Cost-effectiveness of catheter ablation in patients with ventricular tachycardia.

BACKGROUND: This study evaluated the cost-effectiveness of catheter ablation therapy versus amiodarone for treating ventricular tachycardia (VT) in patients with structural heart disease. The analysis used a societal perspective for a hypothetical cohort of VT patients with implantable cardioverter-defibrillators, who were experiencing frequent shocks. METHODS AND RESULTS: We calculated incremental cost-effectiveness of ablation relative to amiodarone over 5 years after treatment initiation. Event probabilities were from the Chilli randomized clinical trial (Chilli Cooled Ablation System, Cardiac Pathways Corporation, Sunnyvale, Calif), the literature, and a consensus panel. Costs were from 1998 national Medicare reimbursement schedules. Quality-of-life weights (utilities) were estimated using an established preference measurement technique. In a hypothetical cohort of 10 000 patients, 5-year costs were higher for patients undergoing ablation compared with amiodarone therapy ($21 795 versus $19 075). Ablation also produced a greater increase in quality of life (2.78 versus 2.65 quality-adjusted life-years [QALYs]). This yielded a cost-effectiveness ratio of $20 923 per QALY gained for ablation compared with amiodarone. Results were relatively insensitive to assumptions about ablation success and durability. In less severe patients with good ejection fractions who suffer their first VT episode, the incremental cost-effectiveness ratio was $6028 per QALY gained. These cost-effectiveness ratios are within the range generally thought to warrant technology adoption. CONCLUSIONS: This study demonstrates that, from a societal perspective, catheter ablation appears to be a cost-effective alternative to amiodarone for treating VT patients.

Atypical atrial flutter originating in the right atrial free wall.

BACKGROUND: Data from experimental models of atrial flutter indicate that macro-reentrant circuits may be confined by anatomic and functional barriers remote from the tricuspid annulus-eustachian ridge atrial isthmus. Data characterizing the various forms of atypical atrial flutter in humans are limited. METHODS AND RESULTS: In 6 of 160 consecutive patients referred for ablation of counterclockwise and/or clockwise typical atrial flutter, an additional atypical atrial flutter was mapped to the right atrial free wall. Five patients had no prior cardiac surgery. Incisional atrial tachycardia was excluded in the remaining patient. High-density electroanatomic maps of the reentrant circuit were obtained in 3 patients. Radiofrequency energy application from a discrete midlateral right atrial central line of conduction block to the inferior vena cava terminated and prevented the reinduction of atypical atrial flutter in each patient. Atrial flutter has not recurred in any patient (follow-up, 18+/-17 months; range, 3 to 40 months). CONCLUSIONS: Atrial flutter can arise in the right atrial free wall. This form of atypical atrial flutter could account for spontaneous or inducible atrial flutter observed in patients referred for ablation and is eliminated with linear ablation directed at the inferolateral right atrium.

Effects of reperfusion on complete heart block complicating anterior myocardial infarction.

Two patients with complete heart block complicating extensive anterior myocardial infarction underwent late (greater than 40 hours) coronary reperfusion with angioplasty. One to one atrioventricular conduction was restored within minutes of reperfusion despite a lack of measurable ventricular muscle salvage as demonstrated by ventriculography 1 week later. The evidence favors reversible ischemia rather than extensive necrosis of the proximal conduction system as the mechanism of heart block in this subgroup of patients.

Immediate reproducibility of electrically induced sustained monomorphic ventricular tachycardia before and during antiarrhythmic therapy.

The immediate reproducibility of sustained ventricular tachycardia induction was evaluated prospectively during 106 studies performed in 53 patients with clinical sustained monomorphic ventricular tachycardia. Programmed electrical stimulation was performed twice, using the same protocol during 53 drug-free studies and 53 subsequent studies on antiarrhythmic therapy. Sustained monomorphic ventricular tachycardia was reproduced in 104 (98%) of the 106 studies. There was no significant difference in the incidence of reproducible tachycardia in the drug-free state compared with that observed during treatment with different classes of antiarrhythmic drugs. An increase in the number of extrastimuli was required to reinitiate the tachycardia in 9 (11%) of 83 studies in which single or double extrastimuli were initially required to induce the tachycardia. In 39 (37%) of 104 studies with reproducible tachycardia induction, the two tachycardias significantly differed in electrocardiographic (ECG) configuration and cycle length. These observations suggest that the overall reproducibility of ventricular tachycardia induction is sufficiently high to provide a reliable marker for evaluating the efficacy of therapeutic interventions. However, specific tachycardia characteristics such as cycle length and ECG configuration are more variable even within the same study and may be less useful in assessing the effects of subsequent interventions.

