have demonstrated these typical responses to condition- ing. However, we detected no change in exercise heart rate, or cardiac, stroke volume or systemic vascular re- sistance indexes. Our patients did benefit from the con- ditioning program. Their exercise tolerance subjectively and objectively improved, with 8 to 14% increases in total exercise time, peak oxygen uptake and ventilatory anaerobic threshold, however, these indexes remained substantially reduced compared with those of normal subjects in our laboratory. Thus, deconditioning explains part, but not all of the abnormalities observed in sur- viving patients of childhood cancer.

One possible limitation of this study is the small number of patients studied. Although solicitation letters were sent to all eligible patients living within reasonable commuting distance of the hospital, ~25% agreed to participate. In addition, this self-selection may have skewed our data toward more severely affected subjects. This may explain the relative obesity of the study co- hort. However, we do not believe that self-selection re- sulted in an atypical study cohort, because before reha- bilitation, half the patients said that their exercise abili- ty was average or above average, and the results of the prerehabilitation exercise tests were simi1a.r to those re- ported in other studies that did not require a 1Zweek commitment. A further limitation of this study is the in- ability to separate anthracycline from radiation car- diotoxicity. Whereas 8 of 10 patients received either no radiotherapy or radiotherapy limited to areas thought not to affect cardiopulmonary function, 2 received thoracic radiotherapy.

Abnormalities of exercise response in children and young adults after cure of childhood cancer are not com- pletely reversed by an aerobic conditioning program. The residual abnormalities represent chronic cardio- pulmonary dysfunction secondary to their therapy with anthracyclines or irradiation. However, these patients de-

velop both subjective and objective improvement in their exercise tolerance after a 12-week aerobic conditioning program. Therefore, we believe that aerobic condition- ing is indicated in some patients after cure of childhood cancer.

Acknowledgment: We would like to thank Anna T. Meadows, MD, and Jean Fergusson, RN, for invaluable assistance in recruiting patients for the study.

1. Hwkenbeny MJ, Goody DK, Bennett BS. Childhood cancers: incidence, etiol- ogy, diagnosis, and treatment. Pediatr Nurs 1990;16:23%245. 2. Lipshultz SE, Golan SD, Gelber RD, Perez Atayde AR, SaIlan SE, Sanders SP. Late cardiac effects of doxorubicin therapy for acute lymphoblastic leukemia in childhood. N Engl J Med 1991;324:808-815. 3. Larsen RL, Barber F, Heise CT, August CS. Exercise assessment of cardiac function in children and young adults before and after bone marrow transplanta- tion. Pediatrics 1992;89:722-729. 4. Larsen RL, J&&i RI, Vetter VL, Meadows AT, Silber JH, Barber G. Elec- trocardiographic changes and arrhythmias after cancer therapy in children and young adults. Am J Cardiol 1992;70:73-77. 8. Bar-Or 0. Pediatric Sports Medicine for the Practitioner. New York Springer- Verlag, 1983: 343-348. 6. Frisancho AR. New norms of upper limb fat and muscle areas for assessment of nutritional status. Am J C&J Nufr 1981;34:254&2545. 7. Frisancho AR. Triceps skin fold and upper arm muscle size norms for assess- ment of nutrition statas. Am J Clin Nufr 1974,27:1052-1058. 8. Bjarke B, Eriksson BO, Saltin 8. ATP, CP, and lactate concentrations in mus- cle tissue during exercise in male patients with tetralogy of Fallot. Stand .I Clin Lab Invest 1974;33:255-260. 9. Triebwasser JH, Johnson RL, Burpo RP, Campbell JC, Reardon WC, Blomquist G. Noninvasive determination of cardiac output by a modified acetylene helium rebreathing procedure utilizing mass spectrometer measurements. Aviat Space Env- iron Med 1977;48:203-209. 10. Beaver WL, Wasserman K, Whipp BJ. A new method for detecting anaero- bic threshold by gas exchange. J Appl Physiol 1986;60:2020-2027. 11. Vaccaro P, Galioto FM, Bradley LM, Vaccaro J. Effect of physical training on exercise tolerance of children following surgical repair of D-transposition of the great arteries. J Sports Med Phys Fitness 1987;27:443*8. 12. Lefrak EA, Pitha J, Rosenheim S, Gottlieb JA. A clinicopathologic analysis of adriamycin cardiotoxicity. Cancer 1973;32:302-314. 13. Kadota RP, Burgert EO, Driscoll DJ, Evans RG, Gilchrist GS. Cardiopulmo- nary function in long-term survivors of childhood Hodgkin’s lymphoma: a pilot study. Mayo Clin Proc 1988;63:362-367. 14. Mahon AD, Vaccaro P. Ventilatoty threshold and V02max changes in chil- dren following endurance training. Med Sci Sports Exert 1989;21:425-431.

