Single- and dual-site ventricular pacing entirely through the coronary sinus for patients with prior tricuspid valve surgery.

PURPOSE: Transvenous right ventricular pacing has traditionally been avoided after surgical tricuspid valve repair or replacement because of possible valvular dysfunction. Epicardial pacing has been used but it requires surgical thoracotomy and has higher lead failure rates when compared to transvenous pacing. We evaluated the lead stability and clinical outcomes in patients with isolated coronary sinus (CS) lead due to relative contraindication to transvenous pacing from prior tricuspid valve (TV) surgery. METHODS: We retrospectively examined a single-center cohort of 34 patients with TV disease and/or surgery who underwent permanent pacemaker implantation with a left ventricular CS lead as the only ventricular pacing lead (to avoid crossing the TV). The clinical outcome, echocardiographic data, and pacing thresholds were evaluated at follow-up. RESULTS: We implanted 19 patients with a single-CS lead and 15 patients with dual-CS leads. The average left ventricular ejection fraction was 56 ± 13% prior to lead implantation and remained stable at 2-year follow-up. The tricuspid regurgitation remained mild at follow-up. The average lead pacing threshold was 1.2 ± 0.6 V × ms at implant and 1.1 ± 0.4 V × ms at 2-year follow-up (P = 0.39). For patients with dual-CS leads, the pacing threshold was 1.2 ± 0.7 V × ms at implant and 1.1 ± 0.5 V × ms at 2-year follow-up (P = 0.52). CONCLUSIONS: The use of ventricular pacing entirely through the CS is an effective and minimally invasive method that provides stable pacing for patients with prior TV surgery in whom transvenous lead placement either is not possible or is relatively contraindicated.

Exploring the DBR superlattice effect on the thermal performance of a VECSEL with the finite element method.

The design criterion of thermal conductivity for the GaAs/AlAs distributed Bragg reflector (DBR) superlattice structure was thoroughly investigated to precisely analyze the thermal behaviors of the optically pumped vertically external cavity surface-emitting laser (VECSEL). A finite element model with detailed configuration of a VECSEL gain chip was constructed to fulfill the analysis. A 1060 nm VECSEL with different pump conditions was further demonstrated to verify the finite element analysis. At the VECSEL thermal rollover point, the analysis results show that the model with the superlattice property predicts more precise temperature values than that using a bulk composite property. It reveals that the accurate determination of the thermal conductivity of the DBR superlattice is significantly important for the VECSEL thermal analysis.

Sinus of Valsalva Pseudoaneurysm as a Sequela to Infective Endocarditis.

Pseudoaneurysm is an uncommon sequela of infective endocarditis. We treated a 44-year-old man who had an active case of group B streptococcal infective endocarditis of the aortic valve despite no evidence of valvular dysfunction or vegetation on his initial transesophageal echocardiogram. After completing 6 weeks of intravenous antibiotic therapy, the patient developed a sinus of Valsalva pseudoaneurysm and severe aortic regurgitation caused by partial detachment of the left coronary cusp. We used a pericardial patch to close the pseudoaneurysm and repair the coronary cusp. This case shows the importance of routine clinical follow-up evaluation in infective endocarditis, even after completion of antibiotic therapy. Late sequelae associated with infective endocarditis or its therapy include recurrent infection, heart failure caused by valvular dysfunction (albeit delayed), and antibiotic toxicity such as aminoglycoside-induced nephropathy and vestibular toxicity.

Bonding and impedance matching of acoustic transducers using silver epoxy.

Silver epoxy was selected to bond transducer plates on glass substrates. The properties and thickness of the bonding medium affect the electrical input impedance of the transducer. Thus, the thickness of the silver epoxy bonding layer was used as a design parameter to optimize the structure for the transducer input impedance to match the 50 Ω output impedance of most radio frequency (RF) generators. Simulation and experimental results show that nearly perfect matching is achieved without using any matching circuit. At the matching condition, the transducer operates at a frequency band a little bit below the half-wavelength resonant frequency of the piezoelectric plate. In experiments, lead titanate (PT) piezoelectric plates were employed. Both full-size, 11.5 mm × 2 mm × 0.4 mm, and half-size, 5.75 mm × 2 mm × 0.4 mm, can be well matched using optimal silver epoxy thickness. The transducer assemblies demonstrate high efficiency. The conversion loss from electrical power to acoustic power in soda-lime glass is 4.3 dB. This loss is low considering the fact that the transducers operate at off-resonance by 12%. With proper choice of silver epoxy thickness, the transducer can be matched at the fundamental, the 3rd and 5th harmonic frequencies. This leads to the possible realization of triple-band transducers. Reliability was assessed with thermal cycling test according to Telcordia GR-468-Core recommendation. Of the 30 transducer assemblies tested, none broke until 2900 cycles and 27 have sustained beyond 4050 cycles.

Input impedance matching of acoustic transducers operating at off-resonant frequencies.

The input impedance matching technique of acoustic transducers at off-resonant frequencies is reported. It uses an inherent impedance property of transducers and thus does not need an external electric matching circuit or extra acoustic matching section. The input electrical equivalent circuit includes a radiation component and a dielectric capacitor. The radiation component consists of a radiation resistance and a radiation reactance. The total reactance is the sum of the radiation reactance and the dielectric capacitive reactance. This reactance becomes zero at two frequencies where the impedance is real. The transducer size can be properly chosen so that the impedance at one of the zero-crossing frequencies is close to 50 Ω, the output impedance of signal generators. At this off-resonant operating frequency, the reflection coefficient of the transducer is minimized without using any matching circuit. Other than the size, the impedance can also be fine tuned by adjusting the thickness of material that bonds the transducer plate to the substrates. The acoustic impedance of the substrate and that of the bonding material can also be used as design elements in the transducer structure to achieve better transducer matching. Lead titanate piezoelectric plates were bonded on Lucite, liquid crystal polymer (LCP), and bismuth (Bi) substrates to produce various transducer structures. Their input impedance was simulated using a transducer model and compared with measured values to illustrate the matching principle.

The moderating influence of demographic characteristics, social support, and religious coping on the effectiveness of a multicomponent psychosocial caregiver intervention in three racial ethnic groups.

This article extends the findings from the Resources for Enhancing Alzheimer's Caregiver Health (REACH II) program, a multisite randomized clinical trial of a multicomponent psychosocial intervention, to improve the well-being of informal caregivers (CGs) of persons with dementia. We used residual change scores and stepwise hierarchical regression analyses to explore separately in 3 racial ethnic groups (Hispanic or Latino, Black or African American, and White or Caucasian) how the effects of the intervention were moderated by CG characteristics (sex, age, education, and relationship), CG resources (social support), and religious coping. The results indicated that CG's age and religious coping moderated the effects of the intervention for Hispanics and Blacks. The older Hispanic and Black CGs who received the intervention reported a decrease in CG burden from baseline to follow-up. Black CGs with less religious coping who received the intervention also reported a decrease in depressive symptoms from baseline to follow-up.

Measurement of temperature profiles on visible light-emitting diodes by use of a nematic liquid crystal and an infrared laser.

We present a new technique for measuring the temperature profiles of visible LED chips by use of a nematic liquid crystal with IR laser illumination. The LEDs studied have a multi-quantum-well InGaN/GaN/sapphire structure. New features in this technique are the use of a high-power IR laser beam as the sensing light and the insertion of a color filter in the optical path to block the high-intensity LED light. For the LEDs measured, the conversion efficiency decreases by 70% when the junction temperature rises from 25 to 107 degrees C. This technique is a valuable tool for studying the performance of LEDs as a function of junction temperature.