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Biomedical subjects

M M Scheinman

Publications and source records attributed to M M Scheinman.

At least 55 records · Page 3Linked to original sources
PubMed1997

Biophysical characteristics of radiofrequency lesion formation in vivo: dynamics of catheter tip-tissue contact evaluated by intracardiac echocardiography.

During clinical radiofrequency catheter ablation a wide range of delivered power may be necessary to achieve success despite an apparently stable catheter position on fluoroscopy. The purpose of this study was to use intracardiac echocardiography to characterize the relation between catheter tip-tissue contact and the efficiency of heating during applications of radiofrequency energy in vivo and to determine whether intracardiac echocardiography could be used prospectively to improve tissue contact. A closed-loop temperature feedback control system was used during radio-frequency applications at five anatomic regions in the right atrium of 15 anesthetized dogs to ensure achievement of a predetermined temperature (70 degrees C) at the catheter tip thermistor by automatic adjustment of delivered power (maximum 100 W). The efficiency-of-heating index was defined as the ratio of steady-state temperature (degrees Celsius) to power (watts). Two-dimensional intracardiac echocardiography was used to evaluate movement of the catheter tip relative to the endocardium. Perpendicular contact was scored as good, average, or poor and lateral catheter sliding as < 2, 2 to 5, or > 5 mm. Two groups of animals were included: group 1, in which tissue contact was guided by fluoroscopic and electrographic criteria for stability of contact, with intracardiac echocardiography used simply to observe the application; and group 2, in which tissue contact was guided by intracardiac echocardiography. Of 66 applications, 18 (27.3%) had poor perpendicular contact on echocardiography, and 12 (18.2%) demonstrated lateral sliding of > 5 mm even though they had been considered to have good tissue contact by fluoroscopic and electrographic criteria. Perpendicular catheter contact and anatomic location were shown to be independently related to the efficiency-of-heating index. Applications with good perpendicular contact had a significantly higher efficiency-of-heating index and a significantly greater lesion size than those with average or poor contact. The percentage of applications having good perpendicular tissue contact and the lesion size were significantly greater when tissue contact was guided by intracardiac echocardiography compared with fluoroscopic and electrographic guidance. This study demonstrates that variations in catheter tip-tissue contact account for differences in the efficiency of tissue heating, independently of the anatomic site of the application. Poor tissue contact was observed by intracardiac echocardiography and confirmed by indexes of tissue heating in approximately one third of radiofrequency applications despite a fluoroscopic appearance and electrographic morphologic appearance suggestive of good tissue contact. There was a significant correlation between echocardiographic evaluation of tissue contact, parameters of tissue heating (efficiency-of-heating index), and lesion size. In addition, intracardiac echocardiography could be used prospectively to improve the percentage of good contact applications and increase the lesion size.

Analysis of Variance↗
PubMed1997

Radiofrequency catheter ablation for atrial fibrillation.

Until recently, catheter-based radiofrequency ablation for atrial fibrillation was limited to palliative approaches of either atrioventricular node ablation or modification. It is now recognized that at least a proportion of patients with paroxysmal atrial fibrillation may be suitable for curative ablation of an underlying single arrhythmogenic focus. With the intense interest in this area, a catheter-based cure involving endocardial linear lesion creation for patients with chronic or paroxysmal atrial fibrillation may not be far in the future.

Animals↗
PubMed1997

Slow AV nodal pathway ablation utilizing a unique temperature controlled radiofrequency energy system.

