Biomedical subjects

T Fetsch

Publications and source records attributed to T Fetsch.

25 records · Page 2Linked to original sources

PubMed1994

[Problems with anti-arrhythmia therapy in atrial fibrillation].

The prevalence of atrial fibrillation increases with age, with rates of 2-5% among people over the age of 60 years. Patients may be highly symptomatic or may suffer from hemodynamic compromise or thromboembolic complications. However, antiarrhythmic drug treatment implies problems like the choice of the suitable drug, the individual benefit/risk profile, and alternative treatment strategies. Experimental and clinical data support the concept that atrial fibrillation in the clinical setting in most cases is due to multiple reentrant wavelets. A critical number of three to six simultaneously circulating reentrant wavelets seems to be necessary for the maintenance of atrial fibrillation. Consequently, antiarrhythmic drugs may terminate or prevent atrial fibrillation by prolonging the refractory period or slowing conduction velocity, thereby leading to conduction block. In clinical practice, antiarrhythmic therapy may act by slowing of the ventricular rate due to depression of atrioventricular nodal conduction or by termination and/or prevention of atrial fibrillation. Digitalis is commonly used for the control of the ventricular rate. Betablocking drugs and verapamil are effective in this respect during exercise performance. For antiarrhythmic conversion and prophylaxis of recurrences of atrial fibrillation, class Ia (e.g., quinidine), Ic (e.g., flecainide and propafenone), and class III (e.g., amiodarone and sotalol) drugs of the Vaughan Williams classification are useful. Presently, no general concept exists whether medical or electrical cardioversion should be used as a first line approach for termination of atrial fibrillation. In the individual patient with atrial fibrillation, the potential benefit of restoring sinus rhythm must be weighed against the morbidity and mortality of the arrhythmia and the morbidity and mortality of the antiarrhythmic agents used.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗

PubMed1993

The signal-averaged ECG: time-domain analysis.

During the past decade, the high-resolution electrocardiogram as a non-invasive technique for the detection of ventricular late potentials has developed from an experimental method into a routinely applied non-invasive method for risk stratification of patients after myocardial infarction. Meanwhile, several approaches have been developed for the detection of ventricular late potentials including time-domain analysis, frequency-domain analysis and spectrotemporal mapping. Clinical applications are no longer limited to patients after myocardial infarction, but cover a wider spectrum of different cardiac diseases. This review focuses on some methodological aspects as well as on the results and current clinical applications of the analysis of the signal-averaged ECG in the time domain.

Action Potentials↗

PubMed1993

Late potentials, heart rate variability, and electrocardiography.

Low-amplitude, high frequency components in the terminal QRS-complex (so-called late potentials) are thought to arise from diseased myocardial tissue that forms the "electrophysiologic substrate" for ventricular tachyarrhythmias. Recording of late potentials is now commercially available in several systems and may possibly become clinically routine in the near future. Increased attention has been given recently to heart rate variability as an indicator of conditions of the autonomic nervous system that might trigger ventricular tachyarrhythmias. The value of late potentials and heart rate variability for identification of patients at risk for developing life-threatening ventricular tachyarrhythmias is discussed, as are the other applications and limitations of both methods.

Action Potentials↗

PubMed1993

Signal averaging in patients with coronary artery disease: how helpful is it?

In patients who have survived acute myocardial infarction, the presence of ventricular late potentials using the high resolution signal-averaged ECG indicates areas of slow conduction and delayed activation that may potentially serve as a substrate for malignant ventricular arrhythmias. Although detection of late potentials is technique specific, signal-averaged analysis in the time or frequency domain may be a useful index for risk stratification with regard to ventricular tachycardia or sudden cardiac death. The sensitivity and specificity of late potentials for this purpose may be enhanced by combination with other variables, such as left ventricular ejection fraction and presence of complex ventricular ectopy. Therefore, the presence of ventricular late potentials in postmyocardial infarction patients, particularly in those patients with impaired left ventricular function, identifies those patients who are at high risk of malignant ventricular tachyarrhythmias. However, the strategies for prevention of serious arrhythmia complications during follow-up need to be established. The negative predictive value of late potentials is very high. Thus, the absence of late potentials indicates a low propensity to sustained ventricular tachycardia or sudden death, even in the presence of complex ventricular ectopy. Interventions may therefore not be necessary or should even be avoided. The incidence of late potentials in patients with spontaneous or induced ventricular fibrillation is lower and, if present, less pronounced than in those with sustained monomorphic ventricular tachycardia. This presumably is due to a lower degree of conduction delay, which serves as a substrate for reentry. Therefore, the ability of the signal-averaged ECG to predict a propensity to ventricular fibrillation is limited. Despite these limitations, the signal-averaged ECG may be used as a risk predictor in evaluation of patients after myocardial infarction. Unfortunately, at least as far as time domain analysis is concerned, it cannot be used as an efficacy predictor for response to pharmacologic interventions. Further studies will determine whether other modes of signal-averaged analysis can predict the response to drugs.

Action Potentials↗

PubMed1992

[Ventricular late potentials--methods and clinical importance].

Ventricular late potentials are due to regionally depressed inhomogenous conduction, mainly in the border zone of a previous myocardial infarction. They can be recorded noninvasively using high-resolution signal-averaging techniques. They are almost never detectable in normals, whereas they represent a frequent finding in postmyocardial infarction patients. The presence of ventricular late potentials after previous myocardial infarction predicts the subsequent occurrence of hemodynamically severe sustained ventricular tachycardia and/or sudden cardiac death. Their predictive significance can be increased by combining signal-averaging with long-term ECG recording and estimates of left-ventricular ejection fraction. However, despite recent major improvements in identification of patients at risk, there is still a need for an effective mode of prevention of serious ventricular tachyarrhythmias after myocardial infarction.

Death, Sudden↗

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↗

PubMedDate not supplied

Reduced beat-to-beat changes of heart rate: an important risk factor after acute myocardial infarction.

The prognostic significance of heart rate variability derived from 24-hour electrocardiographic recordings was investigated in 250 patients with acute myocardial infarction. During a follow-up of 6 months 15 patients experienced a serious arrhythmic event. These patients showed a significantly reduced beat to beat variability (p = 0.006), a slightly reduced 5-min variability (p = 0.04) and no significant differences in the 24-hour variability compared to the patients free of arrhythmic events. Based on Cox proportional hazard analysis, beat to beat variability remained an independent risk factor (p = 0.0036) in addition to the presence or absence of ventricular late potentials (p = 0.0004) and history of previous infarction (p = 0.04).

Aged↗