REVIEW ARTICLES International Journal of Arrhythmia 2017;18(1):38-42 doi: http://dx.doi.org/10.18501/arrhythmia.2017.005 Supraventricular Tachycardia by Concealed Bypass Tract 이기홍 전남대학교의과대학내과학교실 Ki Hong Lee, MD, PhD Cardiovascular Medicine, The Heart Center of Chonnam National University Hospital, Republic of Korea Received: June 21, 2016 Revision Received: November 3, 2016 Accepted: January 4, 2017 Correspondence: Ki Hong Lee, MD, PhD Cardiovascular Medicine, The Heart Center of Chonnam National University Hospital, 42, Jebong-ro, Dong-gu, Gwangju 61469, Republic of Korea Tel: +82-62-220-6246, Fax: +82-62-223-3105, E-mail: drgood2@naver.com Copyright 2017 The Official Journal of Korean Heart Rhythm Society Editorial Board & MMK Co., Ltd. ABSTRACT Concealed bypass tract (CBT) results from incomplete development of the atrioventricular (AV) annulus. CBT conducts only in a retrograde direction, and therefore does not cause pre-excitation on standard electrocardiograms. The most common tachycardia associated with CBT is an orthodromic atrioventricular reentrant tachycardia (AVRT): a pathway involving anterograde circuitry through the AV node and His Purkinje system and retrograde conduction over the accessory pathway. Orthodromic AVRT accounts for approximately 90%-95% cases of AVRT. Most incidences of CBT occur at the left free wall. Vagal maneuvers and/or intravenous (IV) adenosine are recommended for first line acute management of AVRT. However, pharmacological therapy with IV diltiazem, verapamil, or beta blockers can also be effective for acute treatment for orthodromic AVRT in patients who do not show pre-excitation on their resting ECG during sinus rhythm. The first-line ongoing therapy for AVRT is catheter ablation of CBT; when catheter ablation is not indicated or preferred, oral beta blockers, diltiazem, verapamil, flecainide, propafenone, or amiodarone are recommended. Key Words: Supraventricular Tachycardia AVNRT 서론 방실우회로는방실륜 (AV annulus) 의불완전한발생에의해생성되어방실결절에비해빠른전도속도를특징으로하는비정상심근세포군이다. 방실우회로는주로심방과심실사이의방실륜 (AV annulus) 에존재한다. 좌측벽 (50%) 에가장많이존재하고, 후중격 (20-30%), 우자유벽 (10-20%), 전중격 (5-10%) 순으로존재한다고알려져있다. 방실우회로는현성 또는불현성으로구분할수있고, 전향적, 후향적또는양방향으로전도가가능하다. 이중에서불현성방실우회로 (concealed bypass tract, CBT) 는후향적전도만이가능하므로, 심전도에서조기흥분 (pre-excitation) 이관찰되지않는다. 1 본종설에서는불현성방실우회로로유발될수있는심실상빈맥의종류와기전, 급성기및유지치료방법에대해알아보고자한다. 38
