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Simulation of the QRS complex using papillary muscles positions as the site of early activation: first QRS simulation in human subjects
Available online at www.sciencedirect.com
Journal of Electrocardiology 42 (2009) 614 – 621 www.jecgonline.com
Poster Session 2
Performance of an ST-dipole vector model for description of ST deviations in occlusive myocardial ischemia M.P. Andersen,a C.J. Terkelsen,b J.T. Sørensen,b J.J. Struijk,a ( aDepartment of Health Science and Technology, Aalborg University, Aalborg, Denmark; b Department of Cardiology, Skejby University Hospital, Århus, Denmark) Background: ST-deviation analysis is a cornerstone in the early triage of myocardial ischemia. The current electrocardiogram (ECG) criteria for the diagnosis of occlusive myocardial ischemia focus on ST elevations, but recent studies have proposed to include both ST depression and ST elevation in the diagnosis, hence considering all ST deviations as projections of a single underlying dipole source. In this study, we examined to which extent a dipole ST vector model accounts for the measured ST deviations in acute ischemia patients. Methods: Forty-five patients with acute myocardial infarction were selected retrospectively for the study to have an equal representation of occlusion sites among the 3 major coronary arteries left anterior descending (LAD), right coronary artery (RCA), and left circumflex (LCX). A 12-lead ECG was recorded from each patient immediately before coronary intervention. All patients showed occlusive single-vessel disease with thrombolysis in myocardial infarction (TIMI) flow 0/1 (15 LAD, 15 RCA, 15 LCX). ST deviations were measured 60 milliseconds after the J-point in all leads using the 12SL algorithm. Three-dimensional lead vectors for each of the 12 standard leads were defined in accordance with the spatial direction of the leads in the frontal and horizontal planes. The dipole model was established by considering ST deviations as projections of a single-dipole vector onto each of the defined lead vectors. For each recorded ECG, the best-fitting dipole vector was estimated by minimizing the sum of squared errors between measured and projected ST deviations across all leads. Overall goodness-of-fit (R2) for the dipole model was evaluated between measured and projected ST deviations across all recordings. Results: The goodness-of-fit across all recordings was R2 = 0.82-0.87 (95% confidence interval [CI]). When examining recordings grouped by culprit artery, the model fit was R2 = 0.75-0.85 (95% CI) for the LAD occlusions, R2 = 0.83-0.90 (95% CI) for the RCA recordings, and R2 = 0.78-0.87 (95% CI), for the LCX recordings. Analysis of variance showed no significant difference in goodness-of-fit for the different occlusion sites (P = .19). Conclusion: The single-dipole ST vector accounted for approximately 85% of the ST-deviation information in the studied ECG recordings irrespective of the site of occlusion. A simple dipole model may be a useful descriptor of ST-segment deviations, reducing ST-deviation measurements from 12 leads to a single 3-dimensional vector.
time. This consists of a patient applied real-time analyzer (Philips IntelliPatch Philips, Eindhoven, NL), which includes extensive noise reduction and detection hardware and software. The ECG obtained is a “short vector” ECG with 3 sensing electrodes whose centers lie at the corners of a 1.5-in equilateral triangle. Upon automatic alarm trigger, the device sends surrounding ECG data to a central monitor immediately for confirmation. The suitability of this shorter ECG vector for such analysis was studied. Methods: The Complete Capture Event Recorder Trial was designed to capture a sufficient variety of ECG rhythms, using prototype IntelliPatch devices, to characterize the IntelliPatch ECG lead vectors in comparison to a simultaneously recorded standard, commercially available Holter monitor lead set. Each 24-hour pair of records was resampled to 200 sps and aligned to within a few samples. The first 35 minutes of 52 cases were selected for concordance testing. The first 5 minutes of each case was designated as a “learning phase” for the algorithm, and concordance was evaluated over the remaining 30 minutes. A database of reference annotations was developed for each case using only the Holter ECG data as the standard. These manually reviewed and corrected reference annotations were then used to score algorithm performance for both long-vector and short-vector ECG data. Results: The short vector contains more local information at lower amplitude, so it was scaled up to compensate (×4). Although advanced electrode technology was used reducing noise, this scaling increases the noise content. The short-vector QRS positive predictivity was virtually identical to the long-vector version, whereas the QRS sensitivity was slightly reduced:
Short vector versus database Statistics as if only 1 record Averaged statistics from records Long vector versus database Statistics as if only 1 record Averaged statistics from records
Q Se
Q+P
98.54 98.56
99.78 99.74
99.77 99.78
99.80 99.78
Conclusions: The short vector (despite additional noise) showed extraordinary QRS detection accuracy equivalent to the traditional long vector. The short vector fully supports accurate heart rate alarms.
