies with diverse options.

OBJECTIVES AND METHODS: The management of aortic arch disease is complex. Open surgical management continues to evolve, and the introduction of endovascular repair is revolutionizing aortic arch surgery. Although these innovative techniques have generated the opportunity for better outcomes in select patients, they have also introduced confusion and uncertainty regarding best practices. In New York, we have developed a collaborative group named the New York Aortic Consortium (NYAC) as a means of crosslinking knowledge and working together to better understand and treat aortic disease. In our meeting in May 2023, regional aortic experts and invited international experts discussed the contemporary management of aortic arch disease, differences in interpretation of the available literature, as well as the integration of endovascular technology into disease management. In this review article, we summarize the current state of aortic arch surgery. RESULTS: Approaches to aortic arch repair have evolved substantially, whether it be methods to reduce cerebral ischaemia, improve hemostasis, simplify future operations, or expand options for high-risk patients with endovascular approaches. However, the transverse aortic arch remains challenging to repair. Amongst our collaborative group of cardiac/aortic surgeons, we discovered a wide disparity in our practice patterns and management strategies of patients with aortic arch disease. CONCLUSIONS: It is important to build unique institutional expertise in the context of complex and evolving management of aortic arch disease with open surgery, endovascular repair, and hybrid approaches, tailored to the risk profiles and anatomical specifics of individual patients.

Utility of structured follow-up imaging after aortic surgery.

BACKGROUND: Although postoperative follow-up after aortic surgery is recommended by guidelines, its clinical utility is not well documented. We hypothesized that structured follow-up imaging by an aortic program would improve outcomes. We then documented radiologic findings on asymptomatic postoperative imaging. METHODS: All patients who survived to discharge after open thoracic aortic surgery between January 2017 and July 2021 were included, excluding endocarditis. Patients who followed at our center and received scheduled imaging were compared with patients who did not. Survival was analyzed by the method of Kaplan-Meier, and reintervention was assessed using the Fine-Gray subhazard function. Routine imaging was reviewed for aortic growth, pseudoaneurysm, and perigraft density. RESULTS: After aortic surgery, the cumulative incidence of follow-up was 38.6% at 3 years postoperatively. Patients with follow-up were more likely to have a dissection and fewer comorbidities but were similar in regards to socioeconomic factors and distance to hospital. After matching and accounting for immortal time bias, patients with follow-up had a greater reintervention rate (26.0% vs 9.0%) with similar survival (98.7% vs 95.2%, P = .110) at 4 years. The cumulative incidence of pseudoaneurysm, significant perigraft density, and growth ≥3 mm/year on routine imaging was 49.7% at 3 years. CONCLUSIONS: Implementation of structured follow-up imaging by an aortic program resulted in low clinical compliance. Follow-up was associated with increased rates of aortic reintervention. Clinically relevant radiologic findings were common on asymptomatic imaging and increased throughout 5-year follow-up rather than plateauing in the early postoperative period.

Side-by-side deployment of gore excluder legs at a narrow terminal aorta for endovascular aneurysm repair.

PURPOSE: A narrow terminal aorta is a risk factor for endograft occlusion after endovascular aneurysm repair. To minimize limb complications, we used Gore Excluder legs positioned side-by-side at the terminal aorta. We investigated the outcomes of our strategy for endovascular aneurysm repair in patients with a narrow terminal aorta. METHODS: We enrolled 61 patients who underwent endovascular aneurysm repair with a narrow terminal aorta (defined as < 18 mm in diameter) from April 2013 to October 2021. The standard procedure involves complete treatment with the Gore Excluder device. When other types of main body endografts were used, they were deployed proximal to the terminal aorta, and we used the Gore Excluder leg device in the bilateral limbs. Postoperatively, the intraluminal diameter of the legs at the terminal aorta was measured to assess the configuration. RESULTS: During the follow-up period (mean: 2.7 ± 2.0 years), there were no aorta-related deaths, endograft occlusions, or leg-related re-interventions. There were no significant differences between the pre- and postoperative ankle-brachial pressure index values in the dominant and non-dominant legs (p = 0.44 and p = 0.17, respectively). Postoperatively, the mean difference rate (defined as [dominant leg diameter-non-dominant leg diameter]/terminal aorta diameter) was 7.5 ± 7.1%. The difference rate was not significantly correlated with the terminal aortic diameter, calcification thickness, or circumferential calcification (r = 0.16, p = 0.22; r = 0.07, p = 0.59; and r = - 0.07, p = 0.61, respectively). CONCLUSIONS: Side-by-side deployment of Gore Excluder legs produces acceptable outcomes for endovascular aneurysm repair with a narrow terminal aorta. The endograft expansion at the terminal aorta is tolerable without influencing calcification distribution.

