Showing papers on "QRS complex published in 1976"

The QRS complex during myocardial ischemia. An experimental analysis in the porcine heart.

Abstract: Although ST segment deflections have been widely utilized as a means of assessing the degree of underlying ischemic injury, the relationship of QRS complex alterations to the ischemic process is poorly understood. In this study we made a beat-to-beat analysis of the QRS complex in terms of ventricular activation time (CT) and R wave voltage (V) in the acutely ischemic porcine myocardium and analyzed the relationship of these responses to changes in the area of ischemic involvement, altered myocardial energy demands, and plasma [K+]0 levels. With the onset of ischemia the QRS complex underwent a specific and reproducible biphasic sequence with an initial decrease in CT and V indicating a transient increase in the conduction velocity of the ischemic tissue. Subsequently both CT and V returned briefly to control and then increased dramatically, now indicating a marked decrease in conduction velocity. The time when CT first began to increase (Tc) was shortened by enlarging the area of ischemia or after an inotropic intervention and was lengthened by decreasing the area of ischemia or with administration of propranolol. Moreover Tc was found to be inversely proportional to plasma [K+]0 in the range 3.4-8.8 mM, above which the initial decrease in CT and V was no longer present. We conclude that this biphasic sequence of QRS alterations in early myocardial ischemia is attributable to a progressive leakage of potassium out of the ischemic cells which in turn alters both the time-course and transmural pathway of the activation process through the ischemic tissue. These changes are related to both inotropic state and the area of ischemic involvement.

Long-term evaluation of early repolarization syndrome (normal variant RS-T segment elevation).

Abstract: The electrocardiograms of 65 patients with the "early repolarization syndrome" (normal variant of RS-T elevation) were analyzed to delineate the features and evaluate the natural history of this electrocardiographic entity. Maximal follow-up was 26 years. The syndrome was characterized by (1) an upward concave elevation of the RS-T segment with distinct or "embryonic" J waves, slurred downstroke of R waves or distinct J points or both; (2) RS-T segment elevation commonly encountered in the precordial leads and more distinct in these leads; (3) rapid QRS transition in the precordial leads with counterclockwise rotation; and (4) persistence of these characteristics for many years although some intraindividual changes were common. Less commonly found were (5) tall R and T waves in the precordial leads; (6) "labile" or "juvenile" T wave patterns; (7) "pseudo-R" waves; and (8) "isolated T negativity syndrome." These changes commonly simulate pericarditis, myocardial ischemia, left ventricular hypertrophy and right bundle branch block.

Use of changes in the epicardial QRS complex to assess interventions which modify the extent of myocardial necrosis following coronary artery occlusion.

Abstract: The goal of this study was to determine if changes in the epicardial QRS complex after coronary artery occlusion (CAO) can be used to evaluate the efficacy of interventions designed to limit infarct size. Forty-one open-chest dogs with CAO were studied: 15 were controls, 18 received hyaluronidase and eight received propranolol starting 20 minutes after CAO. Epicardial ECGs were recorded at specific time intervals to analyze ST-segment elevation and changes in Q and R waves. Transmural specimens were obtained 24 hours after CAO from the same sites at which ECGs were recorded. Q wave development (deltaQ), R wave fall (deltaR), and their combination (deltaR + deltaQ) at 24 hours correlated with the extent of necrosis, as determined by myocardial creatine phosphokinase activity depression and histologic appearance. In the control group ST-segment elevation 15 minutes after CAO (ST15M) predicted changes in Q and R waves 24 hours later; in the treated groups, the same ST15M prior to drug administration resulted in significantly less QRS changes. Thus, 1) Q wave development and R wave fall 24 hours after CAO accurately reflect myocardial necrosis. 2) ST15M predicts subsequent changes in Q and R waves. 3) The efficacy of hyaluronidase and propranolol, agents previously shown to reduce myocardial necrosis, can be detected by less Q wave development and a smaller fall in R wave voltage.

New evidence for inferoposterior myocardial infarction on surface potential maps.