doi:10.1016/j.jelectrocard.2009.08.028
doi:10.1016/j.jelectrocard.2009.08.027
Automated performance analysis of short-vector versus long-vector electrocardiograms Dirk Q. Feild,a Stacy Gehman,b ( aAdvanced Algorithm Research Center, Philips Healthcare, Thousand Oaks, CA USA; bPhilips Healthcare, Seattle, WA, USA) Background: A novel recording device has been developed to continuously record 3 channels of electrocardiogram (ECG) for more than 24 hours at a 0022-0736/$ – see front matter
Simulation of the QRS complex using papillary muscles positions as the site of early activation: first QRS simulation in human subjects Nina Hakacova,a Geoffrey D. Bass,b Charles W. Olson,c Anna M.C. Robinson,d Ronald Selvester,e Galen S. Wagner, f ( aChildren's Cardiac Centre, Bratislava, Slovakia, EU; bDuke University, Faculty of Medicine, Durham, North Carolina, USA; cECG-TECH Corp. Huntington, New York, USA; dGlasgow Magnetic Resonance Unit, Glasgow, UK; eMemorial Hospital Research Center, La Jolla, CA, USA; fDuke University Medical Centre, Durham, North Carolina, USA)
Poster Session 2 / Journal of Electrocardiology 42 (2009) 614–621 Background: Simulation of electrical activation of the heart and its comparison with real activation is a promising method in testing potential determinants of excitation events in the heart. The need for simulation of the electrical activity of the human heart is now emerging as a step forward for understanding and predicting electrophysiological patterns in humans. Initial points of excitation and the manner in which the activation spreads from these points are important variables determining QRS complex characteristics. It was suggested that in humans, the initial excitation of the left ventricle is primary determinant of QRS complex characteristics, and it begins at the papillary muscles and septum, where the fascicles of the left bundle branch insert. The aim of this study is to test the hypothesis that QRS duration and direction of QRS axis in the frontal plane has excellent agreement between real QRS and simulated QRS using papillary muscle position as the origin of early ventricular activation. Methods: Fourteen healthy adult volunteers were included in the study. Magnetic resonance imaging (MRI) data were obtained to assess the papillary muscle positions. 12-Lead electrocardiographic (ECG) recordings were used to obtain real ECG for assessment of QRS duration and QRS axis in each subject. Simulation software developed by ECG-TECH Corp was used to simulate ECG of each subject and assess simulated QRS duration and QRS axis. Agreement between real and simulated QRS duration and QRS axis was calculated. Results: Seventy-nine percent of subjects had difference of the QRS duration between real and simulated ECG of less than 10 milliseconds. The calculated strength of agreement between simulated and real QRS duration was 71% and considered as ‘good’ (kappa statistics). In 70% of subjects, the difference in the QRS axis was less than 10 degrees. The calculated strength of agreement between simulated and real QRS axis was 80% and considered as ‘excellent’ (kappa statistics). Conclusions: The results suggest the sites of the initiation of electrical activity in the left ventricle, as assessed by the positions of papillary muscles, may be considered as primary determinants of the QRS duration and QRS axis in the humans. This knowledge may help in predicting normal QRS characteristic on a patient-specific basis. This is the first study where simulation of the QRS complex was based on anatomical data from the human hearts. doi:10.1016/j.jelectrocard.2009.08.029
