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Revista chilena de anatomía

Print version ISSN 0716-9868

Rev. chil. anat. vol.17 n.1 Temuco  1999

http://dx.doi.org/10.4067/S0716-98681999000100011 

ANATOMIC STUDY OF THE DIAGONAL ARTERIES IN HEARTS OF PIGS

ESTUDIO ANATOMICO DE LA ARTERIA DIAGONAL EN CORAZONES DE PORCINOS

* Maria Tereza Jordão
** Sônia M. M. Gomes Bertolini
*** José Henrique dos Santos Areas Júnior
**** Nadir Eunice Valdeverde Barbato de Prates
SUMMARY: Considering the importance of the diagonal artery for myocardial vascularization and the existence of a series of similar features between the hearts of men and pigs, this reserch was carried out to make a morphometric study of the diagonal artery in hearts of pigs. For this study 100 hearts of pigs were used. Coronary arteries of these hearts were injected with 15% gelatin solution stained with red chess. Next, the hearts were fixed in 10% formol solution for 10 days and dissectd to allow visualization of the diagonal artery and measurement of the ventricular height. It was considered diagonal artery only the vessel emerging from the angle between the anterior interventricular and circunflex arteries. It was observed that the diagonal artery in the hearts of pigs was present in 20% of the samples. Its lenght varied from 11,33 mm to 39,5 mm, with mean of 22,4 mm, being the majority (95%) described as artery of short course on the subepidardial plane. As for its behaviour, it was noted that it gave rise to a single branch in 50% of the cases, two branches in 45% of the cases and in one case (5%) it gave rise to three brances. It can be concluded that in case of absence of the diagonal artery the circunflex artery gives rise to many branches, possibly to play the role of irrigation suplly of the left ventricle.

INTRODUCTION

The system of coronary arterial nutrition on the human heart, which is being subject of concern to researchers (anatomists and clinicians), shows a large number of variations of irrigation. The left coronary artery generally gives rise to septal branches on its initial portion and divides into the anterior interventricular and circumflex branches. Nevertheless, some authors describe that the trunk of the left coronary artery sometimes exhibits trifurcation, giving rise to the anterior interventricular, circumflex and diagonal branches (BANCHI, 1904; CRAINICIANU, 1922). This last branch, which is not included on the current Nomina Anatomica (1980), has diverse synonymity such as median branch, diagonalis artery, lateralis artery and artery of the trifurcation of the left coronary.

artery had its importance highlighted by performing a role of irrigation supply in cases of obliteration of the costal collateral branches of the anterior descending artery (PAULA, 1972).

BAPTISTA et al. (1991), referring to the work of GEIRINGER (1951), who believes that the myocardial bridge protects the vessel against atherosclerosis, relates the presence of small and medium-diameter diagonal vessels to the decreasing risk of coronary atherosclerosis.

Due to the importance of the artery for the vascularization of the myocardium in cases of obliteration of the left coronary artery branches, and taking into account that the hearts of pigs are the most appropriate for xenotransplantations, once they have morphology and physiology similar to those of human hearts, in addition to these animals being easy to raise and of rapid growth, this work was carried out with the aim of making a macroscopic study of the diagonal artery in hearts of pigs.

MATERIAL AND METHOD

For the fullfilment of this research it was used 100 hearts of male and female pigs resulting from the beeding of Landrace and Large White races coming from the Experimental Farm of Iguatemi, owned by the State University of Maringá.

Pieces were used soon after animals had been killed. They were washed in running tap water; next the arterial orifices were located and catheterized for injection of 15% gellatin solution stained with red chess. Injection was carried out under constant pressure until the filling in of the whole arterial bed.

Hearts were fixed in 10% formol solution for at least 10 days. The coronary arteries were then dissected under Zeiss stereomicroscope, the subepicardial fat being removed so as to allow visualization of the diagonal artery. When the diagonal artery was present, its length was measured with a Swiss Precision 20 ºC - PAV manual calypers.

It was considered as diagonal artery those emerging from the angle between the anterior interventricular and circumflex arteries.

Taking as a base the ventricular height the ventricle was divided into three segments (proximal, medium and distal) for classification of the diagonal artery, according to its length relative to the ventricular height, as: short, medium or long.

