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Biomedical subjects

G Steinbeck

Publications and source records attributed to G Steinbeck.

At least 55 records · Page 3Linked to original sources
PubMed2000

New mapping technology for atrial tachycardias.

UNLABELLED: Prerequisite for succesful radiofrequency catheter ablation of tachycardias is the exact mapping during the electrophysiological study. The new mapping system CARTO allows a three-dimensional color-coded electroanatomic map of impulse propagation using electromagnetic technology. The aim of this study was to determine the feasibility and safety of the new electromagnetic mapping technology CARTO for atrial tachycardias. RESULTS: Electrophysiologic study and CARTO mapping was performed in 38 atrial tachycardias. The mapping procedure took 26 +/- 23 min. We created 33 maps within the right atrium and 5 maps within the left atrium with a mean of 74 +/- 38 different catheter positions. The mechanism was determined as reentrant in 9, junctional in 1 and focal in 28 tachycardias. In focal tachycardias the tachycardia cycle length (CL) and the total atrial activation time (AT) were clearly different (352 +/- 98 ms vs 99 +/- 25 ms). Reentrant tachycardias had a comparable CL and AT (236 +/- 44 ms vs 240 +/- 56 ms). In 83% of the focal tachycardias and in 67% of the reentrant tachycardias, ablation was performed successfully. No complications occured. CONCLUSION: The electroanatomic mapping system allows high resolution visualization of electrical activity and may therefore improve precision and simplify the determination of the arrhythmogenic substrate during tachycardias for successful catheter ablation.

Adult↗
PubMed2000

Myocardial gene transfer by selective pressure-regulated retroinfusion of coronary veins.

Catheter-based percutaneous transluminal gene delivery (PTGD) into the coronary artery still falls behind the expectations of an efficient myocardial gene delivery system. In this study gene delivery was applied by selective pressure-regulated retroinfusion through the coronary veins to prolong adhesion of replication defective adenovirus within the targeted myocardium. Adenoviral vectors consisted either of luciferase (Ad.rsv-Luc) or beta-galactosidase (Ad.rsv-betaGal) reporter gene under control of an unspecific promotor derived from the Rous sarcoma virus (RSV). In this pig model, selective retrograde gene delivery into the anterior cardiac vein during a brief period of ischemia substantially increased reporter gene expression in the targeted myocardium (LAD region) compared with antegrade delivery as a control. Repeated retrograde delivery during two periods of brief ischemia resulted in a more homogeneous transmural expression predominantly observed in cardiomyocytes (X-gal-staining). In the nontargeted myocardium (CX region) there was no evidence for adenoviral transfection. From our data we infer that selective pressure-regulated retroinfusion is a promising approach for efficient percutaneous transluminal gene delivery to the myocardium. Gene Therapy (2000) 7, 232-240.

Adenoviridae↗
PubMed2000

Catheter ablation of atrial flutter due to amiodarone therapy for paroxysmal atrial fibrillation.

