Elevated circulating levels of tumor necrosis factor in severe chronic heart failure

BACKGROUND AND METHODS

Although cachexia often accompanies advanced heart failure, little is known about the causes of the cachectic state. To assess the potential role of tumor necrosis factor in the pathogenesis of cardiac cachexia, we measured serum levels of the factor in 33 patients with chronic heart failure, 33 age-matched healthy controls, and 9 patients with chronic renal failure.

RESULTS

Mean (+/- SEM) serum levels of tumor necrosis factor were higher in the patients with heart failure (115 +/- 25 U per milliliter) than in the healthy controls (9 +/- 3 U per milliliter; P less than 0.001). Nineteen of the patients with chronic heart failure had serum levels of tumor necrosis factor greater than or equal to 39 U per milliliter (greater than 2 SD above the mean value for the control group), whereas the remaining 14 patients had serum levels of tumor necrosis factor below this level. The patients with high levels of tumor necrosis factor were more cachectic than those with low levels (82 +/- 3 vs. 95 +/- 6 percent of ideal body weight, respectively; P less than 0.05) and had more advanced heart failure, as evidenced by their higher values for plasma renin activity (2.92 +/- 0.53 vs. 1.06 +/- 0.53 ng per liter per second [10.5 +/- 1.9 vs. 3.8 +/- 1.9 ng per milliliter per hour]; P less than 0.01) and lower serum sodium concentration (135 +/- 1 vs. 138 +/- 1 mmol per liter; P less than 0.05). The group with high levels of tumor necrosis factor also had lower hemoglobin levels (7.82 +/- 0.2 vs. 8.69 +/- 0.4 mmol per liter [12.6 +/- 0.4 vs. 14.0 +/- 0.6 g per deciliter]) and higher values for blood urea nitrogen (19.5 +/- 2.2 vs. 12.5 +/- 1.8 mmol per liter) than the group with low levels of tumor necrosis factor (P less than 0.05 for both). The high levels of tumor necrosis factor were not due solely to decreased renal clearance, however, since the levels in the patients with heart failure were considerably higher than those in the nine patients with chronic renal failure (115 +/- 25 vs. 45 +/- 25 U per milliliter; P less than 0.05).

CONCLUSIONS

These findings indicate that circulating levels of tumor necrosis factor are increased in cachectic patients with chronic heart failure and that this elevation is associated with the marked activation of the renin-angiotensin system seen in patients with end-stage cardiac disease.

Elevated circulating tumor necrosis factor levels in Alzheimer's disease

Recent investigations have demonstrated a local inflammatory response in Alzheimer's disease (AD), including microglia and cytokines. Levels of the cytokine tumor necrosis factor alpha (TNF-alpha) in sera from patients with AD and age-matched controls were measured by an enzyme-linked immunoassay and a cytotoxicity bioassay. Significantly elevated levels of TNF were found in AD sera compared to controls. Elevated circulating TNF may be derived from the local CNS inflammatory reaction in AD, and may account for some systemic manifestations of AD such as weight loss. Future studies may determine if, in the absence of complicating disorders which may elevate TNF, circulating TNF could be a marker of AD inflammatory activity.

Role of right atrial endocardial structures as barriers to conduction during human type I atrial flutter. Activation and entrainment mapping guided by intracardiac echocardiography

BACKGROUND

The importance of barriers in atrial flutter has been demonstrated in animals. We used activation and entrainment mapping, guided by intracardiac echocardiography (ICE), to determine whether the crista terminalis (CT) and eustachian ridge (ER) are barriers to conduction during typical atrial flutter in humans.

