Effectiveness of a new inflatable balloon device for gluing dissected layers in an experimental model of aortic dissection

Abstract

OBJECTIVES:

In the surgical treatment of acute aortic dissection, tissue glues are widely used to reinforce the adhesion between the dissected aortic layers. A new inflatable balloon device was developed to compress the dissected aortic wall during gluing to increase adhesion between the dissected layers. The present study used an ex vivo experimental animal model to test the hypothesis that this device is effective when gluing the true and false channels of dissected aortas.

METHODS:

In the ex vivo experimental model, aortic dissection was simulated surgically on 12 fresh bovine aorta samples. In six samples (group I), the inflatable balloon device was inserted into the aorta to reinforce and fuse the dissected layers during gluing. The other six fresh bovine aortic samples (group II) were compressed between the surgeon’s fingers during gluing. Aortic samples were evaluated and compared macroscopically and histologically.

RESULTS:

In group I, adhesion between the dissected layers was easily achieved during gluing. All false cavities were perfectly closed, with no deleterious effects related to the device. In group II, the adhesion between the dissected layers was not complete and some false cavities remained patent.

CONCLUSIONS:

The inflatable balloon device can increase the adhesive effect of tissue glues via homogenous compression of the dissected aortic layers. In addition, the balloon can prevent distal embolization of the glue.

Acute dissection is the most frequent catastrophic condition involving the aorta and remains the leading cause of death from aortic pathology. Aortic disease is characterized by the separation of the layers of the media by a column of circulating blood with variable proximal and distal extension throughout the entire length of the aorta (1).

Tissue glues are widely used to achieve adhesion between the dissected layers in aortic dissection pathologies. However, during application, some difficulties with their effective use are observed, such as the necessity of circular and longitudinally homogeneous distribution, and rapid application of the glue between the aortic layers. In addition, there is a risk of distal embolization of the glue (2–4).

For these reasons, we have developed a novel cylindrical balloon to enable more efficient, safe and simple use of tissue glue for the treatment of aortic dissection. In the present study, the device was evaluated in an ex vivo experimental model involving fresh bovine aortic samples; the effectiveness of the balloon was also evaluated and compared with the standard technique.

METHODS

The balloon device has a silicone surface. It is designed to be inflatable with air and is adjustable with manometric pressure (Figure 1A). It is cylindrical in shape when inflated. To test the device and compare its efficacy, two different methods were used during the application of glue between the aortic layers. In the present experimental study, cyanoacrylate was used to glue the dissected layers.

Figure 1).

A The balloon was inflated to a pressure of approximately 90 mmHg. B Balloon placement and application of glue in the dissected aorta. C Inflation of the balloon to a pressure of approximately 90 mmHg in the aorta. D A technical drawing of the device

A modified version of the method described by Blanton et al (5) was used to achieve aortic dissection. Initially, a tiny circumferential separation was made in the aorta to penetrate between the tunica media and the tunica intima. A dissection from the incision to all sides (approximately 1 cm in length) was produced circularly using a raspatorium.

The balloon device was tested in an ex vivo experimental model involving fresh bovine aortic samples, which were glued according to two different methods. The animals received humane care in compliance with the European Convention on Animal Care and the entire project was approved by the Institute’s Committee for the Prevention of Cruelty to Animals.

The ex vivo aortas were divided into two groups. In group I, the device was used with glue (n=6). Group II was the control group; in these aortas, the glue was applied with manual pressure between the two aortic layers (n=6). In group I, the balloon was used on the dissected aortic wall after gluing and inflated at approximately 90 mmHg pressure for 60 s (Figures 1B, 1C). In group II, the cyanoacrylate was applied to the dissected layers and adhesion was achieved after 60 s of pressure applied by the surgeon’s fingers.

After the macroscopic examination, the aorta was fixed in 1% formalin solution, and histological sections were prepared and stained with hematoxylin and eosin.

Statistical analysis

All values are presented as mean ± SD. The measurements were analyzed for comparison using Mann-Whitney-U tests.

RESULTS

Aortic diameters were measured before and after the procedure, and no changes were observed in either group. Aortic diameters measured before the procedure showed no statistically significant difference between the two groups (group I: 3.23±0.05 cm versus group II: 3.22±0.04 cm; P=0.818).

