Techniques for the determination of left ventricular mass by signal-averaged electrocardiography

The standard ECG correlates poorly with LV mass. The SAECG precisely measures myocardial energy and may allow more exact noninvasive assessment of LV mass. A commercially available system (Corazonix Predictor I) was tested for its ability to reproduce and measure known input energy in square wave and QRS waveforms, using frequency bandwidths different from those used for late potential analysis. A test group of 15 patients was studied to determine optimum filter type and bandwidth for comparison of SAECG energy measurement versus LV mass as determined by echocardiography (Penn conversion) and LV hypertrophy via standard ECG criteria. The best means of energy measurement were maximum and total RMS voltage and the integral of the area under the QRS curve. Optimum correlation with echocardiography was seen with a bidirectional band-pass filter of 5 to 250 Hz applied either to the vector sum of the three orthogonal leads or to the Z lead alone (r values 0.61 to 0.73), which was equal to or superior to standard ECG LV hypertrophy determinants. A second group of 20 patients was studied prospectively to confirm these findings, which yielded similar results. Conclusion: (1) the SAECG when appropriately modified serves as a rapid noninvasive assessment of LV mass. (2) These modifications must examine the entire duration and energy spectrum of the surface ECG and not just the region of late potentials. (3) Very low frequencies (below 5 Hz) must be excluded to eliminate the energy present due to DC offset voltage.     

Spectral analysis of signal-averaged electrocardiograms in patients with idiopathic ventricular tachycardia of left ventricular origin.

BACKGROUND. The signal-averaged ECG has been used to detect late potentials, and it is considered a noninvasive marker for areas of slow conduction requisite for reentrant arrhythmia. Late potentials are not usually found in patients with idiopathic ventricular tachycardia (VT); nevertheless, fragmented electrograms are often recorded in those patients during endocardial mapping. The purpose of this study was to investigate the spectral content of the signal-averaged ECGs with use of fast Fourier transform analysis (FFT) in patients with idiopathic VT of left ventricular origin. METHODS AND RESULTS. Signal-averaged ECGs were recorded in 12 patients with idiopathic VT originating from the left ventricle (group 1) and 25 age-matched normal volunteers (group 2). Frequency analysis with FFT was performed with a Blackman-Harris window in a segment length of 120 msec from 40 msec before the end of the QRS complex, and the frequency spectrum was displayed in a three-dimensional graph. Area ratio 1 (area of 20-50 Hz/area of 10-50 Hz) and area ratio 2 (area of 40-100 Hz/area of 0-40 Hz) were calculated in all subjects. Late potentials defined by the time domain were negative in all subjects. The area ratios of group 1 were significantly higher than those of group 2. High-frequency components in the three-dimensional graph were confined within the QRS complex. CONCLUSIONS. These results suggest that frequency analysis of signal-averaged ECGs with FFT is an available method for detecting the high-frequency component within the QRS complex in some patients with idiopathic VT of left ventricular origin.     

Correlation of electrocardiographic left ventricular hypertrophy criteria with left ventricular mass by echocardiogram in obese hypertensive patients

Introduction

Left ventricular hypertrophy (LVH) and obesity are important cardiovascular risk factors. This study evaluates the influence of obesity on the diagnostic performance of the most used electrocardiographic criteria for LVH in hypertensive patients.

Methods

One thousand two hundred four outpatients from the Hypertensive Unit of the Hospital São Paulo, São Paulo, SP, Brazil, were studied. All underwent 12-lead electrocardiogram and echocardiogram. The most known electrocardiographic criteria for LVH were assessed and compared with the left ventricular mass index obtained by echocardiogram in obese and nonobese groups of hypertensive patients.

Results

The population's mean age was 57.4 ± 4.7 years; 351 were men (29.1%) and 853 women (70.8%). Cornell voltage, Cornell duration, Sokolow-Lyon voltage, Romhilt-Estes criteria, and R wave in aVL 11 mm or higher showed a positive correlation with left ventricular mass index (P < .05). Notwithstanding, there were no changes regarding specificity for obese or nonobese characteristics. However, sensitivity had a statistically significant decrease in obese patients in regard to Sokolow-Lyon voltage and Romhilt-Estes criteria and strain pattern (P < .05).

Conclusion

Cornell voltage and Cornell duration criteria, Perugia score, R wave in aVL, and QTc variable had no significant changes in diagnostic sensitivity in the obese patients.     

