Anaesthetic management of dogs with myxomatous mitral valve disease

Myxomatous mitral valve disease is the most commonly acquired heart disease in the dog. Affected dogs have a reduced forward stroke volume as a result of the regurgitant flow back through the compromised mitral valve leaflets. Primary care practitioners will be all too familiar with the challenges of performing a general anaesthetic on these animals and unfortunately, there is no ideal protocol for every case. Having knowledge of the haemodynamic changes that occur with myxomatous mitral valve disease, compared to structurally normal hearts, as well as a good understanding of pharmacological effects of agents used in general anaesthesia, is essential in the safe management of these cases. This article will summarise disease pathophysiology, concurrent cardiac medications and commonly used pre-anaesthetic, induction and maintenance agents available in primary care practice for use in dogs with myxomatous mitral valve disease.

Current Filaments in Asymmetric Surface Dielectric Barrier Discharge

In this study, we examine the statistical properties of asymmetric surface dielectric barrier discharges (SDBD) produced by applying a periodic high voltage between two conducting displaced electrodes, located at the opposite sides of a flat dielectric panel. Here, the asymmetry refers to the fact that the lower electrode is fully covered with an insulating material, while the upper one, glued onto the dielectric surface, is otherwise left exposed to the air. Such a configuration allows the formation of a thin layer of plasma above the insulating surface. A single cycle signal consists of two well-separated half-cycle patterns, denoted as forward and backward strokes, corresponding to positive and negative voltages, respectively. They display a quite complex discharge pattern constituted by a sequence of individual peaks (bursts) of varying current and time duration. Specifically, we find that backward stroke bursts carry a positive mean charge Q≃0.3 nC and mean current I≃35 mA, with a mean duration τ≃15 ns, while forward stroke bursts have a negative mean charge Q≃−0.1 nC, a mean current I≃−20 mA, and a mean duration τ≃11 ns. The statistical analysis suggests that power injection can be tailored to produce the active agents in the plasma needed for a particular application. We also determined discharge spatial correlation patterns from measurements of the associated stimulated optical emission. The optical excitations occur as a result of the ionizing effect of the electromagnetic waves which ignite the discharge, followed by the electric current flow. In particular, we point out that one of the phases of the discharge is compatible with a cathode directed streamer phenomenon (backward stroke), while the mechanism acting for a forward stroke has a different structure.

Long-term outcome after transcatheter mitral annuloplasty for secondary mitral regurgitation

Funding Acknowledgements Type of funding sources: None. Background The long-term effects of transcatheter mitral valve annuloplasty (TMVA) for secondary mitral regurgitation is unknown. Purpose We studied the clinical outcome and the effects on left ventricular (LV) function and remodeling and on mitral regurgitation (MR) severity after TMVA using the Carillon annuloplasty device. Methods We analyzed 33 consecutive patients with symptomatic MR who were treated with TMVA at Leipzig University Hospital between 2012 and 2018. Echocardiography was performed before TMVA and at follow-up. MR severity was quantitatively assessed by regurgitant volume (calculated as LV total stroke volume – LV forward stroke volume) and regurgitant fraction (calculated as regurgitant volume / LV total stroke volume). Results Mean age was 80 ± 10 years, 19 patients were women. A Society of Thoracic Surgeons (STS) score of 8.1 ± 7.2% indicated high risk status for mitral valve surgery. In 26 patients, mitral regurgitation resulted from LV remodeling and LV dysfunction, 7 suffered from left atrial dilatation. LV ejection fraction at baseline was 38% (30-49%; median, interquartile range). During a mean follow-up time of 45 ± 20 months, 17 patients died, 2 patients withdraw consent, and 4 patients were lost. Of the remaining patients, 4 were hospitalized for decompensated heart failure, and 2 underwent additional transcatheter edge-to-edge mitral valve repair. At follow-up, NYHA functional class improved from 95% in class III/IV at baseline to 70% in class I/II with no patients in NYHA class IV (p < 0.0001). Mitral regurgitant volume was reduced from 27mL (25-42mL) to 8mL (3-17mL) (p = 0.035) and regurgitant fraction from 43% (32-54%) to 11% (8-24%) (p = 0.020). LV end-diastolic volume index (92mL/m2 (71-107mL/m2) vs. 67mL/m2 (46-101mL/m2), p = 0.084) and end-systolic volumes index (51mL/m2 (44-69mL/m2) vs. 32mL/m2 (20-53mL/m2), p = 0.037) decreased. Thus, total stroke volume remained similar (38mL/m2 (33-43mL/m2) vs. 33mL/m2 (26-44mL/m2), p = 0.695) while LV ejection fraction increased (43% (31-49%) vs. 54% (46-57%), p = 0.032). Forward stroke volume, heart rate and forward cardiac output remained unchanged. Blood pressure was similar at baseline and at follow-up. Conclusion. Among high risk patients undergoing transcatheter mitral valve annuloplasty for symptomatic secondary MR, mortality was about 50% at 4 years. In the surviving patients, reduced MR severity was associated with fewer heart failure symptoms, reverse LV remodeling and improved LV function.