Supraventricular Tachycardia by Concealed Bypass Tract 방실회귀성빈맥의병태생리 방실우회로는정상전도계와순환회로를구성하여다양한종류의상심실성빈맥을유발한다. 가장흔히발생하는빈맥은정방향성방실회귀성빈맥 (orthodromic atrioventricular reentrant tachycardia, AVRT) 이다. 정방향성방실회귀성빈맥은전도계가방실결절과히스속을이용한방실전도계를타고심실까지내려가반대방향으로방실우회로를타고올라와서다시심방과방실결절까지전도되어회귀회로를완성한다. 정방향성방실회귀성빈맥은전체방실회귀성빈맥빈도의 90%-95% 를차지하며, 발작성심실상빈맥의약 35% 를차지한다. 일반적으로방실우회로는전향적전도가불가능하므로조기흥분을유발시키지않는다. 그런데조기흥분이보이지않는다고해서전부다전향적전도가불가능한방실우회로로간주해서는안된다. 원래양방향전도가가능한방실우회로임에도불구하고간헐적으로조기흥분이보이지않아마치후향적전도만이가능한방실우회로로보일수있기때문이다. 이러한성격을가진방실우회로는전체방실회귀성빈맥의약 5% 정도를차지하는역방향성방실회귀성빈맥 (antidromic AVRT) 을유발할수있다. 역방향성방실회귀성빈맥은전도계가심방에서심실로방실우회로를타고내려가서방실결절을타고올라와회귀회로를완성한다. 전방향성방실회귀성빈맥은심방과심실이순차적으로탈분극되고정상방실전도계를통한전도속도가방실우회로를통한전도속도보다느리기때문에 PR 간격이 RP 간격보다길어 P파가 QRS파뒤에나오게된다. 역방향성방실회귀성빈맥은심실의탈분극이방실우회로를타고내려간자극에의해비정상적으로전파되기때문에심실빈맥에서처럼 QRS 파의폭이넓어지게된다. 대부분의방실우회로는심근과비슷한전도특성을지니므로감쇠전도 (decremental property) 를보이지않는다. 그런데방실우회로가우중격부위에존재할경우후향적감쇠전도를보일수있는전방향성방실회귀성빈맥을유발할수있고, 이를지속성접합부회귀성빈맥 (permanent junctional reentrant tachycardia, PJRT) 이라고한다. 이빈맥은특징적으로하벽유도심전도 (II, III, avf) 에서깊게반전된후향적 P파를보이고, 우회로의점감특성 (diminishing characteristic) 으로인해긴 RP 간격을보인다. 또다른비전형적방실우회로는심방섬유속 (atriofascicular fiber; Mahaim fiber) 이다. 심방섬유속은우심방과우각의원위섬유속을연결하고전향적감쇠전도를보이지만후향적전도는불가능하다. 심방섬유속에의해발생한방실회귀성빈맥은좌각차단형태를보이며, 방실우회로를통하여전향적으로전도되고방실결절과히스속을이용하여후향적으로전도되어회귀회로를완성한다. 드문방실우회로인결절섬유속 (nodofascicular pathway) 회로는방실결절과심근을연결하여방실회귀성빈맥을유발한다. 드물게섬유속과우각또는좌각의근위부와연결하는방실우회로가보고되기는하였으나빈맥을유발하지는않는다고알려져있다. 방실회귀성빈맥의급성기치료요법 방실회귀성빈맥환자의상태가위급하지않다면미주신경항진술 (vagal maneuver) 과 adenosine 정맥투여를첫번째로시행할수있다 (class of recommendation I, level of evidence B). 미주신경항진술은발살바수기 (Valsalva maneuver) 와경정맥동마사지 (carotid sinus massage) 가있으며신속하게시행할수있다. 발살바수기는반드시환자가누운상태에서시행해야하고숨을참으면서성문 (glottis) 를 10-30초간막아흉강내압력을 30-40 mmhg 정도올린다. 2,3 경정맥동마사지는경동맥에서혈관잡음이들리지않는경우에시행해야하고좌측이나우측경정맥동을 5-10초간지긋이누른다. 2-4 Adenosine은방실회귀성빈맥을 90-95% 정도종료시키는효과적인치료방법이다 (class of recommendation I, level of evidence B). 5,6 Adenosine은심방세동을유발시킬수있고또한심방세동은방실우회로를통하여심실로빠르게전달되어심실세동을유발시킬수있으므로반드시직류충격기가준비된상태에서주사해야한다. 미주신경항진술을시행할수없거나 adenosine 정맥투여에반응이없으면서혈역학적으로불안정할경우직류충격심율동전환을시행한다 (class of recommendation I, level of evidence B). 7 또한다른약물치료에반응이없거나금기이면서혈역학적으로불안정하다면직류충격심율동전환을시행한다 (class of recommendation I, level of evidence B). 8,9 혈역학적으로안정되어있다면 diltiazem, verapamil(class 39
International Journal of Arrhythmia 2017;18(1):38-42 of recommendation IIa, level of evidence B), 5,10-12 베타차단제 (class of recommendation IIa, level of evidence C) 13 등의약물을정맥투여할수있다. 이러한약제들은평상시심전도에서조기흥분이없는정방향성방실회귀성빈맥의종료에효과적이다 (Figure 1). 방실회귀성빈맥의유지요법 방실회귀성빈맥의근본적치료이자첫번째치료는전극도자절제술이다 (class of recommendation I, level of evidence B). 14,15 전극도자절제술의성공율은 93-95% 로보고되며약 3% 의환자에서주요부작용이발생한다고알려져있다. 전극도자절제술을시행할수없거나추천되지않는경우경구베타차단제, diltiazem, vepramil이방실회귀성빈맥예방약제로추천된다 (class of recommendation I, level of evidence C). 16,17 만약구조적심질환이나허혈성심질환의과거력이없다면경구 flecainide와 propafenone이 대체약제로추천된다 (class of recommendation IIa, level of evidence B). 18,19 Flecainide와 propafenone은방실우회로의전도를늦추거나중단시켜방실회귀성빈맥발생을예방한다. 