Showing papers on "QRS complex published in 1974"
TL;DR: Although slow systemic increase of K + induces asystole in animals, administration to a region of myocardium produces ventricular ectopic beats and fibrillation, the latter effect may be due to re-entry and may be mechanistically similar to the arrhythmias of early ischemia.
182 citations
TL;DR: The specific echocardiographic abnormality demonstrated in left bundle branch block is a very dynamic posterior motion of the interventricular septum occurring within 0.04 seconds of the onset of the QRS and preceding the anterior motion ofthe posterior left ventricular wall during ventricular ejection.
Abstract: Seventeen patients with left bundle branch block were studied using standard echocardiographic techniques employing a strip chart recorder. All 17 patients were found to have specific echocardiographic findings of abnormal septal motion uniquely different from previously described forms found in volume overload states of the right ventricle as well as coronary artery disease. The specific echocardiographic abnormality demonstrated in left bundle branch block is a very dynamic posterior motion of the interventricular septum occurring within 0.04 seconds of the onset of the QRS and preceding the anterior motion of the posterior left ventricular wall during ventricular ejection. This type of septal motion is not seen in the other forms of abnormal septal motion and appears to be specific for left bundle branch block.
139 citations
TL;DR: The proposed criteria for the diagnosis of inferior myocardial infarction were found to be statistically superior to both ECG Q wave criteria and to the VCG initial force criteria of Young and Williams.
Abstract: Frank lead vectorcardiograms (VCG) from four carefully selected patient subgroups (226 patients) were analyzed to develop optimal criteria for the diagnosis of anterior myocardial infarction. Specificity was evaluated using 100 healthy volunteers under age 30 and 80 patients with normal left ventriculogram and normal coronary arteriograms. Sensitivity was determined using 25 patients with evolutionary ST-T wave changes (V1-2), and LDH and CPK isoenzyme evidence of acute myocardial infarction; and 21 patients with anterior wall akinesia or dyskinesia and greater than 70% occlusion of the left anterior descending coronary artery. Patients with VCG evidence of bundle branch block, left or right ventricular hypertrophy were excluded. The criterion for the diagnosis of anterior myocardial infarction which was found to give the highest sensitivity with greater than or equal to 95% specificity was: initial anterior QRS forces must not exceed 0.1 mV in maximal anterior amplitude and also must not exceed 24 msec in duration. The performance of this proposed criterion was then tested using four similarly defined patient subgroups consisting of a total of 222 patients. The incidence of false positive diagnosis in these test subgroups was less than 1% with a sensitivity of greater than 95%. The overall performance of the proposed criterion was found to be significantly superior to both the widely accepted VCG and ECG criteria for anterior myocardial infarction. Thus, this quantitative criterion using both time and duration of initial anterior forces is both a highly specific and a sensitive indicator of anterior myocardial infarction.
86 citations
TL;DR: To investigate the effects of physical training on cardiac dimensions and function, eight dogs were exercised for 12 weeks by treadmill running 1 hour/ day, 5 days/week and five dogs were confined in cages as controls for an 8-week period.
Abstract: To investigate the effects of physical training on cardiac dimensions and function, eight dogs were exercised for 12 weeks by treadmill running 1 hour/day, 5 days/week. Five dogs were confined in cages as controls for an 8-week period. Heart rates were monitored by telemetry during rest and exercise. Maximum QRS spatial magnitudes were calculated from records of McFee lead electrocardiograms. Left ventricular end-diastolic dimensions were determined radiographically by the bead and clip technique. Training produced statistically significant decreases in heart rate at rest and at a standard work load of 6.1 mph on a level treadmill and statistically significant increases in work load at a standard heart rate of 194 beats/min. Improvements were rapid during the first 4 weeks of training but gradual during the remaining 8 weeks. Training caused small but statistically significant increases in left ventricular end-diastolic wall thickness, estimated left ventricular mass, and maximum QRS spatial magnitude.
81 citations
TL;DR: Observed observations indicate that an anterior infarction in patients referred because of angina pectoris is accompanied by significant impairment of left ventricular function, whereas an inferior infarctions (isolated), although accompanied by asynergy, is usually associated with normal hemodynamics.
