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Radiofrequency catheter ablation and nerve growth factor concentration in humans
Radiofrequency catheter ablation and nerve growth factor concentration in humans Simon Kangavari, MD,** Yong-Seog Oh, MD, PhD,†* Shengmei Zhou, MD,* Ho-Joong Youn, MD,† Man-Young Lee, MD,† Wook-Sung Jung, MD,† Tae-ho Rho, MD,† Soon-Jo Hong, MD,† Saibal Kar, MD,* Walter F. Kerwin, MD,* Charles D. Swerdlow, MD,* Eli S. Gang, MD,* Donna M. Gallik, MD,* Jeffrey S. Goodman, MD,* Yii-Der Ida Chen, MD,*‡ Peng-Sheng Chen, MD** From the *Division of Cardiology, Department of Medicine and ‡Department of Obstetrics and Gynecology, Cedars-Sinai Medical Center and the David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, † Division of Cardiology, Department of Medicine, St. Mary Hospital and Catholic University, Seoul, Korea. BACKGROUND In animal models, expression of nerve growth factor (NGF) is increased after necrotic myocardial injury. Whether radiofrequency (RF) catheter ablation increases NGF expression in humans is unclear. OBJECTIVES The purpose of this study was to determine NGF concentrations in the aorta, coronary sinus, and peripheral veins before and after RF ablation in patients. METHODS We sampled blood from aorta and either great cardiac vein (group 1, N ⫽ 18) or proximal (group 2, N ⫽ 20) coronary sinus before and after RF ablation. In group 3 (N ⫽ 21), peripheral venous blood was sampled before and after RF ablation and then up to postoperative day 7. In group 4 (N ⫽ 10), we sampled peripheral venous blood during diagnostic electrophysiologic study. The NGF concentration was determined by enzyme-linked immunosorbent assay. Transcardiac NGF concentration was the difference in NGF concentrations between coronary sinus and aorta.
Radiofrequency (RF) catheter ablation is commonly used in the treatment of patients with supraventricular and ventricular arrhythmias. Although the procedure is associated with low morbidity and mortality, many investigators have reported a transient increase in atrial arrhythmias after RF ablation.1– 8 Previous studies demonstrated that necrotic cardiac injury, including RF ablation, is followed by cardiac nerve sprouting and sympathetic hyperinnervation.9 –12 The increased sympathetic innervation may be important in cardiac arrhythmogenesis.13 Zhou et al14 reported that myocardial infarction causes immediate elevation of transcardiac NGF concentrations (defined by the concentration differences between coronary sinus and aorta) in dogs, suggesting NGF release from damaged myocardium. This was folThis study was supported by National Institutes of Health Grants HL66389, HL78932, P50-HL52319, and HL71140; a Wasserman Foundation Endowment; and a Pauline and Harold Price Endowment. * The first two authors contributed equally to this work. Address reprint requests and correspondence: Dr. Peng-Sheng Chen, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Room 5537, Los Angeles, California 90048. E-mail address: [email protected]. (Received April 9, 2006; accepted June 27, 2006.)
RESULTS There was no change in transcardiac NGF concentrations in groups 1 and 2. In group 3, the NGF level did not change significantly from before the procedure (17.10 ⫾ 15.80 ng/mL) to immediately after the procedure (14.46 ⫾ 10.36 ng/mL). However, NGF levels increased significantly to 31.24 ⫾ 19.82 ng/mL (N ⫽ 21, P ⬍.0001) on postoperative day 1, 26.23 ⫾ 16.89 ng/mL (N ⫽ 20, P ⬍.001) on postoperative day 2, and 22.01 ⫾ 11.35 ng/mL (N ⫽ 16, P ⫽ .003) on postoperative day 3. NGF concentrations did not change significantly in group 4. CONCLUSION RF ablation did not result in a detectable increase of transcardiac NGF concentration immediately after the procedure. However, the systemic NGF concentration increased significantly on postoperative days 1 to 3, suggesting that RF ablation resulted in increased NGF expression. KEYWORDS Atrial fibrillation; Enzyme-linked immunosorbent assay; Nerve growth factor; Neurotrophic factor (Heart Rhythm 2006;3:1150 –1155) © 2006 Heart Rhythm Society. All rights reserved.
lowed by increased mRNA NGF in the myocardium 3 days later. Based on these animal studies, we hypothesized that RF ablation in humans may result in acute myocardial NGF release, which increases transcardiac NGF concentration by the end of the procedure. This is followed by chronic elevation of systemic NGF concentration through increased NGF production. The purpose of the present study was to test these hypotheses by determining NGF concentrations in the aorta, coronary sinus, and peripheral veins before and after RF ablation in patients.
Methods The study protocol was approved by the Institutional Review Board of Cedars-Sinai Medical Center and St. Mary Hospital. Prior to the procedure, patients undergoing RF catheter ablation of cardiac arrhythmias consented to have blood sampled from the aorta, coronary sinus, and/or peripheral veins during and after the procedure. The blood samples were coded for confidentiality before delivery to the laboratory. The technician who performed the enzymelinked immunosorbent assay of NGF was blinded to patient information. Electrophysiologic study and RF ablation pro-
1547-5271/$ -see front matter © 2006 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2006.06.033
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cedures were performed according to the clinical needs of the patients and were not altered by the study protocol. The procedures in groups 1 through 3 included insertion of an open-lumen coronary sinus catheter and access to the aorta through the femoral artery for blood pressure monitoring. A coronary sinus venogram was routinely performed to document proper coronary sinus cannulation. We used the blood sampled from the femoral artery catheter as a surrogate for aortic blood, as not all patients have catheters placed in the aorta. In group 4, only venous blood was sampled. Group 1 and some of the group 2 patients were recruited from the Cedars-Sinai Medical Center. The remaining patients were recruited from St. Mary Hospital. The blood samples were stored at ⫺80°C. At the completion of the blood collection for each protocol, the blood samples for that protocol were assayed together.
Group 1: Blood sampled from the great cardiac vein and femoral artery Group 1 consisted of 18 patients in whom blood was sampled from the greater cardiac vein by advancing the distal pole of the coronary sinus catheter beyond the valve of Vieussens or the opening of the vein of Marshall.15,16 The blood sampling was performed prior to any ablation. A simultaneous blood sample was obtained from the femoral artery. Blood also was collected from the same two sites at the end of the study prior to catheter removal.
Group 2: Blood sampled from the proximal coronary sinus and femoral artery As discussed in the Results, group 1 patients did not show a significant increase of transcardiac NGF concentrations immediately after the procedure compared with before the procedure. One potential technical problem is that the distal opening of the coronary sinus catheter is located upstream from the ablation site. It is possible that, if the sampling site is downstream from the ablation site, then an increased transcardiac NGF concentration could be demonstrated. Therefore, we studied an additional 20 patients (group 2) in whom blood was sampled from the coronary sinus when the catheter was positioned at the orifice and before any ablation was performed. A simultaneous sample was obtained from the femoral artery. Blood also was collected from the same two sites at the end of the study prior to catheter removal.
Group 3: Blood sampled from the peripheral veins in patients with RF ablation Group 3 consisted of 21 patients who underwent RF ablation. Venous blood was sampled from a peripheral vein before and after RF ablation and again on postoperative days 1 to 7 after ablation if the patient was still in the hospital. Atrial fibrillation (AF) ablations were performed with circular mapping catheter-guided pulmonary vein ostial isolation. All patients also underwent cavotricuspid isthmus ablation in the right atrium to create bidirectional conduction block. For patients who underwent RF ablation
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for atrial flutter, only the cavotricuspid isthmus in the right atrium was ablated.
