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Biomedical subjects

M Oeff

Publications and source records attributed to M Oeff.

12 recordsLinked to original sources
PubMed1992

A comparison of electrophysiologically guided antiarrhythmic drug therapy with beta-blocker therapy in patients with symptomatic, sustained ventricular tachyarrhythmias.

BACKGROUND: Antiarrhythmic drug therapy guided by invasive electrophysiologic testing is now widely used in patients with symptomatic, sustained ventricular tachyarrhythmias. METHODS: We conducted a prospective, randomized trial in 170 patients to investigate whether this approach would improve long-term outcome. Patients whose arrhythmia was inducible by programmed electrical stimulation were assigned to treatment with electrophysiologically guided drug therapy based on serial testing (61 patients) or with metoprolol (54 patients). Electrophysiologically guided therapy consisted of serial testing of antiarrhythmic agents to identify the first one that rendered the arrhythmia noninducible. The 55 patients whose arrhythmia was noninducible during the initial electrophysiologic test were also treated with metoprolol. RESULTS: During a mean (+/- SD) follow-up period of 23 +/- 17 months, recurrent, nonfatal arrhythmia occurred in 44 patients and sudden death due to cardiac factors in 27. The incidence of symptomatic arrhythmia and sudden death combined was virtually the same in the two groups with inducible arrhythmia after two years of observation (electrophysiologically guided therapy vs. metoprolol therapy, 46 percent vs. 48 percent). The outcome was more favorable in the patients with noninducible arrhythmia at base line (75 percent had neither adverse event) than in those with inducible arrhythmia who were assigned to metoprolol therapy (P = 0.009 by log-rank test). Only 6 of the 29 patients (21 percent) with inducible arrhythmia that became noninducible during drug therapy had recurrent arrhythmia or sudden death, as compared with 21 of the 32 patients (66 percent) with arrhythmia that continued to be inducible (P less than 0.001). A multivariate regression analysis identified continued inducibility of the arrhythmia as an independent predictor of recurrent arrhythmia or sudden death (relative risk, 7.3; 95 percent confidence interval, 2.3 to 23.2; P less than 0.001). CONCLUSIONS: As compared with metoprolol therapy, electrophysiologically guided antiarrhythmic drug therapy did not improve the overall outcome of patients with sustained ventricular tachyarrhythmias. However, effective suppression of inducible arrhythmia by antiarrhythmic drugs was associated with a better outcome than was lack of suppression.

Adrenergic beta-Antagonists↗
PubMed1992

Determination of patch electrode position for the internal cardioverter-defibrillator by cine computed tomography and its relation to the defibrillation threshold.

Cardioverter-defibrillator implantation in 22 consecutive patients after aborted sudden cardiac death was followed by prospective determination of the correct anatomic position of epicardial patch electrodes by chest X-ray study and cine computed tomography; the data were compared with the defibrillation threshold obtained intraoperatively. Patch electrode position was qualitatively graded. Computed tomography improved the assessment as compared with X-ray study in 13 patients (59%), visualizing electrodes in relation to the underlying myocardial and vascular structures. Although the computed tomographic technique provided more precise visualization, its grading of patch position correlated as poorly as that of the X-ray study with the measured acute defibrillation threshold. Three-dimensional reconstruction by computed tomography made it possible to determine quantitatively left ventricular mass (free wall and septum) and the mass encompassed by the patch electrodes. The 34.6 +/- 13.7% (range 12.6 to 61.1%) of the left ventricular mass encompassed by both patch electrodes showed a linear relation to the defibrillation threshold (r = 0.64, p = 0.01). Differentiation of free wall and septal mass in these measurements revealed that the proportion of septal mass encompassed by patch electrodes correlated closely with the defibrillation threshold (r = -0.6, p = 0.019), whereas that of the free wall mass, although significantly larger (35.4 +/- 15.8 vs. 20.6 +/- 15.4 g, p = 0.007), did not. Thus, the position of epicardial patch electrodes could be reliably determined by computed tomography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Ablation of ventricular tachycardia using multiple sequential transcatheter application of radiofrequency energy.

