Einthoven Triangle Research Articles

Einthoven's triangle adapted for horses: Proposal for the Delta configuration.

Reliable ECGs are crucial for diagnosing arrhythmias, yet a lack of standardization impedes arrhythmia diagnosis and treatment in horses. To objectively determine an optimal position of Einthoven's triangle for ECG recordings in horses at rest, which can form the basis for standardized ECG recording and improve diagnosis and treatment of arrhythmias. The study involved 72 healthy, warmblood horses aged between 3 and 20 years. In view of future 12-lead studies and vectorcardiography, requiring an orthogonal system, Einthoven's triangle was positioned around the heart, in the transverse plane. Therefore, 11 electrodes were placed encircling the thorax behind the olecranon, to construct triangles with a horizontal base. Electrocardiogram recordings from different triangles were analyzed. Signal processing involved filtering, R peak detection, and median complex generation. Principal component analysis (PCA) and Euclidean distance measures were employed for data analysis. The left mid-thoracic and ventral regions had high PCA scores, indicating high information content. Base-down triangles exhibited higher summed Euclidean distances, contributing to enhanced diagnostic capabilities. A base-down triangle, called "Delta (Δ) configuration" emerged as most informative, while meeting all criteria. The base-down "Delta configuration" is the optimal Einthoven's triangle adapted for horses, providing large amplitudes and potential to provide basic insights into the mechanisms and origins of cardiac arrhythmias. Because the Delta configuration is positioned in the transverse plane, it forms the ideal basis for 12-lead ECG recordings that provide vectorcardiograms in an orthogonal coordinate system. Standardizing electrode positioning could improve ECG data comparability in equine cardiology.

Miniaturized 3‐Lead Electrocardiogram System Based on Einthoven Triangle for Wireless Cardiac Care Monitoring

Monitoring heart health typically requires a 12‐lead electrocardiogram (ECG) system with a sampling frequency of ≥400 Hz with high power requirements. This allows the detection of clinically relevant cardiovascular events using P, Q, R, S, and T signature peaks in ECG. These requirements limit the scope of ECG use, especially in proactive monitoring, cardiac event prevention, and wireless wearable devices. Herein, a skin‐mountable 3‐lead wireless sensor patch based on the Einthoven triangle is experimentally demonstrated. It allows us to gather vital cardiac information in place of a conventional 12‐lead ECG system. The patch uses the industry's lowest‐power Bluetooth low‐energy system on chip which requires 50 Hz sampling frequency to detect all critical events. A firmware for the chip is developed to transmit data wirelessly at extremely low power (−19 dB), resulting in uninterrupted operation for ≈4 days using a simple CR1632 battery. An Android app records and plots ECG data on a smartphone for real‐time visual monitoring and transmits the data to the cloud‐connected interface for remote monitoring. The demonstration with low‐power operation and integration to the cloud‐connected interface is a significant step for nonassisted home‐based caring to enable preventive health management without being widely constrained by battery and tethered operation.

Signal Quality Analysis of Single-Arm Electrocardiography.

The number of people experiencing mental stress or emotional dysfunction has increased since the onset of the COVID-19 pandemic, as many individuals have had to adapt their daily lives. Numerous studies have demonstrated that mental health disorders can pose a risk for certain diseases, and they are also closely associated with the problem of mental workload. Now, wearable devices and mobile health applications are being utilized to monitor and assess individuals' mental health conditions on a daily basis using heart rate variability (HRV), typically measured by the R-to-R wave interval (RRI) of an electrocardiogram (ECG). However, portable or wearable ECG devices generally require two electrodes to perform bipolar limb leads, such as the Einthoven triangle. This study aims to develop a single-arm ECG measurement method, with lead I ECG serving as the gold standard. We conducted static and dynamic experiments to analyze the morphological performance and signal-to-noise ratio (SNR) of the single-arm ECG. Three morphological features were defined, RRI, the duration of the QRS complex wave, and the amplitude of the R wave. Thirty subjects participated in this study. The results indicated that RRI exhibited the highest cross-correlation (R = 0.9942) between the single-arm ECG and lead I ECG, while the duration of the QRS complex wave showed the weakest cross-correlation (R = 0.2201). The best SNR obtained was 26.1 ± 5.9 dB during the resting experiment, whereas the worst SNR was 12.5 ± 5.1 dB during the raising and lowering of the arm along the z-axis. This single-arm ECG measurement method offers easier operation compared to traditional ECG measurement techniques, making it applicable for HRV measurement and the detection of an irregular RRI.

