Effects of quinidine and amiodarone on blood pressure during rapid ventricular pacing in coronary artery disease.
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Aged↗
Biomedical subjects
A Kadish
Publications and source records attributed to A Kadish.
Effect of epinephrine on the efficacy of the internal cardioverter-defibrillator.
To evaluate the effect of sympathetic activation on the efficacy of the implantable cardioverter-defibrillator (ICD) in converting ventricular tachycardia (VT) or ventricular fibrillation (VF), 32 patients who received an ICD because of life-threatening VT/VF underwent 1 week postimplant ICD testing both before and after infusion of 25 (16 patients) or 50 (16 patients) ng/kg/min of epinephrine for greater than or equal to 12 minutes. These infusion rates are known to result in plasma epinephrine concentrations comparable to mild-moderate stress. The patients' mean age was 63 +/- 10 years; 26 had coronary artery disease, 2 had dilated cardiomyopathy and 4 had no evidence of structural heart disease. VT and VF were induced in 16 patients each by programmed stimulation or alternating current. Among the 16 patients with VT, the first ICD discharge (26 to 30 J) was effective in 15 patients in the baseline state and in all 16 patients during epinephrine infusion. Among patients with VF, the first ICD discharge (26 to 30 J) terminated VF in all patients in the baseline state, compared with 12 of 16 patients during epinephrine infusion (p less than 0.05). In 4 patients, VF was terminated during epinephrine infusion only by the second or third ICD discharge (30 J). In conclusion, physiologic increases in the plasma epinephrine concentration may increase the number and energy of shocks needed to terminate VF.
Aged↗
Outcome of endocardial resection in 33 patients with coronary artery disease: correlation with ventricular tachycardia morphology.
The results in 33 patients with ventricular tachycardia (VT) treated by endocardial resection were reviewed, with special emphasis on the presence of single or multiple morphologies preoperatively and intraoperatively. Multiple VT morphologies were induced in 16 patients and a single VT morphology was induced in the remaining 17. Intraoperative programmed stimulation failed to induce VT in eight patients and visually-directed endocardial resection was performed. The remaining patients underwent map-guided resection. The surgical success rate did not correlate with any morphologic characteristics of the VT, such as bundle branch block pattern or axis. In addition, concordance of VT morphologies preoperatively and intraoperatively before resection did not correlate with the surgical success rate. However, patients in whom multiple morphologies of VT were induced intraoperatively had a significantly higher success rate (100%) compared with those patients in whom only a single morphology was induced intraoperatively (50%, p < 0.05). Long-term follow-up was maintained in 26 patients. Ventricular tachycardia recurred in two patients and VF recurred in two others who did not have inducible VT 1 week after endocardial resection. In conclusion, neither the preoperative morphologic characteristics of VT nor discordance between the morphologies of VT induced preoperatively and in the operating room influenced the outcome of endocardial resection. However, the surgical success rate is higher when multiple morphologies of VT are inducible in the operating room than when only one VT morphology is inducible.
Adult↗
A comparison of standard and high-dose regimens for the initiation of amiodarone therapy.
The effects of two regimens for the initiation of amiodarone therapy were compared in 92 patients with inducible sustained ventricular tachycardia (VT) at baseline electrophysiologic testing. Two groups of 46 patients each received a total of 16.8 gm of oral amiodarone before follow-up electrophysiologic testing. Group A (standard dose) received 1200 mg/day for 14 days, and group B (high dose) received 2400 mg/day for 7 days. Amiodarone suppressed the induction of sustained VT in six subjects (13%) in group A versus 10 (22%) in group B (p = NS). In subjects who continued to have inducible VT after amiodarone loading, the mean increase in cycle length of induced VT was similar in group A (delta = 85 +/- 73 msec) and group B (delta = 78 +/- 59 msec). The mean increase in sinus cycle length, AH and HV intervals, paced QRS duration, and ventricular refractory periods was also not significantly different between the two groups. Side effects developed in 10 (22%) patients in group B but were serious only in one, and one patient required a reduction in dosage. Thus compared to the 14-day standard-dose regimen, the 7-day high-dose regimen was well tolerated and had similar effects on VT inducibility and electrophysiologic variables. Its use may significantly shorten the duration of hospitalization in patients with life-threatening inducible VT who are undergoing loading with amiodarone on an inpatient basis.