Multiple sequential radiofrequency energy was applied in the left and right ventricles of 24 dogs to produce large ablated areas limited to endocardial and subendocardial regions. Endocardial ablation was performed in nine dogs with normal ventricles and 15 that had survived remote myocardial infarcts, three with inducible sustained monomorphic ventricular tachycardia. A quadripolar catheter was positioned either at the site of earliest ventricular activation during induced monomorphic ventricular tachycardia or at circumscribed areas of the left ventricle. Radiofrequency energy was delivered between two adjacent poles of the catheter, successively applying radiofrequency energy to the distal, middle, and proximal electrode pairs; this was repeated 9 to 11 times with the catheter in a slightly different position. A cumulative energy of 9,688 +/- 4,191 joules resulted in an ablated endocardial/subendocardial surface area of 4.7 +/- 2.2 cm2 (range 2.4-10 cm2, maximum depth 4 mm). Sustained tachycardia was not inducible by aggressive programmed ventricular stimulation in the dogs with previously inducible tachycardia, indicating successful ablation of the tachycardia foci. Only seven normal dogs were available for electrophysiological studies; three were used in acute and four in chronic studies. Ventricular tachycardia was not induced in the remaining dogs either before or after radiofrequency ablation, indicating the lack of an arrhythmogenic effect of this method. Histologic examination was performed in all nine normal dogs (five were sacrificed for acute pathological examination) as well as in the 15 with myocardial infarction. The late pathological examination of the radiofrequency lesion in these 19 animals showed homogeneous areas of coagulation necrosis and endocardial proliferation. Thus, this modified technique of radiofrequency ablation produced large homogeneous endocardial/subendocardial scars suitable for treating ventricular tachycardia and showed no evidence of an arrhythmogenic influence.

Animals↗
PubMed1991

Ablation of the atrioventricular junction with radiofrequency energy using a new electrode catheter.

Percutaneous catheter ablation using radiofrequency energy can be used to interrupt atrioventricular (AV) conduction in patients with supraventricular tachycardia refractory to drugs. Results of radiofrequency ablation of the AV junction using a custom-designed catheter with a large, 3-mm-long distal electrode, 2-mm interelectrode spacing, and a shaft with increased torsional rigidity were compared with those using a standard quadripolar electrode catheter (Bard EP). An electrocoagulator (Microvasive Bicap 4005) supplied unmodulated radiofrequency current at 550 kHz, which was applied between the distal electrode of the ablation catheter and a large skin electrode. With use of the modified catheter, 12 of 13 patients (92%) had persistent complete AV block induced with 7 +/- 5 applications of 18 +/- 6 W of radiofrequency power. In contrast, complete AV block was produced in only 9 of 18 (50%) historical control patients treated with the standard catheter, despite a similar number of applications (7 +/- 5) and power output (16 +/- 4 W). A rise in impedance, due to desiccation of tissue and coagulum formation, occurred earlier (28 +/- 18 vs 52 +/- 24 seconds, p less than 0.001) and more frequently (54 vs 40% of applications, p = 0.047) in patients treated with the standard catheter than in patients treated with the modified catheter. The use of a catheter designed to increase the surface area of electrode-tissue contact allows more radiofrequency energy to be delivered before a rise in impedance occurs and appears to increase the effectiveness of radiofrequency ablation of the AV junction.

Atrioventricular Node↗
PubMed1991

Phase image triangulation of accessory pathways in patients undergoing catheter ablation of posteroseptal pathways.