Group 4: Blood sampled from the peripheral veins in patients without ablation Group 4 consisted of 10 patients who underwent routine diagnostic electrophysiologic study without ablation. Venous blood was sampled from a peripheral vein before and after ablation and again on postoperative days 1 to 6.
Enzyme-linked immunosorbent assay Serum (group 1) and plasma (groups 2– 4) NGF concentrations were assayed by sandwich enzyme-linked immunosorbent assay using the NGF Emax ImmunoAssay System (Promega, Madison, WI) according to the manufacturer’s instructions. All assays were performed on F-bottom 96well plates (Nunc, Wiesbaden, Germany). Tertiary antibodies were conjugated to horseradish peroxidase. Each test sample was diluted to 1:300 or 1:400. Samples were incubated for 6 to 8 hours with a shaker at room temperature. Wells were developed with tetramethylbenzidine and measured at 450 nm within 30 minutes. NGF content was quantified against a standard curve calibrated with known amounts of protein. The plasma levels of cardiac troponin-I was determined using an enzyme-linked immunosorbent assay kit supplied by Life Diagnostics, Inc, West Chester, PA. Each test sample was diluted to 1:1 and measured at 450 nm within 15 minutes. All samples were assayed in triplicate and expressed as the mean.
Statistical analysis Data are presented as mean ⫾ SD. Paired t-tests were used to compare the means and the sign test to determine whether the NGF concentration increased or decreased on different days. Because of the large variations in NGF concentration, the data were converted to log scale before performing the t-tests. When a single comparison was used, P ⱕ.05 was considered significant. In groups 3 and 4, NGF concentrations between postoperative days 1 to 3 were compared with NGF concentration immediately after RF ablation. Because three comparisons were made, P ⬍.0167 was considered significant (Bonferroni correction).
Results Baseline demographics of the patient groups are given in Table 1. The specific ablation procedures performed are summarized in Table 2.
Group 1 In Group 1, the concentration of NGF in the artery increased from before the procedure to immediately after the procedure (20.69 ⫾ 21.70 ng/mL to 25.75 ⫾ 24.52 ng/mL, P ⫽ .018). The concentration of NGF in the great cardiac vein also increased, from 20.75 ⫾ 25.02 ng/mL to 25.22 ⫾ 28.18 ng/mL (P ⬍.001). However, there was no significant change in transcardiac NGF concentrations from before the procedure to after the procedure (0.06 ⫾ 5.58 ng/mL vs ⫺0.52 ⫾ 13.31 ng/mL, P ⫽ NS).
1152 Table 1
Heart Rhythm, Vol 3, No 10, October 2006 Patient characteristics
Median age (yr) Male gender Diabetes Hypertension Hypercholesterolemia Coronary artery disease Medication use Antiarrhythmic Beta-blocker Calcium channel blocker Digoxin Angiotensin-converting enzyme inhibitor Angiotensin receptor blocker Aspirin Warfarin Diuretic Statin
Group 1 (N ⫽ 18)
Group 2 (N ⫽ 20)
Group 3 (N ⫽ 21)
Group 4 (N ⫽ 10)
53 ⫾ 15.3 15 (83) 1 (5) 7 (38) 4 (22) 3 (17)
51 ⫾ 12.6 12 (60) 2 (10) 7 (35) 2 (10) 2 (10)
51 ⫾ 9.6 16 (76) 2 (10) 6 (29) 0 (0) 0 (0)
57.8 ⫾ 14.6 3 (30) 1 (10) 5 (50) 3 (30) 0 (0)
7 5 6 4 0 6 6 12 4 3
12 3 3 4 1 1 1 8 4 1
0 2 1 0 0 2 0 0 1 3
3 7 1 4 3 1 2 3 2 2
(17) (39) (5) (22) (17) (5) (11) (17) (11) (11)
(35) (25) (30) (20) (0) (30) (30) (60) (20) (15)
(57) (14) (14) (19) (5) (5) (4) (38) (19) (5)
(0) (20) (10) (0) (0) (2) (0) (0) (10) (30)
Values are given as mean ⫾ SD or number (percent).
Group 2 In Group 2, the concentration of NGF in arterial blood did not change significantly from before ablation to immediately after ablation (20.45 ⫾ 10.54 ng/mL to 19.82 ⫾ 10.64 ng/mL, P ⫽ NS). The NGF concentration from the proximal portion of the coronary sinus vein did not change significantly from before ablation to after ablation (20.14 ⫾ 9.94 ng/mL to 18.94 ⫾ 8.69 ng/mL, P ⫽ NS). There was no Table 2
significant change in transcardiac NGF concentrations from before the procedure to after the procedure (⫺0.31 ⫾ 4.10 ng/mL vs ⫺0.88 ⫾ 6.61 ng/mL, P ⫽ NS).
Group 3 The NGF concentrations in group 3 patients are shown in Figure 1 (filled columns). There were no significant changes
Procedures performed
Procedures
Group 1
Group 2
Group 3
AVNRT Atrial flutter Atrial fibrillation Wolff-Parkinson-White syndrome Inappropriate sinus tachycardia AVRT VT Diagnostic electrophysiologic study Average procedure time (min) AVNRT Atrial flutter Atrial fibrillation Wolff-Parkinson-White syndrome Inappropriate sinus tachycardia AVRT VT Diagnostic electrophysiologic study Average ablation time (min) AVNRT Atrial flutter Atrial fibrillation Wolff-Parkinson-White syndrome Inappropriate sinus tachycardia AVRT VT Diagnostic electrophysiologic study
6 7 1 3 1
3 1 12 2 0 1 1
3 2 15 0 0 0 1
(33) (39) (5) (18) (5)
(15) (5) (60) (10) (0) (5) (5)
Group 4
(14) (10) (71) (0) (0) (0) (5) 10 (100)
135 ⫾ 35 227 ⫾ 91 300 100 ⫾ 21 200 0 0
130 ⫾ 48 120 330 ⫾ 169 175 ⫾ 45 — 150 130
143 ⫾ 37 165 ⫾ 63 308 ⫾ 58 — — — 240
7⫾4 25 ⫾ 11 45 3⫾3 8
7.2 ⫾ 6.3 23 54.6 ⫾ 35.6 9.7 ⫾ 3.7 — 5.31 5.0
6.1 ⫾ 1.0 52.9 ⫾ 47 73.5 ⫾ 15.2 — — — 13.6
Values are given as mean ⫾ SD or number (percent). AVNRT ⫽ atrioventricular nodal reentrant tachycardia; AVRT ⫽ atrioventricular reentrant tachycardia; VT ⫽ ventricular tachycardia.
