Abstract: An implantable medical device for in vivo electrochemical measurements of blood properties, such as measurements of, inter alia, oxygen pressure, glucose and pH, avoids the problem with the reference electrodes currently in use which cause inflammatory reactions of tissue, by forming the reference electrode of carbon, preferably activated pyrolytic carbon.

Abstract: An implantable defibrillator has an electrode lead system a sensing unit for sensing the condition of the heart and emitting a condition signal corresponding to that condition, a control unit for determining the heart's condition from the condition signal and, if a state of fibrillation is present, sending a command signal to a shock pulse generator, which, depending on the command signal, delivers at least one defibrillation shock to the heart via the electrode lead system. The shock being formal of one or more low-energy pulses with an energy less than 2 Joules and a very high voltage, i.e. more than 1,000 Volts. Each low-energy pulse thus has a voltage greatly exceeding the voltage in a conventional defibrillation shock and less energy than the energy in a conventional defibrillation shock.

Abstract: A device for detecting hemodynamic conditions in a heart, in particular conditions corresponding to dangerous arrhythmias contains a sensing unit for a physiological variable, such as blood pressure, the unit emitting a signal on the basis of the variable having an average value, a signal conditioning unit connected to the sensing unit, a calculation unit connected to the signal conditioning unit and a comparator after the calculation unit. The calculation unit is devised to calculate a variability measure relative to the signal's average value, the variability measure being correlated to average blood pressure, and the variability measure is compared in the comparator to an adjustable threshold value corresponding to a specific hemodynamic condition, whereupon the comparator emits an indication signal when the variability measure falls below the threshold value.

Abstract: For detecting tachyarrhythmia of the heart, the partial pressure of gases physically dissolved in the blood is measured, preferably the partial oxygen pressure pO.sub.2, and a fast variation and/or a variation of the measured partial pressure pO.sub.2 that exceeds a prescribed degree is utilized as a criterion for the detection of a tachyarrhythmia. An apparatus for treating tachyarrhythmia of the heart operating according to the above method includes a sensor for identifying the partial pressure of gases dissolved in the blood, an evaluation unit supplied with the sensor output for recognizing rapid changes of the partial pressure or changes of the partial pressure that exceed a prescribed degree, the output of the evaluation unit being connected to circuitry for triggering the tachyarrhythmia treatment.

Abstract: A rate-responsive heart stimulator with a variable stimulation interval contains a measurement device which generates a measurement signal corresponding to the volume of blood in a heart during the blood-filling phase (diastole) and a comparator which compares the measurement signal with a defined threshold value corresponding to a defined degree of blood filling. The comparator generates a control signal when the measurement signal reaches the threshold value, the control signal representing the time elapsing since the last stimulation pulse, and controlling the heart stimulator's stimulation interval.

Abstract: In a method and apparatus for detecting ventricular fibrillation, a measured impedance signal, dependent on the blood volume in the heart, is evaluated, and ventricular fibrillation is assumed to be present if the level of the measured impedance signal falls below a predetermined threshold. This is based on the perception that as the heart fills with blood, given the presence of ventricular fibrillation, the level of the measured impedance signal will decrease. The apparatus also includes circuitry for treating the detected ventricular fibrillation.