Search PubMed⌕ Search

Biomedical subjects

J Neuzner

Publications and source records attributed to J Neuzner.

At least 19 recordsLinked to original sources
PubMed2001

Inappropriate arrhythmia detection in implantable defibrillator therapy due to oversensing of diaphragmatic myopotentials.

Nonadequate arrhythmia detection and delivery of electrical therapy is still a main problem in current implantable cardioverter defibrillator therapy. Besides supraventricular arrhythmias extra-cardiac biosignals also can cause inadequate shock delivery. The present study focuses on nonadequate arrhythmia detection due to oversensing of diaphragmatic myopotentials. Their clinical characteristics, incidence and management are presented. Three-hundred-eighty-four recipients of a transvenous cardioverter-defibrillator who were implanted and followed-up at our institution between October 1991 and June 1999 were enrolled. During a mean follow-up of 32+/-25 months a total number of 139 nonadequate episodes of arrhythmia detection due to oversensing of diaphragmatic myopotentials were observed in 33 patients (8.6%). In 11 patients a total of 32 high energy shock deliveries occurred. Oversensing of diaphragmatic myopotentials was primarily observed in patients implanted with defibrillator leads providing "integrated bipolar" sensing. The vast majority of nonadequate arrhythmia detection were observed during intrinsic bradycardia heart rate and/or antibradycardia pacing. Electrical lead failure was ruled out in every patient. In 90% of the patients with a cardioverter-defibrillator providing programmable maximal sensitivity (n=16), the reduction of maximum sensitivity was effective in preventing further episodes of nonadequate arrhythmia detection. In 48% of the patients with devices without programmable maximal sensitivity (n=17), surgery revision was necessary to solve the problem.

Adult↗
PubMed2001

Possible role of epicardial left ventricular programmed stimulation in Brugada syndrome.

A patient with recurrent syncope due to polymorphic ventricular tachycardia was diagnosed with Brugada syndrome. Programmed right ventricular stimulation could not induce arrhythmia. Epicardial stimulation from a left ventricular site through the coronary sinus led to polymorphic VT. The stimulation protocol for risk stratification in Brugada syndrome is discussed.

Adult↗
PubMed2001

Myocardial injury during radiofrequency catheter ablation: comparison of focal and linear lesions.

The aim of study was to investigate the extent of myocardial injury incurred by creation of continuous RF current induced linear ablation lesions (LL; ablation of atrial fibrillation, right atrial procedure) in comparison to focal RF lesions (FL; AV node reentry tachycardia, WPW tachycardia). In 23 patients with LL (age 51.3 +/- 11.2 years, 18 men, 5 women) and in 16 patients with FL (age 53.9 +/- 5.1 years, 8 men and 8 women), levels of creatine kinase (CK), myoglobin (MG), CKMB mass (CKMB M), CKMB activity (CKMB A), and cardiac troponin T (cTnT) were determined before and 2, 4, 8, 24, and 48 hours after ablation. CKMB A was normal in 87% in LL and 100% in FL (< 6% of CK) with median maximum CK values of 214 (45-1583) U/L in LL and 36 (29-212) U/L in FL. Peak values of all parameters were significantly higher in LL than in FL. The sensitivity of cTnT was 50% in FL and 100% in LL. In FL MG, total CK, and CKMB M were abnormal in only 12.5% of cases while in LL MG and CKMB M were pathological in 100% and total CK was abnormal in 91.3% of patients. The amount of energy and number of RF applications correlated with cTnT, MG, and CKMB M (P = 0.01). In conclusion, (1) long linear RF current lesions for ablation of atrial fibrillation are associated with significantly greater myocardial injury than focal ablations. (2) In focal lesions only cTnT provided a sensitivity of 50% in the detection of myocardial injury while in linear lesions cTnT, CKMBM, and CKMB M seemed suitable for detection of RF current induced myocardial damage with 100% sensitivity. All biochemical parameters do not differentiate patients with coronary ischemia up to 48 hours after an ablation. (3) Further investigations are necessary to determine if RF current linear lesions lead to impaired atrial contractility in cases of extensive tissue damage.

Adult↗
PubMed2001

Reduction of pacing output coupling capacitance for sensing the evoked response.

