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Left Ventricular Hypertrophy by the Surface ECG
Available online at www.sciencedirect.com
ScienceDirect Journal of Electrocardiology xx (2017) xxx – xxx www.jecgonline.com
Review
Left Ventricular Hypertrophy by the Surface ECG Ljuba Bacharova, MD, DSc, MBA, a, b,⁎ E. Harvey Estes, MD c a International Laser Center, Bratislava, Slovak Republic Institute of Pathophysiology, Medical Faculty of Comenius University, Bratislava, Slovak Republic Emeritus, Department of Community and Family Medicine, Duke University Medical Center Durham, NC, USA b
c
Abstract
Left ventricular hypertrophy (LVH) is defined as an increase in left ventricular mass (LVM) associated with structural changes of myocardium. The increase in LVM and associated changes are associated with changes in depolarization and repolarization, manifested as a variety of altered QRS and T patterns. Increased QRS voltage has been considered to be a specific ECG finding in LVH, and ECG criteria based on this increased QRS voltage are generally recommended. These ECG changes are also predictive of adverse cardiovascular outcomes. However, it must also be noted that the majority of patients with increased LVM do not have increased QRS voltage. While this is often considered a limitation of ECG in LVH diagnosis, the authors of this minireview consider it more likely that the electrical effects, represented in the altered ECG, and the increased LVM are independent effects, associated by virtue of their common relationship with an underlying pathologic state. This revised view challenges cardiologists and electrocardiologists to explore the interrelationships between electrical, biochemical, and mechanical alterations of myocardial remodeling seen with heart disease, to advance our understanding of this process and its effects, including the evolution of the ECG changes known as “LVH”. © 2017 Elsevier Inc. All rights reserved.
Keywords:
Left ventricular hypertrophy; ECG; QRS complex; Electrical remodeling; Change in paradigm
Contents Left ventricular hypertrophy. . . . . . . . . . Other information provided by ECG . . . . . Predictive value of the ECG-LVH . . . . The effect of impaired electrical properties Conclusion . . . . . . . . . . . . . . . . . . References
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . on the QRS complex. . . . . . . . . . . . .
The ECG diagnosis of left ventricular hypertrophy (LVH) has been a continuous challenge for electrocardiographers for more than a hundred years, with fluctuating intensity of interest. At the beginning, in a time with limited diagnostic possibilities, there were high expectations based on the high specificity. Introduction of non-invasive imaging methods (echocardiography, cardiac magnetic resonance) led to a decrease in interest, as attention shifted to these imaging methods, with their demonstrated superiority in sensitivity
⁎ Corresponding author at: International Laser Center, Ilkovicova 3, 841 04, Bratislava, Slovak Republic. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2017.06.006 0022-0736/© 2017 Elsevier Inc. All rights reserved.
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and specificity in estimating the left ventricular mass. This superiority seems logical, as they estimate size, but fails to explain the other problem, the high incidence of documented increase in size by imaging techniques with no evidence of ECG-LVH (false negative ECG evidence). In addition, ECG-LVH has been documented as an independent cardiovascular risk factor [1]. Originally considered as a “non-modifiable”, it has been shown that it is reversed by antihypertensive therapy and correction of valvular stenosis, both associated with a decrease of unfavorable outcomes [2]. The high specificity and significant modifiable independent CV risk factor maintain the relevance of the ECG diagnosis of LVH as a clinical and diagnostic tool. This minireview critically appraises current
2
L. Bacharova, E.H. Estes / Journal of Electrocardiology xx (2017) xxx–xxx
Table 1 Selected ECG criteria for left ventricular hypertrophy representing the limb leads, precordial leads and the combination of a limb lead and a precordial lead. Gubner Sokolow–Lyon Cornell voltage
RI + SIII ≥ 25 mV SV1 + RV5/V6 N 3.5 mV RaVL + SV3 N 2.8 mV (men) RaVL + SV3 N 2.0 mV (women)
ECG-LVH diagnosis and modifies the future perspective for utilizing the ECG in risk prediction. The traditional ECG criterion for LVH is an increase in QRS voltage, which can be associated with assorted other ECG abnormalities. It is assumed that an enlarged left ventricular mass generates a stronger electrical field, and the resultant electrical forces, oriented posteriorly and leftward, are augmented, with an increased QRS amplitude in appropriate leads [3]. Table 1 presents some selected criteria for LVH based on the QRS amplitude [for the review of ECG-LVH criteria see reference 3]. The ECG criterion that utilizes a combination of non-amplitude, and non-QRS elements is the Romhilt–Estes score (Table 2). It is utilized in most European automated ECG algorithms for LVH diagnosis, usually corrected for extracardiac factors influencing the ECG, such as age, gender, race and body habitus. LVH is defined as a simple measure - increased LVM - so there is an expectation that ECG-LVH should duplicate the same simple measure. This effort has failed. In 2009 the relevant expert panel recommended 35 different criteria [3], but recognized no single criterion as dominant while recognizing their common features of low sensitivity and questionable specificity. The authors believe that, in consideration of ECG-LVH, two fundamental aspects must be recognized: its traditional role in the detection of left ventricular hypertrophy and its newly recognized role in prediction of adverse cardiovascular events.
