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At least 271 records · Page 15Linked to original sources
PubMed1977

Effects of contrast media on the conducting system of the heart. Mechanism of action and identification of toxic component.

Infusion of progressive volumes of meglumine sodium diatrizoate (Renografin 76) into the arteries to the sinoatrial and atrioventricular nodes in anesthetized dogs produced a dose rate-dependent decrease in heart rate and an increase in "PR interval." At high dose rates, Renografin 76 caused sinus arrest and complete heart block in 50% and 70% of the animals, respectively. Saline and meglumine solutions (0.939 M) equiosmolar with Renografin 76 produced similar effects. Infusions of metrizamide (equal in iodine content with Renografin 76), dextrose solution (0.939 M), and autologous blood each had substantially less effects. Contrast media have a direct inhibitory action on sinoatrial automaticity and atrioventricular conductivity which is dependent on ionic strength, not iodine content.

Animals↗
PubMed1988

Immunohistochemical identification of Purkinje fibers and transitional cells in a terminal portion of the impulse-conducting system of porcine heart.

The ultrastructure of porcine ventricular tissue was studied by electron microscopy and immunocytochemical techniques. Electron-dense specific granules were found in both Purkinje fibers and transitional cells in the ventricular walls, and were positively stained by the immunogold staining method using an antiserum against atrial natriuretic polypeptide (ANP). This suggests that both the Purkinje fibers and transitional cells display the same specific granules as atrial cardiocytes containing ANP. These results demonstrate that Purkinje fibers and two types of transitional cells, in addition to the ordinary ventricular cardiocytes, can be identified in porcine ventricular wall tissue.

Animals↗
PubMed1987

Pathology of the heart and conduction system in lymphoma and leukaemia.

The clinical and pathological findings in two patients with non-Hodgkin's lymphoma and two patients with T helper cell prolymphocytic leukaemia affecting the heart are described. All four patients had extensive malignant disease, with infiltration of multiple organs. Cardiac infiltration varied from microscopic foci in one case, to grossly identifiable tumour deposits destroying and replacing normal heart structures in three cases. Two patients with infiltration of the conduction system had abnormal electrocardiograms and cardiac dysfunction: one died suddenly, and the other died in heart failure. A third patient with widespread cardiac lymphoma did not show any electrocardiographic abnormalities or dysfunction. Clinicians should be aware of the possibility of cardiac and conduction system disease, particularly in the light of the evolution of specific antitumour chemotherapeutic agents.

Aged↗
PubMed1986

The structure of the atrioventricular conducting system in the avian heart.

The atrioventricular conduction system in three avian species has been studied by light and electron microscopy. A morphologically definable atrioventricular node was not found in any of these. The atrioventricular bundle is a well-defined structure, the proximal portion of which is in direct continuity with the atrioventricular ring, located in the arterial sheet of the muscular valve of the right atrioventricular opening. In the zone of transition between atrioventricular ring and bundle the compactness of the bundle is loosened, but the fibers do not establish continuity with the atrial fibers. The ring consists of Purkinje-like fibers, 10-15 microns in diameter, and (peripherally) small 3-5-microns-diameter junctional fibers which are in continuity with the common atrial fibers. In the muscular atrioventricular valve the fibers of the ring are insulated from the ventricular myocardium by a connective tissue sheet of the annulus fibrosus. It is suggested that in the avian heart the atrioventricular ring may fulfill a role similar to that of the atrioventricular node of mammals.

Animals↗
PubMed1979

Ischemic injury to the conducting system of the heart. Involvement of myocardial lysosomes.

The conducting system was studied in an in situ perfused swine heart preparation with reduced coronary flow (ischemia) using perfusate containing high and low levels of glucose (26.6 versus 8.6mM) with and without insulin. Coronary flow was maintained at normal levels for 60 minutes in control hearts. In ischemic hearts flow was reduced to about 50 percent of control levels for 30 minutes. Ultrastructural studies documented only subtle modifications of Purkinje fibers in ischemic hearts. Glycogen depletion and disruption of cell junctions were observed in some fibers. One consistent finding was the activation of the lysosomal system. The outer membranes of primary lysosomes appeared herniated and in some cases disrupted, and small vesicles containing hydrolytic enzymes were seen in association with the Golgi apparatus and larger primary lysosomes. Specimens prepared for the demonstration of acid phosphatase indicated a redistribution of hydrolytic enzymes in Purkinje fibers with a depostion of acid hydrolases in smaller lysosomal vesicles, the transverse and side-to-side junctions between cells, and occasionally in the sarcoplasmic reticulum. Enriched perfusate containing high levels of glucose with insulin appeared to have no therapeutic effects in terms of the structure of the Purkinje fibers. The results suggest that alterations in the lysosomal system may be one of the earliest structural changes which occur in oxygen-deficient hearts.