Aged↗
Local heat and cold application after eastern cottonmouth moccasin (Agkistrodon piscivorus) envenomation in the rat: effect on tissue injury.
We studied the effect of local application of heat or cold on the development of tissue necrosis in envenomated rats. Anesthetized animals had 6 mg/kg venom from Agkistrodon piscivorus injected subcutaneously into the lateral aspect of a hind limb. Heat or cold was applied to the site of envenomation in the experimental groups for 4-6 hr, and the injected area was examined histologically after 24 hr. Neither local treatment, with or without the presence of systemic antivenin, significantly affected the severity of tissue necrosis induced by the venom in comparison to a control group left at ambient temperature.
Animals↗
Reversal of antiarrhythmic drug effects by epinephrine: quinidine versus amiodarone.
Although previous studies have demonstrated that the electrophysiologic effects of many antiarrhythmic agents can be reversed by catecholamines, the susceptibility of amiodarone to such reversal is unknown. The objective of this study was to compare the relative degree of reversal of the electrophysiologic effects of quinidine and amiodarone by epinephrine infusions that result in plasma epinephrine levels similar to those achieved during various physiologic stresses. Twenty-nine patients who had inducible sustained monomorphic ventricular tachycardia and underwent electropharmacologic testing with quinidine and amiodarone were enrolled in the study. The variables measured before and during an epinephrine infusion (25 or 50 ng/kg per min) included the sinus cycle length, mean arterial pressure, QT interval and effective refractory period at drive train cycle lengths of 600 and 400 ms. The effective refractory period measured at a drive train cycle length of 600 ms shortened less during amiodarone therapy (2 +/- 2%) than during quinidine therapy (6 +/- 4%) or than in the baseline state (6 +/- 4%; p less than 0.01). Similar results were obtained during evaluation of the effective refractory period at a cycle length of 400 ms. Epinephrine infusion, at both 25 and 50 ng/kg per min, completely reversed the effects of quinidine and partially reversed the effects of amiodarone on the effective refractory period. The effects of epinephrine on the sinus cycle length and QT interval were similar in the baseline state and in conjunction with quinidine and amiodarone. Twenty-four patients underwent programmed ventricular stimulation during amiodarone therapy alone and in conjunction with either a 25- or a 50-ng/kg per min infusion of epinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)
Amiodarone↗
Physiology of "atypical" atrioventricular junctional reentrant tachycardia occurring following radiofrequency catheter modification of the atrioventricular node.
The physiology of atypical atrioventricular junctional reentrant tachycardia (AVJRT) occurring following catheter modification of the AV node is poorly defined. Six patients undergoing radiofrequency current catheter modification of the AV node had inducible atypical AVJRT before or after AV nodal modification. Typical AVJRT was differentiated from atypical AVJRT by a ventriculoatrial (VA) time < 60 msec in the His-bundle electrogram recording. Five of six patients had typical AVJRT and two had atypical AVJRT prior to AV nodal modification. Following anterior approach AV nodal modification, previously undetected atypical AVJRT was induced in four patients. Earliest retrograde atrial activation in the posterior septum was documented in all patients with atypical AVJRT prior to modification and in three of four patients with atypical AVJRT following modification. The AH intervals during tachycardia were 320 +/- 52 msec in typical AVJRT, 88 +/- 33 msec in the premodification atypical AVJRTs, and 172 +/- 12 msec in the postmodification atypical AVJRTs (P = 0.0001). The AH/HA ratios were 4.1 +/- 0.9 in typical AVJRT, 0.5 +/- 0.2 in the premodification atypical AVJRTs, and 0.9 +/- 0.2 in the postmodification atypical AVJRTs (P = 0.0001). Two patients with postmodification atypical AVJRT underwent further posterior approach AV node modification that resulted in VA block. One patient with postmodification atypical AVJRT had further anterior approach AV nodal modification that resulted in heart block. The retrograde limb of the atypical AVJRT seen following anterior approach AV nodal modification is a posterior, slow pathway.
