Posterior Bundle Research Articles

Failure of Surgery in Preexcitation: Correlation with Pathologic Findings

A 37-year-old man with mitral stenosis and recurrent drug-resistant paroxysmal atrial fibrillation, paroxysmal supraventricular tachycardia, and preexcitation, underwent two surgical attempts to ablate an anomalous pathway (AP). Electrophysiologic study demonstrated a left posterior AP with a short antegrade refractory period. Epicardial mapping at the time of mitral valve replacement (left lateral thoracotomy) suggested a posterior right AP. Mitral valve replacement and incision of the left atrial wall failed to cure preexcitation. Epicardial mapping at a second operation (median sternotomy) demonstrated a subepicardial left posterior AP. Right atrial and atrial septal incisions failed to cure preexcitation. Serial section of the atrioventricular rings and conduction system demonstrated an intact left posterior anomalous atrioventricular muscle bundle with surgical incision placed above the plane of the mitral anulus.

The conduction system in hypoplasia of the aortic tract complex.

This is a study of the course of the conduction system in two cases of hypoplasia of the aortic tract complex, one with mitral stenosis and the other with mitral atresia. In both there was a posterior atrioventricular (AV) node which formed the AV bundle. In case 1 the bundle was short and bifurcated early. The branching bundle gave off a large left bundle branch (LBB), many Mahaim fibers to the septum and a small right bundle branch (RBB). In case 2 the AV node was divided into two parts which formed two posterior bundles which joined together to form a short branching bundle. Instead of a LBB there were profuse Mahaim fibers passing from the branching bundle to the depths of the ventricular septum. The RBB was large. The abnormalities seen in the conduction system particularly in the LBB are discussed from the embryologic stand-point.

Prognosis for patients with congenital heart disease and postoperative intraventricular conduction defects.

Intraventricular conduction defects are common following repair of various forms of congenital heart disease. Such defects may affect adversely the long-term prognosis of patients in whom cardiac hemodynamics were adequately restored. Review of previously published studies suggests that the site of the conduction defect may be the reason for the different prognoses reported for patients from different institutions. The so-called "trifascicular block" pattern which sometimes occurs following open heart surgery is probably due to a more extensive lesion to the branching and penetrating parts of the His bundle rather than additional injury to the posterior left bundle branch fibers. Transient complete heart block in the immediate postoperative period seems to be a predictor for late development of complete heart block or sudden death at least as powerful as right bundle branch block and left anterior hemiblock.

Effects of lesions of various medial forebrain bundle components on lateral hypothalamic self-stimulation

Unilateral lesions of various medial forebrain bundle components were assessed for their effects on lateral hypothalamic self-stimulation. Damage of areas containing nigrostriatal dopaminergic or ascending noradrenergic neurons had negligible effects on bar pressing, tail moving and alley running for hypothalamic stimulation. Lesions which appeared to destroy most or all of the catecholaminergic fibers in the posterior medial forebrain bundle virtually eliminated reinforced bar pressing and tail moving, but only partially suppressed alley running. The results suggest that brain stimulation reinforcement of the bar press and tail movement tasks depends upon the integrity of neural tissue in the area of the catecholaminergic pathways of the medial forebrain bundle, but not upon specific dopaminergic or noradrenergic systems. The data further suggest that the reinforcement of alley running is at least partially mediated by different neural tissue (possibly non-catecholaminergic) at the level of the posterior medial forebrain bundle lesions.

Fibroblast-collagen interactions in the formation of the secondary stroma of the chick cornea.

