1017

Dimension and Related Anatomical Distance ofKoch's Triangle in Patients with Atrioventricular

Nodal Reentrant Tachycardia

KWO-CHANG UENG. M.D., SHIH-ANN CHEN, M.D., CHERN-EN CHIANG, M.D.CHING-TAI TAI. M.D., SHIH-HUANG LEE, M.D., CHUEN-WONG CHIOU, M.D.,

ZU-CHI WEN, M.D., CHI-JEN TSENG, M.D.. YI-JEN CHEN, M.D.,WEN-CHUNG YU, M.D., CHUNG-YIN CHEN, M.D.,

and MAU-SONG CHANG, M.D.

From the Division of Cardiology, Department of Medicine. National Yang-Ming University. School of Medicine,and Veterans General Hospital-Kaohsiung and Taipei. Taiwan, Republic of China

Koch ' s Tr iangle in AVNRT. Introduction: The dimension of Koch's triaiiftle in patientswith AV nodal reentrant tachycardia has not been well described. Understanding the dimen-sion and anatomical distance related to Koch\ triangle might be useful in avoiding accidentalAV block during ablation of the slow pathway. The purposes of this study were to define thedimension of Koch^s triangle and its related anatomical distance and correlate these parame-ters with the successful ahlation sites in patients with AV nodal reentrant tachycardia.

Methods and Results: We studied 218 patients with AV nodal reentrant tachycardia. Thedistance hetween the presumed proximal His-bundle area and the base of the coronary sinusorifice (D|,i .,m) measured in the right anterior ohiiqne view was used to define the dimension ofKoch's triangle. The distance of the proximal His-bundle recording site from the successful ab-lation site (DHJ^.^^) and the distance as a fraction of the entire length of Koch's triangle (DHi . /t*iiis-()s) w* ''c determined. The mean D||i .os and D,,i , ,, were 25.9 ± 7.9 and 13.4 ± 3.8 mm, re-spectively. Dfii o negatively correlated with patient age (r = -4).41, P < 0.0001) and body massindex (r = -0.18, P = 0.004). Among the patients with successful ahlation sites in the medialarea, Dni,.(>, was longer {27.2 ± 6.6 vs 24.6 ± 8.4 mm, P < 0.005), D|,i,., h was similar (12.9 ± 3.1vs 13.9 ±4.0, P > 0.05) and D,!,, ,b/I>ni.-.>. was smaller (0.48 ± 0.04 vs 0.74 ± 0.11, P < 0.05). Fur-thermore, the patients with successful ablation sites in the medial location needed more ra-diofrequency pulse numbers than those in the posterior location (6 ± 4 vs 4 ± 3, P < 0.05).

Conclusion: The site of successful slow pathway ablation was consistently about 13 mm fromthe site recording tbe proximal His-bundle deflection in patients with AV nodal reentranttachycardia despite marked variability in tbe dimensions of Koch's triangle: therefore, patientswith large trian|;les required ablation in tbe medial region ratber tban the posterior region.Care sbould be taken when delivering radiofrequency energy to the posteroseptal area in pa-tients with shorter DHJS.OS to avoid injury to AV node. fJ Cardiovasc Electruphysiol, Vol. 7, pp.J0I7'I023, November 1996)

Koch's triangle, atrioventricular nodal reentrant tachycardia, radiofrequency ablation

Supported in pan by grants frdni the National Science Council Introduction(NSC-85-233i-B075-()7l and85-23.1l-B01()-047)andthe Acade- r. J - 4- u . ui .• c .u tmiaSinica. Taipei. Taiwan. Republic of China. Radiofrequency catheter ablation of the slow

pathway is highly effective in elimitiating AV mxlalAddress tor correspondence: Shih-Ann Chen, M.D.. Division of .-«,.,.•..„«» .„„! ^,v,.. ...i.u ..« «..»;.«..*-»^ ^^i^ ,.f,, ,. , X, . r- r u . I T fll c -v cu i. reentrant tacnycaruia, wttn an est imated n s k otCardiology. Veierans General Hospital-Taipei. 201 Sec 2. Shih- •"Pai Road. Taipei. Taiwan. Repuhlic of China. Fax: 886-2- Complete AV block about 1%.' ^ Both the slow and87356. 6. fast pathways are located within Koch's triangle.

