Effects of quinidine and amiodarone on blood pressure during rapid ventricular pacing in coronary artery disease.
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Aged↗
Biomedical subjects
F Morady
Publications and source records attributed to F Morady.
Determinants of impedance during radiofrequency catheter ablation in humans.
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Adolescent↗
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↗
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↗
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↗
Comparison of the cost of radiofrequency catheter modification of the atrioventricular node and medical therapy for drug-refractory atrioventricular node reentrant tachycardia.
The purpose of this study was to determine the charges for radiofrequency catheter modification of the atrioventricular (AV) node in 15 patients with symptomatic AV node reentrant tachycardia despite pharmacologic therapy and to compare these charges with the estimated charges for health care utilization by the same patients before the catheter procedure was performed. There were seven men and eight women with a mean age of 50 +/- 17 years. The mean duration and frequency of symptoms were 16 +/- 9 years and 4.5 +/- 6 episodes/month, respectively. Fourteen of the 15 patients required only one procedure for diagnosis and cure of AV node reentrant tachycardia and 1 patient required two sessions. All patients underwent electrophysiologic study before discharge from the hospital to confirm the short-term efficacy of the procedure. The mean duration of the hospital stay was 3 +/- 1.5 days and the mean total charge/patient expressed in 1991 dollars was $15,893 +/- $3,338 for catheter modification. These total charges consisted of hospital charges of $8,105 +/- $2,466 and physician charges of $7,788 +/- $971. All patients had a successful outcome and required no additional antiarrhythmic therapy. The estimated cost of health care utilization for these 15 patients before cure of AV node reentrant tachycardia was $7,651/patient per year. These estimated costs included charges incurred for emergency room visits, office visits, hospitalizations and antiarrhythmic drug therapy. In conclusion, the results of this study indicate that the annual health care costs incurred by patients who have symptomatic, drug-refractory paroxysmal supraventricular tachycardia caused by AV node reentry are substantial.(ABSTRACT TRUNCATED AT 250 WORDS)
Anti-Arrhythmia Agents↗
Recurrence of conduction in accessory atrioventricular connections after initially successful radiofrequency catheter ablation.
The purpose of this study was to characterize the incidence and clinical features of accessory pathway recurrence after initially successful radiofrequency catheter ablation and to identify variables correlated with recurrence. Radiofrequency ablation was performed with a 7F deflectable tip catheter with a large (4 mm in length) distal electrode. Left-sided accessory pathways were approached through the left ventricle and right-sided pathways by way of the right atrium. Patients were included in the study if 1) they had an initially successful procedure, defined as the absence of accessory pathway conduction immediately after ablation, and 2) had undergone a 3-month follow-up electrophysiologic test or had documented recurrence of accessory pathway conduction. Accessory pathway conduction recurred after initially successful ablation in 16 (12%) of 130 patients. Almost half (7 of 16) of these recurrences were in the 1st 12 h after ablation, and the last occurred after 106 days. Return of delta waves on the electrocardiogram (ECG) or spontaneous paroxysmal supraventricular tachycardia was the initial indication of recurrence in 15 of the 16 patients. Two patients with manifest accessory pathways exhibited recurrence with exclusively concealed accessory pathway conduction. Accessory pathways ablated from the tricuspid anulus (right free wall or septal accessory pathways) had a much higher recurrence rate (24%) than did those on the mitral anulus (6%). Fourteen of 15 patients have had successful repeat accessory pathway ablation after the initial recurrence. After a mean follow-up period of 4 +/- 3 months, there have been no repeat recurrences of any of these accessory pathways. It is concluded that accessory pathway recurrence is infrequent after successful radiofrequency catheter ablation.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Impedance monitoring during radiofrequency catheter ablation in humans.
Radiofrequency catheter ablation of accessory pathways and the atrioventricular junction often requires multiple applications of energy. The inability to determine the effects of any given application on the underlying tissue may contribute to this problem. In the present study, impedance was monitored in 20 patients undergoing radiofrequency catheter ablation, and the relationship between an initial decrease in impedance and subsequent effects were examined. An initial fall in impedance of more than 10 omega was 78% sensitive and 88% specific for predicting subsequent evidence of tissue heating (interruption of conduction or an abrupt rise in impedance due to coagulum formation). In contrast, initial values of voltage, current, or impedance did not distinguish between effective and ineffective applications of radiofrequency energy. Continuous monitoring of impedance may facilitate radiofrequency catheter ablation.
Adult↗
Effects of an acute increase in atrial pressure on atrial refractoriness in humans.