RESULTS

The left coronary artery, on the hearts of pigs used in this investigation, splitted into two in 79% of the cases (Fig. 1), into three in 20% (Fig. 2) and into four in 1% (Fig. 3). After its origin, the diagonal artery travelled obliquely towards the cardiac apex. Its course was superficial, very brief and soon became intramyocardial (Fig. 2). The smallest diagonal artery found had 11,3 mm length and the largest, 39,5 mm, averaging 22,4 mm. The maximal relative length of the dia gonal artery varied from 12,86% to 46,19% of the left ventricle length, the mean value being 24,73%.


Figure 1 - Photograph of heart of pig evidencing the left coronary artery (arrow) bifurcating into anterior interventricular branch (I) and circum-flex branch (C).

Figure 2 - Photograph of heart of pig showing the diagonal artery (arrow) giving off one collateral branch (D).


Taking as reference the ventricular height it was verified that in 19 cases (95%) the diagonal artery was short (Fig. 3) and in one (5%) it was medium (Fig. 4). This result demonstrates the short path of this vessel on the subepicardial plane.

Figure 3 - Photograph of heart of pig evidencing the left coronary artery trifurcating (arrow) in anterior interventricular branch (I), circumflex branch (C) and diagonal branch (D).

Figure 4 - Photograph of heart of pig evidencing the left coronary artery quadrifurcating (arrow) into anterior interven-tricular branch (I), circumflex branch (C) and two diagonal branches (D and D').


The maximal initial diameter of the diagonal arteries on the supepicardial plane was 3,6 mm, and the minimal was 1,3 mm, the mean being 2,08 mm. In all the cases the initial diameter of the anterior interventricular artery was greater than that of the diagonal artery. As for the circumflex artery, excepting one case, its initial diameter was also greater than that of the diagonal artery.

When analyzing the length of the diagonal artery on the subepicardial plane, it was noted that 10 arteries (50%) gave off one branch (Fig. 2), nine (45%) gave off two branches (Fig. 3) and only one (5%) gave off three branches (Fig. 4). Most of these cases were considered as short branches. It was also observed that in only three hearts in which the diagonal artery was present, the circumflex artery gave off only one branch, while on the hearts where the diagonal artery was absent, the circumflex artery gave off from one to seven branches, averaging four branches.

Figure 5 - Photograph of heart of pig showing the diagonal artery (arrow) trifurcating into (D, D' and D'').

Figure 6 - Photograph of heart of pig showing the diagonal artery (arrow) bifurcating into (D and D').


DISCUSSION

on the literature it was observed that most of the authors agree that the left coronary artery frequently gives off two branches: the anterior interventricular artery and the circumflex artery (BANCHI, 1904; SMITH, 1962; BAROLDI & SCOMAZZONI, 1967; FAVALORO, 1970; ARIE et al., 1971; PAULA, 1972; LEGUERRIER et al., 1976; VLODAVER et al., 1976; CARVALHO, 1978; PAULIN, 1983).

In this research the incidence of the diagonal artery was of 20%. Similar incidences are observed on the work of LEGUERRIER et al. (1976) and ANDERSON & BECKER (1983). It should be stressed that the hearts studied for those authors were of human beings. on the other hand, a low incidence of diagonal artery is reported by VELICAN et al. (1981) and PENTHER et al. (1976) in human hearts (6,5% and 9%, respectively). Nevertheless, PAULA (1972) finds this vessel in 81,6% of the cases and GRANDE et al. (1982), in 89,5%.

Concerning the length of the diagonal artery, the smallest had 11,3 mm length and the largest 39,5 mm, averaging 22,4 mm, so that most of them (95%) were classified as arteries of short extension. Similar finding is reported by BANCHI (1904). As for the relative length, the diagonal artery varied from 12,86% to 46,19% of the left ventricle length, with mean value of 24,73%. These findings are in disagreement with those of BAPTISTA (1987). This can be possibly explained by the fact that the species were different and thus had different vascularization patterns.

When observing the diameter of the diagonal artery, it was verified that in most of the cases this was smaller than that of the anterior interventricular artery. These results agree with the observations made by ROCHA-LAGÔA (1928) and BAROLDI & SCOMAZZONI (1967).

As for the branching pattern of the diagonal artery, it was verified that it gave off from two to three branches. Similar division is observed by BAROLDI & SCOMAZZONI (1967).