Sensing of the intracardiac evoked response (ER) after a pacing stimulus has been used in implantable pacemakers for automatic verification of capture. Reliable detection of ER is hampered by large residual afterpotentials associated with pacing stimuli. This led to the development of various technological solutions, like the use of triphasic pacing pulses and low polarizing electrode systems. This study investigated the effect of reducing the coupling capacitance (CC) in the pacemaker output circuitry on the magnitude of afterpotential, and the ability to automate detection of ventricular evoked response. A CC of 2.2 microF and four different blanking and recharge time settings were clinically tested to evaluate its impact on sensing of the ventricular ER and pacing threshold. Using an automatic step-down threshold algorithm, 54 consecutive patients, aged 70 +/- 10 years with acutely (n = 27) or chronically (n = 27) implanted ventricular pacing leads were enrolled for measurement testing. Routine measurements, using a standard pacing system analyzer (PSA), were (mean +/- SD) impedance 569 +/- 155 omega, R wave amplitude baseline to peak 9.8 +/- 3.7 mV and threshold 0.9 +/- 0.7 V at 0.4-ms pulse width. This new capture verification scheme, based on a CC of 2.2 microF and recharge/blanking timing setting of 10/12 ms, was successful in 52 patients which is equivalent to a success rate of 96%. In a subgroup of 26 patients implanted with bipolar ventricular leads (10 chronic, 16 acute), data were collected in unipolar (UP) and bipolar (BP) pace/sense configurations. Also, ER signals were recorded with two different band-pass filters: a wider band (WB) of 6-250 Hz and a conventional narrow band (NB) of 20-100 Hz. WB sensing from UP lead configuration yielded statistically significant larger signal to artifact ratios (SAR) than the other settings (P < 0.01). A dedicated unipolar ER sensing configuration using a small output capacitor and a wider band-pass filter enables adequate automatic capture verification, without any restrictions on pacing lead models or pacing/sensing configurations.

Aged↗
PubMed2001

Dual-coil vs single-coil active pectoral implantable defibrillator lead systems: defibrillation energy requirements and probability of defibrillation success at multiples of the defibrillation energy requirements.

AIMS: The aim of the study was to compare the defibrillation energy requirements and the probability of successful defibrillation at multiples of the minimum defibrillation energy requirements in active pectoral implantable defibrillators with single- and dual-coil lead systems. METHODS AND RESULTS: Eighty-three consecutive patients undergoing implantation of an active pectoral cardioverter-defibrillator were randomized to receive a dual- or single-coil lead system. Defibrillators of two manufacturers with a fixed tilt biphasic defibrillation waveform were used. Defibrillation energy requirements were determined using a step-down defibrillation testing protocol. According to the randomization protocol, the patients were assigned to three additional consecutive defibrillation attempts during device implantation and during pre-discharge testing of either 1.0, 1.5 or 2.0 times the determined defibrillation energy requirement. Patients presenting defibrillation energy requirements > 15 J were excluded from analysis. Eighty of 83 patients (96%) completed the study protocol. Three patients were excluded due to elevated defibrillation energy requirements. The defibrillation energy requirements in the dual- and single-coil patient groups were 8.0 +/- 3.6 J and 8.4 +/- 3.7 J (ns), respectively. A comparable percentage of study patients showed defibrillation energy requirements <10 J (dual-coil: 88% vs single-coil: 83%). Defibrillation impedance was significantly different (dual-coil: 50 +/- 5.8 Ohm; single-coil: 39.8 +/- 4.2 Ohm). Regarding the probabilities of successful defibrillation, there were no significant differences between the two patient groups. The probabilities of defibrillation at the three multiples of the defibrillation energy requirement using a dual- and single-coil lead system were 82, 89.7 and 93.6 and 77.8, 94.1 and 95.8%, respectively (P=0.88, P=0.42, P=0.62, respectively). CONCLUSIONS: Dual- and single-coil active pectoral defibrillator systems show no difference in defibrillation energy requirements and no difference in the probability of successful defibrillation at multiples of the minimum defibrillation energy requirement. The use of more simplified defibrillator lead systems may contribute to a future lead design focusing on improvement in lead durability.

Aged↗
PubMed2001

Electrochemical potentials during radiofrequency energy delivery: a new method to control catheter ablation of arrhythmias.

AIMS: Thermal injury of subendocardial tissue leads to a release of electrolytes and free radicals from the intracellular site creating a change in electrochemical potential (eP) between the distal and the proximal catheter tip electrodes. The aim of the study was to verify the detection of ablation-induced release of electrolytes and free radicals and to assess the suitability of control-line energy delivery at ablation by measuring eP. METHODS AND RESULTS: In vitro tests under constant flow conditions were performed in a 101 bath of physiological saline solution or bovine blood. Endomyocardial preparations of fresh bovine hearts were used. Closed-loop temperature-controlled, irrigated and closed-loop eP-controlled ablations were performed. In vivo animal investigations were performed in six anaesthetized and ventilated pigs. The existence of the eP was established in the tank model and was confirmed in animal investigations. High correlations were found between eP and catheter tip temperature (r=0.87) and between maximum eP and induced lesion size (r=0.85). Also a high correlation (r=0.85, P<0.001) was found between eP and lesion volume. CONCLUSIONS: Control of energy delivery during RF ablation by the measurement of eP is feasible. In comparison with temperature controlled RF ablation, ablation guided by eP-measurement revealed a superior correlation with induced lesion size. Especially during cooled radiofrequency catheter ablation eP is the only parameter for control of energy delivery.