Macroscopic findings

A total of 12 ex vivo bovine aortas were evaluated for dissection continuity based on macroscopic findings. The lengths of the remaining dissected areas were measured 1 h after application in both groups.

In group I, all of the false channels were entirely closed by glue and dissection was scarcely observed between the layers. Complete and homogeneous adhesion of the two layers was obtained without tears in the layers (Figure 2A). In contrast, in the control group, some of the false channels remained patent; their mean length was approximately 0.77±0.24 cm (P=0.002) (Figure 2B).

Figure 2).

A In all aorta samples in group I (device group), the false channels were entirely closed by glue and dissection was scarcely observed between the layers (arrow). B In group II (the control group), the dissected areas were assessed with macroscopic observation (arrow)

Microscopic findings

Microscopic examination revealed a homogeneous and compact distribution of glue in group I (Figure 3A). The glue accumulations were observed in a regular line within these layers. In group II, an irregular distribution of glue and wider dissected areas were observed between the layers (Figure 3B).

Figure 3).

A In group I (device group), microscopic examination showed homogeneous and compact distribution of glue. Accumulation of excess glue was observed in a regular line within the layers. B In group II (the control group), irregular distribution of glue and wider dissected areas were observed between the layers

DISCUSSION

In the present study, the dissected aorta was easily reconstructed using the inflatable balloon device. By applying this method, the results of the macroscopic and light microscopic evaluation for the use of this device in conjunction with tissue glue demonstrated effective adhesion within the dissected aortic layers. This balloon compressed the glued aorta without deforming it.

The use of biological glues has simplified surgical treatment of aortic dissection and has greatly improved patient outcomes (6,7). The tissue glue used most commonly is composed of gelatin, resorcinol, cyanoacrylate and formalin (8). It is applied to the dissected aortic wall with moderate pressure and, within 5 min, firm adhesion is achieved.

However, some difficulties may occur during the use of tissue adhesives. These difficulties include the risk of distal and coronary embolization of glues, immediate application requirement due to rapid polymerization of the glue, inadequate equal pressure applied to the entire area of the dissected aorta with instruments such as forceps or manual manoeuvring, and lack of homogeneous distribution of the tissue adhesives.

Different methods have been used to apply pressure to the dissected aortic wall during gluing. Compression using the fingers is the most commonly used method for gluing. Furthermore, to apply pressure to the dissected aortic wall after gluing, surgeons have used a variety of instruments, including balloon catheters, Hegar dilators, modified clamps and modified clips (9,10).

When the glue is applied between the two aortic layers and pressure is applied by the surgeon’s fingers, irregular distribution of glue can occur, thereby preventing complete circumferential adhesion of the dissected layers. In our study, the mean length of the false channels remaining patent as a result of compression by the fingers was 0.77 cm. Conversely, in the balloon group, all of the false channels were entirely closed by glue and dissection was scarcely observed between the layers.

In the present experimental study, the implementation of equal pressure in a circular manner by the inflatable balloon device may be an advantage for the homogeneous distribution of glue within the aortic layers. Thus, firm adhesion between the dissected layers can be achieved.

Instances of distal embolization, such as to coronary, brain and femoral arteries, after the use of glue have been reported in the literature (2–4). Therefore, inflation of the balloon in the aorta can prevent distal embolization of the glue.

There are two limitations of the present study that warrant consideration. First, the present study used healthy aortas, whereas true aortic dissection involves a pathology of some type. Therefore, gluing of the aorta likely depends on many factors including the presence of clot(s) in the false lumen and intramural hematoma, and aortic wall thickness and nature of the dissection (ie, acute, subacute or chronic) – pathologies that were absent in our experimental model. Second, the balloon device is designed only for use in the management of aortic entry tears and cannot be used for re-entry tears; however, repair of re-entry tears commonly involves endovascular methods and stent-graft deployment.

In conclusion, the simplicity and speed of the procedure enables more consistent application of the glue and stronger adhesion between the aortic layers, creating equal pressure on all layers of the aorta. Moreover, the simple use of the glue, as described, avoids embolization of the distal branch via the true lumen while maintaining the advantages of uniform and homogenous distribution of the glue between the aortic layers.