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Biomedical subjects

H Calkins

Publications and source records attributed to H Calkins.

At least 91 records · Page 5Linked to original sources
PubMed1993

Differentiation of paroxysmal narrow QRS complex tachycardias using the 12-lead electrocardiogram.

OBJECTIVES: The purpose of this study was to evaluate the utility of the 12-lead electrocardiogram (ECG) for differentiating paroxysmal narrow QRS complex tachycardias. BACKGROUND: Previous studies evaluating the utility of the 12-lead ECG for differentiating paroxysmal supraventricular tachycardia types have shown conflicting results on the usefulness of some ECG criteria, and some criteria that are considered to be useful have never been formally evaluated. METHODS: Two hundred forty-two ECGs demonstrating paroxysmal narrow QRS complex (< 0.11 ms) tachycardia (rate > or = 120 beats/min) were analyzed. All ECGs were analyzed by an observer who had no knowledge of the mechanism of the tachycardia. RESULTS: There were 137 atrioventricular (AV) reciprocating tachycardias, 93 AV node reentrant tachycardias and 12 atrial tachycardias. Six criteria were found to be significantly different between tachycardia types by univariate analysis. A P wave separate from the QRS complex was observed more frequently in AV reciprocating tachycardia (68%) and atrial tachycardias (75%). A pseudo r' deflection in lead V1 and a pseudo S wave in the inferior leads were more common in AV node reentrant tachycardia (58% and 14%, respectively); QRS alternans was present more often during AV reciprocating tachycardia (27%). When a P wave was present, an RP/PR interval ratio > or = 1 was more common in atrial tachycardias (89%). During sinus rhythm, manifest pre-excitation was observed more often in patients with AV reciprocating tachycardia (45%). By multivariate analysis, the presence of a P wave separate from the QRS complex, pseudo r' deflection in lead V1, QRS alternans during tachycardia and the presence of pre-excitation during sinus rhythm were independent predictors of tachycardia type. These criteria correctly identified 86% of AV node reentrant tachycardias, 81% of AV reciprocating tachycardias and incorrectly assigned the tachycardia type in 19% of cases. CONCLUSIONS: Several features on the ECG are useful for differentiating supraventricular tachycardia type. However, approximately 20% of tachycardias may be incorrectly classified on the basis of analysis of the ECG; therefore, the ECG should not serve as the sole means for determining tachycardia mechanism.

Adolescent↗
PubMed1993

A prospective randomized comparison of direct current and radiofrequency ablation of the atrioventricular junction.

OBJECTIVES: The purpose of this study was to compare direct current and radiofrequency ablation of the atrioventricular (AV) junction in a prospective randomized fashion. BACKGROUND: Catheter ablation of the AV junction can be performed using either direct current shocks or radiofrequency energy. To date, these two techniques have never been compared prospectively or in a randomized study. METHODS: Forty patients with drug-refractory uncontrolled atrial fibrillation-flutter (38 patients) or inappropriate sinus tachycardia (2 patients) were randomly assigned to undergo direct current ablation (20 patients) using up to four shocks of 200 to 300 J or radiofrequency ablation (20 patients) using up to 15 applications of 16 to 25 W for 30 s. If complete AV block was not successfully induced, the ablation procedure was repeated using the alternate type of energy. A rate-responsive ventricular pacemaker was implanted in each patient. The intrinsic escape rhythm was evaluated 15 min, 2 days and 3, 6 and 12 months after ablation. RESULTS: Persistent complete AV block was successfully induced during the first ablation session in 13 (65%) of 20 patients randomly assigned to undergo direct current ablation, compared with 19 (95%) of 20 patients randomly assigned to undergo radiofrequency ablation (p < 0.05). Each patient whose first ablation attempt failed had a successful outcome with the alternate type of energy. The overall efficacy of radiofrequency ablation (26 [96%] of 27 patients) was significantly greater than that of direct current ablation (14 [67%] of 21 patients, p < 0.01). The duration of the direct current and radiofrequency ablation sessions did not differ significantly. The mean peak plasma creatine kinase MB fraction concentration was significantly higher after direct current ablation (58 +/- 29 IU/liter) than after radiofrequency ablation (2 +/- 2 IU/liter) (p < 0.001). An escape rhythm was present 15 min after ablation in an equal proportion of patients undergoing direct current and radiofrequency ablation (78% and 85%, respectively, p = 0.6). An escape rhythm was present in all patients 3, 6 and 12 months after ablation. The mean escape rhythm cycle length 15 min after direct current ablation (2,074 +/- 677 ms) was significantly longer than that 15 min after radiofrequency ablation (1,460 +/- 294 ms) (p < 0.05); however, the mean escape rhythm cycle lengths did not differ significantly at 2 days or 3, 6 or 12 months after ablation. Immediate arrhythmic complications did not occur after either procedure. One patient died suddenly 6.5 months after direct current ablation. CONCLUSIONS: Radiofrequency ablation of the AV junction is more efficacious and safer than direct current ablation and should be the preferred method for inducing complete AV block in patients who are appropriate candidates for ablation of AV conduction.

