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Biomedical subjects

M Manz

Publications and source records attributed to M Manz.

At least 91 records · Page 5Linked to original sources
PubMed1992

Failure of an implantable cardioverter-defibrillator to redetect ventricular fibrillation in patients with a nonthoracotomy lead system.

BACKGROUND: Shock delivery of an implantable defibrillator may cause a change in the amplitude of endocardial electrograms and impair the detection of ventricular fibrillation. Thus, the effects of shock discharges on the amplitude of endocardial electrograms were evaluated in five patients undergoing implantation of a cardioverter-defibrillator in combination with a new nonthoracotomy lead system. METHODS AND RESULTS: At implant, bipolar endocardial electrograms were recorded before each shock application, during ventricular fibrillation, during redetection of ventricular fibrillation in case the applied shock was ineffective, and at intervals of 5, 10, 20, 30, 60, and 120 seconds after each shock delivery. The amplitude of the endocardial electrograms decreased from 10.5 +/- 3.8 mV during sinus rhythm to 6.3 +/- 1.9 mV during initial ventricular fibrillation and declined to 2.2 +/- 1.3 mV during redetection of ventricular fibrillation. After successful termination, the following bipolar electrograms could be obtained at the predetermined intervals: 1.9 +/- 1.2 mV, 3.1 +/- 1.8 mV, 4.5 +/- 1.9 mV, 6.5 +/- 2.9 mV, 9.5 +/- 3.3 mV, and 10.4 +/- 3.8 mV. At predischarge testing, failure of redetection of ventricular fibrillation could be documented in two patients, requiring rescue external defibrillation in both cases to restore sinus rhythm. CONCLUSIONS: These findings demonstrate that the implantable cardioverter-defibrillator did not ensure reliable redetection of ventricular fibrillation in patients using the implanted nonthoracotomy lead system. Thus, the potential risk of sudden cardiac death may persist in these patients despite defibrillator therapy.

Cardiomyopathy, Dilated↗
PubMed1992

[Combination anti-arrhythmic drug therapy].

Antiarrhythmic treatment with single agents is often ineffective and can be limited by dose-dependent side-effects. Therefore, combinations of antiarrhythmic drugs in smaller and well-tolerated doses are advocated in cases refractory to single antiarrhythmic drugs. Basically, substances belonging to the same electrophysiologic class should not be combined. A combination of beta-adrenoreceptor blockers with class I antiarrhythmic drugs may be effective, mainly in cases in which the arrhythmia is dependent on adrenergic stimulation. As shown in our study, the combination of class III and I B-substances can be useful in some cases, from the electrophysiological and clinical points of view. Among the successful combinations of this type are amiodarone and mexiletine, sotalol and mexiletine, and sotalol and tocainide. In patients refractory to amiodarone alone or to a combination with mexiletine, the combined treatment with amiodarone and class-I-C drugs such as flecainide and encainide prolongs the cycle length of ventricular tachycardia, but does not suppress induction of ventricular tachycardia during programmed stimulation. Combination therapy with amiodarone and encainide is associated with a remarkable incidence of proarrhythmic effects. Nevertheless, a combination of antiarrhythmic drugs improves efficacy of therapy in selected patients. However, a close monitoring is mandatory because of the risk of proarrhythmia.

Amiodarone↗
PubMed1992

[Wolff-Parkinson-White syndrome: regional endocardial potential and efficacy of high frequency ablation].

The aim of the study was the evaluation of results of radiofrequency (RF) catheter ablation in relation to characteristics of regional endocardial potential morphology. 418 RF current deliveries in 26 patients with anterogradely conducting left-sided accessory pathways (AP) were investigated. A large regional atrial deflection (> 1/4 of ventricular potential) prior to RF discharge is a prerequisite for ablation success using the ventricular approach. A failing or extremely short (< 10 ms) isoelectric interval between atrial and ventricular deflections of the regional potential predicts a block of the AP. A persistent block can be expected if the regional electrogram contains an AP potential and the AP block occurs early (< 5 s) during onset of RF current.

Adult↗
PubMed1992

[Who should be referred for electrophysiologic studies?].

