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Biomedical subjects

J A Cabrera

Publications and source records attributed to J A Cabrera.

At least 19 recordsLinked to original sources
PubMed2005

Sinus node revisited in the era of electroanatomical mapping and catheter ablation.

OBJECTIVE: To study the architecture of the human sinus node to facilitate understanding of mapping and ablative procedures in its vicinity. METHODS: The sinoatrial region was examined in 47 randomly selected adult human hearts by histological analysis and scanning electron microscopy. RESULTS: The sinus node, crescent-like in shape, and 13.5 (2.5) mm long, was not insulated by a sheath of fibrous tissue. Its margins were irregular, with multiple radiations interdigitating with ordinary atrial myocardium. The distances from the node to endocardium and epicardium were variable. In 72% of the hearts, the whole nodal body was subepicardial and in 13 specimens (28%) the inner aspect of the nodal body was subendocardial. The nodal body cranial to the sinus nodal artery was more subendocardial than the remaining nodal portion, which was separated from the endocardium by the terminal crest. In 50% of hearts, the most caudal boundaries of the body of the node were at least 3.5 mm from the endocardium. When the terminal crest was > 7 mm thick (13 hearts, 28%), the tail was subepicardial or intramyocardial and at least 3 mm from the endocardium. CONCLUSIONS: The length of the node, the absence of an insulating sheath, the presence of nodal radiations, and caudal fragments offer a potential for multiple breakthroughs of the nodal wavefront. The very extensive location of the nodal tissue, the cooling effect of the nodal artery, and the interposing thick terminal crest caudal to this artery have implications for nodal ablation or modification with endocardial catheter techniques.

Adult↗
PubMed2003

[Anatomy of the atria for rhythmologists].

The anatomy of the atria is always in the mind of interventional rhythmologists. There is a mental superposition of the anatomical structures and the references obtained by different incidences of fluoroscopy and the endocavitary electrocardiogram. But understanding the anatomy also requires a certain knowledge of dissection to determine, for example, the orientation of bundles of muscle fibres and anatomical sections. The sino-atrial node is situated at a distance from the endocardium. It is long and protected by its own artery which makes it difficult to reach. The atrio-ventricular node has multiple posterior expansions which correspond to the sites where radiofrequency ablation is effective. The cavo-tricuspid isthmus is the target zone for the treatment of atrial flutter but radiofrequency ablation which must be long may be applied at three different levels: inferolateral, median (the most common site) or inferoseptal. Finally, atrial fibrillation has incited many studies of the muscular extensions of the left atrium to the pulmonary veins, the morphological variations of these veins and the organisation of the muscle fibres of the left atrial wall. They have inspired new concepts of atrial fibrillation.

Arrhythmias, Cardiac↗
PubMed2002

The terminal crest: morphological features relevant to electrophysiology.

OBJECTIVE: To investigate the detailed anatomy of the terminal crest (crista terminalis) and its junctional regions with the pectinate muscles and intercaval area to provide the yardstick for structural normality. DESIGN: 97 human necropsy hearts were studied from patients who were not known to have medical histories of atrial arrhythmias. The dimensions of the terminal crest were measured in width and thickness from epicardium to endocardium, at the four points known to be chosen as sites of ablation. RESULTS: The pectinate muscles originating from the crest and extending along the wall of the appendage towards the vestibule of the tricuspid valve had a non-uniform trabecular pattern in 80% of hearts. Fine structure of the terminal crest studied using light and scanning electron microscopy consisted of much thicker and more numerous fibrous sheaths of endomysium with increasing age of the patient. 36 specimens of 45 (80%) specimens studied by electron microscopy had a predominantly uniform longitudinal arrangement of myocardial fibres within the terminal crest. In contrast, in all specimens, the junctional areas of the terminal crest with the pectinate muscles and with the intercaval area had crossing and non-uniform architecture of myofibres. CONCLUSIONS: The normal anatomy of the muscle fibres and connective tissue in the junctional area of the terminal crest/pectinate muscles and terminal crest/intercaval bundle favours non-uniform anisotropic properties.

Adolescent↗
PubMed2001

Topographic anatomy of the inferior pyramidal space: relevance to radiofrequency catheter ablation.

