Myocardial atrio-venous junctions and extensions (sleeves) over the pulmonary and caval veins Anatomical observations in various mammals
TL;DR: Differences between mammal and human hearts were found regarding the number of pulmonary trunks, the presence of the oblique vein of the left atrium, and the extension of the myocardial sleeves on the caval vein.
Abstract: The myocardial fibres of the posterior wall of the atrio-venous junctions were examined in 35 large domestic mammals. In the majority of specimens a common pattern in the course and organization of the fibres could be observed. The most obvious features were the following: (1) a main circular fascicle surrounding the pulmonary trunks; (2) fibres encircling the atriovenous junctions; and (3) myocardial sleeves extending along the veins, occasionally as far as the lung. The superior part of the left atrial wall was consistently thicker than the inferior section. Individual variations of this wall between the various trunks followed one of four patterns—vertical, oblique, horizontal or criss-crossed. Differences between mammal and human hearts were found regarding the number of pulmonary trunks, the presence of the oblique vein of the left atrium, and the extension of the myocardial sleeves on the caval vein. This extension on the caval vein continues over the end of the azygos vein in animals. The functional significance of the structures described in this study is discussed.
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TL;DR: Ectopic beats initiating PAF can originate from the SVC, and a radiofrequency current delivered to eliminate these ectopies is a highly effective and safe way to prevent PAF.
Abstract: Background—The superior vena cava (SVC) has cardiac musculature extending from the right atrium. However, no previous study in humans has given details regarding the ectopic foci that initiate paroxysmal atrial fibrillation (PAF), which may originate from the SVC. Methods and Results—A total of 130 patients with frequent attacks of PAF initiated by ectopic beats were included. Eight patients (6%) had spontaneous AF initiated by a burst of rapid ectopic beats from the SVC (located 19±7 mm above the junction of the SVC and right atrium), which was confirmed by multiplane angiographic and intracardiac echocardiographic visualization and was marked by a sharp SVC potential preceding atrial activity. During initial repetitive discharges, the group with SVC ectopy had a higher incidence of intravenous conduction block than the group with pulmonary vein ectopy (75% versus 37%; P=0.03). The activation time of the earliest intracardiac ectopic activities relative to ectopic P wave onset was significantly shorter i...
522 citations
TL;DR: During stable AF, the PLA harbors regular, fast, and highly organized activity; the outer limit of the DFmax domain is the area where the most propagation pattern variability and fractionated activity occur.
Abstract: Background— High-frequency fractionated electrograms recorded during atrial fibrillation (AF) in the posterior left atrium (PLA) and elsewhere are being used as target sites for catheter ablation. We tested the hypothesis that highly periodic electric waves emerging from AF sources at or near the PLA give rise to the most fractionated activity in adjacent locations. Methods and Results— Sustained AF was induced in 8 isolated sheep hearts (0.5 μmol/L acetylcholine). Endocardial videoimaging (DI-4-ANEPPS) and electric mapping of the PLA enabled spatial characterization of dominant frequencies (DFs) and a regularity index (ratio of DF to total power). Regularity index showed that fractionation was lowest within the area with the maximal DF (DFmax domain; 0.19±0.02) and highest within a band of &3 mm (0.16±0.02; P=0.047) at boundaries with lower-frequency domains. The numbers of spatiotemporal periodic episodes (25.9±2.3) and rotors per experiment (1.9±0.7) were also highest within the DFmax domain. Most comm...
430 citations
TL;DR: The myocardial architecture in normal pulmonary veins is highly variable and the complex arrangement, stretch, and increase in fibrosis may produce greater non-uniform anisotropic properties.
Abstract: BACKGROUND—Radiofrequency ablation of tissues in pulmonary veins can eliminate paroxysmal atrial fibrillation.
OBJECTIVE—To explore the characteristics of normal pulmonary veins so as to provide more information relevant to radiofrequency ablation.
METHODS—20 structurally normal heart specimens were examined grossly. Histological sections were made from 65 pulmonary veins.
RESULTS—The longest myocardial sleeves were found in the superior veins. The sleeves were thickest at the venoatrial junction in the left superior pulmonary veins. For the superior veins, the sleeves were thickest along the inferior walls and thinnest superiorly. The sleeves were composed mainly of circularly or spirally oriented bundles of myocytes with additional bundles that were longitudinally or obliquely oriented, sometimes forming mesh-like arrangements. Fibrotic changes estimated at between 5% and 70% across three transverse sections were seen in 17 veins that were from individuals aged 30 to 72 years.
CONCLUSIONS—The myocardial architecture in normal pulmonary veins is highly variable. The complex arrangement, stretch, and increase in fibrosis may produce greater non-uniform anisotropic properties.
Keywords: arrhythmias; catheter ablation; fibrillation; cardiac veins
420 citations
TL;DR: A dynamic pattern of changes in the myosin phenotype in the prenatal mouse heart suggests that there are different regulatory mechanisms for cell-specific expression of myos in isoforms during cardiac development.
