Biomedical subjects
Publications and source records attributed to J Neuzner.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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The aim of this study was to compare the efficacy of pulsed versus continuous RF energy delivery via multipolar ablation catheters. In vitro tests were performed in endomyocardial preparations of fresh bovine hearts in a both of physiological saline solution (37 degrees C) at constant flow conditions (1.5 L/min). The catheters were applied to the endocardium at a constant pressure. Energy was delivered pulsed (to 4 electrodes simultaneously, 5-ms duty cycle) or continuously (to each electrode separately). In vivo experiments were performed under fluoroscopy in eight anesthetized pigs, guided by endocardial electrograms to place the catheters in 22 different intraatrial positions. Lesion volume was calculated from measurements of the lesion diameter with a microcaliper. The homogeneity of the lesions was classified from 1 (highest) to 4 (least). More homogeneous linear lesions were produced in significantly less time with pulsed than with continuous energy delivery. There were no differences in electrode temperature or impedance values in vitro and in vivo. The results in the in vitro experiments were reproducible in the intact animal experiments. Significantly larger and more homogeneous linear lesions were created more rapidly with pulsed than with continuous energy delivery.
Despite increasing evidence of hemodynamic benefit and long-term improvement in clinical status of congestive heart failure (CHF) patients with left ventricular and biventricular pacing, the risks and technical limitations of placing a permanent left ventricular pacing lead have prevented widespread clinical adoption of this therapy. Results of this and other recent investigations suggest it is necessary to target specific sites on the left ventricle to maximize hemodynamic benefit. However, limitations and variations of coronary vein anatomy, as well as patient safety, lead dislodgement, pacing thresholds, lead handling, and ease-of-use issues, present technical challenges for current transvenous permanent pacing lead designs. However, a new transvenous lead system based on an over-the-wire design appears to solve many of these problems and has proved feasible in acute clinical studies.
Whether the safety and efficacy of implantable cardioverter defibrillator (ICD) therapy can be assured with lower output devices is an important question. The purpose of this study was to evaluate whether programming the device output at twice the augmented defibrillation threshold was as safe and effective as using the maximum energy. Patients indicated for ICD therapy, but without slow monomorphic ventricular tachycardia (MVT), who achieved an augmented defibrillation threshold (DFT plus) < or = 15 joules (J) with a single endocardial lead system and a biphasic defibrillator were included in the study. Prior to ICD implantation, patients were randomized into 2 groups. The shock energies in test group patient were set as follows: first shock at twice DFT plus, the second to fifth shocks at maximum output (34 J). In control group patients, all shocks were programmed at 34 J. The study population consisted of 166 consecutive patients (mean age 57.4 +/- 12.1 years, mean left ventricular ejection fraction 36.8 +/- 13.8%). Mean DFT plus was 9.6 +/- 3.2 J in test group patients and 10.1 +/- 3.5 J in control group patients (p = 0.36). During a mean follow-up of 24.2 +/- 9.6 months, 736 arrhythmia episodes were analyzed. The first shock efficacy was 98.3% in the test group patients versus 97.4% in the control group (p = 0.45). Total mortality was 6%, equally distributed in both study groups. The results of this study prove that the method of doubling the defibrillation energy at the DFT plus level provides an adequate safety margin in defibrillator therapy.
The aim of this prospective and randomized study was to evaluate the safety and efficacy of a reduced shock strength in transvenous implantable defibrillator therapy. So far clinical data concerning the safety margin of the shock energy in ICD therapy do not exist. The shock energy tested during long-term follow-up in this study was twice the intraoperatively measured defibrillation threshold (DFT). A total number of 176 consecutive patients representing a typical cohort of ICD patients were evaluated. All patients received a non-thoracotomy lead system (CPI, Endotak 0070, 0090) and a biphasic cardioverter-defibrillator with the ability to store episodes (Cardiac Pacemakers Inc., Ventac TM PRx II, PRx III). The intraoperative defibrillation threshold (DFT) was evaluated in a step-down protocol (15, 10, 8, 5 J) and had to be < or = 15 J for inclusion into the study. The lowest effective energy terminating induced ventricular fibrillation had to be confirmed and was defined as DFT+ augmented defibrillation threshold. The DFT+ value was tested immediately after successful implantation, at discharge, and after a follow-up period of one year. Prior to implantation the patients were randomized into two groups. The energy of the first shock in the study group was programmed at twice DFT+ and in the control group at the maximum energy output (34 J). The efficacy of the first shock and its reproducibility in DFT testings and in spontaneous episodes during long-term follow-up of the study group were compared to those in the control group. A DFT+ value was found to be < or = 15 J in 166 of 176 patients (94%). The DFT+ in the study group was 9.6 +/- 3.2; in control group 10.1 +/- 3.5 J. The prohability of successful defibrillation at DFT+ level after one year was 84%. The success rate of the first shock meant to terminate induced ventricular fibrillation (VF) was 99.5% in the study group (217 of 218 episodes) and 99% in the control group (201 of 203 episodes). During follow-up of 24 +/- 9 months spontaneous episodes in the study group, 83/86 (96.5%) monomorphic ventricular tachycardias (MVT) and 38/40 (95%) VF-episodes were converted successfully by the 2x DFT+ shock. In the control group the first shock was successful in 151/156 (96.8%) spontaneous MVTs and in 30/33 (91%) VF episodes. The efficacy of the first shock was not influenced by clinical data such as the underlying cardiac disease, left ventricular function, ongoing antiarrhythmic therapy with amiodarone, or the number of spontaneous episodes per day or by the DFT itself. At a mean follow-up of two years there was no significant difference between the two groups concerning the incidence of sudden cardiac death (2.4% in the study group vs. 3.8% in the control group). In conclusion programming the first shock with the ICD lead system used in this study at 2x DFT+ is as efficient as a shock energy of 34 J in order to terminate induced and spontaneous episodes of VT/VF. Thus, the safety of ICD-therapy is not impaired when programming the shock energy at the 2x DFT+ value.
