Frontal QRS Research Articles

Increase in R-wave amplitude during transient epicardial injury (prinzmetal type)

An increase in QRS amplitude with S-T elevation occurs during the acute phase of myocardial infarction, coronary ligation and variant angina. Ischemic conduction delay, postulated as the cause, has not been well characterized. Six patients with transient chest pain, S-T elevation and increase in R-wave voltage also displayed concomitant shift of the frontal QRS axis toward the locus of injury. Electrocardiographic considerations suggest that regional ischemic block, not true hemiblock as has been suggested, offers the most inclusive explanation, providing previously neglected clinical confirmation of experimental observations.

Non-invasive localization of the pre-excitation site in patients with the Wolff-Parkinson-White syndrome. Vectorcardiographic and echocardiographic correlations.

Vectorcardiographic and echocardiographic correlations were made in 160 patients with no clinical evidence of cardiovascular diseases except for the Wolff-Parkinson-White syndrome. Frank vectorcardiographic classifications of the patients were based on both the morphology of the delta loop and the direction of the mean delta vector in the horizontal plane as follows; group I (93 patients) with a delta loop inscribed nearly straightly anteriorly and either to the left or right and a mean delta vector directed more anteriorly than +20 degrees, group II (31 patients) with a hook-shaped delta loop inscribed initially anteriorly but soon posteriorly and to the left, and group III (36 patients) with a delta loop inscribed nearly linearly to the left and either posteriorly or slightly anteriorly and a mean delta vector directed more posteriorly than +20 degrees. Abnormal echocardiographic patterns of ventricular contractions in the syndrome were seen at the left ventricular posterior wall (LVPW), the interventricular septum (IVS), and the right ventricular anterior wall (RVAW). In group I abnormal LVPW motions were observed in 91 patients (98%), and both abnormal LVPW and IVS motions in 1. The remaining 1 showed no echocardiographic abnormalities either at LVPW or IVS. In contrast, abnormal IVS motions were observed in 29 patients (94%) of group II. No patient of group II showed abnormal LVPW motions. In 17 patients (47%) of group III abnormal LVPW motions alone were observed. Two patients showed both abnormal LVPW and IVS motions. In the remaining 17 patients (47%), no abnormal motions were noted either at LVPW or IVS. Abnormal RVAW motions were invariably observed in 19 patients of group II with satisfactory RVAW echograms, but never seen in groups I and III. Above findings could be explained by the pre-excitation at LVPW in group I, RVAW in group II, and posterior right ventricle in group III. In 19 patients (8 in group I and 11 in group III) frontal QRS loops were very similar to that in left anterior hemiblock. All of these patients except for 1 showed abnormal LVPW motions, so that the site of pre-excitation was presumably located at the posterior paraseptal region or the posterior IVS. Three cases with a combination of a frontal QRS loop of left anterior hemiblock pattern and abnormal IVS motions in addition to abnormal LVPW motions may be explained by the pre-excitation at the right-sided IVS near LVPW. We feel that combinations of vectorcardiographic and echocardiographic approaches are clinically quite useful as an auxiliary non-invasive means of locating the pre-excitation site.

Epicardial activation in human left anterior fascicular block

Four patients with coronary artery disease and chronic marked left axis deviation, defined as a frontal QRS axis more negative than −45 °, were studied with epicardial mapping during coronary bypass surgery. All patients had normal right ventricular and inferior left ventricular epicardial breakthrough sites and activation sequence. Normal breakthrough in the basal anterolateral left ventricular epicardium was absent in all four patients. Two patients had breakthrough in the apical region of the anterolateral left ventricle. In the other two this region was activated from wave fronts emerging in the right ventricle and inferior left ventricle. The latest site of left ventricular activation was the basal segment of the anterolateral wall, a site never found to be the latest activated in our previously studied patients without conduction defects. This site was activated during or slightly after the terminal portion of the QRS complex. It is concluded that marked left axis deviation in patients with coronary artery disease reflects delayed activation of the basal anterolateral left ventricle, and is consistent with the presence of block or delay in the anterior “fascicle” of the left bundle branch.

