Lawrence S. Klein

Clinical features of amiodarone-induced pulmonary toxicity.

The incidence and clinical predictors of amiodarone pulmonary toxicity were examined in 573 patients treated with amiodarone for recurrent ventricular (456 patients) or supraventricular (117 patients) tachyarrhythmias. Amiodarone pulmonary toxicity was diagnosed in 33 of the 573 patients (5.8%), based on symptoms and new chest radiographic abnormalities (32 of 33 patients) and supported by abnormal pulmonary biopsy (13 of 14 patients), low pulmonary diffusion capacity (DLCO) (nine of 13 patients), and/or abnormal gallium lung scan (11 of 16 patients). Toxicity occurred between 6 days and 60 months of treatment for a cumulative risk of 9.1%, with the highest incidence occurring during the first 12 months (18 of 33 patients). Older patients developed it more frequently (62.7 +/- 1.7 versus 57.4 +/- 0.5 years, p = 0.018), with no cases diagnosed in patients who started therapy at less than 40 years of age. Gender, underlying heart disease, arrhythmia, and pretreatment chest radiographic, spirometric, or lung volume abnormalities did not predict development of amiodarone pulmonary toxicity, whereas pretreatment DLCO was lower in the group developing it (76.0 +/- 5.5% versus 90.4 +/- 1.4%, p = 0.01). There was a higher mean daily amiodarone maintenance dose in the pulmonary toxicity group (517 +/- 25 versus 409 +/- 6 mg, p less than 0.001) but no difference in loading dose. No patient receiving a mean daily maintenance dose less than 305 mg developed pulmonary toxicity. Patients who developed toxicity had higher plasma desethylamiodarone (2.34 +/- 0.18 versus 1.92 +/- 0.04 micrograms/ml, p = 0.009) but not amiodarone concentrations during maintenance therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of atrioventricular interval during pacing or reciprocating tachycardia on atrial size, pressure, and refractory period. Contraction-excitation feedback in human atrium.

To determine whether a contraction-excitation feedback mechanism exists in human atrium, we investigated the effects of varying the atrioventricular (AV) interval from 0 to 360 msec during AV pacing at a cycle length of 400 msec on atrial pressure, size, and refractoriness in 10 patients (group 1, without supraventricular tachycardia). The same parameters were determined in another 10 patients (group 2, with different spontaneous AV relations) during AV reciprocating tachycardia or AV nodal reciprocating tachycardia and during high right atrial (RA) pacing at the tachycardia cycle length. In group 1 patients, peak and mean RA pressure, RA effective refractory period (RA-ERP), and left atrial (LA) size all decreased to minimal values at an AV interval of 120 msec and remained low as the AV interval was increased and approached 400 msec. The increase in each of the variables from its lowest to greatest value was as follows: Mean systemic blood pressure, 20.9 +/- 3.1 mm Hg; LA size, 0.55 +/- 0.05 cm; RA peak pressure, 10.4 +/- 1.8 mm Hg; RA mean pressure, 3.5 +/- 0.6 mm Hg; and RA-ERP, 22.5 +/- 3.0 msec, p less than 0.001 for each. The weighted mean correlation coefficient with RA-ERP was significant for RA peak pressure and LA size (p less than 0.001 for each). These same relations were investigated in five patients with the Wolff-Parkinson-White syndrome and AV reciprocating tachycardia and five patients with AV nodal reciprocating tachycardia (group 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency ablation for atrioventricular node reentrant tachycardia : comparison between fast (anterior) and slow (posterior) pathway ablation