Capturing human-like digitalis effect and cardiotoxicity in adult zebrafish using in vivo dual-Einthoven-lead ECG and ex vivo epicardial optical mapping

In humans, twelve-lead electrocardiogram (ECG) is an indispensable, accurate, rapid, and economical method for clinical evaluation of “digitalis effect” (earliest, nontoxic ECG manifestations of adequate cardiac tissue absorption) and digitalis cardiotoxicity (suppressant effects, excitatory effects, and hyperkalemia). In adult zebrafish, for which the canonical ECG recording method employs single lead, digitalis effect and cardiotoxicity are largely unknown. Here we demonstrate the first application of in vivo dual-Einthoven-lead ECG and Einthoven's-triangle construction as a novel reproducible method to reveal that normal adult zebrafish acutely recapitulate most of human digitalis effect and cardiotoxicity (except QT shortening).

Sensitivity and Adjustment Model of Electrocardiographic Signal Distortion Based on the Electrodes' Location and Motion Artifacts Reduction for Wearable Monitoring Applications.

Wearable vital signs monitoring and specially the electrocardiogram have taken important role due to the information that provide about high-risk diseases, it has been evidenced by the needed to increase the health service coverage in home care as has been encouraged by World Health Organization. Some wearables devices have been developed to monitor the Electrocardiographic in which the location of the measurement electrodes is modified respect to the Einthoven model. However, mislocation of the electrodes on the torso can lead to the modification of acquired signals, diagnostic mistakes and misinterpretation of the information in the signal. This work presents a volume conductor evaluation and an Electrocardiographic signal waveform comparison when the location of electrodes is changed, to find a electrodes’ location that reduces distortion of interest signals. In addition, effects of motion artifacts and electrodes’ location on the signal acquisition are evaluated. A group of volunteers was recorded to obtain Electrocardiographic signals, the result was compared with a computational model of the heart behavior through the Ensemble Average Electrocardiographic, Dynamic Time Warping and Signal-to-Noise Ratio methods to quantitatively determine the signal distortion. It was found that while the Einthoven method is followed, it is possible to acquire the Electrocardiographic signal from the patient’s torso or back without a significant difference, and the electrodes position can be moved 6 at most from the suggested location by the Einthoven triangle in Mason–Likar’s method.

Constructing Einthoven's Triangle to Define Adult Zebrafish Cardiac Electrical Vectors and Evaluate Digitalis Effect vs Cardiotoxicity

Zebrafish heart has emerged as a popular high-throughput vertebrate model to study human cardiac electrophysiology, arrhythmias, and myopathies. One reason for this popularity is the purported striking similarities between zebrafish and human electrocardiograms (ECGs) despite their vast cardiac anatomical differences. Yet, the zebrafish heart electrical axis has not been determined and underlying electrical tissue mechanisms are incompletely understood. Therefore, for the first time, adult zebrafish Einthoven's triangle was systematically constructed, and zebrafish heart electrical axis in the frontal plane was determined using the Cabrera (or hexaxial reference) system. Additionally, zebrafish translatability was evaluated by defining how digitalis at therapeutic vs supratherapeutic doses modulate Einthoven's triangle. Comparing zebrafish and human Einthoven's triangles under baseline condition reveal that their ventricular activation propagated in opposite directions, indicating that their electrical axes are antiparallel. Their ventricular repolarization also propagated in opposite directions, accounting for their opposite QRS and T wave concordances. Moreover, digitalis modulation of zebrafish Einthoven's triangle recapitulated classic human ECG manifestations of the ‘digitalis effect’ at therapeutic dose and digitalis cardiotoxicity at supratherapeutic dose, but in mirror image along the main cardiac axis. These findings validate zebrafish Einthoven's triangle as a useful, sensitive, and clinically relevant diagnostic tool. This study is the first systematic analysis of the actual differences and similarities between normal adult zebrafish and human Einthoven's triangles to unmask differences and similarities in the underlying tissue mechanisms. These new insights provide additional, necessary contextual framework to properly interpret the clinical relevance of the adult zebrafish heart model for human cardiac electrophysiology and arrhythmia studies.