Race- and sex-specific ECG models for left ventricular mass in older populations. Factors influencing overestimation of left ventricular hypertrophy prevalence by ECG criteria in African-Americans

The validity of the reported high prevalence of left ventricular hypertrophy (LVH) among African-American men and women has been questioned owing to conflicting echocardiographic evidence. We used echocardiographic left ventricular mass (LVM) from M-mode measurements to evaluate associations between LVM, body size, and electrocardiographic (ECG) variables in 3,627 white and African-American men and women 65 years of age and older who were participants of the Cardiovascular Health Study (CHS), a multicenter cohort study of risk factors for coronary heart disease and stroke. ECG amplitudes used in LVH criteria were substantially higher in African-Americans, with apparent LVH prevalence 2 to 3 times higher in African American men and women than in white men and women, although there was no significant racial difference in echocardiographic LVM. The higher apparent LVH prevalence by Sokolow-Lyon criteria in African-American men is in part owing to smaller lateral chest diameter. In women, reasons for racial differences in ECG LVH prevalence remain largely unexplained although a small part of the excess LVH in African-American women by the Sokolow-Lyon criteria appears to be owing to a larger lateral chest semidiameter in white women. ECG variables alone were too inaccurate for LVM prediction, and it was necessary to incorporate in all ECG models body weight that was properly adjusted for race and sex. This resulted in modest LVM prediction accuracy, with R-square values ranging from .22 to .36. Race- and sex-specific ECG models introduced for LVM estimation with an appropriate adjustment for body size differences are expected to facilitate evaluation of LVH status in contrasting racial population groups.     

Ultrastructural analysis of left ventricular hypertrophy in rabbits

Ultrastructural changes resulting from gradual aortic constriction were quantitated in a model for cardiac hypertrophy. Gradual aortic stenosis was produced in rabbits by swelling of an Ameroid clip. Ultrastructural, biochemical and physiological changes were observed for each heart. The ultrastructure of mitochondria in hypertrophied but non-failing hearts was normal. The respiratory activity of mitochondria isolated from these same hearts was increased. Profiles of granular endoplasmic reticulum and free ribosomes, widening of Z bands and distortions of intercalated discs were observed in hypertrophied hearts and were interpreted as evidence of synthesis of new functional components. However, different cell components increased disproportionately. Morphometric analysis revealed significant decreases in mitochondrial fractional volume (0.35 ± 0.01, P < 0.001) and mitochondria/myofibril ratios (0.59 < 0.02, P < 0.001). The results suggest that increased work load may induce a further deleterious change in the ratio between mitochondrial units and myofibril units with may lead to decompensation and failure. The ultrastructural changes observed in this model may be of interest since the model closely mimics the gradual onset of the hypertrophic response in humans.     

Frequency analysis of signal-averaged electrocardiogram in patients with right ventricular tachycardia.

OBJECTIVES. The purpose of this study was to analyze the frequency content of signal-averaged electrocardiograms (ECGs) in patients with idiopathic ventricular tachycardia of right ventricular origin and in patients with arrhythmogenic right ventricular dysplasia. BACKGROUND. The late potentials in the time domains are usually found in patients with arrhythmogenic right ventricular dysplasia. They are not usually found in patients with idiopathic ventricular tachycardia of right ventricular origin. METHODS. Fast Fourier transform analysis of signal-averaged ECGs was performed with the use of a Blackman-Harris window in 43 subjects: 20 normal volunteers (group I), 12 patients with idiopathic ventricular tachycardia of right ventricular origin (group II) and 11 patients with arrhythmogenic right ventricular dysplasia (group III), and the frequency spectrum was displayed in a three-dimensional graph. Area ratio (ratio of the area under the spectral plot from 40 to 120 Hz to the area from 0 to 120 Hz) was calculated in all subjects. RESULTS. Area ratio was significantly higher in group II than in group I (243 +/- 45 vs. 196 +/- 15, p < 0.01) and significantly higher in group III (396 +/- 51) than in group I or II (p < 0.001). The high frequency components in group II were confined within the QRS complex in the three-dimensional graph, whereas those in group III extended outside the QRS complex. CONCLUSIONS. Frequency analysis of the signal-averaged ECG with fast Fourier transform analysis can detect the high frequency components in patients with right ventricular tachycardia, including idiopathic ventricular tachycardia and arrhythmogenic right ventricular dysplasia.     

ECG alterations with progressive left ventricular hypertrophy in spontaneous hypertension.