Fibroblasts invade the primary corneal stroma of the 6-day-old chick embryo eye. The way in which these cells build the secondary stroma has been studied by microscope examination of the stroma during the subsequent 8 Days. Eyes were embedded in low viscosity nitrocellulose, and 30-micrometer tangential sections of cornea were cut and stained with azan (giving blue collagen and red cells). These sections were sufficiently thick to include enough cells and collagen for stromal organization to be visible under Nomarski optics. Three days after invasion, the fibroblasts extend along collagen bundles in the posterior region of the stroma; surprisingly, fibroblasts near the epithelium are more rounded. The collagen itself is organized in orthogonal bundles rather than in sheets. Measurements show that posterior bundles increase in size with time while anterior stroma si similar in diameter to primary stroma. These observations confirm that the epithelium continues to deposit primary stroma up to at least the 14th day. They show, moreover, that fibroblasts deposit collagen fibrils on extant stroma and that the farther a bundle is from the epithelium, and hence the longer the period since it was first laid down, the wider it is likely to be. Analysis of the results and existing data on hyaluronic acid levels in the stroma suggests that Bowman's membrane, the region of anterior stroma that remains uncolonized by cells, is, during this period at least, primary stroma laid down but as yet unswollen.

The Surgical Treatment of Wolff-Parkinson-White Syndrome: Evolution of Improved Methods for Identification and Interruption of the Kent Bundle

Fifty patients have been operated upon for the tachyarrhythmias associated with Kent bundles. The indications for operation were supraventricular tachycardia (SVT) in 23 and life-threatening tachyarrhythmia in 27. Among the unusual variants noted were multiple Kent bundles in 6 patients and Kent bundles that conducted only retrograde in 3. Forty-nine patients underwent attempted interruption of the bundle of Kent followed by His bundle division in 6. One had elective division of the bundle of His. The surgical problems occurred in 13 patients with posterior septal Kent bundles. A new approach is outlined for this group. Division of the Kent bundle was successful in 31 patients, but 2 deaths occurred from cardiomyopathy. Seven patients had successful control of SVT by His bundle interruption. One patient with postoperative retrograde conduction has the SVT controlled with drugs. Eight have postoperative delta waves, but their SVT is controlled with drugs. There were 3 failures.

Hypothalamic influences on the electrical activity of the olfactory pathway

By means of evoked potentials a direct efferent connection was found to run from the posterior hypothalamus and medial forebrain bundle to primary olfactory structures (olfactory bulb, olfactory tubercle and prepyriform cortex). The pathway from the hypothalamus to the olfactory bulb follows in the lateral olfactory tract at a conduction velocity 5–10 m/sec. The olfactory tubercle functions as a relay station for the efferent fibers from various sources, running to the olfactory bulb. In animals with electrodes chronically implanted in the olfactory structures, hypothalamic stimulation gives rise to a prolonged train of hypersynchronous bursts of activity (40–50 Hz), which resemble the arousal reaction. This response is modified by transecting the cervical sympathetic trunk. By pathways still to be defined, potentials are evoked in the olfactory bulb by stimulation of the cervical sympathetic trunk and the termination of these sympathetic fibers shows a common postsynaptic neuronal pool with axons of hypothalamic origin. Epinephrine topically applied to the olfactory mucosa induced hypersynchronous activity in olfactory structures, quite similar to that consequent to hypothalamic stimulation. These results suggest a multichanneled hypothalamic modulation of olfactory input.

Electrocardiographic Abnormalities in Alcoholic Cardiomyopathy: A Study of 65 Patients

Electrocardiograms of 65 patients with alcoholic cardiomyopathy seen over a five-year period were reviewed. ST segment and T wave abnormalities, left ventricular hypertrophy, biatrial enlargement, left atrial enlargement, premature ventricular contractions, prolonged PR interval, and left anterior hemiblock are the most frequently encountered abnormalities. A combination of left ventricular hypertrophy and biatrial enlargement with or without left anterior hemiblock is most specific, Atrial flutter or fibrillation, pathologic Q waves, and bifascicular block are not uncommon findings, while isolated right atrial or right ventricular abnormalities, and isolated posterior hemiblock or right bundle branch block are rare. Electrocardiographic changes are in general similar to those seen in any diffuse cardiomyopathy and reflect biventricular involvement.

The conducting tissues in congenitally corrected transposition.