Contraction-excitation feedback has been studied extensively in mammalian ventricles. In contrast, little is known about contraction-excitation feedback in mammalian atria. The objective of this study was to investigate the effect of acute alterations in atrial pressure, induced by varying the atrioventricular (AV) interval, on atrial refractoriness. Twenty patients without structural heart disease participated in the study. In each patient the atrial effective (ERP) and absolute refractory periods (ARP) were measured during AV pacing at a cycle length of 500 msec and an AV interval of 120 msec. Acute increases in atrial pressure were induced by pacing the atrium and ventricle simultaneously for the final two beats of the drive train. The ERP was defined as the longest extrastimulus coupling interval that failed to capture with an extrastimulus current strength of twice the stimulation threshold. The ARP was defined in a similar manner with an extrastimulus current strength of 10 mA. The ERP and ARP were determined using the incremental extrastimulus technique. A subset of patients had the pacing protocol performed during autonomic blockade. As the AV interval of the final two beats of the drive train was shortened from 120 msec to 0 msec, the peak right atrial pressure increased from 7 +/- 3 mmHg to 15 +/- 5 mmHg (P < 0.001). The increase in atrial pressure associated with simultaneous pacing of the atrium and ventricle resulted in shortening of the atrial ERP and ARP by 7.3 +/- 5.2 and 6.2 +/- 3.5 msec, respectively (P < 0.001). Similar results were obtained during autonomic blockade. these findings confirm the presence of contraction-excitation feedback in normal human atria.
Adult↗
Effect of the atrioventricular relationship on atrial refractoriness in humans.
Atrial arrhythmias occur frequently in the setting of increased atrial size and pressure. This may result from contraction-excitation feedback. The objective of this study was to investigate the effect of alterations in atrial pressure, induced by varying the atrioventricular (AV) interval, on atrial refractoriness, and on the frequency of induction of atrial fibrillation. Twenty-seven patients without structural heart disease participated in the study. In each patient the atrial effective (ERP) and absolute refractory period (ARP) were measured during AV pacing at a cycle length of 400 msec and AV intervals of 0, 120, and 160 msec. The ERP was defined as the longest extrastimulus coupling interval that failed to capture with an extrastimulus current strength of twice the stimulation threshold. The ARP was defined in a similar manner with an extrastimulus current strength of 10 mA. The ERP and ARP were determined during continuous pacing using the incremental extrastimulus technique. A subset of patients had the pacing protocol performed during autonomic blockade. As the AV interval was increased from 0 to 160 msec, the peak right atrial pressure decreased from 16 +/- 4 mmHg to 7 +/- 3 mmHg and the mean right atrial pressure decreased from 7 +/- 3 mmHg to 3 +/- 22 mmHg (P less than 0.001). The atrial ERP and ARP did not change with alterations in the AV interval. There was no difference in the frequency of induction of atrial fibrillation. Similar results were obtained during autonomic blockade. These findings suggests that the phenomenon of contraction-excitation feedback may not be of importance in the development of atrial arrhythmias in patients without structural heart disease.
Adult↗
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↗
Radiofrequency catheter ablation of accessory atrioventricular connections in 250 patients. Abbreviated therapeutic approach to Wolff-Parkinson-White syndrome.
BACKGROUND: The purpose of this study was to report the results and complications of radiofrequency catheter ablation of accessory atrioventricular (AV) connections by using an abbreviated approach aimed at minimizing the duration of the procedure. METHODS AND RESULTS: Two hundred fifty consecutive patients with the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardia involving a concealed accessory AV connection underwent catheter ablation with the use of radiofrequency current. In 179 of the 250 patients, catheter ablation was performed at the time of an initial electrophysiology test. Two hundred thirty-five patients had one accessory AV connection and 15 patients had two or more. One hundred eighty-three accessory AV connections were manifest and 84 were concealed. One hundred sixty-one were were located in the free wall of the left ventricle, 47 were in the right free wall, 44 were posteroseptal, 10 were anteroseptal, and five were intermediate test, and the ablation procedure was recorded for each patient, as was the total duration of fluoroscopy. A follow-up electrophysiology test was performed 2-3 months after the ablation procedure. Ninety-four percent of patients had all accessory AV connections successfully ablated and remained free of symptomatic tachycardia during a mean follow-up of 10 +/- 4 months. Two hundred nineteen patients (88%) had all accessory AV connections ablated during the initial attempt at catheter ablation. Mean duration of the entire procedure was 134 +/- 75 minutes. Procedure duration was longest in patients with multiple accessory AV connections, shortest in patients with intermediate septal accessory AV connections, and similar in all other locations. A nonfatal complication occurred in nine patients (4%). CONCLUSIONS: The results of this study indicate that catheter ablation of accessory AV connections with radiofrequency current can be performed safely and expeditiously in a majority of patients and confirm in a large series the feasibility of catheter ablation at the time of an initial diagnostic electrophysiology test. This abbreviated therapeutic approach avoids the need for electropharmacological testing, long-term antiarrhythmic drug therapy, and surgical therapy in the majority of patients with the Wolff-Parkinson-White syndrome or with symptomatic tachycardias involving accessory AV connections.
Adult↗
Temperature monitoring during radiofrequency catheter ablation of accessory pathways.
