the thorax, rather than to decreased ventricular dimensions. 1. Brady DA. A theoretical analysis of intracavitary blood mass influence on the heart-lead relationship. Circ Res 1956;4:731-738. 2. Voukydis PC. Effect of intracardiac blood on the electrocardiogram. N Engl J Med
1974;291:612-616.
3. Manoach M, Gitter S, Grossman E, Varon D, Gassner S. Influence of hemorrhage on the QRS complex of the electrocardiogram. Am Heart J 1971;82:55-61. 4. Bayley RH, Berry PM. “Body surface” potentials produced by the eccentric dipole in the heart wall of the non-homogenous volume conductor. Am Heart J 1963,65:200-207.
5. Feldman T, Borow KM, Neumann A, Lang RM, Childers RW. Relation of electrocardiographic R-wave amplitude to changes in left ventricular chamber size and position in normal subjects. Am J Cardiol 1985:55:1168-l 174. 6. Battler A, Froelicher VF, Gallagher KP, Kumada T, McKown D, Kemper WS, Ross J. Effects of changes in ventricular size on regional and surface QRS amplitudes in the conscious dog. Circulation 1980,62:174-180. 7. Bonoris PE, Greenberg PS, Christison GW, Castellanet MJ, Ellestad MH. Evaluation of R wave amplitude changes versus ST-segment depression in stress testing. Circulation 1978;57:904-910. 8. Battler A, Froelicher V, Slutsky R, Ashburn W. Relationship of QRS ampli-
tude changes during exercise to left ventricular function and volumes and the diagnosis of coronary artery disease. Cireuhtion 1979,60:1004-1013. 9. Mercuro G, Fonzo R, Rivano CA, Dessi N, Cherchi A. Variazioni del QRS e dimensioni ecocardiogratiche del ventricolo sinistro in rapport0 all’esercizio muscolare in posizione seduta nell’individuo normale. Cardiobgio 1982;27:10611069.
10. Daniels S, Iskandrian AS, Hakki AH, Kane SA, Bemis CE, Horowitz LN, Greenspan AM, Segal BL. Correlation between changes in R wave amplitude and left ventricular volume induced by rapid atria1 pacing. Am Heart J 1984;107:71 l717. 11. Nelson CV, Rand PW, Angelakos ET, Hugenholtz PG. Effect of intracardiac blood on the spatial vectorcardiogram. Circ Res 1972;31:95-104. 12. Lekven J, Chatterjee. K, Tyberg JV, Parmley WW. Reduction in ventricular endocardial and epicardial potentials during acute increments in left ventricular dimensions. Am Heart .I 1979,98:20&206. 13. Rosenthal A, Restieaux NJ, Feig SA. Influence of acute variations in hematowit on the QRS complex of the Frank electrocardiogram. Circulation 1971;44;
456-46s. 14. Ross EA, Nissenson AR. Dialysis-associated hypoxemia: insights into pathophysiology and prevention. Semin Dialysis 1988;1:33-39. 15. Talbot S, Kilpatrick D, Jonathan A, Raphael MJ. QRS voltage of the electrocardiogram and Frank vectorcardiogram in relation to ventricular volume. Br Heart
J 1977;39:1109-1113.