The histopathological findings are reported in 11 cases of congenitally corrected transposition. For the purposes of this investigation, only hearts with a well-formed septum separating two ventricular sinuses were classed as corrected transposition. We did not, therefore, study any examples of single ventricle with inverted outlet chamber. Five of the cases formed the basis of a preliminary report, in which the distribution of conducting tissues in the anomaly was shown to differ from that reported in previous investigations. The six new cases confirmed this distribution. Thus, in all cases, the connecting atrioventricular node was anteriorly situated in the right atrium at the lateral junction of pulmonary and mitral valves. An anteriorly situated bundle descended into the morphologically left ventricle (right-sided) and encircled the anterolateral quadrant of the pulmonary outflow tract before descending on the anterior septum and bifurcating. The bundle branches were inverted. This distribution was observed in specimens with intact septa (three cases) and in specimens with ventricular septal defects (eight cases). In the latter cases the conducting tissues were related to the anterior quadrants of the defects. One case was of particular interest since the posterior node in the position of the normal atrioventricular node also made contact with the ventricles via a posterior bundle. In all other specimens this node was hypoplastic and did not have ventricular connections. It is considered that this finding provides a link with previous descriptions of posterior conducting tissue in congenitally corrected transposition. The findings are discussed with relation to the development of complete heart block in this anomaly.

Differentiation of hypothalamic feeding and killing

Bipolar electrodes were chronically implanted in the posterior lateral hypothalamic-medial forebrain bundle area of male Long-Evans rats. Animals which displayed either stimulus-bound feeding or stimulus-bound killing were trained to self-stimulate and tested while given the opportunity to eat or kill during self-stimulation. Average duration of barpressing was greater in the presence of the goal object appropriate to the stimulus-bound behavior, suggesting a differentiation of hypothalamic mechanisms of feeding and killing.

Intraventricular conduction disturbances and coronary artery disease: Clinical, hemodynamic and angiographic study

The clinical, hemodynamic and angiographic findings of 42 patients with coronary artery disease and electrocardiographic and vectorcardiographic evidence of an intraventricular conduction disturbance are reported. All patients were evaluated because of symptomatic heart disease, and they represent 7 percent of patients with coronary artery disease studied. Right bundle branch block was present in 6, left anterior hemiblock in 18, left anterior hemiblock with right bundle branch block in 9 and left bundle branch block in 8 patients; only 1 patient had right bundle branch block with left posterior hemiblock. Angina pectoris was present in 79 percent. Congestive heart failure and cardiomegaly were common in patients with left bundle branch block and left anterior hemiblock with right bundle branch block. Transmural myocardial infarction on electrocardiogram and vectorcardiogram was common (55 percent), involving the anterior wall of the left ventricle in 72 percent. Eight patients with left bundle branch block or left anterior hemiblock with right bundle branch block had a prolonged P–R interval. Patients with right bundle branch block had normal left ventricular function, end-diastolic volume and ejection fraction, and predominant three vessel coronary disease. In the absence of a transmural myocardial infarction, left anterior hemiblock was associated with normal end-diastolic volume and ejection fraction. More than half of the patients with left anterior hemiblock had single vessel disease. Patients with left bundle branch block or right bundle branch block with left anterior hemiblock had almost uniformly abnormal left ventricular hemodynamics, end-diastolic volume and ejection fraction, and the majority had double or triple vessel disease. The single patient with left posterior hemiblock and right bundle branch block had normal left ventricular function. All the patients with abnormal left ventricular function had abnormal anterior or apical systolic wall abnormalities, or both. All the patients, except the one with left posterior hemiblock and right bundle branch block, had significant disease of the left anterior descending coronary artery. We conclude that the hemodynamic derangements found are correlated more with the intraventricular conduction disturbance than with the extent of the coronary artery disease. The only significant relation with coronary artery disease was the finding of major disease of the left anterior descending coronary artery in all but one patient.

Intermittent trifascicular block: Different mechanisms of conduction disturbances in the bundle branches

