Debra R. Johnston

Long-Term efficacy of antitachycardia pacing for supraventricular and ventricular tachycardias

Over a 14-year period, 53 patients received implanted pacemakers to assist in the control of recurrent tachycardias. Indications were: prevention of tachycardia in 2 patients with supraventricular tachycardia (SVT), and 4 with ventricular tachycardia (VT); termination of tachycardia (15 SVT, 20 VT); and long-term periodic programmed electrical stimulation with potential for tachycardia termination (12 VT). Pacemakers for prevention of VT were implanted in 3 patients with prolonged QT interval syndromes and 1 in whom Holter monitoring showed a significant reduction in ectopic activity during pacing. Pacers were implanted for tachycardia termination only after patients underwent a rigorous protocol aimed at achieving 100 trials of the proposed modality. Patients with tachycardia also requiring antibradycardia pacemakers received pacemakers capable of noninvasive programmed stimulation for use during follow-up. There were no tachycardia recurrences among those patients in whom pacemakers were implanted for prevention. Pacers capable of outpatient programmed stimulation were useful, and it may be desirable to expand their use. The 15 patients with pacers designed for termination of SVT were followed for a mean of 68 months. Among these, actuarial continuation of pacing efficacy was 93% at 1 year, and 78% at 5 years. The 20 patients with pacers for termination of VT were followed for a mean of 37 months. Actuarial efficacy was 78% at 1 year, and 55% at 5 years. Sudden death occurred in 4 of these patients, none clearly pacer related. Pacemakers can play a major therapeutic role in some patients with recurrent tachycardias. The role of such pacemakers in patients with VT may be expanded with the advent of combined pacer-defibrillators.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonsurgical electrical ablation of tachycardias: importance of prior in vitro testing of catheter leads.

Nonsurgical electrical ablation of tachycardia pathways or foci has been attempted or carried out using a variety of temporary pacing catheter leads. To determine the ability of such leads to withstand the high energies used in such procedures, 34 leads were suspended in saline, and subjected to repeated electrical shocks. Small (4 French) temporary pacing leads made by a variety of manufacturers tolerated multiple shocks up to 100 joules; above this level, failures became increasingly common, although usually the failure mode was benign with respect to patient care implications. Testing of 6, 7, and 8 French leads revealed considerable inter‐and intra‐manufacturer differences in the ability to withstand higher energy shocks, reflecting differences in materials and fabrication techniques. It is concluded that careful in vitro lead testing is required prior to using identical models in humans for arrhythmia ablation procedures.

Activation mapping in patients with coronary artery disease with multiple ventricular tachycardia configurations: Occurrence and therapeutic implications of widely separate apparent sites of origin

Catheter or intraoperative activation mapping studies, or both, were performed in 17 patients with coronary artery disease with two to four distinct configurations of ventricular tachycardia, resistant to a mean of 12.1 +/- 6.0 antiarrhythmic drug trials per patient. Mapping studies were performed to guide anticipated surgical ablation of arrhythmias. Activation map data were adequate to determine sites of origin of 30 (64%) of 47 observed tachycardia configurations. These 30 ventricular tachycardias (26 observed clinically) were mapped to 22 separate endocardial sites of origin. Sites of origin of distinct tachycardias were identical or closely adjacent (within 3 cm) in six patients and widely separate (greater than or equal to 4 cm) in eight patients (47% of the group). Activation maps were not adequate to determine sites of origin of 17 (36%) of the 47 tachycardias, including all configurations in three patients. Fifteen patients underwent surgery for control of ventricular tachycardia: aggressive, map-guided endocardial resection (mean 26.5 +/- 14.2 cm2) in 12 patients with identified sites of tachycardia origin and extensive resection of visible endocardial scar (2 patients) or encircling endocardial ventriculotomy (1 patient) in those in whom the sites of origin of all clinical tachycardias remained undetermined. Two inoperable patients were treated with amiodarone. During postoperative electrophysiologic tests (11 of 13 surgical survivors), ventricular tachyarrhythmias were initially uninducible in only 4 of 11 patients. However, in two patients only nonclinical arrhythmias (ventricular flutter) were induced. Six (21%) of 29 clinical tachycardias whose sites of origin were either not determined or not resected (right septum or papillary muscle) remained inducible in five patients. Using previously ineffective antiarrhythmic drugs, initially inducible arrhythmias became uninducible (two patients), or harder to induce than preoperatively (five patients). As a result of surgical resections alone or in combination with previously ineffective drugs (and amiodarone in two inoperable patients), there were no recurrences of ventricular tachycardia in 14 (93%) of 15 patients discharged during 19.0 +/- 14.3 months of follow-up study. Thus, activation mapping may commonly reveal separate apparent sites of origin for clinically observed, morphologically distinct, highly drug-refractory ventricular tachycardias in patients with coronary artery disease with multiple tachycardia configurations. Extensive surgical resection of identified sites of origin may be required to ablate arrhythmias in these patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Implantable Pacers for Tachycardia Termination: Stimulation Techniques and Long‐Term Efficacy

The long‐term efficacy of pacing for termination o/supraventricular tachycardia (SVT) and ventricular tachycardia (VT) was reviewed. Increasingly complex and sophisticated antitachycardia pacing stimulation patterns have evolved, and are outlined. Although excellent results are reported with simple patterns, it may be that the more complex algorithms increase the percentage o/tachycardia patients who may be candidates for implantation of a device. In the papers reviewed, there were 460 patients, 268 with SVT, and 192 with VT. Results were judged to be good‐excellent in 96.5% of both VT and SVT groups.