AIMS: Antiarrhythmic drug treatment for atrial fibrillation can cause atrial flutter-like arrhythmias. The aim of this study was to clarify the effect of catheter ablation of the tricuspid annulus-vena cava inferior isthmus on amiodarone-induced atrial flutter and to determine the incidence of atrial fibrillation after catheter ablation of amiodarone-induced atrial flutter in comparison to regular typical flutter. METHODS AND RESULTS: Among 92 consecutive patients with typical atrial flutter who underwent isthmus ablation 28 patients had atrial flutter without a history of previous atrial fibrillation (group I), 10 patients had atrial flutter following the initiation of amiodarone therapy for paroxysmal atrial fibrillation (group II) and 54 patients had atrial flutter and atrial fibrillation (group III). Atrial cycle length during atrial flutter in amiodarone-treated patients (group II) (277+/-24 ms) was significantly longer as compared to the cycle length of atrial flutter in group I (247+/-33 ms) and group III patients (235+/-28 ms). The rate of successful transient entrainment and overdrive stimulation to sinus rhythm was not different between patients with (60%) or without amiodarone therapy (group I: 71%, group III: 53%). Successful isthmus ablation with bidirectional conduction block eliminating right atrial flutter was achieved in 90% of amiodarone-treated patients and 93% of patients without amiodarone therapy. In the amiodarone-treated patient group atrial conduction times during pacing in sinus rhythm were significantly prolonged by 20-30% before and after ablation in all regions of the reentrant circuit. During a mean follow-up of 8+/-3 months post-ablation, atrial fibrillation recurred in two of 10 patients on continued amiodarone therapy after successful isthmus ablation. Thus, successful catheter ablation of atrial flutter due to amiodarone therapy was associated with a markedly lower recurrence rate of paroxysmal atrial fibrillation (20%) as compared to patients with atrial flutter plus preexisting paroxysmal atrial fibrillation (76%) and was similar to the outcome of patients with successful atrial flutter ablation without preexisting atrial fibrillation (25%). CONCLUSION: These data suggest that isthmus ablation with bidirectional block and continuation of amiodarone therapy is an effective therapy for the treatment of atrial flutter due to amiodarone therapy for paroxysmal atrial fibrillation.

Adult↗
PubMed1999

Influence of balloon pressure during stent placement in native coronary arteries on early and late angiographic and clinical outcome: A randomized evaluation of high-pressure inflation.

BACKGROUND: High-pressure dilatation is considered a better stent placement strategy, but this has not yet been proved by appropriately designed studies. The objective of this randomized trial was to assess the role of high-pressure dilatation in the early and late outcome of patients undergoing coronary stent placement. METHODS AND RESULTS: Consecutive patients with coronary stent placement were randomly assigned to high- (15 to 20 atm, 468 patients) or low- (8 to 13 atm, 466 patients) balloon-pressure dilatation. The primary end point of the study was the event-free survival at 1 year. Secondary end points were the incidence of stent thrombosis at 30 days and angiographic restenosis (>/=50% diameter stenosis) at 6 months. The incidence of stent thrombosis was 1.7% in the high-pressure and 1.9% in the low-pressure group (relative risk 0.89; 95% CI 0.30 to 2.56). During the first 30 days, although there was no significant difference in the incidence of Q-wave myocardial infarction, the incidence of non-Q-wave infarction was 6.4% in the high-pressure and 3.4% in the low-pressure group (relative risk 1. 87; 95% CI 1.02 to 3.42). The restenosis rate was 30.4% in the high-pressure and 31.4% in the low-pressure group (relative risk 0. 97; 95% CI 0.75 to 1.26). Event-free survival at 1 year was not significantly different between the groups, with 78.8% in high-pressure patients and 75.5% in patients assigned to low-pressure dilatation (hazard ratio 0.85; 95% CI 0.65 to 1.11). CONCLUSIONS: The systematic use of high-balloon-pressure inflation (15 to 20 atm) during coronary stent placement is not associated with any significant influence on the 1-year outcome of patients undergoing this intervention.

Aged↗
PubMed1999

[Long-term efficacy of antitachycardia pacing for treatment of ventricular tachycardia in patients with implantable cardioverter/defibrillator].