Thirty-nine consecutive patients with symptomatic AV nodal reentrant tachycardia (AVNRT) underwent temperature guided slow AV nodal pathway ablation (group 1). Forty-three consecutive patients undergoing nontemperature guided slow AV nodal pathway ablation late in our experience compose the control population (group 2). Slow pathway ablation was achieved in all patients of both groups. The mean fluoroscopy and ablation times for group 1 were significantly shorter than for group 2 (26.1 +/- 14.9 vs 33.9 +/- 18.9 min, P < 0.05; 19.9 +/- 12.1 vs 30.9 +/- 23.3 min, P < or = 0.02). There were no episodes of coagulum formation in group 1, while there were 15 episodes (7.1% of energy applications) in group 2 (P = 0.0006) despite a significantly higher applied power in group 1 (53.4 +/- 25.1 vs 35.6 +/- 9.5W, P = 0.0001). Successful energy applications were associated with significantly higher temperatures than unsuccessful applications in group 1 (55.6 degrees +/- 5.8 degrees C vs. 52.9 degrees +/- 6.8 degrees C, P < or = 0.03). The minimum temperature required for successful ablation was 48 degrees C for two patients (5%) and was > or = 50 degrees C for the remainder of patients (37/39 [95%]). The catheter ablation system used in this study was safe, effective, and prevented coagulum formation while delivering relatively high power. In addition, shorter ablation times and radiation exposure were seen with this system. Although successful energy applications and the production of junctional rhythm were associated with higher achieved temperatures, temperature alone did not predict either endpoint. Future prospective, randomized trials are needed to confirm these findings and further evaluate the value of temperature monitoring.

Atrioventricular Node↗
PubMed1997

Diagnostic approach to narrow complex tachycardia with VA block.

Narrow complex tachycardia with VA block is rare. The differential diagnosis usually consists of (1) junctional tachycardia (JT) with retrograde block; (2) AV nodal reentrant tachycardia (AVNRT) with proximal common pathway block; and finally (3) nodofascicular tachycardia using the His-Purkinje system for antegrade conduction and a nodofascicular pathway for retrograde conduction. Analysis of tachycardia onset and termination, the effect of bundle branch block on tachycardia cycle length, and the response to atrial and ventricular premature depolarization must be carefully done. Making the correct diagnosis is crucial as the success rate in eliminating the tachycardia will depend on tachycardia mechanism.

Atrioventricular Node↗
PubMed1997

Electrocardiographic and electrophysiologic characterization of atypical atrial flutter in man: use of activation and entrainment mapping and implications for catheter ablation.

INTRODUCTION: Although the circuit in typical counterclockwise atrial flutter has been clearly delineated, the mechanisms of "atypical atrial flutters" have been less well characterized. The purpose of this study was to investigate the ECG and electrophysiologic (EP) characteristics of atypical atrial flutter. METHODS AND RESULTS: Thirty-three patients with at least one form of atypical atrial flutter underwent EP evaluation with multipolar atrial activation and entrainment mapping. Nineteen patients with clockwise flutter had: (1) stereotypic ECG morphology; (2) same cycle length as counterclockwise flutter; (3) clockwise activation around the tricuspid annulus; (4) recording of discrete split potentials along the length of the crista terminalis, suggesting the presence of conduction block; (5) concealed entrainment from the low right atrial isthmus; (6) successful ablation in this isthmus. Twenty patients with atypical flutter not consistent with a clockwise mechanism ("true atypical flutter") showed: (1) heterogeneous ECG morphology; (2) cycle length shorter than that of clockwise flutter; (3) frequent transitions from and to atrial fibrillation; (4) could be entrained in only six patients and, when accomplished, demonstrated surface fusion when entraining from the low right atrial isthmus. CONCLUSIONS: Atypical flutter falls into two broad categories. Clockwise flutter uses the same circuit with the same endocardial barriers as its counterclockwise counterpart and is best considered a form of typical flutter. True atypical flutter induced in the EP laboratory is a heterogeneous group of arrhythmias that are transitional to atrial fibrillation. Although it may superficially resemble clockwise or counterclockwise flutter based on the 12-lead ECG alone, the distinction can be readily made from a combined evaluation including activation and entrainment mapping.

Adult↗
PubMed1997

Is the Brugada syndrome a distinct clinical entity?