Coronary artery bypass grafting for coronary artery anomalies in infants and young children.

OBJECTIVES: Coronary artery bypass grafting (CABG) has been reported for coronary artery diseases in patients with Kawasaki disease and coronary artery complications after arterial switch operations for transposition of the great arteries. However, only a few studies have explored this modality for congenital coronary artery anomalies. As congenital coronary artery anomalies, particularly left coronary artery atresia and stenosis, are one of the reasons for sudden death, coronary revascularization is often required in infants and young children. Therefore, we aimed to investigate the outcome of CABG for such anomalies in infants and young children. METHODS: From 2014 to 2018, 3 infants and 2 children (median age: 10 months; range: 6-40 months) with coronary artery anomalies underwent CABG at our hospital. The indications for the procedure included left main coronary artery atresia and stenosis in 2 and 3 patients, respectively. Graft patency was evaluated postoperatively by contrast-enhanced computed tomography or coronary angiography, and postoperative outcomes (including death and cardiac events) were assessed during the follow-up period. RESULTS: No 30-day or in-hospital mortalities were noted. Postoperative examinations revealed patent grafts in all patients. They were discharged without any cardiac complications. Regarding the outcomes at the follow-up period, the graft patency rate was 80.0% (4/5 grafts), with no deaths or cardiac events. CONCLUSIONS: CABG is a useful strategy for coronary revascularization in infants and young children with coronary artery anomalies. Although the mid-term outcomes and patency are satisfactory, careful follow-up is necessary because the long-term outcomes remain unknown.

Sufficient cardiac unloading by Impella 5.0 in left ventricular rupture following mitral valve replacement: a case report.

A 72-year-old woman presented with exertional dyspnea. Echocardiography revealed severe mitral valve stenosis; therefore, mitral valve replacement was performed using a bioprosthetic valve. However, left ventricular wall rupture occurred following mitral valve replacement. Under re-cardiac arrest, we found a left ventricular tear under the posterior annulus of the mitral valve. We repaired the left ventricular muscle using a bovine pericardial patch and implanted a bioprosthetic valve again. Postoperatively, we implanted an Impella 5.0 heart pump through the right axillary artery to ensure left ventricular wall unloading. Systemic blood flow depended almost completely on mechanical circulatory assistance until postoperative day 3. After the fourth postoperative day, we started weaning the patient from Impella 5.0. Finally, it was completely discontinued on the sixth postoperative day. After that, the patient's condition was stable, and she was discharged 44 days postoperatively. Impella 5.0 is a potentially beneficial device for left ventricular unloading in patients with left ventricular wall rupture following mitral valve replacement.

Estimating the Haemodynamic Streamline Vena Contracta as the Effective Orifice Area Measured from Reconstructed Multislice Phase-contrast MR Images for Patients with Moderately Accelerated Aortic Stenosis.

PURPOSE: In aortic stenosis (AS), the discrepancy between moderately accelerated flow and effective orifice area (EOA) continues to pose a challenge. We developed a method of measuring the vena contracta area as hemodynamic EOA using cardiac MRI focusing on AS patients with a moderately accelerated flow to solve the problem that AS severity can currently be determined only by echocardiography. METHODS: We investigated 40 patients with a peak transvalvular velocity > 3.0 m/s on transthoracic echocardiography (TTE). The patients were divided into highly accelerated and moderately accelerated AS groups according to whether or not the peak transvalvular velocity was ≥ 4.0 m/s. From the multislice 2D cine phase-contrast MRI data, the cross-sectional area of the vena contracta of the reconstructed streamline in the Valsalva sinus was defined as MRI-EOAs. Patient symptoms and echocardiography data, including EOA (defined as TTE-EOA), were derived from the continuity equation using TTE. RESULTS: All participants in the highly accelerated AS group (n = 19) showed a peak velocity ≥ 4.0 m/s in MRI. Eleven patients in the moderately accelerated AS group (n = 21) had a TTE-EOA < 1.00 cm2. In the moderately accelerated AS group, MRI-EOAs demonstrated a strong correlation with TTE-EOAs (r = 0.76, P < 0.01). Meanwhile, in the highly accelerated AS group, MRI-EOAs demonstrated positivity but a moderate correlation with TTE-EOAs (r = 0.63, P = 0.004). MRI-EOAs were overestimated compared to TTE-EOAs. In terms of the moderately accelerated AS group, the best cut-off value for MRI-EOAs was < 1.23 cm2, compatible with TTE-EOAs < 1.00 cm2, with an excellent prediction of the New York Heart Association classification ≥ III (sensitivity 87.5%, specificity 76.9%). CONCLUSION: MRI-EOAs may be an alternative to conventional echocardiography for patients with moderately accelerated AS, especially those with discordant echocardiographic parameters.