UNLABELLED: Antitachycardia pacing techniques (ATP) have proved useful for termination of ventricular tachycardia (VT). However, little is known about the efficacy and safety off ATP during long-term follow-up in a larger study population. We analyzed the data of 80 ICD patients (pts) with spontaneous monormorphic VT, mean age 59 +/- 12 years, the mean follow-up was 26 +/- 17 months. 50 pts (62.5%) had coronary artery disease, 18 (22.5%) dilative cardiomyopathy (DCM), the remaining 12 pts (15%) had no or other cardiac diseases. 2926 episodes of ventricular tachycardia (cycle length 349 +/- 51 ms, 240-520 ms) occurred in 64/80 pts (80%), overall efficacy of ATP was 89.9%, acceleration occurred in 4.1% of VTs. Success of ATP did not correlate with positive ATP testing on induced arrhythmias, LVEF, NYHA class or aneurysm. Neither underlying heart disease nor antiarrhythmic medication had an impact on the ATP success rate. ATP efficacy was linked significantly to short VT cycle length (VTCL, 240-300 ms, p < 0.01) and long coupling intervals (91-97%), p < 0. 01). Acceleration occurred in 32% of pts and in 4.1% of VT episodes; it was also dependent on short VT cycle length (< 300 ms vs > 300 ms, p < 0.04) and short coupling intervals (< 81% vs >/= 81%, p </= 0. 01). CONCLUSIONS: First, ATP is a highly effective therapy, independent of patients characteristics. Second, short VT cycle length and long ATP coupling intervals were identified as predictors for successful ATP. Best conversation rates were obtained with coupling intervals between 90 and 97% of VTCL in tachycardias with a cycle length < 300 ms. Third, testing ATP on induced VTs before hospital discharge did not improve efficacy, empiric modes showed equal success rates. Fourth, acceleration rate of ATP depends on VT cycle length and coupling interval; therefore, aggressive ATP modes should be carefully applied in patients with VTs faster than 300 ms.

Adult↗
PubMed1999

Identification of ventricular late potentials in the surface electrocardiogram during atrial, atrioventricular sequential, or single-chamber ventricular pacing.

Sudden cardiac death occurs in up to 30% of patients with cardiac pacemakers, caused by ventricular arrhythmias, but in these patients noninvasive risk stratification with Holter, exercise, or standard signal-averaged electrocardiogram is limited. This study investigated whether late potential analysis during cardiac pacing is applicable. In 50 postinfarction patients with documented sustained ventricular tachycardia (VT) and in 50 patients without VT, late potential analysis during sinus rhythm was compared with the corresponding patient's analysis during temporary pacing. During sinus rhythm late potentials were seen in 48 of 50 patients with VT and in 2 of 50 patients without VT. No significant changes were observed during atrial pacing. Modified QRS alignment for signal averaging, QRS endpoint definition, and adjusted cutoff values for abnormality in time and frequency domain analysis allowed retrieval of all late potentials observed during sinus rhythm even in ventricular-paced beats and retrograde conduction. By application of an adjusted analysis to 100 selected patients with permanent pacemakers (50 patients with a history of VT, 50 patients without VT) late potentials were detectable in 44 of 50 patients with VT and in 4 of 50 without VT (sensitivity 88%, specificity 92%). Thus, considering that varying pacing modes, ventricular-paced beats, and retrograde conduction do require modifications of standard late potential analysis, this is an applicable mode for noninvasive risk stratification even in patients with cardiac pacemakers.

Adult↗
PubMed1999

Risk stratification following myocardial infarction in the thrombolytic era: a two-step strategy using noninvasive and invasive methods.

OBJECTIVES: We prospectively performed a two-step risk assessment in patients in the early phase after acute myocardial infarction (MI). BACKGROUND: Noninvasive methods like Holter electrocardiographic monitoring (HM) and determination of the left ventricular ejection fraction (EF) as well as the invasive technique of programmed ventricular stimulation (PVS) have been used to identify patients in the late phase after MI as candidates for prophylactic implantation of a cardioverter/defibrillator. However, it is unclear whether these results can be transferred to patients following acute MI. METHODS: A series of 657 patients with acute MI (< or = 75 years) underwent HM and EF. If one of the two methods yielded abnormal findings (HM > or = 20 ventricular ectopic beats/h/> or =10 ventricular pairs/day/ventricular tachycardia; EF < or = 40%), PVS was done (abnormal PVS: induction of monomorphic ventricular tachycardia, duration >10 s, cycle length > or = 230 ms). RESULTS: Of 657 patients, 304 (46%) had either an abnormal HM or EF. The PVS performed in 146 of 304 patients was abnormal in 22. During a mean follow-up of 37 months, there were 106 (16%) deaths, being sudden in 24 (3.6%), nonsudden cardiac in 45 (6.8%). The incidence of arrhythmic events (sudden cardiac death, symptomatic ventricular tachycardia, cardiac arrest) was 18% (4/22) with an abnormal PVS and only 4% (5/124) with a normal PVS (odds ratio 4.0, p=0.032). CONCLUSIONS: The rate of arrhythmic events is low in post-MI patients in the 1990s. Nevertheless, a two-step risk stratification is helpful in selecting candidates for a defibrillator trial aiming at primary prevention of sudden cardiac death after MI.

