Chikashi Aoki

Suture Forces in Undersized Mitral Annuloplasty: Novel Device and Measurements

PURPOSE To demonstrate the first use of a novel technology for quantifying suture forces on annuloplasty rings to better understand the mechanisms of ring dehiscence. DESCRIPTION Force transducers were developed, attached to a size 24 Physio ring, and implanted in the mitral annulus of an ovine animal. Ring suture forces were measured after implantation and for cardiac cycles reaching peak left ventricular pressures (LVP) of 100, 125, and 150 mm Hg. EVALUATION After implantation of the undersized ring to the flaccid annulus, the mean suture force was 2.0±0.6 N. During cyclic contraction, the anterior ring suture forces were greater than the posterior ring suture forces at peak LVPs of 100 mm Hg (4.9±2.0 N vs 2.1±1.1 N), 125 mm Hg (5.4±2.3 N vs 2.3±1.2 N), and 150 mm Hg (5.7±2.4 N vs 2.4±1.1 N). The largest force was 7.4 N at 150 mm Hg. CONCLUSIONS The preliminary results demonstrate trends in annuloplasty suture forces and their variation with location and LVP. Future studies will significantly contribute to clinical knowledge by elucidating the mechanisms of ring dehiscence while improving annuloplasty ring design and surgical repair techniques.

The Influence of Mitral Annuloplasty on Left Ventricular Flow Dynamics

BACKGROUND Mitral valve (MV) repair using annuloplasty rings is the preferred method of treatment for MV regurgitation, but the impact of annuloplasty ring placement on left ventricular intraventricular flow has not been studied. METHODS Annuloplasty rings of varying sizes were placed in 5 healthy sheep (intercommissural ring sizes were 24, 26, 28, 30, and 32 mm), and three-dimensional phase contrast magnetic resonance imaging (4D flow MRI) was performed before and 1 week after ring placement. RESULTS Normal diastolic flow consisted of diastolic intraventricular vortices that naturally unwound during systole. Postsurgical intraventricular flow was highly disturbed in all sheep, and the disturbance was greatest for undersized rings. Ring size was highly correlated with the diastolic inflow angle (Pearsons r = -0.62, p < 0.1, 95% confidence interval: -0.92 to 0.14). There was a mean angle increase of mean diastolic inflow angle increase of 12.3 degrees (< 30 mm, p < 0.01, 95% confidence interval: 4.8 to 19.6) for rings less than 30 mm. There was an inverse relationship between peak velocity and annuloplasty ring area (Pearsons r = -0.80, p < 0.05, 95% confidence interval: -0.96 to -0.2). Transmitral pressure gradients increased significantly from baseline 0.73 ± 0.18 mm Hg to after annuloplasty 2.31 ± 1.04 mm Hg (p < 0.05). CONCLUSIONS Mitral valve annuloplasty ring placement disturbs normal left ventricular intraventricular flow patterns, and the degree of disturbance is closely associated with annuloplasty ring size.

Implantation of the Medtronic Harmony Transcatheter Pulmonary Valve Improves Right Ventricular Size and Function in an Ovine Model of Postoperative Chronic Pulmonary Insufficiency

Background—Pulmonary insufficiency is the nexus of late morbidity and mortality after transannular patch repair of tetralogy of Fallot. This study aimed to establish the feasibility of implantation of the novel Medtronic Harmony transcatheter pulmonary valve (hTPV) and to assess its effect on pulmonary insufficiency and ventricular function in an ovine model of chronic postoperative pulmonary insufficiency. Methods and Results—Thirteen sheep underwent baseline cardiac magnetic resonance imaging, surgical pulmonary valvectomy, and transannular patch repair. One month after transannular patch repair, the hTPV was implanted, followed by serial magnetic resonance imaging and computed tomography imaging at 1, 5, and 8 month(s). hTPV implantation was successful in 11 animals (85%). There were 2 procedural deaths related to ventricular fibrillation. Seven animals survived the entire follow-up protocol, 5 with functioning hTPV devices. Two animals had occlusion of hTPV with aneurysm of main pulmonary artery. A strong decline in pulmonary regurgitant fraction was observed after hTPV implantation (40.5% versus 8.3%; P=0.011). Right ventricular end diastolic volume increased by 49.4% after transannular patch repair (62.3–93.1 mL/m2; P=0.028) but was reversed to baseline values after hTPV implantation (to 65.1 mL/m2 at 8 months, P=0.045). Both right ventricular ejection fraction and left ventricular ejection fraction were preserved after hTPV implantation. Conclusions—hTPV implantation is feasible, significantly reduces pulmonary regurgitant fraction, facilitates right ventricular volume improvements, and preserves biventricular function in an ovine model of chronic pulmonary insufficiency. This percutaneous strategy could potentially offer an alternative for standard surgical pulmonary valve replacement in dilated right ventricular outflow tracts, permitting lower risk, nonsurgical pulmonary valve replacement in previously prohibitive anatomies.

