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Biomedical subjects

T N James

Publications and source records attributed to T N James.

At least 163 records · Page 9Linked to original sources
PubMed1977

The sinus node.

This discussion of the sinus node begins with a description of its normal anatomy, particularly in the human heart, and then proceeds to a review of the several pathologic changes known to affect the sinus node. The latter include diseases of the sinus node artery, changes in the normal collagen framework of the node, pericarditis and certain infiltrative processes. The concluding section combines an examination of function and structure of the sinus node on the basis of experimental observations. Some new laws of the heart dealing with governance of normal cardiac rhythm are presented.

Action Potentials↗
PubMed1977

Distribution of 9 trace metals in 17 anatomic sites of dog heart tissue and their classification using pattern recognition.

The concentrations (geometric means of 11 determinations) of 9 trace metals in 17 anatomic regions of dog heart tissue and blood vessels were determined. The relationships recognized within the set of trace metal profiles were comparable to those reported earlier for the cardiovascular systems of pig [J. Mol. Cell Cardiol 6, 383 (1974)] and those of beef [Bioinorg, Chem. (in press)]. These included differences in trace metal concentrations that allowed differentiation of the following tissues from each other: (1) ordinary and specialized myocardium from blood vessels and heart valves, (2) blood vessels from heart valves and (3) arterial from venous tissues.

Animals↗
PubMed1977

Sequence of retrograde atrial activation of the human heart. Correlation with P wave polarity.

Studies were performed in 6 patients during open heart surgery to correlate the relative sequence of atrial activation with the polarity of the retrograde P wave in electrocardiographic leads II, III, and aVF. Bipolar atrial electrograms were recorded from selected sites during threshold pacing from sites low on the right side of the atrial septum which when paced resulted in the inscription of either negative or positive P waves in electrocardiograph leads II, III, and aVF. When the atria were paced from a site just anterior to the coronary sinus ostium (negative P waves), the posteroinferior left atrium was activated early and Bachmann's bundle late during the inscription of the P wave. When the atria were paced from a site 2 cm anterior to the coronary sinus ostial site (positive P waves), Bachmann's bundle was activated early during the P wave and the posteroinferior left atrium was activated relatively later. These data from man are consistent with previous studies in the canine heart. Therefore, we deduced that in man during the inscription of negative retrograde P waves in leads II, III, and aVF, atrial activation occurs primarily in a retrograde fashion. However, during the inscription of positive retrograde P waves in man, activation occurs rapidly up the interatrial septum (we believe via the anterior internodal pathway) to Bachmann's bundle, from where it then spreads in a manner similar to that which occurs during normal sinus rhythm.

Adolescent↗
PubMed1977

Differential sensitivity to neurotransmitters in denervated canine sinus node.

This investigation determined the chronotropic effects of norepinephrine and acetylcholine (ACh) administered selectively into the canine sinus node artery after cardiac denervation. In 42 dogs the cervical vagi were isolated, the heart was exposed, and vagal stimulations were performed before and after sham procedure or extrinsic cardiac parasympathectomy. Four additional dogs underwent bilateral stellectomy. The dogs were reanesthetized 4-23 days later, and blood pressure, heart rate, ECG, and local cardiac electrograms were recorded. The vagi were again stimulated and the effectiveness of the parasympathectomy was verified in 11 of the dogs. On selective perfusion of the sinus node with 0.001- to 1-microgram doses of ACh, the sinus bradycardias of the parasympathectomized and the sham-operated dogs were not significantly different. The responses to norepinephrine (0.01 and 0.1 microgram/ml) administered via the same route in the stellectomized dogs were significantly greater than those in the sham-operated dogs, thus verifying this technique for the assessment of sinus node sensitivity to neurotrasmitters. We conclude that extrinsic denervation of the canine sinus node leads to development of a differential response between adrenergic and cholinergic neurotransmitters. These differential sensitivities may be important when considering the pharmacological responses and electrical stability of the denervated and/or transplanted heart.

