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Scalar versus vector electrocardiography to determine right coronary artery or left circumflex coronary artery occlusion in inferior wall acute myocardial infarction
READERS’ COMMENTS Transesophageal Echocardiography During Cardioversion of Atrial Fibrillation
We would like to comment on the report by Kamp et al1 on transesophageal echocardiography for early cardioversion of atrial fibrillation. The authors question the assumption that patients with atrial fibrillation ⱕ2 days in duration have no significant risk of stroke if they undergo cardioversion without anticoagulation. They cite a study that found left atrial thrombi in 14% of patients with AF ⬍3 days in duration.2 However, it is not mentioned that 17% of the latter study had a recent thromboembolic event; 43% of these patients had congestive heart failure and only 2% of the patients received anticoagulation therapy. Thus, the study population consisted of a group at high risk for atrial thrombi. This is not the group of patients that often presents with acute onset of atrial fibrillation. In contrast, a study by Weigner et al3 showed that the incidence of thromboembolic events was only 0.8% in 357 patients with atrial fibrillation ⬍48 hours in duration who either had spontaneous conversion to sinus rhythm or underwent cardioversion. In this respect, it is interesting that our study group found that electrical cardioversion does not induce atrial stunning in patients with atrial fibrillation ⬍48 hours in duration.4 This finding supports the statement of Kamp et al, that patients with AF ⬍3 days in duration may be at lower risk for atrial stunning and for developing emboli after cardioversion. Heyder Omran, Berndt Lu¨deritz,
MD MD
Bonn, Germany 19 September 2000
Letters (from the United States) concerning a particular article in The American Journal of Cardiology姞 must be received within 2 months of the article’s publication, and should be limited (with rare exceptions) to 2 doublespaced typewritten pages. Two copies must be submitted.
126
1. Kamp O, Verhorst PMJ, Visser CA. Transesophageal echocardiography for early cardioversion of atrial fibrillation. Am J Cardiol 2000;86(suppl):46G– 50G. 2. Stoddard MF, Dawkins PR, Prince CR, Ammash NM. Left atrial appendage thrombus is not uncommon in patients with acute atrial fibrillation and a recent neurological event: a transesophageal echocardiographic study. J Am Coll Cardiol 1995;25: 452– 459. 3. Weigner MJ, Caulfield TA, Danias PG, Silverman DI, Manning WJ. Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours. Ann Intern Med 1997;126:615– 620. 4. Omran H, Jung W, Lu¨deritz B. Risk of thromboembolism after acute cardioversion of atrial fibrillation. Lancet 1998;352:1280.
III and isoelectric or slightly increased in lead I. These findings were emphasized nearly 50 years ago by Grant2 and are as simplistic and valuable now as they were then. Learn of the vector, use it, and avoid the tediously long and easily forgotten descriptions of various wave findings engendered by scalar electrocardiography.
PII S0002-9149(00)01420-X
Philadelphia, Pennsylvania 10 August 2000
Scalar Versus Vector Electrocardiography to Determine Right Coronary Artery or Left Circumflex Coronary Artery Occlusion in Inferior Wall Acute Myocardial Infarction
Boon-Lock Chia et al1 report on the “Usefulness of ST Elevation II/III Ratio and ST Deviation in Lead I for Identifying the Culprit Artery in Inferior Wall Acute Myocardial Infarction,” which appeared in The American Journal of Cardiology. They observed that an ST II/III ratio of 1 or an isoelectric ST segment in lead I are sensitive and specific markers of left circumflex coronary artery occlusion, whereas an ST II/III ratio ⬍1 (ST-segment elevation in lead III ⬎ II) or ST depression in lead I are sensitive and specific markers of right coronary artery occlusion. They then state that these 4 criteria are easily obtained from the standard 12-lead electrocardiogram. They did not indicate that it is much easier to determine by inspection the mean ST vector. In right coronary artery occlusion, the mean ST vector is directed approximately 120°, and in circumflex artery occlusion approximately 75°. A lead has the largest deflection if the vector is parallel to it, and the smallest deflection if perpendicular. Thus, in right coronary artery occlusion, ST-segment elevation is greatest in lead III, and in circumflex artery occlusion ST-segment elevation is similar in leads II and
©2001 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 87 January 1, 2001
Jacob Zatuchni,
MD
1. Chia B-L, Yip JWL, Tan H-C, Lim Y-T. Usefulness of ST elevation II/III Ratio and ST Deviation in Lead I for identifying the culprit artery in inferior wall acute myocardial infarction. Am J Cardiol 2000;86:341–343. 2. Grant RP. Clinical Electrocardiography. The Spatial Vector Approach. New York, Toronto, London: McGraw-Hill Book Co., 1957. PII S0002-9149(00)01353-9
Electrocardiographic Lead Reversal
In the 2 articles published in the AJC,1,2 we have shown that artificial neural networks can detect some of the most common electrocardiographic lead reversals, at levels of sensitivity and specificity not achieved by rule-based criteria. One main point was that the specificity levels must be very high; otherwise there will be a lot of correctly recorded electrocardiograms (ECGs) falsely claimed as lead reversals if our method were to be used in automated electrocardiographic interpretation devices. With references to our results, Abdollah and Milliken presented a method based on a simple P-wave algorithm for detection of one of the lead reversals we have studied, the left arm/left foot lead reversal. On a data set of 70 electrocardiographic recordings, they achieved a sensitivity of 90% (atrial fibrillation not included) compared with our 57% for the same lead reversal.2 However, we presented a specificity of 99.97%, but no specificity levels were presented by Abdollah and Milliken. We therefore implemented and
We would like to comment on the report by Kamp et al1 on transesophageal echocardiography for early cardioversion of atrial fibrillation. The authors question the assumption that patients with atrial fibrillation ⱕ2 days in duration have no significant risk of stroke if they undergo cardioversion without anticoagulation. They cite a study that found left atrial thrombi in 14% of patients with AF ⬍3 days in duration.2 However, it is not mentioned that 17% of the latter study had a recent thromboembolic event; 43% of these patients had congestive heart failure and only 2% of the patients received anticoagulation therapy. Thus, the study population consisted of a group at high risk for atrial thrombi. This is not the group of patients that often presents with acute onset of atrial fibrillation. In contrast, a study by Weigner et al3 showed that the incidence of thromboembolic events was only 0.8% in 357 patients with atrial fibrillation ⬍48 hours in duration who either had spontaneous conversion to sinus rhythm or underwent cardioversion. In this respect, it is interesting that our study group found that electrical cardioversion does not induce atrial stunning in patients with atrial fibrillation ⬍48 hours in duration.4 This finding supports the statement of Kamp et al, that patients with AF ⬍3 days in duration may be at lower risk for atrial stunning and for developing emboli after cardioversion. Heyder Omran, Berndt Lu¨deritz,
MD MD
Bonn, Germany 19 September 2000
Letters (from the United States) concerning a particular article in The American Journal of Cardiology姞 must be received within 2 months of the article’s publication, and should be limited (with rare exceptions) to 2 doublespaced typewritten pages. Two copies must be submitted.
