The classical versus the Cabrera presentation system for resting electrocardiography: Impact on recognition and understanding of clinically important electrocardiographic changes

Associations between electrocardiographic findings and echocardiographic profiles in patients with hypertrophic cardiomyopathy

BACKGROUND

The relationships between electrocardiography (ECG) findings and echocardiographic profiles in patients with hypertrophic cardiomyopathy (HCM) are not fully understood.

METHODS

One hundred forty patients (mean age: 62.9 ± 15.3 years, 96 men) with HCM were studied. We assessed the associations between ECG findings and echocardiographic findings including maximum left ventricular wall thickness, HCM subtypes and distribution of left ventricular hypertrophy (LVH): the LV was divided into basal, mid, and apical segments by dividing it into thirds along the long axis.

RESULTS

In ECG, LVH by voltage criteria, abnormal Q wave, negative T wave, and giant negative T wave (GNT) were observed in 74 (53 %), 30 (21 %), 132 (94 %), and 25 (18 %) of the patients, respectively. In two groups with and without an LVH pattern according to voltage criteria in ECG, there were no significant differences in maximum LV wall thickness, subtype of HCM, and distribution of LVH. Regarding an abnormal Q wave, the proportion of patients with LVH in the basal segment was significantly higher in patients with an abnormal Q wave than in patients without an abnormal Q wave (87 % vs 61 %, p = 0.008). An abnormal Q wave was not observed in patients with LVH confined to the apex. Patients with a GNT included patients with LVH located at only the apex (apical HCM), LVH from the mid segment to apex, and LVH from the base to apex. No GNT was found in patients with hypertrophy located in the upper region from the base to mid segment of the LV.

CONCLUSIONS

In patients with HCM, there was no significant correlation between the presence of LVH by voltage criteria in ECG and echocardiographic findings. An abnormal Q wave was associated with disproportionate hypertrophy of the basal wall and a GNT reflected the presence of LVH in the apical segment.

Donor Electrocardiogram Associations With Cardiac Dysfunction, Heart Transplant Use, and Survival: The Donor Heart Study

BACKGROUND

Potential organ donors often exhibit abnormalities on electrocardiograms (ECGs) after brain death, but the physiological and prognostic significance of such abnormalities is unknown.

OBJECTIVES

This study sought to characterize the prevalence of ECG abnormalities in a nationwide cohort of potential cardiac donors and their associations with cardiac dysfunction, use for heart transplantation (HT), and recipient outcomes.

METHODS

The Donor Heart Study enrolled 4,333 potential cardiac organ donors at 8 organ procurement organizations across the United States from 2015 to 2020. A blinded expert reviewer interpreted all ECGs, which were obtained once hemodynamic stability was achieved after brain death and were repeated 24 ± 6 hours later. ECG findings were summarized, and their associations with other cardiac diagnostic findings, use for HT, and graft survival were assessed using univariable and multivariable regression.

RESULTS

Initial ECGs were interpretable for 4,136 potential donors. Overall, 64% of ECGs were deemed clinically abnormal, most commonly as a result of a nonspecific St-T-wave abnormality (39%), T-wave inversion (19%), and/or QTc interval >500 ms (17%). Conduction abnormalities, ectopy, pathologic Q waves, and ST-segment elevations were less common (each present in ≤5% of donors) and resolved on repeat ECGs in most cases. Only pathological Q waves were significant predictors of donor heart nonuse (adjusted OR: 0.39; 95% CI: 0.29-0.53), and none were associated with graft survival at 1 year post-HT.

CONCLUSIONS

ECG abnormalities are common in potential heart donors but often resolve on serial testing. Pathologic Q waves are associated with a lower likelihood of use for HT, but they do not portend worse graft survival.

Discrimination between ventricular tachycardia and wide-QRS preexcited tachycardia

BACKGROUND

To develop a new algorithm to differentiate ventricular tachycardia (VT) from preexcited tachycardia (pre-ET) according to left bundle branch block (LBBB) and right bundle branch block (RBBB) patterns.

METHODS

This study included 67 electrocardiograms (ECGs) with VT and 63 ECGs with pre-ET, collected from our hospital and through PubMed. Of those, 64 were allocated to the derivation cohort and the rest to the validation cohort. The diagnoses of the ECGs were confirmed using an electrophysiological study. Parameters and classifiers from prior algorithms along with the propagation speeds in the early portion of the QRS complex (initial deflection index) in leads V1, V6, aVR, II, and III were manually measured. The performance of the new algorithm was compared with that of prior algorithms.

