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Biomedical subjects

A Heisel

Publications and source records attributed to A Heisel.

At least 37 records · Page 2Linked to original sources
PubMed1998

Discrimination of sinus rhythm, atrial flutter, and atrial fibrillation using bipolar endocardial signals.

INTRODUCTION: Analysis of endocardial signals obtained from an electrode located in the right atrium as realized in newly designed dual chamber, implantable cardioverter defibrillators might be used to provide additional therapeutic options, such as overdrive pacing or low-energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Therefore, we developed a computer algorithm for discrimination of normal sinus rhythm (NSR), AFL, and AF that may lead to adequate differential therapy of atrial tachyarrhythmias in an automated mode. METHODS AND RESULTS: During an electrophysiologic study, bipolar endocardial signals from the high right atrium were obtained in 28 patients during sustained AFL or AF and after restoration of NSR. A total of 286 data segments of 5-second duration were recorded (NSR: 96, AFL: 86, AF: 104). Mean atrial cycle length (MCL), standard deviation of mean atrial cycle length (SDCL), and index of irregularity (IR), defined as the ratio between MCL and SDCL, were calculated for each data segment. A cutoff of 315 msec for MCL allowed discrimination of NSR from atrial tachyarrhythmias with 100% sensitivity and specificity. For discrimination of AF from AFL by using SDCL, a cutoff value of 11.5 msec led to a sensitivity of 99% and a specificity of 90%. Best discrimination of AF from AFL was found for the criterion IR > or = 7.5%, resulting in a sensitivity of 100% with a specificity of 95% for AF detection. CONCLUSION: The investigated algorithm provides discrimination of NSR, AFL, and AF with high sensitivity and specificity. Incorporation of this algorithm in an implantable automated antitachycardia device may lead to adequate differential therapy in patients suffering from spontaneous episodes of AF and AFL.

Algorithms↗
PubMed1998

Influence of thermal stress on the incidence of acute myocardial infarction in a temperate climate.

Using a Poisson regression model the relative incidence of acute myocardial infarctions (AMI) prospectively registered in 8 hospitals within a radius of 50 km during a 2-year period was correlated with the outside conditions characterized by a complete thermophysiological model (Klima-Michel Model) defining thermal stress. An increase in the incidence of AMI related to thermal stress could be demonstrated neither by splitting the study period into 12 equally sized 'felt-temperature' classes by months of the year nor by single days. This was confirmed by correlation of the AMI rate with the mean felt-temperature level during the preceding 14 days. Thermal stress caused by the atmospheric conditions in a temperate climate may be too weak to influence significantly the incidence of AMI.

Aged↗
PubMed1997

Antitachycardia pacing in patients with implantable cardioverter-defibrillators: inverse circadian variation of therapy success and acceleration.

We analyzed spontaneous ventricular tachycardias treated by antitachycardia pacing during long-term follow-up in 138 recipients of an implantable cardioverter-defibrillator. An inverse circadian variation of the antitachycardia pacing termination and acceleration rates with the worst antitachycardia pacing success during the time period with the highest episode frequency (morning hours) was demonstrated.

Circadian Rhythm↗
PubMed1997

Tolerability of internal low-energy shock strengths currently needed for endocardial atrial cardioversion.

There seems to be no relation between shock strength and patient's tolerability using energy levels currently needed for low-energy internal atrial cardioversion. Every patient felt that the second delivered shock, independent of the amount of energy, was more uncomfortable than the first one, which indicates that psychological conditioning may also play an important role in determining discomfort.

Atrial Fibrillation↗
PubMed1997

Incidence and clinical significance of short-term recurrent ventricular tachyarrhythmias in patients with implantable cardioverter-defibrillator.

