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Computed bipolar precordial leads for improved P wave detection
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ScienceDirect Journal of Electrocardiology 48 (2015) 188 – 189 www.jecgonline.com
Computed bipolar precordial leads for improved P wave detection☆ Velislav N. Batchvarov, MD,⁎ Elijah R. Behr, MD Cardiovascular and Cell Sciences Research Institute, St. George's University of London, London, United Kingdom
Abstract
We present an excerpt from a 24-hour 12-lead Holter recording acquired in an 85-year-old man investigated for the Brugada syndrome. The rhythm cannot be determined because no P waves can be discerned due to the high level of noise and to merging of the T and P waves. The P waves, however, are clearly visible and the noise is considerably reduced in bipolar precordial leads computed from the standard unipolar precordial leads. The case demonstrates the potential usefulness of various computed leads for rhythm analysis by detecting P waves that are not visible in the standard leads. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Electrocardiography; P wave; Unipolar leads; Computed bipolar leads; precordial leads
Case presentation We present an excerpt from a 24-hour ambulatory 12 lead Holter recording acquired in a 85-year-old man investigated for the Brugada syndrome (BrS) because of family history of BrS and conduction disease. The patient had no previous arrhythmia-related symptoms but on genetic analysis was discovered to carry the familial SCN5A mutation. His resting ECG (not shown) was unremarkable except for mild prolongation of the PR interval up to 260 ms and a nonspecific QRS prolongation of 120 ms. In accordance with our standard protocol for Holter investigation in the BrS, leads V1 and V2 from the 3rd intercostal (i.c.) space (leads V1 high and V2 high) were recorded instead of leads V5 and V6, respectively. The other four precordial leads were recorded from their standard positions. In the ECG on Fig. 1A, which presents the standard 12 leads (with leads V1 high and V2 high instead of leads V5 and V6) the rhythm cannot be determined due to considerable noise. The P waves, however, are clearly seen in several bipolar leads computed from leads V1, V3, V4, and V1 high (Fig. 1B). These include leads V1-3 (potential difference between the V1 and V3 electrodes), V1-4 (potential difference between V1 and V4) with a positive pole in both leads at V1, V3-1 high (positive pole at V3) and V4-1 high (positive pole at V4) (Fig. 1B). These leads were computed from the respective precordial unipolar leads by simple subtraction (e.g. lead V1-3 = lead V1 − lead V3, etc.) ☆
None of the authors has any conflict of interest to declare in relation to the manuscript. ⁎ Corresponding author at: St. George's University of London, Cranmer Terrace, London SW17 0RE, United Kingdom. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2014.12.009 0022-0736/© 2015 Elsevier Inc. All rights reserved.
[1], with the help of a custom-made software program. The computed leads are substantially less noisy than the unipolar leads due to noise cancellation [1,2] (since the noise in this case originates mainly from the right arm cable or electrode and is equally transmitted to all precordial leads via Wilson's central terminal) and allow measurement of the main ECG intervals with sufficient accuracy for clinical purposes (Fig. 1B). Two other computed bipolar leads (V1-2 and V3-2 high, not shown) also displayed clear P waves and reduced noise level; however, the P waves were most clearly seen on the bipolar leads presented on Fig. 1B. The P wave negativity in leads V1-3 and V1-4 and positivity in V3-1 high and V4-1 high indicate main direction of atrial depolarisation leftwards and downwards which suggests sinus rhythm. As we have previously reported [1–3] various bipolar and multipolar leads can be computed easily from the standard 12-lead ECG (provided the digital ECG signal is available) and can provide clinically valuable information which is not clearly visible or is invisible in the standard leads used for their computation. This is not only due to removal of noise but also to inherent properties of the bipolar leads. In intracardiac electrophysiology, bipolar leads obtained by subtraction of two closely spaced unipolar leads are used for detection of local electrical events (e.g. fractionation). Such a bipolar lead to some extent resembles the first derivative (that is, the rate of change or steepness of the slope) of the unipolar leads. A slight change in the slope of the ascending or descending limb of the QRS or T wave is usually undetectable to the naked eye; however, this change is marked as a clear peak (whether negative or positive) on the “derivative ECG”. The case demonstrates the potential clinical utility of the
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Fig. 1. A: All standard 12 leads (with leads V1high and V2high instead of leads V5 and V6, respectively) are presented in the usual order. No P waves can be seen in any lead due to both T-P merging and to high noise level. On both figures, the ECG is displayed at 25 mm/second, 1 cm/mV.B: Leads V1, V3, V4 and V1high followed by the bipolar leads V1-3, V1-4, V3-1high and V4-1high are presented. Note that in all four computed leads the noise level is considerably reduced, the P waves are clearly seen and the measurement of the main ECG intervals is possible with sufficient accuracy for clinical purposes. See the text for details.
bipolar leads for improved rhythm analysis which often critically depends on the detection and assessment of the P waves. Although the standard 12-lead ECG criteria for normal P wave morphology and polarity cannot, of course, be applied to various derived bipolar or multipolar precordial leads, the latter also are amenable to simple electrocardiographic vector analysis.
References [1] Batchvarov VN, Behr ER. Clinical utility of computed electrocardiographic leads. J Electrocardiol 2014;47:281–7. [2] Batchvarov VN, Behr ER. Derived bipolar precordial leads for noise filtering. J Electrocardiol 2010;43:660–2. [3] Batchvarov VN, Govindan M, Macfarlane P, Camm AJ, Behr E. Diagnostic utility of bipolar precordial leads during ajmaline testing for suspected Brugada syndrome. Heart Rhythm 2010;7:208–15.