Manuscript received 7 March 19%; Accepted for publication 28 » Structure that varies widely among patients. MoreJune 1996. careftil definition of its anatomy may facilitate ra-

1018 Journal of Cardiovascular Electrophysiology Vol. 7, No. U, November 1996

diofrequency ablation and decrease the risk of com-plete AV block.'* The purposes of this study were:(1) to measure the dimensions of Koch's triangle;and (2) to determine the relation between the di-mension of Koch's triangle and the successfulablation site in patients with AV nodal reentranttachycardia.

Materials and Methods

Patient Population

This study included 218 consecutive patientswho had clinically documented AV nodal reentranttachycardia and were referred to receive radiofre-quency catheter ablation of the slow pathway; allwere refractory to. or intolerant of, antiarrhyth-mic drugs (mean 2 ± I). There were 96 men and122 women (mean age 43 ± 15 years, range 14to 82). Fourteen patients had other structural heartdiseases (6 hypertension. 4 coronary artery disease,and 4 mitral valve prolapse).

Electrophysiologic Study

As described previously, each patient gave in-formed consent for the electrophysiologic studyand ablation." - Four niultipolar. closely spaced (2-5-2 mm interelectrode space) electrode catheters(Mansfield Scientific, Mansfield. MA. USA) wereinserted percutaneously into the right and leftfemora! veins and positioned in the high rightatrium, His-bundle area, posterior aspect of thetricuspid annulus, and right ventricle. They wereused for recording and for programmed atrial andventricular stimulation. One orthogonal electrodecatheter (12 poles, distal 3 cm free of electrode)(Mansfield Scientific) was inserted percutaneouslyinto the right internal jugular vein and positionedin the coronai^ sinus to record the electrical ac-tivity around the posteroseptal and proximal coro-nary sinus area. Intracardiac electrograms werefiltered at 30 to 500 Hz and simultaneously dis-played with surface ECG leads I, II, and V, on amultichannel oscilloscope (Electronics for Medi-cine VR-13. PPG Biomedical Systems. Cardio-vascular Div., Pleasantville, NY, USA). Electricalstimulation was performed with a programmablestimulator (DTU-2U). 215. Bloom Asswiates Ltd.,Nazareth. PA, USA) that delivered rectangularpulses of twice diastolic threshold and a pulse du-ration of 2 msec. All stimuli were deliveredthrough an isolation unit, and the electrical equip-ment was grounded.

Baseline electrophysiologic study protocols forAV ncxial reentrant tachyciirdia were described pre-viously, including determination of the eflective re-fractory periods of the right atrium. AV n(xle (fastand slow pathways in the anlerograde and retro-grade directions), and right ventricle, and inductionof AV nodal reentriuit tachycardia.*^ The diagnosisof AV nodal reentrant tachycardia was made byclassic criteria and by excluding the intra-atrial reen-trant tachycardia or the tachycardia incoiporatingmid-septal or paraseptal accessory pathway.^-'"

