close

Вход

Забыли?

вход по аккаунту

?

The technique of heart plastination.

код для вставкиСкачать
THE ANATOMICAL RECORD 204295-299 (1982)
The Technique of Heart Plastination
K. TIEDEMANN
AND
G.v. HAGENS
Anatomical Institute I, Uniuersity of Heidelberg, Im Neuenheimr Feld 307, 6900
Heidelberg, Federal Republic of Germany
ABSTRACT
Plastinated hearts are natural specimens, preserved in a firm
or flexible state, which thus can be grasped in the hand. They are fixed in a dilated
state. Their tissue water and lipids are replaced by polymerized synthetic resins
or elastomers. The final specimens show doubly injected coronary vessels, opened
atria and ventricles, thus exhibiting all finer external and internal details. The
procedure described consists of the removal of the heart; intermediate storage
facilities; dilatation with water under hydrostatic pressure; color injection of the
coronary vessels; fixation; dehydration in acetone under hydrostatic pressure;
forced impregnation in a vacuum chamber; and hardening with aftercare. Technical variations and pitfalls are discussed, as well as the required equipment.
In the teaching of anatomy, pathology, and
surgery, the heart is one of the few organs which
cannot be grasped through a lecture. As is the
case of the brain, its complex external and internal shape is understood only when an open
cut specimen is actually grasped in the hand.
Artificial models do not reveal finer structural details. As they are uniformly manufactured, peculiarities of different species, congential malformations, and pathological
alterations cannot be demonstrated. Dry specimens preserved with conventional methods,
such as freeze drying (Hower, 1979) or paraffinization (Schmeidel, 1925; Hochstetter, 1927),
are brittle and the intransparent paraffin masks
finer details. Cleared and corroded heart specimens, plastic-embedded after a vascular injection (Wolfe, 1956) aim only a t the perfect
demonstration of the heart's vascular system.
Through the new process of plastination
(v.Hagens, 1979a), real specimens are impregnated with thermosetting resins or elastomers
of desired optical qualities (v.Hagens, 1979b)
which replace the original tissue water and
part of the lipids. A mechanically resistant
flexible or firm specimen of approximately natural size which is odorless, dry, and durable is
obtained. Plastinated hearts, which have been
fixed in their dilated state to improve their
instructive value, not only show doubly injected coronary vessels, but are fenestrated and
thereby reveal all the internal structures (Fig.
la, b).
0003-276x182/2043-0295$0200 fi) 1982 ALAN R. LISS, INC
PROCEDURE
The sequence of the main steps is as follows:
1)Removal from the body
2) Dilatation under hydrostatic pressure
3) Color injection of the coronary vessels
4)Fixation under hydrostatic pressure
5) Dehydration under hydrostatic pressure
6) Impregnation in a vacuum chamber
7) Hardening and aftercare
Removal
All public vessels must be cut far away from
the heart, as they must be tightly tied off in
order to accomplish dilatation (step 2). The large
lung vessels must be loosened away several
centimeters from the lung tissue. Removed
hearts can be stored in a frozen state or processed after rigor mortis. Fresh hearts can be
stored in tap water for 5-10 days in a refrigerator (+ 5°C).
Dilatation
In order to accomplish dilatation, a short polyethylene tube ($3 8-15 mm) is inserted into
one of the lung veins and a second tube into
the anterior vena cava as shown in Figure 2.
The tubes, which hold better when they have
a ridge made with a soldering iron, are connected t o a water tap. The water removes blood
clots and fibrin and shows which of the apReceived January 13, 1982; accepted July 22, 1982.
296
K. TIEDEMANN AND G.v. HAGENS
Fig. 1.a. Plastinated dog heart, left side view. Both ventricles are cut open, the right one exhibiting parts of the
tricuspid valve. From the doubly injected coronary vessels,
the red injected arteries are indistinct due to the black and
white reproduction. b. Right side view of the same heart,
the atrium fenestrated by a flap.
proximately 25 vessels must be tied off. Cork
stoppers are used to retain the rounded shape
of larger vessels (Fig. 2).