Action Potentials↗
PubMed2001

Stimulation of the left ventricle through the coronary sinus with a newly developed 'over the wire' lead system--early experiences with lead handling and positioning.

AIMS: This report describes the initial clinical results with a newly designed guiding catheter and an 'over the wire' pacing lead based on angiolasty technology to stimulate the left ventricle using the transvenous route via the coronary sinus (OTW-CV lead). METHODS AND RESULTS: In 75% of the 15 patients (6 males, 9 females, mean age of 53 +/- 9 years) with congestive heart failure, access to coronary sinus required less than 2 min; in one patient. the attempt failed. Mean R wave amplitudes plus or minus the standard deviation, measured at apical, mid-ventricular and basal positions the anterior (11.4 +/- 9.2, 10.8 +/- 6.2, 9.3 +/- 6.3 mV) and lateral or posterior veins (10.1 +/- 10.7, 8.6 +/- 6.4, 7.7 +/- 4.3 mV) showed a trend favouring the apex without statistical significance. Pacing impedance, measured at the same sites and vein tributaries, ranged from 670 +/- 191 to 915 +/- 145 ohms. Pacing thresholds measured at apical and mid ventricular sites were significantly lower than at the base in the anterior vein 2.5 +/- 2.8 and 2.8 +/- 1.8 vs 5.6 +/- 2.7 V at 0.5 ms, P<0.001). Thresholds in the lateral/posterior veins showed a similar trend but did not reach statistical significance (3.0 +/- 1.7, 3.6 +/- 1.4 +/- 1.8 V at 0.5 ms). In patients, in whom thresholds were determined in more than one vein, the 'best' mean threshold was 1.6 +/- 0.7 V. CONCLUSION: The new 'over the wire' lead and guiding catheter system allows uncomplicated access to the coronary sinus and the depth of the coronary vein tributaries. Left ventricular sensing and pacing thresholds are acceptable for chronic use in implanted cardiac rhythm management systems.

Adult↗
PubMed2001

Peripheral arterial embolism originating from a thrombus in the ascending aorta.

A 45-year-old man experienced arterial thromboembolism to the right leg requiring surgical restoration of blood flow. Transesophageal echocardiography (TEE) was performed to determine the source of embolism and identified a localized atherosclerotic lesion in the distal ascending aorta with an adherent, highly mobile thrombus. The patient underwent surgery with removal of the atherosclerotic plaque and attached thrombus, and resection of the adjacent aortic wall. This case illustrates an unusual location for a complex atherosclerotic lesion in the ascending aorta, and points out the opportunity for remedial surgery once a symptomatic embolus has occurred.

Aorta↗
PubMed2000

Pacemaker automaticity.

The automated measurement of the main electrical parameters of pacemakers, such as battery voltage, current drain, pacing impedance, sensing levels, and pacing thresholds enables a continuous monitoring of the adequate functioning of the implanted device. New technologies in device interrogation, data transfer, and patient alert functions will enhance therapy safety significantly by the immediate detection of all, including transient, device malfunctions. The introduction of this technology will result in major changes in follow-up of patients with pacemakers. Technically we are very close to the goal of a fully automated pacemaker, although clinical acceptance lags behind. Clinical studies are necessary to demonstrate the beneficial effects of automated device functions, with regard to the main rationales for pacemaker automatization: increased patient safety, improved quality of life, and an improvement in the cost-benefit ratio in pacemaker therapy.

Arrhythmias, Cardiac↗
PubMed2000

[Recurrent syncope of unknown origin. Diagnosis with implantable "loop" recorders].

BACKGROUND: In about a third of cases of recurrent syncope a diagnosis cannot be established despite extensive cardiovascular and neurologic testing. In patients without underlying heart disease the sensitivity of conventional diagnostic testing is low. CASE REPORT: A 33-year-old male patient underwent implantation of a loop recorder (Reveal) after negative neurological and cardiovascular testing. One month after implantation sinus node arrest could be documented during a presyncope. The patient underwent pacemaker implantation and remains asymptomatic since then. CONCLUSION: In patients with syncope and a negative conventional diagnostic workup the implantable loop recorder is a helpful and cost-effective diagnostic tool.

