Aortic valve leaflet and root dimensions in normal tricuspid aortic valves: A computed tomography study.

BACKGROUND AND AIM OF THE STUDY: The aim of this study was to use coronary computed tomography in patients with normal tricuspid aortic valves to perform detailed aortic root and aortic valve geometric analysis with a focus on the asymmetry of the three leaflets. METHODS: Retrospective analysis of anonymized coronary computed tomography angiograms was performed using dedicated software, where manual aortic root segmentation and marking of several points of interest were followed by automated measurements of aortic root and leaflets. Asymmetry of the three leaflets in individual patients was assessed by calculating absolute and relative differences between the largest and the smallest of the three leaflets. RESULTS: We analyzed 70 aortic valves, the mean patient age was 53 ± 11 years, and 50% (n = 35) of patients were female. All aortic valves were tricuspid, without calcifications and aortic roots were of normal dimensions. Some degree of asymmetry was present in all analyzed valves. Absolute and relative differences for free margin length were 3.2 ± 1.4 mm and 9.3 ± 3.8%, respectively. The largest relative difference was noted in the coaptation area (36.5 ± 16.5%) and the smallest in leaflet effective height (6.1 ± 4.8%). Using predefined cutoff criteria for absolute differences in leaflet dimensions, 86% of the valves were classified as asymmetric. CONCLUSIONS: Most normal tricuspid aortic valves show some degree of asymmetry. Equal free margin length of the three leaflets is not needed for normal tricuspid aortic valve function. Leaflet effective height showed the least amount of asymmetry confirming its importance in keeping the aortic valve competent.

Segmental analysis of aortic basal ring dimensions in normal and dilated tricuspid aortic roots.

OBJECTIVES: In patients with aortic root aneurysm, the aortic basal ring is frequently dilated. It has been speculated that the muscular part of the basal ring dilates most. The purpose of this study was to analyse the segmental dilatation of the basal ring, comparing normal and dilated roots in patients with tricuspid aortic valves. METHODS: Retrospective analysis of computed tomography studies in patients with normal and dilated aortic roots was performed. Lengths of segments of the basal ring corresponding to each of the 3 sinuses, and to the muscular and fibrous parts were measured. Fractions of these segments relative to the total basal ring perimeter were calculated. RESULTS: We analysed 152 normal and 126 dilated aortic roots and 86 propensity-matched pairs. Basal ring dilatation was present in all segments of dilated aortic roots with subtle differences between the segments corresponding to the 3 sinuses. The muscular part of the basal ring dilated proportionately to its fibrous part, with no difference in fractions of measured muscular part in normal and dilated roots [42.2% (interquartile range 4.3%) vs 42.1% (interquartile range 6.3%)]. CONCLUSIONS: Basal ring dilatation was present in all segments corresponding to the 3 sinuses in dilated aortic roots. Both muscular and fibrous parts dilated equally, supporting the need to stabilize the entire basal ring when performing aortic valve repair surgery.

Left ventricular venting in veno-arterial extracorporeal membrane oxygenation: A computer simulation study.

INTRODUCTION: Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is the fastest way to restore circulation in refractory cardiogenic shock, however it cannot unload the failing left ventricle. There is a lack of consensus regarding optimal approach to left ventricular venting in V-A ECMO patients with severely depressed or absent left ventricular function. METHODS: A computer model was developed in Matlab Simulink R20016b (MathWorks, Inc., Natick, MA, USA) to analyze different venting options as well as atrial septostomy in the setting of cardiogenic shock and V-A ECMO. RESULTS: The model has shown an inverse linear relationship between left atrial pressure and either vent, Impella or atrial septum defect flow rate. The minimum vent flow required to prevent pulmonary edema in complete loss of left ventricular function needed to be higher than the bronchial blood flow. Atrial septostomy restored normal pulmonary blood flow with low left atrial pressure but induced stasis in the left ventricle. Venting the pulmonary artery induced stasis in the entire pulmonary circulation as well as left atrium and left ventricle. Venting the left ventricle directly with a cannula or Impella device avoided blood stasis. CONCLUSION: Our data suggest that reduction of left atrial pressure is linearly related to the vent, Impella or atrial septal defect flow rate. The preferred vent location is the left ventricle as it avoids stasis in the pulmonary circulation and cardiac chambers.

New graft sizing rings for aortic valve reimplantation procedures.