Evaluation of a new modified chest lead in diagnosing wide-complex beats of unknown origin Mark A. Kossick,a Neal Kay, MD,b Michael Carter, DNSc,c James Pruett, PhD,d Linda Hill, DNP,d ( aDNSc, Union University, Jackson, TN, USA; b University of Alabama at Birmingham, Birmingham, AL, USA; cUniversity of Tennessee Memphis Health Science Center, Memphis, TN, USA; dUniUniversity of Tennessee Chattanooga, Chattanooga, TN, USA) Background: Electrocardiographic (ECG) lead configuration of modified chest leads (MCL) remains problematic for many health care providers. The consequences include potential iatrogenic injury to patients. Development of a new MCL that incorporates a unipolar limb lead (instead of a bipolar limb lead system) could potentially reduce configuration errors. Such a lead would need to be investigated for diagnostic accuracy before being examined for ease of configuration relative to MCL1. Methods: A prospective observational study of 8 adults undergoing electrophysiologic study for ablation therapy was performed to compare a new MCL (modified augmented chest lead 1 left arm [MAC1L]) to V1 for its ability to distinguish aberrantly conducted beats from ventricular ectopy. Subjects were connected to 2 monitors, which displayed continuous V1 and MAC1L recordings. The monitor used to display MAC1L was configured via a 5-lead wire-cable system with the right arm, right leg, and left leg electrodes placed in their traditional locations and both the left arm and chest electrodes aligned in the V1 position. Lead aVL was selected to complete the configuration. The His bundle electrogram was used as the criterion standard to determine the site of origin for anamolus beats. Electrocardiogram data were recorded onto an optical disk system and interpreted by 3 cardiologists (years of clinical experience ranged from 1.5 to 13.5 years) who were blinded to patient demographic data and the identity of the ECG leads. These interpreters diagnosed the recorded ectopy
615
as being supraventricular, ventricular, or indeterminate using wellestablished diagnostic QRS patterns. Results: A total of 47 ectopic events (QRS complexes N120-ms duration) recorded simultaneously in 2 ECG leads were available for analysis, of which only 1 represented aberrant ventricular conduction. For all 3 interpreters combined, the proportion of ectopy correctly diagnosed with V1 was 0.73 and with MAC1L 0.68. A proportions test showed no statistically significant difference (α level of .05) in the diagnostic accuracy between V1 and MAC1L. Overall, the appearance of wide-complex beats judged to be identical or nearly identical by the 3 interpreters ranged from 78% to 93%. Conclusions: Due to the limited number of aberrantly conducted beats (n = 1), it is not possible to assess the potential value of MAC1L in distinguishing aberrancy from ventricular ectopy. Sufficient data were available to demonstrate ventricular ectopy recorded in MAC1L are commonly rated as being nearly identical in appearance to what is observed in V1. doi:10.1016/j.jelectrocard.2009.08.030
The electrocardiogram vector basis for location of the bypass tracts in Wolf-Parkinson-White M.M. Laks, MD, (Harbor-UCLA Medical Center, Torrance, CA, USA) Many studies have been published that have created complex and confusing algorithms for the location of bypass tracts. No study has used the National Institutes of Health Visible Human Project Slices of the Heart as improved by David Criley to relate the electrocardiogram (ECG) delta wave vector (Δ) to cardiac anatomy. From the study of Kilpatrick and Scheinman (1994), the localization of the bypass tract algorithms were converted into ECG vectors and superimposed on the frontal and horizontal plane of the National Institutes of Health Visible Human Project Slices of the Heart. The location of the bypass tract ventricular wall is determined by plotting the mean QRS axis from the precordial leads (horizontal plane). Ventricular-wall bypass-tract locations—horizontal plane leads: R: (right ventricle) if QRS axes ≥−30° or − (14°-29°) + R N S in II and Δ b 1 mV S: (ventricular septum) if QRS axes ≥−(1°-15°) or 0-29° + R N S in I by N 1 mV or −(14°-29°) + R N S in II and Δ N1 mV L: (left ventricle) if QRS axes ≥30° or 0°-29° + R N S in I by b1 mV In the horizontal plane as relates to the chest wall, the ventricular anatomy demonstrates that the origin of the Δ at the base of the left ventricle is posterior with Δ directed anterior and of the right ventricle is anterior with Δ directed posterior. The septum is in between. From these