Modified limb lead ECG system effects on electrocardiographic wave amplitudes and frontal plane axis in sinus rhythm subjects

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1 46 Originl Investigtion lim led ECG system effects on electrocrdiogrphic wve mplitudes nd frontl plne xis in sinus rhythm sujects Sivrmn Jyrmn, Venktesn Sngreddi 1, R. Periysmy 2, Justin Joseph 2, Rvi Mrimuthu Shnmugm 1 Deprtment of Biomedicl Engineering, Vel Tech Multi Tech; Chenni-Indi 1 Deprtment of Crdiology, Mdrs Medicl College, Rjiv Gndhi Government Generl Hospitl; Chenni-Indi 2 Deprtment of Biomedicl Engineering, Ntionl Institute of Technology; Ripur-Indi ABSTRACT Ojective: Lim Led (MLL) ECG system my e used during rest or exercise ECG, or tril ctivity enhncement. Becuse of modifiction in the lim electrode plcement, chnges re likely to hppen in ECG wve mplitudes nd frontl plne xis, which my lter the clinicl limits of normlity nd ECG dignostic criteri. The present study investigted the effects of the modified lim electrode position on the electrocrdiogrphic wveforms, ST segment mplitudes (ST ) nd frontl plne xis. Methods: The oservtionl study included sixty sinus rhythm sujects of men ge 38.85±8.76 (SD) in the rnge 25 to 58 yers. In ddition to 12-led ECG, MLL ECG ws recorded with, the RA electrode plced in the 3 rd right intercostl spce to the right of the prsternl line, the LA electrode plced in the 5 th right intercostl spce to the right of the mid-clviculr line nd the LL electrode plced in the 5 th right intercostl spce on the mid-clviculr line. Results: The modifiction produced profound chnges in ECG wve mplitudes nd ST mplitudes in frontl plne leds. The QRS nd T wve xis shifted on the verge y 17 o nd 41 o, respectively, with considerle individul vrition, which ltered the dignostic criteri. Conclusion: The ECG mplitudes nd ST chnges produced y the MLL system showed tht ll remins within the clinicl limits, except the R wve mplitude in the modified led I. It is evident tht the MLL system produced devitions in frontl plne QRS xis which ltered the dignostic interprettion. (Antol J Crdiol 217; 17: 46-54) Keywords: electrocrdiogrm, modified lim led, stndrd 12-led, ST, QRS xis Introduction The stndrd positioning of the lim led electrodes for electrocrdiogrm ws first devised y Willem Einthoven (1). Consequently the study nd stndrdiztion on the precordil leds for electrocrdiogrm were performed y Brnes et l. (2). Motion rtifct is mjor concern on the lim led electrodes, s it hs gret influence on the ECG wveform mplitudes (3). During exercise stress testing, motion of the lims cn disrupt the ECG recordings nd in conditions where lims ecome cliniclly inccessile, the modified lim electrode position on the torso ddresses the ove prolem (4). Mson et l. (5) proposed lterntive lim electrodes for the use in exercise stress testing. A vriety of modified lim electrode configurtions plced on the torso of helthy sujects is discussed (6 9). The modified lim electrode plced on the torso hd n effect on the wve mplitudes in the frontl plne ECG nd flsepositive ECG chnges hve een reported previously (1 15). Significnt R, S, nd T wve mplitude chnges ecuse of modified lim electrode plcement hve een reported previously (16 18). It hs een reported tht with the modified lim electrode plcement, no significnt chnges were oserved in the ECG wveform in the trnsverse plne, s the precordil leds re unchnged (19). In ddition to the modified lim electrode plcement, which ffects the wveform mplitudes nd frontl plne xis, severl other lterntive led systems, plced on the humn torso exist for recording nd studying the electricl ctivity of the tri (2). The uthors of this study recently proposed Lim Led (MLL) system for unmsking the tril repolriztion (T wve) in sinus rhythm sujects nd in AV lock ptients (21 23). Further, in their susequent study, they reported on the norml limits of the proposed MLL system nd documented the chnges hppened in P wve mplitudes nd frontl plne P wve xis Address for correspondence: Sivrmn Jyrmn, M.E., Ph.D., Deprtment of Biomedicl Engineering Vel Tech Multi Tech Engineering College, Chenni Indi Phone: E-mil: mountshiv@gmil.com Accepted Dte: Aville Online Dte: Copyright 217 y Turkish Society of Crdiology - Aville online t DOI: /AntolJCrdiol