OBJECTIVESnWe compared the electrophysiologic effects on atrioventricular (AV) node physiology of selective fast versus selective slow pathway radiofrequency ablation in 42 patients with drug-resistant AV node reentrant tachycardia who underwent 51 ablation attempts to prevent tachycardia recurrence while preserving AV conduction.nnnBACKGROUNDnThe recent introduction of radiofrequency ablation to treat AV node reentrant tachycardia allows the opportunity to study the effects of selective elimination of the different limbs involved in AV node reentrant tachycardia.nnnMETHODSnSelective fast pathway ablation was attempted in 13 patients by delivering radiofrequency energy anteriorly across the tricuspid valve anulus. Selective slow pathway ablation was attempted in 29 patients by delivering radiofrequency energy posteriorly across the tricuspid valve anulus at sites where putative slow pathway potentials were recorded.nnnRESULTSnSelective fast pathway ablation eliminated AV node reentrant tachycardia without AV block in 6 (46%) of 13 patients after one ablation session and in an additional 3 patients (69% of total) after repeat ablation sessions. Slow pathway ablation eliminated AV node reentrant tachycardia without AV block in 26 (90%) of 29 patients after one radiofrequency ablation session and in an additional 2 patients (97% of total) after repeat ablation sessions. Selective fast pathway ablation increased the PR interval (140 to 220 ms, p = 0.0001) and AH interval (66 to 153 ms, p = 0.0001), whereas slow pathway ablation did not change these intervals. Fast pathway radiofrequency ablation caused retrograde block in 7 (64%) of 11 patients, whereas no patients undergoing slow pathway ablation developed selective retrograde block. Single AV node echo beats were commonly induced after slow but not fast pathway ablation (17 of 29 patients vs. 1 of 11 patients, respectively, p = 0.01) and did not predict recurrence of AV node reentrant tachycardia.nnnCONCLUSIONSnSuccessful selective radiofrequency ablation of fast or slow pathways in patients with AV node reentrant tachycardia resulted in different electrophysiologic properties after ablation. Slow pathway ablation produced more successful outcomes, with a decreased prevalence of recurrent AV node reentrant tachycardia or AV block.

Radiofrequency catheter ablation of Mahaim fibers at the tricuspid annulus.

BackgroundThe purpose of this study was to test the feasibility of radiofrequency catheter ablation of Mahaim fibers at the tricuspid annulus. Methods and ResultsFour patients who fulfilled criteria for having Mahaim fibers and preexcited reciprocating tachycardia underwent radiofrequency catheter ablation. Three patients had atriofascicular connections, and one patient had an atrioventricular connection. The mean age was 27 years (age range, 11-48 years). All patients had highly symptomatic tachycardias, producing syncope in one patient and presyncope in the remaining three patients. Symptoms were present for a mean of 13 years (range, 4- years). All pathways conducted only anterogradely, and preexcitation resulted in a left bundle branch block QRS morphology. Adenosine caused block in the accessory pathway in the three patients in whom it was tested. The stimulus to delta interval increased by 75 msec (range, 35-90 msec) during rapid atrial pacing. The atrial insertion of the Mahaim fiber was in the right lateral atrium in one patient, right posterolateral atrium in two patients, and right posterior atrium in one patient. The ventricular insertion was in the distal right bundle branch in three patients and in the posterolateral right ventricle near tricuspid annulus in the patient with an atrioventricular connection. Stimulus to delta wave mapping was used to help localize the atrial insertion of the atriofascicular connections. A mean of 15 radiofrequency pulses (range, 10-19 pulses) delivered to the tricuspid annulus in the posterior to lateral regions eliminated accessory pathway conduction in all patients. No complications occurred. Tachycardia did recur during a mean follow-up of 8 months (range, 2-15 months). ConclusionRadiofrequency current applied to the tricuspid annulus can safely eliminate tachycardia in patients with Mahaim fibers.

Antitachycardia devices: Realities and promises

Nonpharmacologic therapy for ventricular arrhythmias has gained growing attention with the development of the implantable cardioverter-defibrillator. In addition, the reports of adverse effects of drug therapy from several studies, including the Cardiac Arrhythmia Suppression Trial (CAST), have supported the need for these devices. The development of new implantable cardioverter-defibrillators that have the capability of antitachycardia pacing, bradycardia pacing, cardioversion and defibrillation has enhanced their clinical utility. The currently available implantable cardioverter-defibrillators have been shown to significantly improve survival after sudden cardiac arrest in patients with life-threatening ventricular arrhythmias. Newer devices with expanded capabilities may reduce mortality even further. In this report the features of currently available antitachycardia devices and implantable cardioverter-defibrillators are reviewed and the features and current implant data on newer antitachycardia devices are discussed.