Abstract: Clinical, hemodynamic and angiographic findings were reviewed in 82 patients with isolated inferior, 55 patients with isolated anterior and 27 with combined inferior and anterior myocardial infarction and were compared with findings in 100 patients without electrocardiographic evidence of a prior transmural myocardial infarction. All of the 264 patients were referred and evaluated because of angina pectoris and found, on selective coronary angiography, to have coronary artery disease. There was no significant difference in the ages of the patients in each group studied. A history of heart failure, audible gallops and cardiomegaly were more prevalent in the two groups with anterior infarction (isolated and combined with inferior infarction) than in the other two groups. The mean left ventricular hemodynamic measurements (end-diastolic pressure, end-diastolic volume and ejection fraction) in the groups of patients with a normal QRS or an isolated inferior myocardial infarction were not significantly different from those of patients with a normal left ventricle. Patients with isolated anterior myocardia infarction had abnormal end-diastolic pressure (68 percent), end-diastolic volume (51 percent) and ejection fraction (67 percent). Similarly, the group with multiple infarctions had abnormal hemodynamic measurements, with 81 percent having an abnormal ejection fraction. For the entire group of patients studied, an abnormal end-diastolic volume was always associated with an abnormal ejection fraction. Cardiomegaly on X-ray film was associated with an abnormal end-diastolic volume and ejection fraction. An abnormal contractile pattern (asynergy) was noted in 42 percent of the patients with a normal QRS; inferior asynergy was observed in 88 percent with inferior infarction, and anterior or apical asynergy, or both, was found in 90 percent with anterior infarction. All the patients with multiple infarctions had asynergy. The right coronary artery was significantly involved in 90 percent of the patients with inferior infarction, while all the patients with anterio infarction had significant disease of the left anterior descending artery. More than 80 percent of the patients with an infarction pattern on electrocardiogram had double or triple vessel disease, as compared with 68 percent of the patients with a normal QRS pattern. This study represents a select group of patients referred because of angina pectoris and cannot be extended to the asymptomatic patient with coronary artery disease. The observations made on these patients indicate that an anterior infarction (isolated or combined with inferior) in patients referred because of angina pectoris is accompanied by significant impairment of left ventricular function, whereas an inferior infarction (isolated), although accompanied by asynergy, is usually associated with normal hemodynamics. The electrocardiogram is not sensitive enough to predict reliably in the individual patient the extent and severity of the coronary artery disease.
77 citations
TL;DR: Evidence is presented indicating that the bundle branch block during tachycardia was likely to be due to concealed retrograde conduction of the appropriate bundle branch, and in the presence of an anomalous bypass, the cycle length of the tachycardsia depended on the anatomical relationship of the anomalies bypass to the blocked bundle branch.
Abstract: Four patients with paroxysmal supraventricular tachycardia have been studied using programmed electrical stimulation of the heart and intracardiac recordings. One patient had an atrioventricular (A-V) junctional tachycardia, possibly due to a rapidly discharging protected ectopic focus, and three patients had anomalous atrioventricular connections. The ECG recordings in all four patients showed a bundle branch block pattern during tachycardia, and normal intraventricular conduction could be produced by suitably timed right ventricular premature beats. The cycle length of the tachycardia was shorter with normal intraventricular conduction than in the presence of a bundle branch block pattern in two patients. Evidence is presented indicating that the bundle branch block during tachycardia was likely to be due to concealed retrograde conduction of the appropriate bundle branch, and in the presence of an anomalous bypass, the cycle length of the tachycardia depended on the anatomical relationship of the anoma...
74 citations
TL;DR: Since no relation was found between the length of the incision and the QRS duration, the results suggest that the ventriculotomy-induced RBBB pattern is unlikely to be due to disruption of a continuous Purkinje network but is probably due to disruptions of a distal branch or branches of the right bundle.
Abstract: Fifteen patients with various congenital heart defects were studied during open heart surgery in order to establish the precise mechanism by which a right ventriculotomy causes a right bundle branch block (RBBB) pattern on the scalar electrocardiogram (ECG). All required a right ventriculotomy for the correction of their defects. In each, the right ventriculotomy was carried out in steps, with incisions (3 to 7) of approximately 1 cm in length. Six simultaneous scalar ECG leads were recorded prior to the first incision and following each incision. The QRS duration was then measured and related to the length of the ventriculotomy. Following the right ventriculotomy, 12 of the 15 patients developed an RBBB pattern; the remaining three did not. In all cases, the total increase in QRS duration occurred during one specific incision of the right ventricular free wall and was not related to the total length of the ventriculotomy or to the sequence of the incisions. The site at which incision of the right ventric...