Abstract: Extensive body surface potential recording was performed in 22 patients 2 to 4 weeks after an acute inferoposterior myocardial infarction. Serial isometric projection maps were viewed millisecond by millisecond throughout ventricular excitation, and a second series of maps were examined after removal of the expected range of normal potential distribution. Three major findings outside the normal range appeared: (1) In 6 patients, an early zone of abnormal positivity developed in the left anterior chest at xiphoid level between 15 and 30 msec after onset of the QRS complex; (2) in 13 other patients, a large zone of positivity developed high on the left anterior chest (subclavicular region) between 30 and 60 msec after QRS onset; and (3) in 8 patients the long-lasting rim of negativity about the lower chest was strictly abnormal compared with the expected range. Thus, in 19 of 22 patients the potential map expression was outside the normal range, whereas only eight standard electrocardiograms revealed persistent Q waves with a duration greater than 30 msec. We believe the mid and late activation changes are related to ischemically induced alterations in the temporal sequence of ventricular excitation, not easily appreciated by conventional means of recording, but obvious with the departure map technique.

Alterations in ventricular contraction pattern in the Wolff-Parkinson-White syndrome. Detection by echocardiography.

Abstract: The effects of abnormal ventricular activation upon the contractile pattern of the ventricles in patients with the Wolff-Parkinson-White syndrome (WPW) remain uncertain. Therefore we compared the motion of the anterior right ventricular wall (RV), the interventricular septum (IVS), and left ventricular posterior wall (LVPW) on echogram in nine patients with WPW and one patient with a coronary sinus pacemaker (CSP) to 20 normal subjects. Normal subjects manifested posterior RV motion which began and reached maximal excursion at 175 and 366 msec (group mean), respectively, after the onset of the QRS complex; posterior movement of the IVS which started and peaked at 90 and 30 msec, respectively; and anterior contraction of the LVPW which began and peaked at 159 and 406 msec, respectively. Five of seven patients with Type A WPW demonstrated a localized area of premature contraction of the LVPW occuring during the initial 100 msec interval following the onset of the QRS complex which was accompanied by paradoxic anterior motion of the IVS. Thereby in Type A patients initial and maximal posterior motion of the IVS occurred later, 230 (P less than 0.001) and 400 (P less than 0.05) msec, and anterior motion of the LVPW occurred earlier, 75 (P less than 0.001) and 367 (P less than 0.05) msec as compared to normal. The amplitude and duration of early contraction could be related to the prominence of the delta wave during atrial pacing. Similar premature contraction was also observed in the patient with CSP during paced beats. One Type B WPW patient exhibited abnormal IVS motion while the additional patient manifested premature LVPW contraction similat to that seen in Type A patients. The contractile pattern of the right ventricular anterior wall was recorded in five of seven Type A Wolff-Parkinson-White patients and manifested prolongation of the interval from the onset of the QRS complex to the initial posterior movement (group mean 234 msec, P less than 0.05) as compared to normal. Thus echocardiography can be used to confirm the diagnosis and to improve understanding of the pathophysiology of the Wolff-Parkinson-White syndrome.

Electorcardiographic ST-segment analysis in the characterization of myocardial ischemia and infarction.

Abstract: The ST segments of the electrocardiogram (ECG) become elevated within 20 to 30 seconds after the onset of acute coronary occlusion and, when persistent, such changes offer a possible indirect marker of the extent and severity of myocardial ischemic injury and of eventual cell death. When ST-segment elevation on the epicardial ECG is measured 15 minutes after an acute coronary occlusion in the dog, a general correlation exists with biochemical changes, regional myocardial blood flow, and myocardial electrolyte alterations measured at 15 minutes, although when an effort is made to correlate the degree of such alterations with the magnitude of the ST-segment change there is considerable scatter. On the other hand, when the ST-segment elevation at 15 minutes is correlated with myocardial blood flow, histologic changes, and creating phosphokinase (CPK) depletion 24 hours later, the correlation is good. Possible mechanisms underlying ST-segment elevation are discussed, and data are reviewed which indicate that the epicardial ECG my be relatively insentive to subendocardial injury; in the experimental setting this problem may be partially corrected by the use of intramyocardial ECG leads. The extension of direct epicardial ECG maps to precordial ST-segment mapping poses additional problems that include reduced sensitively, problems due to reciprocal changes in the ECG at the body surface, surface contact of the electrodes, pericarditis, and individual variability in the rate of spontaneous regression of ST-segment changes. Such mapping appears reliable only for infarctions of the anterior and lacteral wall. Further research is necessary on analysis of the QRS complex, and use of vector leads. Despite these problems experimental and clinical studies indicate that precordial electrocardiographic analysis may be useful for detecting acute changes in the severity of ischemic injury over relatively short periods of time (2 to 4 hours). This indirect measure clearly will require correlation with specific markers of ischemic damage, but with further improvements it seems likely that analysis of serial ECG changes will evolve into a valuable and reliable nonivasive clinical tool for characterizing myocardial ischemia and infarction.