relationships, a simplified terminology system is presented below. Bypass tract locations—frontal plane leads: RS: (right ventricle anteriolateral) if FPΔ 0°-60° or QRS III N 0 mV SS: (septal ventricle anteroseptal) if FPΔ 30°-90° SM: (septum mid) if FPΔ 0° -29° LS: (left ventricle anterolateral) if FPΔ ≥ 30° or QRS N 60° LM: (left ventricle posterolateral) if FPΔ 0° to +29° or QRS 0°-90° {R N S in I by ≦0.8 mV RI: (right ventricle posterolateral) if FPΔ 330°-359° SI: (septum posteroseptal) if FPΔ 270°-330° SM: (septum mid) if FPΔ 331°-359° LI: (posteroseptal) if FPΔ 271°-359° ( ) = Scheinman terminology First letter: R = right ventricle; S = septum; L = left ventricle Second letter: S = superior; M = mid; I = inferior In the frontal plane as relates to a person sitting up, cardiac anatomy highlights the origin of the delta vector locations on the superior, middle and inferior walls. Summary: The above simple bypass tract terminology best relates to the anatomy of the chest wall to a person sitting up and to the images seen on the vertical fluoroscopic screen during electrophysiology studies. Anterior is more superior, and posterior is more inferior.
Journal of Electrocardiology 42 (2009) 614 – 621 www.jecgonline.com
Poster Session 2
Performance of an ST-dipole vector model for description of ST deviations in occlusive myocardial ischemia M.P. Andersen,a C.J. Terkelsen,b J.T. Sørensen,b J.J. Struijk,a ( aDepartment of Health Science and Technology, Aalborg University, Aalborg, Denmark; b Department of Cardiology, Skejby University Hospital, Århus, Denmark) Background: ST-deviation analysis is a cornerstone in the early triage of myocardial ischemia. The current electrocardiogram (ECG) criteria for the diagnosis of occlusive myocardial ischemia focus on ST elevations, but recent studies have proposed to include both ST depression and ST elevation in the diagnosis, hence considering all ST deviations as projections of a single underlying dipole source. In this study, we examined to which extent a dipole ST vector model accounts for the measured ST deviations in acute ischemia patients. Methods: Forty-five patients with acute myocardial infarction were selected retrospectively for the study to have an equal representation of occlusion sites among the 3 major coronary arteries left anterior descending (LAD), right coronary artery (RCA), and left circumflex (LCX). A 12-lead ECG was recorded from each patient immediately before coronary intervention. All patients showed occlusive single-vessel disease with thrombolysis in myocardial infarction (TIMI) flow 0/1 (15 LAD, 15 RCA, 15 LCX). ST deviations were measured 60 milliseconds after the J-point in all leads using the 12SL algorithm. Three-dimensional lead vectors for each of the 12 standard leads were defined in accordance with the spatial direction of the leads in the frontal and horizontal planes. The dipole model was established by considering ST deviations as projections of a single-dipole vector onto each of the defined lead vectors. For each recorded ECG, the best-fitting dipole vector was estimated by minimizing the sum of squared errors between measured and projected ST deviations across all leads. Overall goodness-of-fit (R2) for the dipole model was evaluated between measured and projected ST deviations across all recordings. Results: The goodness-of-fit across all recordings was R2 = 0.82-0.87 (95% confidence interval [CI]). When examining recordings grouped by culprit artery, the model fit was R2 = 0.75-0.85 (95% CI) for the LAD occlusions, R2 = 0.83-0.90 (95% CI) for the RCA recordings, and R2 = 0.78-0.87 (95% CI), for the LCX recordings. Analysis of variance showed no significant difference in goodness-of-fit for the different occlusion sites (P = .19). Conclusion: The single-dipole ST vector accounted for approximately 85% of the ST-deviation information in the studied ECG recordings irrespective of the site of occlusion. A simple dipole model may be a useful descriptor of ST-segment deviations, reducing ST-deviation measurements from 12 leads to a single 3-dimensional vector.
