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Biomedical subjects

W Haverkamp

Publications and source records attributed to W Haverkamp.

At least 109 records · Page 6Linked to original sources
PubMed1994

Dispersion of ventricular refractoriness in experimental myocardial infarction: effect of sotalol.

UNLABELLED: Dispersion of refractoriness may contribute to the propensity for reentrant arrhythmias. This study was performed to assess the effect of sotalol on the dispersion of refractoriness in experimental myocardial infarction. In 9 mongrel dogs, 14 days after induction of myocardial infarction by an occlusion reperfusion technique, programmed ventricular stimulation and epicardial mapping were performed before and during (3 mg/kg + 0.5 mg/kg per hour) sotalol administration. To assess the spatial distribution of refractoriness, ventricular fibrillation (VF) intervals were analyzed. The rationale for this method is that, during VF, when multiple reentrant wavelets are present, cells are excited as soon as they recover from previous activation. The coefficient of variation (standard deviation x 100) served as an index of spatial distribution of refractoriness. RESULTS: VF was induced before sotalol in 7 dogs and in 5 of 7 during sotalol administration. The mean value of the index VF intervals decreased from 19.8 +/- 2.3 at baseline to 15.8 +/- 2.6 during sotalol (P = 0.011), indicating a more homogeneous distribution of refractoriness. Thus, the antiarrhythmic effects of sotalol may be mediated by its action on the dispersion of refractoriness.

Animals↗
PubMed1994

Recurrence and late block of accessory pathway conduction following radiofrequency catheter ablation.

INTRODUCTION: Many issues regarding the recurrence of accessory pathway conduction and the long-term outcome of late block of accessory pathway conduction are still unknown or controversial. METHODS AND RESULTS: Data from 217 patients who underwent an initially successful radiofrequency ablation of accessory pathways and 7 patients with late block of accessory pathway conduction following an initially unsuccessful ablation were analyzed. During a mean follow-up of 19 +/- 11 months, accessory pathway conduction resumed in 21 (10%) of 217 patients following an initially successful ablation and in 6 (86%) of 7 patients with late block of accessory pathway conduction (P < 0.01). After initially successful ablations, the recurrence rates of accessory pathway conduction at 1, 3, and 6 months were 5.9%, 7.4%, and 11.3%, respectively. A late electrophysiologic study at 6 months uncovered recurrence in only 1 of 124 asymptomatic patients, but failed to detect the late recurrence in 2 patients in whom the accessory pathway conduction resumed after more than 6 months. Multivariate analysis revealed that independent predictors for recurrence of accessory pathway conduction were concealed accessory pathway, presence of transient effect of radiofrequency pulse, and more than 5 pulses required for initial cure. Accessory pathway location, length of the tip electrode of the ablation catheter, and repeat radiofrequency pulses ("safety pulses") after effective pulses did not predict resumption of accessory pathway conduction. CONCLUSIONS: After initially successful ablation, the recurrence rates of accessory pathway conduction at 1, 3, and 6 months were 5.9%, 7.4%, and 11.3%, respectively. Late electrophysiologic testing had little prognostic value in asymptomatic patients following successful ablation. Application of "safety pulses" did not prevent recurrence. Late block of accessory pathway conduction did not predict long-term efficacy.

Adolescent↗
PubMed1994

[High frequency catheter ablation of left-sided manifest accessory conduction pathways during sinus rhythm and in continuous atrial fibrillation].

Atrial fibrillation is frequently initiated during radiofrequency catheter ablation of accessory pathways. It has been generally believed that initiation of atrial fibrillation may complicate the localization of accessory pathway. Therefore, most centers currently perform cardioversion in order to continue the ablation session. The purpose of the present study was to assess the feasibility and the electrophysiologic criteria for successful radiofrequency catheter ablation of left sided accessory pathways during atrial fibrillation in patients with WPW-syndrome. Radiofrequency ablation was performed in 87 patients with left-sided manifest accessory pathways during atrial fibrillation (n = 16) or during sinus rhythm (n = 71). The criteria for localization of accessory pathways were recording of stable accessory pathway potentials, local ventricular activation preceding the onset of the intrinsic flection of the unipolar electrogram and a QS pattern of the unipolar electrogram. Overall, the accessory pathways were successfully interrupted in 85/87 patients (98%). During the first ablation procedure, abolishing of accessory pathways was achieved in 15 of 16 patients (94%) during atrial fibrillation compared to 64 of 71 patients (90%) during sinus rhythm (n.s.). The total procedure time and fluoro time was significantly shorter during atrial fibrillation than during sinus rhythm (161 +/- 91 min vs. 216 +/- 128 min, p < 0.05, and 31 +/- 24 vs. 41 +/- 26 min. p < 0.05, respectively). Thus, it is feasible and very effective to perform radiofrequency ablation of left-sided manifest accessory pathways during atrial fibrillation. Precise localization of accessory pathway during atrial fibrillation seems even easier than during sinus rhythm as indicated by shorter procedure and fluoro times in the atrial fibrillation group.