Alterations of right ventricular systolic time intervals by chronic pressure and volume overloading.

Abstract: Right ventricular (RV) systolic time intervals and hemodynamic parameters were determined by micromanometric techniques in 13 subjects with normal right ventricles (NRV). These data were compared to those of 16 patients with pulmonary hypertension (PH) or predominant pressure overloading and 13 individuals with uncomplicated secundum atrial septal defects (ASD) or predominant volume overloading. In PH, the QP2 interval tends to remain within the normal range due to reciprocal changes in isovolumic contraction (ICT) and ejection (RVET) times. Elevations of pulmonary artery diastolic pressure are associated with increases in the mean rate of isovolumic pressure rise (MRIPR) (r = 0.84), but the latter change does not fully compensate for the widened ventriculoarterial diastolic pressure difference and ICT becomes prolonged (P less than 0.001). Factors other than stroke index depression which may contribute to the decreased duration of RVET (P less than 0.001) include tricuspid regurgitation and elevation of pulmonary vascular impedance. In ASD, QP2 is significantly prolonged (P less than 0.025) due to a significant increase in RVET (P less than 0.005). In contrast to NRV, a linear correlation of RVET and stroke index was not present, which suggested an alteration of ejection dynamics in this group. Despite a high incidence of complete or incomplete right bundle branch block the interval from QRS onset to rapid RV pressure upstroke was not prolonged. This is most probably the result of peripheral bundle branch block of genesis of the QRS pattern by right ventricular hypertrophy.

An echocardiographic study of interventricular septal motion in the Wolff-Parkinson-White syndrome.

Abstract: Echocardiographic studies of interventricular septal motion were performed in 26 consecutive patients with the Wolff-Parkinson-White (WPW) syndrome and in ten normal subjects. All patients with types A or B pre-excitation were subclassified into groups I to IV on the basis of their electrocardiogram utilizing the method of Boineau and associates. In all 14 patients with type A (Group III or IV) pre-excitation, the motion of the interventricular septum and posterior left ventricular wall motion were normal. However, in 11 patients with type B (Group I) WPW an abnormal septal movement was noted. This was characterized in ten patients by an early systolic posterior motion, a subsequent anterior movement in mid systole, and the usual posterior septal motion beginning in late systole. In eight patients, including the one without early systolic posterior movement of the septum, the late systolic posterior movement was interrupted by a prominent septal notch. On e patient with type B (Group II) WPW was studied and exhibited normal septal and posterior wall motion. In one patient with a spontaneous change in the QRS complex from normal to a type B (Group I) WPW pattern, the septal motion was initially normal and abruptly changed following the first WPW beat. The onset of abnormal interventricular septal motion with type B pre-excitation QRS complexes strongly suggests that abnormal septal movement may be related to an altered sequence of ventricular depolarization during right ventricular pre-excitation.

Origin of epicardial ST-T wave potentials in the intact dog.