RESULTS

The initial deflection index in lead III was the strongest predictor of pre-ET in LBBB-pattern wide-QRS tachycardia (p = 0.003, AUC 0.805). The initial deflection index in lead V1 was the most powerful predictor of pre-ET in RBBB-pattern wide-QRS tachycardia (p = 0.001, AUC 0.848). Compared to earlier algorithms, those using the initial deflection indexes: lead III in LBBB patterns (cutoff value >0.3) and lead V1 in RBBB patterns (cutoff value ≤0.48), demonstrated superior performance in screening VT, with AUC values of 0.828. The initial deflection indexes proved effective as discriminators between VT and pre-ET in the validation cohort.

CONCLUSIONS

In LBBB-pattern wide-QRS tachycardia, the early propagation speed of pre-ET was faster than that in VT. Conversely, in RBBB-pattern wide-QRS tachycardia, it was slower.

Completing the Cabrera Circle: deriving adaptable leads from ECG limb leads by combining constraints with a correction factor

Objective.We present a concept for processing 6-lead electrocardiography (ECG) signals which can be applied to various use cases in quantitative electrocardiography.Approach.Our work builds upon the mathematics of the well-known Cabrera sequence which is a re-sorting of the six limb leads (I,II,III,aVR,aVL,aVF) into a clockwise and physiologically-interpretable order. By deriving correction factors for harmonizing lead strengths and choosing an appropriate basis for the leads, we extend this concept towards what we call the 'Cabrera Circle' based on a mathematically sound foundation.Main results.To demonstrate the practical effectiveness and relevance of this concept, we analyze its suitability for deriving interpolated leads between the six limb leads and a 'radial' lead which both can be useful for specific use cases. We focus on the use cases of i) determination of the electrical heart axis by proposing a novel interactive tool for reconstructing the heart's vector loop and ii) improving accuracy in time of automatic R-wave detection and T-wave delineation in 6-lead ECG. For the first use case, we derive an equation which allows projections of the 2-dimensional vector loops to arbitrary angles of the Cabrera Circle. For the second use case, we apply several state-of-the-art algorithms to a freely-available 12-lead dataset (Lobachevsky University Database). Out-of-the-box results show that the derived radial lead outperforms the other limb leads (I,II,III,aVR,aVL,aVF) by improving F1 scores of R-peak and T-peak detection by 0.61 and 2.12, respectively. Results of on- and offset computations are also improved but on a smaller scale.Significance.In summary, the Cabrera Circle offers a methodology that might be useful for quantitative electrocardiography of the 6-lead subsystem-especially in the digital age.

An error in interpretation and real extraordinary electrocardiographic changes in patient with acute traumatic spondylolisthesis

Background

Acute cervical spinal trauma may lead to cardiac effects by influencing cardiac sympathetic preganglionic fibers. Some of these effects, which are vital, may occur in ECG.

Case presentation

A 52-year-old female patient admitted to the emergency department with acute traumatic spondylolisthesis at C6-C7 level and paraplegia. Positive QRS complex, ST segment depressions and prolongation of QTc interval were observed on ECG according to sudden autonomic disruption because of sympathetic nerve compression. It was mentioned that changes in QRS complex axis was normal which was dependent to the ECG display format of Cabrera sequence used differently from the classical system. After surgical correction, evident ST depressions were recovered and QTc intervalwas narrowed but still prolonged in control ECG.

Conclusions

Autonomic dysfunction can lead to extraordinary electrocardiographic presentation including widespread ST depressions with prolonged QTc interval. However, when evaluating the changes in the ECG, attention should be paid to ECG display format to avoid errors in interpretation.

Golden Standard or Obsolete Method? Review of ECG Applications in Clinical and Experimental Context

Cardiovascular system and its functions under both physiological and pathophysiological conditions have been studied for centuries. One of the most important steps in the cardiovascular research was the possibility to record cardiac electrical activity. Since then, numerous modifications and improvements have been introduced; however, an electrocardiogram still represents a golden standard in this field. This paper overviews possibilities of ECG recordings in research and clinical practice, deals with advantages and disadvantages of various approaches, and summarizes possibilities of advanced data analysis. Special emphasis is given to state-of-the-art deep learning techniques intensely expanded in a wide range of clinical applications and offering promising prospects in experimental branches. Since, according to the World Health Organization, cardiovascular diseases are the main cause of death worldwide, studying electrical activity of the heart is still of high importance for both experimental and clinical cardiology.