Dilatation is performed with tap water under hydrostatic pressure with the tubes connected to a water tank located 40-80 cm above
the organ. The pressure at the origin of the
aorta results in a complete rinsing of the coronary vessels, and the continued pressure dilatation, sustained for several hours in a dog
heart and up to 2 days in a cattle heart, leads
to a permanent relaxation of the heart muscle.
jection of the red resin with a disposable syringe forces the resin as far as the arterial
capillaries and is ended by tying off when the
myocardium and the adipose tissue have taken
a reddish color, which gives the whole specimen an almost natural tone.
For the retrograde color injection of the heart
veins with the blue epoxy resin we use the
coronary sinus via the posterior vena cava. In
small species, such as the dog, the tying off of
the coronary sinus with a thread is difficult
because of its tenuous wall. We therefore use
polyethylene tubing, with a thicker piece of
tubing attached (Fig. 3B),which, passed through
the vena cava, can just be pressed into the coronary sinus. This tubing remains in place after
the injection until the resin is gelated. In cattle, we tie off the coronary sinus around a thick
cone of a needle (Fig. 3A); a finger can be inserted into this large vessel t o feel the tip of
the curved tweezers which force the thread
around the vessel. The great cardiac vein is
easily filled;the resin can be forced further into
the smaller branches by rubbing the bulging
Color Znjection
For the injection of the coronary vessels with
a colored epoxy resin, red and blue BIODUR
E 201with the hardener E 2 is used. The coronary arteries are injected from within by the
use of a needle with a cone at its tip (Fig. 3A).
This needle, introduced into the brachiocephalic artery, is placed into the orifice of the
coronary artery. The stem of this vessel, hidden under the respective auricle, is lifted up
with bent forceps, and a thread for its later
tying off is layed around it. The groove in the
cone of the needle permits a temporary fixation
with this thread during the injection. The in-
'BIODUR Jahnstr. 8, D-6900 HeidelbergGermany
TECHNIQUE OF HEART PLASTINATION
2
297
3
Fig. 2. Posterior view of a heart from above. One lung
vein and the anterior cava vein carry a polyethylene tube.
The other vessels (except the posterior cava vein) are tied
off; the aorta and pulmonary arteries are closed with cork
stoppers.
Fig. 3. Instrumentsfor the color injection of the coronary
vessels. A) Needles with a cone at their tip. B) Connected
polyethylene tubing for the m u l a t i o n of the coronary sinus
in smaller species.
veins with the finger tips. The middle cardiac
vein is frequently filled through anastomoses
around the tip of the heart. Air bubbles found
in the veins mainly travel the same way. The
middle cardiac vein is tied off with a surgical
needle and thread before the resin, which follows the air bubbles, empties into the right
atrium. Alternatively, this vein-and in human hearts also the small cardiac vein-can
be cannulated a t its opening in the orifice of
the coronary sinus. After the injection, a short
powerful water rinse via the two polyethylene
tubes removes the small amounts of colored
epoxy resin which may have entered the atria
and ventricles from the injection sites or from
veins opening directly into the atria.
tubes and hydrostatic pressure. Fixation occurs after the color injection, when the resin
is still flexible enough to allow expansion of
the heart. The heart, whose tissue maintains
some resiliency, becomes fixed in its dilated
state for several hours and becomes temporarily dull in color as it loses its tissue transparency. Depending on the thickness of its ventricular walls, the heart remains immersed for
1 or several days in the formalin, where it can
also be stored before further processing.
Fixation
Fixation with 20% formalin solution (20 parts
3538 wt.% formaldehyde solution in water and
80 parts tap water) proceeds in the same way
as the dilatation with the insertion of the two
Dehydration
A water rinse before dehydration is useful
to double-check whether or not all vessels are
tied off. After emptying the heart, technical
acetone in a grade between 96 and 100% is
applied in the same manner as in the dilatation
step. The continual hydrostatic pressure counteracts the shrinkage of the heart; only hollow
organs can be dehydrated by this rapid method.
A heart of a human being or dog requires 5 kg
298
K. TIEDEMANN AND G.v. HAGENS
of acetone; a cattle heart requires up to 80 kg
over a period of 8 hours. When acetone in an
amount five times greater than the volume of
the heart has seeped through its walls, the heart
becomes rigid. In this time frame, the final
shape of the heart and position of its large vessels still may be corrected.
After the pressure-dehydration, the hardened heart is kept in pure acetone with several
changes until a concentration of a t least 99%
is maintained. During this time, all threads,
cork stoppers, and the two tubes are removed.