Incidence and determinants of multiple morphologically distinct sustained ventricular tachycardias.

The incidence and determinants of multiple morphologically distinct ventricular tachycardias were examined prospectively in 71 consecutive patients with at least one documented spontaneous episode of sustained monomorphic ventricular tachycardia. Mean frontal and horizontal QRS axes were determined from the 12 lead electrocardiograms (ECGs) of 190 spontaneous and 352 induced tachycardias. Two or more morphologically distinct spontaneous tachycardias were observed in 19 (43%) of 44 patients who had at least two documented spontaneous episodes. In 43 (61%) of the 71 patients, multiple morphologically distinct tachycardias were induced by programmed ventricular stimulation. Overall, 57 (80%) of the 71 patients had at least two morphologically distinct tachycardias. Predictors of multiple tachycardia configurations were selected by multivariate analysis from clinical and angiographic variables and were similar for both spontaneous and induced ventricular tachycardia: presence of multiple previous myocardial infarctions (p = 0.032 spontaneous, p = 0.005 induced) and number of different antiarrhythmic drug treatments during which ventricular tachycardia was documented (p = 0.0089 spontaneous, p less than 0.0001 induced). These data demonstrate that a large majority of patients with sustained monomorphic ventricular tachycardia exhibit more than one distinct QRS configuration when adequate ECG documentation of multiple episodes is obtained during different antiarrhythmic drug treatments. In individual patients, caution should be used in attributing clinical significance to a single unique QRS configuration.

A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification.

OBJECTIVES: The goal of this study was to compare T-wave alternans (TWA), signal-averaged electrocardiography (SAECG) and programmed ventricular stimulation (EPS) for arrhythmia risk stratification in patients undergoing electrophysiology study. BACKGROUND: Accurate identification of patients at increased risk for sustained ventricular arrhythmias is critical to prevent sudden cardiac death. T-wave alternans is a heart rate dependent measure of repolarization that correlates with arrhythmia vulnerability in animal and human studies. Signal-averaged electrocardiography and EPS are more established tests used for risk stratification. METHODS: This was a prospective, multicenter trial of 313 patients in sinus rhythm who were undergoing electrophysiologic study. T-wave alternans, assessed with bicycle ergometry, and SAECG were measured before EPS. The primary end point was sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation or appropriate implantable defibrillator (ICD) therapy, and the secondary end point was any of these arrhythmias or all-cause mortality. RESULTS: Kaplan-Meier survival analysis of the primary end point showed that TWA predicted events with a relative risk of 10.9, EPS had a relative risk of 7.1 and SAECG had a relative risk of 4.5. The relative risks for the secondary end point were 13.9, 4.7 and 3.3, respectively (p < 0.05). Multivariate analysis of 11 clinical parameters identified only TWA and EPS as independent predictors of events. In the prespecified subgroup with known or suspected ventricular arrhythmias, TWA predicted primary end points with a relative risk of 6.1 and secondary end points with a relative risk of 8.0. CONCLUSIONS: T-wave alternans is a strong independent predictor of spontaneous ventricular arrhythmias or death. It performed as well as programmed stimulation and better than SAECG in risk stratifying patients for life-threatening arrhythmias.

Catheter ablation of ventricular tachycardia in patients with structural heart disease using cooled radiofrequency energy: results of a prospective multicenter study. Cooled RF Multi Center Investigators Group.

