- Email: [email protected]
Maybe a dazzle but not puzzle
Available online at www.sciencedirect.com
Journal of Electrocardiology 43 (2010) 682 – 685 www.jecgonline.com
Letters to the Editor Maybe a dazzle but not puzzle We would like to thank the author (Dr Rowlands) for his interest in our article. Also, we would like to add that we believe that his detailed mathematical explanations about limb lead misplacements will make our report more interesting. The author's warning about the equations between augmented unipolar derivations and bipolar limb derivations is absolutely correct, and his mathematical demonstration chain is very accurate. However, actually, we did not mean that aVF = lead II + (lead III/2), aVL = lead I − (lead III/2), and aVR = −lead I − (lead II/2). Contrary, we did mean that aVF = (lead II + lead III)/2, aVL = (lead I − lead III)/2, and aVR = (−lead I − lead II)/2, as one can only decipher first electrocardiogram (ECG; Fig. 1) by the latter explanation, not by the former. For example, aVL equals (lead I − lead III)/2 in the first ECG, not lead I − (lead III)/2. The author has correctly assumed that our expression represents the former because of missing parentheses. Of course, we should not ignore the mathematical science jargon and assume that these short relationships clearly represent what we wanted to express, even if they are very well known. We are in a full agreement with the author's explanations, as we would before. We would like to thank the author for pointing out this mathematical dictation error. Conversely, we do not endorse the explanation of “interchanging electrodes” on interesting part of our case. As the author pointed out, inadvertent interchange between right arm and right leg is very common in clinical practice and leads to record of a nearly flat line in lead II. However, this is not in accordance with our ECG findings and cannot explain the difference between 2 ECGs (as the author stated), and it is not what the fact is. First, in the situation of inadvertent interchange between right arm and right leg, lead II consists of potential difference between left leg and right leg, which is close, but evidently not equal, to zero. Accordingly, instead of drawing a perfect flat line as in our case (Fig. 1 in the original article), lead II draws a nearly flat line with tiny notches synchronized with QRS complexes in leads I and III. A tracing from our laboratory is given as an example below (Fig. 1). Without doubt, the author and the reviewers might have ECGs like the one in Fig. 1 in their ECG collection. This ECG is in accordance with known and brilliantly reclarified mathematical relationships by the author. However, in this case, if one carefully look at flat lead II, he or she can easily note the small deflections (arrows) arising from potential difference of QRS complexes between 0022-0736/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
left leg and right leg. This fact is also consistent with the article,1 which is very well written and referenced by the author himself. This article shows a good example of right arm-right leg lead misplacement (Fig. 3 in that article), and again, instead of being a perfect flat line, lead II contains aforementioned notches that are evident for an experienced eye. Another example is given for lead III (Fig. 5 in that article) in the same article with analogous appearance. Similar examples can be found in medical literature (for a detailed review, see Batchvarov et al,2 Fig. 3), including references of abovementioned report (Hoffman,3 Fig. 1; Rudiger et al,4 Fig. 3). Thus, it is not probable to explain the perfect flat line in our report with inadvertent electrode placement. A perfect flat line should bring probability of a disconnection error (or short circuit) into consideration, stemming from device itself. Moreover, it is not possible to explain second ECG (Fig. 2) with taking lead III as only normal reference lead, which is stated by the author, too. Fig. 2, beyond an assumption, is the real second ECG of the patient, and QRS morphology in limb leads is consistent with successive ECGs, derived from the same patient. Double, even triple, interconnection error cannot explain the difference between these 2 ECGs; this is already what makes this case interesting. The problem in this ECG is not misconnection, but disconnection problem probably arising from inside of the ECG machine. It can be easily seen that only similarity between these 2 ECGs, excluding precordial leads, is lead I. It is also not possible to record such an ECG with any combination of electrodes when lead I is correctly placed. Here, ECG was correctly recorded, but the device did not process lead II because of an internal error. Some ECG devices record 2 limb leads and compute the other ones, as pointed out before.5 Electrocardiogram devices using this method are inevitably obliged to use a 6 + 6 lead design, so they can print all limb leads simultaneously. The ECG machine in Fig. 1 in our report is such a device. Another interesting point to note is as the following; this device does not allow taking an ECG even with only one disconnected electrode. Thus, disconnection or short circuit is probably in the device itself. Electrocardiogram fans know very well how much information an ECG can give. Here, ECG warns clinicians about disconnection and leads the electric technician to look for a possible internal device disorder. Lastly, there is a more definitive and simple resolution for this issue. After the reported case, we tried to reproduce this artifact in a controlled situation with correct lead placement. An example for this and its control with a different device is
Letters to the Editor / Journal of Electrocardiology 43 (2010) 682–685
Fig. 1. An inadvertent interchange between right arm and right leg.
Fig. 2. Another artifact with the same ECG machine with correctly placed electrodes.