False-Positive Treadmill Exercise Tests due to Computer Signal Averaging John A. Milliken, MD, Hosiar Abdollah, MB, and Gary W. Burggraf, MD ignificant ST depression may occur during exerS cise, despite the absence of demonstrable coronary disease by angiographic studies. Such false-positive tests often lead to further fruitless investigations and cause much unnecessary anxiety. Less well known are the falsepositive tests produced by computerized test systems, where ST depression is due to signal averaging, but absent from the “true” or “raw” electrocardiogram. Baseline drift 1is corrected but ST segments may show ST depression not present on the raw 12-lead electrocardiogram. This problem is most evident when healthy, asymptomatic men become “positive” at stage IV or more of the Bruce protocol. Despite the admonition by Chaitman2 that one should always have the true or raw electrocardiogram to review before interpreting a test as positive, most centers report these false-positive tests as abnormal. We selected 200 consecutivetreadmill exercise tests performed using the CaseZZMarquette system and the standard Bruce protocol. Each subject was carefully prepared with 10 electrodesapplied in the usual manner. The arm leads were shifted to below the clavicles, and the lower limb leadsto below the ribs. The 6 chestleads were placed in the standard locations, except for VI, which became V4R.3All were held firmly in place by a Jishnet body stocking. The skin was carefully prepared by shaving, rubbing vigorously and cleaning with an alcohol sponge before electrode application. Resting, standing and supine pretest 12-lead records were obtained, as well as a record every 3 minutes during the test, and every 2 minutes during recovery. A raw 12-lead electrocardiogram was also obtained after each of the signal averaged recordings. There wascontinuous moniFrom the Division of Cardiology, Queen’s University, Hotel Dieu Hospital, Kingston, Ontario, Canada K7L 5G2. Manuscript received July 17,1989; revised manuscript received and accepted August 29,1989. 946
THE AMERICAN
JOURNAL
OF CARDIOLOGY
VOLUME
65
toringof leads Vt, Vs and aVF during the test. Zf significant ST depressionwasnoted, a raw 12-lead electrocardiogram was obtained at once, to confirm the result before the test was terminated. Each patient wasencouraged to exercise to his or her maximum, but the test was always terminated at the patient’s request, especially if 90% of the target rate wasachieved or ST depression>2 mm occurred. Two hundred consecutivetestswere interpreted using the averaged complex and averaged 12-lead records. After this, the raw 12-lead data were reviewed. The following definitions were usedin relation to the baseline electrocardiogram. A POSITIVE TEST: defined as >I mm of ST depression 80 ms after the Jpoint present in any lead of the true or raw 12-lead electrocardiogram. A FALSE-POSITIVE TEST: defined as >l mm of ST depression80 msafter the Jpoint present in any lead of the averaged 12-lead electrocardiogram, but absent in the true or raw 12-lead electrocardiogram. A NEGATIVE TEST: defined as
1974;291:612-616.
3. Manoach M, Gitter S, Grossman E, Varon D, Gassner S. Influence of hemorrhage on the QRS complex of the electrocardiogram. Am Heart J 1971;82:55-61. 4. Bayley RH, Berry PM. “Body surface” potentials produced by the eccentric dipole in the heart wall of the non-homogenous volume conductor. Am Heart J 1963,65:200-207.
5. Feldman T, Borow KM, Neumann A, Lang RM, Childers RW. Relation of electrocardiographic R-wave amplitude to changes in left ventricular chamber size and position in normal subjects. Am J Cardiol 1985:55:1168-l 174. 6. Battler A, Froelicher VF, Gallagher KP, Kumada T, McKown D, Kemper WS, Ross J. Effects of changes in ventricular size on regional and surface QRS amplitudes in the conscious dog. Circulation 1980,62:174-180. 7. Bonoris PE, Greenberg PS, Christison GW, Castellanet MJ, Ellestad MH. Evaluation of R wave amplitude changes versus ST-segment depression in stress testing. Circulation 1978;57:904-910. 8. Battler A, Froelicher V, Slutsky R, Ashburn W. Relationship of QRS ampli-
tude changes during exercise to left ventricular function and volumes and the diagnosis of coronary artery disease. Cireuhtion 1979,60:1004-1013. 9. Mercuro G, Fonzo R, Rivano CA, Dessi N, Cherchi A. Variazioni del QRS e dimensioni ecocardiogratiche del ventricolo sinistro in rapport0 all’esercizio muscolare in posizione seduta nell’individuo normale. Cardiobgio 1982;27:10611069.