In 1992, Brugada and Brugada described a syndrome characterized by right bundle branch block pattern with ST elevation in leads V1 through V3 and a history of sudden death due to polymorphic ventricular tachycardia or ventricular fibrillation. Since these patients had no evidence of cardiac disease, these findings were ascribed to a distinct clinical entity. Further experience has shown that this same pattern may be mimicked by patients with right ventricular dysplasia, acute ischemia of the right ventricle, other infiltrative cardiomyopathies, as well as tricyclic drug overdose. The pathogenesis of these changes may be due to loss of the dome configuration in the transmembrane potential of right ventricular epicardial cells, which would result in a voltage gradient producing ST elevation. Other explanations involve delayed conduction in a dysplastic right ventricle. The clinical importance of this syndrome is that it calls attention to patients at risk for sudden cardiac death. In addition, these observations have sparked the interest of basic electrophysiologists relative to the relationship of these ECG waveforms and malignant ventricular arrhythmias. Finally, the clinician must exclude other organic diseases before diagnosing this entity.

Anti-Arrhythmia Agents↗
PubMed1996

Mode of onset of torsade de pointes in congenital long QT syndrome.

OBJECTIVES: We sought to describe the mode of onset of spontaneous torsade de pointes in the congenital long QT syndrome. BACKGROUND: Contemporary classifications of the long QT syndrome (LQTS) refer to the congenital LQTS as "adrenergic dependent" and to the acquired LQTS as "pause dependent." Overlap between these two categories has been recognized, and a subgroup of patients with "idiopathic pause-dependent torsade" has been described. However, it is not known how commonly torsade is preceded by pauses in the congenital LQTS. METHODS: We reviewed the electrocardiograms (ECGs) of all our patients with congenital LQTS evaluated for syncope or sudden death (30 patients). Documentation of the onset of torsade de pointes was available for 15 patients. All these patients had "definitive LQTS" by accepted clinical and ECG criteria. RESULTS: Pause-dependent torsade de pointes was clearly documented in 14 of the 15 patients (95% confidence interval 68% to 100%). The cycle length of the pause leading to torsade was 1.3 +/- 0.2 times longer than the basic cycle length, and most pauses leading to torsade were unequivocally longer than the preceding basic cycle length (80% of pauses were > 80 ms longer than the preceding cycle length). CONCLUSIONS: The "long-short" sequence, which has been recognized as a hallmark of torsade de pointes in the acquired LQTS, plays a major role in the genesis of torsade in the congenital LQTS as well. Our findings have important therapeutic implications regarding the use of pacemakers for prevention of torsade in the congenital LQTS.

Adult↗
PubMed1996

Percutaneous multielectrode endocardial mapping during ventricular tachycardia in the swine model.

BACKGROUND: Identification of critical areas within the ventricular tachycardia circuit is a prerequisite for catheter ablation. Currently, mapping during ventricular tachycardia, usually performed with standard catheters, is difficult and time-consuming and can be used only in patients with hemodynamically stable tachycardia. METHODS AND RESULTS: A total of 43 pigs underwent closed-chest induction of myocardial infarction. A basket-shaped catheter carrying 64 electrodes was deployed in the left ventricle during normal sinus rhythm. Unipolar pacing at 3 mA was successful in 78% of the basket catheter electrodes, demonstrating good electrode-tissue contact. Hemodynamic and echocardiographic measurements did not reveal any significant interference with myocardial or valvular function during or after catheter deployment. One hundred eighteen episodes of monomorphic ventricular tachycardia were induced in 28 pigs through right ventricular stimulation, 81 of which were mapped and analyzed. Ventricular tachycardia mapping was rapid, requiring only several beats and < 10 seconds to complete. Presystolic potentials, a possible target for ablation, were identified in 58% of the tachycardia episodes mapped. Pathological examination revealed only minor valvular and endocardial catheter-induced lesions immediately after mapping and none a month later. CONCLUSIONS: The multielectrode catheter enables rapid and safe percutaneous endocardial mapping of ventricular tachycardia in the swine model. Exploration of the clinical potential of the multielectrode catheter seems warranted.

Animals↗
PubMed1996

Results of radiofrequency catheter ablation for atrial flutter.

RF catheter ablation for symptomatic typical atrial flutter is associated with a high procedural success rate, but a second RF procedure may be required in up to one third of subjects, particularly those with right atrial enlargement. In those subjects with both established AF and flutter, RF ablation for atrial flutter may decrease the recurrence rate of AF. However, patients remain at risk for the development of newly documented AF, most likely secondary to the high incidence of underlying structural heart disease.