Multiple accessory pathways in the permanent form of junctional reciprocating tachycardia

The permanent form of junctional reciprocating tachycardia (PJRT) has been successfully eliminated by ablation of the accessory pathway responsible for the tachycardia. The coexistence of multiple accessory pathways responsible for different, long RP-interval tachycardias was not documented previously. Five patients with PJRT underwent radiofrequency catheter ablation of accessory pathways. Three of 5 patients had 2 accessory pathways each: 1 had 2 left free wall accessory pathways, another had a right posterior free wall and right posteroseptal pathway, whereas the third had 2 right posteroseptal pathways approximately 1 cm apart. The remaining 2 patients each had 1 right posteroseptal accessory pathway. Seven of 8 pathways were successfully ablated with a median of 3 radiofrequency pulses. No patient developed complications. Peak serum creatine kinase ranged from 131 to 311 IU/liter, with peak MB fraction 7 to 17 IU/liter, or 5 to 11%. Follow-up electrophysiologic study, 29 to 70 days after ablation, revealed no inducible tachycardia and no evidence of accessory pathway conduction, except for the 1 pathway not ablated. All patients remained asymptomatic 17 to 29 months after ablation. Thus, patients with PJRT can have several accessory pathways that can be safely and effectively eliminated with radiofrequency catheter ablation.

Elimination of AV Nodal Reentrant Tachycardia with 2:1 VA Block by Posteroseptal Ablation

AV Nodal Reentrant Tachycardia. AV nodal reentry capable of VA block during tachycardia was successfully eliminated using a posteroseptal ablation pulse delivered well away from the site of earliest atrial activation during tachycardia. A possible explanation is that the arrhythmia represented typical AV nodal reentrant tachycardia with transient intra atrial conduction block during tachycardia.

Phenylephrine increases T wave shock energy required to induce ventricular fibrillation.

Phenylephrine Increases VFT. Introduction: Previous reports in experimental models have suggested that ventricular fibrillation threshold (VFT) can be changed by manipulating cardiac neural tone using agents such as phenylephrine. The purpose of this study was to determine whether phenylephrine increased the energy required to induce VF in humans undergoing such induction using DC energy applied to the T wave.

Alcohol Ablation of Ventricular Tachycardia

Alcohol Ablation of Ventricular Tachycardia. Ventricular tachycardia that is refractory to medical management has been treated with surgical resection, catheter ablation, and antitachycardia pacemaker. In this case report we describe the use of transcoronary alcohol ablation to treat a patients ventricular tachycardia. This is accomplished by using ethanol to destroy the site of origin or pathways used in ventricular tachycardia.

976-12 Reduced Reflex Vagal Activity in Patients with AV Nodal Reentrant Tachycardia Compared to Patients with Atrioventricular Reentrant Tachycardia

Decreased heart rate variability, a manifestation of reduced tonic vagal activity. has been reported following radiofrequency catheter ablation (RFCA) for AV nodal reentrant tachycardia (AVNRT). Disruption of parasympathetic fibers in the posteroseptal region is the proposed mechanism. Baroreflex sensitivity (BRS). an index of reflex vagal activity. has not been evaluated in patients with AVNRT. We studied BRS prior to and immediately following RFCA in 20 patients with AVNRT(age 13–65 years, mean 42; 15 females. 5 males). Fourteen patients with atrioventricular reentrant tachycardia (AVRT) and free wall accessory pathways (age 14–46 years. mean 25; 6 females. 8 males) were evaluated as controls (RFCA site far from posteroseptal region I. BRS (msec/mmHg) was assessed with continuous femoral artery blood pressure (BP) and ECG recordings during the bolus administration of phenylephrine (400 μg). BRS was calculated as the slope of the change in cycle length vs the change in systolic BP during the first sustained rise in BP. At baseline. prior to RFCA. mean BRS for patients with AVNRT was significantly less than for patients with AVRT (8.3xa0±xa05.9 vs 22.1xa0±xa010.3; Pxa0lxa00.0002). This difference remained significant when controlled for age (pxa0lxa00.0002) and male gender (pxa0lxa00.0003). but not for female gender (pxa0lxa00.09). Following RFCA there was no significant change in BRS for patients with AVNRT (9.3xa0±xa07.6) or AVRT (17.3xa0±xa09.6) compared to pre-RFCA values. This comparison remained insignificant when controlled for age or gender. These results suggest that in the baseline state, patients with AVNRT have lower reflex vagal activity than patients with AVRT. Reduced reflex vagal activity may contribute to the development of sustained AVNRT in patients with dual AV nodal physiology. RFCA did not alter BRS in either patient group.