Analysis of the Changes in ECG during Status Asthmaticus

An analysis was made of the changes in ECG in 61 random patients during status asthmaticus. It was found that a statistically significant increase occurred in the amplitude of the P wave in the inferior leads. P. pulmonale was noticed in lead II in 26%, in lead III in 18%, and in lead aVF in 25% during status asthmaticus, whereas corresponding values in the controls were 5%, 5% and 3%. A tendency to rS was also seen in the precordial leads, as were a small clockwise rotation, a small rotation of the frontal QRS axis to the right, and slight changes in the ST segment and T wave.

Range of Frontal Plane QRS Axes: Electrocardiograms of Subjects in a Multiphasic Screening Program

The range of mean QRS axes in the frontal plane was determined in electrocardiograms of subjects examined in a program of periodic health screening. Fifty-three of 5,163 individuals had a mean frontal QRS axis between -30 degrees and -60 degrees. Fourteen individuals had an axis between +110 degrees and +133 degrees. These findings suggest that individuals with no history of heart disease may manifest a considerable range of frontal plane QRS axes often to a degree previously considered abnormal. The axes were calculated by the use of leads 1 and 3. Other leads, or the use of the method of Grant, would give different results. Comparison of series of patients can be made only if these variables are understood.

Features of fascicular block imposed upon existing right bundle branch block in the dog and baboon

To delineate in the presence of right bundle branch block the electrocardiographic features of either left anterior fascicular block or left posterior fascicular block, these lesions were produced experimentally in six dog and six baboon hearts using a small knife for right bundle branch block, then a ligature for either left anterior fascicular or left posterior fascicular block. After each resultant conduction defect was proved with epicardial mapping of respective excitation delays, the effects of such blocks on the electrocardiogram and the vectorcardiogram were observed. Corresponding anatomic lesions were confirmed at autopsy. Right bundle branch block alone caused a right-anterior-superior shift of the mean QRS axis that was more pronounced in the dog than in the baboon. Left anterior fascicular block then resulted in extreme left axis deviation in both species. Left posterior fascicular block did not cause further right axis deviation but shifted the mean frontal QRS axis counterclockwise, still superior in the dog but quite inferior in the baboon. QRS duration after right bundle branch block alone was prolonged more in the dog than in the baboon. After fascicular block, further prolongation was greatest in the baboon to quite comparable final values. In both species, the addition of left anterior fascicular block widened the QRS complex more than the addition of left posterior fascicular block. In the electrocardiogram and vectorcardiogram, left anterior fascicular block tended to enhance, and left posterior fascicular block to mask, the aberrancy associated with right bundle branch block alone, especially in the primate.

True and False Left Anterior Hemiblock

For confirming the configuration of the QRS loop in left anterior hemiblock, 82 cases with the frontal QRS vector above minus 30 degrees were collected and classified by the configuration of the horizontal QRS loop. Thereafter, a comparison has been made between the configuration of the QRS loop in clinical cases and that in the authors' construction method, and the following findings for criteria of left anterior hemiblock are obtained. 1) The afferent limb of the frontal QRS loop is dislocated to the left and more superiorly. 2) The efferent and afferent limbs of the horizontal QRS loop are located left posteriorly. The configuration of the horizontal QRS loop is long and narrow and the direction of inscription is clockwise, a figure of 8 or counterclockwise. 3) Cases with the right posterosuperior dislocation of the afferent limb of the QRS loop is excluded from left anterior hemiblock.

Electrocardiographic Criteria for the Diagnosis of Left Anterior Fascicular Block: Left Axis Deviation and Delayed Intraventricular Conduction

The two current criteria for diagnosis of left anterior fascicular block (LAFB) were evaluated; they are marked left axis deviation (LAD) and a delay in the time of inscription of the intrinsicoid deflection (ID) in lead aVL asynchronous to V6. From 400 electrocardiograms with a LAD of --30 degrees or greater, 62 percent showed asynchronous activation of the left ventricle. There was only a general relationship between the degree of LAD and delayed ID in aVL. The incidence of delayed ID in aVL was as follows: 2 percent with mean frontal QRS axis at 0 degrees; 9 percent at --15 degrees; 41 percent at --30 degrees; 69 percent at --45 degrees; 82 percent at --60 degrees; and 100 percent at --75 degrees or greater. The lack of correlation between both criteria in many instances questions their validity. The LAD alone should not be considered synonymous with LAFB. Recognition of delayed inscription of the ID in aVL is a useful supplemental criterion for diagnosis.

