Efficacy of antitachycardia pacing confirmed by stored electrograms. A retrospective analysis of 613 stored electrograms in implantable defibrillators.

The implantable defibrillator (ICD) is an established therapy in the prevention of sudden cardiac death by defibrillation of ventricular fibrillation. Another specific feature of the ICDs is antitachycardia pacing (ATP) of ventricular tachycardia. Several studies report success rates of ATP in 83 to 98% of cases. In clinical practice the success of terminating ventricular tachycardia is estimated only by automatic device analysis. Therefore the objective of this study was to confirm the efficacy of ATP based on the evaluation of stored electrograms. From the German Ventritex MD-register stored electrograms of 613 monomorphic ventricular tachycardias in 44 patients were analyzed retrospectively. The cycle length of the ventricular tachycardias was between 265 and 560 ms. The success rate of ATP-induced termination of the episodes reached 89.3%; another 2.3% of the ventricular tachycardias were accelerated by antitachycardia pacing into ventricular fibrillation. Left ventricular function did not influence the success rate, but the success rate was lower for fast ventricular tachycardias > 200/min (63.9%). For ventricular tachycardias < 150 bpm there was no restriction of ATP effectiveness. Of the episodes 72.9% were terminated by the first ATP burst. In these cases the duration of tachycardia was very short (11.9 +/- 2.8 s). Fifty-eight ventricular tachycardias (9.5%) had to be terminated by means of a shock, and only one case required 2 shocks. In patients with more than 10 episodes an individual therapy success > 90% was recorded for 80% of them. The very high success rate of the first ATP attempt in ICD therapy can be achieved with uniform programming, and is confirmed for ventricular tachycardias analyzed on the basis of stored electrograms.

[Adequate performance of a pectoral implanted defibrillator after high-dose radiation therapy for thyroid cancer]. / Regelrechte Funktion eines implantierten Defibrillators nach hochdosierter Strahlentherapie unter Einbeziehung der Defibrillator-Loge.

The interference of implanted defibrillators (ICD) from electronic appliances is small. There is scant knowledge about the effects of radiation therapy on defibrillator function. Existing data commonly derive from in vitro tests of the devices. We report on a 60-year old male patient with a left pectoral implanted ICD, who received radiation therapy for treatment of thyroid cancer. The patient suffered from coronary heart disease with severely impaired left ventricular function, and had to be resuscitated from ventricular fibrillation in December 1997. A defibrillator (Medtronic Jewel 7219 C) was implanted in a left pectoral pocket. In January 2000, a carcinoma of the thyroid gland was diagnosed and treated surgically. The operation was followed by a radiation therapy with curative intention. The patient received a local dosage of 64 Gray (32 sessions in 51 days). The ICD was covered by individually sized metal blocks, and was affected by 10 Gray at maximum. The ICD was inactivated during the radiation applications to avoid inadequate therapy due to electromagnetic interference. The pace-sense parameters during 8 months of follow-up were regular. Three episodes of ventricular fibrillation were terminated adequately by the ICD. Therefore, we assumed a correct ICD funtion after radiation therapy. Radiation-induced damage of the ICD was possible. A surgical transfer of the generator out of the radiation area was rejected on ethical grounds. In the short follow-up period, the ICD function was correct. For our opinion it seems to be justified primarily to control the spontaneous outcome and ICD function at short intervals, especially in view of the poor prognosis of cancer patients.

Catheter-induced mechanical conduction block of right-sided accessory fibers with Mahaim-type preexcitation to guide radiofrequency ablation.

BACKGROUND: Accessory pathways originating at the tricuspid annulus that exhibit decremental antegrade conduction properties (Mahaim-type preexcitation) are amenable to radiofrequency (RF) current catheter ablation. However, a reliable and reproducible strategy for mapping and ablation of these fibers is lacking. METHODS AND RESULTS: Eleven patients with preexcited atrioventricular tachycardia involving a decrementally conducting antegrade accessory pathway underwent complete electrophysiological evaluation and subsequent attempts at RF catheter ablation. Mechanical conduction block at the subannular level of the atrial input to the accessory fiber was induced by catheter manipulation in 8 patients, in 2 of them during atrial fibrillation. RF current was delivered, after resumption of preexcitation, to the site of mechanical block during atrial pacing (n = 6) or atrial fibrillation (n = 2) and eliminated the accessory pathway in all 8 patients. In another patient, mechanical block was not observed, but ablation of the atrial accessory fiber insertion was achieved at the subannular level during atrioventricular tachycardia. The anatomic site of ablation along the tricuspid annulus was anterolateral (n = 1), lateral (n = 3), or posterolateral (n = 5). Failures were encountered in the first patient of the series in whom ablation attempts were directed at the ventricular insertion of the accessory fiber and in a patient in whom ablation of the atrial insertion was attempted at the supraannular level. Recurrence of preexcitation within 12 hours was observed in 5 of 6 patients in whom ablation had been achieved during atrial pacing. Eventually successful repeat sessions were performed the following day using a simplified ablation approach. Thus, a median of 5 RF pulses (range, 1 to 26) per accessory fiber eliminated conduction in 9 (82%) of the 11 patients in 1.9 +/- 0.9 sessions. During a follow-up of 9.5 +/- 2.3 months, preexcitation recurred in 1 patient. CONCLUSIONS: The atrial origin of accessory connections with Mahaim-type preexcitation is apparently confined to the anterolateral-to-posterolateral region of the tricuspid annulus. Mechanical conduction block in the atrial input to the accessory fiber induced at the subannular level by catheter manipulation provides an optimal marker to locate the ablation site, even during atrial fibrillation. To expose early recurrence of antegrade accessory pathway conduction, intermittent atrial pacing in the 12 hours after ablation is advisable; in cases of recurrence, a repeat procedure can readily be performed using just the ablation catheter advanced to the target site at the tricuspid annulus.

