Endocardial catheter ablation of ventricular tachycardia in patients with ventricular assist devices

BACKGROUND: The outcomes of patients with ventricular assist devices (VADs) who undergo catheter ablation for ventricular tachycardia (VT) have not been reported. OBJECTIVE: The purpose of this study was to assess the feasibility, safety, and efficacy of endocardial VT ablation in patients with VADs. METHODS: We retrospectively reviewed three cases at our institution where endocardial catheter ablation was performed in patients with VADs and incessant VT. RESULTS: Three patients with underlying cardiomyopathies and VADs underwent VT ablation for incessant VT refractory to multiple antiarrhythmic medications. In each case, VT was either eliminated or significantly ameliorated by catheter ablation. No procedure-related complications occurred. The hemodynamic stability afforded by the VAD played an important role in facilitating ablation in two of the cases. CONCLUSION: Catheter ablation for VT in VAD patients appears to be feasible, safe, and effective based on our initial experience. Several technical issues, such as decreases in ventricular volumes that can limit maneuverability of the ablation catheter and potential entrapment of the mapping catheter in the inflow cannula, need to be considered at the time of ablation.     

Fabrication of Diamond Based Sensors for Use in Extreme Environments

Electrical and magnetic sensors can be lithographically fabricated on top of diamond substrates and encapsulated in a protective layer of chemical vapor deposited single crystalline diamond. This process when carried out on single crystal diamond anvils employed in high pressure research is termed as designer diamond anvil fabrication. These designer diamond anvils allow researchers to study electrical and magnetic properties of materials under extreme conditions without any possibility of damaging the sensing elements. We describe a novel method for the fabrication of designer diamond anvils with the use of maskless lithography and chemical vapor deposition in this paper. This method can be utilized to produce diamond based sensors which can function in extreme environments of high pressures, high and low temperatures, corrosive and high radiation conditions. We demonstrate applicability of these diamonds under extreme environments by performing electrical resistance measurements during superconducting transition in rare earth doped iron-based compounds under high pressures to 12 GPa and low temperatures to 10 K.     

Fragmented QRS on a 12-lead ECG: a predictor of mortality and cardiac events in patients with coronary artery disease.

BACKGROUND: Fragmented QRS (fQRS) on a 12-lead electrocardiogram (ECG) is associated with myocardial scar in patients with coronary artery disease (CAD). OBJECTIVE: We postulated that fQRS is a predictor of cardiac events and mortality in patients who have known CAD or who are being evaluated for CAD. METHODS: The cardiac events (myocardial infarction, need for revascularization, or cardiac death) and all-cause mortality were retrospectively reviewed in 998 patients (mean age 65.5 +/- 11.9 years, male 967) who underwent nuclear stress test. The fQRS on a 12-lead ECG included various RSR' patterns (> or =1 R' prime or notching of S wave or R wave) without typical bundle branch block in 2 contiguous leads corresponding to a major coronary artery territory. RESULTS: All-cause mortality (93 [34.1%] vs 188 [25.9%]) and cardiac event rate (135 [49.5%] vs 200 [27.6%]) were higher in the fQRS group compared with the non-fQRS group during a mean follow-up of 57 +/- 23 months. A Kaplan-Meier survival analysis revealed significantly lower event-free survival for cardiac events (P <.001) and all-cause mortality (P = .02). Multivariate Cox regression analysis revealed that significant fQRS was an independent significant predictor for cardiac events but not for all-cause mortality. The Kaplan-Meier survival analysis showed no significant difference between fQRS and Q waves groups for cardiac events (P = .48) and all-cause mortality (P = .08). CONCLUSION: The fQRS is an independent predictor of cardiac events in patients with CAD. It is associated with significantly lower event-free survival for a cardiac event on long-term follow-up.     

The design effect and cluster samples: optimising tuberculosis prevalence surveys

Cross-sectional surveys of disease prevalence, including for tuberculosis (TB), often use a two (or more) stage sampling procedure. By choosing clusters of people randomly from all possible clusters, the logistic costs of doing the survey can be reduced. However, this increases the statistical uncertainty in the estimate of prevalence, and we need to balance the reduction in cost against the increase in uncertainty. Here we describe cluster sampling and consider ways to determine the optimal survey design as well as the extent to which deviations from the optimal design matter. We illustrate the results using data from a recent survey in Cambodia in which TB was diagnosed using sputum smears, cultures and X-rays.     

Health-seeking behaviour of new smear-positive TB patients under a DOTS programme in Tamil Nadu, India, 2003.

BACKGROUND: Although case detection is above 70% in Tamil Nadu after DOTS implementation, an assessment of the timeliness of patient diagnosis and treatment is still needed. OBJECTIVE: To study the health-seeking behaviour of new smear-positive pulmonary tuberculosis (PTB) patients treated at government facilities. METHODS: New smear-positive patients diagnosed and treated between January and March 2003 in government facilities of randomly selected blocks in Tamil Nadu were interviewed using a semi-structured interview schedule. RESULTS: Of 601 patients interviewed, 65% contacted a provider within 28 days. The first contact was governmental for 47% and non-governmental for 53%. Median total, patient and provider delays were respectively 62, 28 and 28 days; provider delay was 9 days with government and 50 with private provider. In multivariate analysis, patient delay was significantly associated with smoking (P < 0.001) and mode of travel (P < 0.01), and provider delay with first consultation with a private provider (P < 0.001) and distance > 5 km from the health facility (P < 0.01). Twenty-five per cent of patients took more than two actions before diagnosis. CONCLUSION: Community awareness of TB needs to be increased. Greater private sector involvement in the Revised National Tuberculosis Control Programme is essential to reduce provider delay. Referral and sputum transportation to the diagnostic facility should be given priority.     

Rapid Growth of Nanostructured Diamond Film on Silicon and Ti–6Al–4V Alloy Substrates

Nanostructured diamond (NSD) films were grown on silicon and Ti–6Al–4V alloy substrates by microwave plasma chemical vapor deposition (MPCVD). NSD Growth rates of 5 μm/h on silicon, and 4 μm/h on Ti–6Al–4V were achieved. In a chemistry of H₂/CH₄/N₂, varying ratios of CH₄/H₂ and N₂/CH₄ were employed in this research and their effect on the resulting diamond films were studied by X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. As a result of modifying the stock cooling stage of CVD system, we were able to utilize plasma with high power densities in our NSD growth experiments, enabling us to achieve high growth rates. Substrate temperature and N₂/CH₄ ratio have been found to be key factors in determining the diamond film quality. NSD films grown as part of this study were shown to contain 85% to 90% sp³ bonded carbon.