Although many ECG criteria exist for diagnosis of left ventricular hypertrophy (LVH) in hypertensive man, little is known of which specific ECG changes accompany progression of LVH with duration of hypertension. The spontaneously hypertensive rat (SHR) provides the best animal model thus far developed for studying this process since these animals demonstrate a progressive increase in left ventricular/body weight ratio with age. Electrocardiograms were performed under light ether anesthesia in four age groups of SHR and two normotensive Wistar strains (NR and WKY). Analysis of variance for two factors (rat strain and age) revealed progressively increased QRS and P-wave duration and delay in intrinsicoid deflection in SHR (p less than 0.001). Bipeak P-wave notching was also noted in SHR similar to left atrial abnormality in hypertensive man. Thus, specific ECG indices can be identified in association with the known progressive increase in left ventricular mass in SHR and should provide a better means to understand evolving ECG changes in LVH.     

Relationship between signal-averaged electrocardiography and dangerous ventricular arrhythmias in patients with left ventricular aneurysm after myocardial infarction.

We performed signal-averaged electrocardiography (SAECG) and Holter monitoring, and subsequently followed-up 53 ambulatory patients with left ventricular aneurysm (LVA) after myocardial infarction (MI). A history of spontaneous episodes of sustained ventricular tachycardia (VT) was also analysed. Out of 53 patients, 25 (47%) had an abnormal SAECG. Abnormal SAECG correctly identified nine out of 10 cases with a history of sustained VT. Complex ventricular arrhythmias were detected on Holter monitoring in 23 patients: in five out of 28 with normal SAECG (18%) and in 18 out of 25 with abnormal SAECG (72%) (P less than 0.001). During follow-up (mean 19 months) sustained VT and/or sudden cardiac death (SCD) occurred in eight cases, out of which seven had an abnormal SAECG. The negative predictive value of SAECG (no VT or SCD during follow-up) was very high, 96%, similar to the negative predictive value of a history of sustained VT (93%). Using multivariate analysis only a history of sustained VT was an independent factor in predicting the outcome of patients in this study. We conclude that an abnormal SAECG identifies those post infarction patients with LVA who are prone to complex ventricular arrhythmias. A normal SAECG and an absence of a history of sustained VT strongly indicate that the risk of developing arrhythmic events is very low.     

Mean QRS, ventricular gradient and left ventricular mass in patients with eccentric left ventricular hypertrophy.

The spatial ventricular gradient (G) and the mean QRS-T angle were examined in 12 patients with angiographically determined eccentric left ventricular hypertrophy (LVH), as compared with 12 normal control subjects. In these 24 patients, a high significant correlation (r = 0.88) was obtained between the magnitude of the spatial mean QRS and LV mass. Although correlations were obtained between the magnitude of the spatial G or the spatial mean QRS-T angle and LV mass, they were lower (r = 0.56, 0.71 respectively). The magnitude of the spatial G (0.190 +/- 0.049 MVSec) in the eccentric LVH group increased significantly (p less than 0.001) in comparison with the control value (0.105 +/- 0.032 mVSec), while in the eccentric LVH group, decreased G/QRS (p less than 0.02), decreased T/QRS (p less than 0.05), and increased QRS-T angle (p less than 0.02) were observed. Furthermore, decreased G/QRS and widening of the QRS-T angle were observed in cases of LVH only. In cases of mild or moderate LVH, normal G/QRS ratios with definitely increased G magnitude and normal QRS-T angle were observed. It is concluded that the magnitude of the spatial mean QRS closely relates to an increase in LV mass. Therefore, should the magnitude of G increase proportionally to an increase in total muscle volume in ideal hypertrophy, then the widening of the QRS-T angle observed in LVH would be due not only to the large ARS complex but also to an alteration in the ventricular gradient.     

Long-term follow-up of the signal-averaged ECG in arrhythmogenic right ventricular cardiomyopathy: correlation with arrhythmic events and echocardiographic findings.

AIMS: The aims of our study were to evaluate late potential changes during long-term follow-up in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and to correlate these results with echocardiographic findings and sustained ventricular tachycardia (VT) occurrence. METHODS AND RESULTS: We studied 31 patients (22 males and 9 females; mean age 29+/-16) during 8 years of follow-up by signal-averaged ECG (SAECG) and echocardiography. Ten subjects experienced episodes of sustained VT. During follow-up, all the SAECG parameters showed a progressive significant increase in late potentials. In contrast, echocardiographic indices did not show evidence of relevant modifications. Patients with sustained VT were characterized by significantly lower left and right ventricular ejection fractions, longer values of filtered QRS at 25/40/80-250 Hz filters, and longer high-frequency low-amplitude (HFLA) signals at 25-250 Hz at baseline. The analysis of SAECG modification during follow-up indicated that only HFLA signals at 25-250 Hz increased significantly in the sustained VT group. CONCLUSION: We detected a progressive increase in delayed ventricular conduction by SAECG not associated with significant echocardiographic changes. Therefore, the conduction disturbance seems to increase independently from anatomical alterations. The baseline SAECG and echocardiographic parameters, more than their modifications during follow-up, appear to be useful in identifying patients with sustained VT.     