Value of holter monitoring in predicting long-term efficacy and inefficacy of amiodarone used alone and in combination with class 1A antiarrhythmic agents in patients with ventricular tachycardia

The value of two reported and two new ambulatory electrocardiographic (Holter) criteria was studied in 80 patients taking amiodarone for refractory recurrent sustained ventricular tachycardia. In the 80 patients, the four Holter criteria were as follows: I-85% or greater reduction of ventricular premature complexes and abolition of couplets and nonsustained ventricular tachycardia in 74 patients who had 10 or more ventricular premature complexes/h, or any couplets or nonsustained ventricular tachycardia/24 hours at baseline; II-abolition of nonsustained ventricular tachycardia in 51 patients who had nonsustained ventricular tachycardia at baseline; III-85% or greater reduction of ventricular premature complexes and abolition of nonsustained ventricular tachycardia in 64 patients who had 30 or more ventricular premature complexes/h at baseline; and IV-85% or greater reduction of ventricular premature complexes and abolition of nonsustained ventricular tachycardia in 73 patients who had 10 or more ventricular premature complexes/h at baseline. Amiodarone was judged effective in, respectively, 51 of 74, 44 of 51, 51 of 64 and 61 of 73 patients by criterion I, II, III or IV. During the follow-up period (19 +/- 20 months), there were 19 instances of recurrence of ventricular arrhythmia or sudden death. Actuarial arrhythmia-free survival rate at 24 months was 84, 74, 86 and 85%, respectively, in patients with efficacy by criterion I, II, III or IV and 61, 43, 48 and 39%, respectively, in patients with inefficacy (p less than 0.015 for all). Many patients with efficacy by Holter criteria, however, had a recurrence of arrhythmia, suggesting insensitivity of these Holter criteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic value of the changes in the mode of ventricular tachycardia induction during therapy with amiodarone or amiodarone and a class 1A antiarrhythmic agent

The prognostic value of 3 previously reported programmed stimulation efficacy criteria was studied in 70 patients taking amiodarone for sustained ventricular tachycardia (VT). At baseline all patients had VT inducible by programmed stimulation. After amiodarone loading (935 +/- 271 mg/day for 16 +/- 7 days), efficacy of amiodarone was determined by 3 programmed stimulation criteria (criterion I = VT not inducible or 15 beats or less; criterion II = VT not inducible or harder to induce; criterion III = VT not easier to induce). Amiodarone was effective in 12, 25 and 49 of 70 patients by criteria I, II and III, respectively. There were 16 recurrences or cardiac arrest during the follow-up period (19 +/- 19 months). Actuarial arrhythmia-free survival rates at 1 and 2 years were: 90% and 90% in patients with efficacy by criterion I and 78% and 78% in patients with inefficacy, respectively; 84% and 84% in patients with efficacy by criterion II and 78% and 78% in patients with inefficacy, respectively; and 80% and 80% in patients with efficacy by criterion III and 79% and 79% in patients with inefficacy, respectively (difference not significant for all). From the results of follow-up at 2 years, sensitivities of criteria I, II and III were 92%, 75% and 33%, respectively. Specificities were 17%, 26% and 70%, respectively, and predictive accuracies were 43%, 43% and 67%, respectively. Thus, patients with efficacy by criterion I appear to have a better prognosis when compared with patients with inefficacy. However, many patients with inefficacy by criterion I had a good outcome (nonspecificity).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of programmed stimulation and Holter monitoring for predicting long-term efficacy and inefficacy of amiodarone used alone or in combination with a class 1A antiarrhythmic agent in patients with ventricular tachyarrhythmia