When studying the behaviour of the circumflex artery, it was observed in 15% of the cases that, on the presence of the diagonal artery, the circumflex artery gave rise to only one branch. However, when the diagonal artery was absent, the circumflex artery gave off several branches. Possibly this is explained by the absence of the diagonal artery, in which case the circumflex artery take on the irrigation of the left ventricle.

For the identification of the diagonal artery, the same criterion adopted by CRAINICIANU (1922) was used in this investigation. It was considered diagonal artery, only the vessel arising from the angle formed by the anterior descending branch and the circumflex branch. This criterion was also used by PAULA (1972) and ANDERSON & BECKER (1983).

With no criteria to detect the presence of the diagonal artery, PENTHER et al. (1976) considers this vessel as either coming from the superior portion of the anterior interventricular artery or the branch resulting from the trifurcation of the left coronary artery or as a branch of the circumflex artery.

SMITH (1962), MAY (1969) and FAVALORO (1970) consider as diagonal artery only the branches coming from the anterior descending branch. They identify the diagonal artery sectioning the angle between the descending and circumflex arteries, and considering that it can arise from one of the branches or between them. To BAROLDI & SCOMAZZONI (1967) and GENSINI et al. (1976), the diagonal artery is always a branch from the anterior descending artery and had apparent origin on the left coronary artery as a false trifurcation of the common trunk.

MaC ALPIN et al. (1973) and NEIMANN et al. (1976), report that the diagonal artery arises as an early branch of the circumflex artery, observing this vessel in 1/3 of the cases. VIEWG et al. (1975) also describes that the diagonal artery can arise from the initial portion of the circumflex branch. If this same criterion was used on the present investigation, the diagonal artery would be present in 43 hearts (43%).

As observed by LEGUERRIER et al. (1976), in this work one case of diagonal artery quadrifurcation was present. Some authors also find the left coronary artery giving rise to four or more branches (WALMSLEY & WATSON, 1978).

The terminology 'diagonal artery' is opposed by PAULIN (1983). This author explains that the branch originating on the center of the bifurcation of the left coronary artery is named 'intermediate branch' and that the number of diagonals varies from one to six, being their extension and distribution dependent of the presence or not of the intermediate branch.

An occasional presence of the diagonal artery is reported by FAVARO (1970), VLODAVER et al. (1976) and CARVALHO (1978).

The classification adopted by BORELLI & BORELLI (1996) for the diagonal artery into types I, II and III, differs from that used in this investigation. This fact can be attributed to the differences of vascularization found on the hearts of cats and pigs.

RESUMEN: Debido a la importancia de la arteria diagonal en la vascularización del miocardio y a la existencia de características semejantes entre el corazón del hombre y del porcino, realizamos un estudio morfométrico de la arteria diagonal en 100 corazones de porcinos. Se inyectaron las arterias coronarias con una solución de gelatina al 15%, teñida de rojo. Luego, los corazones fueron fijados en solución de formol al 10%, por un período de 10 días y disecados para visualización de la arteria diagonal y comparación de la altura ventricular. Sólo se consideró como arteria diagonal al vaso que emergía de la bisectriz del ángulo formado por la arteria interventricular anterior y circunfleja. La arteria diagonal estuvo presente en el 20% de los casos. Su longitud varió entre 11,3 mm y 39,5 mm (x 22,4 mm), por lo que se clasificó a la mayoría de ellas (95%), como arterias de corto trayecto en el plano subepicárdico. Con relación a su ramas, se verificó que dicha arteria emitía una rama en el 50% de los casos, 2 ramas en el 45% y 3 ramas en el 5%. Se puede concluir entonces, que en el caso de ausencia de la arteria diagonal, la arteria circunfleja emitiría varias ramas, seguramente para suplir la insuficiente irrigación del ventrículo izquierdo.

PALABRAS CLAVE: 1. Arteria diagonal; 2. Corazón; 3. Suinos.

* Universidade Paranaense, Paraná, Brasil.
** Universidade Estadual de Maringá, Paraná, Brasil.
*** Bolsista CAPES.
**** Instituto de Ciências Biomédicas da Universidade de São Paulo, Paraná, Brasil.
 
Dirección para correspondencia:
Prof. Dra. Maria Tereza Jordão
Rua Visconde de Nassau, 712
Edifício Monza Apto. 104-A
Bairro- Zona 7
CEP 87020-030
Maringá - Paraná
BRASIL


Recibido : 06-06-1999
Aceptado: 11-07-1999

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