Blood flow energy loss: a predictor for the recovery of left ventricular function after bioprosthetic aortic valve replacement.

OBJECTIVES: It is difficult to estimate the improvement in left ventricular (LV) function after aortic valve replacement (AVR). The present study aimed to evaluate whether energy loss (EL) can predict the postoperative LV function after AVR. METHODS: Nine patients who underwent AVR with a bioprosthetic valve were enrolled in the present study. Porcine prostheses were used in 5 patients and bovine pericardial prostheses were used in 4 patients. The aortic flow pattern was visualized and EL and cardiac output (CO) were measured using 4-dimensional flow magnetic resonance imaging from the LV to the descending aorta; the EL/CO ratio in the extracted area was calculated as total EL/CO ratio. RESULTS: With a porcine valve, a severe helical flow was observed in the ascending aorta during the holosystolic phase. In contrast, with a bovine pericardial valve, straight transvalvular aortic flow was observed in the early systolic phase and 2 large vortical flows occurred on both sides of the greater and lesser curvature of the ascending aorta after the mid-systolic period. The total EL/CO ratio was strongly correlated with LV ejection fraction improvement after AVR (r = 0.74, P = 0.02). CONCLUSIONS: The aortic flow pattern is different between the porcine valve and bovine pericardial valve. The total EL/CO ratio is a valuable tool for evaluating the postoperative LV ejection fraction improvement after AVR. Optimization of total EL/CO ratio would have potential to improve haemodynamic performances after AVR.

Determination of the dominant arch by computational fluid dynamics analysis using computed tomography images in double aortic arch.

Computational fluid dynamics (CFD) analysis using computed tomography images can reveal the details of the blood flow in cardiovascular disease. In double aortic arch, it is difficult to assess the hemodynamics because of the strong influence of various anatomical features, such as the angle of the aortic bifurcation. In the present study, we reported that CFD analysis is a valuable method for hemodynamic assessment in patients with double aortic arch.

Prediction for future occurrence of type A aortic dissection using computational fluid dynamics.

OBJECTIVES: The actual underlying mechanisms of acute type A aortic dissection (AAAD) are not well understood. The present study aimed to elucidate the mechanism of AAAD using computational fluid dynamics (CFD) analysis. METHODS: We performed CFD analysis using patient-specific computed tomography imaging in 3 healthy control cases and 3 patients with AAAD. From computed tomography images, we made a healthy control model or pre-dissection model for CFD analysis. Pulsatile cardiac flow during one cardiac cycle was simulated, and a three-dimensional flow streamline was visualized to evaluate flow velocity, wall shear stress and oscillatory shear index (OSI). RESULTS: In healthy controls, the transvalvular aortic flow was parallel to the ascending aorta. There was no spotty high OSI area at the ascending aorta. In pre-dissection patients, accelerated transvalvular aortic flow was towards the posterolateral ascending aorta. The vortex flow was observed on the side of the lesser curvature in mid-systole and expanded throughout the entire ascending aorta during diastole. Systolic wall shear stress was high due to the accelerated aortic blood flow on the side of the greater curvature of the ascending aorta. On the side of the lesser curvature, high OSI areas were observed around the vortex flow. In all pre-dissection cases, a spotty high OSI area was in close proximity to the actual primary entry site of the future AAAD. CONCLUSIONS: The pre-onset high OSI area with vortex flow is closely associated with the future primary entry site. Therefore, we can elucidate the mechanism of AAAD with CFD analysis.

Alternative pulmonary artery reconstruction technique in the arterial switch operation.

