Is Concomitant Mitral Stenosis Associated With Worse Outcomes in Patients Who Underwent TAVR? Insights from a National Database.

Concomitant mitral stenosis (MS) is present in 10% to 15% of all patients who underwent transcatheter aortic valve replacement (TAVR). Our aim is to assess outcomes of TAVR in patients with MS using a national database. The Nationwide Inpatient Sample database was used to identify patients who underwent TAVR from 2015 to 2020. We created 2 groups, patients with and those without MS. We then compared baseline characteristics, demographics, and in-hospital outcomes of the groups. Primary outcomes were in-hospital mortality, acute respiratory failure, and pacemaker placement. Secondary outcomes were length of stay and in-hospital costs. Our study indicates that patients with MS had greater incidence of acute respiratory failure (8.8% vs 4.89%, p = 0.001), complete heart block (13.54% vs 9.36%, p = 0.01), and permanent pacemaker placement (8.03% vs 6.03%, p = 0.05). In-hospital mortality was greater in the MS group; however, it was not statistically significant (1.32% vs 1.53%, p = 0.679).

Clinical Profile of Tension Type Headache in a Medical College with Special Emphasis on Triggering Factors.

Background and Objectives: Tension type headache is one of the costliest primary headaches which can cause a significant impact on an individual's life. Healthcare professionals are exposed to multiple trigger factors which give rise to an increase in headache frequency, most notable reasons being sleep disturbances, stress and untimely food habits. With this background, we conducted this study of detailed clinical profile and trigger factors among the 2050 subjects (MBBS students: 909, BDS students: 323, nursing students: 268, postgraduates students and staff: 550) in our medical institute. Materials and Methods: Subjects were given questionnaires on headache and were instructed to give the details of their clinical symptoms along with relevant questions on trigger factors. The assessment tools used were the Visual Analogue Scale (VAS) and Migraine Disability Assessment Scale (MIDAS). Results: Out of 2050 subjects, 464 patients suffered from tension type headache. Overall prevalence of tension type headache was 22.6%. Prevalence was higher in females (57.9%) as compared to males (42.1%). Headache experienced by majority of the student population was unilateral (31.4%), pulsating type (51.6%) and of moderate intensity (77.1%). Common associated symptoms were nausea associated with other factors (40%) and photophobia and phonophobia (18.6%). Stress (72.1%) and decreased sleep (49.4%) were the most common triggering factors. Practice of self-medication was reported by 80.2% of subjects. Conclusion: Our study noted a high frequency of trigger factors in medical professionals, the most common triggering factors being stress and disturbed sleep. To our knowledge this is the first large study to evaluate headache and specifically tension type headache among medical professionals.

Declining Trend of Transapical Access for Transcatheter Aortic Valve Replacement in Patients with Aortic Stenosis.

Introduction: The last decade has witnessed major evolution and shifts in the use of transcatheter aortic valve replacement (TAVR) for severe aortic stenosis (AS). Included among the shifts has been the advent of alternative access sites for TAVR. Consequently, transapical access (TA) has become significantly less common. This study analyzes in detail the trend of TA access for TAVR over the course of 7 years. Methods: The national inpatient sample database was reviewed from 2011-2017 and patients with AS were identified by using validated ICD 9-CM and ICD 10-CM codes. Patients who underwent TAVR through TA access were classified as TA-TAVR, and any procedure other than TA access was classified as non-TA-TAVR. We compared the yearly trends of TA-TAVR to those of non-TA-TAVR as the primary outcome. Results: A total of 3,693,231 patients were identified with a diagnosis of AS. 129,821 patients underwent TAVR, of which 10,158 (7.8%) underwent TA-TAVR and 119,663 (92.2%) underwent non-TA-TAVR. After peaking in 2013 at 27.7%, the volume of TA-TAVR declined to 1.92% in 2017 (p < 0.0001). Non-TA-TAVR started in 2013 at 72.2% and consistently increased to 98.1% in 2017. In-patient mortality decreased from a peak of 5.53% in 2014 to 3.18 in 2017 (p=0.6) in the TA-TAVR group and from a peak of 4.51% in 2013 to 1.24% in 2017 (p=0.0001) in the non-TA-TAVR group. Conclusion: This study highlights a steady decline in TA access for TAVR, higher inpatient mortality, increased length of stay, and higher costs compared to non-TA-TAVR.

Comparison of Suture-Based and Collagen-Based Vascular Closure Devices for Large Bore Arteriotomies-A Meta-Analysis of Bleeding and Vascular Outcomes.