Aged↗
PubMed1993

Association between atrioventricular node reentrant tachycardia and inducible atrial flutter.

OBJECTIVES: The purpose of this study was to evaluate the inducibility of atrial flutter in patients with atrioventricular (AV) node reentrant tachycardia and to determine the effect of radio-frequency ablation of the slow AV node pathway on the inducibility of atrial flutter. BACKGROUND: Studies have shown that both AV node reentrant tachycardia and atrial flutter are reentrant arrhythmias having an area of slow conduction that is located in the low posterior right atrium near the ostium of the coronary sinus. METHODS: Ninety-one patients were prospectively evaluated using a standardized atrial pacing protocol. Three groups of patients were analyzed: 42 patients with inducible AV node reentrant tachycardia, 13 with a history of spontaneous atrial flutter and 36 control patients. A subgroup of 34 patients with AV node reentrant tachycardia who underwent successful radiofrequency ablation of the slow AV node pathway underwent atrial pacing again after ablation. RESULTS: Atrial flutter was more frequently inducible in patients with AV node reentrant tachycardia (88%) and in those with a history of atrial flutter (92%) than in control patients (36%) (p = 0.0001). There were no differences between the patient groups with respect to atrial effective refractory period, P wave duration or PA interval at the His position. Among the 34 patients with AV node reentrant tachycardia who underwent atrial pacing before and after radiofrequency ablation, there were 30 with atrial flutter and 4 with atrial fibrillation before ablation and 29 with atrial flutter and 5 with atrial fibrillation after ablation (p = NS). There was no difference in the duration of the induced atrial flutter before and after ablation. The mean atrial flutter cycle length before ablation (206 +/- 22 ms) was not different from that after ablation (196 +/- 20 ms) (p = NS). CONCLUSIONS: There is a strong association between AV node reentrant tachycardia and inducible atrial flutter, suggesting that there may be a common area of perinodal atrium participating in the two tachycardia circuits. However, radiofrequency ablation of the slow pathway of the AV node reentrant tachycardia circuit does not influence the inducibility of atrial flutter.

Adult↗
PubMed1993

Comparison of fixed burst versus decremental burst pacing for termination of ventricular tachycardia.

The objective of this study was to compare prospectively the efficacy of fixed burst pacing with that of decremental burst pacing in terminating VT. Forty-four patients with inducible sustained monomorphic VT were studied. The efficacy of fixed burst and decremental burst pacing for terminating 57 distinct types of VT were compared during 50 electrophysiology tests (mean VT cycle length = 334 +/- 84 msec). Termination of each type of VT was attempted with fixed burst and decremental burst pacing. Both pacing algorithms were delivered in an adaptive fashion with an increasing number of stimuli with each successive attempt at VT termination. Seventy percent of VT episodes were successfully terminated with fixed burst pacing. The mean number of stimuli required for VT termination was 5 +/- 2. Seventy-two percent of VT episodes were successfully terminated with decremental burst pacing. The mean number of stimuli required for VT termination was 5 +/- 2. For fixed burst and decremental burst pacing, the efficacy of VT termination was greater for VTs with a cycle length > 300 msec than for faster VTs (P < 0.05). The efficacy of VT termination and the incidence of VT acceleration were no different for the two pacing algorithms (P > 0.1). The results of this study demonstrate that fixed burst and decremental burst pacing are equally effective in terminating VT and that a single adaptive pacing algorithm is effective in terminating nearly three fourths of VTs.

