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Increased heart rate variability after radiofrequency ablation
Increased
Heart Rate Variability
After Radiofrequency
Ablation
Bernhard Frev, MD. Gottfried Heinz, MD. Gerhard Kreiqer, MD, Herwig Schmidinger, MD, Heinz Weber,-&lD,&d Heinz G&singer; MD adiofrequency ablation is a safe and highly effective modality of treatment for patients with atrioventricR ular (AV) nodal reentrant1and circus movement2,3tachycardias. Inappropriate sinus tachycardia has been described after the procedure.4Vagal withdrawal has been implicated in its occurrence, assuming damage of postganglionic parasympathetic fibers in the region of the AV node.4In the present study,heart rate (I-R) variability was analyzed after radiofrequency ablation to further characterizeany direct or indirect effect of radiofrequency energy on the sinus node. Sixteen patients (age 37 + 14 years, 11 women and 5 men, Ebstein’s anomaly in 2) underwent radiofequency ablation for dual AV nodal pathways (n = 4), left lateral accessory pathways (n = 4), right posteroseptal accessory pathways (n = 4) and right lateral accessory connections (n = 4). Sevenpatients (age 47 IL 13 years, 5 women and 2 men, Ebstein’s anomaly in 1) who had only diagnostic electrophysiologic study served as controls. All antiarrhythmic medications were withdrawn X4 hours before analysis of HR variability. Temperatureguided radiofrequency ablation was pet$ormed u&g the Osypka HAT 200 device and a 7Fr steerable, bipolar catheter with a 4 mm tip (Cerablate, Osypka). For control of AV nodal reentrant tachycardia, fast pathway ablation was peflormed in 4 patients. One patient had slow pathway ablation. Accessory pathway ablation From the Department of Cardiology, University of Vienna, Vienna, Austria: Dr. Frey’s current address is: Klinik fiir Innere Medizin II, Abteilung fiir Kardiologie, Wtiingergtirtel 18-20,1090Wien, Austria. Manuscript received October 1, 1992; revised manuscript received December 7, 1992,and acceptedDecember 9.
was peqormed at the atria1 or ventricular insertion site. In 2 patients with posteroseptal pathways, energy was delivered in the OSof the coronary sinus. Ablation end points were as follows: (1) selective elimination of slow or fast AV nodal pathway conduction, (2) elimination of accessorypathway conduction, and (3) noninducibility of AV nodal tachycardia after orciprenaline administration. These end points were achieved in all but 2 patients with accessory posteroseptal pathways and tricuspid regurgitation due to Ebstein’s anomaly. Holter recordings were processedfor HR variability using Marquette system8000 and softwareOOlA. For a tape to be included in the study, it had to have >12 hours of analyzable data with sinus rhythm as the basic rhythm. The total spectral power in thefrequency range 0.01 to 1.OOHz (PS tot), and the SD of the j-minute mean RR interval (SDANN) were computed. Data are expressedas mean * 1 SD. Comparisons of continuous variables between 2 groups were performed using Mann Whitney U test. Spearman’sr was used to assesscorrelation of data. In 3 patients, nonsustained atria1 tachycardia occurred after the procedure. A greater HR variability was seen in 10 of 12 patients with ablation of lef latera1 and right posteroseptal pathways, or selectivefast or slow pathway ablation than in control subjects (PS tot 56 f 22 vs 34 * 10 ms [p = 0.031; SDANN 107 ? 31 vs 79 + 7 ms [p = 0.021) (Figure 1 and Table I). No signij?cant change in HR variability wasfound in 4 patients who underwent ablation of right lateral pathways (PS tot 31 IL 7 vs 34 f 10 ms [p = NS]; SDANN 77 & 18 vs 79 IL 7 ms (p = NS]; patients vs controls). There was a weak but signijicant correlation betweenparameters of HR variability and cumulative radiofrequency
Recording A
FIGURE 1. Power spectral density curves in a 22-yeaMd woman with multiple po& teroseptal accessory pathways. Recordiw A was obtained immediately after diagnostic electrophysiology. Recording B was obtained immediately after radie requency ablation, which was performed 6 days apart from diagnostic procedure. avg = average; mean RR = average RR interval during recording period; SDANN = SD of 6-minute mean RR intervals; PS tot q total spectral power in 0.01-1.00 Hz frequency range.