BACKGROUND: Large bore access procedures rely on vascular closure devices to minimize access site complications. Suture-based vascular closure devices (S-VCD) such as ProGlide and ProStar XL have been readily used, but recently, newer generation collagen-based vascular closure devices (C-VCD) such as MANTA have been introduced. Data on comparisons of these devices are limited. METHODS: PubMed, Scopus and Cochrane were searched for articles on vascular closure devices using keywords, ("Vascular closure devices" OR "MANTA" OR "ProStar XL" OR "ProGlide") AND ("outcomes") that resulted in a total of 875 studies. Studies were included if bleeding or vascular complications as defined by Valve Academic Research Consortium-2 were compared between the two types of VCDs. The event level data were pooled across trials to calculate the Odds Ratio (OR) with 95% CI, and analysis was done with Review Manager 5.4 using random effects model. RESULTS: Pooled analyses from these nine studies resulted in a total of 3410 patients, out of which 2855 were available for analysis. A total of 1229 received C-VCD and 1626 received S- VCD. Among the patients who received C-VCD, the bleeding complications (major and minor) were similar to patients who received S-VCD ((OR: 0.70 (0.35-1.39), p = 0.31, I2 = 55%), OR: 0.92 (0.53-1.61), p = 0.77, I2 = 65%)). The vascular complications (major and minor) in patients who received C-VCD were also similar to patients who received S-VCD ((OR: 1.01 (0.48-2.12), p = 0.98, I2 = 52%), (OR: 0.90 (0.62-1.30), p = 0.56, I2 = 35%)). CONCLUSIONS: Bleeding and vascular complications after large bore arteriotomy closure with collagen-based vascular closure devices are similar to suture-based vascular closure devices.

Magnetic resonance conditionality of abandoned leads from active implantable medical devices at 1.5 T.

PURPOSE: During MR scans, abandoned leads from active implantable medical devices (AIMDs) can experience excessive heating at the lead tip, depending on the type of termination applied to the proximal contacts (proximal end treatment). The influence of different proximal end treatments (ie, [1] freely exposed in the tissue, [2] terminated with metal in contact with the tissue, or [3] capped with plastic, and thereby fully insulated, on the RF-induced lead-tip heating) are studied. A technique to ensure that MR Conditional AIMD leads remain MR Conditional even when abandoned is recommended. METHODS: Abandoned leads from three MR Conditional AIMDs ([1] a sacral neuromodulation system, [2] a cardiac rhythm management pacemaker system, and [3] a deep brain stimulator system) were investigated in this study. The computational lead models (ie, the transfer functions) for different proximal end treatments were measured and used to assess the in vivo lead-tip heating for four virtual human models (FATS, Duke, Ella, and Billie) and compared with the lead-tip heating of the complete MR Conditional AIMD system. RESULT: The average and maximum lead-tip heating for abandoned leads proximally capped with metal is always lower than that from the complete AIMD system. Abandoned leads proximally insulated could lead to an average in vivo temperature rise up to 3.5 times higher than that from the complete AIMD system. CONCLUSION: For the three investigated AIMDs under 1.5T MR scanning, our results indicate that RF-induced lead-tip heating of abandoned leads strongly depends on the proximal lead termination. A metallic cap applied to the proximal termination of the tested leads could significantly reduce the RF-induced lead-tip heating.

Wireless Power Harvesting During MRI.

We present methods to harvest wireless power directly from the MRI RF field. The system includes a harvester coil to capture RF energy and an RF-DC converter for rectification. Energy harvesting by the harvester coil is modeled as a function of the MRI B1 RF field. Rectification is modeled using power-dependent large signal S-parameter simulation. A novel reference impedance-based modeling approach is leveraged to cascade models for linear inductive coupling and nonlinear diode rectification, and validated. The method permits independent optimization of harvester coils and RF-DC converters to maximize harvesting efficiency. Feasibility of this technique is demonstrated by implementing concurrent in-bore wireless power harvesting and MRI scanning on a clinical system. The effect of artifacts on image quality is also investigated.Clinical Relevance- In-bore wireless harvesting can provide power for medical accessories during MRI, with minimal system modification and cost.

Modeling Endovascular MRI Coil Coupling With Transmit RF Excitation.

OBJECTIVE: To model inductive coupling of endovascular coils with transmit RF excitation for selecting coils for MRI-guided interventions. METHODS: Independent and computationally efficient FEM models are developed for the endovascular coil, cable, transmit excitation, and imaging domain. Electromagnetic and circuit solvers are coupled to simulate net B1 + fields and induced currents and voltages. Our models are validated using the Bloch-Siegert B1 + mapping sequence for a series-tuned multimode coil, capable of tracking, wireless visualization, and high-resolution endovascular imaging. RESULTS: Validation shows good agreement at 24-, 28-, and 34-µT background RF excitation within experimental limitations. Quantitative coil performance metrics agree with simulation. A parametric study demonstrates tradeoff in coil performance metrics when varying number of coil turns. Tracking, imaging, and wireless marker multimode coil features and their integration is demonstrated in a pig study. CONCLUSION: Developed models for the multimode coil were successfully validated. Modeling for geometric optimization and coil selection serves as a precursor to time consuming and expensive experiments. Specific applications demonstrated include parametric optimization, coil selection for a cardiac intervention, and an animal imaging experiment. SIGNIFICANCE: Our modular, adaptable, and computationally efficient modeling approach enables rapid comparison, selection, and optimization of inductively coupled coils for MRI-guided interventions.

Eight channel transmit array volume coil using on-coil radiofrequency current sources.