Adolescent↗
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↗
PubMed1994

[The pro-arrhythmic effects of anti-arrhythmia agents].

Proarrhythmia is defined as the provocation of new cardiac arrhythmias or the aggravation of preexisting arrhythmias by antiarrhythmic drugs. The possible types of manifestation of proarrhythmia are manifold. With respect to prognosis, drug-induced ventricular tachyarrhythmias seem to be of particular importance. Monomorphic ventricular tachycardia and ventricular tachycardias of the torsade de pointes type have to be distinguished. The former seem to be mainly based on reentrant mechanisms, while the later is supposed to result from triggered activity. Drug-induced monomorphic tachycardia is most often observed during therapy with drugs which slow conduction (class I agents, proarrhythmic potency: IC > IA > IB). Patients with depressed left ventricular function and previously documented life-threatening tachyarrhythmias are the most susceptible candidates. Torsade de pointes can be preferentially observed during therapy with antiarrhythmic drugs which prolong myocardial repolarization (i.e. class IA and class III agents). Electrolyte abnormalities and/or bradycardia are factors which often predispose to the development of this particular type of proarrhythmia. The physician who prescribes antiarrhythmic drugs must be aware of the different types and clinical manifestations of proarrhythmia. This is necessary to assess the degree of proarrhythmic risk and to determine the benefit/risk ratio before the start of drug therapy.

Anti-Arrhythmia Agents↗
PubMed1994

[Drug prevention of recurrence in paroxysmal and chronic atrial fibrillation].

In many patients with paroxysmal or chronic atrial fibrillation, long-term antiarrhythmic drug therapy is performed to prevent recurrences of atrial fibrillation or to reduce the incidence of paroxysmal attacks of atrial fibrillation. The results of several studies on the efficacy of antiarrhythmic drugs in patients with paroxysmal atrial fibrillation have revealed that the incidence of recurrent attacks of atrial fibrillation can be reduced and the duration of arrhythmia free intervals can be prolonged by antiarrhythmic drug therapy. However, complete prevention of atrial fibrillation can be achieved only in a minority of patients. At present, there is no evidence that antiarrhythmic drug treatment of patients with paroxysmal atrial fibrillation might worsen the prognosis by an increase in cardiac mortality induced by antiarrhythmic drugs. In patients with chronic atrial fibrillation, the recurrence rate of the arrhythmia can be significantly reduced by antiarrhythmic drug therapy within the first year of treatment. However, there is evidence that antiarrhythmic drugs might worsen the prognosis when compared to patients with atrial fibrillation not treated with antiarrhythmic drugs. Accordingly, the indication for antiarrhythmic drug therapy to prevent recurrences in patients with chronic atrial fibrillation has to be made restrictively and should be largely based on the symptomatic status of the patients. Antiarrhythmic drug therapy seems to be indicated only in patients who are significantly symptomatic or compromised by the arrhythmia. In patients without or with only mild symptoms, medical therapy with the aim to slow the ventricular response with digitalis, calcium antagonists or betablocking agents seems to be more adequate. Currently, with respect to efficacy and safety, there is no antiarrhythmic drug that has been proved to be superior to others and that can thus be recommended as the drug of first choice for patients with paroxysmal or chronic atrial fibrillation to prevent recurrences. The choice of the optimal antiarrhythmic drug should be made by taking individual factors (e.g., etiology of the arrhythmia, patient compliance, liver and renal function of the patient, additional medical therapy) into account. Major problems during long-term antiarrhythmic drug therapy may arise in patients with pre-existing sinus node dysfunction or conduction disturbances of the atrioventricular node. In addition, the conversion of atrial fibrillation with relatively slow ventricular rates to the atrial flutter with fast ventricular rates that is occasionally observed during treatment with class I-antiarrhythmic drugs may complicate long-term therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Anti-Arrhythmia Agents↗
PubMed1994

[Therapy of AV nodal reentry tachycardia with catheter ablation of the fast retrograde pathway].