Abstract: Expression of the two isoforms of cardiac myosin heavy chain (MHC), MHC alpha and MHC beta, in mammals is regulated postnatally by a variety of stimuli, including serum hormone levels. Less is known about the factors that regulate myosin gene expression in rapidly growing cardiac muscle in embryos. Using isoform-specific 35S-labeled cRNA probes corresponding to the two MHC genes and the two myosin alkali light chain (MLC) genes expressed in cardiac muscle, we have investigated the temporal and spatial pattern of expression of these different genes in the developing mouse heart by in situ hybridization. Between 7.5 and 8 d post coitum (p.c.), the newly formed cardiac tube begins to express MHC alpha, MHC beta, MLC1 atrial (MLC1A), and MLC1 ventricular (MLC1V) gene transcripts at high levels throughout the myocardium. As a distinct ventricular chamber forms between 8 and 9 d p.c., MHC beta mRNAs begin to be restricted to ventricular myocytes. This process is complete by 10.5 d p.c. During this time, MHC alpha mRNA levels decrease in ventricular muscle cells but continue to be expressed at high levels in atrial muscle cells. MHC alpha transcripts continue to decrease in ventricular myocytes until 16 d p.c., when they are detectable at low levels, but then increase, and finally replace MHC beta mRNAs in ventricular muscle by 7 d after birth. Like MHC beta, MLC1V transcripts become restricted to ventricular myocytes, but at a slower rate. MLC1V mRNAs continue to be detected at low levels in atrial cells until 15.5 d p.c. MLC1A mRNA levels gradually decrease but are still detectable in ventricular cells until a few days after birth. This dynamic pattern of changes in the myosin phenotype in the prenatal mouse heart suggests that there are different regulatory mechanisms for cell-specific expression of myosin isoforms during cardiac development.
395 citations
TL;DR: PVI alone is insufficient in the treatment of persistent AF, however, additional left linear lesions increase the success rate significantly.
Abstract: Aims To investigate the effectiveness of additional substrate modification (SM) by left atrial (LA) linear lesions as compared with pulmonary vein isolation (PVI) alone in patients with persistent atrial fibrilla- tion (AF) in a prospective randomized study. Percutaneous PVI has evolved as an accepted treatment for paroxysmal AF but seemed to be less effective in patients with persistent AF. The benefit of PVI alone and additional linear lesions has not been validated in a randomized study so far. Methods and results Sixty-two patients with persistent AF (median duration 7, range 1-18 months) were randomly assigned to either PVI alone (n ¼ 30) or additional SM (n ¼ 32) consisting of a roof line connecting both left superior and right superior PV and LA isthmus ablation between left inferior PV and mitral annulus. Procedures including SM were performed using a three-dimensional mapping system (EnSite NavX TM , St Jude Medical, St Paul, MN, USA). Anti-arrhythmic drugs were discontinued within 8 weeks after ablation in both groups. Follow-up included daily trans-telephonic ECG transmitted irrespective of the patient's symptoms. PVI was successful in 98% of all targeted veins in both groups. Additional SM did not increase fluoroscopy time (72.1+ 18.7 vs. 72.9+ 17.3 min, P ¼ 0.92) because of the use of three-dimensional navigation in the PVI þ SM group. AF recurrences within the first 4 weeks following ablation were more common after PVI alone (77%) than additional SM (44%, P ¼ 0.002). After a follow-up time of 487 (429-570) days, only 20% of patients undergoing stand alone PVI remained in sinus rhythm when compared with 69% following PVI combined with SM (P ¼ 0.0001). Two patients assigned to PVI þ SM experienced procedure-related complications (cardiac tamponade and minor stroke) which resolved without sequelae. Conclusion PVI alone is insufficient in the treatment of persistent AF. However, additional left linear lesions increase the success rate significantly. Early AF-relapses are associated with a negative outcome after PVI alone but not following additional SM.
312 citations
References
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Book•
01 Jan 1914
TL;DR: The anatomy of the domestic animals as discussed by the authors, the anatomy of domestic animals, The anatomy of animals, and the anatomical structure of the human body are discussed in detail in the work of as discussed by the authors.
Abstract: The anatomy of the domestic animals , The anatomy of the domestic animals , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
1,036 citations
"Myocardial atrio-venous junctions a..." refers background in this paper
...Although these sleeves are commonly neglected in anatomical textbooks and medical literature (Bourdelle, 1920; Bruni and Zimmerl, 1951 ; Sisson, 1953 ; Miller, Christensen, and Evans, 1964; May, 1964), they may perhaps be of functional importance....
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Book•
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01 Jun 1964
727 citations
"Myocardial atrio-venous junctions a..." refers background in this paper
...The fact that the oblique vein was frequently present in animals (Miller et al., 1964) and infrequently present in man, is another difference to be noted....
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TL;DR: Some anatomic features of the posterior wall of the left atrium, the atrial-pulmonary venous junctions, and the myocardial sleeves extending over the pulmonary veins, as observed in 16 human hearts are described.
Abstract: Some anatomic features of the posterior wall of the left atrium, the atrial-pulmonary venous junctions, and the myocardial sleeves extending over the pulmonary veins, as observed in 16 human hearts, are described. Different patterns of direction of the myocardial fibers of the atrial wall were found in the different specimens. The atrial wall between the upper pulmonary veins was consistently thicker than that between the lower ones. Similarly, the sphincter-like structures of the atrial-pulmonary venous junctions were generally more conspicuous, and the myocardial venous sleeves better developed in the superior than in the inferior pulmonary veins. The physiological and pathological implications of these findings are discussed.
448 citations
TL;DR: The examination of serial sections of human embryos between 24 and 34 days and the use of plastic reconstructions showed that the common pulmonary vein develops as an outgrowth from the medial superior wall of the left auricle and unites with the angioblastic plexus of the developing lung bud.
Abstract: The examination of serial sections of human embryos between 24 and 34 days (3 to 11 mm) and the use of plastic reconstructions, showed that the common pulmonary vein develops as an outgrowth from the medial superior wall of the left auricle and unites with the angioblastic plexus of the developing lung bud. No evidence was found that the vein connects directly with the sinus venosus in the early stages, and later shifts in position as the atrial septum grows. Anomalous pulmonary venous drainage is classified in four main types, and theories of development are briefly discussed.
184 citations
117 citations