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Biomedical subjects

G Breithardt

Publications and source records attributed to G Breithardt.

At least 361 records · Page 20Linked to original sources
PubMed1991

Standards for analysis of ventricular late potentials using high-resolution or signal-averaged electrocardiography: a statement by a task force committee of the European Society of Cardiology, the American Heart Association, and the American College of Cardiology.

Sufficient data are available to recommend the use of the high-resolution or signal-averaged electrocardiogram in patients recovering from myocardial infarction without bundle branch block to help determine their risk for developing sustained ventricular tachyarrhythmias. However, no data are available about the extent to which pharmacological or nonpharmacological interventions in patients with late potentials have an impact on the incidence of sudden cardiac death. Therefore, controlled, prospective studies are required before this issue can be resolved. As refinements in techniques evolve, it is anticipated that the clinical value of high-resolution or signal-averaged electrocardiography will continue to increase.

Analog-Digital Conversion↗
PubMed1991

Implantable cardioverter/defibrillators (ICD): a new lead-system using transvenous-subcutaneous approach in patients with prior cardiac surgery.

The current approach in cardioverter-defibrillator implantation requires placement of epicardial leads which may lead to pericardial and/or pleural effusion and pneumonia during the perioperative period. Although ICD implantation is less invasive than other surgical techniques for the treatment of rhythm disturbances, the perioperative mortality must be considered. Minimizing the operative procedure could lead to a reduction in perioperative mortality. Therefore, we investigated an approach without the need for thoracotomy using a transvenous/subcutaneous lead system. In nine patients with prior cardiac surgery, defibrillator implantation was performed by a transvenous/subcutaneous approach. There was no perioperative mortality. In all patients, a sufficient defibrillation threshold was achieved. The defibrillation pulses were delivered as two sequential pulses between a right ventricular electrode (cathode) and a coronary sinus or superior caval vein electrode (anode 1) and a subcutaneous patch electrode (anode 2). Intubation of the coronary sinus was necessary in 4 patients in order to obtain satisfactory defibrillation thresholds. These data demonstrate that a transvenous/subcutaneous approach is feasible in patients with prior cardiac surgery obviating the need for thoracotomy. Sensing function of the RV-electrode, intubation of the coronary sinus and the intraoperative use of an epicutaneous patch electrode are current problems of this new technique.

Adult↗
PubMed1991

Sodium channel blockers in the treatment of ventricular arrhythmias: different effects in the normal, ischaemic or failing heart?

In past decades, numerous experimental and clinical studies have improved our knowledge of the electrophysiological effects of sodium channel blockers, as well as of the mechanisms of arrhythmogenesis. However, the mechanisms of antiarrhythmic as well as potentially proarrhythmic drug action have been less well clarified. Sodium channel blocker agents have different effects on the normal, ischaemic, and failing heart since their antiarrhythmic actions depend on the substrate and the mechanisms of arrhythmogenesis, as well as other mostly interrelated cardiac and non-cardiac factors. Strict criteria of efficacy and safety have to be applied when sodium channel blockers are used for the treatment of ventricular arrhythmias.

Anti-Arrhythmia Agents↗
PubMed1991

Standards for analysis of ventricular late potentials using high resolution or signal-averaged electrocardiography. A statement by a Task Force Committee between the European Society of Cardiology, the American Heart Association and the American College of Cardiology.

Sufficient data are available to recommend that the high-resolution or signal-averaged electrocardiogram can be used in patients recovering from myocardial infarction without bundle branch block to help to determine their risk for developing sustained ventricular tachyarrhythmias. However, no data are available regarding the extent to which pharmacologic or non-pharmacologic interventions in patients with late potentials have an impact on the incidence of sudden cardiac death. Therefore, controlled, prospective studies are required before this issue can be definitely answered. As refinements in techniques evolve, it is anticipated that the clinical value of high-resolution or signal-averaged electrocardiography will continue to increase in the future.