Atrioventricular Node↗
Electrogram criteria for identification of appropriate target sites for radiofrequency catheter ablation of accessory atrioventricular connections.
BACKGROUND: Catheter ablation of accessory atrioventricular (AV) connections using radiofrequency current has been demonstrated to be effective in the majority of patients with the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardia involving a concealed accessory AV connection. However, electrogram criteria have not been established to guide attempts at radiofrequency catheter ablation. METHODS AND RESULTS: The characteristics of local electrograms recorded at successful and unsuccessful sites of radiofrequency catheter ablation were determined in 132 patients. Electrograms recorded at a total of 438 sites were analyzed: 338 recorded during ablation of 90 manifest accessory AV connections and 100 recorded during ablation of 44 concealed accessory AV connections. During ablation of manifest accessory AV connections, the independent predictors of outcome were electrogram stability (p less than 0.001), the interval between activation of the ventricular electrogram and onset of the QRS complex (p less than 0.001), and the presence of an accessory AV connection potential (p less than 0.001). Radiofrequency energy delivery at sites demonstrating stable electrograms, a probable or possible accessory AV connection potential, and activation of the local ventrical electrogram before the onset of the QRS complex had a 57% probability of success compared with a 3% probability of success at sites without these features. During ablation of concealed accessory AV connections, the independent predictors of outcome were electrogram stability (p = 0.02), the presence of an accessory AV connection potential (p = 0.05), and the presence of retrograde continuous electrical activity (p = 0.04). Sites demonstrating a stable local electrogram, an accessory AV connection potential, and retrograde continuous electrical activity had an 82% probability of success compared with only a 5% probability of success at sites demonstrating none of these features. CONCLUSIONS: The local electrogram parameters of greatest importance in predicting the success or failure of radiofrequency catheter ablation of accessory AV connections are electrogram stability, the presence of an accessory AV connection potential, and the timing of ventricular activation relative to the QRS complex (for manifest accessory AV connections) or retrograde continuous electrical activity (for concealed accessory AV connections). Awareness of these variables during attempts at radiofrequency catheter ablation of accessory AV connections may minimize the number of unnecessary applications of radiofrequency energy.
Adult↗
A randomized comparison of external and internal cardioversion of chronic atrial fibrillation.
BACKGROUND: Delivery of shocks within the right atrium has been reported to be more effective than conventional external shocks in converting atrial fibrillation (AF), but these two cardioversion techniques have never been compared prospectively. The purpose of this study was to compare the efficacies of external and internal cardioversion in patients with chronic AF unresponsive to prior attempts at electrical and/or pharmacological cardioversion. Low-dose amiodarone was used in all patients after cardioversion to suppress recurrences of AF. METHODS AND RESULTS: One hundred twelve patients with AF of at least 1 month in duration were randomly assigned to undergo external cardioversion with 300-360-J shocks or internal cardioversion with 200-300-J shocks delivered through a standard electrode catheter within the right atrium. The patients were treated with amiodarone (200 mg/day 5-7 days/week) for 1 month before electrical cardioversion and afterward if the cardioversion was successful. The patients were evaluated at regular intervals during 1 year of follow-up. The efficacy of internal cardioversion was significantly greater than that of external cardioversion (91% versus 67%, p = 0.002). The only variable that was associated with the outcome of cardioversion was body weight. Among patients in whom sinus rhythm was restored, AF recurred as often after internal and external cardioversion; at 1 year of follow-up, 37% of patients in whom external or internal cardioversion had been effective were still in sinus rhythm. Patients who had undergone an attempt at electrical cardioversion before entry into this study were less likely to remain in sinus rhythm after cardioversion. The only complications of cardioversion were one instance of cerebral thromboembolism after external cardioversion and one instance of transient pulmonary edema after internal cardioversion. Therapy with amiodarone was discontinued because of an adverse drug effect in only three patients. CONCLUSIONS: Internal cardioversion is more effective than external cardioversion in restoring sinus rhythm and is as safe as external cardioversion in patients with chronic AF. The recurrence rate of AF is the same after both types of cardioversion. If conventional electrical cardioversion is ineffective, internal cardioversion should be attempted. The combination of low-dose amiodarone and external or internal cardioversion may result in maintaining sinus rhythm long-term in patients with refractory AF.