Quantitative vectorcardiographic criteria for the differentiation between atrial septal defects of primum and secundum types

From a population of 304 patients who were operated on for atrial septal defects, 25 patients with primum defects and 78 patients with secundum defects were studied with regard to the ability of various quantitative axial lead vectorcardiographic (VCG) data to predict the anatomical type of defect. The patients included all in whom there had been preoperative doubt concerning the classification. By applying the electrocardiographic (ECG) mean frontal QRS axis, 8 patients were erroneously classified, and 14 could not be classified because no definite QRS resultant was present in the frontal plane (diagnostic performance index 0.85). Several VCG criteria showed a better performance, the best being sums of 10 msec Y lead amplitudes from 20 to 50 msec after QRS onset. These criteria, which reflect the superior shift of the middle part of the QRS complex in primum defects, reduced the number of misclassifications to a minimum of 4 (performance 0.96). A combination of this criterion with one based on the duration of the initial inferior QRS vectors gave some further improvement. This simple combination was not surpassed by classification performed by a stepwise discriminant analysis computer program (BMD 07M).

Some correlations between electrocardiographic findings and lung volumes in pulmonary diseases

The mean frontal P vector (ÂP), the sum of the absolute values of the P amplitude in leads I and III (VP), the mean frontal QRS vector (ÂQRS), the sum of the absolute value of the QRS amplitude in leads I and III (VQRS), the transitional zone of the QRS in the precordial leads (TZQRS), the mean frontal axis of the T wave (ÂT), the transitional zone of the T wave in the precordial leads (TZT) and the difference between AQRS and AT were statistically correlated with the vital capacity (VC) and the residual volume (RV) in 170 subjects with chest diseases. This correlation showed that: a) a reduction of VC is associated with a rightward shift of the ÂP, an increase in VP, lowering of VQRS, a leftward displacement of the TZQRS, an abnormal deviation of ÂQRS either to the right or to the left, and an increase in the angle formed between ÂQRS and AT; b) an abnormal increase in RV is associated with a rightward shift of the ÂQRS, while a decrease in RV is associated with a leftward shift of the ÂQRS.

The “Nona” Electrocardiogram: Findings in 100 Patients of the 90+ Age Group

The electrocardiograms of 100 men and women, all past the age of 90, were analyzed for conduction times, axis deviation, summed frontal QRS and T amplitudes. The ECG patterns were classified, and limited clinical correlations were made. The heart rate, R‐T and QRS intervals remained virtually unchanged with age. An increase in PR intervals, a left axis shift and a reduction in summed frontal T values were noted. The high incidences of atrial fibrillation, left anterior hemiblock, extra systoles and delayed AV conduction were probably a result of the widespread use of digitalis. The two most common ECG abnormalities were left ventricular hypertrophy (evidently a natural consequence of advanced age) and myocardial infarction (often undiagnosed clinically).

The electrocardiographic manifestations of spontaneous left pneumothorax.

Abstract The electrocardiograms (ECG) of seven patients with spontaneous left pneumothorax showed these changes resulting from left pneumothorax: a rightward shift of frontal QRS axis, diminution o...