Arrhythmias, Cardiac↗
PubMed1991

Acute and long-term efficacy of oral propafenone in patients with ventricular tachyarrhythmias.

The class Ic antiarrhythmic agent propafenone was studied by repeated electrophysiologic testing in 54 patients (43 male, aged 54 +/- 10 years, mean ejection fraction of 37.3 +/- 16.9%) with ventricular tachyarrhythmias. Forty patients (74%) had coronary artery disease. Programmed ventricular stimulation (S2, S2S3 during sinus rhythm and/or during S1S1 = 500, 430, 370, and 330 ms) off antiarrhythmic drugs induced sustained ventricular tachycardia, flutter, or fibrillation in all patients. After 450-900 mg of oral propafenone/day for 4-7 days, 51 patients were restudied. In the remaining three patients, spontaneous ventricular tachycardia occurred on drug therapy. Tachycardia induction was suppressed in 9 of 51 patients restudied (18%) and rendered more difficult to induce (basic stimulation drive greater than or equal to 40 beats/min higher than at control study) in another 7 patients (14%) (overall efficacy of 31%). The tachycardia rate decreased from 220 +/- 43 to 177 +/- 44 beats/min (p less than 0.01). The right ventricular effective refractory period increased from 232 +/- 22 to 252 +/- 22 ms (p less than 0.001). Responders to propafenone therapy had higher rates of inducible ventricular tachycardia at control (greater than 230 beats/min: 43%; less than or equal to 230 beats/min: 21%; p less than 0.05), higher ejection fractions, and lower left ventricular end-diastolic pressures than nonresponders. Eleven of the 16 patients showing a positive response to propafenone therapy in electrophysiologic testing were discharged on propafenone alone. During follow-up (17 +/- 12 months), nine patients remained free from ventricular tachycardia, one patient had a relapse, and one patient died of noncardiac death.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1991

Standards for analysis of ventricular late potentials using high-resolution or signal-averaged electrocardiography. A statement by a Task Force Committee of the European Society of Cardiology, the American Heart Association, and the American College of Cardiology.

Sufficient data are available to recommend the use of the high-resolution or signal-averaged electrocardiogram in patients recovering from myocardial infarction without bundle branch block to help determine their risk for developing sustained ventricular tachyarrhythmias. However, no data are available about the extent to which pharmacological or nonpharmacological interventions in patients with late potentials have an impact on the incidence of sudden cardiac death. Therefore, controlled, prospective studies are required before this issue can be resolved. As refinements in techniques evolve, it is anticipated that the clinical value of high-resolution or signal-averaged electrocardiography will continue to increase.

American Heart Association↗
PubMed1991

New approaches to risk stratification after myocardial infarction.

Parameters to assess the presence of electrical instability after myocardial infarction include spontaneous ventricular arrhythmias, late potentials, and programmed ventricular stimulation. The accuracy of the long-term electrocardiogram in correctly identifying high-risk patients has been questioned because spontaneous ventricular arrhythmias also occur in a large proportion of patients who do not develop ventricular tachycardia or sudden death during follow-up (false-positive results). In addition, many patients died suddenly without having these markers. Late potentials, although showing a good correlation to subsequent occurrence of sustained ventricular tachyarrhythmia or sudden death, are also burdened by the problem of a great number of false-positive results. Programmed ventricular stimulation (such as late potentials) assesses the presence of an arrhythmogenic substrate. An abnormal finding such as inducibility of ventricular tachyarrhythmia is predictive of subsequent occurrence of ventricular tachyarrhythmias. Combining these approaches, additionally including a low ejection fraction, subgroups of patients at very high risk of sudden death or sustained ventricular tachyarrhythmia can be identified. Noninvasive procedures (such as Holter monitoring or recording of late potentials) are desirable for screening purposes, whereas it would be acceptable to use more aggressive invasive techniques in certain subsets of patients. A step-like approach using noninvasive recording of late ventricular potentials as the initial step would allow the preselection of patients for further evaluation by invasive electrophysiological techniques.