Aged↗
PubMed1996

Intravenous amiodarone for recurrent sustained hypotensive ventricular tachyarrhythmias. Intravenous Amiodarone Multicenter Trial Group.

OBJECTIVES: We sought to determine the response rate and safety of intravenous amiodarone in patients with ventricular tachyarrhythmias refractory to standard therapies. BACKGROUND: Numerous small retrospective reports suggest a response of refractory ventricular tachyarrhythmias to intravenous amiodarone, yet no controlled prospective trials exist. METHODS: Two hundred seventy-three patients with recurrent hypotensive ventricular tachyarrhythmias refractory to lidocaine, procainamide and bretylium were randomized to receive one of three doses of intravenous amiodarone: 525, 1,050 or 2,100 mg/24 h (mean [+/- SE] dose 743.7 +/- 418.7, 1,175.2 +/- 483.7, 1,921.2 +/- 688.8 mg, respectively) by continuous infusion over 24 h. RESULTS: Of the 273 patients, 110 (40.3% response rate) survived 24 h without another hypotensive ventricular tachyarrhythmic event while being treated with intravenous amiodarone as a single agent (primary end point). A significant difference in the time to first recurrence of ventricular tachyarrhythmia (post hoc analysis) over the first 12 h was observed when the combined 1,050- and 2,100-mg dose groups were compared with the 525-mg dose group (p = 0.046). The number of supplemental (150 mg) infusions of intravenous amiodarone (given for breakthrough destabilizing tachyarrhythmias) during hours 0 to 6 (prespecified secondary end point) was significantly greater in the 525-mg dose group than in the 2,100-mg dose group (1.09 +/- 1.57 vs. 0.51 +/- 0.97, p = 0.0043). However, there was no clear dose-response relation observed in this trial with respect to success rates (primary end point), time to first recurrence of tachyarrhythmia (post hoc analysis) or mortality (secondary end point) over 24 h. CONCLUSIONS: Intravenous amiodarone is a relatively safe therapy for ventricular tachyarrhythmias refractory to other medications.

Amiodarone↗
PubMed1996

Long-term results of electrophysiologically guided sotalol therapy for life-threatening ventricular arrhythmias.

The efficacy and safety of sotalol therapy for ventricular arrhythmias was evaluated in 133 patients with drug-refractory ventricular arrhythmias. All patients had baseline electrophysiologic studies before and after oral sotalol therapy. Sixty-six patients were discharged home, treated with sotalol (52 patients without inducible ventricular tachycardia or fibrillation and 14 patients with hemodynamically stable inducible ventricular tachycardia). The mean follow-up period was 41 +/- 27 months for the 14 patients with hemodynamically stable ventricular tachycardia. Sotalol was effective in 8 of these 14 patients. Recurrent nonlethal ventricular tachycardia occurred in 3 patients; 2 patients had sudden death; and 1 patient had adverse side effects. The 52 patients without inducible ventricular tachycardia were followed up for a mean period of 36 +/- 30 months. Thirty-five of 52 patients were successfully treated. Two patients had recurrent ventricular tachycardia; both of these episodes of ventricular tachycardia occurred within the first year. Four patients had sudden cardiac death; three of these deaths occurred within the first month, and the last episode of sudden death occurred after 8 years of sotalol therapy. The actuarial incidence of sotalol efficacy was 76% at 1 year, 72% at 2 years, 64% at 4 years, and 52% at 5 years. Approximately 46% of patients receiving long-term sotalol treatment reported side effects. Side effects severe enough to warrant withdrawal of sotalol occurred in 7 (11%) patients. The results of our study suggest that sotalol is effective for selected patients with drug refractory ventricular arrhythmias. Although the incidence of side effects are high, patients appear to tolerate long-term sotalol therapy well.

Adult↗
PubMed1996

Quality of life and outcomes after radiofrequency His-bundle catheter ablation and permanent pacemaker implantation: impact of treatment in paroxysmal and established atrial fibrillation.

