Computer analysis of frank vectorcardiograms in normal children--maximal spatial QRS vector

Frank vectorcardiograms recorded on magnetic tape were analyzed by a computer. The study population was 835 normal children aged from 6 to 16. Magnitudes, angles (azimuth, elevation) of the maximal spatial QRS vector and QRS duration were calculated. The magnitude of maximal spatial QRS vector increased significantly in males compared to those in females at ages 9-10, 11-12 (p less than 0.01) and 15-16 (p less than 0.001). Though there was no significant difference of elevation in either sex, azimuth tended to move more anteriorly in females than in males. QRS duration in males became longer with increasing age, while in females at age 15-16, it decreased (p less than 0.001).     

Spatial Frank vectorcardiogram in left posterior fascicular block. Criteria and correlation with clinical and electrocardiographic data.

Computer processing of spatial QRS parameters (Frank vectorcardiogram) was used to study left posterior fascicular block. The best set of vectorcardiographic criteria was sought in order to characterise the classic pattern of left posterior fascicular block. Using these criteria, 18 cases were selected from a group of 4600 patients and 340 healthy subjects; isolated left posterior fascicular block was seen in 10 cases, and was associated with right bundle-branch block in 8 cases. It is shown that some external factors can influence the aspect of the spatial QRS loop in left posterior fascicular block: cardiomegaly tends to produce a superior displacement of the main QRS forces: right bundle-branch block enhances the superior displacement of the initial forces and shifts the main QRS forces more anteriorly and to the right. The 'masquerading effect' of the left posterior fascicular block on a concomitant inferior myocardial infarct was also shown. The most important diagnostic feature was the opposite direction of the initial forces (left anterosuperior) and the maximal vector (right postero-inferior): the angle between these two vectors averaged 152 degrees. Other criteria, such as the direction of rotation or the axis of the frontal loop, the vertical direction of the spatial loop, the presence of a Q wave in leads II, III, and aVF of the electrocardiogram, are not mandatory for the diagnosis of left posterior fascicular block.     

2387例19岁以下城市人群QRS波群与T波平均心电轴分析

为探讨青少年儿童心电图额面、横面QRS波群和T波平均心电轴与性别、年龄的关系,分析2387例19岁以下健康人群的心电图。结果显示:(1)额面QRS波群平均心电轴,男性与年龄增长无关,女性则随年龄增长而逐渐变小(电轴左移)。(2)额面T波平均心电轴,16岁以下的男性及10岁以下的女性随年龄增长而逐渐变大(电轴右移)。(3)横面QRS波群平均心电轴,男性及13岁以下的女性随年龄增长而变小(电轴后移)。(4)横面T波平均心电轴,男性及16岁以下的女性随年龄增长而逐渐增大(电轴前移)。(5)T_Ⅱ>T_Ⅰ和Tv_1>Tv_5(Tv_6)二种综合征在男性青少年中出现率较高,且符合T波平均心电轴的演变规律,认为此现象可能是青少年心电图的正常变异。     

The vectorcardiogram pattern of the athlete's heart (author's transl)

In order to assess the vectorcardiographic pattern of the athlete's heart, we evaluated the vectorcardiograms of 17 professional footballers; the signs of ventricular hypertrophy were particularly studied. 9 athletes had left ventricular hypertrophy, 3 showed VCgraphic signs of combined ventricular hypertrophy and 5 had normal vectorcardiograms. In all athletes with left ventricular hypertrophy the initial forces had normal spatial orientation (I A left ventricular hypertrophy). Likely, the combined right ventricular hypertrophy explains these VCgraphic patterns. The QRS loop did not show abnormal morphology, only the high magnitude of the spatial maximum QRS vectors was significant for diagnosis of left ventricular hypertrophy. The increase of the cardiac volumes induced by training might explain the high magnitude of the QRS loop.     

Hemodynamic correlates of vectorcardiographic QRS loops in pure mitral stenosis

The hemodynamic correlates of the vectorcardiographic types of right ventricular hypertrophy (RVH) according to Chou and Helm and those with normal QRS loop in the horizontal plane of Frank system were analyzed in 100 patients with pure mitral stenosis. All underwent right and left heart catheterization. Additionally, coronary arteriography was done on 16 whose ages were above 40. Type A RVH was associated with the most severe hemodynamic alterations with markedly elevated total pulmonary vascular resistance (TPVR), mean pulmonary artery pressure (MPAP), peak right ventricular pressure (RRVP) and the smallest mitral valve area (MVA). The severity of these parameters were to a lesser degree obtainable in type C but with no significant difference from type A (p greater than 0.05). However, types A and C were clearly separated from type B and normal QRS loop (p less than 0.05). Type B RVH and normal QRS loop showed milder hemodynamic changes and were not significantly different (p greater than 0.05). Our results indicate that in pure mitral stenosis the development of RVH is from a normal loop into type B, C and A reflecting an increasing severity of hemodynamic changes which affect the right ventricle. This order of development is different from the traditional view.     

