Electrical and structural remodeling in left ventricular hypertrophy-a substrate for a decrease in QRS voltage?

ISE/ISHNE Expert Consensus Statement on ECG Diagnosis of Left Ventricular Hypertrophy: The Change of the Paradigm. The joint paper of the International Society of Electrocardiology and the International Society for Holter Monitoring and Noninvasive Electrocardiology

The ECG diagnosis of LVH is predominantly based on the QRS voltage criteria, i.e. the increased QRS complex amplitude in defined leads. The classical ECG diagnostic paradigm postulates that the increased left ventricular mass generates a stronger electrical field, increasing the leftward and posterior QRS forces. These increased forces are reflected in the augmented QRS amplitude in the corresponding leads. However, the clinical observations document increased QRS amplitude only in the minority of patients with LVH. The low sensitivity of voltage criteria has been repeatedly documented. We discuss possible reasons for this shortcoming and proposal of a new paradigm.

Predicting left ventricular hypertrophy from the 12-lead electrocardiogram in the UK Biobank imaging study using machine learning

Aims

Left ventricular hypertrophy (LVH) is an established, independent predictor of cardiovascular disease. Indices derived from the electrocardiogram (ECG) have been used to infer the presence of LVH with limited sensitivity. This study aimed to classify LVH defined by cardiovascular magnetic resonance (CMR) imaging using the 12-lead ECG for cost-effective patient stratification.

Methods and results

We extracted ECG biomarkers with a known physiological association with LVH from the 12-lead ECG of 37 534 participants in the UK Biobank imaging study. Classification models integrating ECG biomarkers and clinical variables were built using logistic regression, support vector machine (SVM) and random forest (RF). The dataset was split into 80% training and 20% test sets for performance evaluation. Ten-fold cross validation was applied with further validation testing performed by separating data based on UK Biobank imaging centres. QRS amplitude and blood pressure (P < 0.001) were the features most strongly associated with LVH. Classification with logistic regression had an accuracy of 81% [sensitivity 70%, specificity 81%, Area under the receiver operator curve (AUC) 0.86], SVM 81% accuracy (sensitivity 72%, specificity 81%, AUC 0.85) and RF 72% accuracy (sensitivity 74%, specificity 72%, AUC 0.83). ECG biomarkers enhanced model performance of all classifiers, compared to using clinical variables alone. Validation testing by UK Biobank imaging centres demonstrated robustness of our models.

Conclusion

A combination of ECG biomarkers and clinical variables were able to predict LVH defined by CMR. Our findings provide support for the ECG as an inexpensive screening tool to risk stratify patients with LVH as a prelude to advanced imaging.

Improved evaluation of left ventricular hypertrophy using the spatial QRS-T angle by electrocardiography

Electrocardiographic (ECG) signs of left ventricular hypertrophy (LVH) lack sensitivity. The aim was to identify LVH based on an abnormal spatial peaks QRS-T angle, evaluate its diagnostic performance compared to conventional ECG criteria for LVH, and its prognostic performance. This was an observational study with four cohorts with a QRS duration < 120 ms. Based on healthy volunteers (n = 921), an abnormal spatial peaks QRS-T angle was defined as ≥ 40° for females and ≥ 55° for males. In other healthy volunteers (n = 461), the specificity of the QRS-T angle to detect LVH was 96% (females) and 98% (males). In patients with at least moderate LVH by cardiac imaging (n = 225), the QRS-T angle had a higher sensitivity than conventional ECG criteria (93–97% vs 13–56%, p < 0.001 for all). In clinical consecutive patients (n = 783), of those who did not have any LVH, 238/556 (43%) had an abnormal QRS-T angle. There was an association with hospitalization for heart failure or all-cause death in univariable and multivariable analysis. An abnormal QRS-T angle rarely occurred in healthy volunteers, was a mainstay of moderate or greater LVH, was common in clinical patients without LVH but with cardiac co-morbidities, and associated with outcomes.

Complementary value of ECG and echocardiographic left ventricular hypertrophy for prediction of adverse outcomes in the general population

OBJECTIVE

To investigate whether ECG left ventricular hypertrophy (ECG-LVH) has prognostic value independent of echocardiography LVH (Echo-LVH).

