Pitschner Hf

Effectiveness of Cardiac Resynchronization Therapy by QRS Morphology in the Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy (MADIT-CRT)

Background— This study aimed to determine whether QRS morphology identifies patients who benefit from cardiac resynchronization therapy with a defibrillator (CRT-D) and whether it influences the risk of primary and secondary end points in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy (MADIT-CRT) trial. Methods and Results— Baseline 12-lead ECGs were evaluated with regard to QRS morphology. Heart failure event or death was the primary end point of the trial. Death, heart failure event, ventricular tachycardia, and ventricular fibrillation were secondary end points. Among 1817 patients with available sinus rhythm ECGs at baseline, there were 1281 (70%) with left bundle-branch block (LBBB), 228 (13%) with right bundle-branch block, and 308 (17%) with nonspecific intraventricular conduction disturbances. The latter 2 groups were defined as non-LBBB groups. Hazard ratios for the primary end point for comparisons of CRT-D patients versus patients who only received an implantable cardioverter defibrillator (ICD) were significantly (P<0.001) lower in LBBB patients (0.47; P<0.001) than in non-LBBB patients (1.24; P=0.257). The risk of ventricular tachycardia, ventricular fibrillation, or death was decreased significantly in CRT-D patients with LBBB but not in non-LBBB patients. Echocardiographic parameters showed significantly (P<0.001) greater reduction in left ventricular volumes and increase in ejection fraction with CRT-D in LBBB than in non-LBBB patients. Conclusions— Heart failure patients with New York Heart Association class I or II and ejection fraction ⩽30% and LBBB derive substantial clinical benefit from CRT-D: a reduction in heart failure progression and a reduction in the risk of ventricular tachyarrhythmias. No clinical benefit was observed in patients with a non-LBBB QRS pattern (right bundle-branch block or intraventricular conduction disturbances). Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180271.

Programmable VT detection enhancements in implantable cardioverter defibrillator therapy.

This report describes the distribution of automatically measured values of enhanced arrhythmia detection parameters such as “rate stability” and “rate onset” in various forms of spontaneous arrhythmia episodes in patients treated with a new, third‐generation, tiered therapy implantable cardioverter defibrillator (ICD). The study population consisted of 27 patients who received the Ventak PRxII cardioverter defibrillator, which provides extensive diagnostic options such as electrogram storage capabilities, and the ability to store measured values of additional arrhythmia detection parameters such as rate stability and rate onset during spontaneous arrhythmia episodes. During a follow‐up period of 11.1 ± 5.2 months, this device detected 264 arrhythmia episodes. The analysis of stored electrograms revealed 13 episodes of sinus tachycardia, 52 episodes of atrial tachyarrhythmias, and 201 episodes of monomorphic ventricular tachycardias (VTs). The mean measured values of rate stability and rate onset were: 2.2 ± 0.9 msec, 0% in sinus tachycardias; 41.0 ± 24.1 msec, 8.5%± 9.5% in atrial tachyarrhythmias; and 7.8 ± 6.0 msec, 30.6%± 12.1% in monomorphic VTs. There was a wide zone of overlapping measured values for rate stability and rate onset in ventricular and nonventricular rhythms. No episode of VT showed a measured rate stability criterion > 35 msec. The subanalysis of arrhythmia episodes presenting with a heart rate < 160 beats/mm revealed no episode of VT with a rate stability value > 24 msec. The calculated, rate dependent specificities for these programmed rate stability parameters in detecting VTs were 46.2% and 81.8%, respectively. The analysis of the rate onset algorithm revealed no comparable relationship between sensitivity and specificity in the detection of VTs. Additional arrhythmia detection algorithms such as rate stability and rate onset may contribute to a significant enhancement in the specificity of lCD therapy.

Risk Stratification Using Heart Rate Turbulence and Ventricular Arrhythmia in MADIT II: Usefulness and Limitations of a 10-Minute Holter Recording

Background: We evaluated the usefulness of heart rate turbulence (HRT) parameters and frequency of ventricular premature beats (VPBs) for risk‐stratifying postinfarction patients with depressed left ventricular function enrolled in Multicenter Automatic Defibrillator Trial II (MADIT II).

Effect of Biphasic Waveform Pulse on Endocardial Defibrillation Efficacy in Humans

Several clinical studies have proved increased defibrillation efficacy for implantable cardioverter defibrillators with biphasic pulse waveforms compared to monophasic pulse waveforms. This difference in defibrillation efficacy depends on the type of defibrillation lead system used. The influence of biphasic defibrillation pulse waveforms on the defibrillation efficacy of purely endocardial defibrillation lead systems has not yet been sufficiently examined, we, therefore studied 30 consecutive patients with drug refractory ventricular tachyarrhythmias during the implantation of a cardioverter defibrillator. After implanting an endocardial “integrated” sensing/defibrillation lead we performed a prospective randomized comparison of the defibrillation efficacy of monophasic and biphasic defibrillation waveform pulses. For endocardial defibrillation with the biphasic waveform the mean defibrillation threshold was 12.5 ± 4.9 joules and for the monophasic waveform 22.2 ± 5.6 joules (P < 0.0001). There was a decrease in the required defibrillation energy of biphasic defibrillation in 29/30 patients. Thus considering purely endocardial defibrillation a statistically significant and clinically relevant increase in defibrillation efficacy can be demonstrated for biphasic defibrillation waveform pulses.

