Matthew S. Jackson

Quantification of chronic functional mitral regurgitation by automated 3-dimensional peak and integrated proximal isovelocity surface area and stroke volume techniques using real-time 3-dimensional volume color doppler echocardiography: In vitro and clinical validation

Background—The aim of this study was to test the accuracy of an automated 3-dimensional (3D) proximal isovelocity surface area (PISA) (in vitro and patients) and stroke volume technique (patients) to assess mitral regurgitation (MR) severity using real-time volume color flow Doppler transthoracic echocardiography. Methods and Results—Using an in vitro model of MR, the effective regurgitant orifice area and regurgitant volume (RVol) were measured by the PISA technique using 2-dimensional (2D) and 3D (automated true 3D PISA) transthoracic echocardiography. The mean anatomic regurgitant orifice area (0.35±0.10 cm2) was underestimated to a greater degree by the 2D (0.12±0.05 cm2) than the 3D method (0.25±0.10 cm2; P<0.001 for both). Compared with the flowmeter (40±14 mL), the RVol by 2D PISA (20±19 mL) was underestimated (P<0.001), but the 3D peak (43±16 mL) and integrated PISA-based (38±14 mL) RVol were comparable (P>0.05 for both). In patients (n=30, functional MR), 3D effective regurgitant orifice area correlated well with cardiac magnetic resonance imaging RVol r=0.84 and regurgitant fraction r=0.80. Compared with cardiac magnetic resonance imaging RVol (33±22 mL), the integrated PISA RVol (34±26 mL; P=0.42) was not significantly different; however, the peak PISA RVol was higher (48±27 mL; P<0.001). In addition, RVol calculated as the difference in automated mitral and aortic stroke volumes by real-time 3D volume color flow Doppler echocardiography was not significantly different from cardiac magnetic resonance imaging (34±21 versus 33±22 mL; P=0.33). Conclusions—Automated real-time 3D volume color flow Doppler based 3D PISA is more accurate than the 2D PISA method to quantify MR. In patients with functional MR, the 3D RVol by integrated PISA is more accurate than a peak PISA technique. Automated 3D stroke volume measurement can also be used as an adjunctive method to quantify MR severity.

Functional 3D Printed Patient-Specific Modeling of Severe Aortic Stenosis

Computed tomography (CT) provides high-resolution images of the aortic valve with clear localization of calcium deposition. Three-dimensional (3D) stereolithographic printing can be used to convert these data into a physical model [(1,2)][1]. We hypothesized that patient-specific, multimaterial, 3D

Transesophageal Echocardiography–Guided Percutaneous Intervention for a Mitral Valve Leaflet Perforation

A 67-year-old woman with coronary artery disease, peripheral vascular disease, and end-stage renal disease on hemodialysis presented with refractory decompensated congestive heart failure. Echocardiography showed severe mitral regurgitation from 2 sources: poor leaflet coaptation due to tethering of

An in vitro validation of cardiac magnetic resonance 4D flow measurements with bioprosthetic mitral valve flow volumes quantification

Background Four dimensional flow MRI is a new methodology for evaluating the morphology of the heart using phase contrast cardiac magnetic resonance imaging not only in the usual three dimensions (x, y and z), but also across time. The full breadth of this new form of imaging has yet to be fully established. In order to evaluate this modality and its accuracy, we decided to use 4D flow MRI to quantify diastolic flow volumes across a bioprosthetic valve (BPV) in a controlled and reproducible in vitro system. Methods Three different sizes of BMV’s (27, 29, and 31 mm) were consecutively mounted in an MRI compatible flow loop where the flow conditions could be controlled using software that programmed a pump to generate pulsatile, physiologic ventricular ejection and filling simulations. The generated pulses were generated using each valve and mimicked diastolic flow volumes of about 70, 90 and 110 ml/beat at a rate of 70 bpm. An in-series ultrasonic flow transducer (UFT) was used to measure flow (L/min) by which diastolic flow volumes were determined. The acquisition of 3D cine (4D flow) phase contrast velocity data was acquired in a 1.5 Tesla MRI scanner (Avanto, Siemens Medical Solutions, Inc., Erlangen, Germany). The typical imaging parameters were: repetition time 45-48 ms, echo time 2.75 ms, flip angle 15°, slice thickness 1.5 mm, field of view 350 × 260 mm2, voxel size 1.5 × 1 × 1.25 mm3. The flow measurements were determined at 3 locations within the valve in post-imaging examination including at the valve base, leaflet tips, and midway between the base and the tips. Results

Four-dimensional flow cardiovascular magnetic resonance in aortic dissection: Assessment in an ex vivo model and preliminary clinical experience