683
684
Letters to the Editor / Journal of Electrocardiology 43 (2010) 682–685
Fig. 3. Control ECG of Fig. 2 with a different ECG machine.
shown in Figs. 2 and 3. The device was repaired recently, and no more similar artifacts could be recorded. Hence, (1) the appearances are not those of inadvertent interchange between the right arm and right leg connections, as the author stated, and (2) “lead II was evidently disconnected” is a correct interpretation of our ECG findings. However, “evidently” can be considered an expression of underestimation after all and it would be better to be removed. We wish that these explanations would make the original report clearer and could answer the questions of the author. Emre Aslanger, MD Istanbul Faculty of Medicine Capa-Istanbul, Turkey E-mail address: [email protected] doi:10.1016/j.jelectrocard.2010.04.010
References 1. Rowlands DJ. Inadvertent interchange of electrocardiogram limb lead connections. Analysis of predicted consequences. J Electrocardiology 2008;41:84. 2. Batchvarov VN, Malik M, Camm AJ. Incorrect electrode cable connection during electrocardiographic recording. Europace 2007;9:1081. 3. Hoffman I. A flat line electrocardiogram in lead II is a marker for right arm/right leg electrode switch. J Electrocardiol 2007;40:226. 4. Rudiger A, et al. Electrocardiographic artifacts due to electrode misplacement and their frequency in different clinical settings. Am J Emerg Med 2007;25:174.
5. Drew BJ. Pitfalls and artifacts in electrocardiography. Cardiol Clin 2006;24:309.
An example of apparently normal electrocardiogram originating from incorrect electrocardiographic acquisition in a patient with ST-segment elevation myocardial infarction: Aslanger et al A valuable lesson and a clarification but still a puzzle. Author’s reply To the Editor, I was delighted to read the carefully considered reply from Aslanger et al to my earlier letter commenting on their article “An example of apparently normal electrocardiogram originating from incorrect electrocardiographic acquisition in a patient with ST-segment elevation myocardial infarction.”1 The authors have clarified the outstanding issues. In this case, there clearly was a hardware fault, giving rise to the recording problem in the original electrocardiogram. Such faults are, of course, very much less common than the inadvertent lead interchange, which I had surmised might (and substantially would) account for the appearances in their Fig. 1. The authors are absolutely correct, however, in pointing out that when there is a “flat line” during the recording of the limb leads (in lead II or lead III), close inspection of a high-quality recording will usually reveal very tiny, transient deflections synchronous with the QRS complexes in other leads. I recognize that when such
Journal of Electrocardiology 43 (2010) 682 – 685 www.jecgonline.com
Letters to the Editor Maybe a dazzle but not puzzle We would like to thank the author (Dr Rowlands) for his interest in our article. Also, we would like to add that we believe that his detailed mathematical explanations about limb lead misplacements will make our report more interesting. The author's warning about the equations between augmented unipolar derivations and bipolar limb derivations is absolutely correct, and his mathematical demonstration chain is very accurate. However, actually, we did not mean that aVF = lead II + (lead III/2), aVL = lead I − (lead III/2), and aVR = −lead I − (lead II/2). Contrary, we did mean that aVF = (lead II + lead III)/2, aVL = (lead I − lead III)/2, and aVR = (−lead I − lead II)/2, as one can only decipher first electrocardiogram (ECG; Fig. 1) by the latter explanation, not by the former. For example, aVL equals (lead I − lead III)/2 in the first ECG, not lead I − (lead III)/2. The author has correctly assumed that our expression represents the former because of missing parentheses. Of course, we should not ignore the mathematical science jargon and assume that these short relationships clearly represent what we wanted to express, even if they are very well known. We are in a full agreement with the author's explanations, as we would before. We would like to thank the author for pointing out this mathematical dictation error. Conversely, we do not endorse the explanation of “interchanging electrodes” on interesting part of our case. As the author pointed out, inadvertent interchange between right arm and right leg is very common in clinical practice and leads to record of a nearly flat line in lead II. However, this is not in accordance with our ECG findings and cannot explain the difference between 2 ECGs (as the author stated), and it is not what the fact is. First, in the situation of inadvertent interchange between right arm and right leg, lead II consists of potential difference between left leg and right leg, which is close, but evidently not equal, to zero. Accordingly, instead of drawing a perfect flat line as in our case (Fig. 1 in the original article), lead II draws a nearly flat line with tiny notches synchronized with QRS complexes in leads I and III. A tracing from our laboratory is given as an example below (Fig. 1). Without doubt, the author and the reviewers might have ECGs like the one in Fig. 1 in their ECG collection. This ECG is in accordance with known and brilliantly reclarified mathematical relationships by the author. However, in this case, if one carefully look at flat lead II, he or she can easily note the small deflections (arrows) arising from potential difference of QRS complexes between 0022-0736/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