Aged↗
PubMed1993

Titration of power output during radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia.

Radiofrequency lesions in the anterior, superior aspect of the tricuspid annulus result in selective elimination of fast pathway function in patients with typical atrioventricular (AV) nodal reentry tachycardia. This technique is simple and effective, but has been associated with a significant risk of inadvertent complete AV block. The purpose of this study was to compare the safety and effectiveness of two different techniques for radiofrequency catheter ablation of the fast AV nodal pathway. Initially, a fixed power output was used at each target site. This method was compared retrospectively to a newer technique where power output was gradually incremented at each site. Radiofrequency power was initially applied at 10 watts for 10-15 seconds. If no junctional ectopy or a change in PR interval was seen, power output was incremented by 2 to 4 watts every 10 to 15 seconds up to a maximum of 30 watts. Thirty seven of 38 (96%) patients treated using this incremental power output were cured of their AV nodal reentry tachycardia. None of these patients developed inadvertent complete AV block. In contrast, 92% of historic controls treated with a fixed power output between 20 and 30 watts achieved a primary success and nine of these 89 (10%) historic controls developed inadvertent complete AV block (P = 0.04). There was no difference in the amplitudes of atrial, His, or ventricular electrograms at the effective sites between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrioventricular Node↗
PubMed1993

Delayed effects of radiofrequency energy on accessory atrioventricular connections.

The purpose of this study was to determine the incidence and characteristics of delayed effects on conduction through accessory atrioventricular (AV) connections after apparently successful attempts at radiofrequency catheter ablation. Among 450 patients who had 471 accessory AV connections, the ablation procedure was unsuccessful in 26 patients (6%), as defined by persistent conduction through the accessory AV connection 60 minutes after the final application of radiofrequency energy. In 6/26 unsuccessfully treated patient (24%), conduction through the accessory AV connection disappeared on a delayed basis. At least once during the ablation procedure, conduction through each of these 6 accessory AV connections was transiently eliminated for 10 seconds to 60 minutes. Five of these accessory AV connections were left-sided and one was posteroseptal; one was concealed and five were manifest. Conduction through the accessory AV connection disappeared on a delayed basis 6-18 hours after the ablation procedure in 4 patients, and at some time between 1-5 days or 1-60 days in the other 2 patients. In 2 patients, the delayed effect was only transient, while in 4 patients, conduction through the accessory AV connections did not return during 5-23 months of follow-up. In conclusion, up to 15% of patients who undergo an apparently unsuccessful attempt at radiofrequency ablation of an accessory AV connection may later manifest a permanent loss of conduction through the accessory AV connection.

Adult↗
PubMed1993

Management of nonsustained ventricular tachycardia guided by electrophysiological testing.