A portable electrocardiogram for real-time monitoring of cardiac signals

This study presents an electrocardiogram (ECG) monitoring and processing system which can observe subjects in real time and display the resultant ECG signals on a computer for observation. The primary application is for the remote observation of cardiac patients. This paper aims to determine its reliability by analysing its portability and wireless connectivity. The system is comprised of three principal units, namely the data acquisition circuit, where cardiac electrical signals are detected using three surface electrodes placed at three different positions on the chest wall to follow the Einthoven Triangle. The signals measured are amplified and filtered by components in a circuit and are then carried to a data processing unit where a ATmega328P microcontroller with a ZigBee interface module are used to transfer the biosignal wirelessly to the Graphical User Interface (GUI) unit which has the capacity to observe ECG biosignals on a computer. The results demonstrated that the design successfully produced a distortion-free signal, namely the hardware and software elements operated and intercommunicated correctly. In both LabVIEW and MATLAB configurations, the GUI characteristics were examined and found to yield unproblematic, user-friendly displays in real-time. Thus, this research provides a novel ECG system design to effectively analyse cardiac patients, however, it would be useful to develop a tool that can differentiate the various forms of cardiac arrhythmia.

The electrostatic foundation of the electrocardiogram

The electrocardiogram, or ECG, is the first diagnostic test for evaluating the health of the heart. Safe, fast, and noninvasive, it does not require previous preparation. The ECG is the graphic recording of the electrical activity of the heart and the variations that occur during cardiac contraction (systole) and relaxation (diastole) of the atria and ventricles during its operation, collected by means of electrodes placed above the body. It was introduced by Willem Einthoven and Etienne-Jules Marey at the beginning of the 20th century. While it was already known since early in the 19th century that every contraction of the heart was due to an electrical activity, it was only with Einthoven and Marey that the electrical activity of the heart was recorded in a quantitative manner, using a modified string galvanometer. Many of the conventions established by Einthoven hold still in the modern era, and form the basis for interpreting many aspects of the modern ECG. In particular, the Einthoven Triangle, which is an imaginary inverted equilateral triangle with the heart at the center, is still the core of the electrode arrangement.

A novel approach for non-invasive measurement of mean arterial pressure using pulse transit time

Recent days many researches are carried out related to the heart of the human. As a result many remedies are found for the various heart disorders. Electrocardiography (ECG) is the exertion of the electrical response from heart by placing the electrodes over the chest. The Einthoven triangle is an imaginary formation of the three leads in the triangle used in electrocardiography; by that technique of placement of electrode we can analysis the electrocardiogram of the heart. The waveform is also known as PQR waveform which contains the information of arterial repolarization, arterial polarization, ventricular repolarization and ventricular polarization. In general the BP monitor is carried out using oscillometry. In the existing system separate techniques and devices are used to measure electrocardiography and BP. The proposed system is to integrate both electrocardiography and blood pressure measurement by means adopting transit pulse time. It is defined as the systematic time lay off betwixt oscillometric pulses and peaks of ECG especially R peaks of it. The major advantage of the system is to exhibit non-zero crossing and gives more accurate result. The mean arterial pressure estimation is done by using MatLab which is the unique estimation method for measuring pulse transit time interval. Thus the non invasive system designed which reduce the cuff deviations and errors in electrocardiography. It can be applied in detecting the arterial disorders at most efficient manner.

Inferior ST-Elevation on the ECG

A 62-year-old woman presented to another hospital with a 36-hour history of uninterrupted, nonspecific chest pain. Her medical history included long-standing hypertension and diabetes mellitus for which she took metoprolol, perindopril, felodipine, metformin, and glimepiride. She had stopped smoking 10 years earlier, and did not drink alcohol or use illicit drugs. The ECG on the admission to the other hospital is shown in Figure 1. Laboratory results at the other hospital were all normal, with the exception of mild hyperglycemia; cardiac troponin I was also normal. Based on the ECG in Figure 1, the patient was transferred to our unit for emergency coronary angiography. Clinical examination on admission to our hospital was unremarkable. A repeated ECG on admission in our hospital is disclosed in Figure 2. Based on the history of uninterrupted chest pain in a patient with cardiovascular risk factors and the aspect of the ECG in Figure 1, the on-call cardiology team in our unit agreed with the indication for emergency coronary angiography. This, however, disclosed no significant coronary artery …