METHODS AND RESULTS

In eight patients, ICE was used to guide the placement of 20-pole and octapolar catheters along the CT and interatrial septum and a roving catheter to nine sites: just posterior (1) and anterior (2) to the CT along the lateral right atrium, at the fossa ovalis (3), and just posterior and anterior to the ER at the low posterolateral (4 and 5), low posterior (6 and 7), and low posteromedial (8 and 9) right atrium. Entrainment was performed, and each site was considered within the flutter circuit if the postpacing interval-flutter cycle length (PPI-FCL) and the stimulus time-activation time (stim time-act time) were < 10 msec. Split potentials were recorded along the CT with components activated in a low-to-high pattern and a high-to-low pattern. Conduction times, as percentage of FCL, were significantly different at sites on either side of the CT and ER: site 1 (33 +/- 13%) and site 2 (43 +/- 12%) (P = .02), site 4 (48 +/- 24%) and site 5 (75 +/- 8.9%) (P = .02), and site 6 (22 +/- 10%) and site 7 (82 +/- 5.3%) (P = .0009). During entrainment, no surface fusion was observed at sites 5, 7, or 9. The PPI-FCL and stim time-act time were not significantly different than 0 at sites 2, 7, 5, or 9, indicating that they were within the flutter circuit, whereas sites 1, 3, 4, and 6 were not.

CONCLUSIONS

ICE enabled the correlation of functional electrophysiological properties with specific anatomic landmarks, identifying the CT and ER as barriers to conduction during human atrial flutter.

Atrial fibrillation after coronary artery bypass grafting is associated with sympathetic activation

BACKGROUND

We prospectively investigated the role of sympathetic activation in the etiology of atrial fibrillation following coronary artery bypass grafting.

METHODS

Continuous ambulatory monitoring was performed for 80 hours in 131 patients after coronary artery bypass grafting. Right atrial plasma norepinephrine levels were assessed preoperatively and every 4 hours for 48 hours postoperatively.

RESULTS

Of the 131 patients, 50% (65) had development of atrial fibrillation and 36% (47) required treatment. Onset of atrial fibrillation was preceded by a significant increase in sinus rate and atrial ectopic activity. On multivariate logistic regression, elevated mean postoperative norepinephrine levels (5.78 +/- 2.83 versus 3.57 +/- 1.31 nmol/L; p < 0.0001), increased age (68.9 +/- 5.7 versus 63.8 +/- 8.7 years; p = 0.02), and decreased postoperative magnesium levels (0.79 +/- 0.09 versus 0.83 +/- 0.10 mmol/L; p = 0.02) were independently associated with the occurrence of atrial fibrillation.

CONCLUSIONS

Elevated norepinephrine levels suggest that sympathetic activation may be important in the pathogenesis of atrial fibrillation after coronary artery bypass grafting, and this underlines the importance of beta-adrenoceptor blockade as prophylaxis.

Ablation of 'incisional' reentrant atrial tachycardia complicating surgery for congenital heart disease. Use of entrainment to define a critical isthmus of conduction

BACKGROUND

Intra-atrial reentrant tachycardia occurs frequently after surgery for congenital heart disease and is difficult to treat. We tested the hypotheses that intra-atrial reentrant tachycardia in patients who had undergone prior reparative surgery for congenital heart disease could be successfully ablated by targeting a protected isthmus of conduction bounded by natural and surgically created barriers and that entrainment techniques could be used to identify these zones.

METHODS AND RESULTS

Eighteen consecutive patients with 26 intra-atrial reentrant tachycardias complicating surgery for congenital heart disease (9 atrial septal defect repair, 4 Fontan, 2 Mustard, 2 Senning, and 1 Rastelli procedure) underwent electrophysiological study and ablation attempts. Mapping of activation was facilitated by the deployment of catheters with multiple electrodes. Sites for ablation were sought that demonstrated entrainment with concealed fusion and at which the postpacing interval minus the tachycardia cycle length and the stimulus to P wave minus the activation time were < 30 ms. These sites were considered to be within a narrow isthmus critical to the tachycardia mechanism. Anatomic barriers bordering the critical isthmus of conduction were identified on anatomic grounds, by the presence of areas of electrical silence or by the demonstration of split potentials signifying a line of block. Success was achieved in 15 patients with 21 arrhythmias. The median number of radiofrequency applications was 5. There was a wide range of activation times at successful sites (-30 to -250 ms). At a mean duration of follow-up of 17 +/- 8 months, 11 patients were asymptomatic and 9 did not require antiarrhythmia therapy.