time. This consists of a patient applied real-time analyzer (Philips IntelliPatch Philips, Eindhoven, NL), which includes extensive noise reduction and detection hardware and software. The ECG obtained is a “short vector” ECG with 3 sensing electrodes whose centers lie at the corners of a 1.5-in equilateral triangle. Upon automatic alarm trigger, the device sends surrounding ECG data to a central monitor immediately for confirmation. The suitability of this shorter ECG vector for such analysis was studied. Methods: The Complete Capture Event Recorder Trial was designed to capture a sufficient variety of ECG rhythms, using prototype IntelliPatch devices, to characterize the IntelliPatch ECG lead vectors in comparison to a simultaneously recorded standard, commercially available Holter monitor lead set. Each 24-hour pair of records was resampled to 200 sps and aligned to within a few samples. The first 35 minutes of 52 cases were selected for concordance testing. The first 5 minutes of each case was designated as a “learning phase” for the algorithm, and concordance was evaluated over the remaining 30 minutes. A database of reference annotations was developed for each case using only the Holter ECG data as the standard. These manually reviewed and corrected reference annotations were then used to score algorithm performance for both long-vector and short-vector ECG data. Results: The short vector contains more local information at lower amplitude, so it was scaled up to compensate (×4). Although advanced electrode technology was used reducing noise, this scaling increases the noise content. The short-vector QRS positive predictivity was virtually identical to the long-vector version, whereas the QRS sensitivity was slightly reduced:
Short vector versus database Statistics as if only 1 record Averaged statistics from records Long vector versus database Statistics as if only 1 record Averaged statistics from records
Q Se
Q+P
98.54 98.56
99.78 99.74
99.77 99.78
99.80 99.78
Conclusions: The short vector (despite additional noise) showed extraordinary QRS detection accuracy equivalent to the traditional long vector. The short vector fully supports accurate heart rate alarms.
doi:10.1016/j.jelectrocard.2009.08.028
doi:10.1016/j.jelectrocard.2009.08.027
Automated performance analysis of short-vector versus long-vector electrocardiograms Dirk Q. Feild,a Stacy Gehman,b ( aAdvanced Algorithm Research Center, Philips Healthcare, Thousand Oaks, CA USA; bPhilips Healthcare, Seattle, WA, USA) Background: A novel recording device has been developed to continuously record 3 channels of electrocardiogram (ECG) for more than 24 hours at a 0022-0736/$ – see front matter
Simulation of the QRS complex using papillary muscles positions as the site of early activation: first QRS simulation in human subjects Nina Hakacova,a Geoffrey D. Bass,b Charles W. Olson,c Anna M.C. Robinson,d Ronald Selvester,e Galen S. Wagner, f ( aChildren's Cardiac Centre, Bratislava, Slovakia, EU; bDuke University, Faculty of Medicine, Durham, North Carolina, USA; cECG-TECH Corp. Huntington, New York, USA; dGlasgow Magnetic Resonance Unit, Glasgow, UK; eMemorial Hospital Research Center, La Jolla, CA, USA; fDuke University Medical Centre, Durham, North Carolina, USA)
Poster Session 2 / Journal of Electrocardiology 42 (2009) 614–621 Background: Simulation of electrical activation of the heart and its comparison with real activation is a promising method in testing potential determinants of excitation events in the heart. The need for simulation of the electrical activity of the human heart is now emerging as a step forward for understanding and predicting electrophysiological patterns in humans. Initial points of excitation and the manner in which the activation spreads from these points are important variables determining QRS complex characteristics. It