[Syncope in supraventricular tachycardia. Incidence, pathomechanism and consequences]. / Synkopen bei supraventrikulären Tachykardien. Häufigkeit, Pathomechanismus und Konsequenzen.

Syncope occurs in up to 20% of patients with supraventricular tachycardias and is suggestive of rapid and dangerous arrhythmias. Incidence, pathomechanism and consequences of syncope in supraventricular tachycardia are reviewed in this presentation. Frequent symptoms in supraventricular tachycardias are palpitations, dizziness or dyspnea. Syncope is more uncommon, however, if a sensation of rapid heart beat precedes a syncope, a causal relationship between arrhythmia and syncope has to be considered. When the surface ECG shows no abnormalities, Holter monitoring or exercise testing usually fail to record a suspected tachycardia, therefore, electrophysiologic study should be performed to verify the underlying arrhythmia. In patients with unexplained syncope supraventricular arrhythmias can be established in up to 15% of patients. However, interpretation of electrophysiologic results has to be performed carefully because functional abnormalities like dual AV nodal pathways can be found in up to 10% of asymptomatic patients. The prognostic value of syncope as a marker for rapid tachycardia or sudden cardiac death is still in discussion. Syncope in patients with Wolff-Parkinson-White syndrome may help to identify patients at risk for ventricular fibrillation due to rapid conduction over an atrioventricular accessory pathway during atrial fibrillation. Syncope in young patients (< 25 years) with Wolff-Parkinson-White syndrome was found to be associated with a short anterograde refractory period (< 220 ms) of the pathway. However, most of the studies were performed retrospectively in selected patients referred to the centers because of severe symptoms, therefore the predictive value of syncope in unselected patients with supraventricular tachycardia remains uncertain.(ABSTRACT TRUNCATED AT 250 WORDS)

[Atrial fibrillation in Wolff-Parkinson-White syndrome. Development and therapy]. / Vorhofflimmern bei Wolff-Parkinson-White-Syndrom. Entstehung und Therapie.

In patients with Wolff-Parkinson-White syndrome the accessory pathway may participate in various tachyarrhythmias thereby influencing symptoms and prognosis. Atrial fibrillation occurs in 10 to 32% of patients and may have life-threatening consequences by precipitating ventricular fibrillation in patients with rapid conduction due to an accessory pathway with short anterograde refractory period (< 250 ms). Pathogenesis of atrial fibrillation in the WPW syndrome and therapeutic options are reviewed in this presentation. Spontaneous degeneration of atrioventricular reentrant tachycardia has been reported to represent the most frequent mode of initiation of atrial fibrillation during electrophysiologic study (up to 64% of episodes). Hemodynamic changes during tachycardia may lead to increased sympathetic tone, hypoxemia or increased tension of the atrial wall, thus, triggering atrial fibrillation. Induction of reentrant tachycardia during electrophysiologic study also has shown to be strongly correlated to its clinical prevalence and is inducible in up to 77% of patients with atrial fibrillation. The pathogenesis and high incidence of atrial fibrillation in patients with WPW syndrome is related to presence and functional properties of the accessory pathway. After surgical excision or catheter ablation more than 90% of patients are free of this arrhythmia. Anterograde conduction properties of the pathway appear to be more important than retrograde properties. High incidence of atrial fibrillation is related to short anterograde refractory periods, and of note, this arrhythmia is rare (3%) in patients with concealed pathways. With intracardiac recordings, Jackman et al. could demonstrate atrial fibrillation due to micro-reentry originating in accessory pathway networks.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheter ablation using radiofrequency current to cure symptomatic patients with tachyarrhythmias related to an accessory atrioventricular pathway.