Left ventricular hypertrophy Left ventricular hypertrophy refers to an increase in the size or mass of left ventricle due to an increase in the size of individual components of myocardium – the cardiomyoTable 2 Romhilt–Estes score. Romhilt–Estes score ≥ 5 points: definite LVH ≥ 4 points: probable LVH Amplitude: R or S wave in limb leads ≥2.0 mV or SV1-2 ≥ 3.0 mV or RV5-6 ≥3.0 mV ST-T segment pattern: ST segment depression in opposite direction to QRS complex without digitalis with digitalis Left atrial involvement Terminal negativity of the P wave in lead V1 ≥ 0.01 mV and ≥ 0.04 s. Left axis deviation ≥ − 30° QRS duration ≥ 0.09 s Intrinsicoid deflection ≥ 0.05 s in V5-V6
cytes. If the size is the measure of interest, imaging methods (e.g. echocardiography, cardiac magnetic resonance) can provide this information. However, left ventricular hypertrophy is associated with other remarkable structural changes including interstitial fibrosis, ischemia, inflammation, apoptosis, all associated with electrical remodeling of myocardium, and all clinically relevant. Electrocardiography by principle does not measure size or mass. It measures the distribution of electrical potentials, measured from the body surface during depolarization and repolarization. The sequence of depolarization and repolarization depends on the electrical properties of myocardium, which in reality does differ in response to disease. But the assumption that mass can be predicted from amplitude resembles the erroneous assumption that the size of a battery can predict its output. One non-constructive consequence of this approach is the categorization of ECG results, using the imaging methods as the gold standard, as true positive/negative, false positive/ negative, leading to serious diagnostic limitations. Considering increased QRS voltage as the sole or principal effect of size/mass, leads to the recognition of only “true positive” ECG findings, representing a minor part of ECG findings in LVH patients, as relevant. The “false negative” results, the majority of patients with LVH, are neglected in the diagnosis. The strongest arguments advanced in favor of continued use of the ECG have been those related to convenience, availability, and low cost, however they are inadequate justification for its use. Other information provided by ECG Predictive value of the ECG-LVH • ECG-LVH is an independent cardiovascular risk factor, independent of increased LVM; Each of the six ECG abnormalities comprising the • Romhilt–Estes score is independently predictive of cardiovascular disease, and each is different from the other five in predicting specific cardiovascular outcomes [4,5]; • The adverse prognostic ability of the ECG in patients with so-called false negative ECG results is also documented [6]. The effect of impaired electrical properties on the QRS complex
3 points
3 points 1 point 3 points
2 points 1 point 1 point
• Computer simulation studies show that global and regional slowing in conduction velocity in the left ventricle causes QRS complex changes similar to those seen in LVH: QRS duration prolongation, leftward shift of electrical axis, and increase in the QRS amplitude in the precordial and/or limb leads [7]. Areas of electrically inactive tissue (i.e. fibrosis) also contribute to this effect. Although considered specific for LVH, they are documented also in other cardiac pathologies affecting myocardial conduction, such as ischemia during the stress test, or in acute coronary syndrome.
L. Bacharova, E.H. Estes / Journal of Electrocardiology xx (2017) xxx–xxx
• Hypertension-induced remodeling as well as hypertrophy are associated with enhanced replacement and diffuse fibrosis [8], consistent with results of experimental and clinical studies. These results suggest that MRI/LVH and ECG/LVH are different, and are related through their common relationship with another underlying and antecedent pathophysiologic state.
Conclusion The increasing evidence suggests that the ECG diagnosis of an increase in LVM is no longer a logical objective. The abnormal ECG patterns currently recognized as ECG-LVH are a strong predictor of future cardiovascular disease and mortality. The other ECG patterns associated with increased LVM need to be recognized, decoded and understood. Understanding the effect of impaired electrical properties can lead to an understanding of the variations in the course of heart failure and create links to understanding LVH as a substrate for arrhythmias, and other clinical puzzles in cardiology. Understanding the ECG findings in LVH is a challenge, and demands that we shift attention from trying to improve prediction of size to that of understanding the meaning of each ECG component. References [1] Sundström J, Lind L, Arnlöv J, Zethelius B, Andrén B, Lithell HO. Echocardiographic and electrocardiographic diagnoses of left ventricular hypertrophy predict mortality independently of each other in a population of elderly men. Circulation 2001;103:2346–51.