OBJECTIVES: Late complications of arterial switch operations (ASO) for transposition of the great arteries, such as neo-pulmonary artery (PA) stenosis and/or neoaortic regurgitation, have been reported. We developed an alternative reconstruction method called the longitudinal extension (LE) method to prevent PA bifurcation stenosis (PABS). METHODS: We identified 48 patients diagnosed with transposition of the great arteries and performed ASO using the Lecompte manoeuvre for neo-PA reconstruction. In 9 consecutive patients (from 2014), the LE method was performed (LE). Before 2014, conventional techniques were performed in 39 patients (C). The median body weight and age in the LE and C groups were 3.0 and 3.1 kg and 12 and 26 days, respectively. In the LE group, 1 patient underwent bilateral PA banding before ASO. In C, PA banding and arch repair were performed in 1 patient each. Patients who received concomitant procedures were included. RESULTS: The median follow-up in LE and C groups was 1.9 and 10.1 years, respectively. Early mortality/late death was not found in group LE and in 1 patient in group C. Only 1 case required ascending aorta sliding plasty in LE, and 8 patients needed PA augmentation for PABS in C. The median velocity of right/left PA was measured as 1.6/1.9 m/s in LE and 2.1/2.3 m/s in C, so it showed a lower value in LE. CONCLUSIONS: Excellent mid-term results were obtained with the LE method. It was considered a useful procedure in preventing PABS, which is a primary late complication of ASO. Further follow-up and investigations are needed.

Computerized virtual surgery based on computational fluid dynamics simulation for planning coronary revascularization with aortic root replacement in adult congenital heart disease: a case report.

A 38-year-old woman presented with exertional dyspnea and chest compression. She had undergone repair of congenital supravalvular aortic stenosis at 8 years of age. Contrast-enhanced computed tomography showed re-stenosis in the ascending aorta, bilateral coronary arterial aneurysm, and a highly thickened left ventricular wall. Release of stenosis was necessary to avoid left ventricular functional deterioration; however, it could cause demand-supply mismatch in coronary flow due to substantial left ventricular hypertrophy. Sufficient statistical evidence was not available in this situation; therefore, computerized virtual surgery based on computational fluid dynamics (CFD) was performed to predict the postoperative hemodynamics. Consequently, root replacement with in situ Carrel patch coronary reconstruction was considered a better option than coronary artery graft bypass in the left-side coronary flow supply. The patient underwent root replacement with in situ Carrel patch coronary reconstruction as planned based on CFD without any complication and was discharged 15 days postoperatively.

Computational fluid dynamics of internal mammary artery-left anterior descending artery anastomoses.

OBJECTIVES: The aim of this study was to elucidate the remodelling of the internal mammary artery (IMA)-left anterior descending artery anastomosis and compare 2 different anastomosis techniques (end-to-side versus side-to-side) using computational fluid dynamics. METHODS: This study included 9 patients. Computed tomography (CT) angiography was performed immediately after coronary artery bypass grafting (CABG) and at 3-6 months later. The computational fluid dynamics models were made using the CT data. The pulsatile 3-dimensional blood flow was achieved with the finite volume method to evaluate the postoperative morphological and haemodynamic changes at the anastomosis in each patient. Flow velocity distribution, wall shear stress (WSS) and its fluctuation oscillatory shear index were measured. RESULTS: No early or mid-term graft occlusion was observed in the study series. In the side-to-side anastomosis, pouch formation at the distal end of IMA caused a vortex flow with low WSS immediately after CABG. However, at 3-6 months after surgery, this pouch disappeared. As a result, the laminar straight flow with uniform WSS distribution was achieved inside the anastomosis. In the end-to-side anastomosis, the anastomosis shape was remodelled, resulting in a laminar flow pattern with uniform WSS distribution. A patchy high oscillatory shear index was detected at the IMA wall on the top of anastomosis in either anastomosis techniques immediately after the surgery, but it disappeared at 3-6 months after surgery. CONCLUSIONS: Regardless of the anastomosis technique used, a successful remodelling of the IMA-left anterior descending artery anastomosis shape was achieved a few months after surgery, resulting in a straightforward flow streamline, with uniform WSS distribution and minimal oscillatory shear index.

Delayed patch repair of a ruptured mitral subvalvular pseudoaneurysm caused by infective endocarditis: a case report.