만약구조적심질환이나허혈성심질환의과거력이있다면경구 dofetilide와 sotalol이추천된다 (class of recommendation IIb, level of evidence B). 20 이들약제의경우 QT 간격을연장시키고 torsa de pointes를유발할수있으므로주기적으로심전도를시행해야한다. 위의모든약제에반응이없거나금기이면서전극도자절제술을시행할수없고금기인경우경구 amiodarone을사용해볼수있다 (class of recommendation IIb, level of evidence C). 21 Digoxin도방실회귀성빈맥예방목적으로사용될수있지만효용성이낮아최근에거의사용되고있지않고있으므로위의모든약제에반응이없거나금기이면서전극도자절제술을시행할수없고금기인경우사용해볼수있다 (class of recommendation IIb, level of evidence C) (Figure 2). 22 Figure 1. Acute Treatment of Orthodromic AVRT. AVRT, atrioventricular reentrant tachycardia; IV, intravenous. 40
Supraventricular Tachycardia by Concealed Bypass Tract Figure 2. Ongoing management of orthodromic AVRT. AVRT, atrioventricular reentrant tachycardia References 1) Page RL, Joglar JA, Caldwell MA, Calkins H, Conti JB, Deal BJ, Estes NA, 3rd, Field ME, Goldberger ZD, Hammill SC, Indik JH, Lindsay BD, Olshansky B, Russo AM, Shen WK, Tracy CM, Al-Khatib SM. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia: a report of the American College of Cardiology/American Heart Association task force on clinical practice guidelines and the Heart Rhythm Society. J Am Coll Cardiol. 2016;67:e27-e115. 2) Waxman MB, Wald RW, Sharma AD, Huerta F, Cameron DA. Vagal techniques for termination of paroxysmal supraventricular tachycardia. Am J Cardiol. 1980;46:655-664. 3) Lim SH, Anantharaman V, Teo WS, Goh PP, Tan AT. Comparison of treatment of supraventricular tachycardia by Valsalva maneuver and carotid sinus massage. Ann Emerg Med. 1998;31:30-35. 4) Luber S, Brady WJ, Joyce T, Perron AD. Paroxysmal supraventricular tachycardia: outcome after ED care. Ann Emerg Med. 2001;19:40-42. 5) Delaney B, Loy J, Kelly AM. The relative efficacy of adenosine versus verapamil for the treatment of stable paroxysmal supraventricular tachycardia in adults: A meta-analysis. Eur J Emerg Med. 2011;18:148-152. 6) Furlong R, Gerhardt RT, Farber P, Schrank K, Willig R, Pittaluga J. Intravenous adenosine as first-line prehospital management of narrow-complex tachycardias by ems personnel without direct physician control. Am J Emerg Med. 1995;13:383-388. 7) Neumar RW, Otto CW, Link MS, Kronick SL, Shuster M, Callaway CW, Kudenchuk PJ, Ornato JP, McNally B, Silvers SM, Passman RS, White RD, Hess EP, Tang W, Davis D, Sinz E, Morrison LJ. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2010;122:S729-S767. 8) Brady WJ, Jr., DeBehnke DJ, Wickman LL, Lindbeck G. Treatment of out-of-hospital supraventricular tachycardia: adenosine vs verapamil. Acad Emerg Med. 1996;3:574-585. 9) Stec S, Krynski T, Kulakowski P. Efficacy of low energy rectilinear 41
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