Recognition of Electrocardiographic Electrode Misplacements Involving the Ground (Right Leg) Electrode Wesley K. Haisty, Jr., MD, Olle Pahlm, MD, Lars Edenbrandt, MD, and Kevin Newman, MD

A ccurate electrocardiographic (ECG) interpretation by computer or manually requires that the electrocar-

diogram be recorded with all electrodes in proper posi- tions. All possible electrode placement errors involving the active limb electrodes (right and left arm, and left leg) have been described.’ The most frequent electrode placement error is the left/right arm electrode reversal; because it is so common and easily recognized, many computerized ECG recorders have built-in logic to rec- ognize it.2,3 The ground electrode, placed on the right

From the Department of Medicine, Section on Cardiology, Bowman Gray School of Medicine, Medical Center Drive, Winston-Salem, North Carolina 27157; and the Department of Clinical Physiology, Uni- versity of Lund, Lund, Sweden. This study was supported in part by Grant 90-03775 from the Swedish National Board for Industrial and Technical Development. Manuscript received November 20, 1991; revised manuscript received and accepted January 7, 1993.

leg by convention, may be positioned anywhere on the body without affecting the ECG waveforms. However, if it is erroneously positioned on an arm and if an arm electrode is therefore positioned on the right leg, a char- acteristic alteration of the electrocardiogram occurs. There are no strategies in computerized ECG recorders for automatic recognition of this electrode reversal, and it is not discussed in standard textbooks of electrocar- diography.1j4,5 The main purposes of this study were to: (1) describe the characteristic ECG appearance of a right arm/leg electrode reversal, (2) propose an algorithm for its automated recognition, and (3) survey cardiologists’ recognition of this electrode reversal.

The effects of the right armlleg electrode reversal were studied, and an algorithm for automated recogni- tion was developed using a learning set of electrocar- diograms obtained at the University Hospital, Lund,

1490 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 71 JUNE 15,1993

FIGURE 1. Correct electre cardiogram (/eff) has normal QRS amplitudes and T-wave contiguration. After right arm/leg electrode reversal (riglit), criteria for low volt- age are fultilled, and corn puter interpretation sug gests pulmonary disease.

RGURE 2. Frontal plane QRS axis of correct electrocap diogram (left) is approxi- mately SO”, and that of right arm/leg reversal (@ttj 150”. Computer interprets tion suggests left posterior fascicular block.

BRIEF REPORTS

FIGURE 3. Frontal plane QRS axis of electrocardiogram with right arm/leg electrode reversal (dght) is -30”. Corn puter interpretation sag gests left-axis deviation.

RGURE 4. Q-wave duration in lead aVF is <30 ms in cor- rect electrocardio@am (/effJ, aad r40 ms in electr* cardiogbm with rigM arm/ leg electrode reversal frigm), which fulfills computer trite tia for inferior myocardial infarction.

1492 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 71 JUNE 15,1993

Sweden. The algorithm was tested on an independent set of electrocardiograms obtained at the Wake Forest University Medical Center, Winston-Salem, North Car- olina. To evaluate sensitivity, electrocardiograms with right armlleg electrodes reversed were recorded in 240 patients (I110 in the lea?-rung set, and I40 in the test set). These electrocardiograms were recorded in ran- domly selected patients referred for a resting electro- cardiogram. Specificity in the learning set was evaluat- ed using 1,592 correctly recorded electrocardiograms available from research data bases in Lund. Spectjicity in the test set was evaluated using electrocardiograms of 8,048 patients who had undergone diagnostic car- diac catheterization in Winston-Salem; serial electro- cardiograms were examined to exclude electrode rever- sals in this set. Electrocardiograms from Lund were recorded on Siemens recorders (Siemens-Elema AB, Solna, Sweden), and waveform measurements were ob- tained with custom software. Electrocardiograms from Winston-Salem were recorded on Marquette recorders (Marquette Electronics, Inc., Milwaukee, Wisconsin) and measured by the Marquette 12SL program.3 Con@ dence limits jar sensitivity and spect@ity were estimat- ed using the method suggested by Diamond.”