AV-nodal reentrant tachycardia (AVNRT) is a common cause of recurrent supraventricular tachycardia. Currently, catheter ablation of either slow or fast pathway are nonpharmacologic options for the treatment of patients with AVNRT. Radiofrequency (RF) catheter ablation of the fast pathway was attempted in 35 patients (aged 46.7 +/- 15 years; 12 m, 23 f) with recurrent AVNRT. RF energy (25-50 watt, 30-90 s) was delivered to the anterior right atrial septum. The catheter was placed posterior to the largest His bundle deflection. AV conduction was monitored during continuous pacing of the high right atrium while the RF current was applied. RF-ablation was acutely successful using a mean of 6.5 +/- 6.2 impulses in 31 patients. Late spontaneous block of the slow pathway occurred in one patient (pat. 17) with an unsuccessful initial attempt of fast pathway ablation. PQ and AH interval increased significantly after the ablation procedure (PQ: from 149 +/- 27 to 208 +/- 34 ms, AH: from 76 +/- 22 to 131 +/- 38 ms; p value: < 0.0001). Acute interruption of retrograde VA conduction was the result in 23 patients. Six patients (17%) had a recurrence of AVNRT during a follow-up period of 11.9 +/- 7.5 months. Five of 6 patients underwent a second successful procedure. Complete AV block occurred in 3 of the first 10 consecutive patients and in none of the subsequent 25 patients (overall incidence: 8.6%). Thus, RF ablation of the fast retrograde pathway is an effective method for the curative treatment of AVNRT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Atrioventricular nodal reentry tachycardia: electrophysiologic comparisons in patients with and without 2:1 infra-His block.

Patients with atrioventricular nodal reentry tachycardia (AVNRT) occasionally may demonstrate a 2:1 infra-His block during tachycardia. However, the electrophysiologic background of this phenomenon has not been established so far. In the present study we compared the electrophysiologic parameters of 10 consecutive patients with a transient 2:1 infra-His block during AVNRT of the common type (Group A) with those of 17 consecutive patients without this phenomenon during tachycardia (Group B). Transient 2:1 infra-His block occurred without termination of the tachycardia in all 10 patients of Group A. The tachycardia sustained despite intermittent or permanent conduction disturbance of the infrahisian tissue in 8 of these 10 patients. In comparison, the electrophysiologic parameters of 17 patients without 2:1 block during AVNRT of the common type (Group B) were analyzed. A significantly longer antegrade (318 +/- 58 ms vs. 259 +/- 50 ms) and retrograde (308 +/- 59 ms vs. 239 +/- 20 ms) AV conduction capacity could be demonstrated in these patients. The tachycardia cycle length did not differ significantly between the two groups, although the mean tachycardia cycle length was 48 ms longer in patients of Group B. These observations demonstrate an advanced conduction capacity in patients with a transient infra-His block during AVRNT of the common type. This study underlines that the reentry circuit in AVNRT is not necessarily dependent on infrahisian tissue.

Adult↗
PubMed1993

Radiofrequency catheter ablation of ventricular tachycardia following implantation of an automatic cardioverter defibrillator.