The atria are cut open in a semicircular line
so that a flap can be turned up and fixed by a
ligature. The fenestration of the right ventricle
must not damage the transverse muscle of the
heart. Similarly, the ovoid opening in the left
ventricle should not destroy the anterior papillary muscle but must offer a view into the
origin of the aorta below the septa1valve. Remnants of fibrin and colored resin are now removed from the interior of the organ.
Impregnation
Impregnation can be accomplished with three
different curable resins depending on the desired mechanical properties and transparency
of the final specimen. A solid but breakable
specimen, best suited for display due to the
clearness of its injected vessels, is impregnated
with the inexpensive BIODUR PEM 27, a specially formulated epoxy-siliconecopolymer,plus
the hardener E 6 and accelerator E 60.
Flexible specimens better suited for the handling by students are obtained by impregnation with a more expensive silicone, whose
opacity renders the vascular injection less clear.
Two silicones have been approved. BIODUR S
20 is less opaque, but may be damaged by tearing, so that its use is more practical for a teacher
rather than a student. The silicone BIODUR
S 10 obscures finer details of the specimen, but
is more easily processed, and its high tear resistance makes it ideal for student use.
The heart remains in either solution in a
vacuum chamber for 1-3 days. The basic principle of the forced impregnation process is that
the acetone, which is continuously pumped out
of the heart and through the surrounding polymer bath in its gaseous state, draws this polymer into the specimen. The vacuum is turned
off when bubbles of the evaporating acetone
cease to appear at a pressure of 5 mm Hg.
Hardening and Aftercare
After the hearts have been taken out of the
polymer bath, excess resin is poured out and
thoroughly wiped off from the BIODUR PEM
27 or S 20, while S 10 specimens need only to
be drained. To maintain the cava veins in their
correct position, they must be plugged before
hardening, e.g., with silicone stoppers.
The hardening is achieved for PEM 27 at
50°C, for BIODUR S 20 a t ambient temperature, and for BIODUR S 10 in a final curing
bath, followed by drying at 50°C in order to
remove excess curing agent. Polypropylene foil
must be used to prevent sticking of the specimens to their underlying surface.
DISCUSSION
During the removal of the organ, many hearts
are injured by piercing, or their vessels are cut
too short so that they cannot be tied off. Failure
to tie off only one of the intercostal or bronchial
arteries still permits dilatation, but later causes
costly leakage of acetone.
Pressure dilatation of the heart with water,
already described by Luciani (1905) as cited by
Monckeberg in Abderhalden's manual (1924),
leads to a relaxation of the heart muscle exceeding the physiological diastolic state. The
most prominent dilatations are those of the
pulmonary artery and the atria. This initial
overexpansionbecomes markedly reduced during fixation and dehydration. Specimens showing insufficient dilatation of the left ventricle
are more frequently seen than those with an
overexpanded right heart. The pressure-dilatation of the heart ends when the original elastic consistency of the organ has distinctly
changed into a flabby one.
The color injection can also be performed after the fixation of the heart (and even on old
perfusion-fixed specimens taken from the dissection lab). However, this results in a less
complete filling of smaller vessels. Compensation for the rigidity of such fixed vessel walls
can be partly achieved by the use of hardener
E 3 instead of E 2, which gives the epoxy resin
BIODUR E 20 a lower viscosity and a much
longer pot life. This mixture is not used in fresh
hearts because the elastic wall tension of the
injected arteries propels it further into the capillaries after the completion of the injection
and the larger branches almost empty themselves through this undesired process.
During fixation, a green discoloration of the
coronary sulcus is sometimes observed, as the
hemolytic blood accumulates below the epicardium. This can be avoided by a prolonged
water dilatation or by a rinse of the coronary
arteries (via the aorta) with physiological saline immediately after removal of the heart.
TECHNIQUE OF HEART PLASTINATION
Dehydration can also be performed by freeze
substitution with acetone a t - 30°C (Schwab
and v.Hagens, 1981), a method recommended
for specimens that cannot be dilated, such as
old open cut formalin specimens. This alternative method requires less acetone than the
pressure dehydration and avoids the shrinkage
of the subepicardial fat. On the other hand, it
is more time consuming and renders the subepicardial vessels less distinct. As the acetone
consumption is an essential cost factor in the
large-scale production of plastinated heart
specimens, a distillation unit is desirable. In
anatomical institutes, this can be achieved by
the conversion of a bone degreasing unit.
