Theoretical considerations on the electrocardiogram of ventricular hypertrophy

Correlation between global longitudinal strain and QRS voltage on electrocardiogram in patients with left ventricular hypertrophy

PURPOSE

Left ventricular hypertrophy (LVH) is as an independent risk factor. Discrepancies were reported between LV mass (LVM) estimated by echocardiography and electrocardiography (ECG) findings. We hypothesized that QRS voltage criteria may reflect not only anatomical changes (LVM) but also changes in LV function and we tested the relationship between QRS voltage and echocardiographic parameters of LV function in patients (pts) with different types of LVH.

METHODS

We prospectively enrolled pts with LVH and preserved ejection fraction (LVEF >50%): 20 pts with isolated arterial hypertension, HTN, 20 pts with severe aortic stenosis, AS (indexed aortic valve area <0.6 cm(2)/m(2)), and 20 pts with symmetric hypertrophic cardiomyopathy, HCM. Standard 12-lead ECG (including Sokolow and Cornell voltage indices) and a comprehensive two-dimensional (2D) echocardiography were performed in all. Left ventricular mass was calculated according to Devereux formula. Global longitudinal strain (GLS) was assessed by speckle tracking echocardiography.

RESULTS

A significant correlation was found between both ECG indices and LVM assessed by echocardiography. Moreover, significant correlations were found between Sokolow-Lyon voltage and LVEF (r = 0.26; P = 0.03), GLS (r = 0.59; P < 0.001) and E/e' average (r = 0.43; P < 0.001). Cornell voltage index correlated significantly only with GLS. In multivariable analysis GLS emerged as the only independent correlate of both Sokolow-Lyon (ß = 0.6, P < 0.001) and Cornell voltage indices (ß = 0.45, P < 0.001).

CONCLUSION

These findings suggest that in pts with LVH, ECG should no longer be used only as a surrogate method for LVM estimation (structural changes only), but rather as an investigation complementary to imaging, incorporating information on overall LV remodeling (changes in structure and function).

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

Electrical remodeling in advanced stages of cardiovascular diseases creates a substrate for triggering and maintenance of arrhythmias. The electrical remodeling is a continuous process initiated already in the early stages of cardiological pathology. The aim of this opinion article was to discuss the changes in electrical properties of myocardium in left ventricular hypertrophy (LVH), with special focus on its early stage, as well as their possible reflection in the QRS amplitude of the electrocardiogram. It critically appraises the classical hypothesis related to the QRS voltage changes in LVH. The hypothesis of the relative voltage deficit is discussed in the context of supporting evidence from clinical studies, animal experiments, and simulation studies. The underlying determinants of electrical impulse propagation which may explain discrepancies between "normal" ECG findings and increased left ventricular size/mass in LVH are reviewed.

Electrocardiographic diagnosis of left ventricular hypertrophy: is the method obsolete or should the hypothesis be reconsidered?

The current ECG diagnosis of LVH is based on QRS voltage criteria and aims to estimate left ventricular mass. Its underlying hypothesis includes unstated assumptions about the non-spatial determinants of QRS voltage;that the electrical properties of hypertrophied myocardium do not differ from those healthy myocardium, and that they are not changed in the course of developing LVH. Since these two assumptions are not true, the performance of the voltage criteria is limited and is reflected in the high number of so-called false negative ECG results, as well as their low sensitivity. The reconsidered hypothesis is based on a more complex understanding of LVH and on the analysis of information provided by electrocardiography. It considers false negative results for LVH diagnosis as a relative voltage deficit, and introduces a new parameter for its quantification: the specific potential (the relative QRS voltage).The relative voltage deficit is related to changes of active and passive electrical properties (electrophysiological remodelling) of the hypertrophied myocardium. This new hypothesis also takes into account changes of the relative QRS voltage in different stages of LVH. The potential of this concept is its usefulness as a parameter in the frame of diagnostics of LVH, of diffuse changes of myocardium, in cardiovascular risk assessment, and well as for evaluation of the effects of therapy.