Acid Phosphatase↗
PubMed1995

Gap junction protein phenotypes of the human heart and conduction system.

INTRODUCTION: Gap junction channels are major determinants of intercellular resistance to current flow between cardiac myocytes. Alterations in gap junctions may contribute to development of arrhythmia substrates in patients. However, there is significant interspecies variation in the types and amounts of gap junction subunit proteins (connexins) expressed in disparate regions of mammalian hearts. To elucidate determinants of conduction properties in the human heart, we characterized connexin phenotypes of specific human cardiac tissues with different conduction properties. METHODS AND RESULTS: The distribution and relative abundance of Cx37, Cx40, Cx43, Cx45, and Cx46 were studied immunohistochemically using monospecific antibodies and frozen sections of the sinoatrial node and adjacent atria. AV node and His bundle, the bundle branches, and the left and right ventricular walls. Patterns of expression of these connexins in the human heart differed from those in previous animal studies. Sinus node gap junctions were small and sparse and contained Cx45 and apparently smaller amounts of Cx40 but no Cx43. AV node gap junctions were also small and contained mainly Cx45 and Cx40 but, unlike the sinus node, also expressed Cx43. Atrial gap junctions were larger than nodal junctions and contained moderate amounts of Cx40, Cx43, and Cx45. Junctions in the bundle branches were the largest in size and contained abundant amounts of Cx40, Cx43, and Cx45. Gap junctions in ventricular myocardium contained mainly Cx43 and Cx45; only a very small and amount of ventricular Cx40 was detected in subendocardial myocyte junctions and endothelial cells of small to medium sized intramural coronary arteries. Minimal Cx37 and Cx46 immunoreactivity was detected between occasional atrial or ventricular myocytes. CONCLUSIONS: The relative amounts of individual connexins and the number and size of gap junctions vary greatly in specific regions of the human heart with different conduction properties. These differences likely play a role in regulating cardiac conduction velocity. Differences in the connexin phenotypes of specific regions of the human heart and experimental animal hearts must be considered in future experimental or modeling studies of cardiac conduction.

Adult↗
PubMed1988

Effects of contrast media on the conducting system of the heart during coronary angiography. A comparison of Renografin-76 to Hypaque-76.

Electrocardiographic changes induced by ionic contrast media can cause complications during coronary angiography. A conduction delay through various parts of the heart is one factor in the genesis of asystole or ventricular fibrillation. Hypaque-76 (H76) and Renografin-76 (R76) are nearly identical ionic contrast media except that R76 binds more calcium than H76 because of the presence of sodium citrate and EDTA in R76. To determine whether the calcium binding additives in ionic contrast media contribute to the cardiac conduction abnormalities, we examined conduction time through the atrioventricular (AV) nodal tissue (via bipolar His bundle electrograms) and through the distal part of the conduction system (recording the QRS complex from the ECG) during coronary angiography. We injected 10 mL of H76 and R76 in 19 closed chest dogs in a blinded, randomized fashion during coronary angiography. The effects of H76 and R76 on heart rate, AH interval, HV interval, V interval and PR interval, and QRS complex duration were recorded. In 14 nonatrial pacing dogs, compared with H76, R76 produced a greater increase in the AV interval (32.9 +/- 6 milliseconds vs 12.4 +/- 2 milliseconds, P less than .01) and the PR interval (29.6 +/- 6 milliseconds vs 11.9 +/- 4 milliseconds, P less than .02). Additionally, the heart rate decreased 13.9 +/- 3.5 beats/minute from control with R76 compared with a decrease of 4.2 +/- 2.6 beats/minute from control with H76 (P less than .05). There was no significant difference between the prolongation of the HV interval and V interval, or QRS complex duration generated by R76 and H76.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