To confiym our belief that electrocardiograms with right armlleg electrode reversal may not be recognized as arttfactual, 25 board-certtjied cardiologists were asked to interpret 5 electrocardiograms, 1 of which was normal except .for right armlleg electrode reversal. The key electrocardiogram was positioned second among the 5 electrocardiograms to avoid drawing attention to it, and to resemble clinical practice. The other electro- cardiograms were abnormal (1 with right bundle branch block and 3 with moderately complex arrhythmias). The number of cardiologists recognizing or suspecting an electrode misplacement was counted.

Characteristic patterns were noted in the altered electrocardiograms. QRS axes in the jrontal plane changed, low amplitudes appeared in lead II, and all other ,frontal leads resembled scaled variations of lead III. These were the changes expected, because active electrodes are on the lefr arm and both legs, and the potential d@erence between the legs is known to be small. The appearance of the altered electrocardiogram depended on the characteristics of lead III in the orig- inal electrocardiogram. When lead III was of low am- plitude, the altered electrocardiogram displayed low voltage in all frontal plane leads (Figure 1). When lead III had large, positive amplitudes, the ,frontal-plane axis approximated +1.50” (i.e., extreme right-axis deviation) (Figure 2). When lead III had large, negative ampli- tudes, the ,frontal-plane axis approximated -30” (Figure 3).

A particularly interesting transjormation occurred in patients with Q waves in the inferior leads. When Q waves were more apparent in lead III than in aVF, the altered electrocardiogram showed prominent Q waves in both III and aVF (Figure 4), suggesting inferior myocardial infarction. When Q waves were most ap- parent in lead aVF, the altered electrocardiograms showed less evidence of inferior infarction. As expect- ed, changes in the precordial leads were much less

prominent than in the frontal plane leads. Only in very fav cases did the changes alter the appearance of pre- cordial leads sujficiently to aflect diagnostic conclusions (Figure 5).

The QRS amnlitudes in Lund II MIQW ~w~~td in ?Glo

learning set. In Figure 6, the greatest positive ampli- tude is plotted against the greatest negative amplitude. All 1,592 correct electrocardiograms had positive amplitudes >I35 IJV and negative amplitudes 350 ,uV; conversely, 97 of 100 right armileg electrocardiograms had amplitudes less than these values. These amplitude values were used.as a criterion for recognition of the right armlleg electrode reversal in the test set. The cri-

. . . . . :

j. “““‘:‘.

. . . . . : : :

.:. _.,:.

&

. ...,

II

GURE 5. Top and middle waveforms show leads Vg and 11 of patient with correct electrode placement. Bottom wave- form shows lead V, of rigBt arm/leg electrode reverse1 in Same patient. Marluxi changes in 1 and ST-T waveforms 00 car ornery with in correct Vs.

BRIEF REPORTS %4

Negative amplitude (E.IV)

I

OO I. -I I A

50 100 150 200

Positive amplitude (I.~V)

terion correctly recognized 136 of 140 electrocardio- grams with the right armlleg reversals (97.1% sensitiv- ity) while falsely recognizing only 4 of 8,048 correctly recorded electrocardiograms (99.95% specificity). Using the pooled data sets, 95% con.dence limits on sensitivity and specificity were 9.5.7-97.870 and 99.89-99.98%, respectively. No cardiologist interpret- ing the 5 electrocardiograms commented on the low amplitude of lead II or suggested electrode misplace- ment. A few cardiologists noted lef-axis deviation or left anterior hemiblock.

