Effects of intravenous disopyramide and quinidine on normal myocardium and on the characteristics of arrhythmias: intraindividual comparison in patients with sustained ventricular tachycardia

Intraindividual comparison of the acute response to intravenousquinidine and to intravenous disopyramide was performed in 27patients with sustained ventricular tachycardia ( VT) who underwentserial electrophysiological studies. In each patient, sustainedVT could be reproducibly initiated by programmed ventricularstimulation during control studies. Quinidine and disopyramideprevented inducibility of sustained VT in 7 and 8 of the 27patients, respectively. Six patients were concordant respondersto both drugs and 18 patients were concordant non-respondersresulting in a total of 24 patients (89%) who had a concordantresult (P<0.01). In the 18 non-responders with induciblesustained VT after both drugs, quinidine and disopyramide causedqualitatively and quantitatively similar changes in the characteristicsof the VT: prolongation of the interval between the initiatingextrastimulus and the first beat of VT by 36 and 39%, and anincrease in VT cycle length by 21 and 29%, respectively. TheQRS morphology of VT was concordantly altered in 13 of these18 patients (72%). In all 27 patients, quinidine and disopyramidecaused a quantitatively similar prolongation of ventricularrefractoriness by 12 and 14%, of the QRS duration by 14 and13% and of the QTc interval by 13 and 13%, respectively. Theclinical data obtained at comparable plasma concentrations confirmthe experimental presumption that quinidine and disopyramidehave qualitatively and quantitatively similar electrophysiologicaleffects not only on normal myocardium but also on the characteristicsof VT, resulting in a significant concordance of antiarrhythmicresponses.     

In-hospital experience with multiprogrammable implantable antitachycardia/antifibrillation devices

Multiprogrammable, automatic internal defibrillators with (n= 45) and without (n = 15) antitachycardia pacing features wereimplanted in 60 consecutive patients with refractory, malignantventricular tachycardia (VT) (n = 42) or fibrillation (VF) (n= 18). Left ventricular (LV) ejectionfraction wasreduced to39% ± 12% as a result of structural heart disease in56 patients. The complexity of the systems caused no additionalrisks to the surgical procedure or postoperative management.VT/VF detection parameters were individually adjusted to thearrhythmia type (detection cycle length 323 ± 40 ms inpatients with VF vs 405 ± 40 ms for VT patients, P<0.05)and incidence (longer detection periods if frequent nonsustainedVT was also present). Shock energy was reduced in patients withVT as compared to VF(11J vs 24J, P<0.05). Antitachycardiapacing was activated in 19/28 (68%) patients with well toleratedVT. Signal, telemetry, as detected by the device, combined withprogrammability allowed the device to be checked for correctdecisions (these were inappropriate in four patients in threeof whom corrections were non-invasive) prior to discharge. Inconclusion, in the automatic tachyarrhythmia control deviceswe studied, programmability and flexibility appeared to be clinicallysafe and useful. Prolonged observation periods are required,however, to evaluate the true clinical safety and persistentefficacy of device programmability and flexibility.     

Atrial Flutter Ablation in Inducible Patients during Pulmonary Vein Atrum Isolation: A Randomized Comparison

Background: The incidence of atrial flutter (AFL) post pulmonary vein antrum isolation (PVAI) in patients with atrial fibrillation (AF) is reported to be between 8% and 20%. The need for right or left AFL ablation during the initial PVAI procedure remains controversial. We prospectively compared mapping and ablation versus no ablative treatment of inducible AFL during PVAI. Methods and Results: In 220 patients (167 men, mean age 56 ± 15 years) with symptomatic AF presenting for PVAI, burst pacing from the high right atrium and coronary sinus was performed to determine AFL inducibility. A total of 25 patients with sustained (17 patients) or reproducible (eight patients) AFL were included in this study. Patients were randomized to mapping and ablation of AFL using the CARTO 3D mapping system (Biosense Webster, Diamond Bar, CA, USA) versus no further ablation. Typical AFL was induced in 48% of the patients. During a follow‐up of 12 ± 4 months, recurrences were determined by serial 48‐h Holter and event monitors. Recurrence rates, time to recurrence, and AFL cycle length differences between both groups were not statistically significant. Conclusion: These data suggest that inducibility of AFL post PVAI does not predict long‐term incidence of AFL. Moreover, this study demonstrates little benefit to mapping and ablation of these arrhythmias during the PVAI procedures.     

Implantable Cardioverter Defibrillator: Possible Hazards of Electromagnetic Interference

We report on three patients with an automatic, implantable cardioverter defibrillator (AICD, CPI) in whom the device had been deactivated due to electromagnetic interference. In all cases, the source of the electromagnetic disturbances could be identified.