93 ⫾ 35
0
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Nerve Growth Factor and Radiofrequency Ablation
NGF Concentration (ng/ml)
70 60 50 40
*
30 20
*
*
10 0 N= 21,10 Pre
21,10 Post
21,10 POD1
20,10 POD2
16,11
11,9
POD3
POD4
3, 4 POD5
2, 1 POD6
1 POD7
Figure 1 Changes of nerve growth factor (NGF) concentration in group 3 (filled columns) and group 4 (unfilled columns) patients. In group 3, there was no change in NGF concentration from preablation (Pre) to postablation (Post). However, there was an increase in NGF concentrations on postoperative day 1 (POD1) followed by slight reduction on postoperative days 2 and 3. Asterisks indicate that the NGF concentration on postoperative days 1 to 3 were significantly higher than the immediate postablation values.
in venous NGF concentration from before the procedure to immediately after the procedure (17.10 ⫾ 15.80 ng/mL vs 14.46 ⫾ 10.36 ng/mL, P ⫽ NS, N ⫽ 21). However, NGF levels increased significantly (from the immediate postablation values) to 31.24 ⫾ 19.82 ng/mL (N ⫽ 21, P ⬍.0001) on postoperative day 1, 26.23 ⫾ 16.89 ng/mL (N ⫽ 20, P ⬍.001) on postoperative day 2, and 22.01 ⫾ 11.35 ng/mL (N ⫽ 16, P ⫽ .003) on postoperative day 3. NGF concentrations were 29.14 ⫾ 17.76 ng/mL (N ⫽ 11) on postoperative day 4, 39.02 ⫾ 21.53 ng/mL (N ⫽ 3) on postoperative day 5, 29.95 ⫾ 4.57 ng/mL (N ⫽ 2) on postoperative day 6, and 33.51 ng/mL (N ⫽ 1) on postoperative day 7. Of the 21 patients studied, 20 showed an increase from immediate postablation to postoperative day 1; the one patient who had a decreased reading changed only from 22.87 to 19.14 ng/mL. Of the 20 patients with two postoperative readings, 16 showed a decrease from postoperative day 1 to postoperative day 2 (P ⬍.05 by sign test). Of the 16 patients with at least three postoperative readings, seven decreased from day 2 to day 3, six increased, and three did not change. These findings suggest an immediate increase, followed by a decrease and then stabilization of NGF concentrations. There was no correlation between the magnitude of NGF increase and the duration of ablation or the total duration of the procedure. Table 2 shows that group 3 included three patients with AV nodal reentrant tachycardia (AVNRT) and 15 patients with AF. The 15 patients with AF had an average ablation time more than 10-fold longer than the average ablation time of the three patients with AVNRT. NGF levels for AVNRT and AF patients were, respectively, 17.26 ⫾ 1.39 ng/mL and 14.38 ⫾ 11.98 ng/mL immediately after ablation (P ⫽ NS) and 39.95 ⫾ 9.27 ng/mL and 27.66 ⫾ 20.98 ng/mL on postoperative day 1 (P ⫽ NS). The magnitude of NGF increase (delta) between postoperative day 1 and immediately after ablation was 22.69 ⫾ 9.87 ng/mL for patients with AVNRT and 13.28 ⫾ 16.74 ng/mL for patients with AF (P ⫽ NS). These data further demonstrate a lack of
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correlation between the magnitude of NGF increase and the duration of ablation. The cardiac troponin-I levels for group 3 patients were 0.075 ⫾ 0.074 (range 0.005– 0.341) ng/mL before ablation and 1.361 ⫾ 0.885 ng/mL (range 0.029 –3.755 ng/mL) on postoperative day 1 (P ⬍.001). The average increase (delta) per patient was 1.29 ⫾ 0.888 ng/mL. There was no correlation between postoperative day 1 NGF and cardiac troponin-I level, between delta NGF and delta cardiac troponin-I level from immediate postablation to postoperative day 1, between ablation time and postoperative day 1 cardiac troponin-I level, or between ablation time and delta cardiac troponin-I level. All except for three patients in group 3 underwent cardioversion during the procedure. No patients showed signs of heart failure. No significant groin hematoma or pericardial effusion occurred after the procedure.
Group 4 None of the group 4 patients had inducible arrhythmia. NGF concentrations of Group 4 patients are shown in Figure 1 (unfilled columns). NGF levels immediately before, immediate after, and on postoperative days 1 to 6 were 11.28 ⫾ 8.25 ng/mL (N ⫽ 10), 9.56 ⫾ 6.78 ng/mL (N ⫽ 10), 11.63 ⫾ 6.94 ng/mL (N ⫽ 10), 11.21 ⫾ 7.36 ng/mL (N ⫽ 10), 12.37 ⫾ 9.78 ng/mL (N ⫽ 10), 9.95 ⫾ 9.01 ng/mL (N ⫽ 9), 10.73 ⫾ 4.94 ng/mL (N ⫽ 4), and 8.09 ng/mL (N ⫽ 1), respectively. There was no significant difference of NGF concentration between immediately postablation and any of the other time points. The ratio between postoperative day 1 and immediately postablation averaged 1.34 ⫾ 0.52 (range 0.86 –2.59, P ⫽ NS).
NGF concentration and atrial arrhythmia recurrence in group 3 patients Group 3 included 17 patients who underwent ablation for either AF (n ⫽ 15) or atrial flutter (n ⫽ 2). The latter two patients both had a history of AF. After 11 ⫾ 1 months of follow-up, 6 of these 17 patients in group 3 had recurrences of AF or atrial flutter. In the six patients with AF recurrence, NGF level increased from 7.36 ⫾ 3.01 ng/mL immediately after ablation to 36.60 ⫾ 26.63 ng/mL on postoperative day 1 (P ⬍.001), with an average increase of 5.05 ⫾ 3.75 fold (range 1.77–11.83, Figure 2, unfilled columns). In contrast, the 11 patients without AF recurrence had an increase in NGF level from 17.21 ⫾ 12.93 ng/mL immediately postablation to 26.43 ⫾ 18.59 ng/mL on postoperative day 1 (P ⬍.01), with an average increase of 1.77 ⫾ 0.64 fold (range 0.88 –3.17, Figure 2, filled columns). In patients with recurrence, the total duration of RF application was 3,042 ⫾ 1,913 seconds and the total duration of the procedure was 280 ⫾ 139 minutes. These durations were not different from those in patients without recurrence: total duration of RF application 4,051 ⫾ 790 seconds (P ⫽ .14) and total duration of the procedure 289 ⫾ 57 minutes (P ⫽ .85). These findings suggest an association between the magnitude of NGF increase and the recurrence of AF after procedure.
Relative NGF Concentrations
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Heart Rhythm, Vol 3, No 10, October 2006
9
NGF concentration in humans
8
Human plasma and serum NGF concentrations have been measured by many different laboratories. The absolute NGF levels in humans vary significantly, depending on the methods used for analyses.21–26 However, repeated measures of NGF in the same patients showed stability over time. For example, Lang et al25 measured human NGF serum concentrations repeatedly and showed no significant changes of NGF concentrations over 4 weeks. The authors concluded that the stability of repetitive measurements over 4 weeks suggests that NGF is a reproducible and stable marker in human serum within an individual. An implication is that the abrupt threefold increase on postoperative day 1 of the present study likely was not due to spontaneous variations of NGF concentrations.
7 6
*
5 4 3 2
*
1 0
N= 11,6 Pre
11,6 Post
11,6 POD1
11,6 POD2
8, 5 POD3
6, 4 POD4
2 POD5
1 POD6
Figure 2 Relative nerve growth factor (NGF) concentrations in group 3 patients with (unfilled columns) and without (filled columns) recurrences of atrial fibrillation or atrial flutter after ablation. The changes on postoperative day 1 (POD1) were significant (asterisks) compared with immediate postablation values.
However, the case number is too small to draw a definite conclusion.
Discussion RF ablation did not result in a detectable increase of transcardiac NGF concentration immediately after the procedure. However, the systemic NGF concentration increased significantly on postoperative days 1 to 3, suggesting that RF ablation resulted in increased NGF expression.