The 3 active electrodes can be misplaced in 5 dif- ferent ways that have been described in detail.’ When the ground electrode is also considered, 18 additional misplacements can occur; some of these result in 2 ac- tive electrodes measuring the potential difference be- tween the legs. The ECG hallmark of these misplace- ments is that 1 standard lead (I, Il or III) approximates a straight line. When both arm electrodes are inter- changed with those on both legs, lead I shows the straight line. With a left arm/right leg electrode reversal, the straight line appears in lead III.

The most frequent electrode reversal involving the ground electrode is the right arm/leg reversal; in this case, lead II will have low amplitudes. With correct electrode placement, large QRS amplitudes are usually

TJLA RLi LL II

HGURE 6. Scatter plot of maximal posi- tive and negative amplitudes for learning set of 100 electrocardiograms recorded with right arm/leg lead switch, and those patients (among 1,592) with amplitudes in lead II c225/125 pV.

found in lead II, and a simple criterion using QRS amplitudes accurately separated correctly recorded electrocardiograms from those with right arm/leg elec- trode reversal. Computerized ECG recorders, using such a criterion, could advise the technician to consider elec- trode misplacement and resolve the problem. Because misplacement of the ground electrode occurs infre- quently, criteria for its recognition need to be highly spe- cific so that false-positive interpretations are infrequent. Results of the present study with 99.95% specificity and 97% sensitivity are favorable. Sensitivity could be en- hanced by including P- or T-wave criteria, or both. Al- gorithms similar to the one developed in this study may be used to recognize the other electrode reversals posi- tioning active electrodes on both legs.

The changes noted may be clinically important: Low, frontal plane voltage may suggest pulmonary or pericar- dial disease. Marked axis deviation may suggest cardiac or pulmonary abnormalities. The appearance of a signifi- cant Q wave in lead aVF may suggest inferior myocar- dial infarction. These frndings may appear more signifi- cant if thought to be of recent onset by serial compari- son of electrocardiograms.

All observed changes can be explained in regard to the physical relation among the 6 limb leads and to the contribution of the central terminal to the precordial leads. Only limb lead IIl is recorded mrectiy (Figure 7). Leads I and aVL approximate an inverted lead IlI; aVR and aVF approximate lead III at half amplitude. These observations apply to all cases, because the 6 leads are mathematically related. The central terminal becomes the average of left arm, and right and left leg potentials, rather than the usual average of right and left arm, and left leg potentials; the difference between the 2 is equal to one third of the difference between the right arm and leg potentials, which approximates one third of standard lead II and will be subtracted from all precor- dial leads. Thus, changes may be noted in the precor- dial waveforms if lead II has large amplitude (Figure 2).

I

RGURE 7. Schematic representation of Einthoven’s triangle We were surprised that no cardiologist in the survey

(I&J versus changes in effective lead axes, and distortion suspected electrode misplacement; however, this con- of Einthoven’s triangle (right) secondary to right arm (RA)/ lirms our belief that the abnormality is frequently not leg (RL) electrode reversal. LA = left arm; LL q left leg. recognized, even by experienced electrocardiographers.

1494 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 71 JUNE 15,1993

The results of this study should alert physicians to consider right arm/leg electrode reversal when lead II of the electrocardiogram approximates a straight line, and frontal leads I and III show the same waveform, but of opposite sign. Manufacturers of interpretive, computer- ized t%Cti recorders are encouraged to implement recoe- nition algorithms similar to the one developed in this study.

Acknowledgment: We would like to credit Ross Fletcher, MD, for correctly explaining this electrocar-

diographic abnotmality in 1973 while training Dr. Haisty.

1. Marriott HJL. Practical Electrocardiography. 8th ed. Baltimore: Williams and Wilkins, 1983:33. ^. .2;ixdi” 2. “ubL~“.;c ,LLLAL ;,,. ;“;‘&&‘u,c TV.“‘, LIlWliS TCV’, mib. Currr- prehemive Eiecmc~dioiogy. New Ycrk ?ergm~on, 198Y:i530. 3. Physician’s Guide to Marquette Electronics Resting ECG Analysis. Milwaukee: Marquette Electronics Inc., 19X7:53. 4. Goldman M.J. Principles 01 Clinical Electrocardiography. 12th ed. East Nolwalk, Connecticut: Appleton-Century-Crofts, 1986. 5. Goldschlager, N. Principles of Clinical Electmcardiogmphy. East Norwalk, Con- necticut: Appleton-Cetlltury-Crofts, 1989. 6. Diamond GA. Limited assurances. Am J Cardiol 19X%63:99-100.

