Elliott M. Groves

The Effects of Transcatheter Valve Crimping on Pericardial Leaflets

BACKGROUND Transcatheter aortic valve replacement has emerged as a promising therapy for treatment of severe aortic stenosis. Although it has been shown that these valves can be safely delivered and implanted, studies of valve longevity are lacking because of the infancy of the technology. Particularly, the effects of stent crimping on the valves leaflets have not yet been sufficiently investigated. In this study, we have characterized the effects of crimping on pericardial leaflets in time and through the depth of the tissue. METHODS To test the structural changes at the surface and deep layers of bovine pericardial leaflets, scanning electron microscopy and second-harmonic generation microscopy were used. An uncrimped tissue sample was imaged, followed by imaging a segment of tissue after crimping in a stented transcatheter valve, immediately after, at 20 minutes, and 60 minutes after crimping. The crimping experiment was performed for multiple crimping sizes (ie, 14F, 16F, and 18F). We defined a damage index that quantifies the level of leaflet structural changes as a result of crimping. RESULTS Based on the calculated damage indices and analyses of the raw images, it was determined that crimping does measurable damage to the leaflet tissue that persists with time. CONCLUSIONS Significant tissue damage was observed at the surface layers of the leaflets. In the deeper tissue layers, damage was substantial for 14F crimping; however, it became less significant but still visible for larger collapse profiles. Crimping may induce substantial structural damage to pericardial leaflets that does not improve with time.

Emerging Trends in Heart Valve Engineering: Part I. Solutions for Future

As the first section of a multi-part review series, this section provides an overview of the ongoing research and development aimed at fabricating novel heart valve replacements beyond what is currently available for patients. Here we discuss heart valve replacement options that involve a biological component or process for creation, either in vitro or in vivo (tissue-engineered heart valves), and heart valves that are fabricated from polymeric material that are considered permanent inert materials that may suffice for adults where growth is not required. Polymeric materials provide opportunities for cost-effective heart valves that can be more easily manufactured and can be easily integrated with artificial heart and ventricular assist device technologies. Tissue engineered heart valves show promise as a regenerative patient specific model that could be the future of all valve replacement. Because tissue-engineered heart valves depend on cells for their creation, understanding how cells sense and respond to chemical and physical stimuli in their microenvironment is critical and therefore, is also reviewed.

Effects of weekend admission on the outcomes and management of ruptured aortic aneurysms

OBJECTIVE Ruptured aortic aneurysm is a condition with a high rate of mortality that requires prompt surgical intervention. It has been noted that in some conditions requiring such prompt intervention, in-hospital mortality is increased in patients admitted on the weekends compared with patients admitted on weekdays. We sought to determine if this was indeed the case for both ruptured thoracic aortic aneurysms (TAA) and abdominal aortic aneurysms (AAA) and to elucidate the possible reasons. METHODS Using the Nationwide Inpatient Sample, a publicly available database of inpatient care, we analyzed the incidence of mortality among 7200 patients admitted on the weekends compared with weekdays for ruptured aortic aneurysm. Among these patients, 19% had a TAA and 81% had an AAA, and each group was analyzed for differences in mortality during the hospitalization. We adjusted for demographics, comorbid conditions, hospital characteristics, rates of surgical intervention, timing of surgical intervention, and use of additional therapeutic measures. RESULTS Patients admitted on the weekend for both ruptured TAA and AAA had a statistically significant increase in mortality compared with those admitted on the weekdays (TAA: odds ratio, 2.55; 95% confidence interval, 1.77-3.68; P = .03; AAA: odds ratio, 1.32; 95% confidence interval, 1.13-1.55; P = .0004). Among those with TAA, a surgical intervention was performed on day of admission in 62.1% of weekday admissions vs 34.9% of weekend admissions (P < .0001). This difference was much smaller among those with an aortic aneurysm; 79.6% had a surgical intervention on day of admission on a weekday vs 77.2% on the weekend (P < .0001). CONCLUSIONS Weekend admission for ruptured aortic aneurysm is associated with an increased mortality compared with admission on a weekday, and this is likely due to several factors including a delay in prompt surgical intervention.

The Effects of Positioning of Transcatheter Aortic Valves on Fluid Dynamics of the Aortic Root

Transcatheter aortic valve implantation is a novel treatment for severe aortic valve stenosis. Due to the recent use of this technology and the procedural variability, there is very little data that quantify the hemodynamic consequences of variations in valve placement. Changes in aortic wall stresses and fluid retention in the sinuses of Valsalva can have a significant effect on the clinical response a patient has to the procedure. By comprehensively characterizing complex flow in the sinuses of Valsalva using digital particle image velocimetry and an advanced heart-flow simulator, various positions of a deployed transcatheter valve with respect to a bioprosthetic aortic valve (valve-in-valve) were tested in vitro. Displacements of the transcatheter valve were axial and directed below the simulated native valve annulus. It was determined that for both blood residence time and aortic Reynolds stresses, it is optimal to have the annulus of the transcatheter valve deployed as close to the aortic valve annulus as possible.

Emerging Trends in Heart Valve Engineering: Part IV. Computational Modeling and Experimental Studies

In this final portion of an extensive review of heart valve engineering, we focus on the computational methods and experimental studies related to heart valves. The discussion begins with a thorough review of computational modeling and the governing equations of fluid and structural interaction. We then move onto multiscale and disease specific modeling. Finally, advanced methods related to in vitro testing of the heart valves are reviewed. This section of the review series is intended to illustrate application of computational methods and experimental studies and their interrelation for studying heart valves.