Recording B
0 ms
1460
THE AMERICANJOURNALOF CARDIOLOGY VOLUME71
JUNE 15. 1993
TABLE I Amount of Cumulative Energy Applied and Heart Rate Variability After Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentry or Circus Movement Tachycardias Ablation LL, PS,”
Sites
AVNRT
Energy(W) Mean SDANN
RR (ms) (ms)
PStot (ms)
88,642 -c 10,857 926 2 109 107
56t
?I 31
22
Control
RL
(n = 12)
(n = 4)
6,730 ‘746 t 77 zi 31i
Subjects
(n =
3,857 83 18 7
7)
Q+O 848 + 93 79 F 7 342 10
p Valuet
NS 0.02 0.03
‘Includes ineffective ablation in 2 patients with poskwxeptal pathways and tricuspid regurgitation due to Ebstein’s anomaly. tMann-Whitney IJ test between LL, PS, AVNRT and control subjects AVNRT = atrioventrlcular nodal reentry tachycardla; LL = left lateral accessory pathway; mean RR = mean RR averaged overentlre Holterrecording; PS = posteraseptal accessory pathway; PS tot = total spectral power m 0.01-1.00 Hzfrequency range; RL = right lateral accessory pathway; SDANN = SD of 5minute mean RR intervals.
energy upplied for the group of patients undergoing ahl&ion of left lateral or posteroseptal accessory pathways, or fast or slow AV nodal pathways (PS tot: r = 0.54 [p = 0.021; SDANN: r = 0.52 [p = 0.02]). In a previous report, Ehlert et aI observedthe occurrence of inappropriate sinus tachycardia in 3 patients after radiofrequency modification of the AV nodal junction. This was attributed to vagal withdrawal, possibly following damage of autonomic fibers in the AV junctional groove. Furthermore, they observedan association between the occurrence of sinus tachycardia and an increasednumber of radiofrequency energy applications. In the present study, values for SDANN and PS tot were greater after radiofrequency ablation and correlated with the amount of energy applied, except in patients after right-sided pathway ablation. The reasonsfor an increasedHR variability after radiofrequency ablation are not completely understood. Regardlessof the mechanism of these changesin sinus activity related to radiofrequency ablation, the assumption of vagal withdrawal is not supported by the present data. A shift in autonomic balance due to vagal withdrawal would be expected to manifest itself with a decreasein SDANN and PS tot.5 There are several hypotheses to explain these findings. First, the electromagnetic field generatedby radiofrequency energy may exert a direct effect on the sinus node. The geometry of this field has not been determined. However, with the medium wave lengths used in radiofrequency ablation, it would be reasonableto think of the catheter as a large antenna, with the field spreading radially around it, and extending between the catheter tip and the back electrode. The effects on the sinus node should critically depend on the amount of energy applied.HR variability correlatedto the cumulativeamount of radiofrequency energy. Second, there could be an enhancement in vagal tone. Postganglionic parasympathetic fibers innervating
the sinus node cross the AV groove.h It is possible that these fibers are stimulated by radiofrequency ablation in the proximate vicinity with consecutive increased vagal intluence on the sinus node. However, it is unclear why this effect persists >12 hours after the ablation procedure. The tiuence of the ablation site on HR variability is not explained by either of the aforementioned hypotheses. One would expect that both the distance between the ablation site and sinus node or vagal fibers, and the amount of energy applied determine the effects under study. Therefore, it is not easy to understand why right-sided ablation should have no effect on HR variability, becauseconsiderable amounts of energy were applied on