UNLABELLED: Automatic mode switching (AMS) function in dual chamber pacemakers depends on adequate detection of atrial tachyarrhythmias. There are few data on showing how intra-operative atrial signal amplititude during sinus rhythm can predict atrial tachyarrhythmias after pacemaker implantation. In 43 patients undergoing DDDR pacemaker implantation and atrioventricular nodal ablation for the treatment of drug-refractory paroxysmal atrial fibrillation, atrial sensing thresholds during sinus rhythm and during induced atrial tachyarrhythmias (24-48 h after device implantation) were analysed. Five different DDDR pacemaker systems were implanted (Chorus 7034, Ela Medical n = 13; Meta DDDR 1254, Telectronics Pacing Systems n = 12; Vigor DR 1230, Guidant n = 6; Trilogy DR 2364, Pacesetter, n = 2; Kappa DR 401, Medtronic USA n = 10). Every patient received a steroid-eluting, screwing, bipolar atrial lead (Medtronic, Capsure-Fix 4068). The mean P wave amplitude during implantation was 3.91 +/- 1.14 mV. The mean atrial sensing threshold during sinus rhythm and during all modes of induced atrial tachyarrhythmias was 3.35 +/- 1.0 mV, and 1.52 +/- 0.92 mV, respectively (P < 0.001). Atrial fibrillation was induced in 36 patients. The mean sensing threshold during sinus rhythm in this patient group was 3.39 +/- 1.01 mV, the mean sensing threshold during atrial fibrillation was 1.27 +/- 0.56 mV, reflecting a 63% reduction of sensing threshold compared with sinus rhythm (P < 0.001). Atrial flutter was induced in seven patients. The mean sensing threshold during sinus rhythm was 2.92 +/- 1.19 mV, the mean sensing threshold during atrial flutter was 2.79 +/- 1.26 mV, reflecting a reduction of 5% (ns) compared with sinus rhythm. Atrial sensing thresholds during sinus rhythm were significantly correlated with sensing thresholds during atrial tachyarrhythmias (r = 0.44; P < 0.002), but there were significant variations in intra-individual results. The reduction of atrial sensing thresholds between sinus rhythm and induced atrial tachyarrhythmias ranged from 30% to 82%. CONCLUSION: Bipolar atrial sensing thresholds during sinus rhythm are correlated with sensing thresholds during atrial tachyarrhythmias, but there is a large degree of variance in individual patients. A 4:1 to 5:1 atrial sensing safety margin based on sensing threshold during sinus rhythm is a predictor for adequate postoperative detection of atrial tachyarrhythmias and the function of AMS devices.
UNLABELLED: Dual chamber ICD systems use two separate leads for sensing. We developed and tested a new prototype of a single pass dual chamber passive fixation lead for dual chamber ICDs. METHODS AND RESULTS: The prototype was a modification of the Guidant CPI Endotak DSP lead. The additional sensing electrode for the right atrium consisted of a side-mounted porous atrial ring electrode (AR). Atrial signals were recorded from the lead in patients during normal sinus rhythm (NSR), atrial fibrillation (AFib), and/or atrial flutter (AFl) with the AR in stable contact with the atrial wall or floating. During NSR, with the AR in contact with the atrial wall, an average P wave amplitude of 7.2 +/- 1.5 mV (mean +/- SD, n = 12) was measured. After induction of Afib/AFl, the single amplitude decreased to 3.6 +/- 1.5 mV (n = 8) during AFib and 3.4 +/- 1.7 mV (n = 9) during AFl. Amplitudes dropped between 53% and 75% when the AR lost atrial wall contact. The atrial pacing threshold was 1.0 +/- 0.4 V (n = 16) when the AR was in contact with the atrial wall. CONCLUSIONS: In future dual chamber ICDs the signals from a passive fixation single pass lead could be used for atrial sensing and pacing as long as the sensing electrode for the right atrium remains in contact with the atrial wall. This system might lead to a simpler, less invasive implantation of dual chamber ICD systems.