CONCLUSIONS

Successful ablation of intra-atrial reentrant tachycardia complicating surgery for congenital heart disease may be achieved by creation of an ablative lesion in a critical isthmus of conduction bounded by anatomic barriers. This isthmus may be identified by the presence of entrainment with concealed fusion and an analysis of the relationship between the postpacing interval and the tachycardia cycle length and between the activation time and the stimulus time. Because this isthmus is invariably confined on at least one aspect by a surgical repair site that is of central importance to the tachycardia mechanism, we suggest that this type of arrhythmia be given the descriptive designation of "incisional reentry."

"Cristal tachycardias": origin of right atrial tachycardias from the crista terminalis identified by intracardiac echocardiography

OBJECTIVES

We sought to use intracardiac echocardiography (ICE) to identify the anatomic origin of focal right atrial tachycardias and to define their relation with the crista terminalis (CT).

BACKGROUND

Previous studies using ICE during mapping of atrial flutter and inappropriate sinus tachycardia have demonstrated an important relation between endocardial anatomy and electrophysiologic events. Recent studies have suggested that right atrial tachycardias may also have a characteristic anatomic distribution.

METHODS

Twenty-three consecutive patients with 27 right atrial tachycardias were included in the study. ICE was used to facilitate activation mapping in relation to endocardial structures. A 20-pole catheter was positioned along the CT under ICE guidance. ICE was also used to assist in guiding detailed mapping with the ablation catheter in the right atrium.

RESULTS

Of 27 focal right atrial tachycardias, 18 (67%, 95% confidence interval [CI] 46% to 83%) were on the CT (2 high medial, 8 high lateral, 6 mid and 2 low). ICE identified the location of the tip of the ablation catheter in immediate relation to the CT in all 18 cases. The 20-pole mapping catheter together with echocardiographic visualization of the CT provided a guide to the site of tachycardia origin along this structure. Radiofrequency ablation was successful in 26 (96%) of 27 (95% CI 81% to 100%) right atrial tachycardias.

CONCLUSIONS

This study demonstrates that approximately two thirds of focal right atrial tachycardias occurring in the absence of structural heart disease will arise along the CT. Recognition of this common distribution may potentially facilitate mapping and ablation of these tachycardias.

Activation and entrainment mapping defines the tricuspid annulus as the anterior barrier in typical atrial flutter

BACKGROUND

The importance of anatomic barriers in the atrial flutter reentry circuit has been well demonstrated in canine models. It has been shown previously that the crista terminalis and its continuation as the eustachian ridge form a posterior barrier. In this study we tested the hypothesis that the tricuspid annulus forms the continuous anterior barrier to the flutter circuit.

METHODS AND RESULTS

Thirteen patients with typical atrial flutter were studied. A 20-pole halo catheter was situated around the tricuspid annulus. A mapping catheter was used for activation and entrainment mapping from seven sequential sites around the tricuspid annulus and from three additional sites including the tip of the right atrial appendage, at the fossa ovalis, and in the distal coronary sinus. Sites were considered to be within the circuit when the postpacing interval minus the flutter cycle length and the stimulus time minus the activation time were < or = 10 ms; sites were considered to be outside the circuit when these intervals were > 10 ms. All seven annular sites were within the circuit; activation occurred sequentially around the annulus and accounted for 100% of the flutter cycle length. The fossa ovalis, the distal coronary sinus, and the right atrial appendage were outside the circuit.

CONCLUSIONS

Closely spaced sites around the tricuspid annulus are activated sequentially, and are all within the flutter circuit according to entrainment criteria. This demonstrates that the tricuspid annulus constitutes a continuous anterior barrier constraining the reentrant wave front of human counterclockwise atrial flutter.

Prospective, randomized comparison of effect of long-term treatment with metoprolol or carvedilol on symptoms, exercise, ejection fraction, and oxidative stress in heart failure

BACKGROUND

With beta-blocker use becoming more prevalent in treating chronic heart failure (CHF), the choice of drugs raises important theoretical and practical questions. Although the second-generation compound metoprolol is beta1-selective, the third-generation compound carvedilol is beta-nonselective, with ancillary pharmacological properties including alpha-blockade and antioxidant effects. A prospective comparison of these 2 agents can address the issue of optimal adrenergic blockade in selecting agents for therapy in CHF.