the right side. Moreover, the right lateral ablation sites are located closer to the sinus node or to vagal fibers in the AV groove than are the left lateral sites, and vagal fibers are not known to cross the mitral annulus. In summary, this study found an increasedHR variability after radiofrequency ablation that correlated to the amount of cumulative energy applied, consistent with either a far-field effect on the sinus node or increasedvagal tone. 1. Jawyeri MR, Hempe SL, Sra JS, Dhala AA, Blanck Z, Deshpande SS, Awall B, Krum DP, Gilbert CJ, Akhta M. Selective tmnscalheter ablation of the fast and slow pathways using radiofrequency energy in patients with attiovenwicular nodal reentrant tachycxdia. C~rculnfion 1992;85:13 IX- 1328. 2. Jackman WM, Wang X, Friday KJ, Roman CA, Moulton KP, Beckman KJ, McClelland JH, Twiddle N, Ha&t HA, Plier Ml, Margolis PD, C&me JD, Overholt ED, Lazzara R. Catheter ablation of accessory pathways (Wolff-ParkinsonWhite syndrome) by radiofrequency current. N Engl .I Med 199 1;324:1605-1611. 3. Gallagher JJ, Pritchctt ELC, Scaly WC, Kascil J, Wallace AG. The pexcilation syndromes. Prog Cardiovasc Dis 1978$X:285-327. 4. Ehlert FA, Goldberga JJ, Brooks R, Miier S, Kadish AH. Persntcnt mxppro-
p&e
sinus
tachycxdia
after
radiofkquency
cul~ent
catheter
modification
of the
atrioventriculw node. Am J Cur&l 1992;69:1092-1095. 5. VybiiaI T, Bryg RJ, Maddens ME, Boden WE Effects of passive tilt on sympathetic and parasympathetic components 01 haart rate variability in normal subjects. Am .I Car&l 1989;63:1117-1120. 6. Randall WC, Ardell JL. Nervous control of the hean: anatomy and pathophysiology. In: zlpcs DP, Jalife J, eds. Cardiac Eleclrophysiology: From Cell to Bedside. Philadelphia: W. B. Saunders, 19901291-299.
BRIEFREPORTS 114
Heart Rate Variability
After Radiofrequency
Ablation
Bernhard Frev, MD. Gottfried Heinz, MD. Gerhard Kreiqer, MD, Herwig Schmidinger, MD, Heinz Weber,-&lD,&d Heinz G&singer; MD adiofrequency ablation is a safe and highly effective modality of treatment for patients with atrioventricR ular (AV) nodal reentrant1and circus movement2,3tachycardias. Inappropriate sinus tachycardia has been described after the procedure.4Vagal withdrawal has been implicated in its occurrence, assuming damage of postganglionic parasympathetic fibers in the region of the AV node.4In the present study,heart rate (I-R) variability was analyzed after radiofrequency ablation to further characterizeany direct or indirect effect of radiofrequency energy on the sinus node. Sixteen patients (age 37 + 14 years, 11 women and 5 men, Ebstein’s anomaly in 2) underwent radiofequency ablation for dual AV nodal pathways (n = 4), left lateral accessory pathways (n = 4), right posteroseptal accessory pathways (n = 4) and right lateral accessory connections (n = 4). Sevenpatients (age 47 IL 13 years, 5 women and 2 men, Ebstein’s anomaly in 1) who had only diagnostic electrophysiologic study served as controls. All antiarrhythmic medications were withdrawn X4 hours before analysis of HR variability. Temperatureguided radiofrequency ablation was pet$ormed u&g the Osypka HAT 200 device and a 7Fr steerable, bipolar catheter with a 4 mm tip (Cerablate, Osypka). For control of AV nodal reentrant tachycardia, fast pathway ablation was peflormed in 4 patients. One patient had slow pathway ablation. Accessory pathway ablation From the Department of Cardiology, University of Vienna, Vienna, Austria: Dr. Frey’s current address is: Klinik fiir Innere Medizin II, Abteilung fiir Kardiologie, Wtiingergtirtel 18-20,1090Wien, Austria. Manuscript received October 1, 1992; revised manuscript received December 7, 1992,and acceptedDecember 9.