Mapping and Ablation

A putative slow pathway jx>tential as describedby Jackman et al.' was used to guide the ablationsite. If the anterograde slow pathway potential couldnot be ohtained, radiofrequency energy was de-livered to the mid-septal and posteroseptal aspectsof the tricuspid annulus. Three parts (superior, me-dial, and posterior) were divided from the His-bun-dle area to the (loor of the coronary sinus orifice.The catheter was initially positioned in the rightanterior oblique projection, along the tricuspid an-nulus anterior to the coronary sinus orifice and cau-dal to the fxjsition of the catheter recording His-bundle activation. At the posterior area, the bipo-lar electrogram from the distal electrode pairrecorded a ventricular deflection that was largerthan the atrial deflection, and the proximal elec-trode pair recorded atrial and ventricular deflec-tion of approximately equal amplitude. The abla-tion catheter was maintained in a stable positionwith gentle clockwise rotation, and the positionwas based on fluoroscopic imaging of the anatomyof Koch's triangle and the electrogram amplitudeof the atrial and ventricular deflections recordedby the ablation catheter. If delivery of energy tothis region was not successful in ablating slowpathway conduction, the catheter was repositionedcaudal to the coronary sinus orifice along the tri-cuspid annulus in a continued attempt to ahlate theslow pathway. If selective slow pathway ablationwas not achieved in this region, the catheter wasrepositioned more cephalic to the coron;iry sinusorifice along the tricuspid annulus in a continuedattempt. As described previously, a multipolar,closely spaced (2 mm), deflectable, large-tip (4-mm) electrode catheter (Mansfield Scientific) wasused for mapping and ablation; radiofrequency en-ergy (Radionlcs-3C, Burlington, MA. USA) wasdelivered at a power setting of 30 to 40 W, dura-tion 20 to 60 seconds, and was terminated imme-diately in the event of inip)edance rise, dislocation

Ueng, ft id. Koch's Triangle in AVNRT 1019

of the catheter, or prolongation of the PR interval.''After each application of radio frequency energy,induction of tachycardia was attempted, and an-terograde and retrograde conduction were assessedimmediately. Endpoints of the procedures wereelimination of anterograde and/or retrograde slowpathways with noninducibility of AV nodal reen-trant tachycardia. Ablation failure was defined asinduction of two or more beats of AV nodal reen-trant echoes or tachycardia under isoproterenoland/or atmpine challenge. Presence of residual slowpathway conduction with induction of a single AVnodal reentrant echo beat was not regarded as ab-lation failure. The details of postablation follow-up studies have been described previously.' -'-'*

Coronary Arteriography for Coronary SinusVenogram

As described previously, coronary arteriographyof the left coronaiy artery was performed in everypatient before electrophysiologic study to locatethe coroniiry sinus orifice.'' A 7-Frcnch introduc-ing sheath was first inserted into the rightfemoral artery by the Seldinger technique. A 7-French Judkins catheter for the left coronary arterywas then inserted and advanced through the sheathto the aortic arch into the ascending aorta undercontinuous pressure monitoring and fluoroscopicimaging. The left coronary ostium was cannulated,and 8 to 10 mL of contrast media was injected intothe left coronary artery. Special attention was paidto the venous phase of the coronary arteriography(about 5 to 10 sec after contrast injection), whichclearly delineated the coronary sinus orifice.

Definition of the Measured Anatomical Distance

At the apex of Koch's triangle, the AV nodepenetrates the central fibrous body to become theHis bundle. In the right anterior oblique projec-tion, the ptisterior and miterior landmiuks of Ktx:h'striangle iire delineated by the coronary sinus andHis-bundle catheters, respectively. The His-bundlecatheter was used as reference catheter with stan-dard interelectrode distance. Therefore, we usedthe distance between the proximal His bundle andcoronary sinus orifice (identified by contrast in-jection) (DHj _t>,) ^s a measurement of the dimen-sion of Koch's triangle. D ,-,,! is defined as thedistiince between the catheter electrode that recordedthe proximal His-bundle potential (half way be-tween electrodes 3 and 4; atrial and ventricularelectrograms the same size) and the floor of the

coronary sinus orifice identified by coronary sinusvenogram in the 30" right anterior oblique pro-jection during the end-diastolic cardiac cycle andend-expiratory phase. DHi ^ is defined as the dis-tance from the proximal His-bundle recording siteto the successful ablation site.