Saddle-Shaped Annuloplasty Improves Leaflet Coaptation in Repair for Ischemic Mitral Regurgitation

BACKGROUND Current repair results for ischemic mitral regurgitation (IMR) with undersized annuloplasty rings are characterized by high IMR recurrence rates. Current annuloplasty rings treat annular dilatation, but they do little to improve (and may actually exacerbate) leaflet tethering. New saddle-shaped annuloplasty rings have been shown to maintain or restore a more physiologic annular and leaflet geometry and function. Using a porcine IMR model, we sought to demonstrate the influence of annuloplasty ring shape on leaflet coaptation. METHODS Eight weeks after posterolateral infarct, eight pigs with grade 2+ or higher IMR were randomized to undergo either a 28-mm flat ring annuloplasty (n = 4) or a 28-mm saddle-shaped ring annuloplasty (n = 4). Real-time three-dimensional echocardiography and a customized image analysis protocol allowed three-dimensional assessment of leaflet coaptation before and after annuloplasty. RESULTS Total leaflet coaptation area was significantly higher after saddle-shaped ring annuloplasty (109.6 ± 26.9 mm(2)) compared with flat ring annuloplasty (46.2 ± 7.7 mm(2), p <0.01). After annuloplasty, total coaptation area decreased by 87.5 mm(2) (or 65%) in the flat annuloplasty group (p = 0.01), whereas total coaptation area increased by 22.2 mm(2) (or 25%) in the saddle-shaped annuloplasty group (p = 0.28). CONCLUSIONS This study shows that the use of undersized saddle-shaped annuloplasty rings in mitral valve repair for IMR improves leaflet coaptation, whereas the use of undersized flat annuloplasty rings worsens leaflet coaptation. Because one of Carpentiers fundamental principles of mitral valve repair (durability) is to create a large surface of coaptation, saddle-shaped annuloplasty may increase repair durability.

Real-Time Magnetic Resonance Imaging Technique for Determining Left Ventricle Pressure-Volume Loops

BACKGROUND Rapid determination of the left ventricular (LV) pressure-volume (PV) relationship as loading conditions are varied is the gold standard for assessment of LV function. Cine magnetic resonance imaging (MRI) does not have sufficient spatiotemporal resolution to assess beat-to-beat changes of the LV PV relationship required to measure the LV end-systolic elastance (EES) or preload-recruitable stroke work (PRSW). Our aim was to investigate real-time MRI and semiautomated LV measurement of LV volume to measure PV relations in large animals under normal and inotropically stressed physiologic conditions. METHODS We determined that PV relationships could be accurately measured using an image exposure time Tex less than 100 ms and frame rate Tfr less than 50 ms at elevated heart rates (∼140 beats per minute) using a golden angle radial MRI k-space trajectory and active contour segmentation. RESULTS With an optimized exposure time (Tex=95 ms and frame rate Tfr=2.8 ms), we found that there was no significant difference between cine and real-time MRI at rest in end-diastolic volume, end-systolic volume, ejection fraction, stroke volume, or cardiac output (n=5, p<0.05) at either normal or elevated heart rates. We found EES increased from 1.9±0.7 to 3.1±0.3 mm Hg/mL and PRSW increased from 6.2±1.2 to 9.1±0.9 mm Hg during continuous intravenous dobutamine infusion (n=5, p<0.05). CONCLUSIONS Real-time MRI can assess LV volumes, EES, and PRSW at baseline and elevated inotropic states.

Injectable Microsphere Gel Progressively Improves Global Ventricular Function, Regional Contractile Strain, and Mitral Regurgitation After Myocardial Infarction

BACKGROUND There is continued need for therapies which reverse or abate the remodeling process after myocardial infarction (MI). In this study, we evaluate the longitudinal effects of calcium hydroxyapatite microsphere gel on regional strain, global ventricular function, and mitral regurgitation (MR) in a porcine MI model. METHODS Twenty-five Yorkshire swine were enrolled. Five were dedicated weight-matched controls. Twenty underwent posterolateral infarction by direct ligation of the circumflex artery and its branches. Infarcted animals were randomly divided into the following 4 groups: 1-week treatment; 1-week control; 4-week treatment; and 4-week control. After infarction, animals received either twenty 150 μL calcium hydroxyapatite gel or saline injections within the infarct. At their respective time points, echocardiograms, cardiac magnetic resonance imaging, and tissue were collected for evaluation of MR, regional and global left ventricular function, wall thickness, and collagen content. RESULTS Global and regional left ventricular functions were depressed in all infarcted subjects at 1 week compared with healthy controls. By 4-weeks post-infarction, global function had significantly improved in the calcium hydroxyapatite group compared with infarcted controls (ejection fraction 0.485 ± 0.019 vs 0.38 ± 0.017, p < 0.01). Similarly, regional borderzone radial contractile strain (16.3% ± 1.5% vs 11.2% ± 1.5%, p = 0.04), MR grade (0.4 ± 0.2 vs 1.2 ± 0.2, p = 0.04), and infarct thickness (7.8 ± 0.5 mm vs 4.5 ± 0.2 mm, p < 0.01) were improved at this time point in the treatment group compared with infarct controls. CONCLUSIONS Calcium hydroxyapatite injection after MI progressively improves global left ventricular function, borderzone function, and mitral regurgitation. Using novel biomaterials to augment infarct material properties is a viable alternative in the current management of heart failure.