Aims of the present study were (1) to investigate the clinical significance of short-term recurrent tachyarrhythmias (STRTs) in ICD recipient, (2) to identify basic characteristics of the subgroup of patients with STRTs and (3) to compare the frequency and circadian pattern of single arrhythmic events and STRTs. We reviewed data from 119 consecutive patients with late generation ICD. All registered spontaneous ventricular tachyarrhythmias were divided into STRTs (defined as two or more consecutive episodes separated by < or =1 h of sinus rhythm) and single events. During a mean follow up of 36+/-18 months (range 2-67 months) 1849 ventricular arrhythmic events were detected in 57 out of 119 ICD recipients (48%). 202 STRTs consisting of 1128 single detection (6+/-7/STRT, range 2-52) occurred in 34/57 patients (60%; 6+/-6 per patient, range 1-21). Recurrent ventricular tachycardias before device implantation and a high number of single arrhythmic events during follow-up distinguished patients with STRTs. Cardiac mortality was significantly higher in patients with STRTs (26 vs. 4%, P<0.05). The majority of both single episodes and STRTs were registered between 8 a.m. and noon and in the evening. This study reveals a high incidence of STRTs in ICD recipients with spontaneous tachyarrhythmias during follow-up and identifies STRTs as prognostic significant events. Comparable circadian variations suggest that similar triggering factors may be involved in the genesis of STRTs and single tachyarrhythmias.

Adult↗
PubMed1997

Coronary implantation of silicone-carbide-coated Palmaz-Schatz stents in patients with high risk of stent thrombosis without oral anticoagulation.

Coronary stenting in bail-out situations is effective but associated with increased stent thrombosis and bleeding rates. Silicone-carbide coating reduces fibrinogen activation on alloplastic surfaces and thus may also reduce stent thromboses. A total of 44 patients received 58 silicone-carbide-coated stents for threatened (80%) or abrupt (20%) closure. In addition to heparin, patients were treated with aspirin and ticlopidine (75%) or aspirin (25%) only. Two patients (4.5%) died in the hospital. The combined in-hospital complication rate including death, emergency revascularization, stent-related myocardial infarction, and stent thrombosis was 9% (4 of 44 patients). Major bleeding occurred in 4 patients (9%). Six-month follow-up angiography was obtained in all eligible patients (42 of 44), revealing a restenosis rate of 21% (9 of 42). Thus, coronary implantation of silicone-carbide-coated stents is feasible in bail-out situations without oral anticoagulation and with a low complication rate. Further studies are required to optimize the anticoagulation regimen with this type of coating.

Adult↗
PubMed1997

Trouser-like stenting: a new technique for bifurcation lesions.

We report on a new technique of stenting a bifurcation lesion. A manually bent 180 degrees hinged slotted tube stent was implanted using the kissing balloon technique (resembling two trouser legs). In addition, the proximal part of the main vessel was covered with a stent mounted on two balloons corresponding to the trousers' waist. This "trousers-like stent technique" ensures open accesses to both vessels not obstructed by stent struts and could be a promising solution for main bifurcation lesions.

Angioplasty, Balloon, Coronary↗
PubMed1997

Factors influencing heart rate variability in patients with severe aortic valve disease.

BACKGROUND AND HYPOTHESIS: Heart rate variability (HRV) is an accepted tool for the assessment of cardiovascular autonomic tone. There are no sufficient data concerning its application to patients with severe aortic valve disease (AVD) requiring cardiac surgery. METHODS: It was the aim of this study to examine HRV and its physiologic correlates in patients with severe aortic valve disease requiring cardiac surgery. The correlates of time domain indices of HRV obtained from 24-h Holter electrocardiographic recordings were analyzed in 36 consecutive patients (23 men and 13 women, mean age 62 +/- 11 years) with AVD prior to cardiac surgery (aortic stenosis: 17 patients, aortic valve regurgitation: 3 patients, combined aortic valve disease: 16 patients). RESULTS: Low values of HRV were found in the entire study group: SDNN 96.8 +/- 30.9 ms, SDNNI 39.3 +/- 14.4 ms, SDANN 86 +/- 28.9 ms, and RMSSD 30 +/- 18.1 ms. In a univariate analysis, there was no significant correlation between the time domain measures of HRV and age, gender, medication, left ventricular ejection fraction, peak aortic pressure gradient, fraction of aortic valve regurgitation, and left ventricular mass assessed by echocardiography. Patients in advanced functional classes of heart failure [New York Heart Association (NYHA) III or IV] had significantly lower values for SDNN (83.8 +/- 33.6 vs. 107.3 +/- 24.7 ms; p < 0.05) and SDANN (72.7 +/- 29.4 vs. 96.6 +/- 24.3 ms; p < 0.05) than patients in NYHA class I or II. Reassessment of HRV 1 week after aortic valve replacement was performed in 17 patients and showed a significant further decrease of SDNN (102.4 +/- 29.7 vs. 61.5 +/- 23.5 ms; p < 0.001), SDNNI (40.7 +/- 13.6 vs. 23.4 +/- 12.4 ms; p < 0.001) and SDANN (91.8 +/- 29.2 vs. 54.2 +/- 22.8 ms; p < 0.001). CONCLUSION: Patients with AVD requiring cardiac surgery reveal reduced time domain indices of HRV. This observation is pronounced in patients with a progressed clinical class of heart failure, whereas hemodynamic and echocardiographic parameters seem to have no significant influence on HRV parameters in this population. In addition, there is evidence of a further reduction of HRV time domain indices 1 week after uncomplicated aortic valve replacement.