Changes in organ weights and blood parameters in ageing Brattleboro rats with hereditary diabetes insipidus

Organ weights and blood parameters were measured in male and female Brattleboro rats with hereditary diabetes insipidus (DI) and in normal rats of the same strain, between 37 and 138 weeks old. Although differences in body weight between the homozygous DI and heterozygous normal rats accounted for differences in the weights of the heart and gonads, the weights of the spleen, liver and kidney were not solely body-weight dependent; there were significant sex and genotype differences in the mean weights of these organs. The liver, heart and gonads were the only organs showing age-dependent changes. No genotype-dependent differences were observed in the haematocrit and haemoglobin concentration, although there was a sex difference; the mean values of these parameters were higher in males. Plasma glucose concentrations were significantly lower in homozygous than in heterozygous rats; in the latter, plasma glucose concentration decreased with age. No significant changes occurred in the mean plasma concentrations of sodium or potassium with age or genotype. Total plasma lipids of heterozygous female rats showed both age- and genotype-dependent changes; this parameter reached a plateau at 90-100 weeks old, and was significantly higher in heterozygous females than in all other groups. Plasma proteins showed no age-dependent changes, but were of higher mean value in heterozygous than in homozygous rats and were greater in females than in males. Differences in blood parameters of homozygous and heterozygous Brattleboro rats are discussed in terms of differences in hormone concentrations.     

Normal limits of pediatric Frank lead electrocardiograms. Differences in data obtained in 4th or 5th intercostal spaces

Frank lead electrocardiograms (VCGs) were recorded from 970 young subjects in order to establish normal limits for pediatric VCGs. In 245 children and 231 adolescents, the thoracic electrodes were located at the levels of the 4th and of the 5th intercostal space with subjects in supine position. Pairwise comparisons of 211 linear and angular parameters were made, using the 4th interspace as the reference. In children, there were 155 parameters with statistically significant differences and 56 parameters without significant differences between levels 4 and 5. In adolescents, corresponding figures were 158 parameters with significant differences and 53 without. Results for selected measurements showed an increase of the amplitude of Q and R waves in leads X and Y, a decrease of Q and R waves in lead Z and an increase of maximal spatial and planar QRS vectors, with the QRS loop being more anteriorly oriented by shifting the electrodes from level 4 to level 5. The mean differences in amplitude and orientation were generally small and of little practical value. However, the percentile distribution of the differences indicated that substantial changes in either direction can occur in some subjects. Thus, quantitative analysis of the pediatric Frank VCGs can be critically affected by modification of electrode placement. It is suggested that normal limits should be determined for each recording level and that criteria for analysis should be applied only to VCGs recorded at the same specified level.     

Extent of the inferior myocardial infarction assessed by the frontal plane of the vectorcardiogram.

A correlation was made between the vectorcardiographic changes and the peak value of the L.D.H. in the serum of 21 patients with acute inferior (diafragmatic) M.I. The following vectorcardiographic variables showed changes proportional to the increase in serum L.D.H. The correlation was found to be statistically significant. The direction of the 0.025 sec vector (r = 0.63, P less than 0.005). The duration of the initial superior forces of the QRS loop (r = 0.87, P less than 0.001). The maximal leftward deviation of the initial superior QRS loop forces (r = 0.65, P less than 0.005). The maximal superior deviation of the initial QRS loop forces (r = 0.68, P less than 0.05). The ratio of the maximal superior deviation over the maximal inferior deviation of the QRS loop "QY/RY" (r = 0.76, P less than 0.001). The area under the initial superior forces of the QRS loop and over 0 degrees +/- 180 degrees axis in squared milimeters (r = 0.88, P less than 0.001). It is suggested that V.C.G. is a usefull means in assessing the extent of inferior M.I.     

Experimental Induction of Immediate-Type Sensitization

Electrocardiographic and vectorcardiographic changes in the heart were evaluated in 14 children with bronchial asthma during the acute attack and later during remission. Many more abnormalities were noted on the vectorcardiograms as compared to electrocardiograms. The abnormalities noted were in closer relationship to the particular attack rather than to the severity of asthma as revealed by history.

