Morphometric and Clinical Analysis of Moderator Band in Humans

Int ernat ional Journal of Anatomy and Research, Int J Anat Res 2015, Vol 3(4):1741-44. ISSN 2321- 4287 DOI: ht t p:/ / dx.doi.org/10.16965/ ijar.2015.342 Original Research Article M ORPHOM ETRIC AND CLINICAL ANALYSIS OF M ODERATOR BAND IN HUM ANS HannahSugirt habai RajilaRajendran * 1 , Ashok V ict or 2 , Gn anasund aram Vait hian at han 3 , Indum at hi Sundaram urt hi 4 , Th ot akura Bala ji 5 , Ja nani Yoganandham 6. * 1,5 Professor, Depart ment of Anat omy, Chett inad Hospital & Research Inst it ute, Kelambakkam, Chennai, Tamil Nadu, India. 2 Assistant Professor, Depart ment of Cardiology, Stanley M edical College, Chennai, Tamil Nadu, India. 3,6 Depart ment of Anat omy, Chett inad Hospital & Research Inst it ute, Kelambakkam, Chennai, Tamil Nadu, India. 4 Professor and HOD, Depart m ent of Anat om y, Chet t inad Hospit al & Research Inst it ut e, Kelambakkam, Chennai, Tamil Nadu, India. ABSTRACT Background: The m oderat or band has t he right bundle of His w it hin t he right vent ricle. It also is know n t o prevent t he over dilat at ion of RV. It is im portant because of it s involvem ent in RV infarct s, in different iat ing RV from LV in congenital anom alies, in VPDs & VTs and in VSDs. The present lit erat ure is very m uch lacking in it s morphom etry. M at erials and M ethods: M oderat or band w as looked for in 50 heart s and only in t his st udy did w e f ind it in all t he hear t s. The lengt h, t he t hickness, t he dist ance from t he t ricuspid valve along w it h t he pr esence of any t rabeculat ions in t he sept al end or in t he papillar y m uscle end w ere looked for and r ecorded. Results: The average lengt h w as 14.71±4.99m m , t he average t hickness w as 4.97±1.64 m m , t he average dist ance from t he t ricuspid orifice w as 19.85±5.92 m m . The at t achm ent t o t he ant erior papillary m uscle w as found t o be branched in 8 heart s t hat is having an incidence of 14% . The sept al end w ere br anched and separat ed as t w o in only t w o specim ens. Only one specim en had branched at t achm ent s on bot h t he apical and sept al ends. Conclusion: The dist ance from t ricuspid valve and know ledge of branching are im port ant in correct ive surgeries of t he VSDs. An aw areness of lengt h and t hickness helps t he clinician t o differ ent iat e m oderat or band from t he ot her st ruct ures, w hich m ay result in m isdiagnosis during echocardiography. It s presence m ay in fact be of significance in prevent ing over dist ension of t he heart in RV m yocardial ischaem ia. KEY WORDS: M oderat or Band, Right Vent ricle, Ant erior Papillar y M uscle, VSD, Tricuspid Valve. Address for Correspondence: Dr. HannahSugirt habai RajilaRajendran, M .S, Ph.D, Professor, Depart ment of Anat omy, Chett inad Hospital & Research Inst it ute, Kelambakkam, Chennai, Tamil Nadu, India. Pin – 603103 Phone No.: +919710403803 E-M ail: ashrajsanada@gmail.com Access this Article online Quick Response code Web site: Int ernat ional Journal of Anat omy and Research ISSN 2321-4287 ww w.ijmhr.org/ ijar.htm DOI: 10.16965/ ijar.2015.342 Int J Anat Res 2015, 3(4):1741-44. Received: 09 Oct 2015 Accept ed: 19 Dec 2015 Peer Review : 09 Oct 2015 Published (O): 31 Dec 2015 Revised: None Published (P): 31 Dec 2015 ISSN 2321-4287 1741 HannahSugir t habai RajilaRajendran et al. M ORPHOM ETRIC AND CLINICAL ANALYSIS OF M ODERATOR BAND IN HUM ANS. INTRODUCTION The moderat or band or sept omarginal t rabecula is seen in t he right vent ricle of t he heart . It is supposed t o st rengt hen t he sept al w all of t he right vent ricle and gains at t achm ent t o t he ant er ior papillar y m uscl e and t he par i et al vent r icular w all [1] . The m oderat or band is supposed t o regulat e t he dist ension of t he right vent ricle and hence it has derived t he nam e “ moderat or ”, as it contains t he right bundle of His. The moderat or band is a least st udied st ruct ure of t he human heart. There are very minimal w orks done on t he moderat or band. The main reaso n f or t hi s d ef i cien cy, is t h e p ract ical difficult y of view ing it in t he echocardiogram. This st udy aim s at t he various m orphological crit eria of moderat or band in human cadaveric hearts. The various crit eria included in t he st udy ar e l en gt h, t hi ck ness, d i st an ce f r o m t h e t r icuspid orif ice, it s appearance, num ber of connect ions t o t he ant erior papillary muscle, the nat ure of t issue (eit her muscular or fibrous) and any ot her variat ions encount ered during t he st udy. Hence, t his st udy aim s at creat ing a baseline dat a all about moderat or band. -ions, t