Amiodarone↗
Epicardial controlled-release verapamil prevents ventricular tachycardia episodes induced by acute ischemia in a canine model.
Sustained-release preparations composed of verapamil-polymeric controlled-release matrices were characterized in vitro and utilized as epicardial implants in dogs with ischemic ventricular arrhythmias. Anesthetized open-chest dogs were subjected to 5 hourly, 10-min complete occlusions of the left anterior descending coronary artery followed by reperfusion. A controlled-release matrix preparation (20% verapamil, 80% polyurethane), placed on the left ventricular epicardium prior to the third occlusion, resulted in successful inhibition of ventricular tachycardia (VT) during acute ischemia in a dose-dependent manner. The largest matrix size used, 300 mg (20% verapamil), provided a net systemic dose of 0.52 +/- 0.18 mg/kg over 140 min and significantly reduced VT episodes during acute ischemia (fifth occlusion) compared to untreated controls (0.16 +/- 0.04 vs. 1.01 +/- 0.35 episodes/min, respectively; t = 2.62, p = 0.01). In controls, by the fifth occlusion ventricular fibrillation (VF) occurred after 5.41 +/- 0.78 min in 89% of animals. However, after a 300-mg verapamil matrix was placed on the left ventricular ischemic zone, VF occurred in only 45% (chi-squared = 4.1, p = 0.04, vs. controls) of the animals after 7.87 +/- 0.92 min (fifth occlusion). Systemic venous plasma verapamil levels during the 2 h following the 300-mg matrix ischemic zone implantation ranged from 8.4-22.0 ng/ml, while simultaneous regional coronary venous levels were 125.0-387.0 ng/ml. Sonomicrometry studies of left ventricular wall thickening carried out with a series of 300-mg verapamil matrix cardiac implants did not demonstrate any significant myocardial dysfunction. It is concluded that controlled-release verapamil, administered directly to the heart, was effective for preventing VT and VF associated with acute coronary ischemia, and that this route of administration was not associated with any significant deterioration of cardiac function.
Animals↗
Concealed entrainment as a guide for catheter ablation of ventricular tachycardia in patients with prior myocardial infarction.
Fifteen consecutive patients with drug-refractory, recurrent, sustained, monomorphic ventricular tachycardia and a history of remote myocardial infarction underwent catheter ablation of ventricular tachycardia. Shocks of 100 to 300 J were delivered to sites at which pacing during ventricular tachycardia resulted in concealed entrainment, in which the ventricular tachycardia accelerated to the pacing rate, there was a long stimulus to QRS interval and there was no change in the configuration of the QRS complex during pacing at several rates compared with the configuration during ventricular tachycardia, thus identifying a zone of slow conduction in the reentrant circuit. Concealed entrainment was demonstrated in nine (60%) of 15 patients, and the stimulus to QRS intervals were 90 to 400 ms. At sites of concealed entrainment, the endocardial activation time relative to the QRS complex during ventricular tachycardia ranged from -125 to +50 ms, the timing of the local electrogram relative to the QRS complex was the same during entrainment as during ventricular tachycardia and the pace map during sinus rhythm was discordant with that of the ventricular tachycardia in seven patients. In the six patients in whom a site of concealed entrainment could not be identified, the target site for ablation was selected on the basis of identification of an isolated mid-diastolic potential, activation mapping and pace mapping. The mean (+/- SD) cumulative number of joules delivered to the target site was 306 +/- 140. A successful long-term clinical outcome was achieved in 9 of the 15 patients (mean follow-up 20 +/- 7 months). The clinical success rate was the same whether the target site was selected on the basis of concealed entrainment (five of nine, 56%) or on the basis of the other mapping techniques (four of six, 67%). In conclusion, the responses to pacing suggest that sites at which there is concealed entrainment may be located within a zone of slow conduction in the ventricular tachycardia reentry circuit, although not necessarily in an area critical for the maintenance of reentry. The long-term clinical efficacy of catheter ablation targeted to sites of concealed entrainment is about 60%, similar to the results achieved when conventional mapping techniques are used.