Humans↗
PubMed1991

[Non-pharmacological treatment of arrhythmia using the method of trans-catheter ablation].

Trans-catheteral ablation is an important therapeutic method for nonpharmacological management of various types of cardiac arrhythmias. Since its introduction into clinical practice in 1982, it has proved its efficacy in disturbance or change of the type of atrioventricular conduction and conduction along accessory abnormal atrioventricular conduction pathways. Positive results have also been attained in the treatment of some patients with ventricular tachycardia. The energy sources used for ablation include direct current pulses possessing large energy, high-frequency currents, and laser energy. Ablation with direct current and high-frequency current is already used successfully in patients, while the use of laser energy for ablation of myocardial arrhythmogenic tissue is limited mainly to operations on the open heart. The use of alternating high-frequency current has attracted particular attention in the last years. Trans-coronary chemical ablation is another recently introduced method which is not connected with the use of electric current. Only experimental and a small clinical experience with this new method has been gained to date. This survey systemasizes the current knowledge of the biophysical bases of the various method of ablation from the standpoint of the mechanisms of treatment, the methodology and the main types of tissue response. Clinical experience with trans-catheteral treatment of cardiac arrhythmias is analysed.

Arrhythmias, Cardiac↗
PubMed1991

[Patient-specific determinants of delay in goal-oriented patient behavior in acute myocardial infarct. Results of the post-infarct late potential study].

369 (63%) of 586 consecutive patients with confirmed myocardial infarction were admitted to hospital within 6 h of symptom onset. Patients' arrival to hospital followed a characteristic circadian distribution with a marked morning increase between 0600 and 1200 hours, and a corresponding decrease in the late night hours. There were no differences in the occurrence of late potentials and in ECG data between early and late arrival group. The early group (less than 5.9 h) was, however, characterized by significantly higher cardiac enzyme levels than the late group (greater than 6.0 h); they also experienced more arrhythmic events in the acute phase (16.0% vs. 9.7%; p less than 0.032). Catecholamines were significantly more often necessary (26.4% vs. 10.3%; p less than 0.0001). Six-month prognosis after AMI was markedly worse. The time between symptom onset and hospital arrival was not affected by age and risk factors. In univariate analysis, pain history and recurrent infarction also had no influence on delay of admission to hospital. The time interval was, however, significantly shorter when the acute event occurred during the night (18.4% vs. 8.3%; p less than 0.0001). Absence of prodromi in the prehospital phase (18.5% vs. 12.0%; p less than 0.04) and a higher socio-economic level (68.3% vs. 61.0%; p less than 0.077) also shortened the admission time, whereas a hyperactive behavioral pattern prolonged the delay time (21.1% vs. 28.9%; p less than 0.05).

Adult↗
PubMed1991

[Initial clinical experiences with a transvenous-subcutaneous defibrillation system].

In 19 patients with an indication for an implantable defibrillator, it was tried to avoid thoracotomy by using two electrodes positioned via the subclavian vein in the right ventricle (for pacing, sensing, and defibrillation) and the superior vena cava or coronary sinus (for defibrillation), and one electrode positioned subcutaneously near the ventricular apex (for defibrillation). In 17 patients (89%) the transvenous-subcutaneous leads were implanted, whereas in the remaining two patients an epi-/pericardial lead system was subsequently used due to an insufficient defibrillation threshold. Perioperatively, no major complications were observed and patients were rapidly mobilized. Within a follow-up period of 7 +/- 4 months, no malfunction of the lead system became evident. Sixty-eight episodes of spontaneous ventricular tachyarrhythmias occurred, all of which were successfully terminated. In one patient an infection of the lead system developed after 2 months that proved refractory to antibiotics and required surgical removal. Thus, transvenous-subcutaneous placement of leads for implantable defibrillators yielded a sufficient defibrillation threshold in the majority of patients. Long-term efficacy was excellent and no malfunctions were observed. This approach seems to be feasible and advisable in patients with an increased risk for thoracotomy.