Resting vagal tone is negatively associated with suicide ideation

BackgroundThe present study aimed at investigating whether resting vagally mediated heart rate variability (HRV) as a trait-like biomarker of cognitive inhibitory control capacity is related to suicide ideation in a sample without suicide attempt history. MethodsThirty-seven healthy students participated voluntarily (18 to 34 years, M=24.5, SD=4.1; 73.0% female). Time and frequency measures of HRV were derived from an electrocardiogram that was recorded using Einthoven's Triangle lead II. Participants filled in the Rasch-based Depression Screening and four questions concerning lifetime suicide ideation (SI). Bivariate Pearson's and partial (controlling for depression severity) correlation coefficients were calculated between SI and measures of vagally mediated HRV. ResultsA significant correlation between the ln10-transformed high-frequency band of resting vagally mediated HRV and SI was found (r=−.33, p<.05). Correlations did not change substantially when controlling for depression. Mean heart rate as a time domain measure also significantly correlated with SI while controlling for depression (r=.36, p<.05). A trend correlation between SI and Root Mean Square of Successive Differences between interbeat intervals emerged. LimitationsSI was assessed with a composite score of four items measuring SI. Future studies should consider using more comprehensive assessment instruments. ConclusionsThe relation between resting vagally mediated HRV and suicide ideation may be interpreted as indicating that reduced inhibitory cognitive control capacity may be a risk factor for suicidality. It may act already early in the suicidal process, before suicidal behavior develops and should be further investigated as potentially clinically important physiological predictor of suicidality.

HEART DEPOLARIZATION VECTOR LOCUS CARDIOGRAM AND ITS CLINICAL DIAGNOSTIC APPLICATIONS

This study demonstrates the development of the heart depolarization vector locus cardiogram (HPVLC, from limb leads and a modified Einthoven's triangle) as a diagnostic measure of the left ventricular depolarization strength. Our work involves the reconstruction of the "equivalent heart electrical-activity vector (HAV)" for the QRS complex from limb leads voltages of a sample ECG recording, and plotting the progression of the cardiac vector during the QRS complex. A realistic visualization of the progression of the equivalent-dipole HAV during the QRS complex is possible by staging the HPVLC of the QRS complex from the onset of the QRS till the end of the depolarization stage. This can enable the characterization of the HPVLC by means of an analytical function. By studying the HPVLC for various electro-cardiological disorders, it is possible to determine the ranges of the analytical function's parameters for normal and disordered electro-cardiological states, for diagnostic purpose. We have seen that the monitored ECG is theoretically derived from HAV components on the sides of the Einthoven triangle. Nevertheless, in cardiac practice, the monitored ECG is employed in diagnosis of heart diseases. From the ECG, we can obtain the heart rate, and therefrom the heart rate variability, which too has diagnostic applications. Many nonlinear methods have been proposed to analyze ECG and HRV for detection of cardiac abnormalities, using linear and nonlinear methods. Herein, we have shown how HRV signal can be analyzed in terms of four recurrence quantification analysis (RQA) features, which are then combined into an Integrated Index to enable better separation of normal and diabetic subjects.

A simple device to illustrate the Einthoven triangle

The Einthoven triangle is central to the field of electrocardiography, but the concept of cardiac vectors is often a difficult notion for students to grasp. To illustrate this principle, we constructed a device that recreates the conditions of an ECG reading using a battery to simulate the electrical vector of the heart and three voltmeters for the main electrocardiographic leads. Requiring minimal construction with low cost, this device provides hands-on practice that enables students to rediscover the principles of the Einthoven triangle, namely, that the direction of the cardiac dipole can be predicted from the deflections in any two leads and that lead I + lead III = lead II independent of the position of heart's electrical vector. We built a total of 6 devices for classes of 30 students and tested them in the first-year Human Physiology course at the University of California-Davis School of Medicine. Combined with traditional demonstrations with ECG machines, this equipment demonstrated its ability to help medical students obtain a solid foundation of the basic principles of electrocardiography.