Aged↗
Comparison of responses to isoproterenol and epinephrine during head-up tilt in suspected vasodepressor syncope.
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Bradycardia↗
Results of electrophysiologic testing and long-term prognosis in patients with coronary artery disease and aborted sudden death.
The purpose of this study was to evaluate the results of electrophysiologic testing and the long-term prognosis of 56 patients with coronary artery disease who presented with aborted sudden death unrelated to acute myocardial infarction. The mean age of the patients was 62 +/- 8 years (+/- standard deviation) and 48 were men. The mean left ventricular ejection fraction was 0.34 +/- 0.16. During the baseline electrophysiology test, sustained monomorphic ventricular tachycardia (VT) was inducible in 22 patients who then underwent electropharmacologic testing: 11 patients were treated with antiarrhythmic drugs that suppressed the induction of VT or resulted in the VT becoming hemodynamically stable; 10 patients who failed drug testing received an automatic implantable cardioverter/defibrillator (AICD); one patient underwent endocardial resection. Among 34 patients who did not have inducible sustained VT, a precipitant of cardiac arrest (severe ischemia, proarrhythmia) was identified and was corrected in 9 of 34. An AICD was recommended in the remaining 25 patients; however, nine patients refused and were treated empirically with antiarrhythmic drugs. The mean follow-up was 22 +/- 12 months. The 2-year actuarial incidence of sudden death was 31% in patients who were treated with drugs based on the results of electropharmacologic testing, 26% in patients who were treated with antiarrhythmic drugs on an empiric basis, 0% among patients in whom a correctable etiology for the cardiac arrest was identified, and 9% among patients who underwent implantation of an AICD. The 3-year actuarial incidence of sudden death among the 20 patients treated with antiarrhythmic drugs was 53%, compared with 9% among the 26 patients who underwent AICD implantation (p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)
Actuarial Analysis↗
Current treatment for Wolff-Parkinson-White syndrome: results and surgical implications.
From July 1986 to January 1991, 123 patients with Wolff-Parkinson-White syndrome underwent operation for ablation of aberrant conduction pathways. There were 85 male and 38 female patients ranging in age from 11 months to 68 years. Associated anomalies included Ebstein's anomaly, sudden death syndrome, coronary artery disease, cardiomyopathy, abdominal aortic aneurysm, neurofibromatosis, other arrhythmias, or other complex congenital heart disease. Forty-one patients had multiple accessory pathways. Operative results showed a 7% initial failure rate, which dropped to 3% after reoperation. One patient had undergone previous operation for Wolff-Parkinson-White syndrome at another institution. Procedures performed concomitantly included mitral or tricuspid valve repair or replacement (6), right ventricular conduit replacement, subaortic resection, Fontan repair, corrected transposition repair, coronary artery bypass, and placement of an automatic internal cardioverter defibrillator. There was no operative mortality. Late follow-up is 27 +/- 16 months, and complications included mitral regurgitation and myocardial infarction. By comparison, in the last 12 months 124 patients with the Wolff-Parkinson-White syndrome underwent catheter ablation using radiofrequency current. There were 9 patients with multiple pathways. One hundred twelve patients (90%) had all accessory atrioventricular connections ablated and have remained free of symptomatic tachycardia. There have been 12 failures (10%), of which 5 have had operation and 7 are being treated medically. Mean follow-up is 7 +/- 5 months, and complications included circumflex coronary artery occlusion, excessive bleeding, valve perforation, and cerebral vascular accident.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Monophasic action potential duration during programmed electrical stimulation.