The outcome of posteroseptal accessory pathway ablation by direct current (DC) shocks delivered just outside the os of the coronary sinus was studied in 21 patients. Electrocardiographic and electrophysiological parameters as well as phase image patterns of equilibrium multiple-gated blood-pool scintigrams were studied to determine their usefulness in predicting the success of ablation. A second free-wall pathway was documented by electrophysiological or surgical findings in six patients, and the value of phase images in detecting this second pathway was studied as well. Ablation was successful in 57%. The cumulative mean energy of DC shocks amounted to 524 +/- 170 joules and was not predictive of ablation outcome, neither was the mean ventriculoatrial (VA) conduction time. The predictive value of the 12-lead maximally preexcited electrocardiogram was poor in the 15 patients with a single posteroseptal bypass tract. A new method to triangulate the site of the earliest phase angle on the atrioventricular (AV) valve plane successfully localized the bypass pathway in 14 of those patients. No specific phase pattern predicted successful ablation except for a symmetrical, concentric peripheral phase progression found to be predictive of ablation success in the four patients who showed this pattern. Phase analysis was able to localize the second, nonposteroseptal pathway in four of six patients. This study showed that a concentric peripheral phase progression in the gated blood-pool scintigrams is predictive for ablation success in patients with posteroseptal pathways. A free-wall localization of the earliest phase angle is suggestive of a second bypass tract in this area.

Adolescent↗
PubMed1990

Inefficacy and proarrhythmic effects of flecainide and encainide for sustained ventricular tachycardia and ventricular fibrillation.

OBJECTIVE: To assess the efficacy of encainide and flecainide in treating patients with sustained ventricular arrhythmias. DESIGN: Patients were treated with encainide or flecainide. Efficacy was assessed by comparing the results of programmed ventricular stimulation while patients received therapy with the results while they were drug free. SETTING: The electrophysiology laboratory of the University of California at San Francisco. PATIENTS: Forty-nine patients with spontaneous or inducible sustained ventricular tachycardia or ventricular fibrillation for whom treatment with at least one class IA antiarrhythmic agent had failed. INTERVENTIONS: Patients were treated with encainide, 35 to 50 mg three or four times daily, or flecainide, 100 to 200 mg twice daily. RESULTS: Arrhythmia worsened early in 5 of 16 patients receiving encainide and 3 of 33 patients receiving flecainide. Patients with poor left ventricular function were more likely to exhibit proarrhythmia (P = 0.02). Nine of eleven patients receiving encainide and 23 of 28 patients receiving flecainide who had repeat programmed ventricular stimulation while receiving drug therapy still had inducible, poorly tolerated ventricular tachycardia. CONCLUSION: Encainide and flecainide have a low efficacy rate and a high incidence of worsening of arrhythmia in patients with sustained ventricular arrhythmias, particularly when this condition is associated with poor left ventricular function.

Adult↗
PubMed1990

Effects of multipolar electrode radiofrequency energy delivery on ventricular endocardium.

This study examined the effects of radiofrequency energy applied in a bipolar fashion with single as compared with multiple sequential applications at the canine endocardium. In this closed-chest model, radiofrequency energy (750 kHz) was delivered between two adjacent poles of an electrode catheter. Single applications were performed at distinct sites in the left (n = 30) and right ventricles (n = 29) of 13 normal dogs. A multiple sequential technique, which enlarges the ablated endocardial surface, was applied in the left (n = 13) and right ventricles (n = 4) of seven normal dogs and six dogs with remote myocardial infarction. Single applications (199 +/- 200 joules) resulted in lesions with a volume of 0.12 +/- 0.06 cm3 (range 0.03 to 0.31 cm3) and an endocardial surface area of 0.29 +/- 0.15 cm2 (range 0.06 to 0.63 cm2). Changes at the catheter/tissue interface led to a rise in impedance, restricting further enlargement of the necrosis. Sequential delivery of radiofrequency energy between poles 1 and 2, 2 and 3, and 3 and 4 of a quadripolar electrode catheter repeated 9 to 11 times in slightly different positions allowed a cumulative energy of 6571 +/- 3857 joules to be applied to the endocardium, resulting in a lesion volume of 0.84 +/- 0.38 cm3, with an endocardial lesion surface area of 3.7 +/- 1.2 cm2 (range 2.9 to 5.1 cm2). Histologically, all radiofrequency lesions were restricted to the endocardium/subendocardium with a small border zone of injury. Aggressive stimulation techniques did not induce ventricular tachycardia in any of the dogs before and 19 +/- 11.4 days after multiple sequential ablations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Catheter ablation of canine myocardium with radiofrequency energy.