Safety and efficacy of implantable defibrillator therapy with programmed shock energy at twice the augmented step-down defibrillation threshold: results of the prospective, randomized, multicenter low-energy endotak trial ☆

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.

Safety of Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators and Severely Depressed Left Ventricular Function

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third‐generation implantable Cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety‐one patients with active ATP were followed for 16 ± 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF ± 30% (n = 20), and group B with LVEF ± 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 ± 16 beats/min; group B: 180 ± 21 beats/min; P = NS). Eighty‐three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P ± 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P ± 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first‐shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P= NS). We conclude that ATP is effective and safe in patients with recurrent VTs and severely depressed LV function, and it can be safely programmed in this group of patients to minimize the use of shock therapy.

Implantable Cardioverter Defibrillator: Effect on Survival

On the occasion of William Harveys tercentenary day of death in 1957, Claude S. Beck published papers dealing with differences in myocardial oxygenation and their present and future surgical treatment. He provocatively postulated that by such oxygen differences, hearts otherwise too good to die succumbed to electrical self-execution, thus killing the patients.^-^ In 1957, it was only by chance that such a victim survived, while survival from cardiocirculatory arrest of arrhythmic origin is no longer a rare event. If the estimation that about 50% of all cardiac deaths occur suddenly is approximately correct, then we are faced with a considerable number of hearts too good to die.^ If treatment with an implantable cardioverter defibrillator (ICD) is considered to be effective in saving lives, then knowledge of the number of patients in need of such a device could shed light on the otherwise obscure number.

Interrelation of Tissue Temperature Versus Flow Velocity in Two Different Kinds of Temperature Controlled Catheter Radiofrequency Energy Applications

The influence of blood flow cooling down the energy delivering electrode during temperature controlled radiofrequency energy application is an important factor for ablation success. In this experimental in-vitro study, using tempered saline as blood equivalent, we observed a highly significant increase in tissue temperature, lesion depth and required energy amount with increasing flow velocity. Second, we found significant deeper lesions with use of pulsed radiofrequency energy application compared to continuous application. We conclude that, even with lower electrode temperatures, success can be achieved dependent on the local blood flow velocity, and deeper lesions can be created with the use of pulsed radiofrequency energy application. Background: Success in temperature-controlled radiofrequency (RF) catheter ablation of arrhythmogenic areas in human hearts depend largerly (among others) on the size of the electrode, developed pressure of electrode against tissue, as well as on the localization of the thermistor sensor within the electrode. In addition, the blood flow velocity at various sites of ablation is an important factor for the calculation of heat transport from the electrode, which obviously has not been given much consideration of in the past. The aim of the present in-vitro study, therefore, was to evaluate this important factors influence on the temperature developed at the electrode and within the myocardial tissue. Methods and Results: All experiments were carried out in a bath containing NaCl solution at 37 °C. Four different flow velocities were applied (0, 110, 180, 320 ml/cm2*min). During and after temperature-controlled unipolar radiofrequency energy delivery (60 °C, 40 sec) the electrode temperature, the tissue temperature 5 mm in depth, and the total energy delivered were measured, as well as the actual depth of the lesion. The amount of energy applied to the electrode was regulated by the thermosensor in the electrode to obtain a maximum temperature of 60 °C. Two different kinds of radiofrequency energy delivery have been used: (1) continuous radiofrequency energy delivery as usual regarding clinical use, (2) pulsed radiofrequency energy delivery with a duty cycle length of 10 ms and a pause of at least the same duration during two consecutive duty cycles. At pulsed radiofrequency energy application, the energy for each duty cycle was held constant during delivery. The amount of pulses delivered to the electrode was regulated by the electrodes thermosensor. With both modes of radiofrequency energy delivery a uniform observation could be made. The more the flow velocity applied accelerated, the more the tissue temperature rose (R = 0.85; p < 0.00000001), and the lesion depth increased in spite of electrode temperature being held constant. The amount of the total energy delivered rose in proportion to the cooling down of the electrode dependent on the flow velocity (R = 0.69, p < 0.0000004). Steady-state temperatures had not been accomplished after 40 sec time. When energy was delivered at the pulsed mode, intramyocardial temperatures proved higher compared to the continuous mode with significant differences (p < 0.05) at comparable flow velocities applied between 180 and 320 ml/cm2*min and at same electrode temperatures. This resulted in significantly (p < 0.05) larger lesion depths in pulsed radiofrequency energy delivery. We suppose that this significant difference can be explained by a higher amount of total energy delivered at comparable electrode temperature in the pulsed mode as compared to the continuous mode.

Low-energy transvenous cardioversion of atrial fibrillation using a single atrial lead system.

Atrial Cardioversion Using a Single Atrial Lead System. Introduction: Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option.

Electrophysiological Heterogeneity of Atrial Fibrillation and Local Effect of Propafenone in the Human Right Atrium: Analysis Based on Symbolic Dynamics

A recently developed algorithm that is based on symbolic dynamics and computation of the normalized algorithmic complexity (Cα) was applied to basket-catheter mapping of the atrial fibrillation (AF). The aim of our study was to analyze the spatial distribution of the Cα 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. Cα was calculated for a moving window (size: 2000 points; step 500 points). Generated Cα was analyzed within 10 minutes before and after administration of propafenone. The inter-regional Cα 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 Cα 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 Cα 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.