Two hundred eighty patients with spontaneous nonsustained ventricular tachycardia were treated based on the results of electrophysiological testing. Seventy-nine patients had no evidence of structural heart disease, 134 had coronary artery disease, 43 had idiopathic dilated cardiomyopathy, and 24 patients had miscellaneous types of heart disease. Sustained monomorphic ventricular tachycardia was induced during electrophysiological testing in the drug free state in 52 of 280 patients (19%). Ventricular tachycardia was induced more frequently in patients with coronary artery disease (32%) than in any of the other groups (P < 0.001). The patients with inducible sustained monomorphic ventricular tachycardia underwent a mean of 1.9 +/- 1.3 drug trials. Twenty-five patients had the induction of ventricular tachycardia suppressed by pharmacological therapy and were treated with the drug judged to be effective during electropharmacological testing. Twenty-seven patients continued to have inducible sustained monomorphic ventricular tachycardia despite antiarrhythmic therapy and were discharged on the drug that made induced ventricular tachycardia best tolerated. Forty-five of 280 patients (16.1%) died during a mean follow-up period of 19.6 +/- 14.4 months. There were 15 sudden cardiac deaths, 21 nonsudden cardiac deaths, 6 noncardiac deaths, and 3 deaths that could not be classified. Sudden cardiac death mortality was lowest in the patients without structural heart disease (0% at 2 years), intermediate in the patients with coronary artery disease and miscellaneous heart disease (4% at 2 years), and highest in the patients with idiopathic dilated cardiomyopathy (13% at 2 years; P < 0.01 for pairwise comparisons). No patient treated with a drug that had suppressed the induction of sustained ventricular tachycardia died suddenly during the follow-up period whereas four of 27 patients who were discharged on "ineffective antiarrhythmic drugs" and 11 of 228 patients without inducible sustained ventricular tachycardia experienced sudden cardiac death during the follow-up period. By multivariate analysis, ejection fraction and inducible ventricular tachycardia during the predischarge electrophysiological test were independent predictors of sudden cardiac death. In conclusion, in patients with spontaneous non-sustained ventricular tachycardia: (1) Arrhythmia inducibility varies depending on the underlying heart disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Inducibility of atrial fibrillation before and after radiofrequency catheter ablation of accessory atrioventricular connections.

INTRODUCTION: The purpose of this study was to evaluate the inducibility of atrial fibrillation in patients with an accessory atrioventricular connection (AAVC) and to determine if the inducibility of atrial fibrillation is altered after successful radiofrequency catheter ablation of the AAVC. METHODS AND RESULTS: Thirty-seven patients with an AAVC and 36 control patients were prospectively evaluated using a standardized atrial pacing protocol. The high right atrium was paced using a 25-beat drive train, 1.5-second intertrain pause, 10-mA pulse amplitude, and 2-msec pulse duration at cycle lengths of 250 to 100 msec, in 10-msec decrements. Pacing was performed twice at each cycle length. Thirty patients with an AAVC underwent repeat atrial overdrive pacing after successful radiofrequency ablation of the AAVC. Atrial fibrillation was induced in 26 (70%) patients with an AAVC and 22 (61%) controls (P = NS). Atrial flutter was induced in 11 (30%) patients with an AAVC and 13 (36%) controls (P = NS). The cumulative percentage of patients with atrial fibrillation/flutter induced at each pacing cycle length was the same in each group. There was no difference in the duration of atrial fibrillation/flutter between control patients and patients with an AAVC. Among the 30 patients who underwent repeat atrial overdrive pacing after radiofrequency ablation of an AAVC, there was no difference in the inducibility or duration of atrial fibrillation/atrial flutter after ablation compared to baseline. CONCLUSION: These findings indicate that the vulnerability of the atrium to fibrillate in response to atrial pacing is independent of the presence of an AAVC.

Adult↗
PubMed1993

Radiofrequency catheter ablation of ventricular tachycardia in patients with coronary artery disease.

BACKGROUND: Radiofrequency (RF) ablation of idiopathic ventricular tachycardia (VT) has been demonstrated to be highly efficacious, but the efficacy of RF ablation of VT in patients with coronary artery disease has been unknown. Therefore, the purpose of this study was to determine the feasibility of RF ablation of VT in patients with coronary artery disease. METHODS AND RESULTS: Fifteen consecutive patients with coronary artery disease and a history of myocardial infarction underwent an attempt at RF ablation of 16 hemodynamically stable monomorphic VTs that had been documented clinically on a 12-lead ECG and that had not been successfully managed by pharmacological or device therapy. One VT was incessant, five occurred more than 25 times, and the remainder occurred two to 20 times. An additional four VTs that had not been documented clinically also were targeted for ablation. The mean age of the patients was 68 +/- 7 years (+/- SD), and their mean left ventricular ejection fraction was 0.27 +/- 0.08. The mean cycle length of the 20 VTs targeted for ablation was 438 +/- 82 msec. Ablation sites were selected based on endocardial activation mapping, pace mapping, identification of an isolated mid-diastolic potential, or concealed entrainment. Sixteen of the 20 VTs (80%) were successfully ablated in 11 of 15 patients (73%), using a mean of 4.2 +/- 3 applications of RF energy, and no recurrences of the ablated VTs occurred during 9.1 +/- 3.3 months of follow-up. The mean duration of the ablation procedures was 128 +/- 30 minutes. No complications occurred in any of the patients. CONCLUSIONS: The results of this study demonstrate that RF ablation of hemodynamically stable VT is feasible as adjunctive therapy in selected patients with coronary artery disease.