Combined Modality Therapy↗
PubMed1999

Functional changes of ventricular late potentials by provocation with increase of heart rate. Evaluation during atrial pacing.

BACKGROUND: Standard methods fail to reveal late potentials in 20 to 30% of patients with ventricular arrhythmias after myocardial infarction. However, these patients may develop transient delayed ventricular activation during increases in heart rate. METHODS AND RESULTS: Atrial pacing was performed, at the rates of 100 min-1 and 120 min-1, in 50 patients after myocardial infarction. Twenty-six patients had a history of documented, sustained ventricular tachycardia, 12 had a history of ventricular fibrillation and 12 no history of ventricular arrhythmias. The low-noise surface electrocardiogram was analysed before and during atrial pacing in the time and frequency domains. Fifteen of 26 patients with ventricular tachycardia, four of 12 with ventricular fibrillation and three of 12 without ventricular arrhythmias experienced late potentials during sinus rhythm. Atrial pacing led to a shift of 26 +/- 15 ms of preexistent late potentials into the ST segment, this being greater in patients with anterior infarctions and to an increase in magnitude in patients with inferior infarctions. In patients without late potentials during sinus rhythm, atrial pacing provoked late potentials in eight of 11 patients with ventricular tachycardia, in four of eight patients with ventricular fibrillation and in one of nine patients without ventricular arrhythmias. Low amplitude signals (LAS) were increased in patients after inferior and filtered QRS in patients after anterior infarction. In 10 patients without cardiac disease no late potentials were detectable in the time and frequency domain either at rest or during increased heart rate. CONCLUSIONS: Increase in heart rate may unmask late potentials in patients prone to malignant ventricular arrhythmias. Therefore, functional late potential analysis with non-invasive clinical stress tests, i.e. exercise tests, should be performed only with an adequate rate response. This might identify patients at risk of malignant ventricular arrhythmias otherwise not identified with conventional late potential analysis.

Arrhythmias, Cardiac↗
PubMed1999

Circadian variability of late potential analysis in Holter electrocardiograms.

Appearance of ventricular tachycardia, ventricular fibrillation, and sudden cardiac death has diurnal variations. We retrospectively studied, using digital Holter electrocardiogram, whether a time course in the appearance of late potentials may be associated with malignant ventricular arrhythmias. The 24-hour recordings in 200 patients after myocardial infarction (50 patients with documented, sustained, monomorphic and reproducibly inducible ventricular tachycardia (< 270/min) (group I), 50 patients resuscitated from ventricular fibrillation (group II), and 100 patients without ventricular arrhythmias (group III) were divided into 24 segments, 60 minutes each. Late potential analysis was performed using the Simson method in the time domain in each segment and compared to a conventional short-term registration. Late potential analysis in conventional short-term recordings during arbitrarily chosen daytimes revealed late potentials in 80% of patients in group I, 38% of patients in group II, and in 16% of patients without ventricular arrhythmias. In at least one 60-minute segment late potentials were found in group I in 92%, in group II in 88% (P < 0.05 vs conventional analysis), and in group III in 19%. Interestingly, in patients with a history of ventricular fibrillation late potentials appeared significantly more often during morning hours (6-12 AM: 82% vs 26% at 12 AM-6 PM, 30% at 6 PM-12 PM, and 42% at 12 PM-6 AM, P < 0.05), especially during phases with heart rate accelerations. Late potential analysis for risk stratification in conventional short-term recordings is feasible for patients prone to ventricular tachycardia, but patients prone to ventricular fibrillation would be more effectively stratified using 24-hour registrations with detection of circadian variations of late potential appearance.