2 Antol J Crdiol 217; 17: lim led ECG 47 (24). In tht study it ws found tht P wve mplitude incresed in ll the modified leds compred with tht in the stndrd leds, nd ccording to the results of tht study, it ws found tht the MLL system ws optiml in studying the electricl ctivity of the tril ECG components. In this study, the purpose of the investigtion ws to exmine the mgnitude of the ECG wve mplitudes nd ST segment mplitudes (ST) differences etween the stndrd lim led (SLL) nd the MLL ECG system. In ddition, it ws lso exmined whether the modifiction led to ny devitions in the frontl plne xis eyond the clinicl limits of normlity. Methods Study design This ws n oservtionl study which includes 6 mle sujects in sinus rhythm of men ge 38.85±8.76 (SD) in the rnge of 25 to 58 yers with norml ody composition. All volunteers were recruited into the study from the outptient deprtment of the Rjiv Gndhi Government Generl Hospitl, Chenni nd ll were mediclly exmined to exclude ny form of crdiovsculr disese. Non-hypertensive sujects were included in the study. Smokers nd ptients with congestive hert filure, vlvulr disese, tril firilltion, nd other crdiopulmonry diseses tht my lter the ECG morphology were excluded from this study, which ws pproved y the Institutionl Ethics Committee. Before dt recording, ll sujects gve informed consent to their prticiption in this study. lim electrode plcement The modified lim electrode plcement (21, 22) of the MLL system is riefly descried s follows (Fig. 1). The right rm electrode is plced on the suject s third right intercostl spce, slightly to the left of the mid-clviculr line. The left rm electrode is plced in the 5 th right intercostl spce, slightly to the right of the mid-clviculr line, nd the left leg electrode is plced in the 5 th right intercostl spce, on the mid-clviculr line. The right leg electrode is plced on the suject s right nkle. The polrity of the right rm electrode is negtive, nd the polrity of the left rm nd left leg electrode is positive. The usul terminology pplies-e.g., the potentil difference etween the right rm electrode (RA) nd left rm electrode (LA) is still denoted s led I, etc. The stndrd precordil electrode positions V1 V6 re unchnged in this study during the MLL recordings, ut they hve no role to ply in this study. ECG cquisition A digitl ECG recorder (EDAN SE-11 PC ECG system, EDAN Instruments, Inc., Chin) operting t smples per second with frequency response of.5 Hz to 1 Hz ws used to cquire ECG dt. ECGs could e printed t vrile gin from 2.5 mm/mv to mm/mv nd vrile pper speed of 5 mm/s to 2 mm/s. Figure 1. () Plcement of modified lim electrodes on the torso. The precordil leds V 1 _V 6 re unchnged. () Lim Led system. All ECGs were recorded in the supine position using surfce Ag AgCl electrodes. All the ECGs were recorded, first using the stndrd 12-led electrode positions nd susequently y the MLL system y repositioning the right rm, left rm nd left leg electrodes s indicted in Figure 1. All the ECGs were recorded t stndrd ECG pper speed of 25 mm/s nd 1 mm/mv. Dt nlysis All the ECG dt were nlyzed utomticlly y n utomtic nlysis smrt ECG mesurement nd interprettion progrms of EDAN ECG mchine in offline. The ECG vlues such s frontl plne xis (P, QRS, nd T), mplitudes of ech wveform (R, S, nd T) nd ST were ll recorded nd stored for further nlysis. The ST is mesured from the J point to 8 ms fter the onset of the J point (J+8 ms) in