Heart

Remove the heart (with epicardium) from the remainder of the pericardium

Find these structures:

• • Epicardium

  • Coronary (atrioventricular) sulcus

  • Anterior interventricular sulcus

  • Posterior interventricular sulcus

  • Sulcus terminalis

Photo 1. Heart in the pericardium, thymus gland reflected

1.) Using scissors, transect the superior and inferior vena cavae within 2 cm of the heart

Photo 2. Incisions of superior & inferior vena cavae

2.) Pass a finger or a blunt instrument through the transverse pericardial sinus, and gently pull the ascending aorta and pulmonary trunk anteriorly. Using scissors, carefully transect the ascending aorta and pulmonary trunk about midway between the heart and the bifurcation of the pulmonary trunk.

Photo 3. Incisions of the ascending aorta & pulmonary trunk (finger in transverse pericardial sinus)

Photo 5. Pericardial cavity, heart removed

4.) Examine the heart before further dissection. Locate the epicardium, coronary (atrioventricular) sulcus, anterior interventricular sulcus, posterior interventricular sulcus, and sulcus terminalis.

Note: The epicardium is the visceral layer of serous pericardium. It can be very difficult to separate from the deep epicardial fat. The epicardium and epicardial fat will be removed simultaneously later in this dissection.

Note: The sulci are typically covered with varying amounts of epicardial fat. Arteries located within the sulci are often visible, and can help in locating these sulci.

Photo 6. Heart, anterior

Photo 7. Heart, inferoposterior

Photo 8. Heart, inferior

Note: The sulcus terminalis is the external demarcation of the crista terminalis. It is a very slight, vertical groove anterior to the superior vena cava.

Photo 9. Heart, right lateral

Remove the epicardium (visceral serous pericardium) and locate coronary vasculature

Find these structures:

• • Epicardial fat

  • Right coronary a. (RCA)

    • Sinu-atrial (SA) nodal br. [possibly a branch of the Circumflex br.]

    • Right marginal br.

    • Atrioventricular (AV) nodal br. [possibly a branch of the Circumflex br.]

    • Posterior interventricular br. [possibly a branch of the Circumflex br.]

  • Left coronary a. (LCA)

    • Anterior interventricular br.

    • Circumflex br.

      • Left marginal a.

  • Coronary sinus

    • Great cardiac v.

    • Middle cardiac v.

    • Small cardiac vv.

  • Anterior cardiac vv.

The epicardium encases adipose tissue, referred to as epicardial fat.

Note: The epicardial fat is varied in amount and distribution, but tends to concentrate in the coronary sulcus, anterior and posterior interventricular sulci, and around the origins of the great vessels.

5.) Locate the ascending aorta and bluntly remove the epicardial fat surrounding this vessel. Be careful not the sever the origins of the right and left coronary aa. Also take caution to not sever the SA Nodal br.

Photo 10. Epicardial fat at the base of the great vessels

6.) Examine the aortic sinus(es) by looking into the ascending aorta. Depending on the age and health of your donor, you may be able to discern the origins of the right and left coronary aa.

Photo 11. Closeup of the external origins of the RCA & LCA

7.) Locate the RCA, and clean any surrounding epicardium and epicardial fat. Follow the RCA to locate its branches.

• • Sinu-atrial nodal br.

Note: The SA nodal br. is a branch of the RCA in 60% of individuals. In 40% of cases, it is a branch of the circumflex br. of the LCA. (Moore et al., 2014). It branches near the ascending aorta toward the SA node located near the junction of the R. atrium and superior vena cava.

Photo 12. SA nodal br.

Note: The RCA typically travels between the ascending aorta and the right auricle as it enters the coronary sulcus. Use caution as you uncover the RCA at this point, as there are several (3-5) anterior cardiac vv. that travel superficially over the RCA from the right ventricle to the right atrium. Preserve these veins.

Photo 13. Anterior cardiac vv.

• • Right marginal br.

Note: The R. marginal br. of the RCA is located along the inferior border of the heart and is typically the last anterior branch of the RCA.

Photo 14. Right marginal br.

• • Atrioventricular (AV) nodal br.

  • Posterior interventricular br.

Note: The AV nodal and posterior interventricular brs. arise from the RCA in 67% of individuals, and the circumflex br. of the LCA in 33% of cases (Moore et al., 2014). The AV nodal br. arises near the posterior interventricular br. and dives deep and superior toward the AV node.

Note: Heart dominance is determined by the origin of the posterior interventricular br. Right dominance indicates that the source for the posterior interventricular br. is the RCA; left dominance is the LCA. In 18% of individuals, the posterior interventricular a. arises from both the RCA and the circumflex branch of the LCA, an arrangement known as codominance.

Photo 15. Posterior interventricular and AV nodal brs. of a right dominant heart

8.) Locate the LCA, and remove any surrounding epicardium and epicardial fat. Follow the LCA, and locate its 2 main branches: anterior interventricular br. and circumflex br.

• • Anterior interventricular br.

  • Circumflex br.

Photo 16. Anterior interventricular br. and circumflex br. of LCA

9.) Locate the left marginal a., which is a branch of the circumflex br. of the LCA. This artery follows the left border of the heart.

• • Left marginal a.

Photo 17. Branches of the circumflex br. of LCA

10.) Starting in the anterior interventricular sulcus, locate the great cardiac v., and follow it back to the coronary sinus. This vein closely associates with the anterior interventricular br. of the LCA.

Photo 18. Great cardiac v.

Rotate the heart to follow the coronary sinus to the diaphragmatic surface of the heart. Here you should see the confluence of the middle cardiac v. (coming from the posterior interventricular sulcus) with the coronary sinus. The middle cardiac v. is associated with the posterior interventricular br..

Photo 19. Middle cardiac vein

Rotate the heart to its anterior surface. The small cardiac v. may be visible near the inferior border, associated with the right marginal br. The anterior cardiac vv. form bridges over the RCA (from the right ventricle to the right atrium).

Note: Recall that the anterior cardiac vv. are unique from the other cardiac veins in that they typically drain directly into the right atrium, rather than into the coronary sinus.

Photo 20. Small cardiac v. and anterior cardiac vv.

Open the chambers of the heart, and examine internal features

Find these structures:

• • Myocardium

  • Endocardium

Photo 21. Heart wall, epicardium removed

10.) Make four incisions through the heart wall as shown in the image(s) below. If done properly, you should not sever any of the vasculature of the heart. Once complete, use forceps to remove coagulations. You may rinse the chambers clean to best visualize the fine features of each chamber.  

Incision One: R. atrium

Make a longitudinal incision, using scissors, starting at the superior vena cava and continuing inferiorly to the inferior vena cava.

Photo 22. Incision of the R. atrium

Incision Two: R. ventricle

With scissors, make a longitudinal incision starting at the pulmonary trunk to the inferior border of the heart. Continue this incision laterally toward the right atrium, above the R. marginal a.,taking care to avoid the anterior cardiac vv.

Photo 23. Incision of the R. ventricle

Incision Three: L. atrium

Rotate the heart such that the base of the heart is facing you. Make a longitudinal cut with scissors through the L. atrium between the openings of the pulmonary vv.

Photo 24. Incision of the L. atrium

Incision Four: L. ventricle

With scissors, make a vertical cut through the L. ventricle. This incision should be between the anterior interventricular br. and the L. marginal a. The myocardium in the L. ventricle is thick in comparison to the other chambers.

Photo 25. Incision of the L. ventricle