A Simple Device to Illustrate the Einthoven Triangle

Objective: Einthoven's Triangle is a crucial concept for the proper understanding of electrocardiography but the electrical vector of the heart is often difficult for students to grasp. In order to illustrate this principle, we constructed a device that simulates the ECG orientation and frontal plane vectors to simulate the heart's electrical activity for the main electrocardiographic leads (I, II and III). Materials & Methods: We built a box connected to a headboard with three analog voltmeters and a battery that simulates the electrical activity of the heart. Placed on the top of the box is an acrylic board with a diagram of the Einthoven Triangle, consisting of an equilateral triangle with an inscribed concentric circle. The voltmeters were connected to the corners of the triangle, mirroring the standard ECG leads. Silver-chlorided electrodes were placed at the center and at twelve equally spaced positions (30 degrees apart) along the circle. All electrodes were electrically “connected” by submergence in a 10 mM saline solution (NaCl). A particular position of the heart's electrical vector was simulated by connecting the negative terminal of the battery to the center of the circle and the positive terminal to an electrode along the circumference. At every position, readings from meters I, II and III were taken. We built a total of six devices for a class of thirty students and tested them in the HPH 400 Human Physiology course at the UC Davis School of Medicine. Conclusions: This device enabled students to verify the Einthoven Triangle principle; namely, that Lead I + Lead III = Lead II, independent of the heart's electrical vector position. Combined with the traditional demonstration with ECG machines, this equipment helps medical students to obtain a solid foundation of the basic principles of electrocardiography.

Einthoven's Triangle Transparency: A Practical Method to Explain Limb Lead Configuration Following Single Lead Misplacements

Limb lead switches remain a significant source of electrocardiographic error that may lead to faulty diagnosis and improper clinical action. Methods to identify such errors have been the subject of many prior publications. A brief review of the mathematical derivation of the limb lead system is presented here, together with an additional method to help understand limb lead reversals using a transparency of the Einthoven's triangle.

Design of a Three-Lead Synthetic ECG Generator Using the Simplified McSharry's Model

Recently, due to the dramatic improvement in computing capabilities and processing speed of microcontrollers and digital signal processors, many analytic algorithms for electrocardiograms (ECGs) have been developed and applied to a variety of portable electronic devices. In order to test whether the algorithms can analyze the various morphologies of electrocardiogram well, it is necessary to expend much effort collecting various ECG samples to establish an ECG database. Therefore, this paper simplifies and adopts a synthetic electrocardiogram model composed of three coupled differential equations proposed by Dr. McSharry et al. (2003), as well as utilizes an improved fourth-order Taylor series to quickly approximate the exponential function within the differential equation of a simplified synthetic ECG model so that, when studying ECG analytic algorithms, the graphical user interface (GUI) application “Synthetic Waveforms Control Panel,” developed by the author using LabVIEW, can be used to attain the desirable morphology of electrocardiogram as well as the time intervals between peaks (P, Q, R, S, T) and heart rate. The parameters of the adjusted synthetic ECG model are then sent to the memory of a synthetic ECG generator through a USB interface, and the ECG generator will generate three synthetic electrocardiograms of Einthoven's triangle for testing the electrocardiogram analytic algorithms.

Utility of the Frontal Plane QRS Axis in Identifying Non–ST-Elevation Myocardial Infarction in Patients With Poor R-Wave Progression

Poor R-wave progression (PRWP) is a common electrocardiographic phenomenon in which the anticipated increase in R-wave amplitude in successive precordial leads, V(1) to V(5), fails to occur. PRWP is prevalent in approximately 10% of hospitalized adult patients, predominantly in those with coronary artery disease. Debate is ongoing on its association with myocardial infarction (MI). However, studies that showed no association failed to appraise the significance of the QRS axis in relation to PRWP among such patients with MI. In our retrospective study, we consecutively identified 150 unselected adult patients with PRWP among 660 successive admissions to the general medical floors of a tertiary care teaching hospital (Saint Vincent Hospital, Worcester, Massachusetts). After excluding patients with anterior wall Q-wave MI (defined as the presence of a QS complex or Q-wave > or =1 mm deep in V(2) or V(3)), sudden unexpected death, MI after percutaneous coronary interventions or coronary artery bypass grafting during this hospitalization, Wolff-Parkinson-White syndrome, pacemakers, bundle branch blocks, and electrocardiograms that were of poor quality or affected by severe motion artifact, inconsistencies with patient identification, or errors in lead placement, 137 patients remained. The patients were then screened for non-ST-segment elevation MI (NSTEMI) during the present admission. The DePace criteria for PRWP were systematically used for all patients, and the QRS axis was calculated using limb leads based on Einthoven's equilateral triangle (normal was considered -30 degrees to 100 degrees ). Of the 137 study patients screened with PRWP, 38 had NSTEMI (25.3%). Thirty-one had a normal QRS axis (mean age +/- standard deviation 71.3 +/- 12 years), and 7 showed either right or left axis deviation (mean age +/- standard deviation 64.3 +/- 15 years). This proved to be statistically significant (p <0.0001) within this cohort of NSTEMI patients. In conclusion, PRWP determined using the DePace criteria in the presence of a normal QRS axis appears to be more significantly associated with the presence of overall MI within this cohort of NSTEMI patients.