BACKGROUND: Animal studies have suggested that the temperature of the electrode-tissue interface during radiofrequency catheter ablation accurately predicts lesion size. The purpose of the current study was to evaluate the utility of continuous temperature monitoring during radiofrequency catheter ablation in patients with Wolff-Parkinson-White syndrome. METHODS AND RESULTS: Twenty patients with manifest preexcitation were included in the study. The ablation catheter was positioned on the ventricular side of the mitral annulus for left-sided accessory pathways and on the atrial side of the tricuspid annulus for right-sided and septal accessory pathways. A thermistor imbedded in the distal electrode of the ablation catheter allowed continuous temperature monitoring during each energy application. To define the relation between power and temperature, radiofrequency current was applied several times at each site using outputs of 20, 30, 40, and 50 W. The accessory pathways were successfully ablated in each of the 20 patients. Because of marked variability in the efficiency of heating between sites, power output did not predict temperature. However, at any given site, there was a positive dose-response relation between power and temperature. Radiofrequency energy applications on the atrial side of the tricuspid annulus produced lower temperatures than did applications on the ventricular side of the mitral annulus (49 +/- 7 versus 60 +/- 16 degrees C, p = 0.0001). Transient block in the accessory pathways occurred at a mean of 50 +/- 8 degrees C, whereas permanent block was seen at a mean of 62 +/- 15 degrees C (p = 0.0001). Less than half of the applications at outputs < or = 40 W produced temperatures adequate to interrupt accessory pathway conduction. An abrupt rise in impedance caused by coagulum formation occurred only at temperatures between 95 and 100 degrees C. CONCLUSIONS: Temperature monitoring may facilitate radiofrequency catheter ablation of accessory pathways. By adjusting power output to ensure that adequate but not excessive temperatures have been achieved, a rise in impedance can be avoided and the total number of energy applications and procedure duration may be reduced.
Adult↗
Reduction in medical care cost associated with radiofrequency catheter ablation of accessory pathways.
The cost of definitive therapy was compared in 25 patients who underwent radiofrequency catheter ablation of accessory pathways in 1990 and 25 patients who underwent surgical ablation of accessory pathways in 1989. In the radiofrequency group, 23 of 25 patients had a single accessory pathway and the remaining 2 patients each had 2 accessory pathways. In the surgical group, 20 patients had a single accessory pathway and 5 patients each had 2 accessory pathways. The success rate was 96% in each group. The mean duration of hospitalization was 3 +/- 1 days in the radiofrequency group and 9 +/- 4 days in the surgical group (p less than 0.0001). All the cost data are expressed in fiscal year 1990/1991 dollar values. The total cost of therapy in the radiofrequency group was $14,919 +/- $6,740 compared with $53,265 +/- $12,755 in the surgical group (p less than 0.0001). The cost of radiofrequency ablation consisted of a hospital charge of $7,753 +/- $3,472 and physician fees of $7,166 +/- $3,439. The hospital charge included charges for use of the electrophysiology laboratory, hospital stay, electrocardiograms, echocardiograms and blood studies. The cost of surgery consisted of a hospital charge of $37,708 +/- $10,179 and physician fees of $15,557 +/- $3,149. The hospital charge in the surgical group included the costs of a baseline electrophysiology study, in-hospital care and a follow-up office visit. In conclusion, radiofrequency catheter ablation of accessory pathways results in a dramatic reduction in the cost of definitive therapy in patients with the Wolff-Parkinson-White syndrome.
Adolescent↗
Incidence of loss of consciousness during automatic implantable cardioverter-defibrillator shocks.
OBJECTIVE: To determine the incidence of loss of consciousness occurring in association with shocks delivered by automatic implantable cardioverter-defibrillators (AICD) in patients who had undergone implantation as treatment for ventricular tachycardia or ventricular fibrillation. DESIGN: Cohort study. SETTING: Two major tertiary medical care facilities. PATIENTS: A total of 180 patients who had undergone implantation of an AICD for treatment of ventricular tachycardia or ventricular fibrillation. INTERVENTION: Implantation of an AICD that delivered only high-energy shock. MEASUREMENTS: During a mean (+/- SD) follow-up period of 16 +/- 12 months, the incidence of loss of consciousness occurring in association with spontaneous AICD shocks was determined. Various clinical factors were analyzed to identify predictors of loss of consciousness that occurred during AICD shocks. MAIN RESULTS: Of the 180 patients who received an AICD, 106 patients (59%) experienced AICD shocks during follow-up. Sixteen of the 180 patients (9%) experienced loss of consciousness; 13 of these 16 patients had syncope and 3 died suddenly, in association with AICD shocks. The absence of syncope during one AICD shock did not always predict the absence of syncope during subsequent shocks. Syncope could not be predicted by age, sex, history of syncope, left ventricular function, type of underlying heart disease, electrophysiologic findings, rate of ventricular tachycardia, antiarrhythmic medications, and type of pulse generator implanted. CONCLUSIONS: Patients with sustained ventricular tachycardia or ventricular fibrillation who receive an AICD that delivers only high-energy shock therapy are at moderate risk for experiencing loss of consciousness during AICD shocks. No clinical variables were found to be predictors of syncope. Therefore, driving and other activities that require patients to be extra vigilant should not be assumed to be safe after implantation of an AICD that delivers only high-energy shock.
Adult↗
Noncapturing stimuli during the basic drive shorten ventricular refractoriness.
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Adolescent↗