特发性室性心动过速患者的信号平均心电图频域分析

为进一步明确特发性室性心动过速的病因及机制,对18例左心室特发性室性心动过速、8例右心室特发性室性心动过速患者及17例正常对照者进行信号平均心电图检查,并对于其时域、频域结果进行分析。结果显示:时域分析:左、右心室特发性室性心动过速组中各1例晚电位阳性,正常对照组无晚电位阳性。频域分析:左、右心室特发性室性心动过速组AR_1(20—50Hz/0—50Hz)的平均值(328.77±43.81,338.05±43.81)均高于对照组(300.08±23.75,P<0.05);左、右心室特发性室性心动过速组的AR_2(40—120Hz/0—120Hz)的平均值(119.71±34.69,115.22±27.74)显著高于对照组(90.74±16.32,P<0.05)。频谱分析发现部分特发性室性心动过速患者QRS终末波所含的高频成分增加,可能存在轻度心肌传导异常。     

ST 段抬高型急性心肌梗死患者的心电图表现与近期左心室功能的相关性研究

目的：探讨 ST 段抬高型急性心肌梗死（ST-segment elevation acute myocardial infarc-tion,STEAMI）患者的心电图表现与近期左心室功能的相关性。方法对60例 STEAMI 患者在入院时及三个月后行心电图与超声心动图检查,分析结果。结果患者 V1～V6导联中 ST段抬高幅度之和1．72 mV,R 波振幅之和3．28 mV,Q 波振幅之和2．83 mV,Q 波导联数为5个,ST 段抬高最大振幅值4．32 mV,左心室舒张末期内径（LVEDd）为51．34 mm,急性期左室射血分数（LVEF）为56．19％;Killip 分级1级32例、2级15例、3级10例、4级3例;三个月后LVEDd、LVEF 分别为45．87 mm 和59．20％;ST 段抬高幅度之和、Q 波振幅之和、Q 波导联数与 Killip 分级、三个月后 LVEDd 呈正相关（r ＝0．54、0．52）,与三个月后 LVEF 呈负相关（r ＝－0．56）,R 波振幅之和与三个月后 LVEDd 呈负相关（r ＝－0．61）,与三个月后 LVEF 呈正相关（r ＝0．46）。结论STEAMI 患者 ST 段抬高幅度、R 波振幅、Q 波振幅、Q 波导联数等与左心室功能关系密切,可用于患者左心室功能的近期预测。     

Validity of the ECG diagnosis of left ventricular hypertrophy in normotensive and moderately hypertensive men when using the echocardiographic assessment of left ventricular mass index as reference.

The diagnostic validity of ECG criteria for left ventricular hypertrophy (LVH) was assessed in 100 men aged 22-64 (mean 47) years with moderate hypertension (Group 1) and 95 age-matched normotensive men (Group 2) using echocardiographic recordings of LV mass index (MI) as reference. A diagnosis of LVH was made in subjects with LVMI greater than or equal to 125 g/m2. Mean LVMI was 126 +/- 34 g/m2 in Group 1 vs. 100 +/- g/m2 in Group 2 (P less than 0.001), and the prevalence of LVH was 48% and 11% respectively (P less than 0.001). The mean ECG voltage according to Sokolow-Lyon (S-L) was 28 +/- 8 mm in Group 1 and 27 +/- 7 mm in Group 2 (NS); with 19% having LVH in Group 1 and 14% in Group 2 (NS). Using the Cornell criterion Group 1 had on average 15 +/- 6 mm vs. 12 +/- 5 mm in Group 2 (P less than 0.001), but only two Group 1 patients had LVH. In Group 2 a significant negative correlation between age and S-L voltage was found (r = 0.33, P less than 0.001). LVMI was not correlated with any of the two voltage criteria using linear regression analysis whereas multiple regression analysis revealed a weak, but significant correlation between LVMI and S-L voltage in Group 1 (t = 2.06, P = 0.04). No subject had LV strain pattern or LVH according to the Romhilt Estes point score system. In the assessment of possible LVH in normal or moderately hypertensive men less than 65-70 years of age, ECG has limited value.     

