Elimination of Transcoarctation Pressure Gradients Has No Impact on Left Ventricular Function or Aortic Shear Stress After Intervention in Patients With Mild Coarctation

Objectives: This study sought to investigate the impact of transcatheter intervention on left ventricular function and aortic hemodynamics in patients with mild coarctation of the aorta (COA). Background: The optimal method and timing of transcatheter intervention for COA remains unclear, especially when the severity of COA is mild (peak-to-peak transcoarctation pressure gradient  < 20 mm Hg). Debate rages regarding the risk/benefit ratio of intervention versus long-term effects of persistent minimal gradient in this heterogeneous population with differing blood pressures, ventricular function, and peripheral perfusion. Methods: We developed a unique computational fluid dynamics and lumped parameter modeling framework based on patient-specific hemodynamic input parameters and validated it against patient-specific clinical outcomes (before and after intervention). We used clinically measured hemodynamic metrics and imaging of the aorta and the left ventricle in 34 patients with mild COA to make these correlations. Results: Despite dramatic reduction in the transcoarctation pressure gradient (catheter and Doppler echocardiography pressure gradients reduced by 75% and 47.3%, respectively), there was only modest effect on aortic flow and no significant impact on aortic shear stress (the maximum time-averaged wall shear stress in descending aorta was reduced 5.1%). In no patient did transcatheter intervention improve left ventricular function (e.g., stroke work and normalized stroke work were reduced by only 4.48% and 3.9%, respectively). Conclusions: Transcatheter intervention that successfully relieves mild COA pressure gradients does not translate to decreased myocardial strain. The effects of the intervention were determined to the greatest degree by ventricular–vascular coupling hemodynamics and provide a novel valuable mechanism to evaluate patients with COA that may influence clinical practice. Key Words: aortic hemodynamics, left ventricle function, mild coarctation, peak-to-peak pressure gradient, transcatheter interventionNational Institute of Mental Health (U.S.) (R01 GM 49039)American Heart Association (Postdoctoral Fellowship 16POST26420039

Aortic regurgitation assessment by cardiovascular magnetic resonance imaging and transthoracic echocardiography: intermodality disagreement impacting on prediction of post-surgical left ventricular remodeling

Transthoracic echocardiography (TTE) is the primary clinical imaging modality for the assessment of patients with isolated aortic regurgitation (AR) in whom TTE’s linear left ventricular (LV) dimension is used to assess disease severity to guide aortic valve replacement (AVR), yet TTE is relatively limited with regards to its integrated semi-quantitative/qualitative approach. We therefore compared TTE and cardiovascular magnetic resonance (CMR) assessment of isolated AR and investigated each modality’s ability to predict LV remodeling after AVR. AR severity grading by CMR and TTE were compared in 101 consecutive patients referred for CMR assessment of chronic AR. LV end-diastolic diameter and end-systolic diameter measurements by both modalities were compared. Twenty-four patients subsequently had isolated AVR. The pre-AVR estimates of regurgitation severity by CMR and TTE were correlated with favorable post-AVR LV remodeling. AR severity grade agreement between CMR and TTE was moderate (ρ = 0.317, P = 0.001). TTE underestimated CMR LV end-diastolic and LV end-systolic diameter by 6.6 mm (P < 0.001, CI 5.8–7.7) and 5.9 mm (P < 0.001, CI 4.1–7.6), respectively. The correlation of post-AVR LV remodeling with CMR AR grade (ρ = 0.578, P = 0.004) and AR volumes (R = 0.664, P < 0.001) was stronger in comparison to TTE (ρ = 0.511, P = 0.011; R = 0.318, P = 0.2). In chronic AR, CMR provides more prognostic relevant information than TTE in assessing AR severity. CMR should be considered in the management of chronic AR patients being considered for AVR

Optimized Computer-Aided Segmentation and Three-Dimensional Reconstruction Using Intracoronary Optical Coherence Tomography

We present a novel and time-efficient method for intracoronary lumen detection, which produces three-dimensional (3-D) coronary arteries using optical coherence tomographic (OCT) images. OCT images are acquired for multiple patients and longitudinal cross-section (LOCS) images are reconstructed using different acquisition angles. The lumen contours for each LOCS image are extracted and translated to 2-D cross-sectional images. Using two angiographic projections, the centerline of the coronary vessel is reconstructed in 3-D, and the detected 2-D contours are transformed to 3-D and placed perpendicular to the centerline. To validate the proposed method, 613 manual annotations from medical experts were used as gold standard. The 2-D detected contours were compared with the annotated contours, and the 3-D reconstructed models produced using the detected contours were compared to the models produced by the annotated contours. Wall shear stress (WSS), as dominant hemodynamics factor, was calculated using computational fluid dynamics and 844 consecutive 2-mm segments of the 3-D models were extracted and compared with each other. High Pearson's correlation coefficients were obtained for the lumen area (r = 0.98) and local WSS (r = 0.97) measurements, while no significant bias with good limits of agreement was shown in the Bland-Altman analysis. The overlapping and nonoverlapping areas ratio between experts' annotations and presented method was 0.92 and 0.14, respectively. The proposed computer-aided lumen extraction and 3-D vessel reconstruction method is fast, accurate, and likely to assist in a number of research and clinical applications

Ventricular stroke work and vascular impedance refine the characterization of patients with aortic stenosis

Aortic stenosis (AS) management is classically guided by symptoms and valvular metrics. However, the natural history of AS is dictated by coupling of the left ventricle, aortic valve, and vascular system. We investigated whether metrics of ventricular and vascular state add to the appreciation of AS state above valve gradient alone. Seventy patients with severe symptomatic AS were prospectively followed from baseline to 30 days after transcatheter aortic valve replacement (TAVR). Quality of life (QOL) was assessed using the Kansas City Cardiomyopathy Questionnaire. Left ventricular stroke work (SW[subscript LV]) and vascular impedance spectrums were calculated noninvasively using in-house models based on central blood pressure waveforms, along with hemodynamic parameters from echocardiograms. Patients with higher preprocedural SW[subscript LV] and lower vascular impedance were more likely to experience improved QOL after TAVR. Patients fell into two categories: those who did and those who did not exhibit increase in blood pressure after TAVR. In patients who developed hypertension (19%), vascular impedance increased and SW[subscript LV] remained unchanged (impedance at zeroth harmonic: Z[subscript 0], from 3964.4 to 4851.8 dyne·s/cm[superscript 3], P = 0.039; characteristic impedance: Z[subscript c], from 376.2 to 603.2 dyne·s/cm[superscript 3], P = 0.033). SW[subscript LV] dropped only in patients who did not develop new hypertension after TAVR (from 1.58 to 1.26 J; P < 0.001). Reduction in valvular pressure gradient after TAVR did not predict change in SW[subscript LV] (r = 0.213; P = 0.129). Reduction of SW[subscript LV] after TAVR may be an important metric in management of AS, rather than relying solely on the elimination of transvalvular pressure gradients