Published online before print December 21, 2005, 10.1148/radiol.2382042182
(Radiology 2005;238:719.)
A more recent version of this article appeared on December 1, 2005
© RSNA, 2005
Subxiphoid Access to Normal Pericardium with Micropuncture Set: Technical Feasibility Study in Pigs1
Fei Sun, MD,
Francisco M. Sánchez, DVM, PhD,
Verónica Crisóstomo, DVM, PhD,
Laura Luis, DVM, PhD,
Jesús Usón, DVM, PhD and
Manuel Maynar, MD, PhD
1 From the Center for Minimally Invasive Surgery, Campus Universitario, Avenida de la Universidad, s/n, 10071 Cáceres, Spain. Received December 23, 2004; revision requested February 23, 2005; revision received February 28; accepted March 15; final version accepted April 18.
Address correspondence to F.S. (e-mail: feisun{at}ccmi.es).
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ABSTRACT
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This study was performed with approval from the ethics committee for animal research of the local government. The purpose of the study was to evaluate the technical feasibility of a technique for subxiphoid access to the normal pericardial space with a micropuncture set in 10 large white pigs. With fluoroscopic guidance, a fine needle was inserted through a subxiphoid approach into the anterior mediastinal space to puncture the pericardium, and a micropuncture set was placed in the pericardial space successfully in all animals without complications. Necropsy at 24 hours did not reveal hemomediastinum, hemopericardium, or laceration of the pericardium. Results of the experiments in animals indicated that the technique was feasible and safe.
© RSNA, 2005
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INTRODUCTION
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With intrapericardial delivery of therapeutic agents, one can use the pericardial space as a reservoir where the administered agents may directly act on the diseased myocardium, coronary arteries, autonomic nerves, and conducting tissue with fairly high local drug concentration and prolonged contact time, while toxic reactions and side effects encountered with intravenous or intraarterial administration can be minimized or eliminated (1). By means of the intrapericardial approach, hypothermia therapy and angiogenic therapy for acute and chronic coronary ischemia and antiarrhythmic therapy have been tested in experimental animals. Results of these tests appear encouraging and indicate a great potential in human application (2–6). Performance of the intrapericardial treatments requires a safe and practicable minimally invasive technique to access the normal pericardium. This poses a technical challenge to interventionists because of the potential damage to the heart and coronary artery and the underlying small normal pericardial space. On the other hand, it also offers an opportunity to strengthen the effect of interventional techniques on clinical practice.
Several approaches to the normal pericardial space that do not rely on thoracotomy have been described, and these include transatrial (7,8), transventricular (9), and subxiphoid access with a device for percutaneous subxiphoid access to the normal pericardium (PerDucer; Comedicus, Columbia Heights, Minn) (10,11) and a blunt-tip needle device (12,13). The purpose of our study was to evaluate the technical feasibility of a technique for subxiphoid access to the normal pericardial space by using a micropuncture set in pigs.
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MATERIALS AND METHODS
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Animals
Ten adult large white pigs, of either sex, with a body weight of 47.2–55.6 kg were used in this study. Animal care and all experimental procedures were performed in accordance with guidelines of the European Communities Council Directive no. 86/609/EEC. Protocols were approved by the ethics committee for animal research of the local government.
Device Description
Percutaneous needle.—We used a 21-gauge 15-cm-long two-part trocar needle with a blunt-tip cannula and an inner stylet (Accustick; Boston Scientific, Boston, Mass), which is designed to reduce tissue trauma.
Microwire.—We used a 0.018-inch 40-cm-long extrastiff guidewire with a platinum tip (Accustick; Boston Scientific). The extra stiff part of the guidewire may offer an effective support to facilitate placement of the dilator or catheter in procedures for percutaneous access; extreme softness and flexibility and high radiopacity of the platinum tip make the guidewire easy to control and increase the safety of percutaneous procedures.
Micropuncture introducer set.—The micropuncture introducer set is composed of an inner catheter matched with the 0.018-inch guidewire and an outer 4-F 10-cm-long catheter matched with a 0.035-inch guidewire (Micropuncture; Wilham Cook Europe, Bjaeverskov, Denmark). The coaxial catheter pair is designed for replacing a microguidewire with a regular guidewire.
