- Email: [email protected]
The value of the aV limb leads and the V chest leads (V4R to V7) in routine clinical electrocardiography
THE
VALUE OF THE aV LIMB LEADS AND THE CLINICAL LEADS (V~R TO V,) IN ROUTINE ELECTROCARDIOGRAPHY
R. H. ROSENMAN,
M.D.,* E. SILBER, M.D.,** AND B. SHORR, M.D. CHICAGO.
V CHEST
L. N. KATZ, &I .I).,
I I,I..
I
N RECENT years the emphasis in the field of electrocardiography has been in the direction of greater accuracy and refinement in diagnosis by means of more extensive exploration of precordial potentials. This has led not only to an increase in the number of precordial lead positions employed, but also to the development of techniques designed to avoid the distortions inherent in the ordinary bipolar connections. The central terminal developed by Wilson and his associates’ is the nearest practical approach to the theoretical ideal of an indifferent electrode having a null potential. It has been demonstrated, however, that even this indifferent electrode does not remain at zero potential during the heart cycle.2 For this reason we have deplored the term “unipolar” lead with reference to Wilson’s central terminal and have preferred the designation V lead. Nevertheless, the V chest leads have been found to be more accurate than the CF, CR, or CL connections3 and should be employed routinely. The combined use of V limb and V chest leads has found wide application, and their clinical value is now firmly established.” Recently, our interest has centered around an evaluation of the leads which would prove to be most fruitful for routine electrocardiographic analysis. In large institutions it is undesirable and costly to employ a battery of leads without regard for the fact that many of these leads do not regularly yield sufficient information to justify their routine use. This analysis was not designed as a study of the statistical value of each of the electrocardiographic leads used here. Such a study would have necessitated many more records obtained seriatim from more patients than comprise this survey. The value of the aV limb leads in the interpretation of individual electrocardiograms has already been well established. Our purpose was to determine whether the accuracy of routine electrocardiographic diagnosis could be increased appreciably enough to warrant the routine use of leads other than I, II, III, and V2, V4, and V5 which we have been using. It was also believed important to determine whether the routine use of the additional precordial leads would obviate the routine use of the aV limb leads. As a corollary, it was important to determine which combination of leads, taken routinely, would satisfy the demands of accuracy and practicability. From the Cardiovascular Department. I\Iedical Research Institute, l\tichael Reese Hospital, Chicago. The department is supported in part by the Michael Reese Research E’ouudation. Received for publicat,ion May 23, 1950. *Sam Ehrlich Memorial Fellow. Xow in California. **Herbert G. Mayer Memorial FeIiow.
574
AMERICAN
HE.4
RT
JOURNAL
The electrocardiograms of 466 consecutive patients referred from the various outpatient departments of Mandel Clinic were the subject of this study. ‘I’IW majority of the patients were adults, varying in age from 20 to 85 >.ears. Ho\%.ever, many of the electrocardiograms exhibiting right heart strain were obtained from children with congenital heart disease, referred to the Heart Station fcr intracardiac catheterization and angiocardiographic studies. Aklditional instances of intraventricular block with and without myocardial infarction were excluded. Our experiences with the latter wilt be discussed in a separate communication. It is the practice of the Outpatient Clinic to obtain routine electrocardiograms of many patients, so that many of the electrocardiograms were obtained from patients without disease of the cardiovascular system. ‘I’herefore, the patients studied represented a random sampling without regard to the presence of organic heart disease. An additional forty-nine consecutive electrocardiograms were obtained as “emergencies” from hospitalized patients. In the latter group the clinical indication was usually the suspicion of recent myocardial infarction. These records were included in order to provide a representative group of patients with coronary’ artery disease in whom the value of the electrocardiogram may be great. Leads I, II, III, aVs, aVL, aVr, Vi to Vi, V, R, and VAs were recorded in each instance. The precordial leads were obtained by using the central terminal.’ The aV limb leads were recorded by the method of Goldberger,lo modified by the introduction of a 5,000 ohm resistance in every comrection of the indifferent electrode to minimize current flowing through the skin.” The six-lead electrocardiograms (1~~1s 1, II, III and VZ, V 4, V 5) were interpreted in a routine manner according to criteria previously set forth.” The fifteen-lead electrocardiograms were then interpreted independently and Criteria for normality, left heart strain, and right heart final diagnoses reached. strain were those that have been recently set forth bar Sokolow and associates.‘“~‘3~” The results were tabulated in a manner indicating whether the additional leads clarified and provided added information not obtained from the six leads. Many of the patients were fluoroscoped in the horizontal position, and the anatomic position of the heart on its anteroposterior axis was estimated, using the same nomenclature as that employed in describing the “electrical position.” A correlation of the “electrical” and anatomic positions was made in three groups of cases comprising 200 patients. RESULTS
The electrocardiograms obtained from a total of 51.5 patients were included in this analysis. The fifteen-lead electrocardiograms were placed in one of six categories enumerated later and were then further subdivided on the basis of whether the additional leads were essential or superfluous to the correct interpretation. Three groups of records were classified (Table I) with respect to the of the heart; this was omitted in the cases of right heart “electrical position” strain, of recent and of previous myocardial infarction where experience has shown
ROSENMAN
TABLE I.
ET
AL.
:
VALUE
OF
aV
LIMB
AND
V CHEST
LEADS
575
THE ELECTRICAL POSITION IN THREE GROUPS OF PATIENTS I
i
ELECTROCARDIOGRAPHIC DIAGNOSIS
I
"ELECTRICAL
POSITION-t
NO. CASES
GROUP*
H.
S.H.
IST.
S.V. -__-___
___Normal
1;
-__ --Nonspecific abnormalities
II
-___ Left heart strain
1 -__--
-__
--Totals
160 16, ___-__--120 17
I;’
-__
i,” _____ 425
20 2i
15 2
13 0
20 3
28 1
15
64 j
5:
.-
v.
48 6
41 3
36 3
27 1
8j 6
10 13
91
99
.-~
__----
113 i
*Group I = Casesin which the routine six-lead electrocardiogram II = Cases in which the routine six-lead electrocardiogram
Group
corroborated
failed
final
to corroborate
interpretation.
final
interpre-
tation. tH. = horizontal. S.H. = semihorizontal. Int. = intermediate. S.V. = semivertical. V. = vertical.
that determination of position may be difficult and inaccurate.* As anticipated, so far as position was concerned, the chief value of the additional leads employed was in the correct interpretation of left heart strain in “electrically” vertical and semivertical hearts. Two hundred of the patients in the same three groups were fluoroscoped. The anatomic position of the heart with respect to the anteroposterior axis was estimated, using the same nomenclature as that for describing the “electrical position” (Table II). The determination of the anatomic position was based on impression, since no quantitative analysis was undertaken. It was, however, TABLE
II.