was peqormed at the atria1 or ventricular insertion site. In 2 patients with posteroseptal pathways, energy was delivered in the OSof the coronary sinus. Ablation end points were as follows: (1) selective elimination of slow or fast AV nodal pathway conduction, (2) elimination of accessorypathway conduction, and (3) noninducibility of AV nodal tachycardia after orciprenaline administration. These end points were achieved in all but 2 patients with accessory posteroseptal pathways and tricuspid regurgitation due to Ebstein’s anomaly. Holter recordings were processedfor HR variability using Marquette system8000 and softwareOOlA. For a tape to be included in the study, it had to have >12 hours of analyzable data with sinus rhythm as the basic rhythm. The total spectral power in thefrequency range 0.01 to 1.OOHz (PS tot), and the SD of the j-minute mean RR interval (SDANN) were computed. Data are expressedas mean * 1 SD. Comparisons of continuous variables between 2 groups were performed using Mann Whitney U test. Spearman’sr was used to assesscorrelation of data. In 3 patients, nonsustained atria1 tachycardia occurred after the procedure. A greater HR variability was seen in 10 of 12 patients with ablation of lef latera1 and right posteroseptal pathways, or selectivefast or slow pathway ablation than in control subjects (PS tot 56 f 22 vs 34 * 10 ms [p = 0.031; SDANN 107 ? 31 vs 79 + 7 ms [p = 0.021) (Figure 1 and Table I). No signij?cant change in HR variability wasfound in 4 patients who underwent ablation of right lateral pathways (PS tot 31 IL 7 vs 34 f 10 ms [p = NS]; SDANN 77 & 18 vs 79 IL 7 ms (p = NS]; patients vs controls). There was a weak but signijicant correlation betweenparameters of HR variability and cumulative radiofrequency
Recording A
FIGURE 1. Power spectral density curves in a 22-yeaMd woman with multiple po& teroseptal accessory pathways. Recordiw A was obtained immediately after diagnostic electrophysiology. Recording B was obtained immediately after radie requency ablation, which was performed 6 days apart from diagnostic procedure. avg = average; mean RR = average RR interval during recording period; SDANN = SD of 6-minute mean RR intervals; PS tot q total spectral power in 0.01-1.00 Hz frequency range.
Recording B
0 ms
1460
THE AMERICANJOURNALOF CARDIOLOGY VOLUME71
JUNE 15. 1993
TABLE I Amount of Cumulative Energy Applied and Heart Rate Variability After Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentry or Circus Movement Tachycardias Ablation LL, PS,”
Sites
AVNRT
Energy(W) Mean SDANN
RR (ms) (ms)
PStot (ms)
88,642 -c 10,857 926 2 109 107
56t
?I 31
22
Control
RL
(n = 12)
(n = 4)
6,730 ‘746 t 77 zi 31i
Subjects
(n =
3,857 83 18 7
7)
Q+O 848 + 93 79 F 7 342 10
p Valuet
NS 0.02 0.03
‘Includes ineffective ablation in 2 patients with poskwxeptal pathways and tricuspid regurgitation due to Ebstein’s anomaly. tMann-Whitney IJ test between LL, PS, AVNRT and control subjects AVNRT = atrioventrlcular nodal reentry tachycardla; LL = left lateral accessory pathway; mean RR = mean RR averaged overentlre Holterrecording; PS = posteraseptal accessory pathway; PS tot = total spectral power m 0.01-1.00 Hzfrequency range; RL = right lateral accessory pathway; SDANN = SD of 5minute mean RR intervals.