Aortic Valve↗
PubMed1997

[Biatrial stimulation in therapy of paroxysmal atrial tachycardia: a case report].

A biatrial pacemaker was inserted in a 68-year-old female with paroxysmal atrial fibrillation and atrial flutter refractory to antiarrhythmic drugs based on a sick-sinus-syndrome and concomitant interatrial conduction delay. One electrode positioned in the right atrium and another electrode located in the coronary sinus were connected to a dual-chamber pacemaker. The electrode in the right atrium was connected to the atrial channel, the electrode in the coronary sinus to the ventricular channel. The pacemaker was programmed in DDD-mode with an AV-delay of 30 ms. Under a chronic antiarrhythmic medication with 160 mg sotalol per day there was no evidence for recurrent episodes of atrial tachyarrhythmias in the patient's history, 24-h-Holter-ECG, nor in the memory of the pacemaker during a follow-up of 8 months.

Aged↗
PubMed1997

Implantable cardioverter-defibrillator therapy: influence of left ventricular function on long-term results.

The degree of left ventricular impairment in an acknowledged important prognostic marker of long-term outcome for patients being evaluated for implantation of cardioverter-defibrillators. Just how left ventricular function impacts freedom from all-cause mortality, as well as from sudden death and cardiac death, is a subject of current major debate, and is analyzed hereunder from a large, recent multicenter ICD patient cohort. The multicenter database consists of data from 361 patients receiving implantable cardioverter-defibrillators for standard indications, that is, documented episodes of ventricular fibrillation or sustained ventricular tachycardias with poor hemodynamic toleration. Data were collected from 1988 to 1995 at three centers in Germany. Two-hundred and three patients (56%) had a left ventricular ejection fraction (LVEF) > 0.30 (group I), and 158 patients (44%) had a LVEF < or = 0.30 respectively (group II). The mean follow-up was 23.9 months (range 3-98 months). Overall survival at 5 years for group II patients was lower, as expected, at 74.1% versus 94.2%, respectively (P < 0.0001). Mortality was higher for each different cause of death in group II patients than in Group I: sudden arrhythmic deaths, 5 versus 1 (P < 0.048); nonsudden cardiac deaths, 16 versus 5 (P < 0.002); noncardiac deaths, 7 versus 2 (P < 0.03). Group II patients received a higher rate of at least one presumably appropriate shock at 86 (54.4%) versus 89 (43.8%) in group I (P < 0.05). However (and somewhat surprisingly), neither the time from ICD implantation to death, comparing only the patients who died, nor the event-free probability of appropriate shocks due to very rapid, sustained ventricular arrhythmias (> 230 beats/min), including a presumed risk of sudden arrhythmogenic death, differed between groups I and II. Sudden cardiac death was only marginally affected by LVEF (group I, 1.5% actuarial, 5-year survival 99.5%; group II, 3.1% and 95.8%, respectively). Therefore, the lower overall survival in ICD patients with LVEF < or = 0.30 resulted mainly from causes of death that cannot be directly influenced by cardioverter-defibrillator therapy. However, because group II patients had a far higher incidence of at least one ventricular tachyarrhythmia terminated by ICD shocks than group I patients, they also probably derived benefit from ICD therapy.

Cohort Studies↗
PubMed1997

Facilitating influence of procainamide on conversion of atrial flutter by rapid atrial pacing.

