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Biomedical subjects

G Breithardt

Publications and source records attributed to G Breithardt.

At least 397 records · Page 22Linked to original sources
PubMed1989

Radiofrequency coagulation of ventricular myocardium: improved prediction of lesion size by monitoring catheter tip temperature.

To assess the importance of voltage, current, impedance and catheter tip temperature for the prediction of the size of tissue injury induced by transcatheter radiofrequency application, radiofrequency pulses (500 kHz) were delivered both in vitro and in vivo to isolated ventricular preparations and the intact canine heart, respectively. Radiofrequency coagulations were performed using unipolar electrode configuration. Besides measurements of current and voltage which were used to calculate the delivered power and tissue impedance, the catheter tip temperature was monitored during each application using specially designed 6F USCI catheters with a built-in nickel/chromium-nickel thermoelement. Lesion dimensions were measured and the correlation between lesion volume and delivered radiofrequency energy, maximum changes in catheter tip temperature and the integral of the temperature curve were calculated. First, in a pilot in vitro investigation, 50 radiofrequency coagulations (3.2 W-22.4 W, pulse duration 10 s) were performed in ventricular preparations from freshly excised dog hearts. The correlation between applied radiofrequency energy and lesion volume was 0.87; the correlation between maximal catheter tip temperature and lesion volume was 0.82; the correlation between temperature integral and lesion volume was 0.9. In the intact dog heart, 44 radiofrequency pulses were delivered to the left and right ventricular endocardium in 12 anaesthetized dogs (exposure time: 10 s). Delivered power ranged between 5.6 W and 24.6 W; tissue impedance varied between 92 omega and 364 omega; lesion volume measured 0-273 mm3; developed peak temperatures ranged from 16.25 degrees C to 196 degrees C. The calculated integral beneath temperature curves measured 126-1971 degrees C.s. The correlation between applied radiofrequency energy and lesion volume was 0.32; the correlation between maximal catheter tip temperature and lesion volume was 0.61. Temperature integral correlated best with the assessed volume of myocardial necrosis (r = 0.7). No significant arrhythmogenic or haemodynamic side-effects were observed. Macroscopic examination showed a central depression surrounded by a zone of homogeneous coagulation. Vaporization and crater formation up to a depth of 4 mm were observed following three radiofrequency discharges. In two of these cases, rapid changes and oscillation of catheter tip temperature were observed. Thus, monitoring of catheter tip temperature during radiofrequency energy application improves the prediction of lesion size. In addition, temperature monitoring might improve the safety of the procedure with respect to the risk of perforation.

Animals↗
PubMed1989

Catheter ablation of ventricular tachycardia using defibrillator pulses: electrophysiological findings and long-term results.

Catheter ablation of ventricular tachycardia (VT) was attempted in 24 patients (mean age 49 +/- 15.1 years) with a history of recurrent sustained VT resistant to previous antiarrhythmic drug therapy. 14 patients (58.3%) had also failed to respond to long-term administration of amiodarone alone and in combination with class I antiarrhythmic drugs. Endocardial catheter mapping during induced or spontaneous VT and/or pacemapping were performed to identify the site of origin of VT. Direct-current high-energy anodal shocks were delivered from a conventional cardioverter with stored energies of 100, 200 or 400 J via the distal electrode of conventional catheters. A total of 139 shocks was delivered during the ablation procedure. One patient died from wall perforation. Within 1 week of ablation, nine patients developed spontaneous recurrences of monomorphic sustained VT, identical to the clinical VT, and one patient developed a VT with a new morphology. In addition, four patients had a recurrence of their clinical VT after several weeks. In seven of 14 patients with spontaneous recurrences after the first ablation procedure and in three patients in whom VT was again inducible at the end of the first week, a second ablation procedure was performed. One patient with inducible VT after the first and second ablation sessions was given a third ablation procedure, and was discharged from hospital on anti-arrhythmic drugs which were successful despite being previously ineffective. After a mean follow-up period of 14.1 +/- 9.1 months, there were no spontaneous recurrences of sustained VT in 17 patients (71%) (nine without antiarrhythmic drugs and eight on antiarrhythmic drugs). In the remaining patients, incessant non-sustained VT (n = 2) or recurrent sustained VT (n = 2) occurred, and two patients died suddenly (at 2 and 21 months). There was no correlation between catheter mapping data or the results of pre-discharge electrophysiological study and clinical outcome during long-term follow-up. Complications related to catheter ablation included pulmonary oedema, cardiac tamponade, femoral artery occlusion, multiple episodes of ventricular tachycardia/fibrillation and thrombus formation, each in one patient (major complications; n = 7,29.1%), as well as transient third degree AV block, transient right or left bundle branch block, transient marked ST elevation or transient atrial tachycardia (minor complications; n = 8, 33.3%). The results suggest that catheter ablation might become an effective procedure for the non-pharmacological treatment of sustained VT.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