3
[2] Bang CN, Devereux RB, Okin PM. Regression of electrocardiographic left ventricular hypertrophy or strain is associated with lower incidence of cardiovascular morbidity and mortality in hypertensive patients independent of blood pressure reduction - A LIFE review. J Electrocardiol 2014;47:630–5. [3] Hancock EW, Deal BJ, Mirvis DM, Okin P, Kligfield P, Gettes LS. AHA/ ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part V: electrocardiogram changes associated with cardiac chamber hypertrophy: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society. Endorsed by the International Society for Computerized Electrocardiology. J Am Coll Cardiol 2009;53:992. [4] Estes EH, Zhang Z-M, Li Y, Tereshchenko LG, Soliman EZ. The Romhilt-Estes left ventricular hypertrophy score and its components predict all-cause mortality in the general population. Am Heart J 2015;170:104–9. [5] Estes EH, Zhang ZM, Li Y, Tereshchenko LG, Soliman EZ. Individual components of the Romhilt-Estes left ventricular hypertrophy score differ in their prediction of cardiovascular events: the Atherosclerosis Risk in Communities (ARIC) study. Am Heart J 2015;170(6):1220–6. [6] Bacharova L, Chen H, Estes EH, Mateasik A, Bluemke D, Lima J, et al. Determinants of discrepancies in detection and comparison of the prognostic significance of left ventricular hypertrophy by electrocardiogram and cardiac magnetic resonance imaging. Am J Cardiol 2015;115:515–22. [7] Bacharova L. Left ventricular hypertrophy: disagreements between increased left ventricular mass and ECG-LVH criteria: the effect of impaired electrical properties of myocardium. J Electrocardiol 2014;47:625–9. [8] Maanja M, Wieslander B, Schlegel TT, Bacharova L, Daya HA, Fridman Y, et al. Diffuse myocardial fibrosis reduces electrocardiographic voltage criteria for left ventricular hypertrophy independent of left ventricular mass. JAHA 2017:e003795.
ScienceDirect Journal of Electrocardiology xx (2017) xxx – xxx www.jecgonline.com
Review
Left Ventricular Hypertrophy by the Surface ECG Ljuba Bacharova, MD, DSc, MBA, a, b,⁎ E. Harvey Estes, MD c a International Laser Center, Bratislava, Slovak Republic Institute of Pathophysiology, Medical Faculty of Comenius University, Bratislava, Slovak Republic Emeritus, Department of Community and Family Medicine, Duke University Medical Center Durham, NC, USA b
c
Abstract
Left ventricular hypertrophy (LVH) is defined as an increase in left ventricular mass (LVM) associated with structural changes of myocardium. The increase in LVM and associated changes are associated with changes in depolarization and repolarization, manifested as a variety of altered QRS and T patterns. Increased QRS voltage has been considered to be a specific ECG finding in LVH, and ECG criteria based on this increased QRS voltage are generally recommended. These ECG changes are also predictive of adverse cardiovascular outcomes. However, it must also be noted that the majority of patients with increased LVM do not have increased QRS voltage. While this is often considered a limitation of ECG in LVH diagnosis, the authors of this minireview consider it more likely that the electrical effects, represented in the altered ECG, and the increased LVM are independent effects, associated by virtue of their common relationship with an underlying pathologic state. This revised view challenges cardiologists and electrocardiologists to explore the interrelationships between electrical, biochemical, and mechanical alterations of myocardial remodeling seen with heart disease, to advance our understanding of this process and its effects, including the evolution of the ECG changes known as “LVH”. © 2017 Elsevier Inc. All rights reserved.
Keywords:
Left ventricular hypertrophy; ECG; QRS complex; Electrical remodeling; Change in paradigm
Contents Left ventricular hypertrophy. . . . . . . . . . Other information provided by ECG . . . . . Predictive value of the ECG-LVH . . . . The effect of impaired electrical properties Conclusion . . . . . . . . . . . . . . . . . . References
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . on the QRS complex. . . . . . . . . . . . .