this study. The ST devitions re nlyzed for ech 2 ms fter the onset of the J point to vlidte whether the MLL system hs ny effect on the ST segments. All the ECG dt were plotted digitlly nd nlyzed seprtely for comprison purpose. Sttisticl nlysis The dt presented re expressed s men±stndrd devition (SD), men±stndrd error (SE). The Student's t-test ws used to determine sttisticl significnce of ll mesurement differences. The Shpiro-Wilk W test ws used for testing the normlity nd ll the dt were normlly distriuted (p=.78 ). Liner nd curviliner regression nlysis ws performed on the dt for the men distriution of QRS nd T wve xis. Liner regression nlysis ws used on the dt etween the stndrd nd modified men QRS nd T wve xis chnges. All tests were two-sided nd vlue p<.5 ws considered sttisticlly significnt. The collected dt were sttisticlly evluted using Win STAT in Excel for Windows. Results The 12-led ECG recorded on mle sujects in sinus rhythm reveled no trce of crdic disorders nd ws reported s eing within norml limits. All ECG dt were normlly distriuted. The stndrd 12-led ECG nd MLL ECG (21, 22) recor-

3 48 lim led ECG Antol J Crdiol 217; 17: men QRS xis (degrees) Stndrd men QRS xis (degrees) 2 1 Figure 2. () Stndrd 12-led ECG of mle suject in sinus rhythm. The R wve hs mximum mplitude in ll the leds. () MLL ECG of the sme mle suject in sinus rhythm used in the stndrd 12 led ECG. The MLL ECG shows the presence of lrge P wve mplitudes nd reduced R wve mplitudes in the lim leds ded t stndrd ECG pper speed in supine position for helthy mle sujects is shown in Figure 2. It is noted tht very lrge mplitude chnges tke plce with the MLL system. The MLL ECG showed significnt R wve mplitude chnges (23). As the left rm electrode nd left leg electrode re eside ech other in the MLL system, the modified led III ECG is essentilly seen s flt trce in ll the recordings. But still, smll R wve mplitude ws noticele in the modified led III with no distinct P nd T wve. Since the mplitude, xis chnges of the P wve nd the importnce of the MLL system in detecting the tril ECG components hve een previously reported s seprte pper (24) this study emphsis on other wve mplitudes (R, S, nd T), ST nd devitions in frontl plne xis cused y the MLL system. Chnges in QRS nd T wve xis Compred with the stndrd 12-led ECG, MLL plcement resulted in the frontl plne xis shift in P, QRS, nd T wves. The xis mesurements were generlly more ffected y the chnges in the modified lim electrode plcement. The distriution of the QRS nd T wve xis chnges etween the stndrd nd the modified position is shown in Figure 3, 4. The difference in the frontl plne xis (QRS nd T) vlues etween the MLL ECG nd SLL ECG is shown in Tle 1. The frontl plne men QRS xis hd significnt chnges in the MLL system, with n verge xis shift of 17±91 o when the electrodes were moved from the lim to the torso of the sujects. The men difference etween the Δ xis (degrees) c Axis ngle (degrees) Stndrd men QRS wve xis (degrees) QRS xis Clinicl threshold exceeds Stndrd Clinicl threshold exceeds Figure 3. () Distriution of men QRS wve xis in stndrd nd modified position nd curviliner regression clculted from the xis vlues () Distriution of men QRS wve xis in stndrd position (x-xis) versus the chnge in the mesurement when the electrodes re moved to the torso nd liner regression clculted from the xis vlues (c) Men electricl xes of the QRS complex in stndrd nd modified position showing the thresholds for clinicl normlity modified nd stndrd led (M-S) of the QRS xis is found to e 61 o. There re considerle individul vritions in the degree of this shift. The lest squre cuic fit for the modified xis (αm) clculted from the stndrd xis (αs) from Figure 3 is given s αm=.4αs 3.1αs αs (1) The eqution of the liner regression line from Figure 3 is given s ΔQRS xis ( o )= x QRS (2) where QRS is the QRS wve xis.