Nerve sprouting after myocardial injury Following division, crushing, interference of blood supply, or other means of injury to a nerve, peripheral nerves undergo wallerian degeneration,17 which may be followed by neurilemma cell proliferation and axonal regeneration. The regeneration effort is triggered by re-expression of NGF or other neurotrophic factor genes in the non-neuronal cells around the site of injury.18 For example, NGF activity in the Schwann cells of sympathetically denervated rat iris is increased significantly.19 Because nerves in the heart may be injured during myocardial ischemia,20 it is reasonable to expect that nerve sprouting and NGF overexpression also occur after myocardial injury. Compatible with this expectation, Zhou et al14 found that acute myocardial ischemia in dogs causes an immediate (within 30 minutes) increase of transcardiac NGF concentration. In comparison, mRNA NGF and mRNA of growth-associated protein-43 (GAP43) began to increase 3 days after myocardial infarction and peaked 1 week later. We do not have data on postoperative day 1 or postoperative day 2 in that study. Because the increase of transcardiac NGF preceded the increase of mRNA NGF, the initial rise of transcardiac NGF most likely is due to the release of preformed NGF from the myocardium in response to massive myocardial injury. The subsequent elevation of NGF is due to overexpression of mRNA NGF. Unlike myocardial infarction, RF ablation does not damage a large amount of myocardium. Therefore, the initial release of NGF may be either small or undetectable. However, because of subsequent overexpression of mRNA NGF, the NGF concentration began to increase on postoperative day 1 and persisted for many days afterward.
Study limitations The number of patients is small. Therefore, whether or not NGF elevation is a reliable predictor of AF recurrence cannot be proven definitively by the data available in this study.
Conclusion RF catheter ablation does not increase transcardiac NGF concentrations immediately after the procedure. However, significant increases of venous NGF concentrations occur on postoperative day 1 and persist for at least 2 days afterward. The results support the hypothesis that RF ablation results in up-regulation of NGF expression in humans.
Acknowledgments We thank Ji-Hoon Kim, Hongmei Li, Su-Chao Ding, Lan S. Chen, Lei Lin, and Elaine Lebowitz for assistance and C. Thomas Peter for support.
References 1. Ehlert FA, Goldberger JJ, Brooks R, Miller S, Kadish AH. Persistent inappropriate sinus tachycardia after radiofrequency current catheter modification of the atrioventricular node. Am J Cardiol 1992;69:1092–1095. 2. Skeberis V, Simonis F, Tsakonas K, Celiker A, Andries E, Brugada P. Inappropriate sinus tachycardia following radiofrequency ablation of AV nodal tachycardia: incidence and clinical significance. Pacing Clin Electrophysiol 1994;17:924 –927. 3. Dagres N, Clague JR, Lottkamp H, Hindricks G, Breithardt G, Borggrefe M. Impact of radiofrequency catheter ablation of accessory pathways on the frequency of atrial fibrillation during long-term follow-up; high recurrence rate of atrial fibrillation in patients older than 50 years of age. Eur Heart J 2001;22: 423– 427. 4. Chiang CE, Chen SA, Wang DC, Tsang WP, Hsia CP, Ting CT, Chiang CW, Wang SP, Chiang BN, Chang MS. Arrhythmogenicity of catheter ablation in supraventricular tachycardia. Am Heart J 1993;125:388 –395. 5. Frey B, Kreiner G, Binder T, Heinz G, Baumgartner H, Gossinger HD. Relation between left atrial size and secondary atrial arrhythmias after successful catheter ablation of common atrial flutter. Pacing Clin Electrophysiol 1997;20:2936 – 2942. 6. Cosío FG, Gil ML, Goicolea A, Arribas F, Barroso JL. Radiofrequency ablation of the inferior vena cava-tricuspid valve isthmus in common atrial flutter. Am J Cardiol 1993;71:705–709. 7. Steinberg JS, Prasher S, Zelenkofske S, Ehlert FA. Radiofrequency catheter ablation of atrial flutter: procedural success and long-term outcome. Am Heart J 1995;130:85–92. 8. Kocovic DZ, Harada T, Shea JB, Soroff D, Friedman PL. Alterations of heart rate and of heart rate variability after radiofrequency catheter ablation of supraventricular tachycardia. Delineation of parasympathetic pathways in the human heart. Circulation 1993;88:1671–1681.
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9. Vracko R, Thorning D, Frederickson RG. Fate of nerve fibers in necrotic, healing, and healed rat myocardium. Lab Invest 1990;63:490 –501. 10. Nori SL, Gaudino M, Alessandrini F, Bronzetti E, Santarelli P. Immunohistochemical evidence for sympathetic denervation and reinnervation after necrotic injury in rat myocardium. Cell Mol Biol 1995;41:799 – 807. 11. Cao J-M, Fishbein MC, Han JB, Lai WW, Lai AC, Wu T-J, Czer L, Wolf PL, Denton TA, Shintaku IP, Chen P-S, Chen LS. Relationship between regional cardiac hyperinnervation and ventricular arrhythmia. Circulation 2000;101: 1960 –1969. 12. Okuyama Y, Pak H-N, Miyauchi Y, Liu Y-B, Chou C-C, Hayashi H, Fu KJ, Kerwin WF, Kar S, Karagueuzian HS, Fishbein MC, Chen P-S, Lan LS. Sympathetic nerve sprouting induced by radiofrequency catheter ablation in dogs. Heart Rhythm 2005;1:712–717. 13. Rubart M, Zipes DP. Mechanisms of sudden cardiac death. J Clin Invest 2005;115:2305–2315. 14. Zhou S, Chen LS, Miyauchi Y, Miyauchi M, Kar S, Kangavari S, Fishbein MC, Sharifi B, Chen PS. Mechanisms of cardiac nerve sprouting after myocardial infarction in dogs. Circ Res 2004;95:76 – 83. 15. Chen P-S, Chou CC. Coronary sinus as an arrhythmogenic structure. J Cardiovasc Electrophysiol 2002;13:863– 864. 16. Ludinghausen MV, Ohmachi N, Boot C. Myocardial coverage of the coronary sinus and related veins. Clin Anat 1992;5:1–15. 17. Guth L. Regeneration in the mammalian peripheral nervous system. Physiol Rev 1956;36:441– 478. 18. Levi-Montalcini R. Growth control of nerve cells by a protein factor and its antiserum. Science 1964;143:105–110.
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19. Rush RA. Immunohistochemical localization of endogenous nerve growth factor. Nature 1984;312:364 –367. 20. Barber MJ, Mueller TM, Davies BG, Gill RM, Zipes DP. Interruption of sympathetic and vagal-mediated afferent responses by transmural myocardial infarction. Circulation 1985;72:623– 631. 21. Hadjiconstantinou M, McGuire L, Duchemin AM, Laskowski B, Kiecolt-Glaser J, Glaser R. Changes in plasma nerve growth factor levels in older adults associated with chronic stress. J Neuroimmunol 2001;116:102–106. 22. Parikh V, Evans DR, Khan MM, Mahadik SP. Nerve growth factor in nevermedicated first-episode psychotic and medicated chronic schizophrenic patients: possible implications for treatment outcome. Schizophr Res 2003;60:117–123. 23. Lambiase A, Bonini S, Bonini S, Micera A, Magrini L, Bracci-Laudiero L, Aloe L. Increased plasma levels of nerve growth factor in vernal keratoconjunctivitis and relationship to conjunctival mast cells. Invest Ophthalmol Vis Sci 1995;36: 2127–2132. 24. Matucci-Cerinic M, Giacomelli R, Pignone A, Cagnoni ML, Generini S, Casale R, Cipriani P, Del Rosso A, Tirassa P, Konttinen YT, Kahaleh BM, Fan PS, Paoletti M, Marchesi C, Cagnoni M, Aloe L. Nerve growth factor and neuropeptides circulating levels in systemic sclerosis (scleroderma). Ann Rheum Dis 2001;60:487– 494. 25. Lang UE, Gallinat J, Danker-Hopfe H, Bajbouj M, Hellweg R. Nerve growth factor serum concentrations in healthy human volunteers: physiological variance and stability. Neurosci Lett 2003;344:13–16. 26. Kaye DM, Vaddadi G, Gruskin SL, Du XJ, Esler MD. Reduced myocardial nerve growth factor expression in human and experimental heart failure. Circ Res 2000;86:E80 –E84.