Coagulation of ventricular myocardium using radiofrequency alternating current: bio-physical aspects and experimental findings.

Within the last years, a variety of different energy sources has been investigated to test their feasibility for catheter ablation of myocardial tissue. This report summarizes our experience of the use of radiofrequency alternating current (500 kHz, unipolar mode) for coagulation of ventricular myocardium in canine experiments. Under standardized in vitro conditions, we found a significant correlation between actually delivered radiofrequency energy and assessed myocardial necrosis (r = 0.87). However, this did not hold for percutaneous application of radiofrequency alternating current to the beating dog heart (r = 0.32). In the intact dog heart, the size of induced lesions paralleled catheter contact pressure which was varied until ST-egment elevation was either 0-2 mV or 5-7 mV. However, no statistical significant differences in either calculated energy or tissue impedance were observed. Under in vivo conditions, a significant improvement in the predictability of the resulting size of lesions was observed when catheter tip temperature, measured via a built-in Ni/CrNi thermoelement, was monitored (r = 0.07). Changes in tip temperature during coagulation also indicated the quality of catheter contact, catheter damage and the appearance of carbonization at the tip of the ablation catheter. Total perforation of the myocardial wall and proarrhythmogenic effects were only rarely observed. In conclusion, catheter coagulation of myocardial tissue using radiofrequency energy can be considered as safe and effective. Since changes in catheter tip temperature occurring during coagulation were found to predict the extent of induced tissue necrosis, the development of temperature controlled radiofrequency devices seems promising and necessary.

Animals↗
PubMed1989

[Behavior of ventricular late potentials following catheter ablation of ventricular tachycardia].

In 10 patients non-invasively recorded signal-averaged electrocardiograms were obtained before and after direct-current ablation of ventricular tachycardia (right ventricular origin n = 5; left ventricular origin n = 5). The algorithms proposed by Simson and Karbenn et al. were used (modified Frank leads, high-pass filter cut-off frequency 25 Hz). No differences were observed between the mean values of the duration of the QRS-complex, the mean voltage during the last 40 ms of the QRS-complex, the duration of the late potentials and the number of patients having late potentials before and after ablation, respectively. The success of ablation could not be predicted by the signal-averaged ECG. There was no difference between the averaging parameters of those patients without recurrences of ventricular tachycardia during the follow-up period and those with (n = 3). Thus, the signal-averaged ECG did not prove helpful in predicting a successful outcome of direct-current catheter ablation of ventricular tachycardia.

Adult↗
PubMed1988

Reappraisal of criteria for assessing drug efficacy in patients with ventricular tachyarrhythmias: complete versus partial suppression of inducible arrhythmias.

To test whether increased difficulty in inducing ventricular tachycardia during antiarrhythmic therapy can be considered a sufficient criterion for predicting long-term efficacy of such therapy in patients with ventricular tachyarrhythmias, 95 patients were studied with a graded stimulation protocol (single and double premature stimuli during sinus rhythm and ventricular drives of 120, 140, 160 and 180 beats/min). After a control study, the effects of oral antiarrhythmic drugs on the ability to induce ventricular tachycardia were assessed. The median number of drug trials was four per patient. After antiarrhythmic therapy, four subgroups of patients were identified. In 36 patients, there was no change in inducibility (group 1), whereas in 18 patients ventricular tachycardia was rendered more difficult to induce; that is, a sustained ventricular tachycardia was inducible at a basic drive at least 40 beats/min faster than during the control study (group 2). In 34 patients, ventricular tachycardia induction was suppressed (group 3) and in 7 patients with nonsustained ventricular tachycardia, only 3 to 5 repetitive ventricular responses were induced after treatment (group 4). During follow-up of 15.5 +/- 11.5 months, 10 patients of group 1 had a recurrence of ventricular tachycardia and 6 died suddenly, whereas in group 2 only 1 patient died suddenly and in group 3, 2 patients had a recurrence of ventricular tachycardia (group 1 versus 2 and 3, p less than 0.001, Mantel-Cox and Breslow; group 2 versus 3, no difference). Thus, increased difficulty in inducing ventricular tachycardia is a sufficient criterion for predicting long-term efficacy of an antiarrhythmic drug regimen.