Adolescent↗
PubMed1991

[Percutaneous endocardial Nd-YAG laser energy: experimental studies of ablation of the ventricular myocardium].

The in vitro and in vivo effects of endocardial laser ablation were assessed. Energy was supplied by a Nd-YAG laser (wavelength approximately 1064 nm) and transmitted via a quartz core fiber (phi: 0.4 mm) housed within a specially designed 7 F catheter. In vitro, the effects of increasing output power (5, 10, 20, 40 watt) and impulse duration (1, 2, 4, 8 s) on lesion size were assessed in myocardial preparations of canine hearts. Preparations were superfused with saline or blood, respectively; the distance of the optical fiber to the endocardium was 5 mm. Lesion size increased in diameter (range: 0-4.0 mm) and depth (range: 0-5.2 mm) in a power- and time-dependent manner. Superfusion with blood significantly enhanced the diameter of the lesions, whereas depth of the lesions significantly decreased. In 16 anesthetized mongrel dogs, a total of 52 laser impulses (output power: 10, 20, 40 w; impulse duration: 1, 2, 4 s; energy: 10-160 J) were delivered to apical and apico-inferior sites of the left ventricle. Postmortem, 40 lesions with a diameter of 2.6-19.4 mm and a depth of 3.7-16.2 mm were found. 19 lesions revealed central vaporized craters with a depth up to 11.2 mm. Perforation of the left ventricle occurred in two cases following 80 and 160 J, respectively. In vitro and in the intact animal (in apical and apico-inferior sites of the left ventricle) endocardial laser ablation is feasible to induce distinct myocardial lesions in a power- and time-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Induction of arrhythmia by licorice abuse].

We report two cases of licorice-induced arrhythmias. In both cases the ingestion of large amounts of licorice caused a marked hypokalemia. The importance of licorice-induced hypokalemia for the development of arrhythmias is underestimated from the small number of published cases. We conclude that patients with a predisposition for arrhythmias should avoid licorice candies.

Adult↗
PubMed1991

Affective disorders and survival after acute myocardial infarction. Results from the post-infarction late potential study.

Psychological data from 560 male survivors of acute myocardial infarction (AMI) were documented in the third week after onset of AMI. The psychodiagnostic assessment was designed to detect different forms of depression as well as hyperactive behaviour. A complete follow-up of these patients, which covers a period of 6 months, is available. Our findings indicate that affective disorders play an important role in the post-acute phase after AMI although the extent of myocardial infarction (as defined by an ECG score) and behaviour responses are not significantly related to one another. Different subforms of depression are not influenced by a history of angina pectoris, the degree and location of myocardial infarction, the occurrence of late potentials and age, whereas dyspnoea (P less than 0.001) and the recurrence of myocardial infarction (P less than 0.001) favour depressive mood states. Twelve cardiac deaths and 17 arrhythmic events occurred during the study period; they were significantly predicted by severe forms of post-AMI depression as revealed by univariate analysis. The evidence was stronger for predicting cardiac death (P less than 0.001) than for arrhythmic events (P = less than 0.035). The effect remains of borderline significance for cardiac death if all risk factors with a significant univariate influence are included in a multiple logistic regression model. The effect of depression is illustrated by Kaplan-Meier survival curves separated for patient groups with high as compared to low degrees of depression. Hyperactivity showed no impact on patient survival.

Adult↗
PubMed1991

[Arrhythmogenic right ventricular disease].