OBJECTIVES: The present study reports on the complementary role of two nonpharmacological options of antiarrhythmic therapy. BACKGROUND: Catheter ablation, antitachycardia surgery, and the implantable cardioverter defibrillator (ICD) have become important tools in the management of ventricular tachyarrhythmias. However, the emergence of ventricular tachyarrhythmias after implantation of an ICD is possible because the arrhythmogenic substrate is not affected. PATIENTS AND METHODS: Six of 180 patients developed frequent episodes of monomorphic ventricular tachycardia (n = 2) or incessant ventricular tachycardia (n = 4) following implantation of an ICD and underwent radiofrequency (RF) catheter ablation. Catheter ablation was performed using a RF generator HAT 200. Energy was delivered between a 4-mm tip electrode of the ablation catheter and a patch electrode. RESULTS: Catheter ablation was done 6.8 +/- 5 months following ICD implantation; 6 +/- 2.2 RF impulses were delivered at the site of origin of ventricular tachycardia characterized by early endocardial activation during ventricular tachycardia, identical pace mapping and long latency between stimulus, and QRS-complex in five patients. New bundle branch reentry was the underlying mechanism of ventricular tachycardia in one patient. RF catheter ablation resulted in termination of incessant ventricular tachycardia. Immediately postablation, the documented ventricular tachycardia was rendered noninducible in all patients. No ICD malfunctions have been observed. One patient died due to heart failure 24 hours after successful ablation of the incessant ventricular tachycardia. During a follow-up of 5-19 months, episodes of ventricular tachycardia recurred in four patients. All episodes could be controlled by the ICD without frequent cardioversions. CONCLUSION: RF catheter ablation is a complementary therapeutic option in case of frequent or incessant ventricular tachycardia after ICD implantation.

Adult↗
PubMed1993

Unexpected emergence of manifest preexcitation following transcatheter ablation of concealed accessory pathways.

INTRODUCTION: The basis for anterograde or retrograde unidirectional block of accessory pathways still remains a controversial issue. METHODS AND RESULTS: Four of 19 consecutive patients (1 male, 3 female; ages 27 to 34 years) who underwent transcatheter ablation of concealed accessory pathways developed manifest preexcitation after the ablation. The location of the concealed accessory pathways in these four patients were right lateral, left posteroseptal, left posterolateral, and left lateral. Radiofrequency current was used in three of the four patients and high energy direct current in one patient. After ablation, manifest preexcitation was observed in these four patients for the first time. Manifest preexcitation developed immediately after ablation in two of the four patients and after 4 and 14 days in the other two. Detailed endocardial mapping revealed that the manifest preexcitation originated from the same location as the concealed pathways. Subsequently, catheter ablation was successfully performed in three of the four patients using radiofrequency current. One patient underwent successful surgical ablation. No recurrence of preexcitation was observed during a follow-up period of 9 to 38 months. All patients remained free of arrhythmias. CONCLUSION: The basis for this unexpected emergence of preexcitation in these patients with only retrograde conducting accessory pathways deserves further investigation. Although not compared in the present study, this phenomenon has not been reported in patients who underwent surgical interruption of accessory pathways. We postulate that a lesion at the site of insertion of the accessory pathway had modified the anterograde conduction capacity.

Adult↗
PubMed1993

[Torsade de pointes].

Torsade de pointes (TDP) is a polymorphic ventricular tachycardia with a particular electrocardiographic pattern of continuously changing ("twisting") morphology of the QRS complex occurring in the setting of delayed myocardial repolarization (i.e., prolongation of the QT interval). TDP may develop in the setting of an idiopathic disorder (Jervell/Lange-Nielsen syndrome, Romano-Ward syndrome, sporadic long QT syndrome) or may be induced by pharmacologic agents which prolong the QT interval, as well as by other clinical circumstances under which repolarization is delayed (e.g., hypokalemia, hypomagnesemia, bradycardia) (acquired long QT syndrome). Since the treatment of TDP strongly differs from that of conventional ventricular tachycardia, correct diagnosis is critical as it guides the treating physician in selecting the appropriate mode of therapy. In this paper mainly the electrocardiographic criteria presently used for the correct identification of this unusual form of ventricular arrhythmia are presented. Additionally, the potential mechanisms and therapeutic modalities of TDP are discussed.

Anti-Arrhythmia Agents↗
PubMed1993

[Oral anticoagulation for prevention of thromboembolism in non-rheumatic atrial fibrillation: indications, effectiveness and risk].