Adult↗
PubMed2000

[Recurrent syncope in a 34-year-old woman triathlete].

HISTORY: Some weeks previously a 34-year old athlete, specializing in the triathlon, had 6 syncopes in one day. They had caused abrasions and contusions resulting from the falls. At another hospital paroxysmal atrial fibrillation had been diagnosed and treatment with disopyramide (2 x 200 mg) initiated, but she had about 15 further syncopes within 2 weeks. She was admitted for establishing their cause. INVESTIGATIONS: Initial ECGs and neurological examination failed to provide a diagnosis and she was discharged with an "event recorder". DIAGNOSIS, TREATMENT AND COURSE: Three weeks after discharge she had another syncope. The event recorder was activated by the patient's partner and revealed polymorphous ventricular tachycardia. She underwent extensive invasive cardiological tests, including a right ventricular biopsy, but no abnormality was demonstrated. However, a provocation test with ajmaline produced ST segment elevations in V1 and V2 typical of the syndrome previously described by the Brugadas (right bundle branch block, precordial ST elevations in V1-V3 and sudden cardiac death). A cardioverter-defibrillator was implanted. During the subsequent observation period of 2 month the ICD delivered one countershock, triggered by the onset of polymorphous ventricular tachycardia with syncope. CONCLUSION: In patients with serious ventricular arrhythmias but no diagnostic findings, including a normal resting ECG, a drug provocation test should be performed to exclude a Brugada syndrome.

Adult↗
PubMed2000

[Socioeconomic aspects of the treatment of arrhythmias].

In the current clinical cardiac electrophysiology well-defined and effective concepts regarding the diagnostic and treatment of cardiac arrhythmias have been introduced. A further improvement in the cost-benefit and the cost-effectiveness relationships in several fields of cardiac electrophysiology depends on the future technical progress and on the results of ongoing and future scientific studies. On the other side very cost-saving electrophysiological treatments had been developed; the broader clinical use of these treatments is a possibility to optimize the costs for patients' care with cardiac arrhythmias.

Adult↗
PubMed2000

[Non-drug treatment methods in ventricular rate control in atrial fibrillation: high-frequency catheter ablation and catheter modification of the AV node].

AV nodal ablation with pacemaker implantation nor AV nodal modification is the therapy of the choice in patients with permanent or paroxysmal atrial tachyarrhythmias. Both methods of treatment are limited to patients with drug refractory atrial tachyarrhythmias. Therapy indication requires the complete knowledge of the current clinical status and medical history of the patient regarding the time course of the disease and the results of previous treatments. Both methods are effective and palliative treatments which may not modify the underlying arrhythmias. Neither treatment showed an improvement in patients prognosis; therefore a restrictive indication is mandatory.

Aged↗
PubMed2000

[Double ventricular excitation in dual atrioventricular node conduction physiology: catheter ablation of the slow conduction pathway of the dual atrioventricular node].

A variety of electrocardiographic manifestations of dual AV nodal physiology have been reported. The specific subtype dual ventricular response is considered as a very rare phenomenon. We present the case of a 53 year old lady who suffered from paroxysmal regular tachycardias for more than seven years. In the last 6 months the symptomatology of the cardiac arrhythmia changed to more persistent und irregular rhythm disturbances. Treatment with class Ia antiarrhythmic drugs and beta-blocking agents failed. The latter even seemed to worsen her very disturbing palpitations. After examination of the ECG recordings, the diagnosis of dual AV nodal physiology with double ventricular response was made--the lady was referred to our institution for electrophysiological testing and radiofrequency catheter ablation of the slow pathway. An invasive electrophysiological study reconfirmed the diagnosis of a dual AV nodal conduction pattern with irregular double ventricular response. The radiofrequency catheter ablation of the the slow pathway achieved a complete cessation of the double ventricular response. This satisfactory outcome was confirmed by analysis of a postinterventional 24 hour holter recording and an exercise stress test. During a follow-up period of three months, the patient remained free of symptoms and there was no recurrence of dual AV nodal conduction physiology in the surface ECG.

Atrioventricular Node↗
PubMed2000

Electrophysiological heterogeneity of atrial fibrillation and local effect of propafenone in the human right atrium: analysis based on symbolic dynamics.

