J Vet Sci.  2017 Mar;18(1):67-71. 10.4142/jvs.2017.18.1.67.

Surgical access via right thoracotomy facilitates tricuspid valve surgery in sheep

• Bothe W
• Diab M
• Ostermann
• Schwarzer
• Woelfel L
• Bischoff S
• Schubert H
• Doenst T

• KMID: 2412589
• DOI: http://doi.org/10.4142/jvs.2017.18.1.67

Abstract

In quadrupeds, the three-dimensional orientation of the heart with respect to the thorax is fundamentally different from that in humans. In this study, we assessed the best surgical approach to the tricuspid valve in sheep. Firstly, different surgical access sites to the tricuspid valve were tested in sheep cadavers, the anatomy was analyzed, and the optimal surgical approach to the tricuspid valve was determined. Secondly - along with cardiopulmonary bypass and cardioplegic arrest -the chosen approach was tested in six adult sheep in vivo. Anatomical analyses revealed that a left thoracotomy provided optimal access to the aorta and left heart. However, visualization of the right heart was significantly impaired. In contrast, a right thoracotomy provided good access to the right heart, but the ascending aorta was difficult to approach. Therefore, in the in vivo studies, arterial cannulation was performed through a carotid (n = 4) or femoral (n = 2) artery. In conclusion, a right-sided thoracotomy allows good visualization of all components of the tricuspid valve complex in sheep, but not of the ascending aorta. Consequently, peripheral vessels are preferred for arterial cannulation. This work may stimulate the investigation of pathomechanisms and/or novel treatment options for tricuspid valve pathologies.

Keyword

animal model; cardiac surgery; tricuspid valve

MeSH Terms

Animals
Female
Sheep/*surgery
Thoracotomy/*veterinary
Tricuspid Valve/*surgery

Figure

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  Fig. 1 Sheep in a left lateral position with neck and left groin prepared for puncture/cannulation of the peripheral vessels (A). The location of the left femoral and right carotid artery is displayed in B and D, respectively. (B) The position of the femoral vessels changes significantly depending on the degree of flexion/extension of the leg, and the femoral vessels may be located underneath thick muscle bundles. (C) The surgical situs after insertion of the rib retractor. The phrenic nerve runs along the upper border of the pericardium. (D) The right common carotid artery after surgical exposure. The catheters in the upper right corner are lying in the jugular vein.

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  Fig. 2 Schematics of a sheep in a left lateral position and the surgeon standing either on the front (A) or back (B) side of the sheep. The first part of the surgery (until opening of the right atrium) was performed from the front side (C-E). The pericardium was opened and the heart suspended in a pericardial cradle (C). Right atrium (RA) and ventricle (RV) as well as both caval veins (vena cava inferior [VCI] and vena cava superior [VCS], respectively) and coronary sinus (CS) are clearly visible and easy to access. In this study, implantation of radiopaque markers on the valve leaflets required cardioplegic arrest. Therefore, aorta and brachiocephalic trunk had to be clearly exposed. Note that aorta and pulmonary artery (PA) cannot be seen via a right thoracotomy without additional exposure (C). (D) The situs after manual retraction of the RA. The ascending aorta (AAo) has been dissected from the PA and is encircled by vessel loops. The AAo is significantly shorter in sheep (2–3 cm) than in humans (4–5 cm) due to an early branching of the brachiocephalic trunk (BCT). The blue line indicates the distal end. (E) The situs after cannulation of both caval veins and insertion of the cardioplegic cannula (arrow). After aortic cross clamping the surgeon switched locations to the back side of the sheep (F). (F) Tricuspid valve annulus (TA; yellow line), tricuspid septal leaflet (TSL), and the heads of the tricuspid septal papillary muscle (TSPM) after implantation of radiopaque markers.

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