METHODS AND RESULTS

Sixty-seven patients with symptomatic stable heart failure were randomly assigned to receive either carvedilol or metoprolol in addition to standard therapy for CHF. Measured variables included symptoms, exercise, ejection fraction, and thiobarbituric acid-reactive substances (TBARS) as an indirect marker of free radical activity. Metoprolol and carvedilol were well tolerated, and both patient groups showed beneficial effects of beta-blocker therapy in each of the measured parameters, with no between-group differences. Ejection fraction increased over 6 months from 18+/-6.3% to 23+/-8.7% (P<0.005) with metoprolol and from 19+/-8.5% to 25+/-9.9% (P<0.0005) with carvedilol (P=NS between groups). With metoprolol, TBARS values decreased from 4.7+/-0.9 nmol/mL at baseline to 4.2+/-1.5 nmol/mL at month 4 to 3.9+/-1.0 nmol/mL at month 6 (P<0.0001). With carvedilol, there was a parallel decline from 4.7+/-1.4 to 4.2+/-1.3 to 4.1+/-1.2 nmol/mL over the same time frame (P<0.025), with no between-group difference in these changes.

CONCLUSIONS

Carvedilol and metoprolol showed parallel beneficial effects in the measured parameters over 6 months, with no relevant between-group differences in this heart failure population.

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.

Focal atrial tachycardia arising from the tricuspid annulus: electrophysiologic and electrocardiographic characteristics

INTRODUCTION

Focal right atrial tachycardia (RAT) arising from the crista terminalis, para-Hisian, and coronary sinus os regions are well described. Less information exists regarding RAT arising from the nonseptal region of the tricuspid annulus (TA).

METHODS AND RESULTS

From a consecutive series of 64 patients who had undergone successful radiofrequency ablation (RFA) of 67 RATs, the characteristics of 9 (13%) patients (6 men; mean age 50 +/- 20 years) with a TA focus were reviewed. The annular focus was localized to the inferoanterior TA in 7 and the superior TA in 2. Mean tachycardia cycle length was 371 +/- 66 msec. Mean activation time at the site of successful RFA in 9 of 9 patients was -43 +/- 11 msec. At 9.3 +/- 5.6 months of follow-up, 1 of 9 patients had recurrent tachycardia successfully treated with repeat RFA. In 7 of 9 patients with RAT from the inferoanterior TA, the surface ECG P wave morphology was upright in aVL, inverted in III and VI, and either inverted or biphasic with an initial negative deflection from V2 to V6.

CONCLUSION

The TA is an important site of origin of RAT. In the present study, the inferoanterior region of the TA was a preferential site of origin with resulting characteristic P wave morphology. Knowledge of this anatomic distribution and P wave morphology allows targeted mapping and may facilitate successful RFA.

Intracardiac echocardiography during radiofrequency catheter ablation of cardiac arrhythmias in humans

OBJECTIVES

The purpose of this study was to describe our preliminary experience using catheter-based intracardiac echocardiography as an adjunct to biplane fluoroscopy for guiding radiofrequency catheter ablation of atrial arrhythmias in the right side of the heart.

BACKGROUND

Catheter ablation requires precise positioning and stable ablation electrode-endocardial contact. This procedure is currently guided by an analysis of intracardiac electrograms and fluoroscopy. However, the use of fluoroscopy does not allow the endocardium and certain anatomic landmarks to be identified and is associated with the hazards of radiation exposure.

METHODS

Seventeen symptomatic patients were studied. A 10F 10-MHz intracardiac imaging catheter was used to visualize specific anatomic landmarks in the right atrium for directing the ablation electrode in 15 patients undergoing radiofrequency ablation of 19 arrhythmias and to assist with interatrial septal puncture in 3 patients.