INTRODUCTION: Radiofrequency catheter ablation carried out in the vicinity of the triangle of Koch risks damaging not only the AV conduction tissues but also their arterial supply. The aim of this study was to examine the relationship of the AV nodal artery to the inferior pyramidal space, the triangle of Koch, and the right atrial endocardial surface. METHODS AND RESULTS: We studied 41 heart specimens, 24 by gross dissections and 17 by histologic sections. The proximity of the AV nodal artery to the surface landmarks of the triangle of Koch was variable, but it was notable that in 75% of specimens the artery passed close to the endocardial surface of the right atrium and within 0.5 to 5 mm of the mouth of the coronary sinus. In all specimens, the mean distance of the artery to the endocardial surface was 3.5 +/- 1.5 mm at the base of Koch's triangle. The location of the compact AV node and its inferior extensions varied within the landmarks of the triangle. At the mid-level of Koch's triangle, the compact node was medially situated in 82% of specimens, but it was closer to the hinge of the tricuspid valve in the remaining 18% of specimens. In 12% of specimens, the inferior parts of the node extended to the level of the mouth of the coronary sinus. CONCLUSION: The nodal artery runs close to the orifice of the coronary sinus, the endocardial surface of the right atrium, the middle cardiac vein, and the specialized conduction tissues in most hearts. The nodal artery and/or the AV conduction tissues can be at risk of damage when ablative procedures are carried out at the base of the triangle of Koch.

Adolescent↗
PubMed2001

Architecture of the pulmonary veins: relevance to radiofrequency ablation.

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.

Adult↗
PubMed2000

Therapeutic decision tree for patients with sustained ventricular tachyarrhythmias or aborted cardiac arrest: a critical review of the Antiarrhythmics Versus Implantable Defibrillator trial and the Canadian Implantable Defibrillator Study.

Antiarrhythmic drugs, mainly amiodarone and sotalol, radiofrequency catheter ablation, and the implantable cardioverter defibrillator (ICD) are the 3 therapeutic options in patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Idiopathic VT, incessant VT, frequently recurring, hemodynamically stable VT, and VT based on bundle branch reentry, are candidates for radiofrequency catheter ablation. Patients with high-risk ventricular tachyarrhythmias should receive ICDs as initial therapy. Two studies, the Antiarrhythmics Versus Implantable Defibrillator trial (AVID) and the Canadian Implantable Defibrillator Study (CIDS) have tried to approach the problem of these high-risk ventricular tachyarrhythmias. Although at 3 years, the ICD in AVID demonstrated a significant relative risk reduction over amiodarone of 31.5%, CIDS could not duplicate this finding. At 3 years, the relative risk reduction conferred by the ICD over amiodarone in CIDS was only 13.7%. A careful analysis of both studies suggests that CIDS was insufficiently powered to demonstrate statistically significant benefits similar to those shown by AVID, and furthermore, seemed to include an undetermined number of low-risk VT patients. The problem in the CIDS trial in this regard was the recruitment of patients in whom the inclusion criteria were met by the arrhythmias induced during the electrophysiology stimulation study, but which did not exist in real life. In addition CIDS included 14% of patients with (1) undocumented syncope and inducible monomorphic sustained VT; or (2) long runs of spontaneous nonsustained VT. Under these circumstances, the therapeutic implications of AVID remain unchallenged.

Anti-Arrhythmia Agents↗
PubMed1999

Angiographic anatomy of the inferior right atrial isthmus in patients with and without history of common atrial flutter.

BACKGROUND: Although most ablative procedures undertaken for common atrial flutter target the inferior right atrial isthmus, comparative studies of the morphology of this area are lacking. Our study examines its angiographic anatomy, making correlations with postmortem specimens, to provide a better understanding of the anatomic substrate of this arrhythmia. METHODS AND RESULTS: The gross morphological features and dimensions of the area between the orifice of the inferior caval vein and the attachment of the septal leaflet of the tricuspid valve were determined from angiograms made in 23 patients with documented atrial flutter and 30 control subjects. For comparison, we studied 20 normal heart specimens. When viewed in right anterior oblique projection, 2 morphologically distinct areas were identified. In the specimens, the inferior isthmus measured a mean length of 30+/-4 mm, not significantly different from the dimensions obtained from angiograms of control subjects. The mean length of the isthmus, however, was greater in patients with common atrial flutter than those without (37+/-8 versus 28+/-6 mm). Patients with atrial flutter and structural heart disease had an even longer isthmus than those with flutter alone (39. 6+/-8 versus 33+/-7 mm). Compared with those without flutter, the atrial diameter was also larger in patients with flutter (57.6+/-9 versus 48.5+/-6 mm). Reevaluation carried out at follow-up 10+/-2 months after ablation did not show any reduction in atrial size, although contractility improved. CONCLUSIONS: The inferior isthmus and right atrium in patients with common atrial flutter were significantly larger than those in a control population.