63 citations
TL;DR: An increase in magnitude of the QRS potentials in an electrocardiographic lead may be caused by a greater size or number of individual fiber dipoles, as in ventricular hypertrophy, or by decreased cancellation of an opposing vector component, asIn myocardial infarction.
Abstract: THE relation between the electrocardiogram as it registers from body-surface leads and the actual electromotive force of the heart is influenced by many factors. An increase in magnitude of the QRS...
51 citations
TL;DR: The hypothesis that first degree heart block in the presence of a QRS pattern of bifascicular block is related to conduction delay in the remaining fasclcle is tested and his bundle electrography is essential to determine accurately whether the P-R interval is normal or prolonged.
Abstract: To test the hypothesis that first degree heart block in the presence of a QRS pattern of bifascicular block is related to conduction delay in the remaining fasclcle, we reviewed the His bundle records of 63 patients with a pattern of bifascicular block and compared the H-V intervals of the 41 patients without first degree heart block with those of the 22 patients with P-R prolongation. The following conclusions were drawn from analysis of our cases and those studied and reported by others: (1) In the presence of first degree heart block a significant number of these patients will have a normal H-V interval. (2) More than 50 percent of patients with a pattern of left or right bundle branch block and right axis deviation have a prolonged H-V interval regardless of the P-R interval, and the correlation of P-R and H-V prolongation is not statistically significant (P > 0.05 and < 0.1). (3) In patients with a pattern of right bundle branch block and left axis deviation, the presence of P-R prolongation suggests abnormality of the H-V interval (P < 0.005), although 30 percent of the patients with this finding will have a normal H-V interval and the H-V interval cannot be predicted in individual patients. (4) His bundle electrography is essential to determine accurately the presence of trifascicular block in individual patients whether the P-R interval is normal or prolonged.
46 citations
TL;DR: Comparing one year follow-up results of those with versus those without perioperative VCG changes of infarction showed that late death, clinical evidence of myocardial damage, and reinfarction were more frequent in the infarctions group, however, no difference in N.Y.A.H. could be demonstrated.
42 citations
TL;DR: The incomplete nature of some electrocardiographic “complete” bundle branch and fasclcular blocks is demonstrated using the atrial extrastimulus technique, and a discordance of conduction time and refractory period is related to the development of trifascicular block in patients with bifASCicular block and a normal H-V interval.
Abstract: The incomplete nature of some electrocardiographic “complete” bundle branch and fasclcular blocks is demonstrated using the atrial extrastimulus technique. Patient 1, with a QRS pattern of “complete” left bundle branch block, manifested a QRS pattern of right bundle branch block at a shorter coupling interval, indicating that the left bundle could conduct. Patient 2, with a QRS pattern of right bundle branch block and “complete” left anterior hemiblock, manifested a pattern of left posterior hemiblock at a shorter coupling interval, indicating that the left anterior fascicle could conduct. Patient 3, with a normal QRS complex, showed left bundle branch block at shorter coupling intervals and then a pattern of right bundle branch block as the coupling interval was further decreased, indicating that functional left bundle branch block was incomplete. This demonstration of partial bundle branch block depends on a discordance of conduction time and refractory period, the bundle or fascicle with depressed conduction (incomplete block) having a shorter refractory period than the more normally conducting bundle or fascicle. This discordance may be related to the development of trifascicular block in patients with bifascicular block and a normal H-V interval. It is a predisposing factor in the complex patterns of aberrant conduction seen during supraventricular tachyarrhythmias with varying cycle lengths.
TL;DR: D discrete proximal left anterior divisional block resulted in a significant alteration in the sequence of ventricular activation, confirming the fascicular nature of the left ventricular conduction system.