High energy direct-current shocks delivered via an electrode catheter have been used to ablate the atrioventricular junction since 1981. This technique has also been adapted for ablation of other cardiac tissues including the atrium, posterior interatrial septum and ventricular myocardium. The limitations of this technique include inadequate control of the energy source, poor understanding of the mechanisms of myocardial injury, and untoward complications possibly related to barotraumatic injury. Radiofrequency energy has been shown to create ablative injury when delivered to the myocardium via standard electrode catheters. This report will review our experience with radiofrequency catheter ablation of the canine myocardium with specific emphasis on the biophysical aspects of lesion formation.

Animals↗
PubMed1986

Methods for non-invasive detection of ventricular late potentials--a comparative multicenter study.

To evaluate the methodological problems of the non-invasive registration of late potentials the results obtained with four different averaging devices in the same 109 patients were compared. The high-resolution ECG was obtained from the body surface, high-gain amplified and filtered. With the averaging technique, the improved signal-to-noise ratio was able to detect low-amplitude cardiac activity. The incidence of late potentials detected with the four averaging systems, whose characteristics are described, ranged between 12% and 21%. Corresponding positive results were obtained in 5.5%, corresponding negative results in 68.8%. The reasons for differing results were mainly due to differences in visual or automatic interpretation of the registered fractionated electrical cardiac activity. Additionally, the determination of the end of QRS using the QRS width, obtained from reference leads, may influence the specificity of the methods.

Cardiac Complexes, Premature↗
PubMed1986

[Noninvasive registration of spontaneous ventricular potentials in patients with healthy hearts and in patients with intraventricular impulsive conduction disorders. Method and results of the signal averaging technic].

For registration of delayed depolarizations 50 healthy persons (age: 49.4 +/- 6.2 years) and 43 patients with bundle-branch block (age: 65.1 +/- 11.8 years; 23 of them with right and 20 with left bundle-branch block) underwent high-resolution electrocardiography at the body surface using signal-averaging technique. The findings were compared with results obtained in the 24-hour long-term ECG. In 2 normal persons (4%), delayed depolarizations were recorded whose configuration, however, differed from that of pathological findings in patients with coronary heart disease. 2 other subjects evidenced repetitive ventricular arrhythmias. Detection of delayed depolarizations in patients with coronary heart disease is indicative of an increased risk of malignant or even fatal arrhythmias. The low prevalence in healthy subjects underlines the specificity of this finding and represents the prerequisite for identifying patients with an increased risk. Delayed depolarizations were found also in 3 patients with right and 4 patients with left bundle-branch block (16.3% in all). 8 patients had repetitive ventricular arrhythmias, and one of them with a left bundle-branch block also revealed delayed depolarizations. Thus delayed depolarizations can be registered in some patients with intraventricular conduction defects. The incidence rate corresponds to that found in patients with coronary heart disease, so that detection of delayed depolarizations in this patient group is not helpful in the assessment of prognosis.

Adult↗
PubMed1979

[Influence of digitalis on pindolol activity in exercise-induced cardiac failure in patients with coronary disease (author's transl)].

The activity of the beta-receptor blocker pindolol (0.4 mg i.v.) was investigated alone and in combination with digitalis (moderately fast loading) in 12 patients with coronary heart disease and without manifest signs of cardiac insufficiency. These patients showed pathological increase of left ventricular filling pressure during exercise testing. The exercise-induced rise of the mean pulmonary arterial and capillary pressures were increased by pindolol. Concurrently the increase of cardiac frequency was clearly diminished during ergometry (from 107/min without pindolol to 96/min, P less than 0.005). Digoxin given orally for an average of 5 days prevented the pressure increase in the pulmonary circulation induced by pindolol during exercise testing and at rest. The frequency reducing effect of pindolol was potentiated by digitalis. Use of digitalis alone did not influence mean exercise-induced pressure increase of the pulmonary circulation. In fact in some cases deterioration of these parameters was observed.

Acetyldigoxins↗