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Biomedical subjects

F Morady

Publications and source records attributed to F Morady.

At least 199 records · Page 11Linked to original sources
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

The response of paroxysmal supraventricular tachycardia to overdrive atrial and ventricular pacing: can it help determine the tachycardia mechanism?

INTRODUCTION: Standard electrophysiologic techniques generally allow discrimination among mechanisms of paroxysmal supraventricular tachycardia. The purpose of this study was to determine whether the response of paroxysmal supraventricular tachycardia to atrial and ventricular overdrive pacing can help determine the tachycardia mechanism. METHODS AND RESULTS: Fifty-three patients with paroxysmal supraventricular tachycardia were studied. Twenty-two patients had the typical form of atrioventricular (AV) junctional (nodal) reentry, 18 patients had orthodromic AV reentrant tachycardia, 10 patients had atrial tachycardia, and 3 patients had the atypical form of AV nodal reentrant tachycardia. After paroxysmal supraventricular tachycardia was induced, 15-beat trains were introduced in the high right atrium and right ventricular apex sequentially with cycle lengths beginning 10 msec shorter than the spontaneous tachycardia cycle length. The pacing cycle length was shortened in successive trains until a cycle of 200 msec was reached or until tachycardia was terminated. Several responses of paroxysmal supraventricular tachycardia to overdrive pacing were useful in distinguishing atrial tachycardia from other mechanisms of paroxysmal supraventricular tachycardia. During decremental atrial overdrive pacing, the curve relating the pacing cycle length to the VA interval on the first beat following the cessation of atrial pacing was flat or upsloping in patients with AV junctional reentry or AV reentrant tachycardia, but variable in patients with atrial tachycardia. AV reentry and AV junctional reentry could always be terminated by overdrive ventricular pacing whereas atrial tachycardia was terminated in only one of ten patients (P < 0.001). The curve relating the ventricular pacing cycle length to the VA interval on the first postpacing beat was flat or upsloping in patients with AV junctional reentry and AV reentry, but variable in patients with atrial tachycardia. The typical form of AV junctional reentry could occasionally be distinguished from other forms of paroxysmal supraventricular tachycardia by the shortening of the AH interval following tachycardia termination during constant rate atrial pacing. CONCLUSIONS: Atrial and ventricular overdrive pacing can rapidly and reliably distinguish atrial tachycardia from other mechanisms of paroxysmal supraventricular tachycardia and occasionally assist in the diagnosis of other tachycardia mechanisms. In particular, the ability to exclude atrial tachycardia as a potential mechanism for paroxysmal supraventricular tachycardia has important implications for the use of catheter ablation techniques to cure paroxysmal supraventricular tachycardia.

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 atypical atrioventricular nodal reentrant tachycardia.

INTRODUCTION: Published reports of radiofrequency ablation of atypical atrioventricular nodal reentrant tachycardia (AVNRT) have been limited. We present our experience in 10 consecutive patients with atypical AVNRT who underwent radiofrequency ablation of the "slow" AV nodal pathway. METHODS AND RESULTS: There were 9 females and 1 male; their mean age was 44 +/- 19 years (+/- SD). The mean AVNRT cycle length and ventriculoatrial (VA) interval at the His position during AVNRT were 340 +/- 50 msec and 200 +/- 70 msec, respectively. The slow pathway was successfully ablated in all patients with a mean of 10 +/- 7 radiofrequency energy applications in the posteroseptal right atrium near the coronary sinus os. The mean procedure duration was 100 +/- 35 minutes. There were no complications. In 4 patients, target sites were identified during sinus rhythm by mapping for possible slow pathway potentials. In the other 6 patients, target sites were identified by mapping retrograde atrial activation during AVNRT or ventricular pacing. The VA times at successful target sites were a mean of 45 +/- 30 msec less than the VA time at the His catheter during AVNRT. There were no differences in success rate, number of radiofrequency energy applications, or procedure duration between patients in whom mapping was guided by possible slow pathway potentials or by retrograde atrial activation. During 6 +/- 3 months of follow-up, 1 patient had a recurrence of atypical AVNRT and underwent a second ablation procedure, which was successful. CONCLUSION: Radiofrequency ablation of atypical AVNRT can be safely and effectively accomplished when target sites are identified based either on possible slow pathway potentials during sinus rhythm or retrograde atrial activation times during tachycardia.

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

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↗
PubMed1993

Nonthoracotomy lead implantable cardioverter defibrillators: normal radiographic appearance.

Recently, cardioverter defibrillators with leads and patches that can be implanted via a combination of transvenous and subcutaneous routes rather than via thoracotomy have been developed. Early experience in patients subject to serious ventricular arrhythmias suggests that, as with surgically implanted defibrillators, these nonthoracotomy defibrillators can reduce the risk of sudden death due to cardiac arrest [1]. Moreover, high perioperative complication rates associated with thoracotomy-inserted cardioverter defibrillators are avoided [2]. Four models are currently undergoing clinical trials in the United States. We have used three of these models: PCD (Medtronic, Minneapolis, MN), ENDOTAK (Cardiac Pacemakers Inc., St. Paul, MN), and RES-Q (Intermedics, Freeport, TX). This essay illustrates the normal radiographic appearance of these devices.

Defibrillators, Implantable↗
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↗