METHODS

Participants (N = 9744, mean age, 53.81 ± 10.49 years and 45.5% male) from the Northeast China Rural Cardiovascular Health Study were included. Associations between Echo-LVH (sex-specific left ventricular mass normalized to BSA) and ECG-LVH (diagnosed using the Cornell-voltage duration product) and adverse outcomes were evaluated using Cox regression. The value of ECG-LVH for predicting adverse events was evaluated by reclassification and discrimination analyses.

RESULTS

Median follow-up was 4.65 years; 563 participants developed incident stroke or coronary heart disease (CHD) and 402 died. Compared with participants without either condition, those with both Echo-LVH and ECG-LVH had a significantly increased risk of incident stroke or CHD (hazard ratio, 2.42; 95% confidence interval, 1.82-3.22) and mortality (2.58; 1.85-3.60). ECG-LVH remained an independent risk factors for both outcomes when ECG-LVH and Echo-LVH were included in the model as separate variables [incident stroke or CHD (1.43; 1.14-1.79); mortality (1.41; 1.08-1.84)]. Reclassification and discrimination analyses indicated ECG-LVH addition could improve the conventional model for predicting adverse outcomes within 4 years. These relationships persisted after excluding participants with cardiovascular disease history or taking antihypertension drugs or upon applying other ECG-LVH and Echo-LVH diagnostic criteria.

CONCLUSION

Our study provides strong evidence that ECG-LVH is associated with adverse outcomes, independent of Echo-LVH. Clinically, ECG-LVH could be considered as a consequential factor, especially in those with Echo-LVH. These findings have potential clinical relevance for risk stratification.

Missing Link between Molecular Aspects of Ventricular Arrhythmias and QRS Complex Morphology in Left Ventricular Hypertrophy

The aim of this opinion paper is to point out the knowledge gap between evidence on the molecular level and clinical diagnostic possibilities in left ventricular hypertrophy (LVH) regarding the prediction of ventricular arrhythmias and monitoring the effect of therapy. LVH is defined as an increase in left ventricular size and is associated with increased occurrence of ventricular arrhythmia. Hypertrophic rebuilding of myocardium comprises interrelated processes on molecular, subcellular, cellular, tissue, and organ levels affecting electrogenesis, creating a substrate for triggering and maintaining arrhythmias. The knowledge of these processes serves as a basis for developing targeted therapy to prevent and treat arrhythmias. In the clinical practice, the method for recording electrical phenomena of the heart is electrocardiography. The recognized clinical electrocardiogram (ECG) predictors of ventricular arrhythmias are related to alterations in electrical impulse propagation, such as QRS complex duration, QT interval, early repolarization, late potentials, and fragmented QRS, and they are not specific for LVH. However, the simulation studies have shown that the QRS complex patterns documented in patients with LVH are also conditioned remarkably by the alterations in impulse propagation. These QRS complex patterns in LVH could be potentially recognized for predicting ventricular arrhythmia and for monitoring the effect of therapy.

Diagnostic utility of biomarkers of left ventricular stress in patients with aortic stenosis and preserved left ventricular ejection fraction

INTRODUCTION

Aortic stenosis (AS) is the most common acquired valvular heart disease. The early identification of patients with severe AS is crucial. NT-proBNP is a well-known biomarker of pressure overload, and its role in patients with AS has been demonstrated in previous studies. Another, less well-known biomarker of pressure overload is sST2 protein, and its role in AS is unclear.

AIM

To evaluate the utility of sST2 protein, NT-proBNP and selected clinical parameters in the assessment of degenerative AS severity in a population with preserved left ventricular ejection fraction (LVEF).

MATERIAL AND METHODS

Sixty-nine consecutive patients (mean age: 68.42 ±12.58 years, 55.07% male) with symptomatic degenerative AS and preserved LVEF ≥ 45% were prospectively included. At enrollment complete transthoracic echocardiographic examination, ECG analysis, and standard laboratory tests including NT-proBNP were performed and blood samples for sST2 were obtained.