ScienceDirect Journal of Electrocardiology 48 (2015) 188 – 189 www.jecgonline.com
Computed bipolar precordial leads for improved P wave detection☆ Velislav N. Batchvarov, MD,⁎ Elijah R. Behr, MD Cardiovascular and Cell Sciences Research Institute, St. George's University of London, London, United Kingdom
Abstract
We present an excerpt from a 24-hour 12-lead Holter recording acquired in an 85-year-old man investigated for the Brugada syndrome. The rhythm cannot be determined because no P waves can be discerned due to the high level of noise and to merging of the T and P waves. The P waves, however, are clearly visible and the noise is considerably reduced in bipolar precordial leads computed from the standard unipolar precordial leads. The case demonstrates the potential usefulness of various computed leads for rhythm analysis by detecting P waves that are not visible in the standard leads. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Electrocardiography; P wave; Unipolar leads; Computed bipolar leads; precordial leads
Case presentation We present an excerpt from a 24-hour ambulatory 12 lead Holter recording acquired in a 85-year-old man investigated for the Brugada syndrome (BrS) because of family history of BrS and conduction disease. The patient had no previous arrhythmia-related symptoms but on genetic analysis was discovered to carry the familial SCN5A mutation. His resting ECG (not shown) was unremarkable except for mild prolongation of the PR interval up to 260 ms and a nonspecific QRS prolongation of 120 ms. In accordance with our standard protocol for Holter investigation in the BrS, leads V1 and V2 from the 3rd intercostal (i.c.) space (leads V1 high and V2 high) were recorded instead of leads V5 and V6, respectively. The other four precordial leads were recorded from their standard positions. In the ECG on Fig. 1A, which presents the standard 12 leads (with leads V1 high and V2 high instead of leads V5 and V6) the rhythm cannot be determined due to considerable noise. The P waves, however, are clearly seen in several bipolar leads computed from leads V1, V3, V4, and V1 high (Fig. 1B). These include leads V1-3 (potential difference between the V1 and V3 electrodes), V1-4 (potential difference between V1 and V4) with a positive pole in both leads at V1, V3-1 high (positive pole at V3) and V4-1 high (positive pole at V4) (Fig. 1B). These leads were computed from the respective precordial unipolar leads by simple subtraction (e.g. lead V1-3 = lead V1 − lead V3, etc.) ☆
None of the authors has any conflict of interest to declare in relation to the manuscript. ⁎ Corresponding author at: St. George's University of London, Cranmer Terrace, London SW17 0RE, United Kingdom. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2014.12.009 0022-0736/© 2015 Elsevier Inc. All rights reserved.
[1], with the help of a custom-made software program. The computed leads are substantially less noisy than the unipolar leads due to noise cancellation [1,2] (since the noise in this case originates mainly from the right arm cable or electrode and is equally transmitted to all precordial leads via Wilson's central terminal) and allow measurement of the main ECG intervals with sufficient accuracy for clinical purposes (Fig. 1B). Two other computed bipolar leads (V1-2 and V3-2 high, not shown) also displayed clear P waves and reduced noise level; however, the P waves were most clearly seen on the bipolar leads presented on Fig. 1B. The P wave negativity in leads V1-3 and V1-4 and positivity in V3-1 high and V4-1 high indicate main direction of atrial depolarisation leftwards and downwards which suggests sinus rhythm. As we have previously reported [1–3] various bipolar and multipolar leads can be computed easily from the standard 12-lead ECG (provided the digital ECG signal is available) and can provide clinically valuable information which is not clearly visible or is invisible in the standard leads used for their computation. This is not only due to removal of noise but also to inherent properties of the bipolar leads. In intracardiac electrophysiology, bipolar leads obtained by subtraction of two closely spaced unipolar leads are used for detection of local electrical events (e.g. fractionation). Such a bipolar lead to some extent resembles the first derivative (that is, the rate of change or steepness of the slope) of the unipolar leads. A slight change in the slope of the ascending or descending limb of the QRS or T wave is usually undetectable to the naked eye; however, this change is marked as a clear peak (whether negative or positive) on the “derivative ECG”. The case demonstrates the potential clinical utility of the
V.N. Batchvarov, E.R. Behr / Journal of Electrocardiology 48 (2015) 188–189
189
Fig. 1. A: All standard 12 leads (with leads V1high and V2high instead of leads V5 and V6, respectively) are presented in the usual order. No P waves can be seen in any lead due to both T-P merging and to high noise level. On both figures, the ECG is displayed at 25 mm/second, 1 cm/mV.B: Leads V1, V3, V4 and V1high followed by the bipolar leads V1-3, V1-4, V3-1high and V4-1high are presented. Note that in all four computed leads the noise level is considerably reduced, the P waves are clearly seen and the measurement of the main ECG intervals is possible with sufficient accuracy for clinical purposes. See the text for details.
bipolar leads for improved rhythm analysis which often critically depends on the detection and assessment of the P waves. Although the standard 12-lead ECG criteria for normal P wave morphology and polarity cannot, of course, be applied to various derived bipolar or multipolar precordial leads, the latter also are amenable to simple electrocardiographic vector analysis.
References [1] Batchvarov VN, Behr ER. Clinical utility of computed electrocardiographic leads. J Electrocardiol 2014;47:281–7. [2] Batchvarov VN, Behr ER. Derived bipolar precordial leads for noise filtering. J Electrocardiol 2010;43:660–2. [3] Batchvarov VN, Govindan M, Macfarlane P, Camm AJ, Behr E. Diagnostic utility of bipolar precordial leads during ajmaline testing for suspected Brugada syndrome. Heart Rhythm 2010;7:208–15.