OBJECTIVES: The purpose of this multicenter study was to evaluate the safety and efficacy of a radiofrequency (RF) catheter ablation system with internal saline irrigation. BACKGROUND: Catheter ablation of ventricular tachycardia (VT) associated with structural heart disease is more difficult than ablation of idiopathic VT. The larger size of responsible reentrant circuits contributes to the difficulty in achieving an adequate ablation lesion with conventional techniques. Recently, cooling of the ablation electrode by saline irrigation has been shown to increase RF lesion size. METHODS: The patient population included 146 patients who participated in the Cooled RF Ablation System clinical trial and underwent an attempt at ablation of VT occurring in the presence of structural heart disease. The duration of follow-up was 243 +/- 153 days. RESULTS: Catheter ablation was acutely successful, as defined by elimination of all mappable VTs, in 106 patients (75%). In 59 patients (41%), no VT of any type was inducible after ablation. Twelve patients (8%) experienced a major complication. After catheter ablation, 66 patients (46%) developed one or more episodes of a sustained ventricular arrhythmia. CONCLUSIONS: The results of this study demonstrate that catheter ablation of all mappable forms of sustained VT can be performed with high initial success and a moderate incidence of major complications (8%).

Local activation variability during monomorphic ventricular tachycardia in the dog.

OBJECTIVE: The aim was to determine the beat to beat variability in local activation time during sustained monomorphic ventricular tachycardia in a canine model of experimental myocardial infarction. METHODS: A digital template matching algorithm was developed for detecting subtle beat to beat variability in local activation timing at each of multiple ventricular sites. Ten electrically induced sustained ventricular tachycardia episodes, mean cycle length 211 (SD 40) ms, were endocardially and epicardially mapped in mongrel dogs weighing 15-20 kg. Digitised data were analysed for beat to beat local activation time variability. Similar data recorded during ventricular pacing at comparable rates and during sinus rhythm served as controls. RESULTS: The overall mean variability of local activation time for all 10 ventricular tachycardias was 3.2(1.6) ms, range 1.8(1.1) ms to 4.7(2.8) ms, in contrast to the overall mean variability of 0.2(0.4) ms (p = 0.0001) for ventricular pacing and 0.7(0.6) ms (p = 0.0001) for sinus rhythm. Oscillations in local activation time manifested alternans type periodicity during seven of 10 ventricular tachycardias independent of any alternans in local electrogram morphology. CONCLUSIONS: During sustained, monomorphic ventricular tachycardia, beat to beat variability and alternans type oscillations in local activation time are common and may be an intrinsic property of re-entry since they are negligibly small during ventricular pacing.

The mode selection trial (MOST) in sinus node dysfunction: design, rationale, and baseline characteristics of the first 1000 patients.

BACKGROUND: More than 200,000 permanent pacemakers will be implanted in the United States in 2000 at a cost of more than $2 billion. Sick sinus syndrome (SSS) will likely account for approximately half of all cases necessitating implantation. Pacemaker technology permits the selection of ventricular (single-chamber) or dual-chamber devices. However, clinical and outcomes data are inadequate to support a clear recommendation that one or the other type of device be used. METHODS: The Mode Selection Trial (MOST) is a single-blind study supported by the National Heart, Lung, and Blood Institute designed to enroll 2000 patients with SSS. All patients will receive a DDDR pacemaker programmed to VVIR or DDDR before implantation. The average time of follow-up will be 3 years. MOST has a >90% power to detect a 25% reduction in the primary end point-nonfatal stroke or total (all cause) mortality-in the DDDR-treated group. Secondary end points will include health-related quality of life and cost effectiveness, atrial fibrillation, and development of pacemaker syndrome. Prespecified subgroups for analysis will include women and the elderly. Enrollment was completed in October 1999, with a total of 2010 patients. RESULTS: The median age of the first 1000 enrolled patients is 74 years, with 25% of patients 80 years or older. Women comprise 49%, and 17% are nonwhite, predominantly black (13%). Before pacemaker implantation, 22% of patients reported a history of congestive heart failure, 11% coronary angioplasty, and 25% coronary bypass surgery. Supraventricular tachycardia including atrial fibrillation was present in 53% of patients. A prior stroke was reported by 12%. Antiarrhythmic therapy was in use in 18% of patients. CONCLUSIONS: MOST will fill the clinical need for carefully designed prospective studies to define the benefits of dual-chamber versus single-chamber ventricular pacing in patients with SSS. The MOST population is typical of the overall pacemaker population in the United States. Thus the final results of MOST should be clinically generalizable.