Electrocardiographic and Angiographic Features of Common Atrium

Electrocardiograms and large film biplane angiocardiograms were reviewed in 14 cases of anatomically proved common atrium. All were associated with persistent atrioventricular canal. Electrocardiograms (available in 12 cases) revealed frontal plane QRS loops consistent with persistent atrioventricular canal. Horizontally or superiorly oriented abnormal P vectors were observed in 7 of 12 (58 percent) cases, only one of which was associated with persistent left superior vena cava. None of the cases with a persistent left superior vena cava had a coronary sinus. Abnormal atrioventricular conduction was encountered in two thirds of the cases. In all eight cases in which left ventriculograms were reviewed, typical goose-neck deformity diagnostic of persistent atrioventricular canal was observed. In the five cases in which atrial structure was studied either after the injection of contrast material into the right ventricle or directly into the atrium, a single large globular atrial structure was demonstrated. Although clinical examination and hemodynamic study often cannot distinguish common atrium from the more frequently encountered secundum and primum types of atrial septal defects with large intra-atrial communication, diagnosis of common atrium can be made if the following findings are present: an abnormal frontal plane P axis in conjunction with a frontal QRS loop consistent with persistent atrioventricular canal in the electrocardiograms, and the demonstration of a single atrial structure by large film biplane angiocardiograms after rapid injection of contrast material into the right ventricle, into the main pulmonary artery, or directly into the atrium.

Electrocardiogram in corrected transposition of the great arteries with and without associated cardiac anomalies

Summary 21 cases of bulboventricular inversion type corrected transposition of the great arteries were analyzed electro- and vectorcardiographically with 15 cases uncomplicated by intracardiac anomalies collected from the literature. Frontal QRS axes were divided according to the extent of right-sided ventricular overloading (RVO) as follows: group I, right axis deviation from +90° to +140°, consisted of 12 cases with severe RVO, such as pulmonary stenosis (PS) with ventricular septal defect (VSD) or VSD with severe pulmonary hypertension; group II, left axis deviation from +10° to −75°, consisted of 19 cases with no associated anomalies or with mild to moderate RVO, such as VSD with left-to-right shunt or mild PS. In the precordial leads, reversal of the normal precordial Q wave pattern was observed. Moreover, in cases with no associated anomalies, characteristics QS or rS patterns in III, aVF and right precordial leads were found. These patterns were found in 50% of the cases with no associated anomalies. In most cases, with or without associated anomalies, the direction of the frontal plane initial QRS vectors was to the left and superior. However, in the horizontal plane, the initial vectors were divided into two directions, left anterior and left posterior. Therefore, it is the author's opinion that on interpreting electrocardiograms with the initial QRS vector oriented in the left posterior or anterior direction, it is necessary to consider corrected transposition of the great arteries as a possible cause, in addition to the usual considerations of antero-septal myocardial infarction. WPW syndrome, left bundle branch block and myocardial disease.

Role of intraventricular conduction disturbances in ventricular premature systoles

Ten thousand electrocardiograms were reviewed with reference to intraventricular conduction and ventricular premature systoles. Ventricular premature systoles were found in 444 electrocardiograms, an overall incidence of 4.44 percent. The incidence was small in the presence of normal intraventricular conduction (3.73 percent) and greater in the groups with abnormal intraventricular conduction (9.80 percent), increasing in parallel with the degree of conduction delay. The coupling interval was significantly longer in tracings revealing intraventricular conduction disturbances than in normal tracings. Studies of QRS configuration and mean frontal QRS axis of the dominant and ectopic beats disclosed: (1) a positive correlation between the QRS duration of sinus and premature beats; (2) a significantly greater angle between the QRS axes of sinus and ectopic beats in the presence of abnormal intraventricular conduction; and (3) in groups with intraventricular conduction delay, a QRS axis of premature systoles commonly either directed away from the region of the blocked bundle or suggesting an additional delay in the remaining nonblocked fascicles. From these data we conclude that (1) ventricular premature systoles are more likely to originate from the area of intraventricular conduction delay, and (2) the ectopic impulse seems to invade and at least partially utilize the other fascicles of the Purkinje system for ventricular excitation. The clinical significance of more frequent ventricular premature systoles in patients with cardiac disorders than in normal subjects should be reemphasized.

Gross anatomy associated with patterns called left posterior hemiblock.