Oral anticoagulation in patients with rheumatic heart disease for prevention of systemic thromboembolism is accepted clinical practice. The incidence of stroke in patients with nonrheumatic atrial fibrillation is about five times the rate of patients in sinus rhythm. However, contradictory findings in several small retrospective studies have precluded determination of a gold standard for patients with nonrheumatic atrial fibrillation so far. Recently, the results of five prospective, placebo-controlled studies in patients with nonrheumatic atrial fibrillation treated with anticoagulation have been published. A consistent risk reduction of thromboembolism ranging from 37 to 87% in patients treated with warfarin was reported. This risk reduction occurred in excess of a relatively low incidence of intracerebral and/or fatal bleeding complications. The efficacy of prevention of thromboembolism was comparable for high intensity anticoagulation (International Normalized Ratio (INR) 2.8-4.2) and low dose anticoagulation (INR 1.5-2.7). However, fatal and/or intracerebral bleedings only occurred with INR > or = 2.6. In subgroup analysis, recent congestive heart failure, arterial hypertension, and previous apoplex or arterial thromboembolism were independent clinical predictors of increased risk for thromboembolism, whereas results in patients with chronic and intermittent atrial fibrillation were comparable. In 69 patients with lone atrial fibrillation, no single event occurred in the follow-up period. Thus, lone atrial fibrillation does not seem to carry an increased risk for stroke when strict criteria for diagnosis of lone atrial fibrillation are applied. In two of the five studies, aspirin was additionally randomized. Since contradictory findings resulted, the role of aspirin for prophylaxis of stroke still needs to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

[Anisotropic impulse conduction characteristics in chronic myocardial infarct. The importance for initiation and perpetuation of ventricular tachycardia].

The underlying mechanism of most ventricular tachycardias in the setting of chronic myocardial infarction is reentrant excitation. At that time, the active membrane properties like upstroke velocity and amplitude of action potentials of muscle fibers surviving in the border zone of the infarction have returned nearly completely to normal. Anisotropic conduction characteristics, however, importantly contribute to the electrophysiologic properties of the epicardial and/or endocardial border zones in chronic myocardial infarction. In normal myocardial tissue with tight coupling between muscle fibers, conduction velocity is slower for impulses propagating transverse to fiber orientation compared to longitudinal to fiber orientation due to a higher effective axial resistivity ("uniform" anisotropy). With infarct healing, connective tissue invading into the epicardial border zone separates surviving muscle fiber bundles and thereby decreases cell-to-cell coupling ("non-uniform" anisotropy). In this setting, excitation waves propagate transverse to fiber orientation in an irregular sequence and conduction velocity in this direction is significantly reduced without occurrence of acute ischemia. Block of conduction waves propagating longitudinally to fiber orientation may lead to activation of the area distal to the block with long delay by very slow transverse wavefronts. This long delay allows fibers proximal to the line of block to regenerate excitability, and reentrant excitation may be initiated. The common pathway of figure-eight tachycardias preferentially orientates longitudinally to fiber orientation. Very slow conduction transverse to fiber orientation at the pivoting points of reentrant circuits may lead to the occurrence of excitable gaps.

Animals↗
PubMed1993

[Diagnostic and therapeutic problems in idiopathic prolonged QT syndrome. A case report].

The case of a 36-year-old woman with suspected idiopathic long QT syndrome is reported. Diagnosis was made late after syncopal attacks and several episodes of resuscitation had occurred. Although therapy with a beta-blocking agent was initiated and a cardioverter/defibrillator was implanted, the patient died, due to a hydrocephalus internus resulting in cerebral damage. Diagnostic and therapeutic problems in idiopathic long QT syndrome are discussed.

Adult↗
PubMed1992

Characteristics of local electrogram predicting successful transcatheter radiofrequency ablation of left-sided accessory pathways.

OBJECTIVES: The purpose of this study was to analyze and compare the local electrograms recorded at successful and unsuccessful sites of ablation to identify the criteria that may predict successful sites and minimize unnecessary radiofrequency delivery. BACKGROUND: Transcatheter ablation of accessory pathways using radiofrequency energy requires extremely precise localization of an accessory pathway. METHODS: Local electrograms from 50 consecutive patients with left-sided accessory pathways who underwent transcatheter radiofrequency ablation were analyzed. During catheter ablation, localization of accessory pathways was performed in 39 pathways during pre-excited sinus rhythm and in 14 pathways during orthodromic tachycardia. A total of 429 local electrograms at target sites obtained before delivery of radiofrequency current was analyzed. A prospective study was performed in another 20 patients using the criteria derived from the retrospective study. RESULTS: Accessory pathway conduction block was achieved in 36 (92%) of 39 pathways in which mapping was performed during pre-excited sinus rhythm and in 9 (64%) of 14 pathways in which mapping was performed during orthodromic tachycardia (p less than 0.05). When mapping was performed during pre-excited sinus rhythm, a combination of four variables (that is, an accessory pathway potential, stability of local electrograms, atrial activation greater than 1 mV and ventricular activation preceding the onset of the delta wave) showed a 62% probability of success. In contrast, excluding these variables resulted in a 95% probability of failure (noneffective or transiently effective). The prospective study shows that the use of these criteria can significantly reduce the number of current applications. When mapping was performed during orthodromic tachycardia, recording the earliest atrial activation was the most powerful predictor of success. A stable local electrogram with a small notch on the ventricular potential, presumed to be an accessory pathway potential, may add predictive value. CONCLUSIONS: Transcatheter radiofrequency ablation is highly effective in the treatment of patients with left-sided accessory pathways. Specific characteristics of local electrograms can be important predictors of success or failure. Mapping during pre-excited rhythm renders ablation more effective than does mapping during orthodromic tachycardia.

