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New and simplified method for multiple left ventricle catheterizations in small animals

^a Section of Cardiac Surgery, The University of Michigan, Ann Arbor, MI 48109, USA
^b Department of Biomedical Engineering, The University of Michigan, Ann Arbor, MI 48109, USA

Received 20 May 2008; received in revised form 8 July 2008; accepted 9 July 2008

This work was supported by funds from the Section of Cardiac Surgery at the University of Michigan.

*Corresponding author. 2248 Lurie Biomedical Building, 1101 Beal Ave, Ann Arbor, MI 48109, USA. Tel.: +1 734-615-1481; fax: +1 734-615-2847.

E-mail address: fmigneco{at}umich.edu (F. Migneco).

	Abstract

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusions References

 
Ventricular catheterization in the rat is a widely deployed procedure. Current options allow a one-time catheterization procedure, introducing an error due to the inter-individual variability. Six Fischer rats underwent left ventricular catheterization through the right carotid artery, repeated seven days later via the left carotid artery. We acquired volume and pressure data from each animal during both procedures. Volumes and pressures were plotted to construct pressure–volume loops at the two time-points. The neurological outcome and the gross anatomy of the heart were also evaluated. We did not observe any major behavioral or neurological alteration in any of the animals. We observed a Horner syndrome with palpebral ptosis and enophtalmus in one animal. At the macroscopic evaluation of the explanted hearts, we observed perforation of the left ventricle in one case. This is a safe, easy, and reproducible procedure; it can be performed twice in the same animal with no neurological consequences. It is particularly suitable for longitudinal studies, to minimize the statistical error due to inter-individual variability.

Key Words: Rat catheterization; Animal models; In-vivo measurement; Left ventricle catheterization

	1. Introduction

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusions References

 
Rat ventricular catheterization is a widely used procedure in animal studies.

Several techniques have been reported [1–5]. All these procedures allow one-time catheterization, with limited suitability for repeated intra-individual hemodynamic measurements.

A new technique using a sequential approach of the right carotid artery has been described [6]. This method is suited for repeated catheterizations but requires complex, costly, and potentially unavailable equipment [6].

In the following study we report a simple technique to perform several catheterizations in the same animal with a simple, fast, and reproducible procedure.

	2. Materials and methods

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusions References

 
The University Committee for the Use and Care of Animals (UCUCA) granted approval for animal use, in accordance with the ‘Guide for the Care and Use of Laboratory Animals’ (NIH publication 86-23, 1986).

We used six male Fischer rats. Anesthesia was induced and maintained with an isoflurane/O₂ mixture. Intubation was performed with a 16G tracheal cannula under direct vision. The animals were mechanically ventilated (TOPO ventilator, Kent Scientific, Torrington, CT), and their temperature monitored.

A 2-cm incision was performed 2 mm to the right of the trachea, the sternocleidomastoid muscle isolated and mobilized laterally, to visualize the right carotid artery. The artery was dissected free, and exposed in its components: common, internal, and external portions.

We placed a first suture loop (silk 6-0) before the common carotid artery bifurcation, and a second, more proximal, at the common carotid artery (Fig. 1a). For the catheterization procedure we used a 20G over-the-needle cannula and, after puncturing the vessel just below the bifurcation, the needle was retracted, the cannula advanced and stopped just before the proximal suture loop.

View larger version (103K): [in this window] [in a new window]   Fig. 1. (a) Picture of the right carotid artery isolated in its components (common external and internal). Note the proximal and the distal stay sutures to prevent bleeding at the puncturation site. (b) The tip of the cannula is inserted into the vessel, and through this the black catheter is positioned and gently pushed beyond the proximal stay suture. (c) As a result of closure of the right carotid artery, the right pinna auricularis supplied by terminal arteries (anterior and posterior auricular arteries) necrotizes. (d) Vision of the right ear after removal of the pinna.

The same procedure was used for the left carotid artery catheterization.

At the end of the procedure, the catheter was retracted along with the cannula, and the two loops ligated. The skin was sutured, the animal recovered.

On week later, the animals underwent the same procedure approaching the left carotid, and then sacrificed.

The signal from the catheter was acquired by an integrated, computerized system (Scisense, Inc. London, Canada; National Instruments, Austin, TX).

Right and left catheterization data acquired from each animal were used to derive the relative pressure–volume loops. The calculated hemodynamic parameters were expressed as mean±S.D. (Table 1).

	3. Results

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusions References

 
After the first procedure, the animals fully recovered within 30 min. None of them had neurological impairment, signs of hemilateral deficit, or functional limitations after the first catheterization. One animal suffered an accidentally ligated vagal ramus with signs of Horner syndrome. At the second procedure, a case of ventricular perforation, not detected intra-procedurally, was observed at the gross inspection of the heart. No other anomalies were noted. A constant finding in all the animals was an initial discoloration, followed by dry necrosis, of the tip of the right ear (Fig. 1c).

	4. Discussion

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusions References

 
Several approaches have been successfully used to perform left ventricular catheterization, but none of them has shown the possibility to be repeated in the same rat [1–5].

Recently a new technique has been reported [6]. They used a sequential approach: the right external carotid punctured first, then the common carotid. This procedure is effective and reproducible, but it is limited by complex and costly equipment [6]. In addition, they operated under the assumption that a monolateral ligation of the internal carotid inevitably leads to brain damage.

After ligation of a common carotid artery, the homolateral flow to the brain decreases only transiently; if the closure of the artery is maintained, the flow returns to the control baseline in a few minutes [7]. With ligation of both carotid arteries, the brain blood supply decreases 35%, which is enough to avoid cerebral damage [7].

To obtain a permanent and significant decrease of the brain flow, at least three arteries (one common carotid artery and both vertebral arteries) must be occluded, because the vertebral arteries are the main arteries responsible for maintaining cerebral blood flow [7, 8].

The Horner syndrome we observed was due to ligation of a small unseen vagal ramus, running posterior of the carotid artery.

We decided to approach the right carotid artery for the first catheterization and the left carotid for the second procedure. The path of the left carotid artery is more tortuous than the right carotid artery one, leading to a higher number of complications. For this reason we utilized the right carotid artery first to increase our chances of recovering the animal afterward, leaving the left carotid artery for the second, more risky, procedure.

As a complication of the second catheterization, we observed one case of ventricular perforation, not detected during the catheterization. It is likely that such small perforations are of little importance, going into spontaneous closure when the catheter is removed.

The mummification of the tip of the right ear a few days after the first procedure was a constant finding in each animal. We hypothesize that, since we ligate the right common carotid artery, this event is due to the lack of blood supply from the anterior and posterior auricular arteries, both terminal branches of the external carotid artery [9].

Although the necrosis was asymptomatic, to prevent any possible complications (gangrene, infections), our advice is to routinely perform a prophylactic excision of the distal portion of the right pinna (4–5 mm) (Fig. 1d).

	5. Conclusions

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusions References

 
We demonstrated that the approach of using both carotid arteries for hemodynamic study in the rat is a safe and fast method with no clinical neurological sequelae. This is the procedure of choice to make statistical analysis more accurate and less influenced by inter-individual variability, and allowing a dramatic reduction in number of animals deployed.

	References

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusions References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Francesco Migneco Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Migneco, F. Articles by Birla, R. K. Search for Related Content PubMed PubMed Citation Articles by Migneco, F. Articles by Birla, R. K. Related Collections Related Articles