From a compilation of 1411 gross dissections of the hearts from patients who had had recent electrocardiograms prior to death, 62 were found to have frontal QRS axes between +90 and +180°. Thirty-eight exhibited an S 1 Q 3 R 3 pattern-the second screening criterion basic to consideration for the label of left posterior hemiblock (LPH). Twenty-two of these also had right ventricular free wall weights in excess of 70 g. Two others exhibited inferior myocardial infarction only. Of the remaining 14, six afforded mild clinical suspicion of increased hemodynamic loading of the right heart but did not have increased right ventricular weights. Four had right bundle-branch block (RBBB), and only one had a prolonged P-R interval. The S 1 Q 3 R 3 pattern with right-axis deviation thus occurred in patients with or without right ventricular hypertrophy and with or without inferior wall myocardial infarction. Right bundle-branch block was a frequent occurrence in the spectrum of right-axis deviation (RAD) whether S 1 Q 3 R 3 was present or not. The scatter of the frequent associates of RAD-inferior myocardial lesions, right ventricular hypertrophy, a clinical history of right ventricular loading diseases, and RBBB—suggests three alternative ways of viewing the S 1 Q 3 R 3 pattern with RAD: (1) LPH is a cause of S 1 Q 3 R 3 with RAD. It is a manifestation of left ventricular myocardial disease, but it may be a result of overt infarction, or may be mimicked by right ventricular disease. (2) LPH is the cause of S 1 Q 3 R 3 with RAD. It is the means by which diverse etiologies produce a distinctive electrocardiographic pattern (including left ventricular myocardial deficits, right ventricular enlargement, or a small group of unknown causes). (3) LPH is an artifact of convenience. Patients with RAD may or may not have S 1 Q 3 R 3 ; they frequently have inferior wall myocardial infarction, right ventricular overload or enlargement, and RBBB.

Right bundle branch block and left posterior fascicular block: Vectorcardiographic and clinical features

The clinical and vectorcardiographic features were studied in 12 patients, aged 64 to 85 years (mean 74 years), with right bundle branch block and left posterior fascicular block. The blocks had been present for 1 to 9 years (mean 2.7 years). Five patients had coronary artery disease of whom 4 had vectorcardiographic criteria of inferior wall infarction. In 5 patients the cause was undetermined (probably Lenegre's disease), and 2 patients had aortic valve sclerosis. Other causes simulating this type of bilateral bundle branch block were excluded. In 7 patients the horizontal QRS loop was predominantly anterior with variable direction of inscription, and was termed type I. In 5 patients the loop was normal in position, predominantly counterclockwise and was termed type II. The frontal QRS loop was clockwise with the maximal or half area vector inferior (mean 102.1 °). Two patients died of causes not related to disturbed atrioventricular conduction; complete heart block developed in none.

Comparison of the 12-lead and orthogonal electrocardiograms, with special reference to the frontal QRS axis

Summary By reviewing 1,000 electrocardiograms, configuration of QRS, ST and T, as well as QRS amplitude was compared between leads I, V6 and X, and between aVF and Y. Frontal QRS axis derived from leads I and aVF (conventional) was compared to that from X and Y (orthogonal). Morphologically, QRS in lead X resembled either one or both of leads I and V6 in 87.6%, while QRS in Y resembled that in aVF in 82.3% of cases. The net QRS amplitude and ST-T polarity showed good agreement between V6 and X, as well as between aVF and, Y, while their agreement was poorer between I and X. The frontal QRS axis in 12 leads showedthe following distribution normal (+90 to −30°), 87.1%; left axis: deviation (−30 to −180°), 7.7%; and right axis deviation (+90 to +180°), 5.2%. In orthogonal leads, the following criteria yielded similar incidence of these axis deviations: normal, between +60 and −15°; left axis, −15 to −180°; and right axis, +60 to +180°. The QRS axis from orthogonal leads showed lesser variation than that from 12 leads within the normal range, while it tended to show wider variations toward extreme left or right. When both lead systems showed abnormal axis deviation, possible clinical cause for such axis was found in 81–85% of cases, while when only one of the two systems showed abnormal axis, possible cause was found in only 50–60%. Hence, regarding abnormal axes, the conventional and orthogonal systems appear to supplement each other for a better sensitivity and specificity.