Adolescent↗
PubMed1992

Nd:YAG laser-photocoagulation: acute electrophysiological, hemodynamic, and morphological effects in large irradiated areas.

Laser-photocoagulation (LPC) of arrhythmogenic myocardium has been reported to successfully ablate ventricular tachycardia. The purpose of this study was to investigate the acute hemodynamic and electrophysiological effect of continuous laser energy (Nd:YAG, 1060 nm) applied via a 0.4-mm quartz fiberoptic on the epicardial surface of the heart in nine dogs. A total of 51 +/- 2.3 pulses was delivered in each animal to induce homogeneous tissue necrosis. Applied energy was 12.3 +/- 2.7 J/mm2, irradiated surface measured 12.6 +/- 3.0 cm2, lesion depth was 6.3 +/- 1.2 mm (range: 5.0-8.1 mm), lesion volume was 8.1 +/- 2.8 cm3 (6.8% of left ventricular [LV] mass). After LPC, epicardial stimulation threshold significantly rose from 1.0 +/- 0.3 to 10.2 +/- 4.9 mA in the border zone to nontreated tissue and from 0.9 +/- 0.4 to 32 +/- 15.7 mA in the center of the lesions. Loss of epicardial activation in the irradiated areas could be demonstrated by epicardial mapping. Ventricular extrasystoles during LPC were seen in all dogs, ventricular tachycardia in seven, and ventricular fibrillation in two dogs. After LPC, cardiac output and LV dP/dtmax significantly decreased by 14.2% and 11.2%. LPC induced predictable homogeneous tissue edema, eosinophilic staining, contraction band necrosis, and sharp demarcated hemorrhagic border zones with a sharp electrical border zone to nontreated tissue and loss of epicardial activation. During LPC, various arrhythmogenic effects could be observed. However, no persistent arrhythmic activity developed after LPC. The results confirm the feasibility of epicardial LPC of the myocardium. Although not rested in this study, LPC of arrhythmogenic tissue may also be feasible as a treatment modality of ventricular tachycardia.

Animals↗
PubMed1992

Radiofrequency ablation of accessory pathways: characteristics of transiently and permanently effective pulses.

The purpose of this study was to characterize and compare the radiofrequency current applications that produced permanent or transient accessory pathway conduction block. One hundred fifty-two radiofrequency energy applications that induced permanent (permanently effective pulses, n = 48) or transient (transiently effective pulses, n = 104) accessory pathway block in 57 patients with 60 accessory pathways were analyzed. The time from the onset of current application to disappearance of preexcitation or termination of supraventricular tachycardia by permanently effective pulses was 1-15 seconds (mean 3.6 +/- 3.8 sec) compared to 2-29 seconds (mean 11.5 +/- 7.5 sec) by transiently effective pulses (P less than 0.01). After transiently effective pulses that induced block in accessory pathway, conduction resumed within 5 minutes while induced block by permanently effective pulses persisted in 44 of 48 patients (92%) during follow-up of 11 +/- 12 months. The accessory pathway conduction returned in the remaining four patients after ablation 2 weeks to 7 months. After transiently effective pulses, 41 impulses were delivered to the same site using a higher power output (n = 32) and/or longer energy delivery duration (n = 20) without new mapping of accessory pathway location. Thirty-six of these impulses again resulted in transient accessory pathway block, four had no effect, only one impulse induced a permanent block in the accessory pathway. Pulses with higher power outputs tended to induce transient effects more frequently than pulses with lower energy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