OBJECTIVES: The objective was to design sizing rings that would enable proper sizing of the graft in reimplantation procedures and to perform leaflet repair before graft implantation. METHODS: The rings were designed in Autodesk Fusion 360 (San Rafael, CA, USA) and 3D printed using a commercial online 3D printing service. We designed incomplete rings with a low profile and complete rings with a high profile. The complete rings are best suited for reimplantation procedures, whereas low profile C rings are intended for isolated aortic valve repair, where the ascending aorta is not transected. The rings come in sizes corresponding to Vascutek Gelweave graft sizes (Vascutek Terumo, Renfrewshire, Scotland). The ring internal diameters are 5% larger than the designated ring sizes and account for the 5% stretch of the grafts when pressurized. Blades of the rings are placed at 20° intervals. The slits between the blades are designed in such a way that the commissural U-sutures, when put in place and under tension, will lock the ring in position. RESULTS: The rings were successfully used in 10 of our latest reimplantation procedures. After dissection of the aortic root, the commissures were suspended with U-stitches and then the ring was seated onto them. Complete leaflet repair with plication to achieve adequate effective height was then performed, followed by graft implantation. No additional leaflet repair was needed. CONCLUSIONS: The newly designed sizing rings enable proper sizing of the graft in reimplantation procedures and enable complete leaflet repair before graft implantation.

Understanding coronary artery bypass transit time flow curves: role of bypass graft compliance.

OBJECTIVES: Low mean bypass graft flow (Q) and high pulsatility index (PI) measured by the transit time flow measurement method are not specific for anastomotic stenosis, but occur with competitive flow and poor coronary run-off. We hypothesized that graft compliance is responsible for these changes and that flow measured at the proximal end of the coronary bypass can be viewed as a sum of the graft capacitive flow and flow that passes through the distal anastomosis. METHODS: Transit time flow measurements (TTFMs) of 15 left internal thoracic artery (LITA) to LAD bypass grafts and 10 saphenous vein grafts (SVGs) to either the right coronary artery (RCA) or posterior descending artery (PDA) were analysed. The TTFM was performed on the proximal and distal end of the graft, and proximally with distal occlusion of the graft. Low mean bypass graft flow PI and diastolic filling (DF) measured distally and proximally were compared, and graft compliance was estimated. RESULTS: Diastolic filling was higher distally in every single case (LITA-LAD: distal DF 76 ± 12% vs proximal 66 ± 13%, P = 0.005; SVG-RCA/PDA: distal 72 ± 15% vs proximal 63 ± 12%, P = 0.018). There were no significant differences in Q and PI. Subtracting the distal from the proximal flow gave a result identical to the proximal TTFM in distally occluded grafts, confirming the presence of graft capacitive flow. Graft compliance estimated from the flow of distally occluded grafts was 0.99 ± 0.47 µl/mmHg for LITA grafts and 0.78 ± 0.42 µl/mmHg for SVG grafts. CONCLUSIONS: The study confirmed that the TTFM measured at the proximal end of the coronary bypass could be viewed as a sum of graft capacitive flow and the flow that passes through the distal anastomosis. Graft capacitive flow increases the systolic and decreases the diastolic TTFM when measured at the proximal end of the graft. It explains the higher DF when the TTFM is measured at the distal end of the graft and the increase in the PI at the proximal end when Q decreases. As the influence of graft capacitive flow on the PI in low Q can be eliminated by performing the TTFM at the distal end of the graft, we believe that the value of PI is clinically irrelevant.

Mitral regurgitation and axial flow left ventricular assist device: a computer simulation study.

Good right ventricular function is one of the major determinants of long-term outcomes in patients with implanted left ventricular assist devices (LVADs). In the present study, a computer model was developed to assess the impact of mitral regurgitation on right ventricular workload at different levels of LVAD support. Left ventricular assist device was simulated by a model of HeartMate II. The computer model has shown that the regurgitant volume of the mitral valve falls significantly only after the systolic pressure in the left ventricle decreases, which occurs at higher LVAD revolutions per minute (RPM) when there is no ejection through the aortic valve. However, at low LVAD RPM, the pressures in the left atrium and the pulmonary artery decrease significantly, despite a small decrease in regurgitant volume. According to the computer model, LVAD support decreases mitral regurgitation. Furthermore, regurgitant volume has a smaller impact on the right ventricular afterload when compared with a heart without LVAD support.