The values of two Holter ambulatory electrocardiographic monitoring criteria and one programmed stimulation efficacy criterion reported to be predictive of the efficacy of amiodarone were compared in 70 patients taking amiodarone for sustained ventricular tachyarrhythmias. At baseline, all patients had ventricular tachycardia inducible by programmed stimulation. After amiodarone loading (935 +/- 271 mg for 16 +/- 7 days), efficacy was determined by a programmed stimulation criterion (ventricular tachycardia no longer inducible or less than or equal to 15 beats) and two Holter monitoring criteria (Holter I = greater than or equal to 85% reduction of ventricular premature complexes and abolition of couplets and triplets in 64 patients who had greater than or equal to 10 ventricular premature complexes/h or couplets or triplets or both before therapy; Holter II = abolition of triplets in 41 patients who had triplets before therapy). Amiodarone was effective in 12 of 70 patients by the programmed stimulation criterion, in 49 of 64 patients by Holter criterion I and in 37 of 41 patients by Holter criterion II. In assessing efficacy of amiodarone, programmed stimulation and Holter criteria were discordant in 69% of patients or more (p less than 0.001). There were 16 recurrences or sudden deaths during the entire follow-up period (19 +/- 19 months). Arrhythmia-free survival rates at 24 months of patients with efficacy and inefficacy by each criterion, respectively, were 90 and 78% by programmed stimulation, 84 and 62% by Holter criterion I (p less than 0.05) and 73 and 50% by Holter criterion II (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Direct Current Shock Ablation: Quantitative Assessment of Proarrhythmic Effects

Catheter ablation using direct current (DC) shock has proved invaluable in the management of a variety of tachycardias. However, sporadic reports of fatal arrhythmias following ablation have raised the question of the proarrhythmic potential of DC shock ablation. The present study was undertaken in 45 patients to assess prospectively any proarrhythmia related to DC shock ablation, using matched pre‐ and postablation Holter monitors and programmed electrical stimulation (PES). Nineteen of these patients had Holter monitors for three successive postablation days to observe trends. There was unmatched data in 11 additional patients. All 56 patients provided prospective follow‐up for clinical events. There was no immediate sustained VT/VF at the time of the ablation. Four patients had sustained VT in the first 72 hours after ablation; three episodes were similar to the preablation clinical arrhythmias; one patient had torsades de pointes interrupting bradycardia. Twelve patients met Holter, PES, or clinical criteria for proarrhythmia; none were treated on the basis of these findings. On Holter monitoring, there were significant increases in VPCs/hour and couplets/hour in patients undergoing atrial or atrioventricular juncfional ablations; and an increase in couplets after accessory pathway ablations. Increases in these categories were not significant for VT patients; nor were increases in episodes of VT/hour or atrial arrhythmias significant in any group. Patients were followed for 44 ± 33 months, with an actuarial survival of 95% at 1 year, 88% at 3 years, and 85% at 4 years. There were six deaths during follow‐up. Two patients had sudden death; one at 2 months had early evidence of proarrhythmia; the other at 32 months may have represented later myocardia deterioration. One patient died of heart failure at 77 months; and there were three noncardiac deaths. DC shock ablation in humans is much less proarrhythmic than in dogs. The low incidence of clinical proarrhythmic events during prolonged follow‐up after discharge resulted in low sensitivity, specificity, and positive predictive values for Holter and PES, although the negative predictive values of these tests were > 90%. Only one of 12 patients who met criteria for proarrhythmia in the days immediately following ablation had subsequent clinical events consistent with proarrhythmia. These results may be useful as standards for comparison with results of radiofrequency or other ablation modalities.

Programmed Electrical Stimulation of the Ventricle: An Efficient, Sensitive, and Specific Protocol

A relatively simple and evident ventricular programmed electrical stimulation (PES) protocol was developed, capable of achieving high degrees of sensitivity and specificity. In a series of 481 subjects, 1, 2, and 3 extrasfimuli (ES) were used successively during sinus rhythm and ventricular pacing at two drive cycle lengths, at one or more ventricular sites, together with rapid ventricular pacing, and other maneuvers such as isoproterenol infusion. Three ES were used immediately after two ES at each drive rate, rather than returning after completion of the protocol with two ES. Using the protocol, appropriate arrhythmias could be induced in 88% of all patients with ventricularfibrillation, 84% of all patients with sustained ventricular tachycardia (91% with underlying coronary disease), and 58% of patients with severe nonsus‐tained ventricular tachycardia. There were significant differences in inducibility between patients whose ventricular arrhythmias were due to coronary artery disease and other causes. In contrast, sustained ventricular arrhythmias fall ventricular fibrillation) could be induced in only 5% of a control group of control patients, for a specificity of 95%. The protocol described is simpler and more efficient than those that use exhaustive testing of two ES before going to three ES. Three ES during sinus rhythm proved to be the most productive step, with a higher yield ratio (true:false‐positives) than two ES or three ES during pacing, especially at fasterrates. Greater efficiency is also achieved by leaving the timing of an extrastimulus just beyond its effective refractory period when an additional extrastimulus is to be added, compared to protocols in which the extrastimulus is moved later in the cycle and then decremented in tandem with the additional extrastimulus. Coupling intervals < 200 msec produced some false‐positives, but fewer overall than intervals < 200 msec, and with yield ratios comparable to other protocol steps. The protocol described meets NASPE standardsfor ventricular programmed stimulation protocols, and with its demonstrated specificity and relative simplicity and efficiency may be useful as a model for groups not yet committed to an alternative protocol.