The ECG diagnosis of left ventricular hypertrophy (LVH) has been a continuous challenge for electrocardiographers for more than a hundred years, with fluctuating intensity of interest. At the beginning, in a time with limited diagnostic possibilities, there were high expectations based on the high specificity. Introduction of non-invasive imaging methods (echocardiography, cardiac magnetic resonance) led to a decrease in interest, as attention shifted to these imaging methods, with their demonstrated superiority in sensitivity
⁎ Corresponding author at: International Laser Center, Ilkovicova 3, 841 04, Bratislava, Slovak Republic. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2017.06.006 0022-0736/© 2017 Elsevier Inc. All rights reserved.
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and specificity in estimating the left ventricular mass. This superiority seems logical, as they estimate size, but fails to explain the other problem, the high incidence of documented increase in size by imaging techniques with no evidence of ECG-LVH (false negative ECG evidence). In addition, ECG-LVH has been documented as an independent cardiovascular risk factor [1]. Originally considered as a “non-modifiable”, it has been shown that it is reversed by antihypertensive therapy and correction of valvular stenosis, both associated with a decrease of unfavorable outcomes [2]. The high specificity and significant modifiable independent CV risk factor maintain the relevance of the ECG diagnosis of LVH as a clinical and diagnostic tool. This minireview critically appraises current
2
L. Bacharova, E.H. Estes / Journal of Electrocardiology xx (2017) xxx–xxx
Table 1 Selected ECG criteria for left ventricular hypertrophy representing the limb leads, precordial leads and the combination of a limb lead and a precordial lead. Gubner Sokolow–Lyon Cornell voltage
RI + SIII ≥ 25 mV SV1 + RV5/V6 N 3.5 mV RaVL + SV3 N 2.8 mV (men) RaVL + SV3 N 2.0 mV (women)
ECG-LVH diagnosis and modifies the future perspective for utilizing the ECG in risk prediction. The traditional ECG criterion for LVH is an increase in QRS voltage, which can be associated with assorted other ECG abnormalities. It is assumed that an enlarged left ventricular mass generates a stronger electrical field, and the resultant electrical forces, oriented posteriorly and leftward, are augmented, with an increased QRS amplitude in appropriate leads [3]. Table 1 presents some selected criteria for LVH based on the QRS amplitude [for the review of ECG-LVH criteria see reference 3]. The ECG criterion that utilizes a combination of non-amplitude, and non-QRS elements is the Romhilt–Estes score (Table 2). It is utilized in most European automated ECG algorithms for LVH diagnosis, usually corrected for extracardiac factors influencing the ECG, such as age, gender, race and body habitus. LVH is defined as a simple measure - increased LVM - so there is an expectation that ECG-LVH should duplicate the same simple measure. This effort has failed. In 2009 the relevant expert panel recommended 35 different criteria [3], but recognized no single criterion as dominant while recognizing their common features of low sensitivity and questionable specificity. The authors believe that, in consideration of ECG-LVH, two fundamental aspects must be recognized: its traditional role in the detection of left ventricular hypertrophy and its newly recognized role in prediction of adverse cardiovascular events.
Left ventricular hypertrophy Left ventricular hypertrophy refers to an increase in the size or mass of left ventricle due to an increase in the size of individual components of myocardium – the cardiomyoTable 2 Romhilt–Estes score. Romhilt–Estes score ≥ 5 points: definite LVH ≥ 4 points: probable LVH Amplitude: R or S wave in limb leads ≥2.0 mV or SV1-2 ≥ 3.0 mV or RV5-6 ≥3.0 mV ST-T segment pattern: ST segment depression in opposite direction to QRS complex without digitalis with digitalis Left atrial involvement Terminal negativity of the P wave in lead V1 ≥ 0.01 mV and ≥ 0.04 s. Left axis deviation ≥ − 30° QRS duration ≥ 0.09 s Intrinsicoid deflection ≥ 0.05 s in V5-V6
cytes. If the size is the measure of interest, imaging methods (e.g. echocardiography, cardiac magnetic resonance) can provide this information. However, left ventricular hypertrophy is associated with other remarkable structural changes including interstitial fibrosis, ischemia, inflammation, apoptosis, all associated with electrical remodeling of myocardium, and all clinically relevant. Electrocardiography by principle does not measure size or mass. It measures the distribution of electrical potentials, measured from the body surface during depolarization and repolarization. The sequence of depolarization and repolarization depends on the electrical properties of myocardium, which in reality does differ in response to disease. But the assumption that mass can be predicted from amplitude resembles the erroneous assumption that the size of a battery can predict its output. One non-constructive consequence of this approach is the categorization of ECG results, using the imaging methods as the gold standard, as true positive/negative, false positive/ negative, leading to serious diagnostic limitations. Considering increased QRS voltage as the sole or principal effect of size/mass, leads to the recognition of only “true positive” ECG findings, representing a minor part of ECG findings in LVH patients, as relevant. The “false negative” results, the majority of patients with LVH, are neglected in the diagnosis. The strongest arguments advanced in favor of continued use of the ECG have been those related to convenience, availability, and low cost, however they are inadequate justification for its use. Other information provided by ECG Predictive value of the ECG-LVH • ECG-LVH is an independent cardiovascular risk factor, independent of increased LVM; Each of the six ECG abnormalities comprising the • Romhilt–Estes score is independently predictive of cardiovascular disease, and each is different from the other five in predicting specific cardiovascular outcomes [4,5]; • The adverse prognostic ability of the ECG in patients with so-called false negative ECG results is also documented [6]. The effect of impaired electrical properties on the QRS complex
3 points
3 points 1 point 3 points
2 points 1 point 1 point
• Computer simulation studies show that global and regional slowing in conduction velocity in the left ventricle causes QRS complex changes similar to those seen in LVH: QRS duration prolongation, leftward shift of electrical axis, and increase in the QRS amplitude in the precordial and/or limb leads [7]. Areas of electrically inactive tissue (i.e. fibrosis) also contribute to this effect. Although considered specific for LVH, they are documented also in other cardiac pathologies affecting myocardial conduction, such as ischemia during the stress test, or in acute coronary syndrome.