BACKGROUND: Ruptured subvalvular pseudoaneurysm is a rare but significantly fatal complication of infective endocarditis. We report a successful surgical case of ruptured subvalvular pseudoaneurysm with infective endocarditis. CASE SUMMARY: A 46-year-old man presenting with high fever was admitted to a local hospital. Physical examination revealed small erythema and petechiae on his lower limbs. Transthoracic echocardiogram did not show any visible vegetation and valvular disease; however, magnetic resonance imaging (MRI) showed multiple acute cerebral infractions, and methicillin-susceptible Staphylococcus aureus was detected in the blood culture. Infective endocarditis was suspected, and an antibacterial medication was initiated. Twelve days later, he suffered from a sudden cardiogenic shock due to cardiac tamponade. Bloody pericardial effusion (1600 mL) was drained, and his condition improved substantially. Transoesophageal echocardiography after pericardial drainage revealed severe mitral regurgitation and a subvalvular aneurysm at the posteromedial side of the mitral annulus; these were not detected at the time of admission. He was transferred to our hospital for surgery; however, since fresh cerebral bleeding was observed in MRI, the surgery was delayed. Three weeks later, after confirming that the blood culture was negative for any growth, patch repair of the subvalvular pseudoaneurysm and mitral valve repair were performed. Post-operatively, no complication or arrhythmia was observed; he was discharged 25 days later. DISCUSSION: We report a rare case of successful delayed surgery for a ruptured subvalvular pseudoaneurysm at the posteromedial side of the mitral annulus, which presented complications for infective endocarditis by S. aureus.

Early and mid-term outcome of frozen elephant trunk using spinal cord protective perfusion strategy for acute type A aortic dissection.

OBJECTIVE: This study aimed to evaluate the prevalence of spinal cord injury in total arch replacement with frozen elephant trunk for acute type A aortic dissection using our spinal cord protection technique. METHODS: Between January 2013 and December 2017, 33 patients underwent total arch replacement with frozen elephant trunk for acute type A aortic dissection (mean age 67.9 ± 13.3 years). Our spinal cord protection technique involved maintaining extracorporeal circulation through the left subclavian artery in all procedures, using aortic occlusion balloon during distal anastomosis, and inserting frozen elephant trunk above Th 8 with transesophageal echocardiographic guidance. Computed tomography was performed within 1-2 weeks, 12 months, and 36 months postoperatively. We compared the degree of thrombosis of the descending aorta between preoperation and early postoperative period by Fisher's exact test. Moreover, we evaluated postoperative mortality and mobility (including spinal cord injury) at follow-up. RESULTS: The operative mortality within 30 days was 6.1%. Neither paraplegia nor paraparesis was noted. We observed significant thrombosis of the false lumen at the distal arch and aortic valve level of the descending aorta in postoperative early term period (p < 0.01). At mid-term follow-up (mean 33.9 months), survival probability and 3-year freedom from reoperation rates were 93.9 ± 4.1% and 95.0 ± 4.9%, respectively. CONCLUSIONS: The frozen elephant trunk technique with our spinal protection strategy provides good postoperative outcomes. Our strategy can maintain spinal cord perfusion without complete ischemia time even during lower body ischemia time. Implementation of our spinal protection strategy will help prevent spinal cord injury and dilated downstream aorta.

Surgical Strategies for Type B Aortic Dissection by Frozen Elephant Trunk.

The timing and choice of surgical method for type B aortic dissection, is still a topic of much debate. We performed total arch replacement using frozen elephant trunk (TAR-FET) as a means of preventing distant aortic events, such as retrograde type A aortic dissection (RTAD). We conducted analysis of 142 patients with acute type B dissection who were admitted between January of 2010 and July of 2017. Fifty-five cases required surgical intervention to treat enlargement of the false lumen diameter and ULP formation 2 weeks after the onset of symptoms. 17 TAR-FET were performed with a mean of 42±26 days period from onset to surgery. There were no complications of RTAD or paraplegic, and 90% of patient demonstrated aortic event free survival (5 years) and false lumen reduction ratio of 35%. Based on our analysis, using TAR-FET properly avoids serious complications like RTAD, and is a viable treatment option for type B dissection. (This is a translation of J Jpn Coll Angiol 2018; 58: 151-157.).

Modified Double Patch Repair for Septal Rupture With Ventricular Wall Dissection.

Ventricular septal rupture with ventricular free wall dissection is an extremely rare complication after inferior myocardial infarction, and the optimal surgical strategy remains unclear because of the limited number of survival cases. Electrocardiography-synchronized contrast computed tomography was performed before surgery to identify the dissected area and to set up a surgical strategy. We report on modified double patch repair with ventricular wall dissection exclusion, which might be effective for preventing residual shunt and maintaining cardiac function.