was suggested that in humans, the initial excitation of the left ventricle is primary determinant of QRS complex characteristics, and it begins at the papillary muscles and septum, where the fascicles of the left bundle branch insert. The aim of this study is to test the hypothesis that QRS duration and direction of QRS axis in the frontal plane has excellent agreement between real QRS and simulated QRS using papillary muscle position as the origin of early ventricular activation. Methods: Fourteen healthy adult volunteers were included in the study. Magnetic resonance imaging (MRI) data were obtained to assess the papillary muscle positions. 12-Lead electrocardiographic (ECG) recordings were used to obtain real ECG for assessment of QRS duration and QRS axis in each subject. Simulation software developed by ECG-TECH Corp was used to simulate ECG of each subject and assess simulated QRS duration and QRS axis. Agreement between real and simulated QRS duration and QRS axis was calculated. Results: Seventy-nine percent of subjects had difference of the QRS duration between real and simulated ECG of less than 10 milliseconds. The calculated strength of agreement between simulated and real QRS duration was 71% and considered as ‘good’ (kappa statistics). In 70% of subjects, the difference in the QRS axis was less than 10 degrees. The calculated strength of agreement between simulated and real QRS axis was 80% and considered as ‘excellent’ (kappa statistics). Conclusions: The results suggest the sites of the initiation of electrical activity in the left ventricle, as assessed by the positions of papillary muscles, may be considered as primary determinants of the QRS duration and QRS axis in the humans. This knowledge may help in predicting normal QRS characteristic on a patient-specific basis. This is the first study where simulation of the QRS complex was based on anatomical data from the human hearts. doi:10.1016/j.jelectrocard.2009.08.029
Evaluation of a new modified chest lead in diagnosing wide-complex beats of unknown origin Mark A. Kossick,a Neal Kay, MD,b Michael Carter, DNSc,c James Pruett, PhD,d Linda Hill, DNP,d ( aDNSc, Union University, Jackson, TN, USA; b University of Alabama at Birmingham, Birmingham, AL, USA; cUniversity of Tennessee Memphis Health Science Center, Memphis, TN, USA; dUniUniversity of Tennessee Chattanooga, Chattanooga, TN, USA) Background: Electrocardiographic (ECG) lead configuration of modified chest leads (MCL) remains problematic for many health care providers. The consequences include potential iatrogenic injury to patients. Development of a new MCL that incorporates a unipolar limb lead (instead of a bipolar limb lead system) could potentially reduce configuration errors. Such a lead would need to be investigated for diagnostic accuracy before being examined for ease of configuration relative to MCL1. Methods: A prospective observational study of 8 adults undergoing electrophysiologic study for ablation therapy was performed to compare a new MCL (modified augmented chest lead 1 left arm [MAC1L]) to V1 for its ability to distinguish aberrantly conducted beats from ventricular ectopy. Subjects were connected to 2 monitors, which displayed continuous V1 and MAC1L recordings. The monitor used to display MAC1L was configured via a 5-lead wire-cable system with the right arm, right leg, and left leg electrodes placed in their traditional locations and both the left arm and chest electrodes aligned in the V1 position. Lead aVL was selected to complete the configuration. The His bundle electrogram was used as the criterion standard to determine the site of origin for anamolus beats. Electrocardiogram data were recorded onto an optical disk system and interpreted by 3 cardiologists (years of clinical experience ranged from 1.5 to 13.5 years) who were blinded to patient demographic data and the identity of the ECG leads. These interpreters diagnosed the recorded ectopy