Aged↗
PubMed1999

Ischemia-induced changes of the signal-averaged electrocardiogram: experimental investigation during percutaneous transluminal coronary angioplasty balloon-occluded coronary artery.

INTRODUCTION: The influence of myocardial ischemia on the detection of an arrhythmogenic substrate with the signal-averaged ECG is unclear. METHODS AND RESULTS: In 80 patients with single vessel coronary artery disease and a critical stenosis of the left anterior descending vessel selected after coronary angiography in whom percutaneous transluminal coronary angioplasty (PTCA) was planned, we retrospectively investigated the signal-averaged ECGs in the time domain before, during, and after occlusion of the coronary artery by the PTCA balloon. Forty patients were resuscitated from ventricular fibrillation (VF group), and 40 patients had no ventricular arrhythmia (non-VF group). Late potentials were seen at rest in 26 of 40 patients in the VF group. During ischemia, the duration of the filtered QRS complex and the duration of low-amplitude signals < 40 microV increased significantly. In another 14 patients in the VF group, late potentials were observed only during ischemia. In 4 of 26 patients in the VF group without prior infarction but with severe ischemia present at rest, successful PTCA eliminated preexistent late potentials. In the non-VF group, one patient had late potentials present at rest. In two patients with prior infarction, late potentials were provokable only during transmural ischemia. CONCLUSION: Myocardial ischemia is able to modify detection of an arrhythmogenic substrate with the signal-averaged ECG.

Aged↗
PubMed1998

Molecular basis of transient outward potassium current downregulation in human heart failure: a decrease in Kv4.3 mRNA correlates with a reduction in current density.

BACKGROUND: Despite advances in medical therapy, congestive heart failure remains a major cause of death in the developed world. A disproportionate number of the deaths of patients with heart failure are sudden and presumed to be arrhythmic. Heart failure in humans and in animal models is associated with prolongation of the action potential duration (APD), the result of downregulation of K+ currents-prominently, the Ca2+-independent transient outward current (Ito). The mechanism for the reduction of Ito in heart failure is unknown. The K+ channel alpha-subunit Kv4.3, a homolog of the Drosophila Shal family, is most likely to encode all or part of the native cardiac Ito in humans. METHODS AND RESULTS: We used ribonuclease protection assays and whole-cell electrophysiological recording to study changes in the level of Kv4.3 mRNA and Ito in human tissues and isolated ventricular myocytes, respectively. We found that the level of Kv4.3 mRNA decreased by 30% in failing hearts compared with nonfailing controls. Furthermore, this reduction correlated with the reduction in peak Ito density measured in ventricular myocytes isolated from adjacent regions of the heart. There was no significant change in the steady-state level of any other mRNA studied (HERG, Kv1.4, Kir2.1, Kvss1.3, and the alpha1C subunit of the Ca2+ channel). mRNAs encoding Kv1.2, Kv1.5, and Kv2.1 were found in low abundance in human ventricle. CONCLUSIONS: These data provide further support for the hypothesis that Kv4.3 encodes all or part of the native cardiac Ito in humans and that part of the downregulation of this current in heart failure may be transcriptionally regulated.

Action Potentials↗
PubMed1998

[Radiofrequency catheter ablation of atrial flutter and atrial fibrillation].