Prerequisite of a rational antiarrhythmic therapy is the correct diagnosis of the given cardiac rhythm disorder. The majority of intermittent and latent cardiac arrhythmias can be reliably induced and analyzed during the electrophysiologic study (EPS). In case of bradyarrhythmias, the method is indicated in patients with suspected sinus node disease or high-grade AV conduction disturbances, as far as the cause of clinical symptoms cannot be settled by Holter recordings. Since patients with paroxysmal supraventricular tachycardias (WPW syndrome and AV nodal reentrant tachycardia) can be cured by transvenous ablation techniques, EPS is indicating in this setting in all symptomatic patients for the diagnosis and the treatment of the given arrhythmia. In patients with recurrent ventricular tachyarrhythmias, EPS should be performed to establish the diagnosis and to control medical treatment; in addition, EPS is a prerequisite for nonpharmacologic treatment modalities such as defibrillator therapy and transvenous or surgical ablation techniques. In survivors of cardiac arrest without new Q-wave myocardial infarction, persistent ventricular tachyarrhythmias can be induced in some 50% of the patients. Patients should be evaluated by EPS in case the reasons for significant clinical symptoms cannot be determined otherwise, given the likelihood, that brady- or tachyarrhythmias are the cause of the clinical symptoms; this includes patients with organic heart disease and with unexplained syncopes.

Arrhythmias, Cardiac↗
PubMed1992

[Clinical assessment and indications for automatic defibrillation].

A variety of therapeutic options including pharmacological treatment, surgical procedures, ablation interventions and electrotherapy are available for the management of patients who are subject to symptomatic ventricular tachyarrhythmias. Patients with documented sustained ventricular tachycardia or ventricular fibrillation are usually controlled by serial electrophysiological studies. About 30 to 60% of these patients respond to antiarrhythmic drugs during serial electrophysiological testing. Patients with severe left-ventricular function respond less frequently than those of well-preserved function. Long-term follow-up studies have demonstrated that, if ventricular tachyarrhythmias can no longer be induced on antiarrhythmic drugs or if inducibility is at least rendered more difficult, the rate of recurrences is low. In contrast, patients with still inducible ventricular tachyarrhythmias may have a poor prognosis and may suffer from frequent recurrences or may even die suddenly. Thus, nonpharmacological strategies such as an implantable cardioverter/defibrillator, transvenous catheter ablation and map-guided antitachycardia surgery have become important alternatives for drug refractory patients. Since the introduction of the implantable cardioverter/defibrillator using a nonthoracotomy approach, the intraoperative and perioperative mortality and morbidity has been significantly reduced. A widespread use of these newer devices required the establishment of guidelines for the appropriate application of this new treatment modality. Surgical, medical and economic considerations make it imperative that defibrillator therapy should be chosen on a basis of careful patient selection. The presenting clinical arrhythmia and its hemodynamic stability, underlying heart disease and left-ventricular ejection fraction should be taken into consideration.(ABSTRACT TRUNCATED AT 250 WORDS)

Electric Countershock↗
PubMed1992

[Transluminal coronary extraction atherectomy. Method, acute results, angiographic and clinical follow-up].

Transluminal coronary extraction-endarterectomy is an alternative interventional approach for treatment of coronary artery disease. The atherectomy system consists of a catheter assembly including a cutter and torque tube which is rotated at a relatively low rate of 750 rotations per minute, when introduced to the coronary artery over a guide-wire via a guiding catheter. Excised tissue is withdrawn from the coronary artery by suction applied through the catheter by means of an attached vacuum bottle. We report acute results in 18 patients and the clinical outcome of 14 patients who up to now underwent angiographic follow-up catheterization after 6 months. Initial angiographic success (residual stenosis less than 50%) using TEC-atherectomy alone was obtained in 6/18 patients (33%), 11/18 patients (60%) required additional PTCA in order to achieve primary success (9/18) or to treat total occlusion (2/18) after TEC-atherectomy. Major complications consisted in 1-vessel perforation with non-Q-wave-infarction but no need of surgical intervention and 2 occlusions due to dissection (treated with PTCA). 14 patients underwent angiographic follow-up (6 months) and restenosis (greater than 50%) was confirmed in 7 patients (50%). Considering the low primary success rate of TEC-atherectomy alone and the tendency to high restenosis rate, we cannot recommend it as an alternative to conventional PTCA in general clinical practice. Further studies should be designed to directly compare TEC-atherectomy to PTCA in specific patient subgroups (e.g. bypass grafts, intraluminal thrombus, diffuse disease) in order to define the role of this interventional device.

Adult↗
PubMed1992

[Sudden cardiac death--possibilities and limits of drug therapy].