Radiofrequency (RF) catheter ablation is commonly used in the treatment of patients with supraventricular and ventricular arrhythmias. Although the procedure is associated with low morbidity and mortality, many investigators have reported a transient increase in atrial arrhythmias after RF ablation.1– 8 Previous studies demonstrated that necrotic cardiac injury, including RF ablation, is followed by cardiac nerve sprouting and sympathetic hyperinnervation.9 –12 The increased sympathetic innervation may be important in cardiac arrhythmogenesis.13 Zhou et al14 reported that myocardial infarction causes immediate elevation of transcardiac NGF concentrations (defined by the concentration differences between coronary sinus and aorta) in dogs, suggesting NGF release from damaged myocardium. This was folThis study was supported by National Institutes of Health Grants HL66389, HL78932, P50-HL52319, and HL71140; a Wasserman Foundation Endowment; and a Pauline and Harold Price Endowment. * The first two authors contributed equally to this work. Address reprint requests and correspondence: Dr. Peng-Sheng Chen, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Room 5537, Los Angeles, California 90048. E-mail address: [email protected]. (Received April 9, 2006; accepted June 27, 2006.)
RESULTS There was no change in transcardiac NGF concentrations in groups 1 and 2. In group 3, the NGF level did not change significantly from before the procedure (17.10 ⫾ 15.80 ng/mL) to immediately after the procedure (14.46 ⫾ 10.36 ng/mL). However, NGF levels increased significantly to 31.24 ⫾ 19.82 ng/mL (N ⫽ 21, P ⬍.0001) on postoperative day 1, 26.23 ⫾ 16.89 ng/mL (N ⫽ 20, P ⬍.001) on postoperative day 2, and 22.01 ⫾ 11.35 ng/mL (N ⫽ 16, P ⫽ .003) on postoperative day 3. NGF concentrations did not change significantly in group 4. CONCLUSION RF ablation did not result in a detectable increase of transcardiac NGF concentration immediately after the procedure. However, the systemic NGF concentration increased significantly on postoperative days 1 to 3, suggesting that RF ablation resulted in increased NGF expression. KEYWORDS Atrial fibrillation; Enzyme-linked immunosorbent assay; Nerve growth factor; Neurotrophic factor (Heart Rhythm 2006;3:1150 –1155) © 2006 Heart Rhythm Society. All rights reserved.
lowed by increased mRNA NGF in the myocardium 3 days later. Based on these animal studies, we hypothesized that RF ablation in humans may result in acute myocardial NGF release, which increases transcardiac NGF concentration by the end of the procedure. This is followed by chronic elevation of systemic NGF concentration through increased NGF production. The purpose of the present study was to test these hypotheses by determining NGF concentrations in the aorta, coronary sinus, and peripheral veins before and after RF ablation in patients.
Methods The study protocol was approved by the Institutional Review Board of Cedars-Sinai Medical Center and St. Mary Hospital. Prior to the procedure, patients undergoing RF catheter ablation of cardiac arrhythmias consented to have blood sampled from the aorta, coronary sinus, and/or peripheral veins during and after the procedure. The blood samples were coded for confidentiality before delivery to the laboratory. The technician who performed the enzymelinked immunosorbent assay of NGF was blinded to patient information. Electrophysiologic study and RF ablation pro-
1547-5271/$ -see front matter © 2006 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2006.06.033
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cedures were performed according to the clinical needs of the patients and were not altered by the study protocol. The procedures in groups 1 through 3 included insertion of an open-lumen coronary sinus catheter and access to the aorta through the femoral artery for blood pressure monitoring. A coronary sinus venogram was routinely performed to document proper coronary sinus cannulation. We used the blood sampled from the femoral artery catheter as a surrogate for aortic blood, as not all patients have catheters placed in the aorta. In group 4, only venous blood was sampled. Group 1 and some of the group 2 patients were recruited from the Cedars-Sinai Medical Center. The remaining patients were recruited from St. Mary Hospital. The blood samples were stored at ⫺80°C. At the completion of the blood collection for each protocol, the blood samples for that protocol were assayed together.
Group 1: Blood sampled from the great cardiac vein and femoral artery Group 1 consisted of 18 patients in whom blood was sampled from the greater cardiac vein by advancing the distal pole of the coronary sinus catheter beyond the valve of Vieussens or the opening of the vein of Marshall.15,16 The blood sampling was performed prior to any ablation. A simultaneous blood sample was obtained from the femoral artery. Blood also was collected from the same two sites at the end of the study prior to catheter removal.
Group 2: Blood sampled from the proximal coronary sinus and femoral artery As discussed in the Results, group 1 patients did not show a significant increase of transcardiac NGF concentrations immediately after the procedure compared with before the procedure. One potential technical problem is that the distal opening of the coronary sinus catheter is located upstream from the ablation site. It is possible that, if the sampling site is downstream from the ablation site, then an increased transcardiac NGF concentration could be demonstrated. Therefore, we studied an additional 20 patients (group 2) in whom blood was sampled from the coronary sinus when the catheter was positioned at the orifice and before any ablation was performed. A simultaneous sample was obtained from the femoral artery. Blood also was collected from the same two sites at the end of the study prior to catheter removal.
Group 3: Blood sampled from the peripheral veins in patients with RF ablation Group 3 consisted of 21 patients who underwent RF ablation. Venous blood was sampled from a peripheral vein before and after RF ablation and again on postoperative days 1 to 7 after ablation if the patient was still in the hospital. Atrial fibrillation (AF) ablations were performed with circular mapping catheter-guided pulmonary vein ostial isolation. All patients also underwent cavotricuspid isthmus ablation in the right atrium to create bidirectional conduction block. For patients who underwent RF ablation
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for atrial flutter, only the cavotricuspid isthmus in the right atrium was ablated.
Group 4: Blood sampled from the peripheral veins in patients without ablation Group 4 consisted of 10 patients who underwent routine diagnostic electrophysiologic study without ablation. Venous blood was sampled from a peripheral vein before and after ablation and again on postoperative days 1 to 6.
Enzyme-linked immunosorbent assay Serum (group 1) and plasma (groups 2– 4) NGF concentrations were assayed by sandwich enzyme-linked immunosorbent assay using the NGF Emax ImmunoAssay System (Promega, Madison, WI) according to the manufacturer’s instructions. All assays were performed on F-bottom 96well plates (Nunc, Wiesbaden, Germany). Tertiary antibodies were conjugated to horseradish peroxidase. Each test sample was diluted to 1:300 or 1:400. Samples were incubated for 6 to 8 hours with a shaker at room temperature. Wells were developed with tetramethylbenzidine and measured at 450 nm within 30 minutes. NGF content was quantified against a standard curve calibrated with known amounts of protein. The plasma levels of cardiac troponin-I was determined using an enzyme-linked immunosorbent assay kit supplied by Life Diagnostics, Inc, West Chester, PA. Each test sample was diluted to 1:1 and measured at 450 nm within 15 minutes. All samples were assayed in triplicate and expressed as the mean.