Adult↗
PubMed1988

Ultrastructural findings in endomyocardial biopsy of patients with Kearns-Sayre syndrome.

Kearns-Sayre syndrome is clinically defined by progressive external ophthalmoplegia, atypical retinitis pigmentosa and the potential occurrence of complete atrioventricular (AV) block. Right septal endomyocardial biopsy specimens from nine patients (four men and five women with a mean [+/- SD] [corrected] age of 36.3 +/- 14.4 years) with chronic progressive external ophthalmoplegia and mitochondrial skeletal myopathy were studied. Three patients had atypical retinal pigmentation. An atrioventricular or intraventricular conduction defect was observed in five patients. A pacemaker was prophylactically implanted in one patient because of abnormal conduction distal to the His bundle. Ultrastructural investigations revealed mitochondriosis in many heart muscle cells and an increased variability of mitochondrial form and size in all patients. In seven patients, 0.4 to 2.1% of all examined myocytes contained exclusively abnormal mitochondria. Three main types were observed: huge, mainly round mitochondria with concentric cristae; large, round or oval mitochondria with transverse or curved cristae; and small, vacuolated mitochondria. The volume density of myofibrils was reduced (41.9 +/- 11.1 compared with the normal value of 56.5 +/- 2.5 volume density [in percent], p less than 0.01) in these myocytes. Increasing numbers of vacuolated mitochondria correlated significantly with a reduction of myofibrils (r = -0.64, p less than 0.01). The data suggest that the ventricular myocardium of most patients with complete and even incomplete Kearns-Sayre syndrome is affected by disseminated mitochondrial cytopathy.

Adolescent↗
PubMed1988

Termination of re-entrant ventricular tachycardia by subthreshold stimulus applied to the zone of slow conduction.

A 52-year-old female patient developed recurrent sustained ventricular tachycardia during the first week after left ventricular aneurysmectomy. The patient had no history of ventricular tachycardia preoperatively. As her tachycardias proved to be resistant to several antiarrhythmic drugs, catheter ablation was considered. To define the site of origin of ventricular tachycardia, endocardial catheter mapping and pace-mapping were performed. In addition, the response to single premature stimuli applied during ventricular tachycardia was assessed. At a site in the basal portion of the antero-septal area of the left ventricle, early presystolic endocardial activity during ventricular tachycardia was found. Continuous pacing as well as premature stimulation from that site showed a marked delay between the stimulus artefacts and the induced QRS complexes. The stimulus-induced QRS complexes were identical to QRS complexes of spontaneous and induced ventricular tachycardia. At very short critical coupling intervals of single premature stimuli that did not capture the ventricles (non-propagated stimuli), ventricular tachycardia was reproducibly terminated. These findings are explained by assuming that the catheter was located within the zone of slow conduction of the re-entrant circuit, possibly in its proximal portion.

Atrioventricular Node↗
PubMed1988

Value of post-operative programmed ventricular stimulation after map-guided surgery for ventricular tachyarrhythmias--epicardial versus endocardial stimulation.