In patients with syncope, ventricular tachyarrhythmias, and sudden death, in the absence of coronary artery disease or dilative and hypertrophic cardiomyopathy, arrhythmogenic right ventricular disease is a common underlying heart disease. It is marked by ventricular tachyarrhythmias of left bundle branch block pattern, often induced by exercise; negative T-waves in the right precordial leads of the surface-ECG, and localized or diffuse right ventricular contraction abnormalities detected by various imaging techniques in a young, apparently healthy population. Congenital disposition with progressive fibrous and lipomatous tissue infiltration of the right ventricular myocardium with hypertrophy and degeneration of surviving myocytes is the pathogenetic factor leading to modification of conduction and resulting in the development of arrhythmogenic zones. This review contains the current knowledge about arrhythmogenic right ventricular disease on the basis of our own experience, and also a review of the literature. Controversial hypotheses concerning etiology and prognosis are discussed. Variant forms and stages of the disease are described, taking differential diagnostic aspects into consideration. Non-invasive and invasive diagnostic methods are evaluated with regard to their diagnostic accuracy, feasibility, and limitations. Pharmacological and alternative therapeutic concepts are presented, including catheter ablation and surgical intervention.

Bundle-Branch Block↗
PubMed1990

Relation between ventricular late endocardial activity during intraoperative endocardial mapping and low-amplitude signals within the terminal QRS complex on the signal-averaged surface electrocardiogram.

Noninvasive recording of ventricular late potentials and intraoperative endocardial mapping at 36 sites were performed in 24 patients with left ventricular aneurysm and drug-resistant sustained ventricular tachycardia due to coronary artery disease. Their mean age was 55 +/- 8 years. Mean ejection fraction was 28 +/- 12%. For detection of late potentials on the signal-averaged QRS complex, 3 different algorithms were used. Late potentials were found in 54, 67 and 67% of the patients, respectively. In patients with a late potential on the signal-averaged electrocardiogram (ECG), delayed local activation (greater than 40 ms beyond the QRS complex on the intraoperative surface ECG) was recorded at 5.5, 5.5 and 5.6 endocardial sites. In patients without a late potential, this type of delayed local activation was detected at 2.4, 1.1 and 0.9 of 36 endocardial sites, respectively (p less than 0.05; p less than 0.01; p less than 0.002). The mean delay of local endocardial activity was 38, 35 and 37 ms in patients with a late potential on the body surface recording versus 20, 19 and 11 ms, respectively, in patients without a late potential (p less than 0.05; p less than 0.05; p less than 0.002). There was no correlation between the duration or amplitude of the late potential, if present, and the number of endocardial sites exhibiting delayed activity (r = -0.23, r = -0.05, r = 0.21; correlation not significant for each) or the mean duration of the endocardial delayed activity (r = -0.25, r = -0.14, r = -0.07; correlation not significant for each). These results indicate that the presence of late potentials on the signal-averaged surface ECG is related to the mean duration of endocardial late activity as well as to the number of endocardial sites exhibiting a given degree of delayed activation. Thus, it is dependent on the mass of slowly activated tissue. However, a direct conclusion from the duration or the amplitude of a late potential to the amount of delayed activation or the extent of endocardial time delay does not seem possible.

Algorithms↗
PubMed1990

Catheter ablation using radiofrequency energy.

Recently, transvenous catheter ablation using radiofrequency impulses has been applied in experimental animals as well as in humans. This review describes the biophysics, mechanisms, and tissue effects of radiofrequency alternating current. Ablation of the AV-junction has been performed in experimental studies as well as in a growing number of patients. Complete AV-block or modification of the AV conduction by RF-current application can be achieved in about 45-65% of patients. Presently about 50% of patients with rightsided accessory pathways can be successfully managed using radiofrequency impulses. Certain limitations exist using a biopolar "epi-endocardial" electrode configuration for leftsided accessory pathways. Only few studies are available concerning the use of RF ablation of ventricular tachycardia foci. As most experimental investigations were carried out in structurally nondiseased myocardium, the use of this new technique in fibrotic or scarred tissue warrants further studies. Radiofrequency catheter ablation seems to be feasible and relatively safe for the treatment of otherwise drug-refractory supraventricular arrhythmias; further studies are needed to assess the safety and efficacy in patients with drug-refractory ventricular tachyarrhythmias.

Animals↗