Statistical analysis Data are presented as mean ⫾ SD. Paired t-tests were used to compare the means and the sign test to determine whether the NGF concentration increased or decreased on different days. Because of the large variations in NGF concentration, the data were converted to log scale before performing the t-tests. When a single comparison was used, P ⱕ.05 was considered significant. In groups 3 and 4, NGF concentrations between postoperative days 1 to 3 were compared with NGF concentration immediately after RF ablation. Because three comparisons were made, P ⬍.0167 was considered significant (Bonferroni correction).
Results Baseline demographics of the patient groups are given in Table 1. The specific ablation procedures performed are summarized in Table 2.
Group 1 In Group 1, the concentration of NGF in the artery increased from before the procedure to immediately after the procedure (20.69 ⫾ 21.70 ng/mL to 25.75 ⫾ 24.52 ng/mL, P ⫽ .018). The concentration of NGF in the great cardiac vein also increased, from 20.75 ⫾ 25.02 ng/mL to 25.22 ⫾ 28.18 ng/mL (P ⬍.001). However, there was no significant change in transcardiac NGF concentrations from before the procedure to after the procedure (0.06 ⫾ 5.58 ng/mL vs ⫺0.52 ⫾ 13.31 ng/mL, P ⫽ NS).
1152 Table 1
Heart Rhythm, Vol 3, No 10, October 2006 Patient characteristics
Median age (yr) Male gender Diabetes Hypertension Hypercholesterolemia Coronary artery disease Medication use Antiarrhythmic Beta-blocker Calcium channel blocker Digoxin Angiotensin-converting enzyme inhibitor Angiotensin receptor blocker Aspirin Warfarin Diuretic Statin
Group 1 (N ⫽ 18)
Group 2 (N ⫽ 20)
Group 3 (N ⫽ 21)
Group 4 (N ⫽ 10)
53 ⫾ 15.3 15 (83) 1 (5) 7 (38) 4 (22) 3 (17)
51 ⫾ 12.6 12 (60) 2 (10) 7 (35) 2 (10) 2 (10)
51 ⫾ 9.6 16 (76) 2 (10) 6 (29) 0 (0) 0 (0)
57.8 ⫾ 14.6 3 (30) 1 (10) 5 (50) 3 (30) 0 (0)
7 5 6 4 0 6 6 12 4 3
12 3 3 4 1 1 1 8 4 1
0 2 1 0 0 2 0 0 1 3
3 7 1 4 3 1 2 3 2 2
(17) (39) (5) (22) (17) (5) (11) (17) (11) (11)
(35) (25) (30) (20) (0) (30) (30) (60) (20) (15)
(57) (14) (14) (19) (5) (5) (4) (38) (19) (5)
(0) (20) (10) (0) (0) (2) (0) (0) (10) (30)
Values are given as mean ⫾ SD or number (percent).
Group 2 In Group 2, the concentration of NGF in arterial blood did not change significantly from before ablation to immediately after ablation (20.45 ⫾ 10.54 ng/mL to 19.82 ⫾ 10.64 ng/mL, P ⫽ NS). The NGF concentration from the proximal portion of the coronary sinus vein did not change significantly from before ablation to after ablation (20.14 ⫾ 9.94 ng/mL to 18.94 ⫾ 8.69 ng/mL, P ⫽ NS). There was no Table 2
significant change in transcardiac NGF concentrations from before the procedure to after the procedure (⫺0.31 ⫾ 4.10 ng/mL vs ⫺0.88 ⫾ 6.61 ng/mL, P ⫽ NS).
Group 3 The NGF concentrations in group 3 patients are shown in Figure 1 (filled columns). There were no significant changes
Procedures performed
Procedures
Group 1
Group 2
Group 3
AVNRT Atrial flutter Atrial fibrillation Wolff-Parkinson-White syndrome Inappropriate sinus tachycardia AVRT VT Diagnostic electrophysiologic study Average procedure time (min) AVNRT Atrial flutter Atrial fibrillation Wolff-Parkinson-White syndrome Inappropriate sinus tachycardia AVRT VT Diagnostic electrophysiologic study Average ablation time (min) AVNRT Atrial flutter Atrial fibrillation Wolff-Parkinson-White syndrome Inappropriate sinus tachycardia AVRT VT Diagnostic electrophysiologic study
6 7 1 3 1
3 1 12 2 0 1 1
3 2 15 0 0 0 1
(33) (39) (5) (18) (5)
(15) (5) (60) (10) (0) (5) (5)
Group 4
(14) (10) (71) (0) (0) (0) (5) 10 (100)
135 ⫾ 35 227 ⫾ 91 300 100 ⫾ 21 200 0 0
130 ⫾ 48 120 330 ⫾ 169 175 ⫾ 45 — 150 130
143 ⫾ 37 165 ⫾ 63 308 ⫾ 58 — — — 240
7⫾4 25 ⫾ 11 45 3⫾3 8
7.2 ⫾ 6.3 23 54.6 ⫾ 35.6 9.7 ⫾ 3.7 — 5.31 5.0
6.1 ⫾ 1.0 52.9 ⫾ 47 73.5 ⫾ 15.2 — — — 13.6
Values are given as mean ⫾ SD or number (percent). AVNRT ⫽ atrioventricular nodal reentrant tachycardia; AVRT ⫽ atrioventricular reentrant tachycardia; VT ⫽ ventricular tachycardia.
93 ⫾ 35
0
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Nerve Growth Factor and Radiofrequency Ablation
NGF Concentration (ng/ml)
70 60 50 40
*
30 20
*
*
10 0 N= 21,10 Pre
21,10 Post
21,10 POD1
20,10 POD2
16,11
11,9
POD3
POD4
3, 4 POD5
2, 1 POD6
1 POD7
Figure 1 Changes of nerve growth factor (NGF) concentration in group 3 (filled columns) and group 4 (unfilled columns) patients. In group 3, there was no change in NGF concentration from preablation (Pre) to postablation (Post). However, there was an increase in NGF concentrations on postoperative day 1 (POD1) followed by slight reduction on postoperative days 2 and 3. Asterisks indicate that the NGF concentration on postoperative days 1 to 3 were significantly higher than the immediate postablation values.