To assess the efficacy of map-guided antitachycardia surgery, induction of ventricular tachycardia has mostly been performed using endocardial stimulation. In addition, epicardial stimulation can be done using temporary epicardial wires, thus not requiring post-operative catheterization. However, the diagnostic value of epicardial versus endocardial stimulation for the post-operative evaluation of patients undergoing map-guided surgery for drug-refractory ventricular tachycardia is not known, especially with regard to the induction of non-clinical tachyarrhythmias. Therefore, we compared the results of epicardial and endocardial programmed ventricular stimulation in 58 consecutive patients in whom pairs of steel wires were placed over the right ventricle during surgery. The stimulation protocol consisted of single and/or double premature stimuli during sinus rhythm and paced ventricular drives of 500, 430, 370 and 330 ms. Pre-operatively, all patients had inducible monomorphic ventricular tachycardia by endocardial stimulation. Post-operatively, 36 patients were not inducible by either epicardial or endocardial programmed ventricular stimulation, whereas epicardial and endocardial stimulation induced the clinical ventricular tachycardia in six patients and non-clinical ventricular tachycardia in three patients (45/58 patients, 77% concordant). However, in two patients the clinical ventricular tachycardia was induced only by endocardial programmed ventricular stimulation. Non-clinical ventricular tachycardia was inducible in three patients by epicardial stimulation only, and in eight patients by endocardial stimulation only (13/58 patients, 23% discordant). Thus, in 77% of patients an identical result of programmed ventricular stimulation was obtained using epicardial and endocardial stimulation, whereas the results were discordant in 23%. Therefore, epicardial stimulation alone is not sufficient for the post-operative evaluation after map-guided surgery.

Adult↗
PubMed1988

Prognostic significance of ventricular late potentials in the postmyocardial infarction period.

Ventricular late potentials in patients after myocardial infarction can be assumed to herald an increased risk of future sudden cardiac death or symptomatic sustained ventricular tachycardia. This holds particularly true for patients studied early after recent myocardial infarction whereas patients assessed later in the subsequent course have a substantially lesser incidence of arrhythmic events, probably due to intercurrent death of those at high risk. Of prognostic importance appears not only the presence but also the duration of late potentials. A meaningful role is also assumed by the extent of left ventricular functional impairment (EF less than 40%). However, in consideration of the complex mechanisms that can lead to sudden cardiac death, no single method predicts with high sensitivity the occurrence of a ventricular tachyarrhythmic event. Sudden cardiac death can be incurred on the basis of chronic electrophysiological abnormalities as a consequence of regional slow conduction in the border zone of a previous myocardial infarction precipitated by trigger factors such as spontaneous ventricular arrhythmias. Sudden cardiac death or symptomatic sustained ventricular tachycardia can also occur due to sudden and transient changes in the electrophysiological properties of the myocardium due to ischemia. Whether the combination of late potentials with clinical parameters such as ventricular arrhythmias detected in the ambulatory ECG and those induced with programmed electrical stimulation will lead to more accurate identification of patients at risk prerequisites further elucidation. Currently available literature indicates that in patients with late potentials, ventricular tachycardias can be induced more frequently by programmed electrical stimulation and that the combination of both phenomena confers a particularly high risk.

Atrioventricular Node↗
PubMed1988

Effects of non-pharmacological interventions on ventricular late potentials.

The purpose of the paper is to review the presently available information of the effects of non-pharmacological interventions for the control of drug-refractory ventricular tachyarrhythmias on non-invasively recorded ventricular late potentials. During recent years, non-pharmacological interventions have evolved as an alternative form of treatment to control drug-refractory ventricular tachyarrhythmias. The effects of these non-pharmacological measures on ventricular late potentials are poorly understood. Successful surgical control of ventricular tachycardia often normalizes the signal averaged ECG and may eliminate delayed potentials. Thus, this non-invasive test may be useful in assessing surgical efficacy in subgroups of patients with ventricular tachycardia. However, the clinical value of late potentials in assessing surgical efficacy in the individual case may be limited as the sensitivity and specificity of the loss of late potentials after antitachycardia surgery are low. In addition, the effects of transvenous catheter ablation on ventricular late potentials will be reviewed. The available information suggests that this intervention has little effects on the presence or absence of late potentials. Thus, non-invasive recording of late potentials seems not to be helpful in predicting the acute and long-term efficacy of catheter ablation. In conclusion, changing of the parameters in the signal-averaged QRS complex after antitachycardia surgery may be useful in predicting the efficacy of surgical interventions for drug-refractory ventricular tachycardias in subgroups of patients. However, the sensitivity and predictive accuracy of this test are low, thus limiting its clinical usefulness.

Cardiac Pacing, Artificial↗
PubMed1988

[Observations of the clinical characteristics of patients with ventricular tachyarrhythmias--l978 to l985].