Statistical Analysis

All data are presented as mean ± 1 SD. The re-lations between age. body height, body weight,body surtace area, body mass index, and the mea-sured distance (DHJSOS' C)Hi*-Ab) were detennined bylinear regression analysis. Comparisons of thesevariables were performed using A-test. P < 0.05was considered statistically significant.

Results

Physical Characteristics

The men were taller (166 ± 7 vs 156 ± 6 cm,P < 0.001), heavier (67 ± 10 vs 57 ± 9 kg. P <0.001), and had larger body surface area (1.65 ±0.14 vs 1.48 ± 0.12 m^ P < 0.001) than women.The dimensions of Koch's triangle in patients withAV nfxlal reentrant tachycardia varied widely (Fig.I). The D^^,^_^^ and Dn,,., t, in all patients were 25.9± 7.9 mm (range 9 to 46) and 13.4 ± 3.8 mm (range6 to 28), respectively. These values (Dni,_os ^ "dDnis-Ab) were similar between the men (27.2 ± 6.4and 14.1 ± 4.0 mm. respectively) and women (24.9± 7.0 and 13.2 ± 3.5 mm. respectively).

Relation Between the Measured Distance andPhysical Characteristics (Table I)

DHis-os negatively correlated with age (r = -0.41.P < O.Oa)l) and body mass index (r = -O.is! P= 0.004); DHI.OS decreased progressively with in-crease of age or body mass index (Fig. 2). How-ever, it was not related to btxly length (r = 0.12,P = 0.20), body weight (r = -0.09. P = 0.08). orbody surface area (r = -0.07, P = 0.35). Dnj Ab wasnot related to age (r = -0.15, P = 0.21). b(xly massindex (r = -0.12. P = 0.52). body length (r = 0.18,P = 0.33), body weight (r = -0.09, P = 0.23), orbody surface area (r = -0.09, P = 0.11).

Relation Between Successful Ablation Site andDimension of Koch's Triangle

One hundred thirty-six patients had successfulablation al the posterior location and 82 patients

1020 Journal of Cardiovascular Electrophysiolu|>y Vol. 7. No. 11, November 1996

Figure 1. Patient with larger dimension of Koch's triangle (A) versus patient with smaller dimension ofKoch'.s triangle (B).

had successful ablation sites at the medial locations.The patients with successful ablation sites at themedial locations were younger (46 ± 16 vs 55 ±17 years, P < 0.05). The baseline electrophysio-logic data obtained from the patients with successfulablation sites in the posterior and medial areas didnot differ significantly {Table 2). Among the pa-tients with successful ablation sites in the medialarea, D^^^ was longer (27.2 ± 6.6 vs 24.6 ± 8.4mm, P < 0.005), Dij,,.^^ was similar (12.9 ± 3.1 vs13.9 ± 4.0, P > 0.05). and DHi,.^|/Dn,^^ was smaller(0.48 ± 0.04 vs 0.74 ± 0.11, P < 0.05). Further-more, the patients with successful ablation sites in

the medial location needed more radiofrequencypulse numbers than those with successful sites inthe posterior location (6 ± 4 vs 4 ± 3, P < 0.05).

Acute Results and Complications of RadiofrequencyAhlation

Possible slow pathway potentials were recordedto guide the ablation site in 85 (38.9%) of 218 pa-tients. Successful slow pathway ablation or mod-ification was achieved in a total of 218 patients(100%) during a single procedure. None of the pa-tients developed inadvertent complete AV

Veng. et al. Koch's Triangle in AVNRT 1021

Ijllik Ah

00

Le

r

.12

.18

TABLE 1

Correlation Between the Measured Anatomical Distance and Physical Characteristics

nf^lh

P

0.200.33

Weight

r P

-0 .09 0.08-0 .09 0.23

BSA BMl

r P r P r

- 0,07 {).?,5 - 0 . 1 8 0.004 - 0 . 4 \-O.(W 0,11 -0 .12 0.52 -0 .15

A Be

P

0.2!

BMl = body mass index; BSA = hody surface area.