he number of at t achment s t o t he ant erior papillary muscle and t he nat ure of t issue, w hether muscular or fibrous w ere looked for and recorded. Addit ionally, t here w ere t rabeculat ions observed in the septal end of the moderator band and t hey w ere also recoded. Fig. 1: M easur em ent of lengt h of m oderat or band. Fig. 2: M easurem ent of t hickness of m oderat or band. M ATERIALS AND M ETHODS The st udy on moderat or band w as done in t he Anat omy depart ment of Chet t inad Hospit al and Research Inst it ut e. A t ot al of fift y heart s w ere dissected for t his st udy. These heart s w ere all preserved in 10% formalin solut ion. The pericardium w as removed and t hen an incision parallel to the anterior inter ventricular groove was done. This incision w as t hen ext ended t o t he right a lit t le above t he inferior margin of t he heart and care was taken as not t o damage t he anterior papillary muscle or t he moderat or band. The digital Vernier caliper was used t o measure t he var ious cr it er ia. The lengt h w as m easur ed acr oss t he t w o ends of at t achm ent of t he moderat or band, namely t he sept al w all and t he ant erior papillary muscle. The t hickness w as m easured across t he t hickest port ion of t he m od er at o r b an d. The d ist ance f r o m t h e t ricuspid valve (TV) w as m easured from t he annulus of t he TV t o t he at t achm ent of t he m oder at or band t o t he sept al w all. It w as furt her classified int o near t he TV, midway or near t he apex. The presence of any t rabeculat Int J Anat Res 2015, 3(4):1741-44. ISSN 2321-4287 RESULTS The m oderat or band w as seen in all t he 50 heart s, hence report ing an incidence of 100%. The average lengt h of t he moderat or band w as 14.71±4.99mm (Fig.1). The average t hickness of t he moderat or band observed in t his st udy w as 4.97±1.64mm (Fig. 2) ranging bet w een 3.33mm t o 8.74mm. The average dist ance from t he t ricuspid orifice w as 19.85±5.92 mm ranging from 10.11mm t o 28.39mm. The at t achment of t he moderator band t o the ant erior papillary muscle (t he apical end) w as found t o be branched in 8 hearts (Fig. 3). All t he fift y moderat or bands were found t o be fibro-muscular in nat ure. The pariet al/ sept al end or t he at t achment of t he moderat or band t o t he int ervent ricular sept al w all w ere t rabeculat ed and separat ed as t w o in only t w o specimens out of t he 50 moderat or bands 1742 HannahSugir t habai RajilaRajendran et al. M ORPHOM ETRIC AND CLINICAL ANALYSIS OF M ODERATOR BAND IN HUM ANS. observed during t his st udy (Fig. 4). Only one specimen had branched att achments on both the apical and sept al ends (Fig. 5). Fig. 3: Branching at t he apical (ant erior papillary m uscle) end. TV: Tricuspid Valve, M B: M oderator Band, APM : Anterior Papillary M uscle, * Branching at Apical end. Fig. 4: Br anching at t he sept al (int ervent ricular sept al) end. M B: M oderator Band, SC: Septal Cusp * Branching at Septal end Fig. 5: Branching at bot h t he apical and sept al ends. TV: Tr i cu sp id Valve , M B: M o d e rat o r Ban d , SC: Se p t al Cu sp * Branching at Both ends Int J Anat Res 2015, 3(4):1741-44. ISSN 2321-4287 DISCUSSION The moderat or band is usually present in 90% of heart s [2], t hough in t his st udy it w as found in 100% of all t he 50 heart s st udied. It is oft en confused for one anot her t rabeculae carnea. It is an im port ant st ruct ure w hich has t he main right bundle of His of t he conduct ion syst em of heart and hence aids in t he right vent ricular free w all depolarisat ion. It also helps in prevent ing over dist ension of t he right vent ricle (RV), as it forms a bridge bet w een t he sept al w all and t he anterior wall of RV. Apart from t hese funct ions, it also helps in direct ing t he blood from t he inflow t ract t o t he out flow t ract of RV. The moderat or band is supplied by t he sept al art ery, w hich undergoes numerous anast omoses w it h ot her branches of t he sept al branches of t he right coronary art ery [3]. These numerous anast omoses are responsible for prot ect ion against massive RV infarct w hen t here is occlusion of t he proximal part of t he right coronary art ery [4]. M oderat or band is one of t he cont ribut ors for m isdiagnosis of int racardiac m asses. Even in fet us, it is know n t o cause specular reflect ions, in as high as 5.5% of t he cases [5]. Andre Keren et .al [6], has st at ed t hat using t w o dimensional echocardiography, m oderat or band can be visualised in 79% of t heir cases using an apical four chamber view, though t he normal incidence of moderat or band is about 90%. Using M mode echocardiography, t