Abstract 13429: Echocardiographic Predictors of Mitral Transvalvular Gradients After Mitraclip Insertion

Introduction: The MitraClip procedure is a non-surgical alternative for patients with severe mitral regurgitation and high surgical risk. However, the MitraClip may lead to a reduction in the mitral valve orifice area (MVOA) and elevated transmitral mean gradients (TMG). The objectives of this study are to assess the value of baseline MVOA by different imaging methods and explore the value of MVOA indexed for left ventricular (LV) forward stroke volume (SV) to predict postprocedural TMG. Methods: Preprocedural echo images were retrospectively reviewed in 76 consecutive patients. MVOA from 2D transthoracic (MVOA TTE ), 2D transgastric (MVOA TG ) and 3D transesophageal (MVOA 3D ) echocardiography were measured and then indexed by the SV measured by Doppler in the LV outflow tract (MVOA/SV) . Postprocedural TMG was measured at one month and survival rate at one year. Results: Patients with postprocedural TMG >5 mmHg (18/76, 24%) had significantly smaller preprocedural MVOA 3D (3.9±0.9 vs 5.2±1.3 cm 2 , p<0.01) and MVOA TTE (4.9±1.1 vs 5.9±1.5 cm 2 , p=0.02). No significant difference was found for MVOA TG (5.5±1.4 vs 5.9±1.4 cm 2 , p=0.2). Best threshold values for MVOA 3D and MVOA TTE to predict postprocedural TMG >5 mmHg were respectively 3.9 cm 2 (AUC=0.80, IC95%: 0.67-0.94, p<0.01; sensitivity (Se) 62%, specificity (Sp) 87%) and 4,6 cm 2 (AUC=0.69, IC95%: 0.54-0.83, p=0.02; Se 50%, Sp 84%). MVOA/SV from each echocardiographic modality were smaller in patients with postprocedural TMG >5 mmHg (3D: 80 [62-95] vs 113 [99-129] cm 2 /L; TTE: 92 [81-105] vs 130 [100-166] cm 2 /L; TG: 104 [83-123] vs 135 [104-166] cm 2 /L; p<0.01 for all). MVOA/SV 3D was overall the best predictor of postprocedural TMG >5 mmHg, with an optimal threshold of 96 cm 2 /L (AUC=0.86, IC95%: 0.76-0.97, p<0.001; Se 84%, Sp 81%). Patients with MVOA 3D <3.9 cm 2 and MVOA/SV 3D <96 cm 2 /L tend to be at higher risk for mortality at one-year follow-up (69% vs 84%, p=0.14 and 67% vs 87%, p=0.11 respectively). Conclusion: Unlike preprocedural MVOAs assessed by 3D echocardiography, preprocedural MVOAs measured by 2D echocardiographic modalities were poor predictors of high TMG after MitraClip. Preprocedural MVOA 3D <3.9 cm 2 and MVOA/SV 3D <96 cm 2 /L were found to be the best cut-off values to predict postprocedural TMG >5 mmHg.