BACKGROUND: At imaging frequencies associated with high-field MRI, the combined effects of increased load-coil interaction and shortened wavelength results in degradation of circular polarization and B1 field homogeneity in the imaging volume. Radio frequency (RF) shimming is known to mitigate the problem of B1 field inhomogeneity. Transmit arrays with well decoupled transmitting elements enable accurate B1 field pattern control using simple, non-iterative algorithms. METHODS: An eight channel transmit array was constructed. Each channel consisted of a transmitting element driven by a dedicated on-coil RF current source. The coil current distributions of characteristic transverse electromagnetic (TEM) coil resonant modes were non-iteratively set up on each transmitting element and 3T MRI images of a mineral oil phantom were obtained. RESULTS: B1 field patterns of several linear and quadrature TEM coil resonant modes that typically occur at different resonant frequencies were replicated at 128 MHz without having to retune the transmit array. The generated B1 field patterns agreed well with simulation in most cases. CONCLUSIONS: Independent control of current amplitude and phase on each transmitting element was demonstrated. The transmit array with on-coil RF current sources enables B1 field shimming in a simple and predictable manner.

In vivo imaging and spectroscopy of dynamic metabolism using simultaneous 13C and 1H MRI.

Hyperpolarized (HP) (13)C-labeled pyruvate studies with magnetic resonance (MR) have been used to observe the kinetics of metabolism in vivo. Kinetic modeling to measure metabolic rates in vivo is currently limited because of nonspecific hyperpolarized signals mixing between vascular, extravascular, and intracellular compartments. In this study, simultaneous acquisition of both (1)H and (13)C signals after contrast agent injection is used to resolve specific compartments to improve the accuracy of the modeling. We demonstrate a novel technique to provide contrast to the intracellular compartments by sequential injection of HP [1-(13)C] pyruvate followed by gadolinium-chelate to provide T(1)-shortening to extra-cellular compartments. A kinetic model that distinguishes the intracellular space and includes the T(1)-shortening effect of the gadolinium chelate can then be used to directly measure the intracellular (13)C kinetics.

Multimode intravascular RF coil for MRI-guided interventions.

PURPOSE: To demonstrate the feasibility of using a single intravascular radiofrequency (RF) probe connected to the external magnetic resonance imaging (MRI) system via a single coaxial cable to perform active tip tracking and catheter visualization and high signal-to-noise ratio (SNR) intravascular imaging. MATERIALS AND METHODS: A multimode intravascular RF coil was constructed on a 6F balloon catheter and interfaced to a 1.5T MRI scanner via a decoupling circuit. Bench measurements of coil impedances were followed by imaging experiments in saline and phantoms. RESULTS: The multimode coil behaves as an inductively coupled transmit coil. The forward-looking capability of 6 mm was measured. A greater than 3-fold increase in SNR compared to conventional imaging using optimized external coil was demonstrated. Simultaneous active tip tracking and catheter visualization was demonstrated. CONCLUSION: It is feasible to perform 1) active tip tracking, 2) catheter visualization, and 3) high SNR imaging using a single multimode intravascular RF coil that is connected to the external system via a single coaxial cable.

Radiofrequency current source (RFCS) drive and decoupling technique for parallel transmit arrays using a high-power metal oxide semiconductor field-effect transistor (MOSFET).

A radiofrequency current source (RFCS) design using a high-power metal oxide semiconductor field effect transistor (MOSFET) that enables independent current control for parallel transmit applications is presented. The design of an RFCS integrated with a series tuned transmitting loop and its associated control circuitry is described. The current source is operated in a gated class AB push-pull configuration for linear operation at high efficiency. The pulsed RF current amplitude driven into the low impedance transmitting loop was found to be relatively insensitive to the various loaded loop impedances ranging from 0.4 to 10.3 ohms, confirming current mode operation. The suppression of current induced by a neighboring loop was quantified as a function of center-to-center loop distance, and was measured to be 17 dB for nonoverlapping, adjacent loops. Deterministic manipulation of the B(1) field pattern was demonstrated by the independent control of RF phase and amplitude in a head-sized two-channel volume transmit array. It was found that a high-voltage rated RF power MOSFET with a minimum load resistance, exhibits current source behavior, which aids in transmit array design.

TEM transmission line coil with double nuclear capability.

MR imaging and spectroscopy requires RF fields of high homogeneity. Quadrature volume coils meeting this requirement include the birdcage coil and the TEM resonator. We describe here a quadrature volume coil designed around a modified coaxial transmission line in which multiple inner conductors are arrayed on a circular perimeter and surrounded by a common shield. Current antinodes are established at appropriate points on the inner conductors by series transmission line stubs, either open circuit or short circuit, which terminate the line. Quadrature phasing is generated by a novel circuit constructed from a pair of high-performance current baluns and a commercial quadrature hybrid. The coil is a "pure" TEM coil as it is simply a resonant transmission line. There is no mode structure to consider. The construction of a prototype quadrature four-element coil is described and preliminary test results from this coil in a 4.7T horizontal bore magnet are reported. A related double nuclear coil design for (3)He and (1)H in which two linear transmission line coils are arrayed on a circular perimeter and simultaneously tuned and matched to their respective frequencies is also described. Preliminary tests from this coil in a 1.5T clinical scanner are reported.