Analysis of the electrocardiograms of a patient with acute anterior wall myocardial infarction revealed the development of fixed left anterior hemiblock and tachycardia-dependent intermittent conduction in the left posterior branch and right bundle branch systems, with a higher critical rate for conduction in the former system. The electrocardiograms provided a classic illustration of this type of trifascicular block. Both grade I and type I (Mobitz) blocks of atrioventricular (A-V) conduction are attributed to conduction disturbance in the left posterior branch system. The distinction made between the functional nature of type I (Mobitz) block and the organic nature of type II block is criticized especially in the presence of a bundle branch block pattern. Failure of conduction of 3 consecutive impulses in the left posterior branch system, shown in some tracings, is attributed to 3 different electrophysiologic mechanisms: (1) conduction through an incompletely repolarized posterior branch due to pathologic prolongation of its functional refractory period (phase 3 block); (2) enhanced phase 4 depolarization (phase 4 block); and (3) retrograde activation of the posterior branch by an impulse traveling down the right bundle. Regular alternation of the second and third mechanisms occasionally gave rise to long periods of consistent block in the posterior branch. Other tracings demonstrated that successful conduction in the posterior branch could perpetuate transmission failure in the right bundle through retrograde activation of the right bundle branch system. The value of deductive analysis in unraveling complex disturbances of the cardiac rhythm is illustrated.

Morphine dependence in rats with medial forebrain bundle lesions.

Rats with posterior medial forebrain bundle (PMFB) lesions and control rats were administered morphine chronically for 4 or 5 days via implanted subcutaneous silicone reservoirs. Following cessation of morphine administration after five days, PMFB rats showed less withdrawal-induced weight loss than control rats. Other PMFB and control rats were subjected to forced drinking of morphine solution for 9 days. PMFB rats consumed the morphine solution much more readliy than control rats, whereas intake of a quinine solution was similar in two other PMFB and control groups. These results suggest that the addictive and dependence properties of morphine may have separate mechanisms and based on previously reported neurochemical effects of PMFB lesions, that biogenic amines may be differentially involved in such mechanisms.

Behaviorally determined neurophysiological properties of MFB self-stimulation fibers

A number of experiments have demonstrated that such neurophysiological properties as latent addition, neural refractoriness and temporal summation can be behaviorally measured in double pulse studies of the self-stimulation system of the rat. Since these phenomena have been investigated exclusively in the posterior lateral hypothalamic medial forebrain bundle (PH-MFB) or in the ventral tegmental area of the midbrain, the present experiment investigated these properties in an anterior area of the MFB. Eight rats were tested with PH-MFB electrodes and nine rats were tested with anterior preoptic electrodes (POA-MFB). The double pulse derived self-stimulation curves revealed: (a) a higher overall rate of responding for PH-MFB self-stimulation than for POA-MFB self-stimulation even though a higher current level was needed for POA-MFB self-stimulation; (b) refractory period differences between POA-MFB and PH-MFB electrodes; (c) evidence for latent addition; and (d) evidence for temporal summation. These results are discussed in terms of self-stimulation mapping studies of the rat diencephalon, the anatomy of the MFB, and previous double pulse self-stimulation studies.

Effect of trimethadione on the self-stimulation phenomenon.

The effects of the anticonvulsant drug trimethadione on the self-stimulation (S.S.) phenomenon are studied on rats. S.S. is elicited via electrodes implanted in the posterior medial forebrain bundle (M.F.B.). Following administration of trimethadione (325 mg/kg i.p.) a tendency toward improvement of S.S. is found; this trend is not statistically significant. The fact that no change of S.S. is observed in the areas of the posterior M.F.B. where seizures rarely occur is discussed in the light that the high rates of S.S. obtained from these areas might be related to the absence of disruptive epileptiform activity. It is concluded that the high rates of S.S. usually obtained from the posterior areas of the M.F.B. may be due to properties such as the involvement of these areas in high-drive behavior and facilitation of motor activity.

Neural mechanisms for sodium appetite: hypothalamus positive-hypothalamofugal pathways negative

Previous studies showed that lesions of the lateral or ventromedial hypothalamus impair sodium appetite but that lesions of the anterior or posterior medial forebrain bundle or periventricular system which carry hypothalamofugal fibers have no observable effect. In the present study other known or potential hypothalamofugal pathways were disjoined with no observable effect upon sodium appetite. Lateral hypothalamic lesions completely abolished sodium appetite under the same experimental conditions. It was concluded that no single neural pathway is necessary for transmission of hypothalamic natrorectic functions. In addition to data on sodium appetite, observations on disturbances of feeding behavior following certain subthalamic lesions are described, and motor and motivational functions of the subthalamus and hypothalamus are discussed.