In a prospective, double-blind, randomized, placebocontrolled study we investigated the facilitating influence of intravenous procainamide on conversion of atrial flutter by rapid atrial pacing. Fifty consecutive patients with spontaneous sustained atrial flutter were 1:1 randomized into two homogenous groups: group A received 10 mg.kg-1 procainamide intravenously, group B placebo. After infusion there was a significant (P < 0.01) lengthening of the flutter cycle with respect to baseline in group A, exceeding the flutter cycle length of the control group (P < 0.05). The overall success rate of rapid atrial pacing in restoring sinus rhythm was significantly higher after pre-treatment with procainamide compared to placebo (100% vs 76%; P < 0.05): 20 patients of group A reverted immediately after pacing to sinus rhythm, the remaining five after a brief episode of atrial fibrillation. In the placebo group, 16 patients showed a prompt conversion to sinus rhythm and three after transient atrial fibrillation. In the remaining six patients, due to sustained pacing-induced atrial fibrillation, direct current cardioversion was necessary. After administration of procainamide a less aggressive stimulation protocol with significantly (P < 0.01) longer paced cycles to interrupt atrial flutter was achievable. In conclusion, intravenous procainamide augments the efficacy of atrial pacing to convert atrial flutter to sinus rhythm.

Adult↗
PubMed1997

Chronic ventricular pacing using an output amplitude of 1.0 volt.

Thirty-seven patients (21 male, 16 female, mean age 71 years) received identical DDD pacemakers. They also received the same bipolar ventricular passive fixation electrode, which has a microporous tip of platinum-iridium, a surface area of 5.8 mm2, and steroid elution. Eighteen months after implantation the ventricular charge threshold [microC] was measured telemetrically at 0.5, 1.0, and 2.0 V, respectively. For the 1.0 and 2.0 V amplitudes the pulse duration was increased until the charge per pulse [microC] was twice the threshold value, thus giving a 100% safety margin in terms of charge ("safety charge"). Patients who had ventricular capture at 0.5 V were permanently programmed to 1.0 V (30/37 patients), while those who did not capture at 0.5 V were set to 2.0 V (7/37 patients). In both cases, the pulse duration was programmed according to the rationale of "safety charge." During a routine follow-up period of 6 months, no complications were observed and none of the patients suffered from symptoms indicating loss of ventricular capture. Twenty-four-hour Holter recordings, obtained from all patients at the end of the follow-up with the output parameters unchanged, revealed constant ventricular capture. In patients with chronic stable pacing thresholds and steroid-eluting low threshold leads who have capture at 0.5 V, chronic ventricular pacing at an output amplitude of 1.0 V is feasible, and it seems to be safe if the pacing threshold is measured as charge delivered per pulse and a 100% safety margin in terms of charge is programmed. Reducing the output amplitude to well below the battery voltage may increase pacemaker longevity.

Aged↗
PubMed1997

Low energy transvenous cardioversion of short duration atrial tachyarrhythmias in humans using a single lead system.

The purpose of this study was to investigate the efficacy and safety of atrial cardioversion using an endocardial single lead system presently used for ventricular defibrillation. The study population consisted of 26 recipients of an ICD in combination with a conventional endocardial single lead system with the proximal spring electrode as anode in the SVC and the distal as cathode in the apex of the RV. Atrial tachyarrhythmias were induced by right atrial burst pacing. If the arrhythmia sustained > 1 minute, biphasic shocks synchronized with the R wave were delivered using the implanted device, beginning with an energy of 4 J. If 4 J failed to terminate the arrhythmia, energy was increased stepwise, if the first shock was successful, a step-down testing was performed after reinduction of atrial tachyarrhythmias. The mean atrial defibrillation threshold was 2.3 +/- 1.2 J (range, 0.5-5 J). A total of 154 shocks were delivered and no adverse effects were observed. The mean defibrillation threshold for atrial flutter was somewhat lower than that for AF (1.8 +/- 1 J vs 2.7 +/- 1.4 J, P = 0.08). There was no correlation between the atrial defibrillation threshold and a history of previously occurring atrial tachyarrhythmias, the kind of the underlying heart disease, a prescription of antiarrhythmic drugs, the dimension of the LA, the LVEF, or the ventricular DFT. Internal atrial cardioversion of short duration atrial tachyarrhythmias using a transvenous single lead system designed for ventricular defibrillation is feasible and safe at low energies, and may have important clinical applications.

Adult↗
PubMed1997

Antitachycardia pacing in patients with implantable cardioverter defibrillators: how many attempts are useful?