615
as being supraventricular, ventricular, or indeterminate using wellestablished diagnostic QRS patterns. Results: A total of 47 ectopic events (QRS complexes N120-ms duration) recorded simultaneously in 2 ECG leads were available for analysis, of which only 1 represented aberrant ventricular conduction. For all 3 interpreters combined, the proportion of ectopy correctly diagnosed with V1 was 0.73 and with MAC1L 0.68. A proportions test showed no statistically significant difference (α level of .05) in the diagnostic accuracy between V1 and MAC1L. Overall, the appearance of wide-complex beats judged to be identical or nearly identical by the 3 interpreters ranged from 78% to 93%. Conclusions: Due to the limited number of aberrantly conducted beats (n = 1), it is not possible to assess the potential value of MAC1L in distinguishing aberrancy from ventricular ectopy. Sufficient data were available to demonstrate ventricular ectopy recorded in MAC1L are commonly rated as being nearly identical in appearance to what is observed in V1. doi:10.1016/j.jelectrocard.2009.08.030
The electrocardiogram vector basis for location of the bypass tracts in Wolf-Parkinson-White M.M. Laks, MD, (Harbor-UCLA Medical Center, Torrance, CA, USA) Many studies have been published that have created complex and confusing algorithms for the location of bypass tracts. No study has used the National Institutes of Health Visible Human Project Slices of the Heart as improved by David Criley to relate the electrocardiogram (ECG) delta wave vector (Δ) to cardiac anatomy. From the study of Kilpatrick and Scheinman (1994), the localization of the bypass tract algorithms were converted into ECG vectors and superimposed on the frontal and horizontal plane of the National Institutes of Health Visible Human Project Slices of the Heart. The location of the bypass tract ventricular wall is determined by plotting the mean QRS axis from the precordial leads (horizontal plane). Ventricular-wall bypass-tract locations—horizontal plane leads: R: (right ventricle) if QRS axes ≥−30° or − (14°-29°) + R N S in II and Δ b 1 mV S: (ventricular septum) if QRS axes ≥−(1°-15°) or 0-29° + R N S in I by N 1 mV or −(14°-29°) + R N S in II and Δ N1 mV L: (left ventricle) if QRS axes ≥30° or 0°-29° + R N S in I by b1 mV In the horizontal plane as relates to the chest wall, the ventricular anatomy demonstrates that the origin of the Δ at the base of the left ventricle is posterior with Δ directed anterior and of the right ventricle is anterior with Δ directed posterior. The septum is in between. From these relationships, a simplified terminology system is presented below. Bypass tract locations—frontal plane leads: RS: (right ventricle anteriolateral) if FPΔ 0°-60° or QRS III N 0 mV SS: (septal ventricle anteroseptal) if FPΔ 30°-90° SM: (septum mid) if FPΔ 0° -29° LS: (left ventricle anterolateral) if FPΔ ≥ 30° or QRS N 60° LM: (left ventricle posterolateral) if FPΔ 0° to +29° or QRS 0°-90° {R N S in I by ≦0.8 mV RI: (right ventricle posterolateral) if FPΔ 330°-359° SI: (septum posteroseptal) if FPΔ 270°-330° SM: (septum mid) if FPΔ 331°-359° LI: (posteroseptal) if FPΔ 271°-359° ( ) = Scheinman terminology First letter: R = right ventricle; S = septum; L = left ventricle Second letter: S = superior; M = mid; I = inferior In the frontal plane as relates to a person sitting up, cardiac anatomy highlights the origin of the delta vector locations on the superior, middle and inferior walls. Summary: The above simple bypass tract terminology best relates to the anatomy of the chest wall to a person sitting up and to the images seen on the vertical fluoroscopic screen during electrophysiology studies. Anterior is more superior, and posterior is more inferior.