in venous NGF concentration from before the procedure to immediately after the procedure (17.10 ⫾ 15.80 ng/mL vs 14.46 ⫾ 10.36 ng/mL, P ⫽ NS, N ⫽ 21). However, NGF levels increased significantly (from the immediate postablation values) to 31.24 ⫾ 19.82 ng/mL (N ⫽ 21, P ⬍.0001) on postoperative day 1, 26.23 ⫾ 16.89 ng/mL (N ⫽ 20, P ⬍.001) on postoperative day 2, and 22.01 ⫾ 11.35 ng/mL (N ⫽ 16, P ⫽ .003) on postoperative day 3. NGF concentrations were 29.14 ⫾ 17.76 ng/mL (N ⫽ 11) on postoperative day 4, 39.02 ⫾ 21.53 ng/mL (N ⫽ 3) on postoperative day 5, 29.95 ⫾ 4.57 ng/mL (N ⫽ 2) on postoperative day 6, and 33.51 ng/mL (N ⫽ 1) on postoperative day 7. Of the 21 patients studied, 20 showed an increase from immediate postablation to postoperative day 1; the one patient who had a decreased reading changed only from 22.87 to 19.14 ng/mL. Of the 20 patients with two postoperative readings, 16 showed a decrease from postoperative day 1 to postoperative day 2 (P ⬍.05 by sign test). Of the 16 patients with at least three postoperative readings, seven decreased from day 2 to day 3, six increased, and three did not change. These findings suggest an immediate increase, followed by a decrease and then stabilization of NGF concentrations. There was no correlation between the magnitude of NGF increase and the duration of ablation or the total duration of the procedure. Table 2 shows that group 3 included three patients with AV nodal reentrant tachycardia (AVNRT) and 15 patients with AF. The 15 patients with AF had an average ablation time more than 10-fold longer than the average ablation time of the three patients with AVNRT. NGF levels for AVNRT and AF patients were, respectively, 17.26 ⫾ 1.39 ng/mL and 14.38 ⫾ 11.98 ng/mL immediately after ablation (P ⫽ NS) and 39.95 ⫾ 9.27 ng/mL and 27.66 ⫾ 20.98 ng/mL on postoperative day 1 (P ⫽ NS). The magnitude of NGF increase (delta) between postoperative day 1 and immediately after ablation was 22.69 ⫾ 9.87 ng/mL for patients with AVNRT and 13.28 ⫾ 16.74 ng/mL for patients with AF (P ⫽ NS). These data further demonstrate a lack of
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correlation between the magnitude of NGF increase and the duration of ablation. The cardiac troponin-I levels for group 3 patients were 0.075 ⫾ 0.074 (range 0.005– 0.341) ng/mL before ablation and 1.361 ⫾ 0.885 ng/mL (range 0.029 –3.755 ng/mL) on postoperative day 1 (P ⬍.001). The average increase (delta) per patient was 1.29 ⫾ 0.888 ng/mL. There was no correlation between postoperative day 1 NGF and cardiac troponin-I level, between delta NGF and delta cardiac troponin-I level from immediate postablation to postoperative day 1, between ablation time and postoperative day 1 cardiac troponin-I level, or between ablation time and delta cardiac troponin-I level. All except for three patients in group 3 underwent cardioversion during the procedure. No patients showed signs of heart failure. No significant groin hematoma or pericardial effusion occurred after the procedure.
Group 4 None of the group 4 patients had inducible arrhythmia. NGF concentrations of Group 4 patients are shown in Figure 1 (unfilled columns). NGF levels immediately before, immediate after, and on postoperative days 1 to 6 were 11.28 ⫾ 8.25 ng/mL (N ⫽ 10), 9.56 ⫾ 6.78 ng/mL (N ⫽ 10), 11.63 ⫾ 6.94 ng/mL (N ⫽ 10), 11.21 ⫾ 7.36 ng/mL (N ⫽ 10), 12.37 ⫾ 9.78 ng/mL (N ⫽ 10), 9.95 ⫾ 9.01 ng/mL (N ⫽ 9), 10.73 ⫾ 4.94 ng/mL (N ⫽ 4), and 8.09 ng/mL (N ⫽ 1), respectively. There was no significant difference of NGF concentration between immediately postablation and any of the other time points. The ratio between postoperative day 1 and immediately postablation averaged 1.34 ⫾ 0.52 (range 0.86 –2.59, P ⫽ NS).
NGF concentration and atrial arrhythmia recurrence in group 3 patients Group 3 included 17 patients who underwent ablation for either AF (n ⫽ 15) or atrial flutter (n ⫽ 2). The latter two patients both had a history of AF. After 11 ⫾ 1 months of follow-up, 6 of these 17 patients in group 3 had recurrences of AF or atrial flutter. In the six patients with AF recurrence, NGF level increased from 7.36 ⫾ 3.01 ng/mL immediately after ablation to 36.60 ⫾ 26.63 ng/mL on postoperative day 1 (P ⬍.001), with an average increase of 5.05 ⫾ 3.75 fold (range 1.77–11.83, Figure 2, unfilled columns). In contrast, the 11 patients without AF recurrence had an increase in NGF level from 17.21 ⫾ 12.93 ng/mL immediately postablation to 26.43 ⫾ 18.59 ng/mL on postoperative day 1 (P ⬍.01), with an average increase of 1.77 ⫾ 0.64 fold (range 0.88 –3.17, Figure 2, filled columns). In patients with recurrence, the total duration of RF application was 3,042 ⫾ 1,913 seconds and the total duration of the procedure was 280 ⫾ 139 minutes. These durations were not different from those in patients without recurrence: total duration of RF application 4,051 ⫾ 790 seconds (P ⫽ .14) and total duration of the procedure 289 ⫾ 57 minutes (P ⫽ .85). These findings suggest an association between the magnitude of NGF increase and the recurrence of AF after procedure.
Relative NGF Concentrations
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Heart Rhythm, Vol 3, No 10, October 2006
9
NGF concentration in humans
8
Human plasma and serum NGF concentrations have been measured by many different laboratories. The absolute NGF levels in humans vary significantly, depending on the methods used for analyses.21–26 However, repeated measures of NGF in the same patients showed stability over time. For example, Lang et al25 measured human NGF serum concentrations repeatedly and showed no significant changes of NGF concentrations over 4 weeks. The authors concluded that the stability of repetitive measurements over 4 weeks suggests that NGF is a reproducible and stable marker in human serum within an individual. An implication is that the abrupt threefold increase on postoperative day 1 of the present study likely was not due to spontaneous variations of NGF concentrations.
7 6
*
5 4 3 2
*
1 0
N= 11,6 Pre
11,6 Post
11,6 POD1
11,6 POD2
8, 5 POD3
6, 4 POD4
2 POD5
1 POD6
Figure 2 Relative nerve growth factor (NGF) concentrations in group 3 patients with (unfilled columns) and without (filled columns) recurrences of atrial fibrillation or atrial flutter after ablation. The changes on postoperative day 1 (POD1) were significant (asterisks) compared with immediate postablation values.
However, the case number is too small to draw a definite conclusion.
Discussion RF ablation did not result in a detectable increase of transcardiac NGF concentration immediately after the procedure. However, the systemic NGF concentration increased significantly on postoperative days 1 to 3, suggesting that RF ablation resulted in increased NGF expression.
Nerve sprouting after myocardial injury Following division, crushing, interference of blood supply, or other means of injury to a nerve, peripheral nerves undergo wallerian degeneration,17 which may be followed by neurilemma cell proliferation and axonal regeneration. The regeneration effort is triggered by re-expression of NGF or other neurotrophic factor genes in the non-neuronal cells around the site of injury.18 For example, NGF activity in the Schwann cells of sympathetically denervated rat iris is increased significantly.19 Because nerves in the heart may be injured during myocardial ischemia,20 it is reasonable to expect that nerve sprouting and NGF overexpression also occur after myocardial injury. Compatible with this expectation, Zhou et al14 found that acute myocardial ischemia in dogs causes an immediate (within 30 minutes) increase of transcardiac NGF concentration. In comparison, mRNA NGF and mRNA of growth-associated protein-43 (GAP43) began to increase 3 days after myocardial infarction and peaked 1 week later. We do not have data on postoperative day 1 or postoperative day 2 in that study. Because the increase of transcardiac NGF preceded the increase of mRNA NGF, the initial rise of transcardiac NGF most likely is due to the release of preformed NGF from the myocardium in response to massive myocardial injury. The subsequent elevation of NGF is due to overexpression of mRNA NGF. Unlike myocardial infarction, RF ablation does not damage a large amount of myocardium. Therefore, the initial release of NGF may be either small or undetectable. However, because of subsequent overexpression of mRNA NGF, the NGF concentration began to increase on postoperative day 1 and persisted for many days afterward.