CORRELATION
OF THE ELECTRICAL AND PATIENTS (INCLUDED
200
ANATOMIC IN TABLE
j
GROUP*
NO. CASES
OF THE
HEART
IN
~-__
1
ELECTROCARDlOGRAFHiC DIAGNOSIS
POSITION
I)
NO.CASES
WITH
CORRELATIONt
----
I-
EXACT
GOOD
POOR
-_---~___
21 1
Normal Nonspecific abnormalities Left heart strain -__ Totals *See
Table
I for explanation.
tSee text for explanation
“‘:
10 1
15 4
17 4
121
216
1
62
97
41
-___ 4 I 20 4 --__-____-__-
of nomenclature.
._ ^
ROSENMAN
ET
AL.
:
VALUE
OF
aV
LIMB
AND
V CHEST
LEADS
577
arrived at independently. The correlation between the “electrical” and anatomic A good correlation, positions was similar in sixty-two instances (31 per cent). one in which the “electrical” and anatomic axes were not more than one position apart (e.g., “electrically” horizontal and anatomically semihorizontal), was obtained in an additional ninety-seven cases (48.5 per cent). The correlation In the presence of was poor in the remaining forty-one cases (20.5 per cent). marked cardiac enlargement, the correlation of “electrical” and anatomic positions was least accurate, and therefore, unreliable. Disregarding the significant subjective element in the fluoroscopic estimation of the anatomic position, there was an identical or close correlation with the “electrical” position in 79.5 per cent of the 200 cases. Normal Electrocardiogram.-There were 176 normal electrocardiograms, of which sixteen (9.1 per cent) had been misjudged to be abnormal on the basis By means of the aV limb of the usual six-lead electrocardiogram (Table III). leads, deep S waves in Leads II and III were shown to be within normal limits in two cases. Fig. 1,A illustrates such a pattern, showing the origin of deep S In waves in Leads II and III to be due to a horizontal “electrical” position. fourteen instances it was acknowledged that findings regarded as abnormal on the basis of only three precordial leads were normal in view of multiple chest leads. In Lead Vz, a small R wave or a flattened or inverted T wave led to the mistaken judgment of presumed abnormality. Variations of this kind may occur in this lead when the right ventricle is rotated anteriorly due to clockwise rotation of the heart on its longitudinal axis. In these instances the multiple precordial leads revealed the latter basis for the changes observed. 'GABLE
III.
~SUMMARP
OF THE
T)ATA
OBTAINED
FROM
515
ELECTROCARDIOGRAMS
I NO.CASES
I FINAL INTERPRETATION BASED ON 15 LEADS
;
‘Totals
176 137
j I
160
112
1
25 28 37
I !
88 12 35 23
1 I
SIX-LEAD
ECG ~__
CORROBORATEDFINAL INTERPRETATION
Normal Nonspecific abnormalitp Left heart strain Right heart strain Recent myocardial infarction Chronic coronary insufficiency
I!i WHICH
TOTAL No. CASES
515
/ FAILED j FINAL
16 17 24 13 2 5
120
338
TOCORROBORATE INTERPRETATION
,
77
Nonspeci$c Abnormalities of the Electrocardiogram.-Nonspecific abnormalities were noted in 137 electrocardiograms. Low voltage, abnormal P waves, and cardiac arrhythmias were not included as criteria of abnormality for this analysis. There were seventeen (12.4 per cent) instances in which these abnormal QRS complexes or T waves were present only in one or more of the additional leads, the usual six-lead electrocardiogram being within normal limits (Table III). The abnormality was observed in Lead VI in one patient, in Va in two, in Vs in one, in aVI. in four, and in aVF in nine. Tn three instances of an abnormal
Idead a\.~, there were also abnormalities in Lead V, or a\‘[.. Fig. 1,R illustrates (jr:<> year later, a pattern abnormal S-T-T contours limited to l,eads I76 and Vi. of left heart strain appeared in all leatls. In addition, there were five abnormal six-lead records in which the abnorma!ities were more marked in the additional leads. They we,re noted in leads aV1, in three, aVF in one, and \‘,; in one r-ecord. Left Heart Strain in the ~lectrocurdiogram.-One hundred twelve electrocardiograms exhibited abnormalities of the QRS and S-T-T complexes indicative of left heart strain (Table I II). The additional leads permitted a correct interpretation in twenty-four cases (21.4 per cent), nineteen of which were in “electrically” vertical and semivertical hearts (Table I). Xn unequivocal heart strain pattern was observed in Lead a\’ F in fourteen patients; in eight it was the only lead showing the characteristic contour and was, therefore, essential to the diagnosis; in the six remaining cases the strain pattern seen in Lead aVF was also present in Vc and,‘or \:7. l,ead a\‘~, was the 01111.lead exhibiting left heart strain in one patient; in another record the pattern in aV[. was also seen in Leads 1’6 and 1’7. In seven instances V 6 and 1’7 were the onl!. leads showing definitive left heart strain. In only one record of the entire group was the strain pattern confined to Lead kr;. l;ig. l,C and D, illustrates left heart strain patterns in which diagnostic abnormalities appeared only in Leads \/‘6 and \:7 (Dj and aVF, \,‘,j, and 1’; (C). The appearance of the strain WIltOUrS only in Leads V 6 and VT is due to the clockwise rotation OIJ the long axis. In six other records in which the usual six-lead electrocardiogram revealed left heart strain, this pattern was, nevertheless, better seen in one or more of the additional leads (in Y6 and Vi in three, in aVF in one, and in aVI, in two cases). The value of the additional leads in this group ma\- be summarized as follows: When aV limb leads and multiple precordial leads were employed, the definitive heart strain patern was usualI>. observed in more than one of the additional leads. If the pattern of left heart strain in an “electrically” vertical heart had been recognized in the standard limb leads, t-he correct diagnoses could have been made in man)- of the cases in which the usual six-lead electrocardiogram llnder such circumstances, I&ends a1’1, and failed to establish the diagnosis. aVp would have been less essential. Leads V,; and V7 wtre more often the sole leads to reveal a heart strain pattern than were aVI, or a\‘v; nevertheless, the latter were of sufficient value in this regard to merit their use in routine electrocardiograph).. Lead Vs was, by far, the most important single added lead in this group of patients. Right Heart Strain in the Electrocardiogram.-There were twenty-five electrocardiograms exhibiting right heart strain (Table III). The additional leads were essential to the correct interpretation in thirteen cases (52 per cent). The usual six-lead records were interpreted as being normal in three of these cases and as abnormal in ten. The specific diagnosis of right heart strain in this group, however, necessitated the additional leads. Although the strain pattern was often noted in several of the additional leads in many of the sixteen cases, in seven of these Lead V1 was the only additional lead necessary to establish the diagnosis. Fig. 2,A illustrates the importance of Lead VI in the diagnosis
ROSENNAN ET AL,: VALVEOFaV LIMBANDV CHESTLE:ADS
579
580
.4MERICAN
HEART
JOURNAL
of right heart strain. Lead aVl< was essential to the correct interpretation in onI\. one electrocardiogram and Lead VaR or \T4R in five others. Fig. 2,B illustrates the diagnostic value of Lead Van or iT4K in the interpretation of early right heart strain in children. The latter records were all obtained from children under 10 J’ears of age. Recent Myocardial Infarction in the electrocardiogranz.---Keceut myocardial infarction was correctly interpreted in the usual six-lead electrocardiogram in thirty-three proved cases, although the infarct pattern was more distinctly revealed in Leads aVL and V 3 in two and in aVL alone in three patients (Table III). The electrocardiographic patterns indicated recent myocardial infarction involving the anterior wall in twenty-four records and the posterior wall in nine others. Recent myocardial infarction was suspected, but could not be diagnosed with certainty in another two patients; here the additional leads were diagnostic (aVF in one and aVI, in another). In another record in which the six leads were interpreted as exhibiting acute car pulmonale (pulmonary embolism), the typical pattern of posterior wall infarction was observed in Lead aVp. In an additional instance, posterior wall infarction was observed in Lead aVv, whereas the usual six-lead electrocardiogram was interpreted as exhibiting only left heart strain. Fig. 2,C illustrates the value of Lead aVF in the diagnosis of posterior wall infarction. Chronic Coronary Insufficiency in the Electrocardiogranl.---Twenty-eight electrocardiograms exhibited evidence of previous myocardial infarction and other criteria of chronic coronary insufficiency.” Of these, there were five instances (17.8 per ce’nt) in which the stigmata of previous infarction were observed on11 in the additional leads (Table III). Thus, the diagnostic pattern of posterior wall infarction was noted in Lead aVF alone in two cases, of lateral wall infarction only in Lead aVL in one case, and of anterior wall infarction only in Lead V 3 in two instances. Fig. 2,D presents a record in which Lead Va proved invaluable in the diagnosis of anterior wall infarction, in this instance having occurred several years previously. DISCUSSION