RESULTS

There were 43 (62.32%) patients with severe AS. The multivariate stepwise linear regression models revealed that only systolic blood pressure (SBP), Sokolow-Lyon index and left ventricular end-diastolic diameter (LVEDD) were independently associated with severe AS. Spearman correlation coefficients analysis showed no correlations between sST2 levels and a mild to moderate correlation between NT-proBNP concentration and parameters of AS severity. However, levels of NT-proBNP (p = 0.1857) and sST2 (p = 0.7851) did not differentiate patients according to severity of AS.

CONCLUSIONS

In the study population with degenerative AS and preserved LVEF neither the NT-proBNP nor sST2 concentrations can be used to differentiate patients according to the severity of AS.

Diffuse Myocardial Fibrosis Reduces Electrocardiographic Voltage Measures of Left Ventricular Hypertrophy Independent of Left Ventricular Mass

Background

Myocardial fibrosis quantified by myocardial extracellular volume fraction (ECV) and left ventricular mass (LVM) index (LVMI) measured by cardiovascular magnetic resonance might represent independent and opposing contributors to ECG voltage measures of left ventricular hypertrophy (LVH). Diffuse myocardial fibrosis can occur in LVH and interfere with ECG voltage measures. This phenomenon could explain the decreased sensitivity of LVH detectable by ECG, a fundamental diagnostic tool in cardiology.

Methods and Results

We identified 77 patients (median age, 53 [interquartile range, 26–60] years; 49% female) referred for contrast‐enhanced cardiovascular magnetic resonance with ECV measures and 12‐lead ECG. Exclusion criteria included clinical confounders that might influence ECG measures of LVH. We evaluated ECG voltage‐based LVH measures, including Sokolow‐Lyon index, Cornell voltage, 12‐lead voltage, and the vectorcardiogram spatial QRS voltage, with respect to LVMI and ECV. ECV and LVMI were not correlated (R²=0.02; P=0.25). For all voltage‐related parameters, higher LVMI resulted in greater voltage (r=0.33–0.49; P<0.05 for all), whereas increased ECV resulted in lower voltage (r=−0.32 to −0.57; P<0.05 for all). When accounting for body fat, LV end‐diastolic volume, and mass‐to‐volume ratio, both LVMI (β=0.58, P=0.03) and ECV (β=−0.46, P<0.001) were independent predictors of QRS voltage (multivariate adjusted R²=0.39; P<0.001).

Conclusions

Myocardial mass and diffuse myocardial fibrosis have independent and opposing effects upon ECG voltage measures of LVH. Diffuse myocardial fibrosis quantified by ECV can obscure the ECG manifestations of increased LVM. This provides mechanistic insight, which can explain the limited sensitivity of the ECG for detecting increased LVM.

Comparison of Nigella sativa- and exercise-induced models of cardiac hypertrophy: structural and electrophysiological features

Exercise training is employed as supplementary therapeutic intervention for heart failure, due to its ability to induce physiological cardiac hypertrophy. In parallel, supplementation with Nigella sativa (N. sativa) was found to enhance myocardial function and induce cardiac hypertrophy. In this study, we aim to compare the morphological and electrophysiological changes associated with these patterns of cardiac hypertrophy and the possible changes upon administration of N. sativa to exercise-trained animals. Fifty-six adult Wistar rats were divided into: control, Nigella-treated (N), exercise-trained (E), and Nigella-treated-exercise-trained (NE) rats. Daily 800 mg/kg N. sativa was administered orally to N and NE. E and NE ran on treadmill, 2 h/day. At the end of 8 weeks ECG, body weight (BW), heart weight (HW), and left ventricular weight (LVW) were recorded. Hematoxylin and Eosin and periodic acid-Schiff sections were prepared to study the histology of left ventricles and to measure diameter of cardiomyocytes (Cdia). HW/BW, LVW/BW, and mean Cdia were significantly higher in all experimental animals compared to the controls. Histology showed normal cardiomyocytes with no fibrosis. ECG showed significantly lower heart rates, higher QRS amplitude, and ventricular specific potential in NE group compared to control group. Supplementation of N. sativa demonstrated a synergistic effect with exercise training as Nigella-exercise-induced cardiac hypertrophy had lower heart rate and well-matched electrical activity of the heart to its mass. Therefore, this model of cardiac hypertrophy might be introduced as a new therapeutic strategy for treatment for heart failure with superior advantages to exercise training.