Study limitations The number of patients is small. Therefore, whether or not NGF elevation is a reliable predictor of AF recurrence cannot be proven definitively by the data available in this study.
Conclusion RF catheter ablation does not increase transcardiac NGF concentrations immediately after the procedure. However, significant increases of venous NGF concentrations occur on postoperative day 1 and persist for at least 2 days afterward. The results support the hypothesis that RF ablation results in up-regulation of NGF expression in humans.
Acknowledgments We thank Ji-Hoon Kim, Hongmei Li, Su-Chao Ding, Lan S. Chen, Lei Lin, and Elaine Lebowitz for assistance and C. Thomas Peter for support.
References 1. Ehlert FA, Goldberger JJ, Brooks R, Miller S, Kadish AH. Persistent inappropriate sinus tachycardia after radiofrequency current catheter modification of the atrioventricular node. Am J Cardiol 1992;69:1092–1095. 2. Skeberis V, Simonis F, Tsakonas K, Celiker A, Andries E, Brugada P. Inappropriate sinus tachycardia following radiofrequency ablation of AV nodal tachycardia: incidence and clinical significance. Pacing Clin Electrophysiol 1994;17:924 –927. 3. Dagres N, Clague JR, Lottkamp H, Hindricks G, Breithardt G, Borggrefe M. Impact of radiofrequency catheter ablation of accessory pathways on the frequency of atrial fibrillation during long-term follow-up; high recurrence rate of atrial fibrillation in patients older than 50 years of age. Eur Heart J 2001;22: 423– 427. 4. Chiang CE, Chen SA, Wang DC, Tsang WP, Hsia CP, Ting CT, Chiang CW, Wang SP, Chiang BN, Chang MS. Arrhythmogenicity of catheter ablation in supraventricular tachycardia. Am Heart J 1993;125:388 –395. 5. Frey B, Kreiner G, Binder T, Heinz G, Baumgartner H, Gossinger HD. Relation between left atrial size and secondary atrial arrhythmias after successful catheter ablation of common atrial flutter. Pacing Clin Electrophysiol 1997;20:2936 – 2942. 6. Cosío FG, Gil ML, Goicolea A, Arribas F, Barroso JL. Radiofrequency ablation of the inferior vena cava-tricuspid valve isthmus in common atrial flutter. Am J Cardiol 1993;71:705–709. 7. Steinberg JS, Prasher S, Zelenkofske S, Ehlert FA. Radiofrequency catheter ablation of atrial flutter: procedural success and long-term outcome. Am Heart J 1995;130:85–92. 8. Kocovic DZ, Harada T, Shea JB, Soroff D, Friedman PL. Alterations of heart rate and of heart rate variability after radiofrequency catheter ablation of supraventricular tachycardia. Delineation of parasympathetic pathways in the human heart. Circulation 1993;88:1671–1681.
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Nerve Growth Factor and Radiofrequency Ablation
9. Vracko R, Thorning D, Frederickson RG. Fate of nerve fibers in necrotic, healing, and healed rat myocardium. Lab Invest 1990;63:490 –501. 10. Nori SL, Gaudino M, Alessandrini F, Bronzetti E, Santarelli P. Immunohistochemical evidence for sympathetic denervation and reinnervation after necrotic injury in rat myocardium. Cell Mol Biol 1995;41:799 – 807. 11. Cao J-M, Fishbein MC, Han JB, Lai WW, Lai AC, Wu T-J, Czer L, Wolf PL, Denton TA, Shintaku IP, Chen P-S, Chen LS. Relationship between regional cardiac hyperinnervation and ventricular arrhythmia. Circulation 2000;101: 1960 –1969. 12. Okuyama Y, Pak H-N, Miyauchi Y, Liu Y-B, Chou C-C, Hayashi H, Fu KJ, Kerwin WF, Kar S, Karagueuzian HS, Fishbein MC, Chen P-S, Lan LS. Sympathetic nerve sprouting induced by radiofrequency catheter ablation in dogs. Heart Rhythm 2005;1:712–717. 13. Rubart M, Zipes DP. Mechanisms of sudden cardiac death. J Clin Invest 2005;115:2305–2315. 14. Zhou S, Chen LS, Miyauchi Y, Miyauchi M, Kar S, Kangavari S, Fishbein MC, Sharifi B, Chen PS. Mechanisms of cardiac nerve sprouting after myocardial infarction in dogs. Circ Res 2004;95:76 – 83. 15. Chen P-S, Chou CC. Coronary sinus as an arrhythmogenic structure. J Cardiovasc Electrophysiol 2002;13:863– 864. 16. Ludinghausen MV, Ohmachi N, Boot C. Myocardial coverage of the coronary sinus and related veins. Clin Anat 1992;5:1–15. 17. Guth L. Regeneration in the mammalian peripheral nervous system. Physiol Rev 1956;36:441– 478. 18. Levi-Montalcini R. Growth control of nerve cells by a protein factor and its antiserum. Science 1964;143:105–110.
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19. Rush RA. Immunohistochemical localization of endogenous nerve growth factor. Nature 1984;312:364 –367. 20. Barber MJ, Mueller TM, Davies BG, Gill RM, Zipes DP. Interruption of sympathetic and vagal-mediated afferent responses by transmural myocardial infarction. Circulation 1985;72:623– 631. 21. Hadjiconstantinou M, McGuire L, Duchemin AM, Laskowski B, Kiecolt-Glaser J, Glaser R. Changes in plasma nerve growth factor levels in older adults associated with chronic stress. J Neuroimmunol 2001;116:102–106. 22. Parikh V, Evans DR, Khan MM, Mahadik SP. Nerve growth factor in nevermedicated first-episode psychotic and medicated chronic schizophrenic patients: possible implications for treatment outcome. Schizophr Res 2003;60:117–123. 23. Lambiase A, Bonini S, Bonini S, Micera A, Magrini L, Bracci-Laudiero L, Aloe L. Increased plasma levels of nerve growth factor in vernal keratoconjunctivitis and relationship to conjunctival mast cells. Invest Ophthalmol Vis Sci 1995;36: 2127–2132. 24. Matucci-Cerinic M, Giacomelli R, Pignone A, Cagnoni ML, Generini S, Casale R, Cipriani P, Del Rosso A, Tirassa P, Konttinen YT, Kahaleh BM, Fan PS, Paoletti M, Marchesi C, Cagnoni M, Aloe L. Nerve growth factor and neuropeptides circulating levels in systemic sclerosis (scleroderma). Ann Rheum Dis 2001;60:487– 494. 25. Lang UE, Gallinat J, Danker-Hopfe H, Bajbouj M, Hellweg R. Nerve growth factor serum concentrations in healthy human volunteers: physiological variance and stability. Neurosci Lett 2003;344:13–16. 26. Kaye DM, Vaddadi G, Gruskin SL, Du XJ, Esler MD. Reduced myocardial nerve growth factor expression in human and experimental heart failure. Circ Res 2000;86:E80 –E84.