The additional leads were found essential for the correct interpretation of 77 (1.5 per cent) of the 515 electrocardiograms that were analyzed (Table IV). The aV limb leads were diagnostic in 6.8 per cent of all patients in the absence of Lead VT or in 6 per cent with the latter present. The additional precordial leads (V 4Ror V 3K, V1, V 3, and V,) were essential to correct diagnosis in 8.2 per cent. Lead Vr was essential in another 0.7 per cent. The calculated percentage usefulness of the aV limb leads in this study was based on the interpretation of the usual six-lead electrocardiograms according to the empirical criteria employed in this department.5 In recent years the effect of the “electrical” position of the heart on the standard limb lead pattern observed in various conditions has been emphasized.6 Interpretation of the usual six-lead records in terms of newer knowledge of the standard limb leads, particularly in conjunction with the precordial leads, which we had begun to practice, would have significantly decreased the diagnostic value of the aV limb leads. This was particularly apparent in the recognition of left heart strain in “electrically” vertical
ROSENMAN
ET AL. :
VALUE
av
OF
LIMB
AND
V CHEST
581
LEADS
One benefit of the extra leads has been to improve and semivertical positions. the interpretation derived from the usual six leads. Continuation of their employment should further enhance such utility. The normal range of the standard limb leads has been extended in recent years because of the aid offered by the aV limb leads. The latter have made possible the recognition that changes formerly postulated as abnormal in the limb leads were merely an expression of normal variations in “electrical” position. This was evidenced in several instances in this study. The use of multiple precordial leads, over and above the three we have been accustomed to use, has also extended the normal range of individual leads, as illustrated by thirteen cases in this study (Table IV). Significant rotation of the heart on its long axis can shift the “transition zone” of QRS complexes and T waves to the right or left of its usual position. Our experience indicates that absolute criteria involving amplitudes of R, S, and T waves in the precordial leads are of lesser importance than a normal progression of amplitude and direction in the complete precordial electrocardiogram from VAT to Vi. ‘I‘AHLE
IV.
‘I‘HE
OF CASES FINAL
NI.YHER
IK WHICH
FOR THE
EACH
CORRECT
ADDITIONAL
LEAD
WAS
ESSENTIAL
INTERPRETATIOK
d
I FINAL ELECTROCARDIOGRAPHIC INTERPRETATION
~--__ aVR
--__
I \‘G
IIL13CTROChRDIOGRAPHIC
aVL
avF
___-___
VI __-__
l-8
LEAD
i --
aVt
Normal
3
Nonspecific abnormalities Left heart strain Right heart strain
4 1
Recent myocardial
infarction Chronic coronary sufficiency ‘I’otals
1;
2
1
2
129j 7
j
in12
! I
1
i
6
2 25
s
4
--3
to either Lead V~R 01 Vlpr which were alike in the five cases. tThese eases required examination of multiple aV or of multiple precordial leads for correct interpretation of normality. $12, if Lead VT is excluded: if Vi is included, then Vi is essential in five cases of left heart strain and aVF necessary in only eight cases. $If aV limb leads are excluded; VS is essential in only seven cases if aV limb leads are included. *Refers
As expected, nonspecific abnormalities were occasionally noted only in one or more of the additional leads (Table IV). The findings in patients exhibiting heart strain were of greater interest. One-half of the records presenting right heart strain were correctly interpreted only with the aid of the additional leads, particularly Leads V1, VOR, and VJR. However, Lead V3R or V4n was essential only in children, and they were found to be closely similar to each other in all cases. In each of the electrocardiograms obtained from adults which required additional leads for correct interpretation, Lead VI was sufficient for t,he diagnosis. Instances of advanced right heart strain were readily observed in the ordinary chest Leads VZ, VI, and V 5. The right-sided precordial leads were especially
valuable in cases of less marked heart strain, in which a diagnostic pattern was noted only in the leads in closest proximit?- to the right ventricle. This is not surprising in view of the apparent domination of the electrocardiogram by potenAlthough the pattern tials developed during the activation of the left ventricle. was often apparent in Lead ~VR, onl\- one case required this lead for diagnosis, the strain pattern also being present in Leads V, and ir 4n (and V any. In general, the most striking heart strain patterns were observed in I,eads VnR and V dR,’ although a pattern sufficient for diagnosis was usually concomitantly present in Lead VI. In retrospect, the correct diagnosis of right heart strain might have been arrived at in a greater numbei of the usual six-lead electrocardiograms had more attention been paid to the amplitude of the K wave and the time of onset of the “intrinsicoid” deflection in Lead I’?. The recognition of the classical abnormalities indicative of left heart strain in the standard limb leads heretofore has been based on the patterns usual11 present in “electricall>~” 1lorizontal and semihorizontal positions.” The pattern in the standard limb leads in “electricall~~” vertical and semivertical positions often closely resembles that previously considered indicative of right heart strain. A left ventricular strain pattern in the precordial leads usually makes possible a correct interpretation in such instances. However, even the trained observer often-requires the aid of the XV limb leads for their certain differentiation. I’he incidence of left heart strain in “electrically” vertical positions is attested to even in this small series of cases. It is further apparent that the pattern of left heart strain frequently may be observed only in the precordial leads recorded to the left of ITS, particularly in instances of significant clockwise rotation of the heart on its long axis (i.e., left ventricle displaced posteriorI\,). It is significant that records exhibiting left heart strain with a concordant pattern or a right axis shift in the standard limb leads are often electrocardiographicall~~ indicative of only left, and not combined, ventricular strain.:’ Our experience supports the fact that patterns diagnostic of previous (remote) myocardial infarction may be observed only in leads other than those The value of Lead aVL in the diagnosis of recent heretofore routinely taken. myocardial infarction involving the lateral wall of the left ventricle has alread) been demonstrated. 8 The value of Lead aVF in the diagnosis of recent posterior wall infarction has also been well established, particularly in its differentiation Lead aVF was found to be invaluable from the pattern of acute car pulmonale.9 in two of the thirty-three cases studied. Our study indicates that, of the additional leads employed, either VRR or VaR was unnecessary. Lead aVn was also not essential but was useful for 1,ead VT was not required in the presence routine clinical electrocardiography. of Leads aV1, and aVr. Lead Lr3 proved to be of less value than any of the added precordial leads, but proved of value in an occasional case of anterior wall inLead V,; was found to be invaluable, particularly in the diagnosis of farction. Leads V1 and V4R proved essential to the diagnosis of many left heart strain. Leads aVL and aVF were essential for the correct instances of right heart strain. interpretation of many specific and nonspecific electrocardiographic patterns (Table IV).