UNLABELLED: A recently developed algorithm that is based on symbolic dynamics and computation of the normalized algorithmic complexity (C(alpha)) was applied to basket-catheter mapping of the atrial fibrillation (AF). The aim of our study was to analyze the spatial distribution of the C(alpha) during AF and effects of propafenone on this distribution. During right atrial mapping in 25 patients with AF 31 intra-atrial and 1 surface bipolar channels were acquired. The anatomical location of the intra-atrial electrodes was defined fluoroscopically. C(alpha) was calculated for a moving window (size: 2000 points; step 500 points). Generated C(alpha) was analyzed within 10 minutes before and after administration of propafenone. The inter-regional C(alpha) distribution was analyzed using the Friedman-test (intra-individually) and Kruskall-Wallis-H-test (inter- individually). A value of p=0.05 was set for an error probability. Inter-regional C(alpha) differences were found in all patients (p<0.001). The right atrium could be divided in high- and low complexity areas according to individual patterns. A significant C(alpha) increase in cranio-caudal direction (with the exception of septum) was confirmed inter-individually (p<0.01). The administration of propafenone enlarged the areas of low complexity. CONCLUSIONS: This new method utilizing the combination of symbolic dynamics and adaptive power estimation can provide complex evaluation of the dynamics of AF in man. High-density mapping will be required for further evaluation of results.

Algorithms↗
PubMed2000

Homogeneity and diameter of linear lesions induced with multipolar ablation catheters: in vitro and in vivo comparison of pulsed versus continuous radiofrequency energy delivery.

BACKGROUND: For invasive treatment of atrial fibrillation, linear lesions induced with multipolar ablation catheters (MAC) are needed to prevent recurrence. The aim of the study was to compare the efficacy of pulsed versus continuous radiofrequency (RF)-energy delivery using MAC. METHODS: In vitro tests were performed using endomyocardial preparations of fresh pig hearts in a 10-liter-bath of physiologic saline solution (37 degrees C) at constant flow conditions (1.5 l/min). The MAC were placed with a constant pressure of 20 ponds onto the endocardium. The energy (generator: Osypka HAT 200 S) was delivered either pulsed (4 electrodes simultaneously, 5ms duty-cycle) or continuously (each electrode separately). In vivo experiments were performed in 6 anesthetized pigs using fluoroscopic positioning of MAC at 40 different intracardial positions and with similar conditions as in vitro experiments. Lesion volume (LV) was calculated after measuring lesion diameter with a microcaliper. The homogeneity of the lesions (LH) was classified from 1-4; with 1 as highest homogeneity. RESULTS: Pulsed energy delivery produced more homogeneous linear lesions in significantly less time. There was no difference in electrode temperature values (50.2 +/- 0.8 and 51.3 +/- 1.4 degrees C) in vitro and in vivo. In the in vivo experiments, lesion depth and calculated lesion volume were less in both modes of energy delivery but pulsed energy delivery was superior regarding lesion depth and homogeneity. CONCLUSION: With pulsed energy delivery it is possible to create linear lesions of significantly greater homogeneity. Moreover, larger lesions are induced in less time by pulsed energy delivery in vitro and in vivo.

Animals↗
PubMed2000

Detection of ventricular fibrillation in implantable defibrillators with automatic gain control amplifiers: effects of programming sensitivity.

AIMS: In newer implantable cardioverter-defibrillators with automatic gain control amplifiers the maximum possible sensitivity is programmed with the aim of securing optimal detection of ventricular fibrillation. This study was designed to prove that a reduction in maximum sensitivity is safe with respect to appropriate sensing of ventricular fibrillation, while avoiding sensing of extracardiac signals. METHODS AND RESULTS: Forty-two consecutive patients, undergoing defibrillator implantation/replacement with programmable maximum auto-gain sensing sensitivity (Ventak Mini III, Ventak AV , Guidant, St. Paul, MN, U.S.A.), were prospectively investigated. Thirty-four patients were implanted with a dual-coil lead system, providing integrated bipolar sensing (Endotak, Guidant, St. Paul, MN, U.S.A.), eight patients received a single-coil lead system with true bipolar sensing (Sprint, Medtronic, Minneapolis, MN, U.S.A.). During device implantation and pre-discharge testing, arrhythmia detection times of induced ventricular fibrillation were compared at programmed maximum (0.18 mV) and minimum (0.43 mV) sensitivity in a randomized manner. Seventy-six induced episodes of ventricular fibrillation were analysed. The mean arrhythmia detection times did not differ between the programmed sensing levels (maximum sensitivity: 1612 +/- 307 ms, vs minimal sensitivity: 1,602 +/- 330 ms; P = ns). The results were not affected by the type of implanted lead system (integrated bipolar versus true bipolar sensing). CONCLUSION: In the implantable defibrillator devices, reduction in maximum sensitivity did not impair the detection of induced episodes of ventricular fibrillation.

Amplifiers, Electronic↗