Frontal Plane Vectorcardiograms: Theory and Graphics Visualization of Cardiac Health Status

The electrocardiogram (ECG) is a representative signal containing information about the condition of the heart. The shape and size of the P-QRS-T wave, the time intervals between its various peaks, may contain useful information about the nature of disease afflicting the heart. However, these subtle details cannot be directly monitored by the human observer. Besides, these signals are highly subjective, and the symptoms may appear at random in the time scale. It is very taxing and time-consuming to decipher cardiac abnormalities based on these ECG signals. The Vectorcardiogram (VCG) is the vector loop in the 2-D frontal plane, indicating the magnitude and direction of the instantaneous heart electrical activity vector (HAV), which represents the sum of the dipole vectors located along the instantaneous depolarization wavefront. The HAV is constructed from the monitored 3-lead ECG signals, placed at the three vertices of the modified Einthoven triangle formed by the 3-lead system in the frontal plane of the torso. The VCG examines the electrical activities within the heart, using the ECG signals along the three sides of the modified Einthoven triangle, and displays electrical events in the 2-dimensional frontal plane. This study demonstrates the development of the heart-depolarisation vector-locus cardiogram (using modified Einthoven's triangle), as a diagnostic measure of the left ventricular depolarisation strength. Our work involves the reconstruction of the "equivalent heart vector" for the QRS complex from limb lead voltages of a sample ECG, and plotting the progression of the cardiac vector during the QRS complex. We have demonstrated the construction of the frontal plane heart-depolarization vector cardiogram (HDVC), as the path of the locus of the tip of the heart electrical activity vector, with initial and terminal points at the origin. In this work, we have shown characteristic patterns of HDVC for cardiac states namely, normal, bundle branch block, ventricular hypertrophy and myocardial infarction. We have demonstrated how HDVC can be diagnostically employed to characterize cardiac disorders, such as ventricular hypertrophy bundle branch block and inferior myocardial infarction.

Simple Diagnosis of Limb‐Lead Reversals by Predictable Changes in QRS Axis

Limb-lead reversals (LLRs) remain clinically problematic. Because the frontal QRS axis is derived from an equilateral Einthoven triangle and LLRs either rotate (180 degrees horizontally (mirror-image (M)) and/or 120 degrees vertically (clockwise (C)/counterclockwise (CC)) or distort the triangle (by forcing a bipolar lead to record across the lower extremities (LE) where electrical potentials approach zero (zero-potential lead)), we hypothesize that LLR axes changes from a baseline value (n) are predictable. Three hundred and sixty ECGs with all 24 limb-lead combinations from 15 individuals were analyzed. Predicted and actual QRS axes were compared using linear regression. Twenty-four lead combinations produced only 12 (11 abnormal) ECG patterns and diagnosis depended upon identifying upper extremity (UE) cable configurations. Predicted formulas for rotation-type LLR axes (M, C, CC, MC, and MCC) were 180 - n, n - 120, n + 120, 300 - n, and 60 - n, respectively. Corresponding mean differences between predicted and actual values were 4 +/- 5 degrees , 4 +/- 2 degrees , 7 +/- 10 degrees , 5 +/- 7 degrees , and 3 +/- 4 degrees (all r = 0.99 - 1.00, P < 0.0001). The predicted formula for distortion-type LLR axes is (zero-potential lead axis) +/- 90 degrees . Actual mean values for zero-potential lead I, II, and III were 90 +/- 7 degrees or 266 +/- 17 degrees , -31 +/- 6 degrees or 148 +/- 14 degrees , and 26 +/- 14 degrees or 209 +/- 9 degrees , respectively. The mean difference between predicted and actual values for all LLRs was 5 +/- 8 degrees (r = 1.00, P < 0.0001). LLR axes are predictable within an average of 5 degrees . This might help differentiate an acute axis shift due to an LLR from serious medical conditions that may require treatment.

Einthoven's Triangle: Lead Errors and An Algorithm for Solution

Einthoven's Triangle: Lead Errors and An Algorithm for Solution