Abstract: Ventricular repolarization was analyzed by measuring epicardial potential distributions in intact dogs with single or multiple ectopic foci and a minimum at the terminal site(s) of excitation. During the latter half of the T wave the distributions became more complex, and two maxima evolved from the initial one at each ectopic site. The measured epicardial potentials were simulated by means of a model of ST-T wave events that is suitable for study of single and multiple ectopic beats with fusion, a a model we call 'SI model.' Intracellular potentials around the ventricles during repolarization were calculated from measured excitation sequences and known action potential shapes. The extracellular potentials around the ventricles were computed from the intracellular ones by a simplified ventricular geometry. The satisfactory agreement between the theoretical and measured extracellular potential distribution shows that the complex changes which occur throughout the ST-T wave are predicted well on the basis of changes in the intracellular potential distributions. In contrast to the well known lability of the T wave from beat, the results show that for any single beat the events of repolarization proceed in an entirely repeatable and deterministic fashion. The results present a way to directly represent cardiac extracellular events during the ST-T wave, a method analogous to the use of isochromes during QRS, and they imply that in the future it will by possible to achieve a more precise quantitative understanding of the events of the ST-T wave than thus far has been possible for QRS.

Selective versus non-selective His bundle pacing.

Abstract: His bundle pacing was achieved in 10 anaesthetized open chest dogs by stimulation from bipolar electrode catheters positioned in the aortic root and right heart. Recordings were taken directly through plunge wires from the right atrium, high ventricular septum, and epicardial sites on the right and left ventricles. Six types of response were seen during A-V junctional stimulation: (1) low atrial pacing; (2) combined atrial and His bundle pacing; (3) His bundle pacing; (4) combined atrial, ventricular septal, and His bundle pacing; (5) combined septal and His bundle pacing; and (6) ventricular pacing. Pacing of the His bundle in combination with the atrium and/or ventricular septum is designated as non-selective, whereas stimulation of the His bundle alone is considered selective pacing. Non-selective His bundle pacing can be recognized from the surface leads by changes in onset and amplitude of the QRS with appreciable T-wave alterations. Although electrode position was an important determinant of the type of pacing achieved, a variety of patterns of stimulation resulted from variation in the modalities of the pacing stimulus, ie, polarity, intensity, and duration. Unless these factors are considered, selective His bundle pacing may not be achieved.

Interventricular septal motion during preexcitation and normal conduction in Wolff-Parkinson-White syndrome: Echocardiographic and electrophysiologic correlation☆

Abstract: Interventricular septal motion was studied by echocardiogram in 20 consecutive patients with documented Wolff-Parkinson-White (WPW) syndrome before and during electrophysiologic evaluation using His bundle recordings and pacing techniques. Characteristic abnormal interventricular septal motion was seen in 8 of 11 patients with type B WPW syndrome (groups I and II). All eight patients had electrocardiographic patterns consistent with an anomalous pathway located in the anterior right ventricular wall (group I). In five of these eight patients normalization of the QRS complex for one or more beats was accomplished and produced normalization of the septal motion in four; whereas in the fifth patient, who had an underlying atrial septal defect, the abnormal septal motion remained abnormal. All nine patients with type A WPW syndrome (groups III to V) had normal septal motion both during total preexcitation and during normalization of the QRS complex. The normalization of the abnormal interventricular septal motion with normalization of the QRS complex in type B WPW syndrome strongly suggests that the abnormal motion is related to an abnormal sequence of ventricular depolarization during preexcitation. Furthermore, persistent abnormal septal motion after normalization of the QRS complex suggests that other factors such as right ventricular volume overload may be responsible. Likewise, when abnormal septal motion occurs in the presence of type A WPW syndrome, an explanation other than preexcitation must be sought.

The expression of normal ventricular repolarization in the body surface distribution of T potentials.

Abstract: Isopotential maps from 120 normal subjects were obtained from 192 simultaneously recorded electrocardiographic leads. Maps were plotted at 1 msec intervals during the QRS and 5 msec intervals during the ST-T deflection. Repetition of QRS features was evident during all but the first few msec of the initial half of serial T maps. This suggests similarities of the normal sequence of ventricular excitation and recovery. Such similarities have been demonstrated by direct studies but are not evident from other electrocardiographic examinations. Serial maps during later portions of the T wave showed decreasing intensity of potentials with little change of body surface locations. This also correlates with an established feature of ventricular repolarization, namely that potential difference boundaries with stable locations are widely distributed during part of that process. Findings suggest isopotential maps show features of ventricular recovery not apparent from less extensive examinations.