Abstract: Electrocardiograms (ECG), McFee vectorcardiograms (VCG), and ventricular activation data were collected from 25 anesthetized dogs before, immediately after, and 4 weeks after surgically induced discrete left anterior divisional block. Left anterior divisional block resulted in minor ECG changes: small S waves developed in leads II, III, and aVF and the QRS complex was prolonged 5-15 msec (mean 9 ± 2.7 [SD] msec). Prominent VCG changes also occurred: maximal and terminal forces were shifted posteriorly, superiorly, and slightly leftward, the duration of the loop was increased 5-15 msec (mean 9.8 ± 2.8 msec), and the terminal portions of the loop were slurred. Epicardial surface mapping revealed a consistent area of 5-20-msec delay (mean 12 ± 5.1 msec) confined to the lateral-basal surface of the left ventricle. Transmural activation studies in this area invariably revealed 6-20-msec (mean 12.8 ± 4.8 msec) delays in Purkinje and 3-25-msec (mean 12.4 ±5.6 msec) delays in endocardial activation. The wave front propagated across the wall with normal velocity. Q waves developed due to a "window effect" in the area of delay. Combining division of the septal fibers with left anterior divisional block resulted in surface delays of greater magnitude with marked axis shifts toward the left. Despite the extensive interconnections of the left ventricular conduction system, discrete proximal left anterior divisional block resulted in a significant alteration in the sequence of ventricular activation, confirming the fascicular nature of the left ventricular conduction system. The septal division appears to be an integral part of this system. The methodology described in this paper can be used to readily differentiate between epicardial delay due to conduction delay and that due to intramural myocardial delay.
TL;DR: Intacardiac electrocardiography was performed in an 18-month-old child who had histologically confirmed Pompe disease, and it is proposed that the excess glycogen caused both the accelerated conduction through the atrioventricular node and the increased QRS forces by a mechanical or chemical action on the myocardial cells.
Abstract: The pathophysiological cause of the short PR interval usually associated with glycogenosis of the heart (Pompe disease) has not been explained. In an effort to define this abnormality, intracardiac electrocardiography was performed in an 18-month-old child who had histologically confirmed Pompe disease. The low right atrium to His bundle interval (LRA-H), a reflection of atrioventricular nodal conduction time, measured only 40% of the average LRA-H for this age. Treatment of this patient with a glycolytic enzyme lowered the skeletal muscle glycogen level, decreased ventricular electrical forces, and slightly lengthened the PR interval. It is proposed that the excess glycogen caused both the accelerated conduction through the atrioventricular node and the increased QRS forces by a mechanical or chemical action on the myocardial cells.
Patent•
02 May 1974
TL;DR: In this paper, a ventricular arrhythmia (or abnormal ventricular complex) monitoring technique for automatically generating an output in response to elevated low frequency content in the QRS portion of an incoming ECG wave, which is indicative of cardiac abnormalities, is improved by the addition of artifact noise detectors.
Abstract: A ventricular arrhythmia (or abnormal ventricular complex) monitoring technique for automatically generating an output in response to elevated low frequency content in the QRS portion of an incoming ECG wave, which is indicative of cardiac abnormalities, is improved by the addition of artifact noise detectors that temporarily interrupt the output in response to higher frequency muscle tremor and electrical interferences and to broad band, high amplitude noise and sudden baseline variations in the signal. The amplitude of the incoming ECG wave is normalized through an automatic gain control (AGC) input amplifier that receives variable gain control signals generated in accordance with the amplitude of prior QRS complexes. The variable gain control signals provide selectively variable threshold reference levels that are compared against output levels from the various detectors so that their sensitivity is automatically adjusted to match the available signal level.
TL;DR: It is suggested that widened QRS complexes during complete A-V block in acute inferior myocardial infarction have no prognostic significance.
Abstract: Twelve of 35 consecutive patients admitted with complete, atrioventricular (A-V) block complicating acute inferior myocardial infarction manifested widened QRS complexes The escape beats had the pattern of left bundle branch block in four patients, right bundle branch block in five patients and both left and right bundle branch block in three patients His bundle recordings in five patients with escape beats that had a left bundle branch block configuration revealed a His bundle potential preceding the widened QRS complex at His-V intervals of 45 to 60 msec Bradycardia-dependent left bundle branch block was demonstrated in two patients by His bundle pacing In three patients the conducted beats had a left bundle branch block configuration after critical lengthening of the R-R interval during second degree A-V block before or after the episode of complete A-V block In six patients whose escape beats had a right bundle branch block configuration, His bundle recordings did not reveal a His bundle potential preceding these beats Our observations suggest that widened QRS complexes with a left bundle branch block configuration could be due to an A-V junctional escape rhythm with phase 4 left bundle branch block Alternatively in association with a right bundle branch block configuration it is possible that the widened QRS complexes represent a ventricular or fascicular escape rhythm Two of 12 patients with widened QRS complexes died There were no significant differences in immediate mortality, 6 month mortality or mean peak serum glutamic oxaloacetic transaminase (SGOT) values between patients with narrow and widened QRS complexes This finding suggests that widened QRS complexes during complete A-V block in acute inferior myocardial infarction have no prognostic significance
TL;DR: The electrocardiographic manifestations of cardiac rupture could be attributed to acute cardiac tamponade, and there was a sudden, vagally-mediated bradycardia.