To get some insight into the clinical profile of patients with ventricular tachyarrhythmias and to elucidate potential time-dependent changes, data from 421 patients with documented tachyarrhythmias referred for electrophysiologic studies, were analyzed. The observation period is extended from 1978 to 1986. Patient's data were analyzed in 2-year subperiods. There were no major changes with regard to underlying heart disease, or within the interval between myocardial infarction and electrophysiologic study, or with regard to the indication for electrophysiologic study and the results of right ventricular stimulation during the analyzed subperiods. The interval between the first episode of documented tachyarrhythmia and the study, as well as the number of previous episodes of documented arrhythmias, decreased significantly between the first observation period (1978/79) and all the following periods. Before 1982, about 2% of patients were on amiodarone therapy at the time of referral, whereas from 1982 a higher proportion of cases was referred on amiodarone (21%, 12%, resp.). Over the whole observation period, an increasing number of patients finally underwent antitachycardia surgery.

Cardiac Pacing, Artificial↗
PubMed1988

[The effect of alcohol on the heart in chronic alcoholics].

48 asymptomatic alcoholics (mean age 31.2 years) with an average daily alcohol consumption of 287 g were studied about 45 h (mean) after the last ingestion of alcohol. M-mode echocardiography and 24-h long-term ECG recordings were performed. 24 of these patients were restudied after a mean of 12 days of abstinence using long-term ECG recording. All patients were in sinus rhythm. 44 of 48 patients demonstrated supraventricular premature beats. In three patients, there were ventricular pairs (1/24 h). Two further patients had ventricular triplets (1/24 h). Echocardiography demonstrated a significant enlargement of left atrial dimensions (LA: 39 +/- 3.8 mm), of the diameter of the left ventricular posterior wall (10 +/- 4.1 mm), and of the interventricular septum (12 +/- 1.7 mm) compared to control data in 24 'normals'. In addition, there was a significant increase in the derived left ventricular mass index (292 +/- 48.2 g). Left ventricular enddiastolic diameter was not significantly different. Laboratory tests showed pathologically elevated values of SGOT, SGPT, and gamma-GT whereas serum potassium was normal. During restudy of the long-term ECG after 12 days, complex ventricular arrhythmias were no longer detectable. In six patients, echocardiography was repeated after a mean of 110 days of abstinence. Three of these patients had had marginal left ventricular fractional shortening during the first study which was normalized at the repeat study. Our results show some degree of left ventricular dysfunction in some chronic alcoholics without clinical overt heart failure.

Adult↗
PubMed1988

Bidirectional transvenous/subcutaneous defibrillation of ventricular fibrillation in dogs: success rates, energy requirements, currents, voltages and impedance.

Four hundred and thirteen defibrillations of alternating current-induced ventricular fibrillation were performed in 10 halothane-anaesthetized dogs (body weight: 24.5-30.5 kg). Success rates, energy demands, currents, peak voltages and impedance were determined. A transvenous catheter electrode system (Medtronic 6880, right ventricular apex and superior vena cava, distance 100 or 150 mm) and subcutaneous patch electrodes (Intec 67 L, 2nd/3rd and/or 3rd/4th left intercostal space) were used for bidirectional defibrillation. Loading voltages ranged from 600 to 850 V. With an electrode distance of 100 mm and a pulse duration of 2 ms separated by 1 ms, success rates were 100%, 40% and 0% for 850.650 and 600 V, respectively. With a 3-ms pulse duration, the corresponding rates were 100%, 60% and 50%. With a 2-ms pulse duration, successful defibrillation was achieved with energies lower than 15 J in 27%, with energies between 15 and 20 J in 77%, and 100% with energies higher than 20 J. Defibrillation currents were 4.4-9.3 A for pulse 1 (superior vena cava/ventricular apex) and 6.3-13.4 A for pulse 2 (patch/ventricular apex), respectively. Effective peak voltages ranged from 510 to 787 V and from 514 to 777V and averaged 89.6% of the loading voltages. Impedance values (peak voltage/current) were 75.5-117.7 (pulse 1) and 51.7-94.9 Ohms (pulse 2). Fifty consecutive defibrillations in one animal resulted in a decrease of impedance (114.6 to 84.9 Ohms, pulse 1:75.4 to 53.0 Ohms, pulse 2). Defibrillation of ventricular fibrillation can be achieved with acceptably low energies using a bidirectional transvenous/subcutaneous system, avoiding thoracotomy and general anaesthesia for implantation of the defibrillation system.