Vectorcardiographic study of aberrant conduction anterior displacement of QRS: another form of intraventricular block.

Abstract: Aberrant ventricular conduction was induced in 44 subjects by introduction of atrial premature beats through a transvenous catheter-electrode. Multiple patterns of aberrant ventricular conduction were obtained in 32 patients and, in the whole group, 116 different configurations were recorded. Of these, 104 showed a classical pattern of mono- or biventricular conduction disturbance. The pattern frequencies were as follows: right bundle-branch block, 28; left anterior hemiblock combined with right bundle-branch block, 21; left anterior hemiblock, 17; left posterior hemiblock combined with right bundle-branch block, 12; left posterior hemiblock, 10; complete left bundle-branch block, 10; and incomplete left bundle-branch block, 6. The remaining 12 configurations could not be classified into the usual categories of intraventricular blocks. In 7 of them, the alterations only consisted of trivial modifications of the QRS contour. In the other 5 instances, aberrant conduction manifested itself by a conspicuous anterior displacement of the QRS loop, with increased duration of anterior forces. The latter observation is worthy of notice, as it indicates that, in the differential diagnosis of the vectorcardiographic pattern characterized by prominent anterior forces, conduction disturbances should be considered a possible aetiological factor in addition to right ventricular hypertrophy, and true posterior wall myocardial infarction.

De Subitaneis mortibus. XVI. Intractable tachycardia in infancy.

Abstract: Intractable tachycardia in a boy proved fatal at the age of one year. A cousin still living has the same problem. Special electrocardiographic studies in the boy demonstrated a consistent abnormality which included complete atrioventricular dissociation with a normal atrial rate but a ventricular rate usually about 240 beats/minute; a His bundle comples preceded each QRS and all QRS complexes were narrow and uniform in configuration without a delta wave. At postmortem examination there were changes due to congestive failure and the heart was enlarged but otherwise normal except for the His bundle. In its midportion the His bundle was split into several thin and irregular longitudinally oriented strands, within which there were many areas of focal degeneration. There was no myocarditis and no focal degeneration elsewhere in the heart. Although the etiology of this process is uncertain, some possibilities are discussed.

Diagnosis of acute myocardial infarction in a community hospital: significance of CPK-MB determination.

Abstract: Twice-daily CPK-MB determinations were performed but not made availabe to the physicians of 179 consecutive patients with precordial pain admitted to a community hospital to evaluate the diagnostic importance of this isoenzyme. Physician decision was based upon history and once-daily ECG and total enzymes (CPK, SGOT, LDH). Following hospital discharge, each patient's clinical record was reviewed to determine the physician diagnostic decision. The patients were subdivided into three groups. The first group consisted of 46 patients with diagnostic QRS changes and elevated total enzymes. All 46 had physician diagnosis of acute myocardial infarction and CPK-MB was present in 44 (96%). The second group included 55 patients with nondiagnostic QRS but elevated total enzymes. Physician diagnosis was acute myocardial infarction in 28 (51%) but 16 (57%) of these had no CPK-MB. The third group contained 50 patients with nondiagnostic QRS and normal enzyme levels. Six (12%) had physician diagnosis of acute myocardial...

Candida myocarditis without valvulitis

Abstract: Thirty-one patients with systemic candidiasis at postmortem examination were found to have Candida involvement of the myocardium without valvulitis. Retrospective examination of their clinical course demonstrated that a new conduction disturbance was seen in 10, supraventricular arrhythmias in 5,QRS changes mimicking myocardial infarction in 3, and pronounced T wave changes in 13. Hypotension or shock was seen in 13 patients and could not be explained by coexistent bacteremia or blood loss in 8. One patient died suddenly. Of 19 patients with systemic candidiasis without myocardial invasion, 4 had minor T wave changes and one had a supraventricular arrhythmia. Candida invasion of the heart significantly complicates the clinical course in systemic candidiasis and should be suspected when a young person without preexistent heart disease has cultures positive for a Candida organism, a significant arrhythmia, conduction distrubance or other dramatic QRS change. The effect of therapy on Candida invasion of the heart is unknown.