left leg and right leg. This fact is also consistent with the article,1 which is very well written and referenced by the author himself. This article shows a good example of right arm-right leg lead misplacement (Fig. 3 in that article), and again, instead of being a perfect flat line, lead II contains aforementioned notches that are evident for an experienced eye. Another example is given for lead III (Fig. 5 in that article) in the same article with analogous appearance. Similar examples can be found in medical literature (for a detailed review, see Batchvarov et al,2 Fig. 3), including references of abovementioned report (Hoffman,3 Fig. 1; Rudiger et al,4 Fig. 3). Thus, it is not probable to explain the perfect flat line in our report with inadvertent electrode placement. A perfect flat line should bring probability of a disconnection error (or short circuit) into consideration, stemming from device itself. Moreover, it is not possible to explain second ECG (Fig. 2) with taking lead III as only normal reference lead, which is stated by the author, too. Fig. 2, beyond an assumption, is the real second ECG of the patient, and QRS morphology in limb leads is consistent with successive ECGs, derived from the same patient. Double, even triple, interconnection error cannot explain the difference between these 2 ECGs; this is already what makes this case interesting. The problem in this ECG is not misconnection, but disconnection problem probably arising from inside of the ECG machine. It can be easily seen that only similarity between these 2 ECGs, excluding precordial leads, is lead I. It is also not possible to record such an ECG with any combination of electrodes when lead I is correctly placed. Here, ECG was correctly recorded, but the device did not process lead II because of an internal error. Some ECG devices record 2 limb leads and compute the other ones, as pointed out before.5 Electrocardiogram devices using this method are inevitably obliged to use a 6 + 6 lead design, so they can print all limb leads simultaneously. The ECG machine in Fig. 1 in our report is such a device. Another interesting point to note is as the following; this device does not allow taking an ECG even with only one disconnected electrode. Thus, disconnection or short circuit is probably in the device itself. Electrocardiogram fans know very well how much information an ECG can give. Here, ECG warns clinicians about disconnection and leads the electric technician to look for a possible internal device disorder. Lastly, there is a more definitive and simple resolution for this issue. After the reported case, we tried to reproduce this artifact in a controlled situation with correct lead placement. An example for this and its control with a different device is
Letters to the Editor / Journal of Electrocardiology 43 (2010) 682–685
Fig. 1. An inadvertent interchange between right arm and right leg.
Fig. 2. Another artifact with the same ECG machine with correctly placed electrodes.
683
684
Letters to the Editor / Journal of Electrocardiology 43 (2010) 682–685
Fig. 3. Control ECG of Fig. 2 with a different ECG machine.
shown in Figs. 2 and 3. The device was repaired recently, and no more similar artifacts could be recorded. Hence, (1) the appearances are not those of inadvertent interchange between the right arm and right leg connections, as the author stated, and (2) “lead II was evidently disconnected” is a correct interpretation of our ECG findings. However, “evidently” can be considered an expression of underestimation after all and it would be better to be removed. We wish that these explanations would make the original report clearer and could answer the questions of the author. Emre Aslanger, MD Istanbul Faculty of Medicine Capa-Istanbul, Turkey E-mail address: [email protected] doi:10.1016/j.jelectrocard.2010.04.010
References 1. Rowlands DJ. Inadvertent interchange of electrocardiogram limb lead connections. Analysis of predicted consequences. J Electrocardiology 2008;41:84. 2. Batchvarov VN, Malik M, Camm AJ. Incorrect electrode cable connection during electrocardiographic recording. Europace 2007;9:1081. 3. Hoffman I. A flat line electrocardiogram in lead II is a marker for right arm/right leg electrode switch. J Electrocardiol 2007;40:226. 4. Rudiger A, et al. Electrocardiographic artifacts due to electrode misplacement and their frequency in different clinical settings. Am J Emerg Med 2007;25:174.
5. Drew BJ. Pitfalls and artifacts in electrocardiography. Cardiol Clin 2006;24:309.
An example of apparently normal electrocardiogram originating from incorrect electrocardiographic acquisition in a patient with ST-segment elevation myocardial infarction: Aslanger et al A valuable lesson and a clarification but still a puzzle. Author’s reply To the Editor, I was delighted to read the carefully considered reply from Aslanger et al to my earlier letter commenting on their article “An example of apparently normal electrocardiogram originating from incorrect electrocardiographic acquisition in a patient with ST-segment elevation myocardial infarction.”1 The authors have clarified the outstanding issues. In this case, there clearly was a hardware fault, giving rise to the recording problem in the original electrocardiogram. Such faults are, of course, very much less common than the inadvertent lead interchange, which I had surmised might (and substantially would) account for the appearances in their Fig. 1. The authors are absolutely correct, however, in pointing out that when there is a “flat line” during the recording of the limb leads (in lead II or lead III), close inspection of a high-quality recording will usually reveal very tiny, transient deflections synchronous with the QRS complexes in other leads. I recognize that when such