4 Antol J Crdiol 217; 17: lim led ECG 49 Tle 1. Chnges in the frontl plne xis with the stndrd nd modified positions Electrocrdiogrphic xis in degrees for sinus rhythm sujects ECG Stndrd position (SLL) position (MLL) Difference Men SD Rnge Men SD Rnge M-S P* QRS xis to to <.5 T xis to to <.5 MLL - modified lim led; SD - stndrd devition; SLL - stndrd lim led; *Pired smple t-test men T wve xis (degrees) Δ xis (degrees) Stndrd men T wve xis (degrees) Stndrd men T wve xis (degrees) Figure 4. () Distriution of men T wve xis in stndrd nd modified position nd curviliner regression clculted from the xis vlues () Distriution of men T wve xis in stndrd position (X-xis) versus the chnge in the mesurement when the electrodes re moved to the torso nd liner regression clculted from the xis vlues The T wve xis mesurements were lso ffected likewise in the P nd QRS xis. The distriution of the T wve xis in the SLL nd MLL system is shown in Figure 4. The frontl plne men T wve xis hd n verge shift of 4±17 o in the MLL system, when the electrodes re moved from the lim to the torso of the sujects. The men difference etween the modified nd stndrd (M-S) of the T wve xis is found to e 13 o. The lest squre cuic fit for the modified xis (αm) clculted from the stndrd xis (αs) from Figure 4 is given s αm=.αs 3.36αs αs (3) The eqution of the liner regression line from Figure 4 is given s ΔT xis ( o )= x T (4) where T is the T wve xis. QRS xis devitions Surwicz et l. (25) defined the clinicl limits of men frontl plne xis of QRS normlity nd normlity (i.e., < > 3 o to +9 o ). The rnge of devitions in QRS xis in the MLL system ws 88 o to 176 o, wheres in the SLL system it ws 26 o to 96 o. Although the modifiction produced individul vritions in degree of the xis shift, the men frontl QRS xis of the MLL system ws 17 o s seen in Figure 3c. Out of totl 6 sinus rhythm sujects, the MLL system in sinus rhythm sujects produced norml QRS xis shift [ 3 o to +9 o, (n=6)], mrked left xis devition [ 45 o to 9 o, (n=41)], moderte right xis devition [9 o to 12 o, (n=1)] nd mrked right xis devition [12 o to 18 o, (n=12)]. No sinus rhythm sujects produced ny moderte left xis devition ( 3 o to 45 o ). It is cler evident tht the modified lim electrode plcement in the torso produced devitions in the frontl plne men QRS xis nd this my hve n effect on the clinicl specificity. Chnges in ECG mplitudes nd wveforms Consequent to the chnges in the frontl plne xis shift resulted y the modifiction in the position of the lim electrodes, it is noted tht very lrge mplitude differences tkes plce in the frontl plne leds. As with the xis chnges the lrgest voltge chnges re found when the electrodes re moved from the lim to the torso. As expected, no significnt chnges re seen in the ECG mplitudes of the trnsverse plne leds (V1 V6) s they re unchnged during the recording of the modified positioning of the lim electrodes. The MLL system produced significnt R wve mplitude chnges when compred with the other frontl plne leds nd produced flse ECG chnges in the modified led I of the R wve mplitude. The men R wve mplitude of modified led I is.17 mv, which is <.2 mv defined s the clinicl threshold of normlity (26). The plot of men±se of R wve mplitudes in MLL nd SLL recordings is shown in Figure 5. In frontl plne leds the R wve mplitude decresed in the modified leds I-VF. Similrly, the modified lim electrode plcement produced mplitude chnges in S nd T wves respectively s shown in Figures 5 c. The S wve mplitude decresed in ll the frontl plne leds of the MLL system. The T wve mplitude decresed in ll the modified leds except the modified led VL. The R, S,

5 lim led ECG Antol J Crdiol 217; 17: R wve mplitude (µv) Stndrd L1 L2 L3 VR VL VF Leds S wve mplitude (µv) Stndrd L1 L2 L3 VR VL VF Leds T wve mplitude (µv) Stndrd L1 L2 L3 VR VL VF Leds c Figure 5. Plot of men±se of R, S, nd T wve mplitudes of the frontl plne leds in the stndrd nd the modified electrode positions Tle 2. ECG wves with the stndrd nd modifiction of the lim electrode positions. Men vlues re listed for the difference (M-S) in which positive vlues indicte n increse in mplitude nd negtive vlues indicte decrese cused y modifiction. Percentge gins in men mplitudes re lso provided. Amplitudes re in microvolts. N/A=not pplicle Mesurement Leds Stndrd position position Stndrd (SLL) (MLL) position (% chnge) Men SD Men SD Men % I II R mplitude III VR VL VF I II S mplitude III VR N/A VL VF I II T mplitude III VR VL VF MLL - modified lim led; SD - stndrd devition; SLL - stndrd lim led; vlues re in microvolts nd T wve mplitude vlues of the MLL system re shown in Tle 2. Men vlues re listed for the difference etween the modified nd stndrd led (M-S) in which positive vlue indictes n increse nd negtive vlue indictes decrese cused y modifiction of the electrode positioning. Chnges in ST segment mplitudes (ST) level Consequent to the chnges in the ECG mplitudes, the modifiction of the lim electrode produced chnges in the ST in the frontl plne leds. The ST is mesured from the J point to 8 ms fter the onset of the J point (J+8 ms) in this study. The ST devitions re nlyzed for ech 2 ms fter the onset of the J point to vlidte whether the MLL system hs ny effect on the ST segments. In generl the ST segment elevtion greter thn µv is defined s the clinicl threshold level in the frontl plne. Compred with the SLL system, the MLL system hd n influence in the ST, s the vlues of ST reduced in ll the modified leds (I-VF) for (J+ ms) nd (J+8 ms) which re found to e well within the clinicl limits. Incresed vlues of ST in modified led VF for J+2 ms, J+4 ms, J+6 ms were found nd ll re within the norml clinicl limits. The plot of men±se of ST (J) wve mplitudes in MLL nd SLL recordings re shown in Figure 6. The ST segment mplitude etween the vlues of the modified nd stndrd position is shown in Tle 3 nd the men vlues re listed for the difference etween the modified nd stndrd led (M-S) in which positive vlue indictes n increse nd negtive vlue indictes decrese cused y the modifiction.