Procedure
After the pigs were fasted for 24 hours, each pig was intramuscularly premedicated with 0.1 mg per kilogram of body weight of diazepam, 10 mg/kg of ketamine, and 0.01 mg/kg of atropine. Intravenous hydration with normal saline was established by means of catheterization of the auricular vein with 18–22-gauge needles (Abbocath; Abbott Ireland, Sligo, Ireland) and was maintained during procedures. Induction of anesthesia was performed intravenously with 2 mg/kg of propofol. After the pig was endotracheally intubated, it was connected to a system for anesthesia (Ohmeda Excel 210; Ohmeda, Madison, Wis) and a mechanical ventilator (Ohmeda 7800; Ohmeda). Anesthesia was maintained with 2.0%–2.5% halothane, and blood pressure, electrocardiogram, O2 saturation, and end-tidal CO2 were monitored closely throughout the procedure. The pigs were fixed on the operating table in the supine position with cranial and caudal extension of the limbs. Amoxicillin clavulanate (Synulox; Pfizer, New York, NY) at a dose of 0.15 mL/kg was administered intramuscularly to the pigs. The thorax and upper abdomen were shaved and draped in a sterile fashion.
The skin entry site was defined approximately 1 cm below the xiphoid process in the upper abdominal midline where a small stab incision was made (F.S.). With fluoroscopic guidance (BV300; Philips, the Netherlands) in the lateral projection, a 21-gauge two-part trocar needle was inserted subcutaneously and was carefully advanced along the posterior surface of the sternum into the anterior mediastinal space. The angle between the needle and the anterior abdominal wall was kept at 10°–15°. When the tip of the needle was inside the anterior mediastinum, the hub of the needle moved in the same fashion as the abdominal wall moved with respiration. The needle was gently advanced with its tip oriented toward the heart apex (Fig 1). Immediately a resistance was felt, and the needle was fixed and left in place. When the tip of the needle punctured the pericardium and myocardium, the hub of the needle moved simultaneously with heartbeats. The stylet of the needle was removed, and a 2-mL syringe was connected to the cannula of the needle. Aspiration was performed so that the desired position of the tip of the needle could be confirmed if no blood or air was aspirated out. The syringe was then removed, and a microguidewire was inserted through the needle cannula. The hub of the needle was held gently while the guidewire was advanced. When the leading end of the guidewire reached the tip of the needle cannula, the guidewire was slowly and continuously twisted and pushed until the floppy tip of the guidewire entered the pericardial space (Fig 2). If the guidewire met resistance and could not be pushed out of the cannula tip into the pericardial space, the needle was gently pulled out about 1 mm and the guidewire was manipulated in the same fashion (twisted and pushed).
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Figure 1: Lateral fluoroscopic image shows that the apex of the heart was punctured, with an angle of 10°–15° between the needle and the anterior abdominal wall.
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Figure 2: Lateral fluoroscopic image shows that, after gentle twisting and advancement of the guidewire, the floppy tip of the guidewire sprang into the pericardial space.
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After removal of the needle cannula, fluoroscopy was performed in various projections to ensure that the guidewire was placed along the silhouette of the heart (Fig 3). To facilitate placement of the catheter through the anterior thoracic wall, a 5- or 6-F dilator was used for dilation. Then, a coaxial catheter pair from the micropuncture set was advanced along the microguidewire. From the coaxial catheter pair, 10 mL of contrast agent (Urografin 76%; Schering, Berlin, Germany) diluted with saline was injected to document the presence of the catheter inside the pericardial space with fluoroscopy (Fig 4). The micropuncture set was removed, and chest fluoroscopy was performed to inspect the area for pneumothorax. The animal was allowed to recover from anesthesia.
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Figure 3a: Fluoroscopic images demonstrate that the guidewire is inside the silhouette of the heart on (a) posteroanterior and (b) lateral views.
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Figure 3b: Fluoroscopic images demonstrate that the guidewire is inside the silhouette of the heart on (a) posteroanterior and (b) lateral views.
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Figure 4a: Fluoroscopic images obtained after injection of contrast agent suggest success of the procedure, without leakage of the contrast agent outside of the pericardial space on (a) posteroanterior and (b) lateral views.
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Figure 4b: Fluoroscopic images obtained after injection of contrast agent suggest success of the procedure, without leakage of the contrast agent outside of the pericardial space on (a) posteroanterior and (b) lateral views.
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Follow-up
Twenty-four hours after the procedure, the animal was anesthetized by using the same protocol as was used for the procedure. Chest fluoroscopy was performed to check for pneumothorax (F.S.). The animals were then sacrificed with an intravenous injection of potassium chloride solution. Necropsy was performed (F.S., V.C.) to inspect the area for hemomediastinum, hemopericardium, and laceration of the pericardium to evaluate the safety of the procedure.
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RESULTS
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Technical success was obtained in all animals. The procedures—from the time we made the skin incision to the time we placed the micropuncture set into the pericardial space—were completed within 20 minutes in the first two animals and in 10 minutes in the remaining ones. There were no hemodynamic or electrocardiographic changes during or after the procedure, compared with the status before the procedure, in any animals. During the procedure, mean heart rate, O2 saturation, and end-tidal CO2 were in the normal ranges, which were 90–107 beats per minute, 95%–100%, and 35–40 mm Hg, respectively, without substantial changes observed. Pneumothorax was not evident in any animals during the procedures or at 24 hours afterward. At necropsy, the puncture site at the pericardium was identified as a dotlike defect of about 1 mm in diameter, where no laceration of the pericardium was observed. Hemomediastinum or hemopericardium was not noted in any animals.