One hundred seven patients underwent atrioventricular (AV)-junctional ablation and pacing for atrial fibrillation, and 90 were alive 2.3 +/- 1.2 years later. Quality of life index (1.9 +/- 1.2 to 3.6 +/- 1.1; 3.6 +/- 1.1; p<0.001) and ease of activities of daily living (2 +/- 0.4 to 2.4 +/- 0.3; p<0.001) were significantly improved. Doctor visits (10 +/- 13 to 5.06 +/-7; p<0.03), hospital admissions (2.8 +/- 6.8 vs 0.17 +/- 0.54; p<0.03, and antiarrhythmic drug trials (6.2 +/- 4 to 0.46 +/- 1.5; p<0.001) decreased significantly after treatment. Congestive heart failure episodes decreased from 18 before to 8 afterward. Twenty-eight of 36 patients with dual-chamber pacemakers remained in a dual-chamber mode at follow-up. Radiofrequency AV-junctional catheter ablation and pacing is a highly successful form of treatment for medically refractory atrial fibrillation.

Activities of Daily Living↗
PubMed1996

Factors associated with cognitive recovery after cardiopulmonary resuscitation.

BACKGROUND: A range of neuro-cognitive sequelae, from mild intellectual impairments to brain death, have been reported in survivors of aborted sudden cardiac death. PURPOSE: To determine to what extent, if any, factors associated with cardiopulmonary resuscitation, left ventricular function, and mood state are related to outcomes in five cognitive areas, namely orientation, attention, memory, reasoning, and motor performance. METHODS: Repeated measures were used to assess cognitive outcomes in 45 sudden cardiac arrest survivors over the 6 months following cardiopulmonary resuscitation. A battery of neuro-psychological tests was used to assess cognitive outcomes and psychological status over time. The relationship of the cardiopulmonary resuscitation, left ventricular function, and psychological variables to cognitive outcomes were assessed at each data point. The independent variables included time to cardiopulmonary resuscitation, time to defibrillation, duration of cardiopulmonary resuscitation, time to awakening, ejection fraction, New York Heart Association Class I to IV, tension, anger, and depression. RESULTS: During hospitalization 38 of the 45 survivors (84%) had mild to severe deficits in one or more cognitive areas; 19 of 38 survivors (50%) continued to be impaired in one or more cognitive areas at 6 months. Of these, all had mild to severe deficits in at least one aspect of memory, with delayed recall the most frequent impairment. Time to awakening accounted for a unique portion of the variance in orientation and memory outcomes over time. The left ventricular function variables accounted for a significant portion of the variance in motor speed. CONCLUSIONS: Our results suggest that half of the long-term survivors of aborted sudden cardiac death are cognitively intact 6 months after resuscitation but that 25% have moderate to severe impairment in memory, which could hamper and/or preclude the resumption of prearrest roles.

Analysis of Variance↗
PubMed1995

Randomized, double-blind comparison of intravenous amiodarone and bretylium in the treatment of patients with recurrent, hemodynamically destabilizing ventricular tachycardia or fibrillation. The Intravenous Amiodarone Multicenter Investigators Group.

BACKGROUND: After several days of loading, oral amiodarone, a class III antiarrhythmic, is highly effective in controlling ventricular tachyarrhythmias; however, the delay in onset of activity is not acceptable in patients with immediately life-threatening arrhythmias. Therefore, an intravenous form of therapy is advantageous. This study was designed to compare the safety and efficacy of a high and a low dose of intravenous amiodarone with bretylium, the only approved class III antiarrhythmic agent. METHODS AND RESULTS: A total of 302 patients with refractory, hemodynamically destabilizing ventricular tachycardia or ventricular fibrillation were enrolled in this double-blind trial at 82 medical centers in the United States. They were randomly assigned to therapy with intravenous bretylium (4.7 g) or intravenous amiodarone administered in a high dose (1.8 g) or a low dose (0.2 g). The primary analysis, arrhythmia event rate during the first 48 hours of therapy, showed comparable efficacy between the bretylium group and the high-dose (1000 mg/24 h) amiodarone group that was greater than that of the low-dose (125 mg/24 h) amiodarone group. Similar results were obtained in the secondary analyses of time to first event and the proportion of patients requiring supplemental infusions. Overall mortality in the 48-hour double-blind period was 13.6% and was not significantly different among the three treatment groups. Significantly more patients treated with bretylium had hypotension compared with the two amiodarone groups. More patients remained on the 1000-mg amiodarone regimen than on the other regimens. CONCLUSIONS: Bretylium and amiodarone appear to have comparable efficacies for the treatment of highly malignant ventricular arrhythmias. Bretylium use, however, may be limited by a high incidence of hypotension.

