Abstract: A method for analyzing electrocardiograph signals to determine risk of malignant arrhythmias, that involves: sensing fluctuations in voltage resulting from electrical activity of a heart over a time period of about 256 seconds as signals having an analog value; converting such signals having an analog value to digital values corresponding substantially to the analog value of the signals; recording the digital values in a record; analyzing the digital values of the record by: identifying a time of each R wave of a heartbeat; defining a template QT interval for a heartbeat by selecting a beginning of a QRS complex and an end of a T wave for the heartbeat; determining an alteration value selected from the group consisting of an elongation of a heartbeat in time and a compression of a heartbeat in time as an error function for the heartbeat; performing a binary search to determine a minimal value for the error function; and assessing changes in QT interval for each heartbeat using the entire T wave.

Abstract: An assembly of preformed curved enamel-coated ablative tipped endocardial electrodes are housed inside an outer sheath in a preformed geometric arrangement for insertion into heart chambers and application onto the endocardial surface of the heart. The position of the electrodes relative to each other is predetermined by their arrangement on a Teflon bushing which serves as a platform anchored on the end of an inner sheath. The inner sheath is moveable relative to the outer sheath thus allowing graded exposure of the electrodes controlling movement toward the apical and lateral walls of the chamber. Ablative energy is delivered through the 8 mm J-tipped electrode to destroy the arrhythmia focus or reentrant circuit.

Abstract: A method and apparatus for estimating transfer functions among multiple physiologic or biologic signals in the presence of feedback. The invention comprises the injection of broad band purturbation into one or more of the subsystems under study, and measuring signals from the subsystems. These signals are transformed to generate a new set of n signals. Casual transfer functions between the signals and additive noise sources are used to represent the relationships between the n signals. Parametric system identification techniques are then used to characterize quantitatively at least two casual transfer functions and noise sources. This method and apparatus provides a powerful tool with which to characterize the interactions of subsystems in the presence of feedback.

Abstract: A rapid, noninvasive technique for quantifying the dynamic response of the autonomic nervous system (ANS) to perturbations it senses over a broad range of physiologically relevant frequencies. The technique involves two steps. First, a physiologic parameter sensed by the ANS is subjected to a broad-band perturbation as an input signal while a physiologic parameter modulated by the ANS is monitored as an output signal. Then, the transfer relation between input signal and output signal is determined. The computed transfer relation is then readily interpretable in terms of responsiveness of the various limbs of the ANS.