126
1. Kamp O, Verhorst PMJ, Visser CA. Transesophageal echocardiography for early cardioversion of atrial fibrillation. Am J Cardiol 2000;86(suppl):46G– 50G. 2. Stoddard MF, Dawkins PR, Prince CR, Ammash NM. Left atrial appendage thrombus is not uncommon in patients with acute atrial fibrillation and a recent neurological event: a transesophageal echocardiographic study. J Am Coll Cardiol 1995;25: 452– 459. 3. Weigner MJ, Caulfield TA, Danias PG, Silverman DI, Manning WJ. Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours. Ann Intern Med 1997;126:615– 620. 4. Omran H, Jung W, Lu¨deritz B. Risk of thromboembolism after acute cardioversion of atrial fibrillation. Lancet 1998;352:1280.
III and isoelectric or slightly increased in lead I. These findings were emphasized nearly 50 years ago by Grant2 and are as simplistic and valuable now as they were then. Learn of the vector, use it, and avoid the tediously long and easily forgotten descriptions of various wave findings engendered by scalar electrocardiography.
PII S0002-9149(00)01420-X
Philadelphia, Pennsylvania 10 August 2000
Scalar Versus Vector Electrocardiography to Determine Right Coronary Artery or Left Circumflex Coronary Artery Occlusion in Inferior Wall Acute Myocardial Infarction
Boon-Lock Chia et al1 report on the “Usefulness of ST Elevation II/III Ratio and ST Deviation in Lead I for Identifying the Culprit Artery in Inferior Wall Acute Myocardial Infarction,” which appeared in The American Journal of Cardiology. They observed that an ST II/III ratio of 1 or an isoelectric ST segment in lead I are sensitive and specific markers of left circumflex coronary artery occlusion, whereas an ST II/III ratio ⬍1 (ST-segment elevation in lead III ⬎ II) or ST depression in lead I are sensitive and specific markers of right coronary artery occlusion. They then state that these 4 criteria are easily obtained from the standard 12-lead electrocardiogram. They did not indicate that it is much easier to determine by inspection the mean ST vector. In right coronary artery occlusion, the mean ST vector is directed approximately 120°, and in circumflex artery occlusion approximately 75°. A lead has the largest deflection if the vector is parallel to it, and the smallest deflection if perpendicular. Thus, in right coronary artery occlusion, ST-segment elevation is greatest in lead III, and in circumflex artery occlusion ST-segment elevation is similar in leads II and
©2001 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 87 January 1, 2001
Jacob Zatuchni,
MD
1. Chia B-L, Yip JWL, Tan H-C, Lim Y-T. Usefulness of ST elevation II/III Ratio and ST Deviation in Lead I for identifying the culprit artery in inferior wall acute myocardial infarction. Am J Cardiol 2000;86:341–343. 2. Grant RP. Clinical Electrocardiography. The Spatial Vector Approach. New York, Toronto, London: McGraw-Hill Book Co., 1957. PII S0002-9149(00)01353-9
Electrocardiographic Lead Reversal
In the 2 articles published in the AJC,1,2 we have shown that artificial neural networks can detect some of the most common electrocardiographic lead reversals, at levels of sensitivity and specificity not achieved by rule-based criteria. One main point was that the specificity levels must be very high; otherwise there will be a lot of correctly recorded electrocardiograms (ECGs) falsely claimed as lead reversals if our method were to be used in automated electrocardiographic interpretation devices. With references to our results, Abdollah and Milliken presented a method based on a simple P-wave algorithm for detection of one of the lead reversals we have studied, the left arm/left foot lead reversal. On a data set of 70 electrocardiographic recordings, they achieved a sensitivity of 90% (atrial fibrillation not included) compared with our 57% for the same lead reversal.2 However, we presented a specificity of 99.97%, but no specificity levels were presented by Abdollah and Milliken. We therefore implemented and