Abstract: To test the hypothesis that the electrocardiogram of cardiac rupture is due to acute cardiac tamponade, 27 episodes of cardiac tamponade were produced in ten open-chest dogs. During continuous monitoring of the electrocardiogram and the arterial and venous pressures, 10-30 cc of autologous, heparinized blood, or one of several other solutions, were intermittently infused into the pericardial sac until no effective blood pressure was recorded. The characteristic electrocardiographic findings of acute cardiac tamponade were peaked P waves, decrease of QRS complex voltage, left axis deviation of the QRS complex, deep T wave inversions, and ST-segment change. With the appearance of electromechanical dissociation, there was a sudden, vagally-mediated bradycardia. Because these changes are similar to those observed at the time of cardiac rupture, it was concluded that the electrocardiographic manifestations of cardiac rupture could be attributed to acute cardiac tamponade.
TL;DR: The fetal electrocardiogram configuration recorded by direct fetal electrode was studied in 32 patients during labour and notches in the P wave or R wave had no relation to the condition of the infant at birth.
TL;DR: The previously established criteria for the vectorcardiographic diagnosis of a direct posterior myocardial infarction, in general, adequately describes the vectors, but fails to distinguish it from the anteriorly oriented vector Cardiogram of normal individuals which occurs frequently enough to make the importance of this distinction a practical clinical problem.
TL;DR: Three patients with the Wolff-Parkinson-White (WPW) syndrome were studied and conduction of premature atrial depolarizations via the accessory pathway was possible when the His-Purkinje system was still refractory.
Abstract: Three patients with the Wolff-Parkinson-White (WPW) syndrome were studied using His bundle recordings and programmed atrial stimulation. In two of them conduction of premature atrial depolarizations via the accessory pathway was possible when the His-Purkinje system was still refractory. The consequent conduction delay in the His-Purkinje system resulted in re-entry phenomena at the ventricular level in one case, and possibly also in another. In the third patient short runs of supraventricular tachycardia could be elicited, which were due to a longitudinal dissociation within the atrioventricular node. During these paroxysms, ventricular activation occurred over both the anomalous and the normal paths. The resulting QRS complexes resembledfusion beats as indicated by their configuration andprecedingHpotentials.
01 Jul 1974
TL;DR: It was presumed that the original pattern of the cardiac conduction system might be manifested in poikilothermic animals, and that animals showing a lower heart rate in resting state might be able to maintain a capacity of increasing the heart rate greater than those showing a high heart rate.
Abstract: The RR interval and the partial conduction time in the electrocardiogram of vertebrates were studied from the viewpoint of comparative cardiology. They were important for the physiological or patho-physiological approach to the clarification of cardiac function. RR, PQ and QT intervals and QRS complex durations were measured on 245 electrocardiograms recorded from twelve vertebrate species. Cardiological data obtained from some other experiments and the results reported by other workers were referred to in discussion. Positive correlations were recognized in general among the partial conduction times in one another. However, positive correlations of RR-PQ, RR-QT and RR-QRS and a negative correlation on a bilogarithmic scale between the heart weight and the heart rate per minute in resting state were recognized only in homothermic animals. A relationship between the submaximal increasing ratio of heart rate and the heart rate in resting state was indicated approximately by a hyperbolic function. From the results obtained, it was presumed that the original pattern of the cardiac conduction system might be manifested in poikilothermic animals, and that animals showing a lower heart rate in resting state might be able to maintain a capacity of increasing the heart rate greater than those showing a high heart rate.
TL;DR: A patient with a variant of the pre-excitation syndrome who has paroxysmal tachycardia with a pattern of left bundle branch block and ventriculo-atrial dissociation is reported, suggesting that the patient has anomalous conduction between the lower segment of the A-V node and the ventricular septum (Mahaim fibers).
TL;DR: 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.
Abstract: 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).
TL;DR: Orthogonal lead electrocardiograms, using the McFee-axial reference system as modified for use in dogs, were obtained from 27 healthy mature Pitman-Moore minipigs anesthetized with phencylcidine and halothane to serve as a baseline of normal values for electrocardsiograms obtained from minipig results.