energy upplied for the group of patients undergoing ahl&ion of left lateral or posteroseptal accessory pathways, or fast or slow AV nodal pathways (PS tot: r = 0.54 [p = 0.021; SDANN: r = 0.52 [p = 0.02]). In a previous report, Ehlert et aI observedthe occurrence of inappropriate sinus tachycardia in 3 patients after radiofrequency modification of the AV nodal junction. This was attributed to vagal withdrawal, possibly following damage of autonomic fibers in the AV junctional groove. Furthermore, they observedan association between the occurrence of sinus tachycardia and an increasednumber of radiofrequency energy applications. In the present study, values for SDANN and PS tot were greater after radiofrequency ablation and correlated with the amount of energy applied, except in patients after right-sided pathway ablation. The reasonsfor an increasedHR variability after radiofrequency ablation are not completely understood. Regardlessof the mechanism of these changesin sinus activity related to radiofrequency ablation, the assumption of vagal withdrawal is not supported by the present data. A shift in autonomic balance due to vagal withdrawal would be expected to manifest itself with a decreasein SDANN and PS tot.5 There are several hypotheses to explain these findings. First, the electromagnetic field generatedby radiofrequency energy may exert a direct effect on the sinus node. The geometry of this field has not been determined. However, with the medium wave lengths used in radiofrequency ablation, it would be reasonableto think of the catheter as a large antenna, with the field spreading radially around it, and extending between the catheter tip and the back electrode. The effects on the sinus node should critically depend on the amount of energy applied.HR variability correlatedto the cumulativeamount of radiofrequency energy. Second, there could be an enhancement in vagal tone. Postganglionic parasympathetic fibers innervating
the sinus node cross the AV groove.h It is possible that these fibers are stimulated by radiofrequency ablation in the proximate vicinity with consecutive increased vagal intluence on the sinus node. However, it is unclear why this effect persists >12 hours after the ablation procedure. The tiuence of the ablation site on HR variability is not explained by either of the aforementioned hypotheses. One would expect that both the distance between the ablation site and sinus node or vagal fibers, and the amount of energy applied determine the effects under study. Therefore, it is not easy to understand why right-sided ablation should have no effect on HR variability, becauseconsiderable amounts of energy were applied on the right side. Moreover, the right lateral ablation sites are located closer to the sinus node or to vagal fibers in the AV groove than are the left lateral sites, and vagal fibers are not known to cross the mitral annulus. In summary, this study found an increasedHR variability after radiofrequency ablation that correlated to the amount of cumulative energy applied, consistent with either a far-field effect on the sinus node or increasedvagal tone. 1. Jawyeri MR, Hempe SL, Sra JS, Dhala AA, Blanck Z, Deshpande SS, Awall B, Krum DP, Gilbert CJ, Akhta M. Selective tmnscalheter ablation of the fast and slow pathways using radiofrequency energy in patients with attiovenwicular nodal reentrant tachycxdia. C~rculnfion 1992;85:13 IX- 1328. 2. Jackman WM, Wang X, Friday KJ, Roman CA, Moulton KP, Beckman KJ, McClelland JH, Twiddle N, Ha&t HA, Plier Ml, Margolis PD, C&me JD, Overholt ED, Lazzara R. Catheter ablation of accessory pathways (Wolff-ParkinsonWhite syndrome) by radiofrequency current. N Engl .I Med 199 1;324:1605-1611. 3. Gallagher JJ, Pritchctt ELC, Scaly WC, Kascil J, Wallace AG. The pexcilation syndromes. Prog Cardiovasc Dis 1978$X:285-327. 4. Ehlert FA, Goldberga JJ, Brooks R, Miier S, Kadish AH. Persntcnt mxppro-
p&e
sinus
tachycxdia
after
radiofkquency
cul~ent
catheter
modification
of the
atrioventriculw node. Am J Cur&l 1992;69:1092-1095. 5. VybiiaI T, Bryg RJ, Maddens ME, Boden WE Effects of passive tilt on sympathetic and parasympathetic components 01 haart rate variability in normal subjects. Am .I Car&l 1989;63:1117-1120. 6. Randall WC, Ardell JL. Nervous control of the hean: anatomy and pathophysiology. In: zlpcs DP, Jalife J, eds. Cardiac Eleclrophysiology: From Cell to Bedside. Philadelphia: W. B. Saunders, 19901291-299.
BRIEFREPORTS 114