Biomedical subjects

A Kloppe

Publications and source records attributed to A Kloppe.

7 recordsLinked to original sources

PubMed2002

New sensor based on fibre optics for measurement of heart movement.

Innovative fibre-optic sensor technology for measuring the movement of the myocardial walls, and from this the heart chamber volumes, was developed. An optical fibre, with a mirror at its end, is inserted into a catheter located in the heart. An opto-electrical control unit positioned outside the heart contains both the light source and the signal receiver. It generates and couples the light into the fibre and transforms and analyses the reflected signal. With such a system, the movement of the cardiac wall can be continuously measured during each cycle, because the fibre moves synchronously with the heart, and this movement bends the fibre, changing the optical attenuation. Experiments where the fibres were wound around metal cylinders of different diameters revealed a maximum sensitivity of 4% mm(-1), diameter. The noise signal corresponded to about 1% of the diameter. First tests in a working pig heart showed a high correspondence of the fibre signal with cardiac parameters. Although these tests are promising, further long-term, extensive experiments in preclinical test devices, and later in clinical tests, must be carried out before the new sensor is used in clinical practice. The fibre-optic technique could be used in monitoring devices, assist devices, pacemaker systems or cardioverter defibrillators.

Animals↗

PubMed2002

[Biventricular defibrillation using transvenous electrodes].

This study investigated the feasibility of transvenous biventricular defibrillation using an electrode in a left ventricular vein. The standard lead configuration with a coil in the right ventricle (RV) and a coil in the superior vena cava (SVC) was compared with an additional unipolar coil in an accessible epicardial vein. Only biphasic shocks were used with different shocking modes between the coils in the RV, LV, SVC and the ICD-generator (CAN). Shocks were applied starting with 30 J, decreasing till the DFT was reached. As a result there is a lower DFT when defibrillation is performed including the left ventricular electrode. The impedance did not show a significant increase after more then 20 consecutive shocks. It is a feasible and workable application that might help to reduce the energy demand and increase the safety of such a system.

Animals↗

PubMed2002

[Rate-responsive pacemaker concept: parametric system identification].

The focus of this paper is the design of a rate-responsive pacemaker which uses the atrio-ventricular conduction time (AVCT) as an exertion related sensor signal. AVCT can be easily obtained from an intracardial electrogram. During atrial pacing AVCT shortens with exercise but increases with the stimulation rate. Hence, an AVCT based pacemaker always establishes a closed-loop system. General design rules for an AVCT pacemaker have been developed from our experimental results and a system-theoretical treatment. Topics addressed were the controller gain, uncertainties concerning the dynamics of the AVCT, the attenuation of disturbances, the closed-loop bandwidth and stability.

Algorithms↗

PubMed2002

[Blood gas regulation in isolated beating pig hearts].

Continuous perfusion with oxygenated blood is required to supply isolated beating pig hearts. To meet physiological conditions the blood gas parameters pH, pO2 and pCO2 should correspond with values usually found in pigs, respectively. Controlling these parameters manually is a very time consuming task and is therefore done best by a control system consisting of gas blender, oxygenator and blood gas sensors. As this control system should be used with an transportable perfusion apparatus, this paper describes an approach where the gassing is realized only with air and oxygen. In this approach pO2 and pH are measured on blood side so that the control system can change oxygen concentration and gas flow adequately on the gas side.

Acid-Base Equilibrium↗

PubMed2002

[Fiberoptic measurement of myocardial contraction--correlation of the signal with hemodynamic values].

In addition to the intracardial ECG, the mechanical myocard contraction should be used as another input signal for cardiac pacemakers and implantable defibrillators. Therefore a fiberoptical measurement system was designed. A sensor-fiber was placed in the coronary venous system. An opto-electronic system converts the optical losses, caused by bending of the fiber, into a proportional voltage. This method allows measuring of the left ventricular myocard contraction strength. By theoretical calculations it was shown, that a good correlation of the sensor-signal and the left ventricular radius can be expected. Additional investigations using an isolated beating pig heart were performed. A high correlation of the sensor-signal and the left ventricular stroke volume was shown.

Animals↗

PubMed2000

Assessment of the chronotropic response at the anaerobic threshold: an objective measure of chronotropic function.

The evaluation of the heart rate response to exercise is important for the diagnosis of chronotropic incompetence and the assessment of a rate responsive algorithm of sensor-controlled pacemakers. The aim of the present study was to examine a classification of the chronotropic response at an individually moderate exercise level. Sixteen pacemaker patients (patient group, age 62.9 +/- 7.6 years) with sick sinus syndrome and 15 age-matched healthy subjects (control group, age 57.6 +/- 9.4 years) underwent a maximum cardiopulmonary exercise test on a treadmill after a protocol with individually selected incremental steps. To analyze the patients' intrinsic heart rate response, the rate responsive mode of the pacemaker was switched off. Chronotropic incompetence was diagnosed in eight patients whose maximal heart rate was < 80% of the age-predicted heart rate. The heart rate at the anaerobic threshold was significantly lower in the chronotropically incompetent subgroup than in the chronotropically competent patients and the healthy subjects (85.9 +/- 6.6 beats/min vs 100.3 +/- 9.9 beats/min and 112.9 +/- 11.7 beats/min, respectively). The chronotropic slope of the heart rate reserve as a function of the metabolic reserve was significantly higher in the control group than in the patient groups with either mild or severe chronotropic incompetence (0.94 +/- 0.17 vs 0.64 +/- 0.08 and 0.43 +/- 0.14, respectively). Furthermore, the chronotropically incompetent response could be divided into a linear type with and without a threshold, an exponential, and a logarithmic type. The anaerobic threshold was an objectively detectable breakpoint at an individually moderate exercise level that could be used for characterization of chronotropic function. At the anaerobic threshold, a physiological heart rate response was about 220--age--50 beats/min. A deviation of more than 10 beats/min below this physiological value characterized chronotropic incompetence.

Algorithms↗

PubMed1998

Vascular hamartoma of the left ventricle.

Primary tumors of the heart are very rare. We report a case of a 28-year old female patient in whom a tumor of the left ventricle was first diagnosed by transthoracic echocardiography. Angiography, nuclear magnetic resonance imaging and fasting positron emission tomography with 18-fluorodesoxyglucose suggested the diagnosis of a well vascularized tumor. The tumor was subtotally excised during heart surgery under total cardiopulmonary bypass and histological examination identified a predominantly vascular hamartoma.

Adult↗