L. Bacharova, E.H. Estes / Journal of Electrocardiology xx (2017) xxx–xxx
• Hypertension-induced remodeling as well as hypertrophy are associated with enhanced replacement and diffuse fibrosis [8], consistent with results of experimental and clinical studies. These results suggest that MRI/LVH and ECG/LVH are different, and are related through their common relationship with another underlying and antecedent pathophysiologic state.
Conclusion The increasing evidence suggests that the ECG diagnosis of an increase in LVM is no longer a logical objective. The abnormal ECG patterns currently recognized as ECG-LVH are a strong predictor of future cardiovascular disease and mortality. The other ECG patterns associated with increased LVM need to be recognized, decoded and understood. Understanding the effect of impaired electrical properties can lead to an understanding of the variations in the course of heart failure and create links to understanding LVH as a substrate for arrhythmias, and other clinical puzzles in cardiology. Understanding the ECG findings in LVH is a challenge, and demands that we shift attention from trying to improve prediction of size to that of understanding the meaning of each ECG component. References [1] Sundström J, Lind L, Arnlöv J, Zethelius B, Andrén B, Lithell HO. Echocardiographic and electrocardiographic diagnoses of left ventricular hypertrophy predict mortality independently of each other in a population of elderly men. Circulation 2001;103:2346–51.
3
[2] Bang CN, Devereux RB, Okin PM. Regression of electrocardiographic left ventricular hypertrophy or strain is associated with lower incidence of cardiovascular morbidity and mortality in hypertensive patients independent of blood pressure reduction - A LIFE review. J Electrocardiol 2014;47:630–5. [3] Hancock EW, Deal BJ, Mirvis DM, Okin P, Kligfield P, Gettes LS. AHA/ ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part V: electrocardiogram changes associated with cardiac chamber hypertrophy: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society. Endorsed by the International Society for Computerized Electrocardiology. J Am Coll Cardiol 2009;53:992. [4] Estes EH, Zhang Z-M, Li Y, Tereshchenko LG, Soliman EZ. The Romhilt-Estes left ventricular hypertrophy score and its components predict all-cause mortality in the general population. Am Heart J 2015;170:104–9. [5] Estes EH, Zhang ZM, Li Y, Tereshchenko LG, Soliman EZ. Individual components of the Romhilt-Estes left ventricular hypertrophy score differ in their prediction of cardiovascular events: the Atherosclerosis Risk in Communities (ARIC) study. Am Heart J 2015;170(6):1220–6. [6] Bacharova L, Chen H, Estes EH, Mateasik A, Bluemke D, Lima J, et al. Determinants of discrepancies in detection and comparison of the prognostic significance of left ventricular hypertrophy by electrocardiogram and cardiac magnetic resonance imaging. Am J Cardiol 2015;115:515–22. [7] Bacharova L. Left ventricular hypertrophy: disagreements between increased left ventricular mass and ECG-LVH criteria: the effect of impaired electrical properties of myocardium. J Electrocardiol 2014;47:625–9. [8] Maanja M, Wieslander B, Schlegel TT, Bacharova L, Daya HA, Fridman Y, et al. Diffuse myocardial fibrosis reduces electrocardiographic voltage criteria for left ventricular hypertrophy independent of left ventricular mass. JAHA 2017:e003795.