6 Antol J Crdiol 217; 17: lim led ECG 51 ST (J) mplitude (µv) ST (2) mplitude in µv ST (4) mplitude (µv) ST (6) mplitude (µv) ST (8) mplitude in µv Stndrd L1 L2 L3 VR VL VF Leds Stndrd L1 L2 L3 VR VL VF Leds Stndrd L1 L2 L3 VR VL VF Leds Stndrd L1 L2 L3 VR VL VF Leds Stndrd L1 L2 L3 VR VL VF Leds Figure 6. Plot of men±se of ST [J + ST (8)] of the frontl plne leds in the stndrd nd the modified electrode positions Temporl chnges in PR intervl, QRS complex, nd QT intervl As expected the MLL system hs no effect on the temporl spects of the ECG wveform s shown in Tle 4. Discussion In this present study, the uthors sought to investigte the chnges in ECG wve mplitudes nd devitions in the frontl plne xis for the MLL system which ws originlly designed to fcilitte the study of tril P nd T wves in helthy mle sujects nd with view to study the dynmics of T wve in ptients with AV lock. During this investigtion, the uthors found tht the MLL system plced on the torso of the sinus rhythm sujects produced profound chnges in the ECG wve mplitudes, ST nd devitions in the frontl plne xis. The wveform chnges re ssocited with modified lim electrode with more verticl, rightwrd, nd leftwrd shift of the QRS frontl plne xis. The devition in the frontl plne xis hd the R wve, S wve, nd T wve mplitude decrese in ll the frontl plne leds. As the lim electrodes re moved over the chest, the ECG wve mplitudes, ST nd devitions in the frontl plne xis chnges were seen predominntly. Ruthrju et l. (27) showed tht lim electrodes, plced over the chest, even produced chnges in the trnsverse plne leds tht re sttisticlly significnt ut this is not evident in this study. Shepprd et l. (19) studied tht the Tkum electrode modifiction did produce ECG wve mplitude nd frontl plne xis chnges, which re sttisticlly significnt ut not cliniclly significnt y compring with the guidelines of the clinicl thresholds for normlity (25, 26, 28). The present study is in greement with Shepprd et l. (19) with few exceptions, in the frontl plne QRS xis devitions nd R wve mplitude chnges which re cliniclly significnt nd ove the clinicl threshold for normlity. The ST segment is used s key indictor of myocrdil ischemi during exercise stress testing nd emergency monitoring. In this study, it ws found tht the MLL system did not lter the ST vlues in ny of the modified leds which were nlyzed. The ST devitions were nlyzed for ech 2 ms fter the onset of the J point to (J+8 ms) nd ll the vlues re found to e within the norml clinicl limits. In the present study, the devitions in frontl plne xis is investigted in 6 sinus rhythm sujects nd found tht only 6 sujects exhiited norml QRS xis shift. Mrked left xis devition were seen in 41 sujects, mrked right xis devition in 12 sujects, nd moderte right xis devition in 1 suject, which is in the rnge of clinicl threshold of normlity. This result is in contrst to ll the previous study done on the modifiction. In this study, the devitions in the QRS xis produced flse-positive ECG chnges in frontl plne xis, which would led to flse interprettion of hert diseses. In previous studies it hs een sserted tht vritions in ECGs otined with modified lim electrode do not ffect dig-