Objective Four‐dimensional flow cardiovascular magnetic resonance may improve assessment of hemodynamics in patients with aortic dissection. The purpose of this study was to evaluate the feasibility and accuracy of 4‐dimensional flow cardiovascular magnetic resonance assessment of true and false lumens flow. Methods Thirteen ex vivo porcine aortic dissection models were mounted to a flow loop. Four‐dimensional flow cardiovascular magnetic resonance and 2‐dimensional phase‐contrast cardiovascular magnetic resonance measurements were performed, assessed for intraobserver and interobserver variability, and compared with a reference standard of sonotransducer flow volume measurements. Intraobserver and interobserver variability of 4‐dimensional flow cardiovascular magnetic resonance were also assessed in 14 patients with aortic dissection and compared with 2‐dimensional phase‐contrast cardiovascular magnetic resonance. Results In the ex vivo model, the intraobserver and interobserver measurements had Lins correlation coefficients of 0.98 and 0.96 and mean differences of 0.17 (±3.65) mL/beat and −0.59 (±5.33) mL/beat, respectively; 4‐dimensional and sonotransducer measurements had a Lins concordance correlation coefficient of 0.95 with a mean difference of 0.35 (±4.92) mL/beat, respectively. In patients with aortic dissection, the intraobserver and interobserver measurements had Lins concordance correlation coefficients of 0.98 and 0.97 and mean differences of −0.95 (±8.24) mL/beat and 0.62 (±10.05) mL/beat, respectively; 4‐dimensional and 2‐dimensional flow had a Lins concordance correlation coefficient of 0.91 with a mean difference of −9.27 (±17.79) mL/beat because of consistently higher flow measured with 4‐dimensional flow cardiovascular magnetic resonance in the ascending aorta. Conclusions Four‐dimensional flow cardiovascular magnetic resonance is feasible in patients with aortic dissection and can reliably assess flow in the true and false lumens of the aorta. This promotes potential future work on functional assessment of aortic dissection hemodynamics.

EFFECTIVE ORIFICE AREA BY CARDIAC MAGNETIC RESONANCE FOR THE FUNCTIONAL ASSESSMENT OF BIOPROSTHETIC AORTIC VALVES

Effective orifice area (EOA) is the current practice for prosthetic valve functional evaluation. We hypothesized that phase contrast (PC) methods could be employed to describe the dynamic EOA, and compared to Doppler-derived EOA in patients with bioprosthetic aortic valves. We retrospectively

Bioprosthetic Mitral Valve Effective Orifice Area Using 4D Flow Cardiac Magnetic Resonance Derived Time Velocity Integral. An In-Vitro Comparison with Doppler Echocardiography

\Background 4D Flow Cardiac Magnetic Resonance (CMR) is a novel imaging modality to assess bioprosthetic mitral valve (BMV) function. We describe a new, 4D Flow derived velocity time integral (TVI) based method to assess effective orifice area (EOA) for BMVs. Methods In our MRI-compatible circulatory loop 4 stented porcine BMVs (27, 29, 31, 33mm) underwent CMR with a 1.5T Siemens scanner. The valves were evaluated at forward stroke volumes of 70, 90 and 110ml at a beat rate of 70bpm. We plotted instantaneous peak velocities and calculated TVI for each scenario. 4D CMR-EOA was

Bioprosthetic mitral valve effective orifice area by phase-contrast CMR. An in vitro comparison with Doppler echocardiography

Background Introduction: Current guidelines for the functional evaluation of bioprosthetic heart valves recommend the effective orifice area (EOA) as the product of the transvalvular stroke volume divided by Doppler derived diastolic time velocity integral (TVI). Phase contrast CMR may offer an alternative imaging modality to assess bioprosthetic valve EOA when Doppler methods are technically limited or unreliable. Methods Our circulatory loop includes a mock ventricle and a heart valve imaging chamber that has been fabricated using MRI-compatible components. In this study 3 different sized stented porcine mitral valve bioprostheses were evaluated (27 mm, 29 mm, 31 mm) replicating three different hemodynamic conditions with forward stroke volume of 70 ml, 90 ml and 110 ml respectively at a beat rate of 70 bpm. Imaging was performed with a

DEVELOPMENT OF A MULTI-MODALITY IMAGING MODEL OF DYNAMIC MITRAL VALVE DYSFUNCTION

A robust, controlled in vitro model of mitral valve regurgitation (MR) would facilitate the exploration of MR repair techniques and provide a reference test environment for the validation of new imaging applications – including 3D Doppler and phase contrast CMR. Design software, 3D printing