Changes in mortality on weekend versus weekday admissions for Acute Coronary Syndrome in the United States over the past decade

BACKGROUND We assessed in-hospital mortality and utilization of invasive cardiac procedures following Acute Coronary Syndrome (ACS) admissions on the weekend versus weekdays over the past decade in the United States. METHODS We used data from the Nationwide Inpatient Survey (2001-2011) to examine differences in all-cause in-hospital mortality between patients with a principal diagnosis of ACS admitted on a weekend versus a weekday. Adjusted and hierarchical logistic regression model analysis was then used to identify if weekend admission was associated with a decreased utilization of procedural interventions and increased subsequent complications as well. RESULTS 13,988,772 ACS admissions were identified. Adjusted mortality was higher for weekend admissions for Non-ST-Elevation Acute Coronary Syndromes [OR: 1.15, 95% CI, 1.14-1.16] and only somewhat higher for ST-Elevation Myocardial Infarction [OR: 1.03; 95% CI, 1.01-1.04]. Additionally, patients were significantly less likely to receive coronary revascularization intervention/therapy on their first day of admission [OR: 0.97, 95% CI: 0.96-0.98 and OR: 0.75, 95% CI: 0.75-0.75 for STEMI and NSTE-ACS respectively]. For ACS patients admitted during the weekend who underwent procedural interventions, in-hospital mortality and complications were higher as compared to patients undergoing the same procedures on weekdays. CONCLUSION For ACS patients, weekend admission is associated with higher mortality and lower utilization of invasive cardiac procedures, and those who did undergo these interventions had higher rates of mortality and complications than their weekday counterparts. This data leads to the possible conclusion that access to diagnostic/interventional procedures may be contingent upon the day of admission, which may impact mortality.

Invasive Testing for Coronary Artery Disease : FFR, IVUS, OCT, NIRS

Coronary angiography is the gold standard for the diagnosis of coronary artery disease and guides revascularization strategies. The emergence of new diagnostic modalities has provided clinicians with adjunctive physiologic and image-based data to help formulate treatment strategies. Fractional flow reserve can predict whether percutaneous intervention will benefit a patient. Intravascular ultrasonography and optical coherence tomography are intracoronary imaging modalities that facilitate the anatomic visualization of the vessel lumen and characterize plaques. Near-infrared spectroscopy can characterize plaque composition and potentially provide valuable prognostic information. This article reviews the indications, basic technology, and supporting clinical studies for these modalities.

Emerging Trends in Heart Valve Engineering: Part III. Novel Technologies for Mitral Valve Repair and Replacement

In this portion of an extensive review of heart valve engineering, we focus on the current and emerging technologies and techniques to repair or replace the mitral valve. We begin with a discussion of the currently available mechanical and bioprosthetic mitral valves followed by the rationale and limitations of current surgical mitral annuloplasty methods; a discussion of the technique of neo-chordae fabrication and implantation; a review the procedures and clinical results for catheter-based mitral leaflet repair; a highlight of the motivation for and limitations of catheter-based annular reduction therapies; and introduce the early generation devices for catheter-based mitral valve replacement.

Invasive Testing for Coronary Artery Disease: FFR, IVUS, OCT, NIRS

Coronary angiography is the gold standard for the diagnosis of coronary artery disease and guides revascularization strategies. The emergence of new diagnostic modalities has provided clinicians with adjunctive physiologic and image-based data to help formulate treatment strategies. Fractional flow reserve can predict whether percutaneous intervention will benefit a patient. Intravascular ultrasonography and optical coherence tomography are intracoronary imaging modalities that facilitate the anatomic visualization of the vessel lumen and characterize plaques. Near-infrared spectroscopy can characterize plaque composition and potentially provide valuable prognostic information. This article reviews the indications, basic technology, and supporting clinical studies for these modalities.

Functional Assessment of Coronary Artery Disease Using Whole-Heart Dynamic Computed Tomographic PerfusionCLINICAL PERSPECTIVE

Background—Computed tomographic (CT) angiography is an important tool for the evaluation of coronary artery disease but often correlates poorly with myocardial ischemia. Current dynamic CT perfusion techniques can assess ischemia but have limited accuracy and deliver high radiation dose. Therefore, an accurate, low-dose, dynamic CT perfusion technique is needed. Methods and Results—A total of 20 contrast-enhanced CT volume scans were acquired in 5 swine (40±10 kg) to generate CT angiography and perfusion images. Varying degrees of stenosis were induced using a balloon catheter in the proximal left anterior descending coronary artery, and a pressure wire was used for reference fractional flow reserve (FFR) measurement. Perfusion measurements were made with only 2 volume scans using a new first-pass analysis (FPA) technique and with 20 volume scans using an existing maximum slope model (MSM) technique. Perfusion (P) and FFR measurements were related by PFPA=1.01 FFR−0.03 (R2=0.85) and PMSM=1.03 FFR−0.03 (R2=0.80) for FPA and MSM techniques, respectively. Additionally, the effective radiation doses were calculated to be 2.64 and 26.4 mSv for FPA and MSM techniques, respectively. Conclusions—A new FPA-based dynamic CT perfusion technique was validated in a swine animal model. The results indicate that the FPA technique can potentially be used for improved anatomical and functional assessment of coronary artery disease at a relatively low radiation dose.