Three patients showed evidence of right atrial enlargement during the acute attack, and all of them returned to normal during remission.

Ten patients had abnormal orientation of QRS loop on vectorcardiogram during the acute attack, and of these, seven patients continued to have the abnormality during remission. Of the ten patients, five had evidence suggestive of left ventricular enlargement during the acute attack, and all returned to normal during remission. This finding was very intriguing and the possible explanations are discussed.     

Electrophysiological Changes in the Heart of Children with Bronchial Asthma during the Acute Attack and Later during Remission

Electrocardiographic and vectorcardiographic changes in the heart were evaluated in 14 children with bronchial asthma during the acute attack and later during remission. Many more abnormalities were noted on the vectorcardiograms as compared to electrocardiograms. The abnormalities noted were in closer relationship to the particular attack rather than to the severity of asthma as revealed by history.

Three patients showed evidence of right atrial enlargement during the acute attack, and all of them returned to normal during remission.

Ten patients had abnormal orientation of QRS loop on vectorcardiogram during the acute attack, and of these, seven patients continued to have the abnormality during remission. Of the ten patients, five had evidence suggestive of left ventricular enlargement during the acute attack, and all returned to normal during remission. This finding was very intriguing and the possible explanations are discussed.     

Correlation of the vectorcardiographic, echocardiographic parameters and hemodynamics in valvular aortic stenosis

The objective of this work was to verify the correlation between haemodynamic (KT), echocardiographic (ECHO) and vectorcardiographic (VCG) parameters in valvular aortic stenosis (VAS). The VCG was analyzed by the Louvain programme and compared with reference ECHO and KT parameters--transvalvular peak-gradient (PG), mean gradient (MG) and valvular area (AREA)--in 54 consecutive patients with isolated VAS. Of the 84 correlations studied, only three proved to be significant for linear parameters and six for angular parameters. The best correlation was observed between the azimuthal angle of the spatial area vector of the QRS loop and MG-KT (r2 = 0.36, p less than 0.01). On the other hand, there was no significant correlation between the reference parameters and the amplitude of the QRS spatial maximum vector. The conclusion was drawn that there was no linear correlation between the VCG indicators of LVH and ECHO and KT indices of severity in an unselected VAS population. Each method carries its own limitations and each must be used as a complement to other methods.     

Evolution of spatial cognition: sex-specific patterns of spatial behavior predict hippocampal size.

In a study of two congeneric rodent species, sex differences in hippocampal size were predicted by sex-specific patterns of spatial cognition. Hippocampal size is known to correlate positively with maze performance in laboratory mouse strains and with selective pressure for spatial memory among passerine bird species. In polygamous vole species (Rodentia: Microtus), males range more widely than females in the field and perform better on laboratory measures of spatial ability; both of these differences are absent in monogamous vole species. Ten females and males were taken from natural populations of two vole species, the polygamous meadow vole, M. pennsylvanicus, and the monogamous pine vole, M. pinetorum. Only in the polygamous species do males have larger hippocampi relative to the entire brain than do females. Two-way analysis of variance shows that the ratio of hippocampal volume to brain volume is differently related to sex in these two species. To our knowledge, no previous studies of hippocampal size have linked both evolutionary and psychometric data to hippocampal dimensions. Our controlled comparison suggests that evolution can produce adaptive sex differences in behavior and its neural substrate.     

Combined ventricular enlargement during the first months of life A vectorcardiographic study of the T loop

The T loops of 10 infants with congenital heart lesions producing combined ventricular enlargement were compared with those of normal controls and of infants with isolated right and isolated left ventricular enlargement. It was found that in biventricular enlargement the T loop might be normally placed (for age), or on the contrary it might reflect either the enlargement of the right or the enlargement of the left ventricle.

A heretofore undescribed vectorcardiographic pattern of biventricular enlargement during the first year of life was shown. This consisted of the association of QRS changes characteristic of pure right ventricular enlargement coexisting with a T loop pointing anteriorly and to the right. The latter orientation was attributed to left ventricular strain.     

Vectorcardiographic and hemodynamic correlation in chronic obstructive pulmonary disease

Vectorcardiograms in 34 patients with chronic obstructive pulmonary disease and 30 normal people were analyzed with the aim of developing sensitive criteria for the detection of pulmonary artery hypertension. The pulmonary artery pressure was correlated with the known vectorcardiographic measurements of the area of the QRS loop and with two new linear measurements which reflect the QRS loop displacement of the right ventricular hypertrophy. The proposed linear vector-cardiographic and the QRS loop area criteria provided a sensitive means for the noninvasive approximate estimation of mean pulmonary artery pressure in patients with chronic obstructive pulmonary disease. Their sensitivity and specificity were proved to be considerable.     