RESULTS

Continuous intracardiac imaging was performed for a mean +/- SD of 63.6 +/- 39.2 min and demonstrated distal electrode-endocardial tissue contact in 81 (60%) of 134 radiofrequency applications. Movement of the catheter was demonstrated during 36 (44%), microcavitations during 39 (48%) and thrombus during 15 (19%) of the 81 imaged applications. In 7 of 10 procedures for atrial flutter, successful ablation was directed at anatomic corridors in the right atrium visualized with intracardiac echocardiography. During ablation of atrial tachycardia, imaging identified abnormal atrial anatomy related to previous surgery and guided successful ablation of a reentrant tachycardia circulating around these anatomic obstacles. In two procedures for slow pathway modification of atrioventricular node reentrant tachycardia, intracardiac echocardiography confirmed catheter stability at the tricuspid annulus anterior to the coronary sinus.

CONCLUSIONS

During catheter ablation, intracardiac echocardiography augments fluoroscopy by visualizing anatomic landmarks, ensuring stable endocardial contact and assisting in transseptal puncture. Ablation of typical atrial flutter can be successfully directed at anatomic corridors identified using intracardiac imaging.

Acute effects of intraoperative multisite ventricular pacing on left ventricular function and activation/contraction sequence in patients with depressed ventricular function

INTRODUCTION

We hypothesized that simultaneous right and left ventricular apical pacing would result in improvement in left ventricular function due to improved coordination of segmental ventricular contraction. Structural changes in ventricular muscle present in dilated cardiomyopathy compromise ventricular excitation and mechanical contraction.

METHODS AND RESULTS

Eleven patients with depressed left ventricular function having cardiac surgery underwent epicardial multisite pacing with continuous transesophageal echocardiographic imaging. Quantitative measurement of percent fractional area change was performed, and segmental changes in contraction sequence resulting from simultaneous right and left ventricular pacing were assessed by application of phase analysis to recorded transesophageal images. There was no statistically significant difference between the paced QRS duration achieved with simultaneous right and left ventricular apical pacing and the native QRS duration (139+/-39 msec vs 106+/-18 msec, P = NS), but all other paced modes resulted in longer QRS durations. Percent fractional area change improved with simultaneous right and left ventricular apical pacing but not with other paced modes (41.5+/-11.9 vs 34.3+/-9.7, P < 0.01). Phase analysis demonstrated a resequencing of segmental left ventricular activation/contraction when compared to baseline ventricular activation.

CONCLUSION

Simultaneous right and left ventricular apical pacing results in acute improvements in global ventricular performance in patients with depressed ventricular function. Improvements may result from pacing-induced global coordination through recruitment of left and right ventricular apical and septal segments critical to effective ventricular contraction.

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.

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.

Electrical remodeling of the atria associated with paroxysmal and chronic atrial flutter

BACKGROUND

Atrial electrical remodeling may be important for the initiation and perpetuation of atrial arrhythmias. Whether paroxysmal atrial flutter (AFL) and chronic AFL cause electrical remodeling of the atria has not been conclusively determined.

METHODS AND RESULTS

Before radiofrequency ablation of paroxysmal AFL, 15 patients in sinus rhythm were evaluated under autonomic blockade. Lateral right atrial (LRA) effective refractory periods (ERPs) at 600 and 450 ms were measured before and at 1-minute intervals for 10 minutes after spontaneous or pace termination of a 5- to 10-minute period of induced AFL. In 10 patients with chronic AFL, LRA, septal, and coronary sinus (CS) ERPs and corrected sinus node recovery times (cSNRTs) at 600 and 450 ms were measured under autonomic blockade 15 minutes, 30 minutes, and 3 weeks after termination of chronic AFL by ablation. In the paroxysmal AFL group, LRA ERPs decreased by 18% at 600 ms and 12% at 450 ms (P:<0.01) after induced AFL and recovered to baseline over approximately 5 minutes. Atrial fibrillation developed during AFL in 3 patients and during ERP testing in 3 patients when refractoriness was at its nadir. In the chronic AFL group, LRA, septal, and CS ERPs at 3 weeks were significantly greater than at 15 and 30 minutes after termination of chronic AFL at both cycle lengths (P:<0.01). Three weeks after ablation, cSNRT decreased 35% at 600 ms (P:<0.05) and decreased 44% at 450 ms (P:<0. 05). Both ERPs and cSNRTs measured 15 and 30 minutes after ablation of chronic AFL were not significantly different.