Adult↗
PubMed1999

Anatomy of the left atrium: implications for radiofrequency ablation of atrial fibrillation.

INTRODUCTION: The feasibility of treating atrial fibrillation with radiofrequency ablation has revived interest in the structure of the left atrium, a chamber that has been neglected in many textbooks of anatomy. METHODS AND RESULTS: We reviewed the gross structure of the left atrium by examining the septum, the appendage, and insertions of the pulmonary veins in normal hearts. The limited extent of the true septal component is relevant to procedures using the transseptal approach. On gross examination, the musculature of the atrial wall is composed of overlapping bundles of aligned fibers that, in the majority of hearts, are arranged in characteristic patterns with only minor individual variations. Muscular sleeves extend into the walls of the pulmonary veins to varying distances. The longest sleeves are in the left upper veins. Bachmann's bundle anteriorly, and other smaller bundles superiorly and posteriorly, bridge the septal raphe to blend with musculature of the right atrium. Tongues of left atrial musculature from the posterior wall also extend into the wall of the coronary sinus. CONCLUSION: The left atrium is more complex than usually conceived. Understanding its structure, and the arrangement of its musculature, will help in improving strategies for linear lesions when attempting to compartmentalize the chamber, or when placing focal lesions for ablating ectopic sources.

Adult↗
PubMed1998

The architecture of the atrial musculature between the orifice of the inferior caval vein and the tricuspid valve: the anatomy of the isthmus.

INTRODUCTION: Electrophysiologists recognize a so-called "isthmus" in the right atrium through which passes the reentrant circuit of common atrial flutter. Ablative lesions placed in this narrow channel have proved effective in breaking the circuit. To the best of our knowledge, however, no study has been performed to establish the arrangement and orientation of the atrial myocardial fibers in this crucial area. METHODS AND RESULTS: We examined 28 normal heart specimens, identifying a quadrilateral area composed of three morphologic sectors between the inferior caval vein and the tricuspid valve confluent superiorly with the triangle of Koch. Within this quadrilateral, there are constant recesses, or sinuses, inferior and lateral to the orifice of the coronary sinus. The inferior isthmus measured an average of 31+/-4 mm (range 19 to 40). Gross examination identified marked differences in the atrial wall forming the quadrilateral. A smooth anterior component forming the vestibule of the tricuspid valve was found in all the hearts, but variations in the remaining sectors were seen in ten specimens. The usually membranous posterior sector was noticeably muscular in three specimens, while the middle, trabecular sector was more membranous in five specimens. We demonstrated the orientation of the subendocardial atrial fibers by dissection in 14 specimens, revealing a relatively constant overall pattern in eight specimens and variations in fiber orientation in the remaining specimens. CONCLUSION: There are considerable anatomic variations in the atrial wall that comprises the so-called isthmus. The presence of recesses and membranous areas in some hearts and the variations in arrangement of the subendocardial fibers are relevant in improving understanding of conduction in this area.

Data Interpretation, Statistical↗
PubMed1997

Angiographic predictors of neointimal thickening after successful coronary wall healing following percutaneous revascularization.

This study was undertaken to characterize, by intracoronary ultrasound technique, the neointimal thickening at follow-up of treated coronary segments after successful arterial wall repair and to compare the findings with serial angiographic studies. We selected for study 81 patients with single-vessel coronary disease successfully treated by percutaneous revascularization who were angiographically and ultrasonically reevaluated at a mean follow-up time of 22 +/- 21 months; 23 had been treated by balloon angioplasty, 27 by directional atherectomy, and 31 by elective Palmaz-Schatz stent implantation. The late maximal neointimal thickness varied between 0.1 and 1.5 mm (mean 0.65 +/- 0.31 mm), and the neointimal area ranged between 0.97 and 14.9 mm2 (mean 5.19 +/- 3.14 mm2). The neointimal repair was thinner in patients who obtained a better acute angiographic result immediately after treatment and in stented (3.4 +/- 1.8 mm2) versus dilated (7.8 +/- 4.1 mm2) or resected (5 +/- 1.6 mm2, p < 0.001) segments. On the contrary, the repaired neointimal layer was thicker in those patients who angiographically exhibited less late luminal loss or even expansion and in those evaluated after a longer time since treatment. The acute gain and the time influence resulted in independent predictors of the degree of neointimal thickness. These findings suggest that two reparative mechanisms of the coronary wall may operate in close relation.

Angioplasty, Balloon, Coronary↗
PubMed1996

Targeted retroviral gene transfer into the rat biliary tract.