Discussion

Major Findings

This study demonstrated that the distance be-tween the proximal His bundle and coronaiy sinusorifice decreased progressively with age, whereasthe distance between the proximal His bundle andsuccessful ablation site did not change with age.There was a remmkably constant distance from theproximal His-bundle recording site to the site ofsuccessful slow pathway ablation in patients withAV nodal reentrant tachycardia despite marked

o

I"Q

= -0.41p< 0.0001

20 JO 40 50 60 TO SO W

Age (years)

Ea, »9I «Q

U

t

° t ' ''° °° J° 1 , ' '

r = -0.18p = 0.004

•

B Body Mass Index (kg/m )

Figure 2. (Ai Plot correlating the distance between theproximal His bundle and the coronary sinus orifice f £>«/, ,jyidentified by contrast injection) and age. <B) Plot correlat-ing the distance between the proximal His bundle and coro-nary sinus orifice (D^i,.Q^ identified by contrast injection)and body mass index (kg/m-).

variability in the dimensions of Koch's triangle.This study also showed that most of the success-ful ablation sites were in the posterior position;those patients with successful ablation sites in themedial area were younger and had a longer dis-tance between the proximal His bundle and coro-nary sinus orifice. This study also supports theview that changes of dimension of Koch's trian-gle do not correlate with changes in slow AV ntxJalpathway position.

Prior Studies and Age-Related Changes of Koch'sTriangle

McGuire et al." measured the size of Koch's tri-angle during postmortem examination (31%) andduring surgical procedures for the cure of differ-ent supraventricular tachycardias. Although thelength of Koch's triangle was slightly shorter (17± 3 mm) than that found in the present sttidy. theydemonstrated that both the length and height ofKoch's trimigle correlated poorly with body length,body weight, and body surface area; however,the length of Koch's triangle, but not its height,correlated with heart weight.

To the best of our knowledge, this is the firststudy to show that the dimension of Koch's trian-gle correlates with age and body mass index. Al-though the measurements of the dimensions ofthe Koch's triangle based on catheter pcisitions andright anterior obhque view may not accurately rep-resent tnje anatomical dimensions, parts of the pres-ent study were similar to those the study byMcGuire's et al.*' There was a trend of older pa-tients with larger body mass index having a smallerdimension of Koch's triangle. Kitzman and Ed-wards'" studied the geometry of the age-relatedchanges in human hearts and found decrcasing base-to-apex dimension with age. This finding might ex-plain the negative correlation between age and di-mension of KcKh's triangle. Ensor et al." studiedthe longitudinal chest X-ray changes in normal menand demonstrated that the mean cardiothoracic ra-tio increased with age. This finding might explain

1022 Journal uf Cardiovascular Electrophysiology Vol. 7, No. II. November 1996

TABLK 2Comparisons of'ihe Anatomical and RIectropliysiologic

Characteristics Between ihe Patients with SuccessfulAblation Sites in the Medial and Posterior Positions

GroupMedial

(n = 82)Posterior(n = 136) P Values

Age (years)DHI»-OS (mm)

DHIK Ah ( m m )

DHK-At/Dnis-nsRF pulses (n)Fl:l (msec)Sl:l (msec)FERP(msec)SERP(msectVAI:1 (msec)VAKRP(msec)

4fi ± 1627.2 ± 6.6] 2.9 ± 3.10.48 ± 0.O4

6 ±4382 ± 79337 ± 67311 ±67277 ± 56354 ± 78291 ± 70

55 ± 1724.6 ± 8.413.9 ± 4.00.74 ± 0.11

4 ± 3389 ± 79343 ±35316 ± 63282 ± 42361 ± 58295 ± 56

< 0.05< 0.05

NS<0.05<0.05

NSNSNSNSNSNS

RF' = radiofrequeney; Fl : l = minimal atriat pacing cyclelength with 1:1 last AV node pathway conduction; S i : l =minimal atrial pacing cycle length with 1:1 slow AV nodepathway conduction; FERP = fast pathway effective re-fractory period; SERP = slow pathway effective refractoryperiod; VAIil = minimal ventricular pacing cycle lengthwith retrograde 1:1 conduction; VAERP = effective re-fractory period of retrograde VA conduction.

the positive correlation between age and the dis-tance from the middle line of vertebra to theproximal His bundle or coronary sinus ostium.