Orthogonal electrocardiogram, apex cardiogram, and atrial sound in normotensive and hypertensive 50-year-old men.

Abstract: The prevalence of signs of heart involvement was studied non-invasively in a group of untreated hypertensives (n=35) and a reference group (n=73), all derived from a random population sample of 50-year-old men. Signs of left ventricular hypertrophy were studied by means of orthogonal electrocardiography and conventional electrocardiography. Signs of decreased distensibility of the left ventricle were studied by apex cardiography and registration of atrial sounds. Left ventricular hypertrophy among hypertensives was significantly more common according to orthogonal electrocardiography (33%) than according to conventional electrocardiography (9%), indicating that the former may be a better method for detection of left ventricular hypertrophy than the latter. In the hypertension group the amplitude of the R wave in lead X on orthogonal electrocardiography was positively correlated to casual diastolic blood pressure (r=0-40) and to diastolic blood pressure after one hour's rest (r=0-65). The degree of pressure load leading to left ventricular hypertrophy seems to be better reflected by resting than by casual blood pressure. There was no hypertensive subject with both signs of left ventricular hypertrophy on orthogonal electrocardiography and either an a/H ratio over 15 per cent or an abnormal atrial sound, indicating two different forms of cardiac involvement as the result of hypertension. Casual blood pressures became normal during rest in hypertensives with a/H ratio over 15 per cent on apex cardiography or abnormal atrial sound, not in hypertensives with signs of left ventricular hypertrophy on orthogonal electrocardiography.

Electrocardiographic and vectocardiographic findings in Friedreich's ataxia.

Abstract: Electrocardiographic and vectocardiographic changes are frequent in Friedreich's ataxia. In one of 35 patients both tests were normal. The vectocardiogram is more explicit in demonstrating the severity of the QRS changes with a right ventricular hypertrophy pattern present in 60% of cases. Serial examination of ECG tracings are recommended to monitor the cardiomyopathy in this progressive neurological disorder, in order to detect the onset of congestive heart failure, significant tachyarrythmias, or obstructive cardiomypathy.

Cardiac effects of amitriptyline in rats.

Abstract: The effect of intravenous amitriptyline (0.5-2 mg/kg) on heart rate, blood pressure, ECG, and electrolytes in plasma and heart muscle was studied in rats. In addition, the effect on monophasic action potentials was studied in rats with open chest. Amitriptyline caused a significant decrease in blood pressure and heart rate and a significant prolongation of QRS and PQ duration. At the time of maximal QRS prolongation (mean +94%) the duration of monophasic action potentials was virtually unchanged. Beta-adrenergic blockade by means of pretreatment with 0.1 mg propranolol did not influence the amitriptyline-induced prolongation of QRS duration. Amitriptyline administration causing obvious QRS prolongation induced no detectable changes in plasma and heart muscle electrolytes. The results contradict adrenergic dominance or marked imbalance between intra- and extra-cellular electrolytes as a cause of the ECG changes. The present data indicate that the amitriptyline effect is compatible with a direct quinidine-like action on the heart, resulting mainly in a slowing of impulse propagation in the intracardiac conduction system.

The U wave and aberrant intraventricular conduction. Further evidence for the Purkinje repolarization theory on genesis of the U wave.

Abstract: The Purkinje system repolarization theory on the genesis of the U wave was tested by correlating the incidence of aberrancy of atrial premature systoles with the timing of the U wave and other measurements in 126 electrocardiograms selected from 6,000 records. Coupling (R s -R p ) intervals were measured from the onset of the QRS complex of a sinus (s) beat to that of the premature (p) beat, and 149 different R s -R p intervals were studied. Criteria used for diagnosing aberrancy were significant changes in the QRS amplitude and significant alterations in the QRS contour. The incidence of aberrancy was plotted against (1) the R s -R p interval; (2) the ratio between the R s -R p and R s -R s intervals (the basic cycle length); (3) the ratio between P s -P p (the interval from a sinus P wave to a premature P wave) and P s -P s (the sinus cycle length); (4) the interval from the end of the preceding T wave to the premature QRS complex (T-R p interval); (5) the interval from the apex of the U wave of the sinus beat to the premature QRS complex (aU-R p ); and (6) the interval from the end of the preceding U wave to the premature QRS complex (eU-R p ). As expected, a decrease in either of these values tended to increase the incidence of aberrancy. However, smooth S-shaped curves were noted with aU-R p and eU-R p intervals only. The correlation was much poorer with the other four measurements. Aberrancy with a typical right or left bundle branch block pattern was observed only when the premature QRS complex occurred before the apex of the U wave, the left bundle branch block pattern occurring with greater prematurity. It is concluded that the U wave most likely represents phase 3 repolarization of the Purkinje system, and propagation of supraventricular impulses during this period is the cause of aberrant ventricular conduction.