Relationship between signal-averaged electrocardiography and dangerous ventricular arrhythmias in patients with left ventricular aneurysm after myocardial infarction

We performed signal-averaged electrocardiography (SAECG) andHolter monitoring, and subsequently followed-up 53 ambulatorypatients with left ventricular aneurysm (LVA) after myocardialinfarction (MI). A history of spontaneous episodes of sustainedventricular tachycardia (VT) v also analysed. Out of 53 patients, 25 (47%) had an abnormal SAECG. AbnormalSAECG correctly identified nine out of 10 cases with a historyof sustained VT. Complex ventricular arrhythmias were detectedon Holler monitoring in 23 patients: in five out of 28 withnormal SAECG (18%) and in 18 out of 25 with abnormal SAECG (72%)(P<0001). During follow-up (mean 19 months) sustained VTand/or sudden cardiac death (SCD) occurred in eight cases, outof which seven had an abnormal SAECG. The negative predictivevalue of SAECG (no VT or SCD during follow-up) was very high,96%. similar to the negative predictive value of a history ofsustained VT (93%). Using multivariate analysis only a historyof sustained VT twas an independent factor in predicting theoutcome of patients in this study. We conclude that an abnormal SAECG identifies those post infarctionpatients with LVA who are prone to complex ventricular arrhvthmias.A normal SAECG and an absence of a history of sustained VT stronglyindicate that the risk of developing arrhythmic events is verylow.     

Quantitative analysis of the signal-averaged QRS in patients with arrhythmogenic right ventricular dysplasia

Temporal signal averaging of the surface QRS (VI + V3 + V5)was performed in 16 patients with arrhythmogenic right ventriculardysplasia and in 16 normal subjects. The differences betweenARVD patients and normals were large for the filtered QRS duration(FQRSd) (146.2±18.9 vs. 91.8±4.1ms, P<000001),the late potential duration (LPd) (83.5±23.3 ms vs. 23.6±4.6ms,P< 0.00001), the LPd/ FQRSd ratio (53.9± 10.1% vs.25.8±5.1%, P <0.00001), the filtered QRS amplitude(234.0±61.1µV vs. 429±942 fiV, P <0001),and the root mean square voltage of the signals in the terminal40 and 50 ms of the FQRS (RMS40 and RMS50) (18.4± 10.0µVvs. 118.4±49.8p.V, P<0.0005 and 27.9± 19.2µVvs. 217.0±66.3fiV, P<0000002). RMS50 <40µVdiscriminated best between ARVD and normals (81% sensitivityand 100% specificity). The right-sided predominance of the abnormalitiesin ARVD was demonstrated by the significantly longer FQRSd andLPd, and the higher ratio LPd/FQRSd in right than in left precordialleads. The arrhythmia susceptibility did not seem to influencethe presence of or properties ofLP in the ARVD group. Patientswith multiple QRS morphologies during ventricular tachycardia(VT) had, compared with patients with only one type of VT, longerLPd (108.3 ±46.4 ms vs. 64.2 ±31.7 ms, P<0.02)and lower RMS40 voltage (9.4±9.9 µV vs. 25.4±21.6µV, P<0.05). The relative heart volume was positivelycorrelated with delayed activity, but an enlarged heart wasnot apre-requisitefor the presence ofLP. The method thus identifieschanges which are specific to ARVD. The findings indicate thatcertain electrical or morphological conditions are requiredfor the occurrence of arrhythmias.     

ECG manifestations of left ventricular electrical remodeling

Research and thinking about the electrocardiographic manifestations of left ventricular hypertrophy has been constrained by a limited conceptual model of the process: heart disease produces chamber enlargement (increased mass), which in turn produces an altered electrocardiogram. The process is much more complex than can be represented in this simple model. A more robust and intricate model is proposed, in which heart (and vascular) disease causes structural changes, electrical changes, biochemical changes, and others, all of which interact to produce electrical remodeling of ventricular myocardium. This electrical remodeling results in a variety of ECG changes. All of these changes interact, leading to an altered clinical course, and to premature death. It is suggested that research, based on this model, can provide new clues to the processes involved, and improve the prediction of clinical outcomes. New directions in research, in recording equipment, and in organizational activities are suggested to test this new model, and to improve the usefulness of the electrocardiogram as a research and diagnostic tool.