The muscle structurn of human stomach and its relation to the development of gastric ulcers with special reference to the longitudinal muscle fibers

This study presents a new technique to observe the structure of gastric smooth muscle layers by means of the combined use of “mucosa stripping technique” and “nitric acid treatment”. The mucosa stripping technique has been described elsewhere. After the procedure, the specimens are re-emersed into 20% nitric acid solution for 3 to 7 days. By the time, the muscle fibers contract tightly and the interstitial fibrous tissues become swollen and fragil, and they are easily removed by forceps in running water. Leaving muscle structure is solidly delineated.By this method, the author explored the detailed structure of three layers of gastric smooth muscles and individualized the special muscle bundles; namely, “anterior medial oblique muscle bundle”, “posterior medial oblique muscle bundle” and “border circular muscle bundle”. These muscle bundles constitute, so-called, “upper strain zone” in relation to the development of peptic ulcers at about the gastric angulus where almost all uclers locate.Special interest is emphasized on an existence of “lesser curvature longitudinal muscle bundle” which is confined to the area of upper strain zone and tapering off in gradual fusion with the circular muscle bundles. Although, the functional signfiicance of these muscle bundles remains for the future study.

Floral Development, Anatomy, and Embryology of Collinsia heterophylla with Some Notes on Ten Other Species of Collinsia and on Tonella tenella

The apex that produces the decussate leaf primordia also produces the "whorls" (separated close spirals) of floral primordia in the terminal inflorescence of Collinsia heterophylla, with the only morphological change during the transformation being an increase to about twice the size. A two-layered tunica surrounding a densely staining corpus occurs in vegetative, inflorescence, and floral apexes. Flowers of C. heterophylla are hypogynous, sympetalous, zygomorphic, and bicarpellate, and the four stamens and one staminode are epipetalous. This species, in common with other members of the Scrophulariaceae, has its floral organs produced in the sequence of sepals, stamens, petals, carpels, and ovules. Collinsia and Tonella, which have a distinct staminode, appear to occupy an intermediate position in a postulated series in evolutionary reduction of the androecium in the family. In the base of the receptacle 10 bundles (five median sepal alternating with five joint lateral sepal-petal bundles) diverge outward, leaving gaps. The staminode-dorsal carpel bundle is undiverged from the posterior median sepal bundle at origin but soon separates from it tangentially. The median sepal gaps soon close, and almost immediately the four stamen bundles diverge, leaving large gaps which gradually close. Above this level one dorsal carpel trace arises from the vascular cylinder, and the other separates tangentially (or obliquely) from the staminode bundle. Shortly after its divergence a dorsal carpel bundle gives rise to two small laterals. Slightly below the base of the ovary two pairs of lateral carpel bundles arise from the vascular cylinder before it splits to form the two ventral carpel complexes. The latter enter the axis of the ovary in the plane of the septum, and thus each is probably composed of two ventral traces from adjacent carpels. Two branches of each ventral carpel complex enter the placentae and supply the ovules. One other branch from each ventral carpel complex passes upward and outward through the septum. It divides, and the halves enter different carpels, where they merge with the dorsal carpel bundles near the top of the ovary-an unusual condition. Differentiation of provascular tissue proceeds acropetally in the midrib bundles of leaves, bracts, sepals, and petals and in the stamen, staminode, and all carpel bundles. The order of appearance of provascular tissue in the floral organs is the same as the order of the initiation of those organs. Xylem lignification is discontinuous in the main bundles of leaves, bracts, and all floral organs. The direction of lignification is mainly acropetal in the median leaf, sepal, and dorsal carpel bundles, largely basipetal in the stamen and staminode bundles, and about equally acropetal and basipetal in the bract, lateral sepal, and ventral carpel bundles. No lignified xylem is found at any time in the base of the stamen, staminode, and dorsal carpel bundles connecting these to the receptacular vascular tissue. The provascular and mature phloem connection is complete, however. Microsporogenesis is similar to that in most angiosperms, and the single pollen grains are shed in the two-celled stage. As in other members of the Scrophulariaceae, the nuclei of tapetal cells of Collinsia divide mitotically, and the two nuclei may then fuse or they may divide and the four resulting nuclei fuse. The maximum growth rate of pollen tubes in styles was calculated to be approximately 2 56 mm per hour in the conditions under which the plants were grown. In the essentially campylotropous, unitegmic, tenuinucellate ovules a single archesporial cell enlarges to form the megaspore mother cell. This undergoes meiosis, forming a linear tetrad of which the chalazal spore functions to produce an eight-nucleate megagametophyte. Development is thus of the Polygonum type. Polar nuclei fuse before double fertilization occurs. The megagametophyte of C. heterophylla differs only in certain details-for example, time of disintegration of antipodals-from that in other members of the Scrophulariaceae. Embryo development is probably of the Onagrad type. Endosperm development is cellular. The endosperm cell nearest the chalaza early develops into a massive binucleate haustorium, and several (usually four) endosperm cells in the micropylar end form uninucleate haustoria. The centrally located cells divide to form the endosperm proper. In the mature seed all that remains of the integument is the endothelium, the outer epidermis-which consists of large cells that have thin tangential and thick (non-lignified) pitted radial walls-and a few intervening cells where the seed was attached to the placenta. The endosperm at seed maturity consists of thick-walled (non-lignified) cells filled with large droplets of oil and tiny granules of protein. The close relationship among species of Collinsia (C. heterophylla, C. concolor, C. austromontana, C. tinctoria, C. stricta, C. arvensis, C. bruceae, C. solitaria, C. verna, C. corymbosa, C. multicolor) and of Tonella tenella to Collinsia is supported by studies of their vascular anatomy, organography, and gametophyte development. No characters of internal structure can be used to distinguish among them.