Acetylcholine↗
PubMed1977

XXII. Intractable paroxysmal tachycardias which proved fatal in type A Wolff-Parkinson-White syndrome.

Paroxysmal tachycardias proved fatal in a middle-aged man with type A Wolff-Parkinson-White syndrome. Efforts to control his arrhythmias included a surgical incision into the left atrium, based on discovery of early left ventricular activation during epicardial mapping. The incision did not alter any electrocardiographic or clinical feature; at later necropsy examination it was found that the incision had not cut a nearby left atrioventricular (A-V) connection. Serial section study of the entire A-V rings and septal junction of this heart also demonstrated a second unusual A-V connection, between the atrial septum and the region of the His bundle. This latter connection was anatomically eccentric to the normal organization of this region and may have caused an alteration in the local electrophysiological behavior. The left lateral A-V connection may have been of no electrophysiological significance since it was composed of ordinary working myocardial cells. These and other possible correlations are discussed in the context of the clinical features, numerous electrophysiological observations, and the meticulously determined anatomical findings.

Atrioventricular Node↗
PubMed1977

De subitaneis mortibus. XXIII. Rheumatoid arthritis and ankylosing spondylitis.

The conduction system of the heart was carefully examined at necropsy in two cases of rheumatoid arthritis and one of ankylosing spondylitis. All three patients had cardiac electrical instability and two fo the three died suddenly. The electrophysiological abnormalities of the three patients included paroxysmal atrial fibrillation in the first case, sustained atrial fibrillation with complete heart block and escape atrioventricular (A-V) junctional rhythm in the second case, and progressively increasing heart block eventually became complete in the third case. The sinus node exhibited extensive focal degeneration with and without associated inflammation in all three hearts, but the sinus node artery was not remarkably abnormal in any of these. All three hearts had important focal degenerative disease in the A-V node and His bundle, and in each of these there was marked narrowing of the local nutrient arteries, amounting to virtual occlusion in two hearts. The probable relationship of these postmortem histological findings to the electrocardiographic disturbances in each patient is discussed. Abnormalities in the cardiac conduction system of the hearts of these three patients are compared to ones previously reported for disseminated lupus erythematosus, polyarteritis nodosa, and scleroderma heart disease.

Adult↗
PubMed1977

De subitaneis mortibus. XXIV. Ruptured interventricular septum and heart block.

Five patients with acute posterior myocardial infarction developed varying degrees of atrioventricular (A-V) block prior to rupture of their interventricular septums (IVS). In three of these five the times of septal rupture coincided with the resumption of conduced synus rhythm. During the period of A-V block, the only stable escape rhythm appeared to originate in the A-V junctional region, and in two patients early in their course there was evidence of enhanced A-V junctional automaticity. Although the A-V node contained extensive infarction in all five hearts, its distal part, and the entire His bundle and proximal branches appeared to be spared. The anatomical pattern of dissection within the ruptured IVS was similar in three hearts, extending upward to the crest of the IVS and penetrating into the interatrial septum in two of these. Multiple major coronary narrowing were present in all five hearts, especially of a dominating right coronary artery; recent thrombosis was present in the right coronary artery in four of the five cases. The A-V node artery was markedly narrowed by focal fibromuscular dysplasia in three hearts, compounding the ischemia for the A-V node and eliminating one important source of collateral circulation to the interventricular septum.

Aged↗
PubMed1977

Clinicopathologic correlations. De subitaneis mortibus. XXV. Sarcoid heart disease.

Postmortem findings within the cardiac conduction system are described from the case of a black woman with sarcoid heart disease who died suddenly. Her clinical course had been characterized by recurring ventricular arrhythmias and bouts of syncope. Both the sinus node artery and the atrioventricular (A-V) node artery were sites of focal fibromuscular dysplasia, which thickened slightly the wall of the former but markedly narrowed the lumen of the latter. Small foci of sarcoid infiltration were present in the sinus node and the A-V node. Fatty replacement within the His bundle was attributable to the probable ischemia caused by narrowing of the A-V node artery. Sarcoid granulomata and infiltration with epithelioid cells were present throughout the ventricular myocardium, but were conspicuously less prevalent in the atria. All the large coronary arteries were normal. Many small coronary arteries in the ventricular myocardium were involved by the sarcoidosis and their lumen were narrowed. These findings and analogous ones reported by others are discussed relative to the pathogenesis of syncopal attacks and sudden death which seem to peculiarly prevalent in sarcoid heart disease.

Adult↗
PubMed1977

De subitaneis mortibus. XXVI. Fatal electrical instabiltiy of the heart associated with benign congenital polycystic tumor of the atrioventricular node.