Noninvasive Estimation of Right Ventricular dP/dt in Patients with Tricuspid Valve Regurgitation Joseph Anconina, MD, Nicolas Danchin, MD, Christine Selton-Suty, MD, Karl Isaaz, MD, Yves Juilliere, MD, Philippe Buffet, MD, Francois Edel, MD, and Francois Cherrier, MD

1 he role of right ventricular (RV) function has been proven to be important in various cardiac diseases,

including coronary artery disease*,* or dilated cardiomy- opathy. The use of Doppler echocardiography to mea- sure RV inflow has permuted assessment of RV diastolic function in various diseases.3 However, the Doppler echocardiographic approach of RV systolic function re- mains neglected. A Doppler-derived rate of left ventric- ular pressure rise using the mitral regurgitant flow ve- locity pattern, recorded by continuous-wave Doppler echocardiography, has proved to be correlated with peak dP/dt obtained at cardiac catheterization.4s5 Because tri- cuspid regurgitation (TR) is often found in a variety of cardiac diseases and in normal’ subjectq6 we hypothe- sized that the rate of RV pressure rise could be predict- ed from the continuous-wave TR signal, in a way sim- ilar to that used for the rate of left ventricular pressure rise. Therefore, the purpose of the present study was to correlate Doppler-derived RV dP/dt with dP/dt obtained simultaneously from invasive measurements.

We prospectively pegormed Doppler echocardio- graphic studies in 14 patients (9 men and 5 women, mean age 59 years, range 39 to 73) with mild to severe TR who were referred to our institution for right-sided cardiac catheterization. Both Doppler and catheteriza- tion studies were performed simultaneously. Six patients were excluded. Three because of an inadequate Doppler study, 2 had mitral valve prosthesis and 1 had carci- noid heart disease. Therefore, 8 patients (4 had mitral regurgitation, 3 coronary artery disease, and I dilated cardiomyopathy) were included in the study. Seven pa- tients were in New York Heart Association functional class II heart failure and I patient was in class III.

Right-sided cardiac catheterization was performed, with no premeditation using a standard percutaneous technique. At the end of the procedure a 5Fr Millar mi- cromanometer-tipped catheter was inserted through the

From Cardioiogy A and B, Chu Nancy-Brabois, 54500 Vandoeuvre- I&s-Nancy, Fran& This report was suppcnted in part by a grant from the FCdkration Rancaise de Cardiologie, Paris, France. Manuscript received August f2, 1992; revised m&script received January 4,1993, and accepted January 5.

right femoral vein to the right ventricle to obtain RV pressure signals. Electronic dtflerentiation of the RV pressure pulse was per$ormed to obtain peak dPldt. Then the pressure monitor was connected to the echo machine so that pressure tracings and Doppler signal were displayed simultaneously on the echo screen (Fig- ure 1). The continuous-wave TR signal was obtained from the apex using a duplex or nonimaging transduc- er with a ,fiequency of 2.0 MHz (Vingmed CFM 700, Diasonics). The maximal TR velocity recorded was used. All measurements were peformed directly from the video screen using the software program incorpo- rated in the equipment. Two points, Vr and V2, were se- lected on the rising segment of the TR velocity curve and the time interval (At) between them was measured (Figure 2, left). The increase in instantaneous velocity between Vr and V2 was converted to RV-right atria1 pressure gradient (AP) using the simpltjied Bernoulli equation; the rate qf RV pressure rise was obtained as APlAt assuming right atria1 pressure variation negligi- ble during early systole, even in the presence qf TR. For each patient the following values of VI and V2 were

FIGURE 1. Simultaneous recordings of continuous-wave Doppler tricuspid regurgitation signal and cathetetierived dP/dt curve displayed on the echo screen.

BRIEF REPORTS 1495