Experimental bigeminal arrhythmia in the dog

Ventricular bigeminal rhythm was successfully induced in 26 of 34 vagotomized dogs. Induction was accomplished through bilateral carotid artery occlusion, constriction of the thoracic aorta, or a combination of both. The following observations were made:o1.This arrhythmia appears to depend on some combination of high systemic arterial pressure and increased heart rate. It can be induced under conditions in which sympathetic discharge to the heart is inhibited.2.Sinoatrial firing rate during the bigeminal rhythm is usually regular. The PR interval is always shorter and QRS duration longer in the abnormal complex of a bigeminal pair.3.Delta waves are commonly present in the initial portion of QRS complexes of abnormal beats. These complexes have the general characteristics associated with ventricular pre-excitation (WPW).4.Mean frontal QRS vector angles in normal beats of bigeminal pairs were in the range of 23°–76°. Vector angles for abnormal mean frontal QRS complexes were widely distributed in a range of 137°–357°.5.The experimental data do not provide a positive basis for classifying the abnormal complexes as ventricular pre-excitation or coupled late ventricular ectopic beats. In either case, it appears that the site of initial ventricular activation in abnormal complexes is widely dispersed in this group of animals. This arrhythmia appears to depend on some combination of high systemic arterial pressure and increased heart rate. It can be induced under conditions in which sympathetic discharge to the heart is inhibited. Sinoatrial firing rate during the bigeminal rhythm is usually regular. The PR interval is always shorter and QRS duration longer in the abnormal complex of a bigeminal pair. Delta waves are commonly present in the initial portion of QRS complexes of abnormal beats. These complexes have the general characteristics associated with ventricular pre-excitation (WPW). Mean frontal QRS vector angles in normal beats of bigeminal pairs were in the range of 23°–76°. Vector angles for abnormal mean frontal QRS complexes were widely distributed in a range of 137°–357°. The experimental data do not provide a positive basis for classifying the abnormal complexes as ventricular pre-excitation or coupled late ventricular ectopic beats. In either case, it appears that the site of initial ventricular activation in abnormal complexes is widely dispersed in this group of animals.

The Electrocardiogram in Chronic Airways Obstruction: The Role of Bronchitis and Emphysema

Will the electrocardiogram differentiate between types of chronic airway obstruction? This study was done to determine if there was any significant difference in the electrocardiogram of those patients with chronic airway obstruction who had relatively pure bronchitis or emphysema at postmortem examination. Utilizing the present standard electrocardiographic criteria for right ventricular hypertrophy plus new criteria we developed in a previous report, electrocardiograms of eight patients who had relatively pure bronchitis and 17 who had relatively pure chronic emphysema were reviewed for differentiating criteria. The most significant difference between electrocardiograms in the two groups was the presence of “P-pulmonale” in 13 of 17 emphysema patients. It was not found in any of the bronchitis patients. Two other suggestive differences were a greater degree of counterclockwise posterior rotation of the horizontal QRS vector and a greater clockwise rightward rotation (beyond 90°) of the frontal QRS vector in the emphysema group. Will the electrocardiogram differentiate between types of chronic airway obstruction? This study was done to determine if there was any significant difference in the electrocardiogram of those patients with chronic airway obstruction who had relatively pure bronchitis or emphysema at postmortem examination. Utilizing the present standard electrocardiographic criteria for right ventricular hypertrophy plus new criteria we developed in a previous report, electrocardiograms of eight patients who had relatively pure bronchitis and 17 who had relatively pure chronic emphysema were reviewed for differentiating criteria. The most significant difference between electrocardiograms in the two groups was the presence of “P-pulmonale” in 13 of 17 emphysema patients. It was not found in any of the bronchitis patients. Two other suggestive differences were a greater degree of counterclockwise posterior rotation of the horizontal QRS vector and a greater clockwise rightward rotation (beyond 90°) of the frontal QRS vector in the emphysema group.