7 52 lim led ECG Antol J Crdiol 217; 17: Tle 3. ST with the stndrd nd modifiction of the lim electrode positions. Men vlues re listed for the difference (M-S) in which positive vlues indicte n increse in mplitude nd negtive vlues indicte decrese cused y modifiction. Percentge gins in men mplitudes re lso provided. Amplitudes re in microvolts Mesurement Leds Stndrd position position Stndrd (SLL) (MLL) position (% chnge) Men SD Men SD Men % I II ST(J) mplitude III VR VL VF I II ST (J+2) mplitude III VR VL VF I II ST (J+4) mplitude III VR VL VF I II ST (J+6) mplitude III VR VL VF I II ST (J+8) mplitude III VR VL VF MLL - modified lim led; SD - stndrd devition; SLL - stndrd lim led; vlues re in microvolts Tle 4. Modifiction produced no mesurle temporl chnges in the ECG wveform in ll frontl plnes ECG intervls Stndrd lim led (SLL) ECG lim led (MLL) ECG Men SD Rnge Men SD Rnge P* PR Intervl to to 177 >.5 QRS wve to to 16 >.5 QT Intervl to to 388 >.5 SD - stndrd devition; vlues re in miliseconds; *Pired smple t-test

8 Antol J Crdiol 217; 17: lim led ECG 53 nostic interprettion (4 6). This is not true in the present study, s the frontl plne QRS xis shift in 54 sinus rhythm sujects nd R wve mplitude chnges in modified Led I of ll the 6 sinus rhythm sujects would led to flse interprettion of hert disese nd it would develop hert disese of electrocrdiogrphic origin termed y Prinzmetl et l. (29). Such normlities my generte unnecessry investigtions. Study limittions The results of the present study re vlid only for resting, supine sinus rhythm mle sujects. No femle sujects were included in this study. We hve not yet studied the ptients with known nd unknown normlities to test whether the modifiction in the electrode plcement lters the clinicl sensitivity. Conclusion Finlly, we show tht the MLL system, used in this study, produces profound chnges in ECG wve mplitudes, ST, nd devitions in QRS nd T wve xis in the frontl plne leds. We hve quntified tht the chnges in ECG wve mplitudes, ST nd devitions in QRS nd T wve xis, produced y the MLL system shows tht mny remins within the clinicl limits with few exceptions. In this study, the modifiction does lter the clinicl specificity of the stndrd ECG to some extent in the frontl plne QRS xis nd R wve mplitude in modified led I thus producing flse-positive ECG chnges in sinus rhythm sujects. Acknowledgements: One of the uthors would like to thnk the fund from the DST-FIST, Govt of Indi, vide Ref.: SR/FST/College-189/213, Dted: 6 th August 214. Conflict of interest: None declred. Peer-review: Externlly peer-reviewed. Authorship contriutions: Concept S.J.; Design S.J.; Supervision V.S., R.P., R.M.S.; Fundings S.J., V.S., R.P.; Mterils S.J., V.S., J.J., R.M.S.; Dt collection &/or processing S.J., V.S., R.M.S., J.J.; Anlysis &/or interprettion S.J., R.M.S., J.J.; Literture serch S.J., V.S., R.P., J.J.; Writing S.J., V.S., J.J.; Criticl review S.J., V.S., R.P., R.M.S., J.J.; Other S.J. References 1. Einthoven W. The different forms of the humn electrocrdiogrm nd their significtion. Lncet 1912; 1: Brnes AR, Prdee HEB, White PD, Wilson FN, Wolferth CC. Stndrdiztion of precordil leds - Supplementry report. Am Hert J 1938; 15: Wester JG. Reducing motion rtifcts nd interference in iopotentil recording. IEEE Trns Biomed Eng 1984; 31: Dimond D, Griffith DH, Greenerg ML, Crleton RA. Torso mounted electrocrdiogrphic electrodes for routine clinicl electrocrdiogrphy. J Electrocrdiol 1979; 12: Mson RE, Likr I. A new system of multiple-led exercise electrocrdiogrphy. 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