ROSENMAN
ET AL. :
VALUE
OF aV LIMB
AND
V CHEST
LEADS
583
The results of this study lead to the recommendation that the standard and aV limb leads and precordial leads VI, VZ, Vs, V 4, Vs, and Vg be employed for routine clinical electrocardiography. Lead V, is valuable in adults, especially when recent or old myocardial infarction is suspected clinically and when suspicious, but not diagnostic, changes are noted in Leads Vr and VZ. Lead ‘JaR should be recorded routinely in children. It is preferred to Lead V sa because of easier electro;le placement. The routine use of these leads will enhance greatly the clinical value of the electrocardiogram. We have established the practice of taking twelve leads in all patients in the Heart Station as a result of this study. In persons over 10 years, the leads are: I, II, III, aVR, aVL, aVr, Vr, VB, V 3, Vq, VS, and VC,. In those 10 years or younger, Va is omitted and VIn is used instead. SUMMARY
1. Five hundred and fifteen routine electrocardiograms were recorded and analyzed, employing the standard and aV limb leads and precordial leads Vr to VT, VsR, and VIs. Each electrocardiogram was interpreted independently using both the usual six-lead electrocardiogram (I, II, III, Vz, V 4, and V 5) and the fifteen leads mentioned previously. 2. Seventy-seven electrocardiograms (15 per cent) necessitated the presence of certain of the additional leads (aVL, aVr, V ?R, VI, Va, V,) for correct interpretation. 3. The aV limb leads proved essential to accurate interpretation in 6.8 per cent and certain of the additional precordial leads (V ds, VI, V 3, V,J in 8.2 per cent of the cases. 4. A good correlation between anatomic and “electrical” positions of the heart on its anteroposterior axis was found in 200 instances of normal electrocardiograms and those exhibiting nonspecific abnormalities or left heart strain. A poor correlation was encountered particularly in instances of marked enlargement of the heart. 5. The clinical value of the electrocardiogram has been shown to be significantly enhanced by takin g leads other than those heretofore routinely recorded at this institution (I, II, III, VP, V4, V,). 6. It is recommended that, for routine clinical electrocardiography in adults, the standard and the aV limb leads and the precordial leads Vr, Vs, Va, V 4, V5, and V 6 be employed. Lead VqR should also be recorded routinely in children under 10 years of age, and VI can be omitted below this age group. We are in the conduct advice.
greatly of this
indebted study
to the other and especially
members to Drs.
of the department for their invaluable help R. Langendorf and A. Pick for their critical
REFERENCES 1.
2. 3.
Wilson,
F. N., Johnston, F. D., Macleod, A. G., and Barker, P. S.: Electrocardiograms That Represent the Potential Variations of a Single Electrode, AM. HEART J. 9:447, 1933. Dolgin, M., Grau, S., and Katz, L. N.: Experimental Studies on the Validity of the Central Terminal of Wilson as an Indifferent Reference Point, AM. HEART J. 37:868, 1946. Dolgin, M.., Grau, S., and Katz, L. N.: A Comparison of Precordial Electrocardiograms Obtained with CR, CL, CF, and V Leads, AM. HEART J. 37:343, 1949.
584 4.
5. 6. 7. 8. 9.
10.
Il. 12. 13. 1-i.
AMERICAN
1Yilson,
HEART
JOURNAL
F. N., Johnston, F. I~., Kosenbaum, F. F., Erlanger, H., Kossmann, C. E., Hechr , H.. Cotrim. N.. de Oliviera. M.. Scarsi. R.. and Barker, P. S.: The Prerordial Electrocardiogram, Ah. HEART J.‘27:i9, 1944. Katz, L. N.: Electrocardiography., ed. 2, Philadelphia, 1946, Lea & Febiger. Myers, G. B., and Klein, H. A.: The Relation of Unipolar Limb Leads to I’recordial and Esophageal Leads, AM. HEART J. 35:727, 1948. Myers, G. B., Klein, H. A., and Storer, B. E.: The Electrocardiographic Diagnosis of Right Ventricular Hypertrophy, AM. HEART J. 35:1, 1948. Myers, G. B., Klein, H. .A., and Storer, B. E.: VII. Correlation of Electrocardiographic and Pathologic Findings in Lateral Infarction, AM. HEART I. 37:374, 1949. Myers, G. B., and-Oren, B. G.: The Use of the Augmented Unipolar Left Leg Lead in the Differentiation of the Normal From the Abnormal Q Wave in Standard Lead III, AM. HEART J. 29:708, 1945. Goldberger, E.: Simple, Indifferent, Electrocardiographic Electrode of Zero Potential and Technique of Obtaining Augmented, Unipolar, Extremity Leads, AM. HEART J. 23:483, 1942. Bryant, J. M., and Johnston, F. D.: Errors Encountered in the ITse of the Goldberger Central Terminal, J. Clin. Investigation 25:919, 1946. Sokolow, M., and Friedlander, R. D.: The Normal Unipolar Precordial and Limb Lead Electrocardiogram, AM. HEART J. 38:665, 1949. The Ventricular Complex in Left Ventricular Hypertrophy Sokolow, M., and Lyon, T. P.: as Obtained by Unipolar Precordial Limb Leads, AM. HEART J. 37:161, 1949. The Ventricular Complex in Right Ventricular HyperSokolow, M., and Lyon, T. P.: trophy as Obtained by ltnipolar Precordial Limb Leads, AM, HEART J. 38:2, 1949.