CONCLUSIONS

Both paroxysmal AFL and chronic AFL cause reversible electrical remodeling of the atria but demonstrate different time courses of recovery.

Conduction barriers in human atrial flutter: correlation of electrophysiology and anatomy

Animal models of atrial flutter and early mapping studies of human atrial flutter have suggested the importance of barriers in this reentrant arrhythmia. The consistency of rate and morphology of typical atrial flutter suggest a common anatomic substrate for this arrhythmia. The unique endocardial architecture of the right atrium provides anatomic barriers around which reentry occurs. In typical human atrial flutter, the crista terminalis, eustachian ridge, and tricuspid annulus have been identified as barriers to conduction. The importance of conduction barriers, methodology for defining barriers, the anatomic substrate for these barriers, and the role of these barriers in other atrial arrhythmias are discussed.

Electrophysiological effects of long, linear atrial lesions placed under intracardiac ultrasound guidance

BACKGROUND

A curative atrial fibrillation procedure will most likely rely on creating transmural linear ablative lesions. However, it is currently unknown whether endocardial radiofrequency lesions can create lines of conduction block.

METHODS AND RESULTS

In six pigs, intracardiac echocardiography was used to guide the positioning of multiple coil array catheters to bridge endocardial structures in three right atrial locations: (1) from the crista terminalis to the tricuspid annulus; (2) from the fossa ovalis to the crista terminalis; and (3) from the inferior vena cava to the tricuspid annulus. Once the catheter was positioned, linear lesions were made by radiofrequency energy applied sequentially to each of the four coils. After 15 days, the chest was opened and a 112-electrode epicardial plaque was positioned over the atrial free wall lesion to determine activation patterns. Three lesions were placed in each animal, with a mean procedure time of 47+/-11 minutes. Once adequate contact was determined by intracardiac echocardiography, a single series of radiofrequency application was required to achieve tissue heating (65+/-4 degrees C) with a power of 21+/-10 W. Epicardial mapping demonstrated complete conduction block across the lesions in all animals, with split potentials and disparate activation times (64+/-16 ms) across the lesion. At autopsy, all lesions were discrete, continuous, and without evidence of charring. The lesions were within 0.3+/-0.5 mm of their targeted anatomic locations and measured 21+/-4 mm long and 2.8+/-0.6 mm wide. Histology revealed transmural fibrosis throughout the length of each lesion.

CONCLUSIONS

Linear lesions that are electrophysiologically transmural and continuous can be placed in the right atrium of normal pigs. With intracardiac echocardiography, adequate tissue contact over several coil electrodes can be ensured, resulting in short procedure times, efficient energy application, and accurate anatomically linked lesion placement.

Electrical remodeling of the atria following loss of atrioventricular synchrony: a long-term study in humans

BACKGROUND

Evidence suggests that an increased incidence of atrial fibrillation occurs in patients undergoing single-chamber ventricular pacing (VVI) when compared with those undergoing single-chamber atrial pacing (AAI) or those having dual-chamber atrioventricular pacing (DDD). The mechanism for this is unknown. We hypothesized that long-term loss of atrioventricular (AV) synchrony leads to atrial electrical remodeling: a potential explanation for this difference.

METHODS AND RESULTS

The study was a prospective, randomized comparison between 18 patients paced in VVI mode and 12 patients paced in DDD mode for 3 months. Under autonomic blockade, effective refractory periods (ERPs) from the lateral right atrium (RA), RA appendage, RA septum, and coronary sinus-corrected sinus node recovery times (cSNRTs), as well as P-wave duration (PWD), and biatrial diameters were measured at baseline and 3 months. The VVI group was then programmed to DDD pacing and reevaluated after a further 3 months. After long-term VVI pacing, ERPs at all 4 atrial sites increased significantly in a nonuniform fashion in association with biatrial dilatation. PWD and cSNRTs also prolonged significantly. With the reestablishment of AV synchrony, ERPs, PWD, cSNRTs, and biatrial dimensions returned to baseline levels. In the 12 patients who underwent long-term DDD pacing from baseline, no significant changes in atrial electrophysiology or biatrial dimensions were demonstrated.