UNLABELLED: To examine changes in monophasic action potential duration (APD) with a pacing protocol similar to that used during electrophysiological testing, action potentials were recorded in vivo from the left ventricular apical endocardium of 12 normal mongrel dogs. The atrioventricular node was ablated and the dogs paced from the anterior right ventricle at a baseline cycle length of 1000 ms between interventions. Mean steady-state APD (APDss) was 266 +/- 7 ms at a pacing cycle length (PCL) of 1000 ms. Two pacing protocols were used. The first consisted of a sudden acceleration in pacing from a cycle length of 1000 ms to one between 300 and 600 ms. The second consisted of an 8-beat train at a cycle length of 400 ms followed by a premature beat at a coupling interval of 280 ms followed by a pause. The inter-train pause varied between 1 second and 32 seconds. With a sudden acceleration in pacing rate, steady-state values for APD at the faster PCLs were significantly smaller than APDss at 1000 ms with a change to cycle lengths of 600 ms (247 +/- 29 ms), 500 ms (229 +/- 21 ms), 400 ms (220 +/- 17 ms), and 300 ms (203 +/- 31 ms; P less than 0.01 for all comparisons). The time constant of the change in APD was shorter at a PCL of 300 ms (14.9 +/- 0.8 s) than 600 ms (20.3 +/- 4.7 s; P less than 0.05). With drive train pacing and incorporating an inter-train pause, the percent drop in steady-state APD compared to APD for the first train ranged from 10.1% with a 1-second inter-train pause to 2.1% with a 32-second pause. The difference in APD between the first drive train and drive trains after at least 3 minutes of pacing when APD had stabilized was not significant for an inter-train pause exceeding 8 seconds. IN CONCLUSION: (1) with a sudden acceleration in pacing rate, endocardial APD in vivo decreases exponentially. The faster the new rate, the shorter the new steady-state APD and the shorter the time constant. (2) When pacing using an 8-beat drive train and an inter-train pause, there is a decremental shortening in APD for pause lengths shorter than 16 seconds. Thus, while performing programmed stimulation using a pause, a conditioning period of at least 2 minutes should be used prior to diastole scanning to allow APD to achieve a steady state.
Action Potentials↗
Prospective comparison of a conventional and an accelerated protocol for programmed ventricular stimulation in patients with coronary artery disease.
BACKGROUND: This study compared the sensitivity, specificity, and efficiency of a "conventional" and "accelerated" programmed stimulation protocol in 293 patients with coronary artery disease who had a history of sustained or nonsustained monomorphic ventricular tachycardia (VT). METHODS AND RESULTS: In the conventional protocol, one and two extrastimuli were introduced during sinus rhythm and during basic drive trains at cycle lengths of 600 and 400 msec at the right ventricular apex and then at the outflow tract or septum. In the accelerated protocol, one, two, and then three extrastimuli were introduced at each of three basic drive train cycle lengths (350, 400, and 600 msec) at the right ventricular apex; the procedure was repeated at a second right ventricular site. Six hundred thirty-four electrophysiological tests were performed using one of these two protocols either in the baseline state (293 tests) or during drug testing (341 tests). The yield of sustained, monomorphic VT was 89% with the conventional protocol and 92% with the accelerated protocol during baseline tests in patients who had a history of sustained VT (p = 0.05); 20% and 34%, respectively, during baseline tests in patients with a history of nonsustained VT (p = 0.06); and 70% and 77%, respectively, during drug testing (p = 0.2). To induce sustained, monomorphic VT, 10.1 +/- 5.0 (mean +/- SD) protocol steps and 14.4 +/- 8.7 minutes were required with the conventional protocol, compared with 4.0 +/- 3.7 steps and 5.6 +/- 6.1 minutes with the accelerated protocol (p less than 0.001 for each comparison). Among the tests in which sustained, monomorphic VT was induced, sustained polymorphic VT or ventricular fibrillation was induced more often with the conventional protocol (3.6%) than with the accelerated protocol (0.9%, p = 0.05). CONCLUSIONS: The efficiency of programmed stimulation can be improved by the early use of a basic drive train cycle length of 350 msec and three extrastimuli. Compared with a conventional stimulation protocol, the accelerated protocol used in this study reduces the number of protocol steps and duration of time required to induce monomorphic VT by an average of more than 50% and improves the specificity of programmed stimulation without impairing the yield of monomorphic VT.