TL;DR: Frank vectorcardiograms in 21 patients with idiopathic hypertrophic subaortic stenosis and asymmetric septal hypertrophy, and 20 patients with severe aortic regurgitation were analyzed, finding vectors were significantly larger in AR than in AS.
TL;DR: The QRS complex of the electrocardiogram of patients with chronic obstructive lung disease (COLD) seemed to be of briefer duration (narrower) than the QRS of other patients.
TL;DR: Patients over age 65 with atrioventricular and intraventricular conduction defects were studied for periods of from two to five years and left bundle‐branch block and left anterior hemiblock, either alone or in association with any other fascicular block, were more common in the female patients.
Abstract: Four hundred and fifty-five patients over age 65 with atrioventricular and intraventricular conduction defects were studied for periods of from two to five years (average, twenty-six months). Data on the overall incidence of conduction defects, the sex incidence, the type of block, and the associated electrocardiographic abnormalities are presented. There was no ECG evidence of extension of the blocks based on prolongation of the P-R interval, a shift or an increase in axis, a shift of the block from one branch to another, or an increase in width of the QRS complex. Left bundle-branch block and left anterior hemiblock, either alone or in association with any other fascicular block, were more common in the female patients whereas right bundle-branch block was more common in the male patients.
TL;DR: In this paper, the authors recorded specialized fiber electrograms from selected sites along the His bundle and bundle branches during open-heart surgery in 26 patients, and the heart was then paced from the same recording sites.
Abstract: Specialized fiber electrograms were recorded from selected sites along the His bundle and bundle branches during open-heart surgery in 26 patients. The heart was then paced from the same recording sites. Stimuli applied to the proximal His bundle recording site always resulted in His bundle pacing, which was characterized by a stimulus artifact-to-QRS interval which equaled or very nearly equaled the previously recorded His bundle electrogram-to-QRS interval, and no change in QRS duration or waveform from that recorded with a conducted atrial beat. When stimuli were applied to distal His bundle recording sites, the response was variable: in some instances, ventricular pacing occurred; in other instances, His bundle pacing occurred; and in still other instances, ventricular pacing occurred when high stimulus amplitudes were applied, while His bundle pacing occurred when the stimulus amplitudes were reduced below a range of 0.5-3.5 ma. Stimuli applied to the right or left bundle branch recording sites always resulted in ventricular pacing. Therefore, when stimuli are applied to specialized fiber recording sites and His bundle pacing results, it is certain that the site of origin of the previously recorded specialized fiber electrogram is the His bundle, but when ventricular pacing results, the site of origin of the previously recorded specialized fiber electrogram could be the distal His bundle or the bundle branches.
TL;DR: An orthogenal VCG seems to clarify the equivocal situation in the ECG diagnosis of MI,Representing the phasic changes in the depolarization process, according to the difficulties in applying ECG criteria for anterior myocardial infarction.
TL;DR: Electrocardiograms recorded from patients with true posterior myocardial infarction show an abnormal anterior shift in the QRS forces, and measurements obtained on the basis of multivariate analysis were found to be useful in classifying records that could not be categorized by hand measurements.
Abstract: Electrocardiograms recorded from patients with true posterior myocardial infarction show an abnormal anterior shift in the QRS forces. Differentiation of these records from those of right ventricular hypertrophy has been recognized as a difficult problem for a long time. An attempt was made to establish criteria for separating electrocardiograms of posterior myocardial infarction from those of right ventricular hypertrophy exhibiting a similar pattern. Frank lead electrocardiograms obtained from 81 patients with posterior myocardial infarction were compared with electrocardiograms recorded from 71 patients with right ventricular hypertrophy. With two measurements that can be easily obtained, 70 percent of the posterior myocardial infarction records were classified correctly with 15 percent of the right ventricular hypertrophy records being misclassified. A set of three measurements for right ventricular hypertrophy correctly identified 55 percent of cases of right ventricular hypertrophy; however, 13 percent of the posterior myocardial infarction records were misclassified as right ventricular hypertrophy. With seven measurements obtained on the basis of multivariate analysis, 78 percent of the posterior myocardial infarction and 79 percent of right ventricular hypertrophy cases were correctly classified. These measurements were found to be useful in classifying records that could not be categorized by hand measurements. Classification procedures were also tested in 23 autopsy cases with results equal to or slightly better than those obtained in clinical samples. Several measurements on the QRS vector loop previously considered useful in the differentiation of right ventricular hypertrophy from posterior myocardial infarction gave disappointing results when tested in our samples.