hey have reported t hat t here is significant difficult y in different iat ing t he right sid e of i nt er ven t r i cu lar sep t um f r o m t h e moderator band. In vent ricular sept al defect s (VSD), if t he region of t he moderat or band is involved, it is labelled as component 3 of VSD, according t o Richard van pragh et al. [7]. w hich is named as sept al band or proximal conal defect . While t reat ing such defect s, t he m oderat or band has t o be preserved carefully. M oderator bands are know n as u n iq u e si t es f or o r i gi n o f v en t r i cul ar t achyarrhyt hm ias and vent ricular prem at ure depol ar isat io ns. In a r ar e con dit ion called ar r yt h m o gen ic r i gh t v en t r i cu lar d ysp lasi a (ARVD), t he moderat or band is visualized as a highly t hick echogenic band and hence helps in different iat ing ARVD from RV ischaemia [8]. The same is also useful in dist inguishing RV from LV 1743 in congenit al anomalies as t here is no muscular or t rabecular attachment on t he LV [9]. M amat a et al. [10] has classified t he att achment of t he moderat or band int o single and double t ype. The single t ype show ed only one w hole st rip of moderat or band from t he sept al w all of right vent ricle t o t he ant erior papillary muscle. They had furt her divided t he single t ype int o simple and complex t ype, w here t he simple did not have branching pat t ern in t he at t achment t o t he papillary muscle but t here w ere branching pat t ern seen in t he complex t ype. In t he present study, t here were eight moderator bands belonging t o t he single but com plex t ype, w hereas, t he st udy done by M amat a et al. [10] show ed 10 such specimens out of t he 28 heart s studied. They have further report ed one anot her t ype as double, w here t here are t w o moderat or bands, going separat ely from sept al w all t o t he anterior papillary muscle t he w hole way. We did not come across such a finding, but in t w o out of the fift y heart s, t here were branching pat t ern seen in t he sept al end of t he moderat or band. The dist ance of moderat or band from t he t ricuspid valve is of import ance in t reat ing apical vent ricular sept al defect s. M arios Lukas et al. [11] have found t hat t he incidence of origin of moderat or bands close t o TV w as 13% (12 of 96 heart s), midw ay bet w een TV and t he apex w as 47% (45 of 96 heart s) and nearer t o t he apex was 40% (39 of 96 heart s). In t he current st udy, t hese w ere 25%, 40% and 35% respect ively. Hence, t he midw ay origin is more common, follow ed by t he apical origin and t hen t he nearer t o t he TV origin in bot h t he st udies. The t hickness also w ere very similar (4.5 ±1.8 mm and 4.97±1.64 mm) in bot h t hese st udies, w hereas, the average length w as 16.23 ± 2.3 mm in M arios Lukas et .al [11] st udy as against 14.71±4.99mm in t he present st udy. CONCLUSION The moderat or band is a very significant st ruct ure clinically. It can appear as a RV mass during echocardiography and be t he cause for diagnost ic confusions. It creat es addit ional st ress t o RV, w hen t here is myocardial infarct ion of t he right ventricle and hence prevents it s distension. M oderat or band by it self is a know n cause of vent ricular premat ure depolarisat ions (VPD) & Int J Anat Res 2015, 3(4):1741-44. ISSN 2321-4287 vent ricular t achyarryt hmias (VT) and can cause hindrance during pacing surgeries. As mentioned above, it s relat ion t o VSD is of ut most import ance as it may be accident ally cut during VSD repair surgeries. Hence, t he morphom et ry of moderat or band should be known to prevent any confusions clinically. ABBREVIATIONS RV - Right Vent ricle LV - Left Vent ricle VSD - Vent ricular Septal Defect VPD - Vent ricular Prem at ure Depolar isat ions VT- Vent ricular Tachyarr yt hm ias ARVD - Arryt hm ogenic Right Vent ricular Dysplasia Conflicts of Interests: None REFERENCES Susan St andr ing, Gr ay ’s Anat o m y, 40 t h edit io n , Chur chill Livingst o ne, Elsevier. [2]. Paul Ravindran, Solom on Victor. The m oderat or band, Indian Jo ur nal o f Tho r acic and Car dio vascular sur gery, Oct ober 1982;1(1):15-21. [3]. 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DOI: 10.1002/ ca.20968. 1744 How to cite this article : HannahSugir t habai RajilaRajendran, Ashok V ict or, Gnanasundaram Vait hianat han, Indum at hi Sundaram urt hi, Thotakura Balaji, Janani Yoganandham . M ORPHOM ETRIC AND CLINICAL ANALYSIS OF M ODERATOR BAND IN HUM ANS. Int J Anat Res 2015;3(4):1741-1744. DOI: 10.16965/ ijar.2015.342 HannahSugir t habai RajilaRajendran et al. M ORPHOM ETRIC AND CLINICAL ANALYSIS OF M ODERATOR BAND IN HUM ANS.