Radiofrequency catheter ablation is now considered as a curative approach in patients with typical atrial flutter. Typical atrial flutter is due to a macrore-entrant circuit within the right atrium and it can be eliminated by a linear lesion in the isthmus between the tricuspid annulus and the vena cava inferior. The electrophysiological criterion of a bidirectional isthmus block has been shown to reduce the recurrence rate of atrial flutter after catheter ablation, thus achieving long-term cure of typical atrial flutter. Acute success rates of 85 to 90% and recurrence rates of 10 to 15% have been reported. The risk of paroxysmal atrial fibrillation continues to be clinically relevant in patients who underwent successful ablation of atrial flutter, in particular in patients with previously documented atrial fibrillation. The incidence of a new onset of atrial fibrillation after ablation of atrial flutter seems to be approximately 20%. Isthmus ablation has also been shown to be beneficial for the majority of patients with typical atrial flutter and atrial fibrillation: In addition to an elimination of typical atrial flutter the isthmus ablation apparently reduces the incidence of paroxysmal atrial fibrillation. At present, atrial fibrillation can only be treated by catheter ablation as a curative approach in the rare cases where an accessory pathway, an AV nodal re-entrant tachycardia, typical atrial flutter or an ectopic atrial tachycardia is the induction mechanism of the atrial fibrillation. The majority of patients with atrial fibrillation is apparently not amenable to a curative local ablation. While AV junction ablation and AV node modification can palliate some of the symptoms of atrial fibrillation by a control of ventricular rate, the arrhythmia persists with the loss of AV synchrony and continued risk of thromboembolism. The surgical MAZE procedure implies a compartimentation of the atria by surgical incisions resulting in areas to small to sustain the arrhythmia. Based on this procedure experimental and clinical studies are currently performed in order to develop catheter ablation cure of atrial fibrillation.

Atrial Fibrillation↗
PubMed1998

[Significance of calcium detection with electron-beam tomography in coronary disease].

PURPOSE: Coronary calcium is a powerful indicator of arteriosclerosis and can be detected very precisely with electron beam tomography. The method can be applied in patients with known coronary artery disease or in asymptomatic patients at risk of arteriosclerotic disease. METHODS: The standard protocol of EBT consists of 30 to 40 slices of 3-mm thickness with a scan time of 100 ms, no overlap. No contrast medium is needed. The total scan can be performed within one breathhold. The calcium score is calculated as described by Agatston. Radiation exposure amounts to 0.8 mSv per total screen. We used spiral CT with and without ECG trigger as an alternative. RESULTS: At the University of Munich we performed an EBT scan of the heart in 1100 patients within the last year. In 567 patients coronary angiography was performed also (+/- 3 days). Confirming previous reports in the literature, we found a correlation of the calcium score with the age and gender of the patients. Severe coronary artery disease (stenoses > or = 75%) was associated with significantly more calcium than less severe CAD. The calcium score did not discriminate between one-, two- and three-vessel disease. The site of calcification does not correlate with the localization of stenoses. Thirty-three percent of the patients with significant coronary artery disease showed a normal age-adjusted calcium score; a total of 8.1% of patients with severe stenoses did not reveal any coronary calcification (score = 0). With asymptomatic patients there are only a few studies available. Soft plaques cannot be detected with EBT, but in most patients soft plaques occur together with hard plaques. Our results show that spiral CT of the newest generation may also be used for calcium screening. There was an excellent correlation of the calcium scores of EBT and spiral CT at all levels of calcification. DISCUSSION: Coronary calcium is a sensitive marker of coronary artery disease. In the clinical setting EBT is indicated in patients with known coronary artery disease (to evaluate prognosis), in patients who are unable to perform a stress test, and in patients with atypical chest pain. However, lack of calcification may be associated with severe stenoses in a minority of patients. The clinical value in asymptomatic patients needs to be defined: randomized studies are necessary. We see a possible indication in patients with known risk factors, in whom primary preventive strategies could be performed more selectively and cost-effectively.

Adolescent↗