Vacuum-assisted venous drainage in tricuspid valve re-replacement

The number of reoperations for prosthetic valve replacement has increased in recent years due to the steady increase in life expectancy. However, reoperations are complex and require experience and skills. We report the case of a 69-year-old female with severe right heart failure who underwent tricuspid valve re-replacement 28 years after the initial tricuspid valve replacement. Cardiopulmonary bypass with vacuum-assisted venous drainage (VAVD) was used to achieve better perfusion flow and heart decompression with smaller venous cannulae. The operation was successful. The VAVD system is effective in patients who have a persistent elevation of central venous pressure.

Improved Outcomes for Ruptured Abdominal Aortic Aneurysms Using Integrated Management Involving Endovascular Clamping, Endovascular Replacement, and Open Abdominal Decompression

Objective: Endovascular repair has become the treatment of choice for ruptured abdominal aortic aneurysms (RAAAs). To improve surgical outcomes, preoperative management is important. In 2011, we introduced integrated management, which involves endovascular aneurysm repair, stabilization of hemodynamics by endovascular clamping, and open abdominal decompression to address abdominal compartment syndrome (ACS). Methods: To evaluate the efficacy of this management strategy, 62 patients who had undergone emergency surgery for an RAAA were analyzed retrospectively: group A (n=39), where an old strategy was used, and group B (n=23), where integrated management was introduced. Patient characteristics and 30-day mortality rates were compared between the two groups. Results: The average patient age was 67.7 years and 74.7 years for groups A and B, respectively (P=0.032). Group B patients required more frequent use of vasopressors (P=0.035). Other patient characteristics did not differ between the two groups. The duration of surgery was significantly shorter in group B than in group A (P=0.001). The total amount of transfused blood did not differ between the two groups. No patients showed symptoms of ACS. Early mortality rates were 12.8% and 8.7% in groups A and B, respectively. The number of wound infections was significantly fewer in group B than in group A. Conclusion: Although group B patients were significantly older and had a higher rate of vasopressor use, early mortality was improved in both groups. Morbidity was significantly better in group B with respect to the duration of surgery and number of wound infections than in group A.

Surgical Management of Mycotic Aortic Aneurysms

Purpose: A mycotic aneurysm is an uncommon disease associated with a high mortality rate when managed surgically. This study reviewed our experiences in the surgical management of mycotic aortic aneurysms. Methods: In total, 26 patients who underwent surgery for a mycotic aneurysm were retrospectively reviewed. The mycotic aneurysms involved the thoracic aorta in 9 patients, the thoracoabdominal aorta in 4 patients, and the abdominal aorta in 13 patients. An overt aortic rupture in the mediastinum or retroperitoneal space was detected in 4 patients. Patients were classified into one of two groups, febrile or afebrile, and background characteristics, surgical intervention, and early and late mortalities were all compared. Results: There were 19 patients who underwent open surgery, and 7 patients underwent endovascular repair. No significant differences in the clinical characteristics were found between the two groups; however, the incidence of postoperative complications was significantly higher in the febrile group than in the afebrile group (P=0.024). Overall mortality was 15.4% (4/26), and 30-day mortality was 7.7% (2/26). Conclusion: Although febrile patients had a higher incidence of postoperative complications, surgical mortality from a mycotic aneurysm was within an acceptable range. Each patient should be thoroughly evaluated and treated on a case-by-case basis, using conventional open repair, endovascular repair, or a combination of both approaches.

Management of Pulmonary Thromboembolism Based on Severity and Vulnerability to Thrombolysis

Background: The incidence of pulmonary thromboembolism has been considered rare in Japan. However, its occurrence has been increasing because of westernized lifestyle and diet, increased diagnostic technique, and recognition of this disease. Method: Between January 2003 and September 2014, 179 patients were treated for pulmonary thromboembolism. We classified these patients into 3 groups; Massive (n=35), Sub-massive (n=29) and Nonmassive (n=115) and retrospectively reviewed the treatment options and the outcome. Results: Percutaneous cardiopulmonary support (PCPS) was applied for patients with hemodynamic instability and IVC filter was inserted if there was proximal DVT. In non-massive group (n=115), 95.7% of the patient underwent anticoagulant therapy and 47.0% of the patients received IVC filter. In submassive group (n=29), 48.3% of the patient received thrombolytic therapy and 93.1% of the patient underwent IVC filter insertion. Surgical pulmonary embolectomy was performed in 3 patients who had high risk of thrombolytic therapy in submassive group. There was no death in this group. In massive group, 4 patients who had cardiogenic shock died in acute phase. PCPS was applied in 5 patients, pulmonary embolectomy was performed in 13 patients, thrombolytic therapy was performed in 4 patients and 13 patients underwent anticoagulant therapy alone. There were 7 deaths (20.0%) in this group. Conclusions: In submassive group, treatment should be decided depending on the bleeding risk. In massive group, pulmonary embolectomy was effective. (This is a translation of Jpn J Phlebol 2016; 27: 53–59.)