Sex differences in the evolution of the electrocardiographic QT interval with age.

OBJECTIVE: To investigate sex differences in the evolution of the QT interval with age. SUBJECTS AND METHODS: A community-based representative North American population sample of 14,379 children and adults aged from birth to 75 years. The measured QT intervals (QTm) were determined by a computer algorithm and QTm, corrected for heart rate (HR), was expressed as QT index: QTI = (QTm/Tp) x 100, where QTp is the predicted QT from the formula QTp (ms) = 656/(1 + HR/100). MAIN RESULTS: The QTI values of females were significantly longer than of males in all age groups from 15 to 50 years tested at yearly intervals. This difference was due to a 20 ms drop in rate-corrected QT values in adolescent males after puberty, whereas QT values of females remained unchanged throughout the growth, maturation and reproductive years. The new QT prediction formula explained 83% of total QT variance in females and 82% in males after adjustment for heart rate and for the observed significant influence of ventricular excitation time (QRS duration) on QT interval in both sexes and a correction for QT age trend in males. CONCLUSIONS: The sex difference in the QT interval is due to QT shortening in males after puberty rather than QT prolongation in women during reproductive years. The fact that QRS duration is a significant determinant of the QT interval has important theoretical implications for attempts to model the ventricular repolarization process and it indicates that the traditional concept of reverse sequence of ventricular repolarization is not universally valid in all myocardial regions.     

Evolution of QRS-T relationship from birth to adolescence in Frank-lead orthogonal electrocardiograms of 1492 normal children.

Patterns of evolution of QRS-T relationship were investigated by determining statistical distributions of QRS and STT integral vectors and the ventricular gradient vector in 1492 normal children divided into 12 age groups from birth to the age of 16 years. From birth to the age of 4 days, the ventricular gradient vector shifts posteriorly and to the left due to posterior shift of the STT integral vector and an increase in the spatial angle between QRS and STT integral vectors to a mean value of 103 degrees. These early neonatal changes in QRS-T relationship probably reflect the sudden reduction of hemodynamic load and the subsequent postnatal atrophy of the right ventricle while the left ventricular load slowly increases. The magnitude of the ventricular gradient vector increases from age 3 weeks until about 7 years. The increase appears to be related to a gradual increase in the magnitude of the QRS and STT integral vectors and a drastic decrease in the spatial angle between them. The spatial angle between QRS and STT integral vectors reaches it minimum (22 degrees) in the age group 1.5--4.5 years, suggesting that at that age the average direction of ventricular excitation and repolarization wavefronts are nearly opposite to each other. In addition to the shifting balance between the left and right ventricular hemodynamic load, other factors, such as the maturation of the sympathetic nervous system, may be important in determining spatial gradients in the duration of action potentials, thus influencing the relationship between ventricular excitation and repolarization.     

The anteriorly oriented horizontal vector loop: The problem of distinction between direct posterior myocardial infarction and normal variation

An attempt was made to distinguish the vectorcardiogram of a direct posterior myocardial infarction from an anterior horizontal loop that is known to occur in over 20 per cent of normal subjects. Patients with anterior horizontal QRS loops and arteriographic evidence of complete occlusion of the right coronary artery, the posterior descending artery, or dominant left circumflex coronary artery were compared to normal individuals with anterior vector loops in the horizontal plane. Nine patients were thought to have a direct posterior infarction; 13 patients were thought to be normal. The association of an abnormal frontal plane QRS loop indicative of a diaphragmatic infarction (5 of 9 patients) implied an associated direct posterior infarction. Otherwise, no differences were observed in the two groups. Specifically, in the horizontal plane, the 20, 30, 40, 50, and 60 msec. vectors, both magnitude and direction, were similar. Also the maximum QRS vector, half-area vector, anterior accession time, QRS loop rotation, T-loop angle, and rotation and magnitude of the maximum anterior, maximum posterior, and maximum right-ward vectors of the QRS loop were similar in both groups. It appears, therefore, that the previously established criteria for the vectorcardiographic diagnosis of a direct posterior myocardial infarction, in general, adequately describes the vectorcardiogram of a direct posterior infarction; but fails to distinguish it from the anteriorly oriented vectorcardiogram of normal individuals which occurs frequently enough to make the importance of this distinction a practical clinical problem.