STUDIES ON THE CONSTITUTION OF MUSCLE LAYERS OF HUMAN STOMACH

The muscle layers of human stomach in 51 cases of stomach specimens were studied after stripping the mucosa. Specimens included 5 cases of totally resected and 46 of partially resected specimens. All specimens have no gross pathological finding on the gastric portion.1. Oblique muscle: The oblique muscle was divided into two groups. The first group originates from circular muscle of the esophagus and distributes over the gastric corpus. And the second group distributes over only the fundus and is independent to circular muscle of esophagus.The oblique muscle of gastric corpus runs down on anterior and posterior gastric walls and pararell to the lesser curvature, forming a cleft between anterior and posterior bundle, to the end of the gastric corpus.The cleft seems to be corresponded to so-called “Magen-strasse”.2. Border between corpus and antrum: The first group, the muscle bundle which runs most closely to the lesser curvature and down to the most distance become mixed into the circular muscle bundle there. Therefore, the author named this most inner oblique muscle “the longest oblique muscle.” In the pyrolic side from the circular muscle bundle, no oblique muscle can be seen. So, the author divided corpus and antrum by this circular muscle bundle, and named this circular muscle bundle “the border circular muscle bundle”.3. Circular muscle: The circular muscle was divided into two groups. The one was mixed with oblique muscle bundle on the part near greater curvature and distributes over gastric corpus. The other distributes over the antrum without mixture of oblique muscle. Circular muscle was absent over fundus.

Caloric stimulation in localization of brain-stem lesions in a comatose patient.

CALORIC stimulation, employing cold water, in the comatose patient results in conjugate tonic deviation of the eyes toward the side stimulated, provided that the vestibulo-ocular brain-stem pathways are intact. 1 The absence of cerebral influence had been held responsible for both the loss of nystagmus and the antagonism to the vestibular impulses. Hence, tonic deviation occurs. If, in addition, the vestibulo-ocular pathway is interrupted in the posterior longitudinal bundle, a fairly definite sequence of events should follow caloric stimulation. The following case report illustrates this predictable sequence. REPORT OF A CASE Clinical Abstract.— T. L., a white man aged 47, was admitted to the neurological service of Mount Sinai Hospital on March 31, 1951, because of sudden onset of stupor. He had complained of bifrontal headache and nausea for 24 hours prior to admission. Several hours before admission he suddenly lapsed into stupor. He had not been hypertensive or diabetic.