CONCLUSIONS

Long-term loss of AV synchrony induced by VVI pacing is associated with atrial electrical remodeling, which is reversible after the reestablishment of AV synchrony with DDD pacing. This process may be partly responsible for the higher incidence of atrial fibrillation in patients undergoing VVI pacing compared with AV sequential pacing.

Left atrial "stunning" following radiofrequency catheter ablation of chronic atrial flutter

OBJECTIVES

This study examined the effect of radiofrequency ablation (RFA) on left atrial (LA) and left atrial appendage (LAA) function in humans with chronic atrial flutter (AFL).

BACKGROUND

Atrial stunning and the development of spontaneous echocardiographic contrast (SEC) is a consequence of electrical cardioversion of AFL to sinus rhythm. This phenomenon has been termed "stunning" and is associated with thrombus formation and embolic stroke. Radiofrequency ablation is now considered to be definitive treatment for chronic AFL, but whether this procedure is complicated by LA stunning is unknown.

METHODS

Fifteen patients with chronic AFL undergoing curative RFA underwent transesophageal echocardiography to evaluate LA and LAA function and SEC before and immediately, 30 minutes and 3 weeks after RFA. To control for possible direct effects of RFA on atrial function, seven patients undergoing RFA for paroxysmal AFL were also studied. In this group, RF energy was delivered in sinus rhythm and echocardiographic parameters were assessed before and immediately and 30 minutes following RFA.

RESULTS

Chronic AFL: Mean arrhythmia duration was 17.2 +/- 13.3 months. Twelve patients (80%) developed SEC following RF energy application and reversion to sinus rhythm. LAA velocities decreased significantly from 54.0 +/- 14.2 cm/s in AFL to 18.0 +/- 7.1 cm/s in sinus rhythm after arrhythmia termination (p < 0.01). These changes persisted for 30 minutes. Following 3 weeks of sustained sinus rhythm, significant improvements in LAA velocities (68.9 +/- 23.6 vs. 18.0 +/- 7.1 cm/s, p < 0.01) and mitral A-wave velocities (49.8 +/- 10.3 vs. 13.4 +/- 11.2 cm/s, p < 0.01) were evident and SEC had resolved in all patients. Paroxysmal AFL: Radiofrequency energy delivered in sinus rhythm had no significant effect on any of the above indexes of LA or LAA function and no patient developed SEC following RFA.

CONCLUSIONS

Radiofrequency ablation of chronic AFL is associated with significant LA stunning and the development of SEC. Left atrial stunning is not secondary to the RF energy application itself. Sustained sinus rhythm for 3 weeks leads to resolution of these acute phenomena. Left atrial stunning occurs in the absence of direct current shock or antiarrhythmic drugs, suggesting that its mechanism may be a function of the preceding arrhythmia rather than the mode of reversion.

Risk of thromboembolism in chronic atrial flutter

Anticoagulant therapy is not conventionally used in the treatment of patients with atrial flutter. This recommendation has been based on sparse clinical experience, and recent preliminary reports suggest a significant risk of thromboembolism for these patients. A retrospective study was undertaken to assess the frequency of thromboembolic events as well as potential risk factors for these events in a cohort of patients with atrial flutter referred for radiofrequency ablation treatment. Eighty-six consecutive patients with a primary diagnosis of atrial flutter were evaluated. A history of embolic events was noted in 12 of 86 patients (14%) with atrial flutter, with an annual risk of approximately 3%. There were no differences in the prevalence of coronary artery disease, cardiomyopathy, valvular disease, or atrial fibrillation between the 2 groups of patients having an embolic event and those of patients without embolic events. Left ventricular function and left atrial size were also similar between the 2 groups. The only significant risk factor was hypertension (p < 0.05). However, in a regression model with other clinical variables (i.e., age, gender, left atrial size, presence or absence of any cardiac disease, length of time in flutter, left ventricular function, type of flutter, flutter cycle length, type of secondary arrhythmias) no significant predictors were found. Patients with transient ischemic attacks or pulmonary emboli were then excluded from the analysis in order to compare the thromboembolic risk in the present study to that reported in major atrial fibrillation trials. The overall risk becomes 7% (6 of 86), which over a mean follow-up period of 4.5 years yields an annual risk of approximately 1.6%. Although this risk is only 1/3 of that for patients with atrial fibrillation, this risk is higher than previously recognized for patients with chronic atrial flutter. Anticoagulant therapy should be seriously considered for these patients.