VALUE OF THE aV LIMB LEADS AND THE CLINICAL LEADS (V~R TO V,) IN ROUTINE ELECTROCARDIOGRAPHY
R. H. ROSENMAN,
M.D.,* E. SILBER, M.D.,** AND B. SHORR, M.D. CHICAGO.
V CHEST
L. N. KATZ, &I .I).,
I I,I..
I
N RECENT years the emphasis in the field of electrocardiography has been in the direction of greater accuracy and refinement in diagnosis by means of more extensive exploration of precordial potentials. This has led not only to an increase in the number of precordial lead positions employed, but also to the development of techniques designed to avoid the distortions inherent in the ordinary bipolar connections. The central terminal developed by Wilson and his associates’ is the nearest practical approach to the theoretical ideal of an indifferent electrode having a null potential. It has been demonstrated, however, that even this indifferent electrode does not remain at zero potential during the heart cycle.2 For this reason we have deplored the term “unipolar” lead with reference to Wilson’s central terminal and have preferred the designation V lead. Nevertheless, the V chest leads have been found to be more accurate than the CF, CR, or CL connections3 and should be employed routinely. The combined use of V limb and V chest leads has found wide application, and their clinical value is now firmly established.” Recently, our interest has centered around an evaluation of the leads which would prove to be most fruitful for routine electrocardiographic analysis. In large institutions it is undesirable and costly to employ a battery of leads without regard for the fact that many of these leads do not regularly yield sufficient information to justify their routine use. This analysis was not designed as a study of the statistical value of each of the electrocardiographic leads used here. Such a study would have necessitated many more records obtained seriatim from more patients than comprise this survey. The value of the aV limb leads in the interpretation of individual electrocardiograms has already been well established. Our purpose was to determine whether the accuracy of routine electrocardiographic diagnosis could be increased appreciably enough to warrant the routine use of leads other than I, II, III, and V2, V4, and V5 which we have been using. It was also believed important to determine whether the routine use of the additional precordial leads would obviate the routine use of the aV limb leads. As a corollary, it was important to determine which combination of leads, taken routinely, would satisfy the demands of accuracy and practicability. From the Cardiovascular Department. I\Iedical Research Institute, l\tichael Reese Hospital, Chicago. The department is supported in part by the Michael Reese Research E’ouudation. Received for publicat,ion May 23, 1950. *Sam Ehrlich Memorial Fellow. Xow in California. **Herbert G. Mayer Memorial FeIiow.
574
AMERICAN
HE.4
RT
JOURNAL
The electrocardiograms of 466 consecutive patients referred from the various outpatient departments of Mandel Clinic were the subject of this study. ‘I’IW majority of the patients were adults, varying in age from 20 to 85 >.ears. Ho\%.ever, many of the electrocardiograms exhibiting right heart strain were obtained from children with congenital heart disease, referred to the Heart Station fcr intracardiac catheterization and angiocardiographic studies. Aklditional instances of intraventricular block with and without myocardial infarction were excluded. Our experiences with the latter wilt be discussed in a separate communication. It is the practice of the Outpatient Clinic to obtain routine electrocardiograms of many patients, so that many of the electrocardiograms were obtained from patients without disease of the cardiovascular system. ‘I’herefore, the patients studied represented a random sampling without regard to the presence of organic heart disease. An additional forty-nine consecutive electrocardiograms were obtained as “emergencies” from hospitalized patients. In the latter group the clinical indication was usually the suspicion of recent myocardial infarction. These records were included in order to provide a representative group of patients with coronary’ artery disease in whom the value of the electrocardiogram may be great. Leads I, II, III, aVs, aVL, aVr, Vi to Vi, V, R, and VAs were recorded in each instance. The precordial leads were obtained by using the central terminal.’ The aV limb leads were recorded by the method of Goldberger,lo modified by the introduction of a 5,000 ohm resistance in every comrection of the indifferent electrode to minimize current flowing through the skin.” The six-lead electrocardiograms (1~~1s 1, II, III and VZ, V 4, V 5) were interpreted in a routine manner according to criteria previously set forth.” The fifteen-lead electrocardiograms were then interpreted independently and Criteria for normality, left heart strain, and right heart final diagnoses reached. strain were those that have been recently set forth bar Sokolow and associates.‘“~‘3~” The results were tabulated in a manner indicating whether the additional leads clarified and provided added information not obtained from the six leads. Many of the patients were fluoroscoped in the horizontal position, and the anatomic position of the heart on its anteroposterior axis was estimated, using the same nomenclature as that employed in describing the “electrical position.” A correlation of the “electrical” and anatomic positions was made in three groups of cases comprising 200 patients. RESULTS
The electrocardiograms obtained from a total of 51.5 patients were included in this analysis. The fifteen-lead electrocardiograms were placed in one of six categories enumerated later and were then further subdivided on the basis of whether the additional leads were essential or superfluous to the correct interpretation. Three groups of records were classified (Table I) with respect to the of the heart; this was omitted in the cases of right heart “electrical position” strain, of recent and of previous myocardial infarction where experience has shown
ROSENMAN
TABLE I.
ET
AL.
:
VALUE
OF
aV
LIMB
AND
V CHEST
LEADS
575
THE ELECTRICAL POSITION IN THREE GROUPS OF PATIENTS I
i
ELECTROCARDIOGRAPHIC DIAGNOSIS
I
"ELECTRICAL
POSITION-t
NO. CASES
GROUP*
H.
S.H.
IST.
S.V. -__-___
___Normal
1;
-__ --Nonspecific abnormalities
II
-___ Left heart strain
1 -__--
-__
--Totals
160 16, ___-__--120 17
I;’
-__
i,” _____ 425
20 2i
15 2
13 0
20 3
28 1
15
64 j
5:
.-
v.
48 6
41 3
36 3
27 1
8j 6
10 13
91
99
.-~
__----
113 i
*Group I = Casesin which the routine six-lead electrocardiogram II = Cases in which the routine six-lead electrocardiogram
Group
corroborated
failed
final
to corroborate
interpretation.
final
interpre-
tation. tH. = horizontal. S.H. = semihorizontal. Int. = intermediate. S.V. = semivertical. V. = vertical.
that determination of position may be difficult and inaccurate.* As anticipated, so far as position was concerned, the chief value of the additional leads employed was in the correct interpretation of left heart strain in “electrically” vertical and semivertical hearts. Two hundred of the patients in the same three groups were fluoroscoped. The anatomic position of the heart with respect to the anteroposterior axis was estimated, using the same nomenclature as that for describing the “electrical position” (Table II). The determination of the anatomic position was based on impression, since no quantitative analysis was undertaken. It was, however, TABLE
II.