Sudden cardiac death is a challenge for primary prevention efforts, the rescue system, and the prophylactic antiarrhythmic medical therapy. A prerequisite for the successful prevention is insight into the pathophysiologic interaction of the arrhythmogenic substrate, the ischemic events, the autonomous nervous system, ventricular premature beats, left-ventricular function, etc. Latest results of prophylactic antiarrhythmic therapy indicate that the benefit under a specific antiarrhythmic treatment depends on the ratio of antiarrhythmic to proarrhythmic effects and the prevalence of sudden cardiac death in a given population. In diseased hearts with ventricular tachycardia or ventricular fibrillation the chance of sudden cardiac death is high, therefore, antiarrhythmic therapy is indicated and should be controlled by programmed stimulation. In patients with a low likelihood of sudden cardiac death after myocardial infarction, beta receptor blockers should be given; in certain higher risk patients (non-sustained ventricular tachycardia, reduced left-ventricular function) class-III antiarrhythmic agents are recommended. In hypertrophic cardiomyopathy (less in dilative cardiomyopathy) a beneficial effect of amiodarone becomes apparent in subgroups with high risk. Treatment of symptomatic ventricular premature beats remains empiric; in case of no or minimal structural heart disease, the arrhythmogenic potential is low. For the management of recurrent ventricular tachycardia new concepts are proposed that include antiarrhythmic agents and magnesium.

Anti-Arrhythmia Agents↗
PubMed1991

Fetal tachyarrhythmias: transplacental and direct treatment of the fetus-a report of 60 cases.

From 1981 to 1990, 60 fetuses with tachyarrhythmia (21-39 weeks of gestation) were treated in utero. Of these, 54 were cases of supraventricular tachycardia, and six of atrial flutter. Non-immune fetal hydrops was present in 21 cases with supraventricular tachycardia and in five cases with atrial flutter, a total of 26 cases.Transplacental treatment by maternally administered antiarrhythmic drugs (digoxin only or in combination with verapamil) produced good results in non-hydropic fetuses. In this group, all 34 fetuses survived. In fetuses with hydrops, 20 out of 26 survived. In 13 fetuses of the 26 with hydrops, direct fetal therapy was performed in addition to the transplacental therapy when the tachyarrhythmia was refractory to transplacental treatment. During the 9 years of this study, a variety of direct treatment regimes have been used consisting of intraperitoneal and/or umbilical intravenous administrations of different drugs. Since 1988, umbilical vein punctures have shown that the transplacental passage of digoxin (and amiodarone) is hampered in the presence of hydrops, and direct treatment may he necessary in these cases. Amiodarone seems to he the drug of choice for direct therapy. It is highly effective in supraventricular tachycardia and atrial flutter. The long elimination half-time of amiodarone reduces the number of umbilical cord punctures needed to maintain the therapeutic drug level in the fetus.

Journal Article↗
PubMed1991

Comparison of two antitachycardia pacing modes in supraventricular tachycardia.

The comparative efficacy of two different antitachycardia pacing techniques was evaluated in 22 consecutive patients who received the pacemaker Intertach with an atrial electrode for drug refractory, recurrent supraventricular tachycardia (SVT). The Intertach has two consecutive programmable primary and secondary termination modes. The termination programs investigated were adaptive autodecremental burst pacing and adaptive decremental scanning. Atrioventricular nodal reentrant tachycardia was present in 15 patients and atrioventricular reentrant tachycardia due to Wolff-Parkinson-White syndrome in seven patients. The prospective comparison was arranged in a randomized, cross-over study over a period of 12 months. To assess long-term efficacy, diagnostic data of the pacemakers were obtained in intervals of 3 months. In addition, noninvasive programmed stimulation was performed to compare the incidence of pacing-induced atrial fibrillation with both termination programs. During a follow-up of 12 months the overall success rate of autodecremental burst pacing and decremental scanning was 80% and 95%, respectively. Decremental scanning was more effective in 12 patients and less successful in two patients than autodecremental burst pacing. During noninvasive electrophysiological studies, pacing induced atrial fibrillation could be documented in three of ten patients (30%) using autodecremental burst pacing, compared to one of ten patients (10%) using decremental scanning. These data suggest that decremental scanning proved to be more successful in the long-term management of patients with recurrent SVT than autodecremental burst pacing. Furthermore, the occurrence of pacing-induced atrial fibrillation could be documented more frequently with autodecremental burst pacing compared to decremental scanning.

Algorithms↗
PubMed1991

Combination of antiarrhythmic drugs.