Cardiac Pacing, Artificial↗
Catheter modification of the atrioventricular junction with radiofrequency energy for control of atrioventricular nodal reentry tachycardia.
BACKGROUND: The utility of transcatheter application of radiofrequency energy to eliminate atrioventricular nodal reentrant tachycardia (AVNRT) was investigated. METHODS AND RESULTS: Thirty-nine patients (mean age, 53 +/- 20 years; range 14-86 years) with medically refractory AVNRT underwent perinodal ablation with radiofrequency energy. A custom-designed 6F catheter with a large (3-mm-long) distal electrode and interelectrode pacing of 2 mm was used in the majority of cases. The catheter used for ablation was initially positioned across the tricuspid anulus to obtain the largest His bundle electrogram, then withdrawn to obtain the largest atrial:ventricular electrogram ratio, with a small His bundle electrogram (less than or equal to 100 microV). Each application of radiofrequency energy (350-550 kHz, 16.2 +/- 5.2 W) was stopped after 60 seconds or if PR prolongation or an impedance rise was noted. The endpoints of the procedure were persistent modification of atrioventricular nodal conduction (either first-degree atrioventricular block or impairment of ventriculoatrial conduction) and noninducibility of AVNRT before and during isoproterenol administration. Radiofrequency energy was applied a mean of 6.8 +/- 3.5 times per session. After a mean follow-up of 8 +/- 3.0 months, 32 of the 39 patients (82%) have been free of AVNRT, and did not have high grade AV block. Three patients (8%) developed complete atrioventricular block and had pacemakers implanted. Two patients had unsuccessful initial procedures, and two patients had initially successful ablations but had recurrences of tachycardia 4-6 weeks later. Elimination of AVNRT appeared to be due to effects on the retrograde fast pathway in most patients. CONCLUSIONS: Radiofrequency ablation of the perinodal right atrium appears to be safe and effective for treatment of typical AVNRT:
Atrioventricular Node↗
A prospective comparison of class IA, B, and C antiarrhythmic agents in combination with amiodarone in patients with inducible, sustained ventricular tachycardia.
BACKGROUND: Clinical experience suggests that combinations of antiarrhythmic agents provide more effective control of ventricular tachyarrhythmias than does therapy with single agents. METHODS AND RESULTS: Antiarrhythmic and electrophysiological effects of three class I antiarrhythmic agents, one from each subclass A, B, and C, were assessed in single use and in combination with amiodarone in patients with inducible, sustained ventricular tachycardia that was not suppressed by monotherapy with these agents. Thirty-one patients underwent an electrophysiology test on four occasions: at baseline; after 2-4 days of treatment with quinidine, mexiletine, or encainide; after 2 weeks of treatment with 1,200 mg/day amiodarone; and last, after 2-4 days of treatment with both amiodarone and the previously tested class I agent. The combination of a class I agent and amiodarone prevented the induction of sustained ventricular tachycardia in only one of 31 (3%) patients. Ventricular tachycardia became hemodynamically stable in 11 of 31 (34%) patients because of a marked prolongation in the tachycardia cycle length. It increased from 323 +/- 39 to 423 +/- 84 msec (n = 11, p less than 0.01) by adding encainide to amiodarone therapy, and it showed a tendency to lengthen when quinidine was added to amiodarone (from 373 +/- 77 to 425 +/- 58 msec; n = 10, NS). Each class I agent increased amiodarone-induced depression in myocardial conduction, but the extent of the additional depression seemed to differ among the three subclasses. Ventricular refractoriness was increased by all class I agents when used in combination with amiodarone, although not by mexiletine or encainide when used alone. CONCLUSIONS: Class I antiarrhythmic agents slow ventricular conduction and increase ventricular refractoriness when used in combination with amiodarone. When amiodarone and class I drugs by themselves do not suppress the induction of ventricular tachycardia, the combination of amiodarone and a class I agent seldom results in noninducibility; however, it often lengthens the ventricular tachycardia cycle length and may render the ventricular tachycardia hemodynamically stable.
Amiodarone↗