Aged↗
PubMed1995

Dose-ranging study of intravenous amiodarone in patients with life-threatening ventricular tachyarrhythmias. The Intravenous Amiodarone Multicenter Investigators Group.

BACKGROUND: Oral amiodarone effectively suppresses ventricular arrhythmias; however, full activity may take days or weeks. In patients with frequent, life-threatening ventricular arrhythmias, this delay is not acceptable. Thus, in these patients, the speed and dosing accuracy of an intravenous formulation would be beneficial. The goal of this study was to demonstrate the efficacy of intravenous amiodarone in patients with refractory, recurrent hemodynamically destabilizing ventricular tachycardia or ventricular fibrillation by determining a dose response among three regimens. METHODS AND RESULTS: A total of 342 patients were enrolled at 46 medical centers in the United States. Patients received one of three randomized, double-blind dose regimens delivering 125, 500, or 1000 mg during the first 24 hours. Supplemental infusions (150 mg) of intravenous amiodarone could be given to treat breakthrough ventricular arrhythmias. The key efficacy end points were the arrhythmia event rate, time to first arrhythmic event, and number of supplemental infusions administered. The event rate decreased with increasing doses: median values were 0.07, 0.04, and 0.02 events per hour for the 125-, 500-, and 1000-mg dose groups, respectively, representing a significant decrease from baseline event rates (P = .043), and approached significance in the overall test for trend (P = .067). There was a significant dose-related increase in the time to first event (trend test P = .025) and a significant dose-related decrease in the number of supplemental boluses per hour (trend test P = .043). Hypotension was the most common (26%) treatment-emergent adverse event during intravenous amiodarone therapy; there was no dose-response relationship. Seventy-eight percent of the patients survived to at least 48 hours. CONCLUSIONS: Intravenous amiodarone is effective for the treatment of recurrent, life-threatening ventricular tachyarrhythmias.

Amiodarone↗
PubMed1995

Radiofrequency catheter modification of the sinus node for "inappropriate" sinus tachycardia.