BACKGROUND: Recent investigations have shown that cure of patients with symptomatic tachyarrhythmias related to an accessory atrioventricular pathway may be achieved by closed-chest electrode catheter ablation of the accessory connection. Direct current shocks have primarily been used for this purpose, but its applicability is limited because of the lack of controlled titration of electrical energy, the infliction of barotrauma, and the need for general anesthesia. Radiofrequency current has been proposed as an alternate energy source. METHODS AND RESULTS: Seventy-three symptomatic patients with Wolff-Parkinson-White syndrome and 19 patients with only retrogradely conducting (concealed) pathways underwent ablative therapy with radiofrequency current. There were 71 accessory pathways located on the left side of the heart (57 free-wall and 14 posteroseptal pathways) and 25 on the right side (11 free-wall, seven posteroseptal, and seven midseptal or anteroseptal pathways). In patients with right-sided pathways, ablation was attempted via a catheter positioned at the atrial aspect of the tricuspid annulus. In patients with a left-sided free-wall accessory pathway, a novel approach was used in which the ablation catheter was positioned in the left ventricle directly below the mitral annulus. Accessory pathway conduction was permanently abolished in 79 patients (86%). Growing experience and improved catheter technology resulted in a 100% success rate after the 52nd consecutive patient. Failures were mainly the result of inadequate catheters used initially or an unfavorable approach to left posteroseptal pathways. CONCLUSIONS: Catheter ablation of accessory atrioventricular pathways by the use of radiofrequency current is an effective and safe therapeutic modality for patients with symptomatic tachyarrhythmias mediated by these pathways.

Radiofrequency current catheter ablation of accessory atrioventricular pathways.

Tachyarrhythmias mediated by an accessory atrioventricular pathway and which are refractory to drug therapy have been treated surgically with variable success. Early results of direct-current catheter ablation were encouraging but were associated with complications such as barotrauma and the need for a general anaesthetic. We have investigated the endocardial application of radiofrequency current which is a potentially safer technique. Of 105 patients with an accessory atrioventricular pathway, 79 were located on the left side of the heart and 32 on the right side. Accessory pathway conduction was permanently abolished in 93 (89%) patients. Complications developed in 3 patients: thrombotic occlusion of a femoral artery, arteriovenous fistula formation at the site of groin puncture, and left ventricular rupture with cardiac tamponade after direct-current shocks. There were no deaths from the procedure. We conclude that radiofrequency current catheter ablation is both effective and safe for patients with symptomatic tachyarrhythmias mediated by accessory atrioventricular pathways.

[Loading-induced ST-interval elevations in the case of normal coronary arteries. The angiographic demonstration of loading-induced coronary artery spasm]. / Belastungsinduzierte ST-Strecken-Hebungen bei normalen Koronararterien. Angiographischer Nachweis eines belastungsinduzierten Koronararterienspasmus.

In a 60-year-old man with exercise-dependent anginal symptoms, reversible ST segment elevations of maximally 0.8 mV occurred in the anterior chest leads during ergometric exercise at 75 W. Angiography excluded coronary artery stenoses. To demonstrate whether he had exercise-dependent vasospastic angina, angiography was performed during bicycle ergometry. At 75 W the typical symptoms recurred, accompanied by ST elevations in the ECG. At the same time, spasm in the region of the anterior interventricular branch was demonstrated angiographically; it disappeared at once after intracoronary injection of 200 micrograms nitroglycerin. The patient subsequently remained free of symptoms while taking isosorbide dinitrate (120 mg daily) and nifedipine (80 mg daily).

Encainide versus flecainide for chronic atrial and junctional ectopic tachycardia.

For treatment of chronic atrial and junctional ectopic tachycardia, standard antiarrhythmic therapy has been shown to be ineffective in most patients. Both the intravenous efficacy and the oral efficacy of 2 class IC antiarrhythmic drugs, encainide and flecainide, were studied in 16 patients with atrial ectopic tachycardia and in 3 patients with junctional ectopic tachycardia, using exercise testing, 24-hour long-term electrocardiography and programmed electrical stimulation. All patients had been previously treated unsuccessfully with several antiarrhythmic drugs. In 5 patients, tachycardia was persistent; in the remaining patients, it occurred intermittently for more than 12 hours/day. Intravenous encainide, in doses ranging from 0.3 to 2.0 mg/kg body weight, was given to 5 patients with atrial ectopic tachycardia, and it terminated atrial ectopic tachycardia in all patients. Intravenous flecainide was given to 9 patients, and it terminated atrial tachycardia in 4 and slowed the tachycardia rate in 2. It terminated junctional tachycardia in 2 patients and slowed tachycardia rate in 1. During a follow-up period of 10 +/- 5 months, oral encainide, in dosages between 150 and 225 mg/day, completely suppressed atrial ectopic activity in 4 patients. In the remaining patient, encainide reduced the number of tachycardia episodes markedly but had to be withdrawn because of intolerable side effects. During a 12 +/- 11-month (median 6) follow-up, oral flecainide at dosages between 200 and 300 mg/day, completely suppressed ectopic activity in 7 patients and improved symptoms in 5. Only 1 patient failed to respond to oral flecainide. The results of this study indicate that both encainide and flecainide are effective in the treatment of chronic ectopic atrial and junctional tachycardia.