Constructing Adult Zebrafish Einthoven's Triangle to Define Electrical Heart Axes

Zebrafish is 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). However, zebrafish electrical heart axes were unknown. It is impossible to define heart axis based on single-lead ECG because determination of an electrical heart axis in the frontal plane requires the use of the hexaxial reference system (or Cabrera system) derived from Einthoven’s triangle. Construction of Einthoven’s triangle requires simultaneous ECG recording from at least two Einthoven bipolar leads. Therefore, we systematically constructed the first zebrafish Einthoven’s triangle by simultaneous bipolar dual-lead ECG recording to determine for the first time the three frontal electrical heart axes using the Cabrera system. Comparing zebrafish with human Einthoven’s triangle reveals that their normal frontal electrical axes were reflections of each other across 0° in the Cabrera system. The responsible mechanisms involve zebrafish vs. human cardiac activation propagating in the same direction along the heart horizontal axis but in opposite directions along the heart longitudinal axis. The same observations are true for zebrafish vs. human cardiac repolarization. This study marks a technical breakthrough in the first bipolar dual-lead ECG recording in live adult zebrafish to construct for the first time zebrafish Einthoven’s triangle. This first systematic analysis of the actual differences and similarities between normal adult zebrafish and human Einthoven’s triangles unmasked differences and similarities in the underlying cardiac axis mechanisms. Insights of the live adult zebrafish main heart axis and its three frontal electrical heart axes provide critical contextual framework to interpret the clinical relevance of the adult zebrafish heart as model for human cardiac electrophysiology.

Orderly display of limb lead ECGs raises Chinese intern's diagnostic accuracy when determining frontal plane QRS axis

BACKGROUND

There is limited information on whether the orderly display of limb lead ECGs (electrocardiograms) can facilitate students to determine frontal plane QRS complex wave electrical axis.

OBJECTIVES

The study investigated whether the orderly display of limb lead ECGs can raise Chinese undergraduate intern's diagnostic accuracy when determining frontal plane axis.

DESIGN

A total of 147 fifth-year undergraduate interns aged between 21 and 25 years were randomly arranged into 2 groups: one group was given classically displayed ECGs of limb leads while the other group was given orderly displayed ECGs of limb leads. They were then taught to determine frontal plane axis with one of the above displays. The intern's diagnostic accuracy and time used were measured.

RESULTS

After teaching, the orderly display can more effectively raise diagnostic accuracy when determining axis as compared to the classical display (76.65 ± 23.16% vs. 68.88 ± 23.21%, P < 0.05), although diagnostic accuracy in axis determination was improved in both groups as compared to the axis determination at baseline (all P < 0.05).

CONCLUSIONS

Orderly display of limb lead ECGs may raise Chinese intern's diagnostic accuracy when determining frontal plane axis.

Why complicate an important task? An orderly display of the limb leads in the 12-lead electrocardiogram and its implications for recognition of acute coronary syndrome

Background

In the standard ECG display, limb leads are presented in a non-anatomical sequence: I, II, III, aVR, aVL, aVF. The Cabrera system is a display format which instead presents the limb leads in a cranial/left-to-caudal/right sequence, i.e. in an anatomically sequential order. Lead aVR is replaced in the Cabrera display by its inverted version, −aVR, which is presented in its logical place between lead I and lead II.

Main text

In this debate article possible implications of using the Cabrera display, instead of the standard, non-contiguous lead display, are presented, focusing on its use in patients with possible acute coronary syndrome. The importance of appreciating reciprocal limb-lead ECG changes and the diagnostic and prognostic value of including aVR or lead −aVR in ECG interpretation in acute coronary syndrome is covered. Illustrative cases and ECGs are presented with both the standard and contiguous limb lead display for each ECG.

A contiguous lead display is useful when diagnosing acute coronary syndrome in at least 3 ways: 1) when contiguous leads are present adjacent to each other, identification of ST elevation in two contiguous leads is simple; 2) a contiguous lead display facilitates understanding of lead relationships as well as reciprocal changes; 3) it makes the common neglect of lead aVR unlikely.

Conlusions

It is logical to display the limb leads in their sequential anatomical order and it may have advantages both in diagnostics and ECG learning.

Implications of Using the Cabrera Sequence for Diagnosing Acute Coronary Syndrome

The 12-lead electrocardiogram (ECG) is the important, initial examination for diagnosing acute coronary syndrome (ACS). In the traditional 12-lead ECG display, the precordial leads are displayed in their anatomically contiguous order, which makes it easy to understand the positional relationships between the precordial leads and the heart, but the limb leads are not. The "Cabrera sequence" displays the limb leads in an anatomically contiguous manner, which facilitates understanding of the positional relations between the limb leads and the heart, resulting in more rapid, easy, and accurate ECG interpretation than the traditional limb leads display. This review explores the clinical advantages of the Cabrera sequence as compared with the traditional limb leads display for the diagnosis of ACS. (Circ J 2016; 80: 1087-1096).