BACKGROUND: Radiofrequency catheter ablation is the treatment of choice for patients with paroxysmal supraventricular tachycardias refractory to medical therapy. However, in symptomatic patients with inappropriate sinus tachycardia resistant to drug therapy, catheter ablation of the His' bundle with permanent pacemaker insertion is currently applied. We evaluated the safety and efficacy of radiofrequency modification of the sinus node as alternative therapy for patients with inappropriate sinus tachycardia. METHODS AND RESULTS: Sixteen patients with disabling episodes of inappropriate sinus tachycardia refractory to drug therapy (4.2 +/- 0.3 drug trials) underwent either total sinus node ablation or sinus node modification. The region of the sinus node was identified as the region of earliest atrial activation in sinus rhythm during electrophysiological study. This region was further defined by use of intracardiac echocardiography (ICE) in 9 patients, in whom it was found that an ablation catheter could be guided reliably and maintained on the crista terminalis. Radiofrequency energy was delivered during tachycardia between either a standard 4-mm or custom 10-mm thermistor-imbedded catheter tip and a skin patch. Total sinus node ablation was performed successfully in all 4 patients in whom it was attempted and was characterized by a junctional escape rhythm. Sinus node modification was successfully achieved in all 12 patients in whom it was attempted and was characterized by a 25% reduction in the sinus heart rate. For the group as a whole, exercise stress testing after ablation revealed a gradual chronotropic response, with a significant reduction in maximal heart rate (132.8 +/- 6.5 versus 179.5 +/- 3.6 beats per minute [bpm]; P < .001) without evidence of an exaggerated heart rate response to a light workload (103.0 +/- 4.1 versus 139.5 +/- 3.5 bpm; P < .001). Twenty-four-hour ambulatory ECG monitoring revealed a significant decrease in maximal heart rate and mean heart rate after ablation (167.2 +/- 2.6 versus 96.7 +/- 5.0 bpm, P < .001, and 125.6 +/- 5.0 versus 54.1 +/- 5.3 bpm, P < .001, respectively). There was a significant decrease in the number of applications of radiofrequency energy required in patients undergoing modification of the sinus node when guided by ICE compared with fluoroscopy alone (3.6 +/- 0.8 versus 10.4 +/- 2.1; P < .01) as well as a decrease in fluoroscopy time (33.0 +/- 9.5 versus 58.5 +/- 8.4 minutes). After a mean follow-up period of 20.5 +/- 0.3 months, there were no recurrences of inappropriate sinus tachycardia in patients who underwent a total sinus node ablation. However, 2 patients who had a total sinus node ablation subsequently required permanent pacing because of symptomatic pauses, and 1 patient developed an ectopic atrial tachycardia. After a mean follow-up of 7.1 +/- 1.7 months, there were two recurrences of inappropriate sinus tachycardia in patients who underwent sinus node modification. However, no significant bradycardia or pauses were observed. Complications encountered during the study included 1 patient who developed transient right diaphragmatic paralysis and another patient who developed transient superior vena cava syndrome. CONCLUSIONS: Sinus node modification is feasible in humans and should be considered as an alternative to complete atrioventricular junctional ablation for patients with disabling inappropriate sinus tachycardia refractory to medical management. Sinus node modification may be aided by ICE.

Adult↗
PubMed1995

Radiofrequency catheter modification of sinus pacemaker function guided by intracardiac echocardiography.

BACKGROUND: The sinus P wave arises from a pacemaker complex distributed along the crista terminalis. We investigated the feasibility of modification of sinus pacemaker function using graded applications of radiofrequency energy along the crista terminalis in dogs to achieve sinus rate control. METHODS AND RESULTS: Modification of sinus pacemaker function (30 +/- 5% reduction in intrinsic heart rate with retention of a normal P-wave axis) was performed in 11 dogs (group 1). Total sinus pacemaker ablation (> 50% reduction in intrinsic heart rate with development of a low ectopic atrial or a junctional rhythm) was performed in 4 dogs (group 2). Intracardiac echocardiography was used to identify the crista terminalis as an anatomic marker of sinus node location. Sinus pacemaker modification caused a significant decrease in intrinsic heart rate (31% reduction, P < .001), heart rate responsiveness to isoproterenol (30% reduction, P < .0001), and average (20% reduction, P = .0002) and maximal (22% reduction, P = .0007) heart rates during 24-hour Holter monitoring. In 6 of the 11 animals, the targeted rate reduction of 30 +/- 5% was accurately achieved (mean, 31.6 +/- 4.3%; P < .001), and in the other 5, significant reduction of intrinsic heart rate was achieved but with greater variation (28.0 +/- 17.3%, P < .005). Corrected sinus node recovery time was not prolonged. After modification, earliest activation was mapped to the crista terminalis inferior to the lesion in all animals. In long-term follow-up (3.7 +/- 1.0 months), effects were maintained. After total sinus pacemaker ablation, junctional and low atrial escape pacemakers were unstable. CONCLUSIONS: This study demonstrates the feasibility of modification of sinus pacemaker function for sinus rate control using catheter-based radiofrequency ablation guided by intracardiac echocardiography. This can be done while pacemaker stability and attenuated responsiveness to autonomic influences are preserved. Intracardiac echocardiography accurately defined the crista terminalis and provided a reliable means to anatomically localize catheter position in relation to the sinus node.

Animals↗