Aged↗
PubMed1993

A randomized, prospective comparison of anterior and posterior approaches to radiofrequency catheter ablation of atrioventricular nodal reentry tachycardia.

BACKGROUND: Two different techniques have been developed for radiofrequency catheter ablation of typical atrioventricular nodal reentry (AVNRT). Lesions made anteriorly near the apex of the triangle of Koch usually eliminate fast pathway function, whereas lesions made posteriorly near the ostium of the coronary sinus selectively affect slow pathway function. The current study compares the safety, efficacy, and electrophysiological effects of these two techniques in a prospective, randomized fashion. METHODS AND RESULTS: Fifty consecutive patients with typical AVNRT were randomly assigned to receive radiofrequency lesions either anteriorly (n = 22) or posteriorly (n = 28). If the initial approach failed to eliminate inducibility of AVNRT after 1 hour or 10 applications of radiofrequency energy, the alternative ablation technique was used. Patients underwent repeat electrophysiological testing 48 hours and 3 months after ablation. The primary success rates of the anterior and posterior techniques were similar (55% versus 68%, p = NS). All of the patients who failed the initial approach were successfully treated by the alternative technique without developing high-grade atrioventricular block. One patient developed right bundle branch block during an anterior lesion, and another patient developed complete atrioventricular block as the result of a posterior lesion. CONCLUSIONS: The posterior approach to radiofrequency catheter modification of the atrioventricular node is as effective as the anterior approach, and both techniques are associated with a low risk of complications. As long as AVNRT persists, it appears safe to cross over from one technique to the other.

Adult↗
PubMed1993

Scintigraphic pattern of regional cardiac sympathetic innervation in patients with familial long QT syndrome using positron emission tomography.

BACKGROUND: The purpose of this study was to determine whether scintigraphic evidence of cardiac sympathetic neuronal dysinnervation is present in patients with the familial long QT syndrome. The "sympathetic imbalance" hypothesis for the familial long QT syndrome proposes that the long QT syndrome results from a congenital imbalance of sympathetic innervation of the heart caused by lower-than-normal right cardiac sympathetic activity. Although the majority of clinical features of the long QT syndrome can be understood according to this hypothesis, its validity has never been shown. Noninvasive scintigraphic evaluation of the pattern of sympathetic innervation of the heart has recently become possible with catecholamine analogues that can be taken up by sympathetic nerve terminals: radioiodinated metaiodobenzyl guanidine or C-11 hydroxyephedrine (HED). METHODS AND RESULTS: Nine affected patients, each from a separate family with familial long QT syndrome, were enrolled in this study (three men, six women; mean age, 39 +/- 16 years). Scintigraphic evaluation of the pattern of cardiac sympathetic innervation in each patient was performed with HED in conjunction with positron emission tomography. The results of scintigraphic imaging in these patients were compared with those obtained in 14 asymptomatic volunteers. Scintigraphic evaluation demonstrated that HED retention index and HED uptake normalized to blood flow were no different in patients with the familial long QT syndrome than in normal control patients. CONCLUSIONS: Patients with the long QT syndrome have normal cardiac sympathetic innervation as assessed by HED. This finding, although not incompatible with the sympathetic imbalance hypothesis of the long QT syndrome, suggests that if a decrease in right sympathetic activity is present in patients with familial long QT syndrome, it is unlikely to be attributed to an abnormal distribution of cardiac sympathetic nerves.