Apolipoprotein D in the aging brain and in Alzheimer's dementia

Apolipoprotein D (apoD) levels were examined in the temporal cortex as well as an assessment of the location of apoD positive cells within the brain by immunohistochemical and biochemical methods in young control (YC), aged control (AC), and Alzheimer's demented (AD) probands. Scattered apoD positive astrocytes and oligodendrocytes were found throughout the white matter by immunohistochemistry. ApoD immunoreactivity was also observed in the cerebellar oligodendrocytes of the YC group. There was faint positive apoD staining in scattered cortical astrocytes and a few neurons in the same group. In contrast, some of the AC and all of the AD probands had intense and frequent apoD immunostained cortical astrocytes and pyramidal neurons. The cortical senile plaques and neurofibrillary tangles were apoD immunonegative. No quantitative differences were found between the cortical apoD levels in the AC and AD groups, determined by immunoblotting. ApoD detected in the brain tissue was different in molecular weight (29 kDal) from that seen in CSF or in the serum (32 kDal). Our results indicate apoD is present in the human brain, especially in glial cells, and has increased abundance in the elderly and AD subjects.

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.

Mechanism of initiation of atrial flutter in humans: site of unidirectional block and direction of rotation

OBJECTIVES

Using a standardized induction protocol, we investigated the mechanism of initiation of atrial flutter, before ablation, to determine the site of initiating unidirectional block and to test the hypothesis that the direction of rotation of atrial flutter depends on the pacing site from which it initiates.

BACKGROUND

The high recurrence rate of atrial flutter after presumed successful ablation may be due to difficulty in reinduction after termination. In addition, induction of clockwise flutter is currently of unknown clinical importance.

METHODS

Ten patients with documented typical flutter were studied before ablation. A standard protocol consisting of single and double extrastimuli followed by burst pacing was performed from four sites in the right atrium (high and low trabeculated and smooth right atrium) to assess efficacy at inducing atrial flutter. A 20-pole halo catheter placed around the tricuspid annulus and a decapole catheter placed in the coronary sinus were used for mapping during initiation to determine type of flutter induced and the site of unidirectional block during initiation.

RESULTS

Atrial flutter was induced in 52 (6.2%) of 838 attempted inductions. Of these, 33 were counterclockwise and 20 were clockwise. Of the 20 inductions resulting in clockwise flutter, 18 were from the trabeculated right atrium, whereas all the counterclockwise inductions were from the smooth right atrium. In all but the two inductions, the site of unidirectional block was identified between the os of the coronary sinus and the low lateral right atrium for both counterclockwise and clockwise flutter, in the same isthmus at which ablation is targeted.

CONCLUSIONS

Even in patients with clinical counterclockwise flutter, clockwise flutter is frequently induced before ablation and is dependent on the site of induction: Pacing from the smooth right atrium induces counterclockwise flutter, whereas pacing from the trabeculated right atrium induces clockwise flutter. The site of the unidirectional block during the initiation of either form of flutter is in the low right atrium isthmus.

Use of intracardiac echocardiography in interventional electrophysiology

Intracardiac echocardiography is emerging as a potentially useful tool during RF ablation procedures. There are a number of potential benefits of direct endocardial visualization during RF ablation including: (1) precise anatomical localization of the ablation catheter tip in relation to important endocardial structures, which cannot be visualized with fluoroscopy; (2) reduction in fluoroscopy time; (3) evaluation of catheter tip tissue contact; (4) confirmation of lesion formation and identification of lesion size and continuity; (5) immediate identification of complications; and (6) as a research tool to help in understanding the critical role played by specific endocardial structures in arrhythmogenesis. This article will review existing data and speculate as to possible future roles for intracardiac echocardiography in interventional electrophysiology.