Intra-His bundle blocks (102 cases).

Abstract: Some intra-His bundle (intra-HB) blocks escape the routine exploration of the His bundle and are confused with supra- or infrahisian blocks. We believe that a more accurate exploration (recording of His bundle activity successively at the proximal end and the distal end of the His bundle, dynamic tests and drug injection) is needed to detect some concealed cases, mostly paroxysmal intra-HB blocks. In this series of 102 cases of intra-HB blocks, 20% had no criteria of AV block on the surface electrocardiogram, and only 4% had an intact conduction pattern (normal PR interval and normal QRS complexes.) A first degree intra-HB block was found in 35% (15 cases with a normal PR interval), a second degree intra-HB block in 23% and a thired degree intra-HB block in 42% of the cases (unidirectional in 4 cases). Of the 43% having an isolated intra-HB block, most were elderly women with a chronic third degree AV block.

Concealed intraventricular conduction in the His bundle electrogram.

Abstract: Multiple areas of concealed intraventricular conduction are deduced on the basis of aftereffects observed in His bundle recordings. Electrocardiograms and His bundle recordings are presented from two patients with unstable bilateral bundle branch block, the instability of which depended on the interval at which ventricular depolarization was initiated by sinus or paced impulses. This circumstance allows postulation of 1) concealed transseptal retrograde penetration of the left bundle branch system; 2) concealed transseptal retrograde penetration of the right bundle branch system; 3) alternate beat Wenckebach phenomenon with two areas of block in the bundle branch system with concealed penetration of the proximal area; 4) concealed re-entry in the right bundle branch system during an H-V Wenckebach cycle with resetting of the sequence of 2:1 H-V block and return of the re-entry wave to the A-V node causing subsequent A-H block; 5) proximal 2:1 block and distal Wenckebach block producing only two consecutively blocked beats; and 6) infrahisian Wenckebach block with changes both in A-V conduction and QRS contour.

Vectorcardiographic study on left ventricular hypertrophy in spontaneously hypertensive rats.

Abstract: To observe cardiac changes in spontaneously hypertensive rats (SHR) functionally, the vectrocardiographic approach was tried, applying the Takayasu lead system to rats. This vectrocardiogram (VCG) was shown to be sufficiently good to detect left ventricular hypertrophy (LVH) in SHR. VCG in SHR showed specific features, some of which were left upward deviation of the maximum QRS vector in the frontal plane, an increased magnitude of the maximum spatial QRS vector, and prolongations of such indices as the QRS duration, time to the maximum spatial QRS vector and QT interval with abnormal ST-T changes. The P wave of SHR in the X scalar electrocardiogram, lower and wider than that of Wistar-Kyoto rats may also be a significant feature of LVH in SHR. The angle of the maximum QRS vector in the horizontal plane was not proven to be a suitable index of LVH in SHR. Most of the histometrical findings were closely correlated to blood pressure. Some of the vectrocardiographic findings were significantly correlated both to blood pressure and to some of the characteristic findings of LVH, such as the weights of the heart and the left ventricle and so forth. This experiment also indicated that LVH in SHR was not limited only to quantitative myocardial hypertrophy. It also seemed to be related to reversible or irreversible qualitative changes of coronary arteries or myocardium, such as myocardial fibrosis. This vectrocardiographic method was shown to be useful in obtaining various information about the cardiovascular system in rats, especially in SHR, and it seemed to be helpful for further understanding hypertensive cardiac diseases in humans.