CORRELATION
OF THE ELECTRICAL AND PATIENTS (INCLUDED
200
ANATOMIC IN TABLE
j
GROUP*
NO. CASES
OF THE
HEART
IN
~-__
1
ELECTROCARDlOGRAFHiC DIAGNOSIS
POSITION
I)
NO.CASES
WITH
CORRELATIONt
----
I-
EXACT
GOOD
POOR
-_---~___
21 1
Normal Nonspecific abnormalities Left heart strain -__ Totals *See
Table
I for explanation.
tSee text for explanation
“‘:
10 1
15 4
17 4
121
216
1
62
97
41
-___ 4 I 20 4 --__-____-__-
of nomenclature.
._ ^
ROSENMAN
ET
AL.
:
VALUE
OF
aV
LIMB
AND
V CHEST
LEADS
577
arrived at independently. The correlation between the “electrical” and anatomic A good correlation, positions was similar in sixty-two instances (31 per cent). one in which the “electrical” and anatomic axes were not more than one position apart (e.g., “electrically” horizontal and anatomically semihorizontal), was obtained in an additional ninety-seven cases (48.5 per cent). The correlation In the presence of was poor in the remaining forty-one cases (20.5 per cent). marked cardiac enlargement, the correlation of “electrical” and anatomic positions was least accurate, and therefore, unreliable. Disregarding the significant subjective element in the fluoroscopic estimation of the anatomic position, there was an identical or close correlation with the “electrical” position in 79.5 per cent of the 200 cases. Normal Electrocardiogram.-There were 176 normal electrocardiograms, of which sixteen (9.1 per cent) had been misjudged to be abnormal on the basis By means of the aV limb of the usual six-lead electrocardiogram (Table III). leads, deep S waves in Leads II and III were shown to be within normal limits in two cases. Fig. 1,A illustrates such a pattern, showing the origin of deep S In waves in Leads II and III to be due to a horizontal “electrical” position. fourteen instances it was acknowledged that findings regarded as abnormal on the basis of only three precordial leads were normal in view of multiple chest leads. In Lead Vz, a small R wave or a flattened or inverted T wave led to the mistaken judgment of presumed abnormality. Variations of this kind may occur in this lead when the right ventricle is rotated anteriorly due to clockwise rotation of the heart on its longitudinal axis. In these instances the multiple precordial leads revealed the latter basis for the changes observed. 'GABLE
III.
~SUMMARP
OF THE
T)ATA
OBTAINED
FROM
515
ELECTROCARDIOGRAMS
I NO.CASES
I FINAL INTERPRETATION BASED ON 15 LEADS
;
‘Totals
176 137
j I
160
112
1
25 28 37
I !
88 12 35 23
1 I
SIX-LEAD
ECG ~__
CORROBORATEDFINAL INTERPRETATION
Normal Nonspecific abnormalitp Left heart strain Right heart strain Recent myocardial infarction Chronic coronary insufficiency
I!i WHICH
TOTAL No. CASES
515
/ FAILED j FINAL
16 17 24 13 2 5
120
338
TOCORROBORATE INTERPRETATION
,
77
Nonspeci$c Abnormalities of the Electrocardiogram.-Nonspecific abnormalities were noted in 137 electrocardiograms. Low voltage, abnormal P waves, and cardiac arrhythmias were not included as criteria of abnormality for this analysis. There were seventeen (12.4 per cent) instances in which these abnormal QRS complexes or T waves were present only in one or more of the additional leads, the usual six-lead electrocardiogram being within normal limits (Table III). The abnormality was observed in Lead VI in one patient, in Va in two, in Vs in one, in aVI. in four, and in aVF in nine. Tn three instances of an abnormal
Idead a\.~, there were also abnormalities in Lead V, or a\‘[.. Fig. 1,R illustrates (jr:<> year later, a pattern abnormal S-T-T contours limited to l,eads I76 and Vi. of left heart strain appeared in all leatls. In addition, there were five abnormal six-lead records in which the abnorma!ities were more marked in the additional leads. They we,re noted in leads aV1, in three, aVF in one, and \‘,; in one r-ecord. Left Heart Strain in the ~lectrocurdiogram.-One hundred twelve electrocardiograms exhibited abnormalities of the QRS and S-T-T complexes indicative of left heart strain (Table I II). The additional leads permitted a correct interpretation in twenty-four cases (21.4 per cent), nineteen of which were in “electrically” vertical and semivertical hearts (Table I). Xn unequivocal heart strain pattern was observed in Lead a\’ F in fourteen patients; in eight it was the only lead showing the characteristic contour and was, therefore, essential to the diagnosis; in the six remaining cases the strain pattern seen in Lead aVF was also present in Vc and,‘or \:7. l,ead a\‘~, was the 01111.lead exhibiting left heart strain in one patient; in another record the pattern in aV[. was also seen in Leads 1’6 and 1’7. In seven instances V 6 and 1’7 were the onl!. leads showing definitive left heart strain. In only one record of the entire group was the strain pattern confined to Lead kr;. l;ig. l,C and D, illustrates left heart strain patterns in which diagnostic abnormalities appeared only in Leads \/‘6 and \:7 (Dj and aVF, \,‘,j, and 1’; (C). The appearance of the strain WIltOUrS only in Leads V 6 and VT is due to the clockwise rotation OIJ the long axis. In six other records in which the usual six-lead electrocardiogram revealed left heart strain, this pattern was, nevertheless, better seen in one or more of the additional leads (in Y6 and Vi in three, in aVF in one, and in aVI, in two cases). The value of the additional leads in this group ma\- be summarized as follows: When aV limb leads and multiple precordial leads were employed, the definitive heart strain patern was usualI>. observed in more than one of the additional leads. If the pattern of left heart strain in an “electrically” vertical heart had been recognized in the standard limb leads, t-he correct diagnoses could have been made in man)- of the cases in which the usual six-lead electrocardiogram llnder such circumstances, I&ends a1’1, and failed to establish the diagnosis. aVp would have been less essential. Leads V,; and V7 wtre more often the sole leads to reveal a heart strain pattern than were aVI, or a\‘v; nevertheless, the latter were of sufficient value in this regard to merit their use in routine electrocardiograph).. Lead Vs was, by far, the most important single added lead in this group of patients. Right Heart Strain in the Electrocardiogram.-There were twenty-five electrocardiograms exhibiting right heart strain (Table III). The additional leads were essential to the correct interpretation in thirteen cases (52 per cent). The usual six-lead records were interpreted as being normal in three of these cases and as abnormal in ten. The specific diagnosis of right heart strain in this group, however, necessitated the additional leads. Although the strain pattern was often noted in several of the additional leads in many of the sixteen cases, in seven of these Lead V1 was the only additional lead necessary to establish the diagnosis. Fig. 2,A illustrates the importance of Lead VI in the diagnosis
ROSENNAN ET AL,: VALVEOFaV LIMBANDV CHESTLE:ADS
579
580
.4MERICAN
HEART
JOURNAL
of right heart strain. Lead aVl< was essential to the correct interpretation in onI\. one electrocardiogram and Lead VaR or \T4R in five others. Fig. 2,B illustrates the diagnostic value of Lead Van or iT4K in the interpretation of early right heart strain in children. The latter records were all obtained from children under 10 J’ears of age. Recent Myocardial Infarction in the electrocardiogranz.---Keceut myocardial infarction was correctly interpreted in the usual six-lead electrocardiogram in thirty-three proved cases, although the infarct pattern was more distinctly revealed in Leads aVL and V 3 in two and in aVL alone in three patients (Table III). The electrocardiographic patterns indicated recent myocardial infarction involving the anterior wall in twenty-four records and the posterior wall in nine others. Recent myocardial infarction was suspected, but could not be diagnosed with certainty in another two patients; here the additional leads were diagnostic (aVF in one and aVI, in another). In another record in which the six leads were interpreted as exhibiting acute car pulmonale (pulmonary embolism), the typical pattern of posterior wall infarction was observed in Lead aVp. In an additional instance, posterior wall infarction was observed in Lead aVv, whereas the usual six-lead electrocardiogram was interpreted as exhibiting only left heart strain. Fig. 2,C illustrates the value of Lead aVF in the diagnosis of posterior wall infarction. Chronic Coronary Insufficiency in the Electrocardiogranl.---Twenty-eight electrocardiograms exhibited evidence of previous myocardial infarction and other criteria of chronic coronary insufficiency.” Of these, there were five instances (17.8 per ce’nt) in which the stigmata of previous infarction were observed on11 in the additional leads (Table III). Thus, the diagnostic pattern of posterior wall infarction was noted in Lead aVF alone in two cases, of lateral wall infarction only in Lead aVL in one case, and of anterior wall infarction only in Lead V 3 in two instances. Fig. 2,D presents a record in which Lead Va proved invaluable in the diagnosis of anterior wall infarction, in this instance having occurred several years previously. DISCUSSION