Benign congenital polycystic tumors of the atrioventricular (A-V) node are an unusual but not very rare cause of heart block. Two such cases are presented and discussed in conjunction with the reported experience of other. The tumor is always within and only very near the A-V node, seldom involves more than the proximal end of the His bundle, and has not been reported to occur in the sinus node. Although sudden death has been reported in conjunction with these tumors, a surprising number of other patients have lived to old age and died of causes unrelated to the A-V nodal tumor. As a corollary it is important to consider a diagnosis of A-V nodal tumor in any patient of any age who presents with otherwise unexplained heart block or syncope. From accumulated experience it appears that such patients do not tolerate electronic pacing safely and some possible explanations for this are discussed. Escape rhythm in all reported cases has been characterized by QRS complexes which are narrow and a ventricular rate which is from half to two-thirds of the sinus rate. Reasons why an A-V junctional rhythm which is 66% of sinus rate may be especially stable are discussed.

Aged↗
PubMed1977

Entrainment and interruption of atrial flutter with atrial pacing: studies in man following open heart surgery.

To examine the question of why the pacing rate and duration of atrial pacing are crucial factors in the successful interruption of atrial flutter, studies were performed on 30 patients in the period following open heart surgery. In each patient the diagnosis of atrial flutter was made using a pair of wire electrodes placed on the right atrial epicardium at the time of operation and brought out through the anterior chest wall. The same electrodes were used for atrial pacing. Pacing faster than the spontaneous rate of the atrial flutter which failed to interrupt the atrial flutter was associated with transient entrainment of the atrial flutter up to the atrial pacing rate. Atrial flutter was interrupted successfully when the atria were paced at a rate which was too fast for the atrial flutter to follow. This was heralded by the conversion of previously negative flutter waves to positive atrial complexes in ECG lead II. When pacing the atria at a constant rate, 2-22 seconds with a mean of 10 seconds were required to interrupt the atrial flutter.

Adult↗
PubMed1977

De subitaneis mortibus. XXVII. Histological abnormalities in the sinus node, atrioventricular node and His bundle associated with coarctation of the aorta.

A twenty-year-old carpenter died suddenly and unexpectedly nine years after surgical treatment of coarctation of the aorta. Both before and after surgery he had paroxysmal atrial fibrillation, T wave inversions in the ECG and persisting cardiac hypertrophy. At postmortem examination there was focal fibromuscular dysplasia narrowing the sinus node artery, but other small coronary arteries were normal and there was no focal fibrosis of the ventricular myocardium. Within the sinus node there were several small glomera surrounding branches of the sinus node artery. Pericardial fibrosis was present over much of the heart, including margins of the sinus node. The central fibrous body was thickened, particularly on the left, and the His bundle was smaller than normal in cross section. The His bundle appeared displaced toward the right. The artioventricular (A-V) node was split into an upper and lower half tenuously connected through the central fibrous body which divided it. In its lower half the A-V node was directly continuous with ordinary myocardial cells of the interventricular septum. Possible developmental relationships between these unusual anatomical findings in the conduction system and coarctation of the aorta are discussed. How these findings might relate to the known electrophysiological disturbances and some causes for his sudden death are considered.

Adult↗
PubMed1977

A multipurpose catheter for electrophysiologic and hemodynamic monitoring plus atrial pacing.

A new multipurpose flow-directed pulmonary arterial catheter has been developed and evaluated in 30 patients with acute cardiopulmonary dysfunction. The catheter permits monitoring of the bipolar atrial electrogram, pulmonary arterial or wedge pressure, central venous pressure, and cardiac output, plus atrial pacing. The standard Swan-Ganz thermistor-equipped catheter was modified to incorporate two ring electrodes on the shaft at 25 and 26 cm from the tip. With the pair of electrodes positioned in the right atrium at the junction with the superior vena cava, stable electrograms of high quality were recorded in all 30 subjects, some for as long as six days. These high-fidelity atrial electrograms permitted rapid and accurate diagnosis of many complex dysrhythmias in these unstable patients. Because of the limited noise in the signal of the electrogram, continuous quantitative measurements of intervals by a computerized system was feasible. Furthermore, the stable intracavitary position of electrodes provided a reliable site for atrial pacing, with pacing thresholds (2 to 12 ma; average, 5 ma) that remained stable for up to four days. Atrial pacing was used to treat sinus bradycardia, atrial tachyarrhythmias, digitalis intoxication, and ventricular dysrhythmias.

Arrhythmias, Cardiac↗