A Rare Cause of 2:1 AV Block: Long QT Syndrome PATEL, CHINMAY; NARAYANASWAMY, SRINIVASA; MEDINA-RAVELL, VICTOR A. ...
Journal of cardiovascular electrophysiology,
09/2008, Letnik:
19, Številka:
9
Journal Article
An increasing number of basic and clinical studies have suggested that the interval from the peak to the end of the electrocardiographic T wave (T
p-e) may correspond to the transmural dispersion of ...repolarization and that amplification of the T
p-e interval is associated with malignant ventricular arrhythmias. In this review, we outline the utility of the T
p-e interval and the T
p-e/QT ratio as an electrocardiographic index of arrhythmogenesis for both congenital and acquired ion channel disease leading to ventricular arrhythmias. In healthy individuals, the T
p-e/QT ratio has a mean value of approximately 0.21 in the precordial leads and it remains relatively constant between the heart rates from 60 to 100 beats per minute. Interestingly, the T
p-e/QT ratio is significantly greater in the patients at risk for arrhythmic event such as those with long QT syndrome, Brugada syndrome, short QT syndrome, and also in patients with organic heart disease such as acute myocardial infarction. Functional reentry is the underlying mechanism for arrhythmogenesis associated with an increased T
p-e/QT ratio.
T(p-e)/QT ratio as an index of arrhythmogenesis Gupta, Prasad; Patel, Chinmay; Patel, Harsh ...
Journal of electrocardiology,
2008 Nov-Dec, 20081101, Letnik:
41, Številka:
6
Journal Article
Recenzirano
An increasing number of basic and clinical studies have suggested that the interval from the peak to the end of the electrocardiographic T wave (T(p-e)) may correspond to the transmural dispersion of ...repolarization and that amplification of the T(p-e) interval is associated with malignant ventricular arrhythmias. In this review, we outline the utility of the T(p-e) interval and the T(p-e)/QT ratio as an electrocardiographic index of arrhythmogenesis for both congenital and acquired ion channel disease leading to ventricular arrhythmias. In healthy individuals, the T(p-e)/QT ratio has a mean value of approximately 0.21 in the precordial leads and it remains relatively constant between the heart rates from 60 to 100 beats per minute. Interestingly, the T(p-e)/QT ratio is significantly greater in the patients at risk for arrhythmic event such as those with long QT syndrome, Brugada syndrome, short QT syndrome, and also in patients with organic heart disease such as acute myocardial infarction. Functional reentry is the underlying mechanism for arrhythmogenesis associated with an increased T(p-e)/QT ratio.
Small 'bird-sized' Unmanned Aerial Vehicles (UAVs) have now become practical due to technological advances in embedded electronics, miniature sensors and actuators, and propulsion systems. Birds are ...known to take advantage of wind currents to conserve energy and fly long distances without flapping their wings. This dissertation explores the possibility of improving the performance of small UAVs by extracting the energy available in atmospheric turbulence. An aircraft can gain energy from vertical gusts by increasing its lift in regions of updraft and reducing its lift in downdrafts - a concept that has been known for decades. Starting with a simple model of a glider flying through a sinusoidal gust, a parametric optimization approach is used to compute the minimum gust amplitude and optimal control input required for the glider to sustain flight without losing energy. For small UAVs using optimal control inputs, sinusoidal gusts with amplitude of 10–15% of the cruise speed are sufficient to keep the aircraft aloft. The method is then modified and extended to include random gusts that are representative of natural turbulence. A procedure to design optimal control laws for energy extraction from realistic gust profiles is developed using a Genetic Algorithm (GA). A feedback control law is designed to perform well over a variety of random gusts, and not be tailored for one particular gust. A small UAV flying in vertical turbulence is shown to obtain average energy savings of 35–40% with the use of a simple control law. The design procedure is also extended to determine optimal control laws for sinusoidal as well as turbulent lateral gusts. The theoretical work is complemented by experimental validation using a small autonomous UAV. The development of a lightweight autopilot and UAV platform is presented. Flight test results show that active control of the lift of an autonomous glider resulted in approximately 46% average energy savings compared to glides with fixed control surfaces. Statistical analysis of test samples shows that 19% of the active control test runs resulted in no energy loss, thus demonstrating the potential of the 'gust soaring' concept to dramatically improve the performance of small UAVs.
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