The purpose of this study was to determine the termination and acceleration rates for 1 to 6 attempts of antitachycardia pacing [ATP] delivered by ICD in order to terminate spontaneously occurring VTs. Twenty-four ICD recipients with active ATP programs, including a maximum of six ATP sequences and spontaneously occurring VTs during follow-up, were investigated. During a mean follow-up of 42 +/- 15 months (range, 17-63 months) 413 spontaneous VT episodes (17 +/- 14; range, 1-49 per patient) resulting in appropriate ATP delivery by the ICD occurred. ATP successfully terminated 328 episodes (80%) with a mean number of 1.6 +/- 1.1 pacing sequences. Eighty episodes (19%) were accelerated by ATP and 5 (1%) were unresponsive to ATP. The ATP success decreased until the third ATP sequence (59%-->31%-->24%), but increased again in the fourth to sixth attempt (46%-->46%-->29%). The acceleration rate increased from sequence one to sequence three (8%-->13%-->28%), but decreased significantly in further ATP attempts (19%-->0%-->0%). The mean time delays until redetection or termination after 4, 5, and 6 attempts of ATP were 22 +/- 5 seconds, 37 +/- 2 seconds, and 41 +/- 9 seconds, respectively. Nine patients (37%) used > or = 3 ATP attempts during follow-up and all of them had a therapeutic benefit from it. Five out of 13 VTs (38%) treated with > or = 4 attempts could ultimately be terminated by ATP. The results of this study demonstrate that the first ATP sequence is the most effective and that > 4 ATP attempts may be useful in a minority of patients. There seems to be a low risk of VT acceleration by the fourth to sixth ATP sequence. Because of the associated time delay, a high number of ATP attempts should only be programmed in patients with hemodynamically well-tolerated stable VTs.

Acceleration↗
PubMed1997

Low-energy transvenous cardioversion of atrial fibrillation 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. METHODS AND RESULTS: The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet-guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AF. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 +/- 9 min) and eight patients with chronic AF (6.6 +/- 5 months) were included. The fluoroscopy time for lead placement was 3.5 +/- 4.3 minutes. The atrial defibrillation threshold was 2.0 +/- 1.4 J for patients with acute AF and 9.2 +/- 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 +/- 1.1 mV during AF and 4.0 +/- 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 +/- 3.3 V (0.5-msec pulse width). CONCLUSIONS: Atrial signal detection, atrial pacing, and low-energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. This system might lead to a simpler, less invasive approach for internal atrial cardioversion.

Acute Disease↗
PubMed1996

Atrial defibrillation: can modifications in current implantable cardioverter-defibrillators achieve this?

Atrial fibrillation (AF), the most common arrhythmia resulting in hospital admission, is a major health problem. The limited efficacy of antiarrhythmic drugs to control this rhythm disorder and their potential proarrhythmic risk led to the development of new techniques to ameliorate the treatment of AF. Transvenous atrial defibrillation using endocardial electrodes has been shown to be effective at low energy levels. An implantable atrial defibrillator could be a potentially valuable treatment option for patients with paroxysmal AF that is medically refractory. Research is currently under way to investigate several critical issues concerning this new therapeutic concept: long-term efficacy, safety, patient's tolerance, and an acceptable cost/benefit ratio. It is well known that AF often complicates the use of the implantable cardioverter-defibrillator (ICD) for ventricular tachyarrhythmias. Therefore, it would seem desirable to implement the capability for atrial defibrillation into current ICD systems. It has been shown that atrial defibrillation, using endocardial lead configurations specifically designed for ventricular defibrillation, is feasible at energies well within the capabilities of current ICD technology. Further research is needed to evaluate if some enhancement of the lead configuration in combination with possible advanced technology could reduce the atrial defibrillation threshold to a well tolerated level as a prerequisite for automated atrial defibrillation, in ICD recipients with concomitant paroxysmal AF.

Animals↗
PubMed1996

Effects of reperfusion after thrombolysis for myocardial infarction on the signal-averaged electrocardiogram.

Patients with early reperfusion after thrombolysis for acute myocardial infarction revealed a significantly reduced incidence of ventricular late potentials in the signal-averaged electrocardiogram obtained in the chronic post-infarction period in comparison to patients who did not meet the criteria for early successful thrombolysis (14 vs. 39%; P < 0.05). This data demonstrates that early reperfusion might prevent the development of an abnormal electrophysiological milieu after myocardial infarction.

Action Potentials↗