The ability to induce proliferation by temporary duct ligation suggested an hypothesis that retrovirus-mediated gene transfer into cells of the biliary tract could be accomplished. The time course of histologic changes, incorporation of 3H-thymidine and immunofluorescent staining with a monoclonal antibody to cytokeratin-19 (a marker for differentiated bile ducts) was studied in male Fischer F344 rats. A recombinant Gibbon ape leukemia virus (GALV), containing a gene encoding Escherichia coli beta-galactosidase was next introduced into 24 hr obstructed bile ducts. Gene transfer was maximal when virus was exposed to the obstructed duct for 12 hr (approximately 0.1%). The majority of X-gal positive cells were in cytokeratin-19 negative peribiliary tissues, which had the appearance of newly forming bile ducts. The data suggest that cells targeted by retroviral infection of the obstructed rat bile duct may be a precursor of mature, fully differentiated biliary epithelium.

Animals↗
PubMed1996

[Intellectual property rights in Costa Rica in the light of the Biodiversity Convention].

This report analyzes intellectual property rights and acquisition of biological samples in light of the Biological Diversity Convention, with emphasis on Costa Rica. It examines the legal framework which exists for the protection of biological resources in this country, especially evaluating the law regarding protection of biota, which was approved in 1992. This includes information regarding access to genetic resources, and regulation for the aforementioned law. It examines the Biological Diversity Convention which was signed at the Rio Summit in 1992, whose objectives and goals, above all, emphasize the subject of distribution of benefits to be derived from the utilization of biological resources.

Animals↗
PubMed1993

Factors determining late success after mitral balloon valvulotomy.

Mitral balloon valvulotomy (MBV) has proved to be an effective method in the treatment of patients with mitral stenosis. Although several factors determining an optimal immediate result have been described, there is little information regarding long-term follow-up, as well as factors influencing late success after MBV. This study analyzes 350 patients (mean age 46 +/- 12 years) treated by MBV who were clinically followed up between 6 months and 6 years. At least 1 echo-Doppler follow-up study was obtained in 298 patients 28 +/- 14 months after MBV; hemodynamic reevaluations were performed in 66 patients after 23 +/- months. Late success was considered if the patient was in functional class I to II and free of major events (death, restenosis and valve surgery). Restenosis was defined as a 50% loss of initial gain with regard to valve area by echocardiography, which was confirmed hemodynamically. After a mean follow-up of 38 +/- 15 months, 296 patients (84%) remained in functional class I to II, without surgery or the need for an increase in medical treatment. The 5-year Kaplan-Meier survival rate was 94 +/- 1%, whereas restenosis, valve surgery and major event-free probability were 90 +/- 3%, 91 +/- 2% and 85 +/- 2%, respectively. Multivariate study (Cox regression model) identified the presence of sinus rhythm (p < 0.001) and the absence of calcium at fluoroscopy (p < 0.003) as the only independent factors of late success.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

A novel mechanism for achieving transgene persistence in vivo after somatic gene transfer into hepatocytes.

Infusion of hepatocyte-specific DNA-protein complexes into rats leads to transient recombinant gene expression in liver. The eventual deterioration of gene expression is due in part to instability of the targeted DNA. In a previous report, we noted retention of transgene sequences in liver and persistent recombinant gene expression when the animals were subjected to partial hepatectomy following in vivo gene transfer. In an attempt to define the mechanism(s) responsible for persistent gene expression following partial hepatectomy, we characterized the molecular state of the retained, liver-associated transgenes. Southern blot analysis of DNA from liver tissues harvested various times after in vivo gene transfer and partial hepatectomy (10 min to 11 weeks) demonstrated high levels of transgene DNA (100-10,000 copies/cell). The predominant form of this DNA appeared to be episomal based on analyses of uncut DNA or DNA restricted by an endonuclease with one site in the plasmid. Livers from several animals contained a small proportion of transgene sequences of unknown structure. The existence of episomal DNA in liver was confirmed in experiments in which intact plasmid was rescued from total hepatocyte DNA by transformation of bacteria. Both strands of DNA in the liver-associated plasmid retained a bacterial pattern of methylation suggesting that the plasmid had not replicated in the eukaryotic cell. These results are consistent with the hypothesis that the majority of transgene sequences are retained as stabilized plasmids. The specific form of DNA which is transcriptionally active was not identified in these studies. This represents a new mechanism for retaining foreign DNA in eukaryotic cells in vivo and has implications both for the development of somatic gene therapies and the pathogenesis of viral diseases.

Animals↗