The mechanism of vortex bifurcation vis-à-vis axial switching in rectangular synthetic jets

The present study investigates the vortex dynamics of the rectangular shaped synthetic jet and reports the occurrence of vortex ring bifurcation along with other reported modes such as axial switching and the vortex suction. The novel finding of vortex ring bifurcation of rectangular synthetic jets has been observed without any other mode of excitation except the periodic axial actuation. The experiments on synthetic jets have been conducted at different actuation frequencies and both qualitative and quantitative characterization of the flow structures has been carried out using Laser Induced Fluorescence (LIF) and Laser Doppler Velocimetry, respectively. LIF flow visualization provides insights into the size of the vortex and the vortex evolution with respect to time, enabling us to propose the flow physics behind the axial switching and the vortex bifurcation processes for rectangular synthetic jets. The proposed flow physics is then quantitatively evidenced by the time-averaged velocity measurements. Vortex splitting or bifurcation is found to occur in the minor axis plane of orifice and the divergence angle depends on the actuation frequency and average velocity of fluid expelled through the orifice in the forward stroke of diaphragm. In the case of occurrence of axial switching, a maximum of three axial switching events are observed before vortex breakup. Finally, by systematically carrying out experiments across a wide range of operational parameters, a narrow region corresponding to the vortex bifurcation has been identified on a Reynolds Number-Strouhal Number map, along with other modes such as axial switching regime and the vortex suction regime. Based on our measurements, a mechanism of vortex bifurcation vis-à-vis axial switching has also been suggested.

Abstract TP265: Far-Forward Stroke Care: Parallel Processing in the Prehospital Environment May Achieve Door-to-Needle Times of Less Than 15 Minutes on a Mobile Stroke Treatment Unit

Introduction: The time from 911 activation (i.e. alarm) to administration of intravenous (IV) alteplase in acute ischemic stroke is associated with functional, patient centered-outcomes. Mobile stroke treatment units (MSTUs) have emerged as a stroke system tool that may hasten treatment times. Optimal workflows on MSTUs remain to fully elucidated. Methods: Retrospective review of a QA database of patients treated on a MSTU with door-to-needle-times (DTN) of </= 15 minutes to describe workflows and team dynamics that were associated with expeditious treatment. Results: In October of 2018 the University of Rochester Medical Center launched a MSTU, initially operating on Monday through Friday in the city of Rochester from 8am until 4 pm. Over the initial 3 months, there were 96 MSTU responses leading to 54 transported patients, 3 of which were treated with IV alteplase. One patient with an initial NIHSS of 17 was treated with IV alteplase within 9 minutes of reaching the MSTU door. Workflow elements felt to hasten treatment included registration of the patient in the electronic health record (EHR) prior to the patient reaching the MSTU and enabling the telestroke provider to listen to the initial history and physical being performed by the MSTU RN at the scene. The later is accomplished by using a telestroke iPhone application that allows for a “3-way-call” between the MSTU RN, the MSTU, and the telestroke provider. The MSTU RN wears a Bluetooth earpiece that captures the conversation with the patient, witnesses on scene, and initial EMS responders and enables the MSTU RN to summarizes key history and exam findings, vitals, and blood glucose results while keeping their hands available for patient care. Simultaneously, the telestroke provider reviews the patient’s chart in the EHR for alteplase contraindications, prior imaging results, and pertinent medical history. Conclusion: Registering the patient in the EHR and integrating the telestroke provider into the initial patient assessment at the scene in the prehospital setting may allow for consistent door to needle times of < 15 minutes on MSTUs, which may further improve patient outcomes.

A chordwise offset of the wing-pitch axis enhances rotational aerodynamic forces on insect wings: a numerical study

Most flying animals produce aerodynamic forces by flapping their wings back and forth with a complex wingbeat pattern. The fluid dynamics that underlies this motion has been divided into separate aerodynamic mechanisms of which rotational lift, that results from fast wing pitch rotations, is particularly important for flight control and manoeuvrability. This rotational force mechanism has been modelled using Kutta–Joukowski theory, which combines the forward stroke motion of the wing with the fast pitch motion to compute forces. Recent studies, however, suggest that hovering insects can produce rotational forces at stroke reversal, without a forward motion of the wing. We have conducted a broad numerical parametric study over a range of wing morphologies and wing kinematics to show that rotational force production depends on two mechanisms: (i) conventional Kutta–Joukowski-based rotational forces and (ii) a rotational force mechanism that enables insects with an offset of the pitch axis relative to the wing's chordwise symmetry axis to generate rotational forces in the absence of forward wing motion. Because flying animals produce control actions frequently near stroke reversal, this pitch-axis-offset dependent aerodynamic mechanism may be particularly important for understanding control and manoeuvrability in natural flyers.