3-Iodobenzylguanidine↗
PubMed1993

Correlation between scintigraphic evidence of regional sympathetic neuronal dysfunction and ventricular refractoriness in the human heart.

BACKGROUND: Denervation supersensitivity has been proposed as a mechanism for the relation between ventricular arrhythmias and the sympathetic nervous system. Evaluation of this phenomenon in humans has become feasible only recently with the development of noninvasive scintigraphic methods for evaluating the pattern of sympathetic innervation. The purpose of this study was to determine if scintigraphic evidence of sympathetic neuronal dysfunction correlates with measurements of ventricular refractoriness and to evaluate the phenomenon of denervation supersensitivity in humans. METHODS AND RESULTS: Eleven patients with a history of sustained ventricular tachycardia or sudden cardiac death who were referred for placement of an implantable defibrillator participated in this study (seven men and four women; age, 51 +/- 18 years). Preoperative scintigraphic evaluation of the pattern of sympathetic innervation was performed with 11C-hydroxyephedrine in conjunction with positron emission tomography. At the time of surgery, ventricular refractoriness was determined in regions of myocardium demonstrating normal and reduced 11C-hydroxyephedrine retention in the baseline state and during an infusion of norepinephrine. Scintigraphic evaluation demonstrated regions of reduced 11C-hydroxyephedrine retention in each patient. The effective refractory period in areas of myocardium that demonstrated reduced 11C-hydroxyephedrine retention was significantly longer than in areas of myocardium demonstrating normal 11C-hydroxyephedrine retention (273 +/- 32 versus 243 +/- 32 msec, p < 0.001). Norepinephrine shortened the effective refractory period in regions of myocardium demonstrating normal and reduced 11C-hydroxyephedrine retention to a similar degree. CONCLUSIONS: There is a correlation between scintigraphic evidence of sympathetic neuronal dysfunction and ventricular refractoriness in the human heart. These observations help validate the use of scintigraphic techniques for evaluation of sympathetic innervation and may assist in the further evaluation of the relation between the sympathetic nervous system and ventricular arrhythmias.

Carbon Radioisotopes↗
PubMed1992

Conversion of typical to "atypical" atrioventricular nodal reentrant tachycardia after radiofrequency catheter modification of the atrioventricular junction.

Typical atrioventricular (AV) nodal reentry tachycardia (AVNRT) is characterized by anterograde activation over a slowly conducting pathway and by retrograde activation through a rapidly conducting pathway. Preliminary reports suggest that radiofrequency catheter modification can eliminate typical AVNRT while preserving anterograde conduction. Radiofrequency catheter modification was used to treat 88 patients with typical AVNRT. After baseline electrophysiologic evaluation, the ablation catheter was positioned proximal and superior to the site of maximal His deflection. Radiofrequency energy was applied until there was significant attenuation of retrograde conduction, and elimination of AVNRT inducibility. Eighty-one patients were successfully treated and form the basis of this report. A new paroxysmal supraventricular tachycardia with RP greater than PR interval was induced at electrophysiologic testing after successful ablation in 9 patients (11%). Mean atrial-His activation time was 140 +/- 31 ms, and the ventriculoatrial activation time was 170 +/- 46 ms. This arrhythmia was induced only with ventricular pacing during isoproterenol infusion and appeared to be mediated by AV nodal reentry. New retrograde dual AV nodal physiology after modification was more frequent in patients with atypical tachycardia than in those without (4 of 9 vs 2 of 72; p less than 0.0001). Although none of the patients were treated, only 1 of 9 had an episode of spontaneous atypical tachycardia during a mean follow-up of 12 months. Results of this study confirm that typical AVNRT can be rendered noninducible without the complete destruction of reentrant pathways. Because induction of "atypical" AVNRT was not predictive of spontaneous arrhythmia recurrence, it should not be an indication for additional ablation sessions or long-term drug therapy.

Adult↗
PubMed1992

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↗
PubMed1992

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↗
PubMed1992

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↗