We are developing a cardiac pacemaker with a small, cylindrical shape that permits percutaneous implantation into a fetus to treat complete heart block and consequent hydrops fetalis, which can otherwise be fatal. The device uses off-the-shelf components including a rechargeable lithium cell and a highly efficient relaxation oscillator encapsulated in epoxy and glass. A corkscrew electrode made from activated iridium can be screwed into the myocardium, followed by release of the pacemaker and a short, flexible lead entirely within the chest of the fetus to avoid dislodgement from fetal movement. Acute tests in adult rabbits demonstrated the range of electrical parameters required for successful pacing and the feasibility of successfully implanting the device percutaneously under ultrasonic imaging guidance. The lithium cell can be recharged inductively as needed, as indicated by a small decline in the pulsing rate.
A miniaturized, self-contained pacemaker that could be implanted with a minimally invasive technique would dramatically improve the survival rate for fetuses that develop hydrops fetalis as a result of congenital heart block. We are currently validating a device that we developed to address this bradyarrhythmia. Preclinical studies in a fetal sheep model are underway to demonstrate that the device can be implanted via a minimally invasive approach, can mechanically withstand the harsh bodily environment, can induce effective contractions of the heart muscle with an adequate safety factor, and can successfully operate for the required device lifetime of three months using the previously-developed closed loop transcutaneous recharging system.
We are developing a cardiac pacemaker that is designed to be implanted percutaneously into a fetus to treat complete heart block and consequent hydrops fetalis, which is otherwise fatal. One of the most significant considerations for this device is the technical challenges presented by the battery and charging system. The size of the device is limited to about 3 mm in diameter; batteries on this scale have very small charge capacities. The smaller capacity means that the device needs to be designed so that it uses as little current as possible and so that its battery can be recharged wirelessly. We determined the pacing thresholds for a simple relaxation oscillator that can be assembled from discrete, surface mount components and analyzed the power consumption of the device given different electrode configurations and stimulus parameters. An inductive recharging system will be required for some patients; it is feasible within the package constraints and under development.
Red blood cell distribution width (RDW) is associated with increased mortality in several diseases. However, the relationship between RDW fluctuations and the prognosis of critically ill patients with type 2 diabetes mellitus (T2DM) has not been reported. This study investigated the association between baseline RDW levels and dynamic changes and short-term mortality in critically ill patients with T2DM. All critically ill patients meeting the diagnostic criteria for T2DM in the Medical Information Mart for Intensive Care IV database were retrospectively analyzed. Logistic and Cox regression, Kaplan–Meier survival, and subgroup analyses were used to determine the association between baseline RDW and short-term mortality in critically ill patients with T2DM. Generalized additive mixed models were then used to compare trends in RDW over time between survivors and non-survivors. This study enrolled 6,299 patients with a 28-day mortality rate of 18.4%. Kaplan–Meier analysis showed higher 28-day and 60-day mortality (P<0.001) in the high baseline RDW group. High baseline RDW was revealed by multivariate logistic and Cox regression models as an independent risk factor for in-hospital, 28-day, and 60-day mortality in critically ill patients with T2DM. An association between elevated baseline RDW and 28-day mortality was observed in all subgroup analyses. The generalized summation mixed-effects model results showed a significant difference in RDW between the surviving and non-surviving groups within 48 h of admission to the intensive care unit (ICU). Moreover, this difference increased with time (β=0.034, P=0.003). Elevated baseline RDW at ICU admission was associated with high short-term mortality in critically ill patients with T2DM, an association that remained significant within 48 h of patient admission to the ICU. Moreover, dynamic monitoring of RDW may help predict short-term mortality in critically ill patients with T2DM. However, this finding requires further validation in prospective studies.
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