Electrocardiographic versus echocardiographic left ventricular hypertrophy and sudden cardiac arrest in the community

BACKGROUND

Left ventricular hypertrophy (LVH) is associated with increased risk of sudden cardiac arrest (SCA). Whether LVH diagnosed by 12-lead ECG vs echocardiogram conveys identical or distinct risk information has not been previously evaluated.

OBJECTIVE

The purpose of this study was to compare the association between ECG vs echocardiographic LVH and SCA in the community.

METHODS

In a large, prospective population-based study (The Oregon Sudden Unexpected Death Study; population approximately 1 million), cases of SCA were compared to controls recruited from the same geographical area. The association between LVH and SCA was evaluated, specifically comparing LVH diagnosed by ECG vs echocardiogram.

RESULTS

Cases (n = 132, age 66.9 ± 13.5 years, 58.3% male) compared to controls (n = 211; age 66.2 ± 12 years, 59.2% male) were more likely to have both ECG LVH (12.1% vs 5.7%, P = .03) and echocardiographic LVH (35.0% vs 15.5%, P <.001). However, there was poor agreement between the tests (kappa statistic = 0.128). A large subgroup of patients with ECG LVH (57.1%) did not have echocardiographic LVH; conversely, 83.6% of patients with echocardiographic LVH did not have ECG LVH. In multivariate analysis, ECG LVH was significantly associated with SCA (odds ratio [OR] 2.5, 95% confidence interval [CI] 1.1-6.0, P = .04). When echocardiographic LVH was added to the model, this association was only mildly attenuated (OR 2.4, 95% CI 1.0-6.0, P= .05), and echocardiographic LVH was also independently associated with SCA (OR 2.7, 95% CI 1.5-4.9, P = .001).

CONCLUSION

ECG and echocardiographic LVH may convey distinct risk information in patients with SCA, reflecting electrical vs anatomic remodeling. These findings have potential implications for SCA mechanisms and risk stratification.

ECG marker of adverse electrical remodeling post-myocardial infarction predicts outcomes in MADIT II study

BACKGROUND

Post-myocardial infarction (MI) structural remodeling is characterized by left ventricular dilatation, fibrosis, and hypertrophy of the non-infarcted myocardium.

OBJECTIVE

The goal of our study was to quantify post-MI electrical remodeling by measuring the sum absolute QRST integral (SAI QRST). We hypothesized that adverse electrical remodeling predicts outcomes in MADIT II study participants.

METHODS

Baseline orthogonal ECGs of 750 MADIT II study participants (448 [59.7%] ICD arm) were analyzed. SAI QRST was measured as the arithmetic sum of absolute QRST integrals over all three orthogonal ECG leads. The primary endpoint was defined as sudden cardiac death (SCD) or sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) with appropriate ICD therapies. All-cause mortality served as a secondary endpoint.

RESULTS

Adverse electrical remodeling in post-MI patients was characterized by wide QRS, increased magnitudes of spatial QRS and T vectors, J-point deviation, and QTc prolongation. In multivariable Cox regression analysis after adjustment for age, QRS duration, atrial fibrillation, New York Heart Association heart failure class and blood urea nitrogen, SAI QRST predicted SCD/VT/VF (HR 1.33 per 100 mV*ms (95%CI 1.11-1.59); P = 0.002), and all-cause death (HR 1.27 per 100 mV*ms (95%CI 1.03-1.55), P = 0.022) in both arms. No interaction with therapy arm and bundle branch block (BBB) status was found.

CONCLUSIONS

In MADIT II patients, increased SAI QRST is associated with increased risk of sustained VT/VF with appropriate ICD therapies and all-cause death in both ICD and in conventional medical therapy arms, and in patients with and without BBB. Further studies of SAI QRST are warranted.