What can we expect from prophylactic implantable defibrillators?

Death due to ventricular tachyarrhythmia (VT) remains an important public health problem; patients with prior myocardial infarction (MI) constitute the largest identifiable population for prophylactic interventions. Targeting of progressively higher-risk subgroups of post-MI survivors carries inevitable tradeoffs with respect to the global impact of interventions on overall mortality. Therapy with aspirin, beta blockers, and angiotensin-converting enzyme (ACE) inhibitors comprise the benchmark against which all additional interventions, including implantable defibrillators, must be measured. Initial enthusiasm for empiric amiodarone therapy has been tempered by the limited benefit demonstrated in recent randomized trials. Trials of other class III antiarrhythmic drugs, including both d,l-sotalol and d-sotalol, have also failed to demonstrate survival benefit. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) demonstrated significantly improved survival associated with defibrillators in a small subgroup of post-MI survivors with a high short-term risk of death. The ultimate number and optimal criteria for selection of patients who may benefit from prophylactic defibrillator therapy after MI will undergo continued evolution as new data from current and ongoing trials become available.

Limitations of adenosine in assessing the efficacy of radiofrequency catheter ablation of accessory pathways.

Adenosine has been shown to reliably confirm the success of accessory pathway catheter ablation by producing transient atrioventricular (AV) block during atrial and ventricular pacing. This is due to the insensitivity of accessory pathway conduction to adenosine (with the rare exception of accessory pathways with decremental conduction properties). However, 4 of 204 consecutive patients who underwent successful accessory pathway ablation (as shown by adenosine-induced transient AV block) had recurrent AV reciprocating tachycardia involving a second, previously nonmanifest accessory pathway. In each case, the second accessory pathway was localized to a site disparate from the original pathway. No pathway showed decremental anterograde or retrograde conduction properties. In 2 patients, adenosine initially did not show the presence of the second concealed accessory pathway, because the refractory period of the accessory pathway was longer than the pacing cycle length used to assess ventriculoatrial conduction. Only when the refractory period of this second accessory pathway was shortened by infusion of isoproterenol did adenosine reveal the presence of the pathway during follow-up electrophysiologic study. In another patient, a non-decremental accessory pathway was shown to be sensitive to adenosine. In the remaining patient, the second accessory pathway may have been transiently injured during the initial study, thereby simulating adenosine sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of multiple patches during implantation of epicardial defibrillator systems.

During implantation of epicardial automatic defibrillator systems, occasional patients have difficulty in obtaining adequate defibrillation thresholds. Of 236 consecutive patients undergoing implantation of epicardial defibrillator systems, 18 patients received a 3-patch (n = 15) or 4-patch (n = 3) defibrillator system. Twelve patients who received a multiple-patch defibrillator system had a best 2-patch defibrillation energy requirement of > or = 30 J; in the remaining 6 patients less stringent clinical criteria were used in the decision to add a third defibrillator patch (defibrillation energy requirement > 18 J in 4 patients, and > 20 J in 2 patients). Technically, multiple-patch systems were made possible with either the use of Y-connectors or defibrillators allowing output to 3 patches. In 3 patients, addition of a third epicardial patch still resulted in a defibrillation energy requirement of > or = 30 J; in these 3 patients, addition of a fourth patch resulted in a defibrillation energy requirement of < or = 20 J. All patients receiving a multiple-patch defibrillator system had a reduction in defibrillation energy requirement, and 12 patients had a reduction in defibrillation energy requirement of > or = 10 J over the best 2-patch defibrillation energy requirement. In the patients who eventually had placement of a multiple-patch system, the best 2-patch defibrillation energy requirement was > 18 J in 4 patients, > 20 J in 2 patients, > or = 30 J in 9 patients, and > 40 J in 3 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effectiveness of radiofrequency catheter ablation for treatment of atrial tachycardia.