Previous studies shou-ed that most of the suc-cessful ablation sites were in the posteroseptal area(pt)steHor area).'^ and this study also had the samefinding. This study showed that the patients withsuccessful ablation sites in the medial area wereyounger, had longer length of Koch's triangle, andneeded more radiofreciuency pulses: however, thepatients with successful ablation sites in the pos-terior area were older, had smaller Koch's trian-gle, and needed less radiofrequency pulses. Itwas not cleiu- whether the changes of transitionalcells would occur with age; thus, younger patientswith longer length of Koch's triangle had the slowpathways located in the higher position (medialarea), and older patients with smaller length ofKtKh's triangle had the slow pathways located inthe lower position (posterior area).

Clinical Implication

These measured anatomical distances were use-ful for ablation of accessory pathways located inthe septal areas and ablation of slow pathways inpatients with AV nodal reentrant tachycardia.Previous studies demonstrated that the AV nodelength was < 7 mm'- and that the diameter ofthe lesion produced by radiofrequency energy de-

livered through an ablation electrode with a 4-mmlength was approximately 5 mm." Thus, deliveryof radiofrequency energy to the right posterosep-tal accessory pathways or slow AV nodal pathwaysnear the coronary sinus orifice was unlikely to dam-age the AV node directly, even in patients withsmaller Koch's triiuigle. However, delivery of ra-diofrequency energy to the right mid-septal ac-cessory pathways or slow AV nodal pathways inthe mid-septal iu ea must he done cautit>usly. Thisstudy demonstrated thai no matter what the di-mension ot the Koch's triangle, the distance fromthe successful ablation site to the proximal His-bundle recording site did not significantly change;therefore, patients with large triangles requiredmore ablation pulses using a method of progres-sively moving the ablation catheter in a caudal tocephalic and posterior to medial direction. Slowpathways were related closely to the posterior bor-der of the AV node; thus, large triangles requiredablation in the media! region rather than the pos-terior region. Therefore, we can use the direct me-dial approach in patients with large Koch's trian-gles to reduce the number of ablation pulses.

Limitations of the Study

Koch's triangle is a three-dimensional structure,and the two-dimensional measurements of Koch'striangle based on catheter positions and right an-terior oblique view in this study may not accu-rately represent true anatomical dimensions. Mea-surements of the dimensions of Koch's trianglein this study were made during end-diastolic iindend-expiratory phases, and these values may changesomewhat during different cardiac and respira-tory cycles.

References

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2. Jazayed MR. Mempe SL. Sra JS, et al; Selective trans-catheter ablation ol' the last and slow pathways usingradiofrequency energy in patients with atrioventricularnodal reentrant tachycardia. Circulation 1992:85:1318-1328.

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4. Kay GN, Epstein AE, Daiiey SM. et al: Selective ra-diofrequency ablation of the slow pathway for the

Ueng, et al. Koch's Triangle in AVNRT 1023

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9. Chiang CE, Chen SA, Yang CR. et al: Major coro-nary sinus abnormalities: Identification of occurrenceand significance In radiofrequency ablation ofsupraventricular tachycardia. Am Heart J 1994; 127:1279-1289.

10. Kitzman DW, Edwards WD: Age-related changes inthe anatomy of the normal human heart. J Gerontoll990;45:33-39.

11 . Ensor RE. Fleg JL. Kim YC. et al: Longitudinal chest X-ray changes in normal men. J Gerontol 1983;38:307-3l4.

12. Widran J, Lev M: The dissection of the atrioventricularnode, bundle and bundle branches in the human heart.Circulation l951;4:863-867.

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