Computer simulation of ECG manifestations of left ventricular electrical remodeling

An increased QRS voltage is considered to be specific for the electrocardiogram (ECG) diagnosis of left ventricular hypertrophy (LVH). However, the QRS-complex patterns in patients with LVH cover a broader spectrum: increased QRS voltage, prolonged QRS duration, left axis deviation, and left anterior fascicular block- and left bundle branch block-like patterns, as well as pseudo-normal QRS patterns. The classical interpretation of the QRS patterns in LVH relates these changes to increased left ventricular mass (LVM) per se, while tending to neglect the modified active and passive electrical properties of the myocardium. However, it has been well documented that both active and passive electrical properties in LVH are altered. Using computer simulations, we have shown that an increased LVM is not the only determinant of QRS complex changes in LVH, as these changes could also be produced without changing the left ventricular mass, implying that these QRS patterns can be present in patients before their LVM exceeds the arbitrary upper normal limits. Our results link the experimental evidence on electrical remodeling with clinical interpretation of ECG changes in patients with LVH and stress the necessity of a complex interpretation of the QRS patterns considering both spatial and nonspatial determinants in terms of the spatial angle theory. We assume that hypertrophic electrical remodeling in combination with changes in left ventricular size and shape explains the variety of ECG patterns as well as the discrepancies between ECG and left ventricular mass.

Aspects of left ventricular morphology outperform left ventricular mass for prediction of QRS duration

BACKGROUND

The knowledge of the case-specific normal QRS duration in each individual is needed when determining the onset, severity and progression of the heart disease. However, large interindividual variability even of the normal QRS duration exists. The aims of the study were to develop a model for prediction of normal QRS complex duration and to test it on healthy individuals.

METHODS

The study population of healthy adult volunteers was divided into a sample for development of a prediction model (n = 63) and a testing sample (n = 30). Magnetic resonance imaging data were used to assess anatomical characteristics of the left ventricle: the angle between papillary muscles (PM(A)), the length of the left ventricle (LV(L)) and left ventricular mass (LV(M)). Twelve-lead electrocardiogram (ECG) was used for measurement of the QRS duration. Multiple linear regression analysis was used to develop a prediction model to estimate the QRS duration. The accuracy of the prediction model was assessed by comparing predicted with measured QRS duration in the test set.

RESULTS

The angle between PM(A) and the length of the LV(L) were statistically significant predictors of QRS duration. Correlation between QRS duration and PM(A) and LV(L) was r = 0.57, P = 0.0001 and r = 0.45, P = 0.0002, respectively. The final model for prediction of the QRS was: QRS(Predicted)= 97 + (0.35 x LV(L)) - (0.45 x PM(A)). The predicted and real QRS duration differed with median 1 ms.

CONCLUSIONS

The model for prediction of QRS duration opens the ability to predict case-specific normal QRS duration. This knowledge can have clinical importance, when determining the normality on case-specific basis.

The decrease in QRS amplitude after aortic valve replacement in patients with aortic valve stenosis

PURPOSE

The purpose of this study was to evaluate the effect of aortic valve replacement on electrocardiogram (ECG) in patients with aortic valve stenosis.

METHODS

Serial 12-lead ECGs were obtained in 15 patients with aortic valve stenosis who underwent aortic valve replacement. Three ECG indexes for left ventricular hypertrophy were manually measured in each ECG: Sokolow-Lyon index (sum of S wave in V(1) and R wave in V(5)), Cornell voltage index (sum of R wave in aVL and S wave in V(3)), and Gubner index (sum of R wave in I and S wave in III).

RESULTS

After aortic valve replacement, Sokolow-Lyon index gradually decreased during 2 years (51.1 +/- 17.9 to 34.8 +/- 12.5 mm, P < .01). Cornell voltage index (25.6 +/- 7.0 to 15.0 +/- 4.8 mm, P < .01) and Gubner index (15.8 +/- 7.6 to 10.3 +/- 5.5 mm, P < .01) also gradually decreased during 2 years. ST depression in V(6) was found in 14 patients (93%) before aortic valve replacement. It resolved in 9 of 14 patients during 2 years.

CONCLUSIONS

Electrocardiographic evidence of left ventricular hypertrophy gradually resolved after aortic valve replacement in patients with aortic valve stenosis.