The additional leads were found essential for the correct interpretation of 77 (1.5 per cent) of the 515 electrocardiograms that were analyzed (Table IV). The aV limb leads were diagnostic in 6.8 per cent of all patients in the absence of Lead VT or in 6 per cent with the latter present. The additional precordial leads (V 4Ror V 3K, V1, V 3, and V,) were essential to correct diagnosis in 8.2 per cent. Lead Vr was essential in another 0.7 per cent. The calculated percentage usefulness of the aV limb leads in this study was based on the interpretation of the usual six-lead electrocardiograms according to the empirical criteria employed in this department.5 In recent years the effect of the “electrical” position of the heart on the standard limb lead pattern observed in various conditions has been emphasized.6 Interpretation of the usual six-lead records in terms of newer knowledge of the standard limb leads, particularly in conjunction with the precordial leads, which we had begun to practice, would have significantly decreased the diagnostic value of the aV limb leads. This was particularly apparent in the recognition of left heart strain in “electrically” vertical
ROSENMAN
ET AL. :
VALUE
av
OF
LIMB
AND
V CHEST
581
LEADS
One benefit of the extra leads has been to improve and semivertical positions. the interpretation derived from the usual six leads. Continuation of their employment should further enhance such utility. The normal range of the standard limb leads has been extended in recent years because of the aid offered by the aV limb leads. The latter have made possible the recognition that changes formerly postulated as abnormal in the limb leads were merely an expression of normal variations in “electrical” position. This was evidenced in several instances in this study. The use of multiple precordial leads, over and above the three we have been accustomed to use, has also extended the normal range of individual leads, as illustrated by thirteen cases in this study (Table IV). Significant rotation of the heart on its long axis can shift the “transition zone” of QRS complexes and T waves to the right or left of its usual position. Our experience indicates that absolute criteria involving amplitudes of R, S, and T waves in the precordial leads are of lesser importance than a normal progression of amplitude and direction in the complete precordial electrocardiogram from VAT to Vi. ‘I‘AHLE
IV.
‘I‘HE
OF CASES FINAL
NI.YHER
IK WHICH
FOR THE
EACH
CORRECT
ADDITIONAL
LEAD
WAS
ESSENTIAL
INTERPRETATIOK
d
I FINAL ELECTROCARDIOGRAPHIC INTERPRETATION
~--__ aVR
--__
I \‘G
IIL13CTROChRDIOGRAPHIC
aVL
avF
___-___
VI __-__
l-8
LEAD
i --
aVt
Normal
3
Nonspecific abnormalities Left heart strain Right heart strain
4 1
Recent myocardial
infarction Chronic coronary sufficiency ‘I’otals
1;
2
1
2
129j 7
j
in12
! I
1
i
6
2 25
s
4
--3
to either Lead V~R 01 Vlpr which were alike in the five cases. tThese eases required examination of multiple aV or of multiple precordial leads for correct interpretation of normality. $12, if Lead VT is excluded: if Vi is included, then Vi is essential in five cases of left heart strain and aVF necessary in only eight cases. $If aV limb leads are excluded; VS is essential in only seven cases if aV limb leads are included. *Refers
As expected, nonspecific abnormalities were occasionally noted only in one or more of the additional leads (Table IV). The findings in patients exhibiting heart strain were of greater interest. One-half of the records presenting right heart strain were correctly interpreted only with the aid of the additional leads, particularly Leads V1, VOR, and VJR. However, Lead V3R or V4n was essential only in children, and they were found to be closely similar to each other in all cases. In each of the electrocardiograms obtained from adults which required additional leads for correct interpretation, Lead VI was sufficient for t,he diagnosis. Instances of advanced right heart strain were readily observed in the ordinary chest Leads VZ, VI, and V 5. The right-sided precordial leads were especially
valuable in cases of less marked heart strain, in which a diagnostic pattern was noted only in the leads in closest proximit?- to the right ventricle. This is not surprising in view of the apparent domination of the electrocardiogram by potenAlthough the pattern tials developed during the activation of the left ventricle. was often apparent in Lead ~VR, onl\- one case required this lead for diagnosis, the strain pattern also being present in Leads V, and ir 4n (and V any. In general, the most striking heart strain patterns were observed in I,eads VnR and V dR,’ although a pattern sufficient for diagnosis was usually concomitantly present in Lead VI. In retrospect, the correct diagnosis of right heart strain might have been arrived at in a greater numbei of the usual six-lead electrocardiograms had more attention been paid to the amplitude of the K wave and the time of onset of the “intrinsicoid” deflection in Lead I’?. The recognition of the classical abnormalities indicative of left heart strain in the standard limb leads heretofore has been based on the patterns usual11 present in “electricall>~” 1lorizontal and semihorizontal positions.” The pattern in the standard limb leads in “electricall~~” vertical and semivertical positions often closely resembles that previously considered indicative of right heart strain. A left ventricular strain pattern in the precordial leads usually makes possible a correct interpretation in such instances. However, even the trained observer often-requires the aid of the XV limb leads for their certain differentiation. I’he incidence of left heart strain in “electrically” vertical positions is attested to even in this small series of cases. It is further apparent that the pattern of left heart strain frequently may be observed only in the precordial leads recorded to the left of ITS, particularly in instances of significant clockwise rotation of the heart on its long axis (i.e., left ventricle displaced posteriorI\,). It is significant that records exhibiting left heart strain with a concordant pattern or a right axis shift in the standard limb leads are often electrocardiographicall~~ indicative of only left, and not combined, ventricular strain.:’ Our experience supports the fact that patterns diagnostic of previous (remote) myocardial infarction may be observed only in leads other than those The value of Lead aVL in the diagnosis of recent heretofore routinely taken. myocardial infarction involving the lateral wall of the left ventricle has alread) been demonstrated. 8 The value of Lead aVF in the diagnosis of recent posterior wall infarction has also been well established, particularly in its differentiation Lead aVF was found to be invaluable from the pattern of acute car pulmonale.9 in two of the thirty-three cases studied. Our study indicates that, of the additional leads employed, either VRR or VaR was unnecessary. Lead aVn was also not essential but was useful for 1,ead VT was not required in the presence routine clinical electrocardiography. of Leads aV1, and aVr. Lead Lr3 proved to be of less value than any of the added precordial leads, but proved of value in an occasional case of anterior wall inLead V,; was found to be invaluable, particularly in the diagnosis of farction. Leads V1 and V4R proved essential to the diagnosis of many left heart strain. Leads aVL and aVF were essential for the correct instances of right heart strain. interpretation of many specific and nonspecific electrocardiographic patterns (Table IV).
