US 5,520,190 A · Cardiac blood flow sensor and method

Abstract

A cardiac blood flow sensor includes a light source and a photodetector within a housing. The light source projects a beam through a fiber optic line having a first end optically connected to the housing and a distal tip positioned within the patient's heart. A ruby positioned at the distal tip is heated by the beam, and fluoresces for a period of time after illumination ceases. The period of time depends on the temperature of the ruby, so that the fluorescent light is transmitted back through the optic line to the photodetector. The signal generated by the photodetector may be analyzed to estimate the blood flow rate, due to the thermal effect of blood flowing past the heated ruby. The flow sensor may be contained in a common housing with a defibrillator that is implanted in a patient. The sensor may remain inactive until a tachycardia or rapid heart rate is detected, upon which the light source is activated. The cardiac condition is analyzed based on the detected heart rate and blood flow and, if needed, an appropriate therapy is delivered.

Claims19

Dependent claims

A method for discrimination between a pathologic tachycardia and a physiologic tachycardia in a patient comprising the steps of:

selecting a predetermined threshold indicative of tachycardia;
detecting the patient's heart rate;
comparing said detected heart rate with said predetermined threshold;
in response to detection of a heart rate above said predetermined threshold, illuminating a temperature sensitive element positioned within the patient's blood stream, then sensing the duration of fluorescent light emitted;
heating the temperature sensitive element;
waiting a predetermined period of time following said heating step;
after said predetermined period following the heating of the temperature sensitive element, illuminating the temperature sensitive element and then sensing the duration of fluorescent light emitted to measure the temperature of the temperature sensitive element to obtain a relative measure of blood flow;
and
determining whether the tachycardia is physiologic or pathologic in origin based on the relative measure of blood flow.

6 more elements

An implantable cardiac therapy apparatus comprising:

a housing having a port for transmitting light between the housing interior and exterior;
a light source within the housing and in optical communication with the port, such that at least a portion of light emitted by the light source is transmitted along a first beam path between the light source and the port;
a photodetector having an electrical output, the photodetector being responsive to the intensity of light impinging thereon, the photodetector being positioned within the housing and in optical communication with the port, such that at least a portion of light entering the port is transmitted along a second beam path between the port and the detector to impinge on the photodetector;
a processor connected to the photodetector's electrical output;
a flexible elongated light conduit having a first end optically connected to the housing port, and a distal tip including a temperature sensitive element, such that light from the light source is transmitted through the conduit to the distal tip, and such that at least a portion of any light generated by the distal tip is transmitted to the photodetector to generate a signal;
means for illuminating the temperature sensitive element before heating the temperature sensitive element, then sensing the duration of fluorescent light emitted;
means for waiting a predetermined time after heating the temperature sensitive element, then illuminating the temperature sensitive element and sensing the duration of fluorescent light emitted;
and
a pulse generator having an input connected to the processor for generating an electric pulse in a lead extending from an output port of the pulse generator.

6 more elements

Dependencies are inferred from the claim text.

Cardiac blood flow sensor and method

Life of this patent

Cardiac blood flow sensor and method

Life of this patent

Abstract

Claims19