Catheter ablation has been used to treat atrioventricular node reentrant and atrioventricular reentrant tachycardias with extremely high success rates. The suitability of catheter ablation for treatment of atrial tachycardia, a much less common type of supraventricular tachycardia, has not been well addressed. Fifteen patients (8 females) ranging from 10 to 83 years (mean 38 +/- 22) were referred for catheter ablation of supraventricular tachycardia. The diagnosis of atrial tachycardia was established by standard electrophysiologic techniques. A combination of activation and pace mapping was used to identify a suitable site for radiofrequency current catheter ablation. Medical therapy was unsuccessful in all but 1 patient. Two patients had surgically corrected congenital heart disease, 2 had coronary artery disease and 1 had dilated cardiomyopathy. Seven patients had depressed left ventricular function. Six patients had incessant tachycardias. Presumed tachycardia mechanism was automatic in 11 patients and reentrant in 4. Mean tachycardia cycle length was 372 +/- 74 ms. Catheter ablation was acutely successful in 12 patients (80%) with application of 11.1 +/- 6.6 lesions at a mean voltage of 60 +/- 9 V. In the other 3 patients, 16 to 38 lesions were applied. At a mean follow-up of 18.5 +/- 6.5 months, 2 patients have had recurrences with different P-wave morphologies and underwent a second successful catheter ablation procedure. An additional 2 patients had recurrences with the same P-wave morphology and 1 underwent a second successful catheter ablation procedure. Thus, radiofrequency ablation can be used in a diverse population of patients with atrial tachycardia with an acute success rate of 80% and a long-term success rate of 73%.

Retrograde fast pathway ablation for atrioventricular nodal reentry associated with markedly prolonged PR intervals.

Three patients with typical atrioventricular nodal reentrant tachycardia (AVNRT) and markedly prolonged PR intervals (>300 ms) without dual pathway physiology at baseline or during isoproterenol infusion underwent successful fast pathway ablation and remained asymptomatic without recurrent AVNRT, atrioventricular block, or symptomatic bradycardia for a mean of 19 months. In patients with recurrent AVNRT and markedly prolonged PR intervals, selective ablation of the retrograde fast pathway can eliminate AVNRT without further impairment of anterograde atrioventricular nodal function.

Current-based transthoracic defibrillation.

This study examines in a prospective, multicenter trial the feasibility and advantage of current-based, transthoracic defibrillation. Current-based, damped, sinusoidal waveform shocks of 18, 25, 30, 35, or 40 amperes (A) were administered beginning with 25 A for polymorphic ventricular tachycardia (VT) and ventricular fibrillation (VF) or 18 A for monomorphic VT; success rates were compared with those of energy-based shocks beginning at 200 J for VF/polymorphic VT and 100 J for VT. The current-based shocks were delivered from custom-modified defibrillators that determined impedance in advance of any shock using a "test-pulse" technique; the capacitor then charged to the exact energy necessary to deliver the operator-selected current against the impedance determined by the defibrillator. Three hundred sixty-two patients received > 1 shock for VF, polymorphic VT, or monomorphic VT: 569 current- based shocks and 420 energy-based shocks. Current-based shocks of 35/40 A achieved success rates of up to 74% for VF/polymorphic VT; 30 A shocks terminated 88% of monomorphic VT episodes. Energy-based shocks of 300 J terminated 72% of VF/polymorphic VT; 200-J shocks terminated 89% of monomorphic VT. We could not demonstrate a significant increase in the success rate of current-based shocks over energy-based shocks for patients with high transthoracic impedance; this may be due to inadequate sample size. Thus, current-based defibrillation is clinically feasible and effective. A larger study will be needed to test whether current-based defibrillation is superior to energy-based defibrillation.

Nonthoracotomy lead system for implantable defibrillator.