ROSENMAN
ET AL. :
VALUE
OF aV LIMB
AND
V CHEST
LEADS
583
The results of this study lead to the recommendation that the standard and aV limb leads and precordial leads VI, VZ, Vs, V 4, Vs, and Vg be employed for routine clinical electrocardiography. Lead V, is valuable in adults, especially when recent or old myocardial infarction is suspected clinically and when suspicious, but not diagnostic, changes are noted in Leads Vr and VZ. Lead ‘JaR should be recorded routinely in children. It is preferred to Lead V sa because of easier electro;le placement. The routine use of these leads will enhance greatly the clinical value of the electrocardiogram. We have established the practice of taking twelve leads in all patients in the Heart Station as a result of this study. In persons over 10 years, the leads are: I, II, III, aVR, aVL, aVr, Vr, VB, V 3, Vq, VS, and VC,. In those 10 years or younger, Va is omitted and VIn is used instead. SUMMARY
1. Five hundred and fifteen routine electrocardiograms were recorded and analyzed, employing the standard and aV limb leads and precordial leads Vr to VT, VsR, and VIs. Each electrocardiogram was interpreted independently using both the usual six-lead electrocardiogram (I, II, III, Vz, V 4, and V 5) and the fifteen leads mentioned previously. 2. Seventy-seven electrocardiograms (15 per cent) necessitated the presence of certain of the additional leads (aVL, aVr, V ?R, VI, Va, V,) for correct interpretation. 3. The aV limb leads proved essential to accurate interpretation in 6.8 per cent and certain of the additional precordial leads (V ds, VI, V 3, V,J in 8.2 per cent of the cases. 4. A good correlation between anatomic and “electrical” positions of the heart on its anteroposterior axis was found in 200 instances of normal electrocardiograms and those exhibiting nonspecific abnormalities or left heart strain. A poor correlation was encountered particularly in instances of marked enlargement of the heart. 5. The clinical value of the electrocardiogram has been shown to be significantly enhanced by takin g leads other than those heretofore routinely recorded at this institution (I, II, III, VP, V4, V,). 6. It is recommended that, for routine clinical electrocardiography in adults, the standard and the aV limb leads and the precordial leads Vr, Vs, Va, V 4, V5, and V 6 be employed. Lead VqR should also be recorded routinely in children under 10 years of age, and VI can be omitted below this age group. We are in the conduct advice.
greatly of this
indebted study
to the other and especially
members to Drs.
of the department for their invaluable help R. Langendorf and A. Pick for their critical
REFERENCES 1.
2. 3.
Wilson,
F. N., Johnston, F. D., Macleod, A. G., and Barker, P. S.: Electrocardiograms That Represent the Potential Variations of a Single Electrode, AM. HEART J. 9:447, 1933. Dolgin, M., Grau, S., and Katz, L. N.: Experimental Studies on the Validity of the Central Terminal of Wilson as an Indifferent Reference Point, AM. HEART J. 37:868, 1946. Dolgin, M.., Grau, S., and Katz, L. N.: A Comparison of Precordial Electrocardiograms Obtained with CR, CL, CF, and V Leads, AM. HEART J. 37:343, 1949.
584 4.
5. 6. 7. 8. 9.
10.
Il. 12. 13. 1-i.
AMERICAN
1Yilson,
HEART
JOURNAL
F. N., Johnston, F. I~., Kosenbaum, F. F., Erlanger, H., Kossmann, C. E., Hechr , H.. Cotrim. N.. de Oliviera. M.. Scarsi. R.. and Barker, P. S.: The Prerordial Electrocardiogram, Ah. HEART J.‘27:i9, 1944. Katz, L. N.: Electrocardiography., ed. 2, Philadelphia, 1946, Lea & Febiger. Myers, G. B., and Klein, H. A.: The Relation of Unipolar Limb Leads to I’recordial and Esophageal Leads, AM. HEART J. 35:727, 1948. Myers, G. B., Klein, H. A., and Storer, B. E.: The Electrocardiographic Diagnosis of Right Ventricular Hypertrophy, AM. HEART J. 35:1, 1948. Myers, G. B., Klein, H. .A., and Storer, B. E.: VII. Correlation of Electrocardiographic and Pathologic Findings in Lateral Infarction, AM. HEART I. 37:374, 1949. Myers, G. B., and-Oren, B. G.: The Use of the Augmented Unipolar Left Leg Lead in the Differentiation of the Normal From the Abnormal Q Wave in Standard Lead III, AM. HEART J. 29:708, 1945. Goldberger, E.: Simple, Indifferent, Electrocardiographic Electrode of Zero Potential and Technique of Obtaining Augmented, Unipolar, Extremity Leads, AM. HEART J. 23:483, 1942. Bryant, J. M., and Johnston, F. D.: Errors Encountered in the ITse of the Goldberger Central Terminal, J. Clin. Investigation 25:919, 1946. Sokolow, M., and Friedlander, R. D.: The Normal Unipolar Precordial and Limb Lead Electrocardiogram, AM. HEART J. 38:665, 1949. The Ventricular Complex in Left Ventricular Hypertrophy Sokolow, M., and Lyon, T. P.: as Obtained by Unipolar Precordial Limb Leads, AM. HEART J. 37:161, 1949. The Ventricular Complex in Right Ventricular HyperSokolow, M., and Lyon, T. P.: trophy as Obtained by ltnipolar Precordial Limb Leads, AM, HEART J. 38:2, 1949.