Animals↗
PubMed1987

Influence of the cycle length of basic drive on induction of sustained ventricular tachycardia associated with coronary artery disease.

The relation between the cycle length of basic drive during programmed ventricular stimulation and the coupling intervals at which sustained monomorphic ventricular tachycardia (VT) was initiated was analyzed in patients with coronary artery disease and documented sustained VT. The study included 28 patients in whom hemodynamically tolerable, monomorphic sustained VT was inducible at different cycle lengths of basic drive during the same electrophysiologic study. The stimulation protocol included single or double premature stimuli during paced ventricular rhythms at different cycle lengths of basic drive. The coupling intervals of premature stimuli for induction of VT (considered the outer margin of the echo zone) during step 1 of the stimulation protocol (basic drive at cycle lengths of 500 or 430 ms) were compared with those during step 2 (basic drive at cycle lengths of 370 or 330 ms). The mean cycle length of induced sustained VT was 370 +/- 79 ms. The mode of induction of VT remained the same in 23 patients (single or double premature stimuli); in 5 patients, fewer premature stimuli were required during step 2 than step 1. By moving from step 1 to step 2, VT could be induced at longer coupling intervals of the premature stimuli in 23 patients (82.1%). The mean increase in the sum of the coupling intervals was 52 +/- 37 ms. In 5 patients, the coupling intervals either did not change from step 1 to step 2 (n = 1) or decreased by an average of -40 +/- 14.1 ms. The results suggest that inducibility of VT is favored by a decrease in the cycle length of basic drive.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

High frequency alternating current ablation of an accessory pathway in humans.

High frequency alternating current ablation of an accessory pathway was performed in a patient with incessant circus movement tachycardia using a right-sided, free wall accessory pathway. Antiarrhythmic drugs, antitachycardia pacing and transvenous catheter ablation using high energy direct current shocks could not control the supraventricular tachycardia. A 7F bipolar electrode catheter with an interelectrode distance of 1.2 cm was positioned at the site of earliest retrograde activation during circus movement tachycardia. At this area, two alternating current high frequency impulses were delivered with an energy output of 50 W through the distal tip of the bipolar catheter, while the patient was awake. After the first shock supraventricular tachycardia terminated and accessory pathway conduction was absent without altering anterograde conduction in the normal atrioventricular (AV) conduction system. No reports of pain or other complications were noted. In short-term follow-up of 5 months, the patient had been free of arrhythmias without antiarrhythmic medication. Thus, high frequency alternating current ablation was performed for the first time in the treatment of an arrhythmia incorporating an accessory pathway in a human. This technique may be an attractive alternative to the available transcatheter ablation techniques and to antitachycardia surgery.

Adult↗
PubMed1987

Effects of pharmacological and non-pharmacological interventions on ventricular late potentials.

The purpose of this paper is to review the presently available information on the effect of antiarrhythmic drugs and of map-guided antitachycardia surgery on ventricular late potentials. Studies in experimental myocardial infarction have shown that antiarrhythmic drugs are able to prolong regional low-amplitude fractionated electrical activity. However, no correlation between changes in duration of low-amplitude electrical activity and antiarrhythmic drug efficacy could be demonstrated. A similar lack of correlation between changes in duration of late potentials as recorded by the signal averaging technique from the body surface and inducibility or suppression of ventricular tachycardia were observed. Neither changes in duration or amplitude nor in the frequency content of ventricular late potentials showed an unequivocal correlation with drug efficacy. By contrast, there is convincing evidence that exclusion of arrhythmogenic tissue by map-guided antitachycardia surgery correlates with the loss of late potentials postoperatively in a high percentage of cases. If, however, late potentials persist after surgery, there is a high chance of ventricular tachycardia being still inducible postoperatively. A loss of ventricular late potentials by surgery may be the result of isolation of the arrhythmogenic tissue, devitalization and/or removal. In conclusion, there is presently no convincing evidence that any of the parameters for characterization of ventricular late potentials is clinically useful to predict the efficacy of antiarrhythmic drug therapy. On the other hand, ventricular late potentials have proved useful for prediction of the success of map-guided antitachycardia surgery.

Anti-Arrhythmia Agents↗