Antiarrhythmic treatment with single agents is often ineffective and can be limited by dose-dependent side effects. Therefore, combinations of antiarrhythmic drugs in smaller and well-tolerated doses are advocated in cases refractory to single antiarrhythmic drugs. Basically, substances belonging to the same electrophysiologic class should not be combined. However, drugs of different subsets of class I may be combined. Agents that have pharmacokinetic interactions, such as quinidine and amiodarone, should not be given together because this combination may be associated with a considerable proarrhythmic effect. A combination of beta-adrenoreceptor blockers with class I antiarrhythmic drugs may be effective, mainly in cases in which the arrhythmia is dependent on adrenergic stimulation. The combination of class III and IB substances can be useful in some cases, from the electrophysiological and clinical point of view. Among the successful combinations of this type are amiodarone and mexiletine, sotalol and mexiletine, or sotalol and tocainide. In 34 patients, the reduction of ventricular premature beats by sotalol alone was 28%, and by sotalol plus mexiletine or tocainide was 79%. Complex ventricular arrhythmias were suppressed by sotalol alone by less than 40% and by sotalol plus mexiletine or tocainide by more than 80%. There was no difference in the effectiveness of mexiletine and tocainide (both of them being class IB drugs) in this combination. However, mexiletine was associated with fewer adverse effects than was tocainide. In patients refractory to amiodarone alone or to a combination with mexiletine, the combined treatment with amiodarone and class IC drugs such as flecainide and encainide prolongs the cycle length of ventricular tachycardia, but does not suppress induction of ventricular tachycardia during programmed stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Which programmable functions of pacemakers are available, and what is their clinical relevance?].

Microprocessors incorporated into cardiac pacemakers enable a substantial number of programmable functions (Table 1), the clinical relevance of which is the subject of this overview. Stimulation mode: The mode of operation can be chosen as fixed-rate, triggered and inhibited stimulation. Rate: Rate-programmability enables optimal setting with respect to electrophysiologic and hemodynamic considerations. Impulse amplitude and width: With programmable impulse amplitude and width excessive stimulation energy can be avoided and the duration of the aggregate prolonged. In some pacemakers, the output current can be chosen as "unregulated or regulated" whereby with regulated current the magnitude of the output impulse remains constant until the battery is depleted. Functional impairment of the pacemaker through threshold elevation or muscle stimulation can be eliminated by reprogramming of the impulse amplitude or width. Sensitivity: Programmability of the input sensitivity enables noninvasive counteraction of detection disturbances (as undersensing especially with low-amplitude atrial signals and oversensing of interference signals with subsequent pacemaker inhibition; Figure 1). A new option, automatic sensitivity setting, regulates the registration of cardiac activity at the atrial and/or ventricular level within a safety margin of 2:1; even though somewhat problematic, undersensing is rare. Electrode polarity: Depending on the clinical situation, the unipolar or bipolar electrode may offer advantages. The programmability of the electrode polarity accordingly represents a clinically-relevant new development which provides a favourable combination of bipolar detection and unipolar stimulation. Some modern dual-chamber systems enable separate programming of the atrial and ventricular electrode configurations. Hysteresis: For single-chamber systems and, more recently, AV-sequential pacemakers, hysteresis is optionally available, that is, a programmable prolongation of the basic interval after detection of a spontaneous cardiac event. With further refinement, the so-called search hysteresis prolongs the stimulation interval after a constant number of continuous stimulation cycles to a programmed hysteresis interval to allow spontaneous cardiac activity; if this is detected during the prolonged interval, the pacemaker is inhibited, otherwise the pacemaker stimulates at the set rate. An AV-interval hysteresis - to date only available in one pacemaker system - prolongs the duration of the AV-interval in the following cycles to a programmed interval, if, within the programmed AV-interval, spontaneous AV-conduction is detected. Additionally, after a defined number of AV-cycles an AV-interval prolongation is chosen to assess the possibility of physiologic AV-conduction. AV-interval: Modern AV-sequential pacemakers incorporate integration of the differential and rate-adaptive AV-interval.(ABSTRACT TRUNCATED AT 400 WORDS)

Algorithms↗
PubMed1991

[Heart-minute volume during persistent ventricular tachycardia: anti-arrhythmia intervention using ajmaline].

The hemodynamic effect of the intravenous application of ajmaline (50 mg) was studied during persistent ventricular tachycardia. With the onset of ventricular tachycardia an increase of heart rate up to 177 +/- 40 bpm and a simultaneous decrease of cardiac output from 7.1 +/- 2.7 l/min to 3.4 +/- 1.1 l/min (p less than 0.001) could be demonstrated. Ajmaline prolonged the QRS interval and slowed the ventricular tachycardia rate to 133 +/- 28 bpm. Simultaneously, an increase of cardiac output to 5.9 +/- 2.3 l/min (p less than 0.001) could be documented. A significant correlation between the increase of cardiac output and the change of ventricular tachycardia rate was found. A drug-induced termination of ventricular tachycardia by ajmaline was possible in 60% of patients. Intravenous application of ajmaline during persistent ventricular tachycardia leads to a hemodynamic improvement caused by the reduction of the tachycardia rate. This temporary stabilization of the hemodynamic status is important for emergency treatment of ventricular tachycardia.

Adult↗