The impregnationprocess is explained in more
detail in technical leaflets for the polymers employed. As all resins used for the impregnation
can be reused after the removal of the impregnated specimens, a stock of fully dehydrated
specimens for a second or third run is of economic importance.
A common pitfall in heart plastination is focal discoloration of the organ due to threads or
cork stoppers which have not been color-proofed
or due to drying of the organ surface. The latter
easily happens during the handling in acetone,
and leads to an incomplete impregnation
(v.Hagens 1979a; Bickley 1980) with typical
white discolorations of the hardened specimen.
An insufficient color injection occurs when 1)
both large branches of the left coronary artery
have not been completely filled, 2) fine atrial
branches have been injured during the encircling of the respective coronary artery, or 31
vascular variations such as additional coronary arteries have not been considered. The
ramification pattern of the coronary vessels is
species-dependent;we found it most beautiful
(for display specimens) in the dog and unattractive in the pig.
The technical equipment necessary for heart
plastination is often found in morphological
institutes: a deep freezer, a vacuum chamber
(best with cooling devices for -2O"C), an explosion-proof vacuum pump, and a hot cabinet.
A bell jar and a water-jet vacuum pump can
be used as minimal equipment for the beginner.
The materials for the plastination of one dog
heart cost between $30 and $40; for a cattle
299
heart, $100-$150. The economy of scale reduces these costs by a third when solvents and
polymers are reused.
Plastination is covered by several patents
(v.Hagens, 1977-1981). Its use in public institutions like universities and schools, however,
is virtually unrestricted because the use of
BIODUR-polymers includes its use on a noncommercial basis.
These polymers were developed especially for
plastination over the last 5 years with major
support by BAYER AG, Leverkusen, BAKELITE GmbH, Iserlohn-Lethmate and BASF,
Ludwigshafen.
Our most annoying experience with heart
plastination is that plastinated specimens are
more quickly stolen than produced.
ACKNOWLEDGMENTS
We thank the chairman of the Anatomical
Institute I, Dr. W. Kriz for his kind support of
this project. We highly appreciate the efforts
of our chief technician, Mrs. Hiltraud Hosser,
for doing the major part of the practical work
involved.
LITERATURE CITED
Bickley, H.C. (1980) Preservation of gross tissue specimen
by plastination. Bull. Pathol. Educ., 6:5-7.
v.Hagens, G. (1979a) Impregnation of soft biological specimens with thermosetting resins and elastomers. Anat.
Rec., 194.247-256.
v.Hagens, G. (1979b) Emulsifying resins for plastination.
Der Praparator, 25:43-50.
v.Hagens, G.Patents: D.B. Pat. 27 10 147 (1977),Brit. Pat.
1 558 802 (19781, Belg. Pat. 863.949 (19781, R.S.A. Pat.
78/1330 (1978),Austr. Pat. 360 272 (1980),U S . Pat. 4,205,
059(1980),U.S.Pat. 4,244,992 (1981),U S . Pat. 4,278,701
(1981).
Hochstetter, F. (1927) Die Paraffindurchtrankung zur Erhaltung von Tieren und Pflanzen in ihrem naturlichen
Aussehen. Umsch., 31:650-652.
Hower, R.O. (1979) Freeze-Drying Biological Specimens: A
Laboratory Manual. Smithsonian Institution Press,
Washington.
Monckeberg,J.G. (1924) Die Methoden zur morphologischen
Untersuchung erkrankter Herzen. In: Handbuch der Biologischen Arbeitamethoden.E. Abderhalden, ed.Urban und
Schwanenberg, Berlin, Vol. VIII, pp. 635-650.
Schmeidel, G. (1925) Wie Paraffinpraparatehergestellt werden. Erg.-H. Anat. Anz., 60:282-283.
Schwab, K., G. v.Hagens (1981) Freeze substitution of macroscopic specimens for plastination. Acta Anat.,
111:139-140.
Wolfe, K. (1956) Plastic-embedded heartpcleared and corroded specimens. Arch. Pathol., 61~153-158.
Документ
Категория
Без категории
Просмотров
0
Размер файла
426 Кб
Теги
heart, plastination, techniques
1/--страниц
Пожаловаться на содержимое документа