Over a 2-year period, 110 patients underwent attempted implantation of an automatic cardioverter-defibrillator using the nonthoracotomy lead system. Indications included sustained monomorphic ventricular (n = 62), nonsustained with poor ventricular function (n = 7), ventricular fibrillation (n = 21), ventricular tachycardia/fibrillation (n = 18), and familial long QT syndrome (n = 2). There were 90 male and 20 female patients. Mean age was 57 +/- 15 years. Sixty percent had previous coronary bypass or valve operations, or both. Mean left ventricular ejection fraction was 30% +/- 14%, cardiac index was 2.4 +/- 0.9 L/m2, and systolic pulmonary artery pressure was 41 +/- 14 mm Hg. Under general anesthesia, the nonthoracotomy lead was introduced through the left subclavian vein. The subcutaneous patch and generator were placed posteriorly on the serratus muscle and left upper quadrant, respectively. The length of the procedure was 116 +/- 44 minutes and the mean number of defibrillation shocks for a successful implant was 8 +/- 4. Eighty-five patients (77%) had successful implantations. Failures were due to high defibrillation threshold (n = 23) and inability to place a right ventricular lead (n = 2). Predictors of failure included preoperative antiarrhythmic drugs and cardiac index of 1.8 +/- 4 L/m2 or less (p = 0.004). Three patients (2.7%) died after the operation of heart failure (n = 2) and chronic heart transplant rejection (n = 1). Complications included lead migration or dislodgment (n = 8), infection (n = 1), and hematoma (n = 3). In summary, the nonthoracotomy lead system may provide an alternative in patients undergoing cardioverter-defibrillator implantation.

Prognostic significance of sustained ventricular tachyarrhythmia occurring during dobutamine infusion.

The prognostic significance of a de novo sustained ventricular tachyarrhythmia occurring during a dobutamine infusion is unknown. This study was performed to determine (1) the risk of recurrent ventricular arrhythmia, (2) the safety of future dobutamine infusions, and (3) the role of electrophysiologic testing. The study population consisted of 15 patients, six with coronary artery disease, and nine with idiopathic dilated cardiomyopathy. Mean ejection fraction was 17% +/- 4.1%. The arrhythmia during the infusion was ventricular tachycardia in 13 patients and ventricular fibrillation in two patients and was not associated with preceding hemodynamic instability, electrolyte abnormality, digoxin toxicity, or antiarrhythmic drug therapy. During electrophysiologic testing, 7 of 15 patients had inducible ventricular tachycardia. All patients with inducible ventricular tachycardia were treated with either antiarrhythmic drugs, defibrillators, or ablation. Over a 12.3 +/- 5.2 month follow-up period, all 15 patients received further dobutamine treatment. Seven of 15 (47%) had a recurrent sustained ventricular tachyarrhythmia. Although three of seven recurrences occurred during a dobutamine infusion, all three of these patients had hemodynamically unstable conditions and were receiving high-dose (> 10 micrograms/kg/min) therapy at the time of recurrence. The other four recurrent arrhythmias were not associated with clear precipitating factors. Ejection fraction, origin of left ventricular dysfunction, and inducibility at baseline electrophysiologic testing did not predict arrhythmia recurrence. The de novo occurrence of a sustained ventricular tachyarrhythmia during dobutamine infusion is associated with a significant risk of arrhythmia recurrence (47%), which can occur in the presence or absence of dobutamine therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Median sternotomy for implantable cardioverter/defibrillator.

The automatic implantable cardioverter/defibrillator is an accepted mode of therapy for medically refractory sustained ventricular tachycardia or fibrillation. At the Loyola University Medical Center, Maywood, Ill, 39 implantations were performed in a 14-month period. The method of implantation was the median sternotomy. Our population included 9 patients in whom sternotomies had to be redone and 17 patients with concomitant revascularization. Two patients died due to pump failure, and one major complication (infection) occurred that was directly related to the automatic implantable cardioverter/defibrillator. The median sternotomy, because of good results, continues to be our method of choice for insertion of the automatic implantable cardioverter/defibrillator.

Surgical ablation for idiopathic ventricular tachycardia.

A 33-year-old man with a right-bundle branch, left-axis deviation ventricular tachycardia was medically treated unsuccessfully. Surgical mapping and ablation was performed with a successful surgical result. A discussion of surgical results for this problem is provided.

Electrophysiologic effects of prazosin during acute myocardial ischemia.

Prazosin, 100 micrograms/kg, had no effect on baseline refractoriness or intraventricular conduction in anesthetized dogs. During 1 h of coronary artery occlusion followed by reperfusion, prazosin significantly blunted the shortening of the ventricular effective refractory periods within ischemic myocardial region relative to vehicle-treated animals. Prazosin treatment also prevented the delayed conduction of paced ventricular complexes entering and exiting the ischemic zone. These effects may be associated with the blockade of alpha 1-adrenoceptor activation during the acute phase of myocardial ischemia.