10. Daniels S, Iskandrian AS, Hakki AH, Kane SA, Bemis CE, Horowitz LN, Greenspan AM, Segal BL. Correlation between changes in R wave amplitude and left ventricular volume induced by rapid atria1 pacing. Am Heart J 1984;107:71 l717. 11. Nelson CV, Rand PW, Angelakos ET, Hugenholtz PG. Effect of intracardiac blood on the spatial vectorcardiogram. Circ Res 1972;31:95-104. 12. Lekven J, Chatterjee. K, Tyberg JV, Parmley WW. Reduction in ventricular endocardial and epicardial potentials during acute increments in left ventricular dimensions. Am Heart .I 1979,98:20&206. 13. Rosenthal A, Restieaux NJ, Feig SA. Influence of acute variations in hematowit on the QRS complex of the Frank electrocardiogram. Circulation 1971;44;
456-46s. 14. Ross EA, Nissenson AR. Dialysis-associated hypoxemia: insights into pathophysiology and prevention. Semin Dialysis 1988;1:33-39. 15. Talbot S, Kilpatrick D, Jonathan A, Raphael MJ. QRS voltage of the electrocardiogram and Frank vectorcardiogram in relation to ventricular volume. Br Heart
J 1977;39:1109-1113.
False-Positive Treadmill Exercise Tests due to Computer Signal Averaging John A. Milliken, MD, Hosiar Abdollah, MB, and Gary W. Burggraf, MD ignificant ST depression may occur during exerS cise, despite the absence of demonstrable coronary disease by angiographic studies. Such false-positive tests often lead to further fruitless investigations and cause much unnecessary anxiety. Less well known are the falsepositive tests produced by computerized test systems, where ST depression is due to signal averaging, but absent from the “true” or “raw” electrocardiogram. Baseline drift 1is corrected but ST segments may show ST depression not present on the raw 12-lead electrocardiogram. This problem is most evident when healthy, asymptomatic men become “positive” at stage IV or more of the Bruce protocol. Despite the admonition by Chaitman2 that one should always have the true or raw electrocardiogram to review before interpreting a test as positive, most centers report these false-positive tests as abnormal. We selected 200 consecutivetreadmill exercise tests performed using the CaseZZMarquette system and the standard Bruce protocol. Each subject was carefully prepared with 10 electrodesapplied in the usual manner. The arm leads were shifted to below the clavicles, and the lower limb leadsto below the ribs. The 6 chestleads were placed in the standard locations, except for VI, which became V4R.3All were held firmly in place by a Jishnet body stocking. The skin was carefully prepared by shaving, rubbing vigorously and cleaning with an alcohol sponge before electrode application. Resting, standing and supine pretest 12-lead records were obtained, as well as a record every 3 minutes during the test, and every 2 minutes during recovery. A raw 12-lead electrocardiogram was also obtained after each of the signal averaged recordings. There wascontinuous moniFrom the Division of Cardiology, Queen’s University, Hotel Dieu Hospital, Kingston, Ontario, Canada K7L 5G2. Manuscript received July 17,1989; revised manuscript received and accepted August 29,1989. 946
THE AMERICAN
JOURNAL
OF CARDIOLOGY
VOLUME
65
toringof leads Vt, Vs and aVF during the test. Zf significant ST depressionwasnoted, a raw 12-lead electrocardiogram was obtained at once, to confirm the result before the test was terminated. Each patient wasencouraged to exercise to his or her maximum, but the test was always terminated at the patient’s request, especially if 90% of the target rate wasachieved or ST depression>2 mm occurred. Two hundred consecutivetestswere interpreted using the averaged complex and averaged 12-lead records. After this, the raw 12-lead data were reviewed. The following definitions were usedin relation to the baseline electrocardiogram. A POSITIVE TEST: defined as >I mm of ST depression 80 ms after the Jpoint present in any lead of the true or raw 12-lead electrocardiogram. A FALSE-POSITIVE TEST: defined as >l mm of ST depression80 msafter the Jpoint present in any lead of the averaged 12-lead electrocardiogram, but absent in the true or raw 12-lead electrocardiogram. A NEGATIVE TEST: defined as
