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Two cases of coronary venous drainage by a persistent left superior vena cava in cat.

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TWO CASES O F CORONARY VENOUS DRAINAGE
BY A PERSISTENT LEFT SUPERIOR
VENA CAVA I N CAT
FRED N . ZEINER
Department of Zoology, University of Denver, Denver, Colmado
This condition was seen in two cats in the same group during classroom dissection. There are few previous reports.
Prows (’43) summarizes them and adds a case from man. The
only previous report of this anomaly in cat is that of Grant
(’17). Chouke (’39) gives an extensive bibliography of related anomalies.
DESCRIPTION AND DISCUSSION
A sizeable vein joined the left innominate at the junction of
subclavian and external jugular veins and extended toward
the heart in a nearly straight line. It differed from the often
reported “left precava,” which empties into the right atrium
through the coronary sinus, in having direct continuity with
v. cordis magna and there was no coronary sinus. The main
ventral branch of the v. cordis magna attained the dorsal side
by running through the coronary sulcus. Here at the dorsoanterior portion of the left ventricle it received the dorsal
contribution and also attached to the left precava. There was
nothing extending transversely through the coronary sulcus
from this point toward the right atrium in the normal position
of the coronary sinus. There was no indication of a coronary
orifice or Thebesian valve in either cat.
With one exception the literature of persistent left precavae
mentions the existence of a coronary sinus and, in this case
(Basu, ’32), the portion of the left precava receiving the coronary veins would be described by others as a coronary sinus.
275
T H E ANATOMIOAL RECORD, V O L 129, NO. 3
NOVEMBEE 1957
276
FRED N. ZEINER
It is difficult to bound the sinus when the left precaval drainage is into the right atrium unless the portion of the vessel in
the coronary sulcus and receiving the coronary veins shows n
distinct swelling. Identification is simpler in cases of coronary
drainage through the left precava to the left innominate vein.
I n some (Prows, ’39 ; Reed, ’38) a blindly-ending, pouch-like
structure in the appropriate location and with a transverse
orientation therein receives the coronary veins and in turn
connects with the left precava. Grant’s interpretation (’17)
of a coronary sinus is questioned. The structure so-labelled
in his figure appears to be merely that part of the ventral
branch of v. cordis magna which runs through the coronary
sulcus on the left side. It is believed that his case was similar
to those reported here.
A developmental explanation has both obvious and clouded
features. The left precava results from persistence of the
more proximal part of the left anterior cardinal vein. Confusion in the story of coronary sinus development makes it
difficult to delimit the embryonic structures that have not
persisted. It appears that the channel between v. cordis magna
and the atrium atrophied before establishment of a large
coronary return and before atrophy of the left precardinal
segment. The suggestions advanced by Grant (’17) seem to
offer reasonable explanation for this.
The occurrence of a rare anomaly in two specimens of the
same shipment raises the possibility of a genetic basis. It is
probable that the two specimens were sibs, but this, unfortunately, could not be determined.
SUMMARY
Coronary venous drainage by a persistent left precava is
described in two cats. I n neither was a coronary sinus present.
The possibility of a genetic basis for the anomaly exists.
LITERATURE CITED
BASU,B. N. 1932 Persistent ‘left superior vena cava’, ‘left duct of Cuvier’,
and ‘left horn of the sinus venosus’. J. Anat., 66: 268-270.
ABERBANT CORONARY VEXOUS DRAINAGE
27 7
CHOUKE,K. S. 1939 A ewe of bilateral superior vena cava in an adult. Anat.
Rec., 7 4 : 151-157.
GRANT,8. B. 1917 A persistent supcrior vcna cava sinistra in the eat tran8mitting coronary blood. Anat. Rec., 13: 45-49.
PROWS,
M. A. 1943 Two cases of bilateral superior venae cavae, one draining
a closed coronary sinus. Anat. Rcc., 67: 99-106.
REED,A. F. 1938 A left superior Venn cava draining the blood from a closed
coronary sinus. J. Anat., 73: 195-197.
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drainage, persistence, two, venous, cat, vena, superior, case, coronary, cava, left
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