Zbigniew Dunajski

Responses to median and tibial nerve stimulation in patients with chronic neuropathic pain.

Somatosensory evoked magnetic fields and electrical potentials were measured in eight patients with unilateral neuropathic pain. After median nerve stimulation on the painful side, the amplitudes of the evoked responses were enhanced 2 to 3 times at a latency of about 100 ms compared to the responses of the contralateral, unaffected side. After posterior tibial nerve stimulation an enhancement was found at latencies around 110 ms and 150 ms. The scalp distribution of the magnetic field at the latencies of “abnormal” responses was dipolar and the responses could be ascribed to a current dipole. Three (of the eight) patients underwent spinal cord stimulation (SCS) for their pain. The enhancement of the evoked responses to stimulation of the painful side decreased after spinal cord stimulation. After a long period of spinal cord stimulation only (e.g., a year) during which the patient reported to be pain free, these “abnormal” responses were no longer observed.

Impedance measurements for pacing treatment in syncopic patients

Intracardiac electrical impedance was proposed as a method of assessing of signal for pacing control since 20 years. In cardiac pacing applications of impedance method one or more intracardiac pacing leads and active pacemaker housing are used as poles for measurement procedure. The stroke volume (SV) signal can be calculated from impedance signal by specialized algorithm in typical pacing system. Our previous study has showed that in group of 42 syncopic patients developing of vasodepresive reaction the SV drop was observed significantly before blood pressure (BP) drop. We have found that the SV drop is excellent indicator of early phase of syncope.

Improving signal-to-noise ratio of fetal magnetocardiograph by third order flux transformer

The application of SQUIDS and superconducting radiometers in clinical biomagnetic instrumentation for fetal magnetocardiography is presented. The paper focuses on the characteristics and performance of the third order flux transformer for fetal magnetocardiography with a good signal to noise ratio. An optimum figure of merit of the third order flux transformer was determined. The optimal signal-to-noise ratio (SNR) was used as the optimization criterion.

The Focuses of Pathology of Electrical Activity of Brain in Assessment of Origin of Syncope

The origin and aetiology of some syncope attacks are still an unsolved issue. The hypothesis of focuses of origin of the syncope is presented in the paper. The results of our syncope study utilizing orthostatic and drug provocation showed: 1. EEG abnormalities prior to the syncope in the left occipital area are observed significantly more frequently than in the right occipital area, 2. Statistically significant differences of the blood flow and hemoglobin concentration in the brain present before and during syncope. The focuses of pathology of electrical activity in the brain common for patients with syncope history and healthy volunteers were found in our study. All published studies up to date were limited by the provoked mechanism of the syncope induction in contrast to the spontaneous syncope. We propose modeling the focuses of syncope origin for clinical verification with high resolution magneto encephalography. High resolution recording of the area of potential focus or focuses of patients with syncope history versus healthy volunteers are proposed as the first stage of model verification. The next step should consist of recording of the area of potential focus or focuses in patients undergoing provocation.

The new criterion for cardiac resynchronization therapy treatment assessed by two channels impedance cardiography

The cardiac resynchronization therapy is an effective treatment for systolic failure patients. Independent electrical stimulation of left and right ventricle corrects mechanical ventricular dyssynchrony. About 30–40% treated patients do not respond to therapy. In order to improve clinical outcome authors propose the two channels impedance cardiography for assessment of ventricular dyssynchrony. The proposed method is intended for validation of patients diagnosis and optimization of pacemaker settings for cardiac resynchronization therapy. The preliminary study has showed that bichannel impedance cardiography is a promising tool for assessment of ventricular dyssynchrony.

The Impedance Cardiography - A Simple and Effective Tool for Optimization of Hemodynamic Parameters in Pacemaker Patients Follow-Up

The echocardiographic, plethyzmographic and impedance methods of atrioventricular delay (AV) optimization were tested in several groups of patients with implanted DDD pacemakers. The measurement was performed for pacing rate of 70 beats per minutes. We extended our latest study to examine the hemodynamic efficiency of the heart during different pacing rate. The criterion of optimization of the AV was the highest value of the stroke volume (SV) measured by plethyzmographic and impedance methods applied to the same patients at the same time. The stroke volume values were assessed for different pacing rates. The results showed no significant discrepancy between different test methods. Therefore we concluded that the impedance method was the most clinically useful method due to its simplicity. Four methods of AV optimization were tested in 10 patients treated by the cardiac resynchronization therapy (CRT). The criterion of optimization of AV by the impedance and plethyzmographic methods was the delay of the highest value of SV. Two echocardiographic techniques: quantitative based on the Ritter formula and qualitative based on the visual evaluation of echocardiogram were also tested. The only significant differences between echocardiographic criteria and maximal SV criterion (measured simultaneously by impedance cardiography and plethyzmography) were found in a patient with the high insufficiency of valves. The impedance method was also found to be optimal in that group of patients.

The impedance methods in cardiology - own clinical results

We applied impedance methods in cardiological diagnosis and therapy for several years. In our clinical practice the impedance cardiography was incorporated in systems for the following diagnostic procedures: passive and provoked head up tilt tests, tailoring of atrioventricular delay in patients dependent on DDD pacing, adjusting of atrioventricular and intraventricular delay in cardiac resynchronization therapy. The impedance methods were also utilized in implanted pacemakers technology as sensors for estimation of exercise load of patient in rate response pacing. Our study of stroke volume behaviour during vasovagal lack of conscious has proved that intracardiac impedance estimation of stroke volume can be applied for early detection of syncope and thus utilized in syncope preventing algorithm in pacemaker technology. The impedance methods are easy to apply and deliver reliable information about current condition of patient. They can be applied on line in diagnostic and therapeutic systems. The records obtained in course of treatment can be easily compared. The impedance methods have showed high clinical efficiency in syncope diagnostic, optimization of atrioventricular and intraventricular delay in cardiac pacing, rate response pacing.

Optimization of Atrioventricular Delay of Pacemaker by Impedance Cardiography and Plethyzmography

In the presented study SV values taken by plethyzmographic device were related to the results given by impedance cardiography device. The 20 patients; 4 females and 16 males (age 74 +/- 7 years) with a history of predominant pacemaker driven rhythm were included in the study group. The stroke volume was assessed for atrioventricular delay settings in a range from 100 to 250 msec. with a step of 10 msec. The basic rhythm for all evaluated patients was 70 bpm. The AV was assumed to be optimal at the maximum value of SV. The obtained results have shown that the plethyzmographic method can be applied for the AV delay optimization. The differences of SV between an optimized and the recommended by the companies settings showed a strong need of tailoring of AV for each patient separately especially in the group of the patients with a predominant pacemaker driven rhythm.

Implementation of Impedance Method in Syncope Treatment

Implementation of Impedance Method in Syncope Treatment Current syncope treatment by cardiac pacing is limited to patients developing cardiodepressive reaction. There is strong need to apply this method to other types of reaction. Presented method shows, that impedance method can be applied for early detection of vasodepressive syncope. Thus the method can be applied for antivasovagal pacing in syncopic patients.

Impedance Cardiography in Cardiac Pacing

The goal of the presented study was to confirm that the impedance algorithms can be utilized for antivasovagal syncope pacing. The clinical examinations showed that the SV signal calculated from impedance signal seems to be the good enough for early detection of syncope with dominant vasodepressive type of reaction.