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DISCUSSION
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We developed a percutaneous technique to access normal pericardial space by means of a fine sharp needle and a micropuncture set. The strategy of the technique is to obtain access to the normal pericardial space by using a fine needle and a microwire and to introduce a micropuncture set, with which a 0.035-inch guidewire and a regular infusion catheter can be exchanged for subsequent therapeutic purposes. During the procedure, the crucial step is to introduce the micro guidewire inside the pericardium. In the achievement of this end, we observed four technical key points, which are summarized next.
First, the entry site of the pericardium should be at the heart apex, with the bevel of the needle tip maintained upward and the orientation of the needle kept at an angle of 10°–15° in relation to the anterior abdominal wall.
Second, with the guidance of fluoroscopy in the lateral projection, the needle should be gently advanced within the anterior mediastinal space until a faint resistance is felt with the fingers. This generally indicates that the tip of the needle is just puncturing the pericardium and touching the myocardium. The other instrumental indicator is the movement of the needle hub in the same fashion as heartbeats; while the tip of the needle is in the mediastinal space, the needle hub moves simply with the abdominal wall in respiration.
Third, before introduction of the guidewire, it is mandatory that aspiration be performed through the puncture needle so that no blood or air is present and, thus, possible complications are avoided.
Fourth, when the leading end of the guidewire is introduced to the tip of the needle, it should be smoothly twisted and pushed to let the guidewire extend out of the needle while one hand is gently holding the needle rather than firmly fixing it. In this way, the tip of the needle can readily be adjusted minimally to facilitate positioning of the guidewire. Typically, the tip of the needle punctures at the myocardial surface; hence, when the guidewire is twisted and advanced, the tip of the guidewire is initially stuck at the myocardium. Then the floppy portion of the guidewire becomes bent and eventually slips into the pericardial space. Once the guidewire is successfully placed into the pericardial space, it can always be moved freely along the cardiac silhouette.
The initial results of the study indicate that the technique is feasible and safe for accessing the normal pericardium in pigs. Technical success was obtained in all procedures. Furthermore, the technique appeared to be simple, with a short learning curve; the whole procedure was accomplished within 20 minutes in the initial two animals and within 10 minutes in the other animals. There were no hemodynamic or electrocardiographic changes during or after the procedure, as compared with the status before the procedure. In all animals, no major complications, such as pneumothorax, hemopericardium, or hemomediastinum, were evident either during the procedure or at necropsy at 24 hours afterward.
In the literature, various techniques for approaches to the normal pericardium that do not rely on thoracotomy have been reported. These can be classified as percutaneous subxiphoid access and transvenous access. In comparison with those techniques that were described previously, the technique that we described appears to have numerous advantages from the standpoint of clinical application.
The PerDucer is reported as a device for percutaneous subxiphoid access to the normal pericardium. The technique consists of two major steps: pericardial puncture by means of negative suction with a side-hole bleb chamber and pericardial puncture through the side hole. The technical feasibility and safety have been confirmed in large numbers of animals and in a few clinical trials in patients. According to previous reports, however, use of the PerDucer device for pericardial access usually failed because the pericardial fat pad obstructed the hemispheric side-hole chamber and prevented capture; with a thick and stiff pericardium, or substantial pericardial effusion, negative pressure inside the side-hole chamber could not be sufficiently obtained to capture the pericardium (10,11). In addition, the large profile of the PerDucer requires a 19-F (6.3-mm-diameter) introducer to be placed subcutaneously in the anterior mediastinum. This necessitates a large incision at the skin entry site and produces a substantial invasion in the anterior mediastinum. Insertion of a large dilator or introducer may be severely painful in some patients, so intravenous administration of analgesics has to be applied (11,14). In contrast, our technique has the feature of minimal invasion because we used a 4-F coaxial catheter set (diameter, 1.3 mm).
Another technique for percutaneous subxiphoid access to the normal pericardium was described by Sosa et al (15); in their technique, they used a blunt-tip epidural introducer needle (17-gauge Tuohy needle) in procedures for epicardial mapping and ablation. This technique was subsequently used in animal experiments to evaluate the effectiveness of angiogenic therapy for coronary ischemia (13), as well as in patients for pericardiocentesis (16). In the procedure, a blunt-tip needle is connected with an intraflow infusion system and a pressure transducer. The blunt-tip needle is advanced gently with fluoroscopic guidance and a continuous positive pressure of 20–30 mm Hg. Entry into the pericardial space is indicated by a slight negative pressure, when the saline flow increases through the infusion system. A soft floppy-tip 0.025-inch guidewire is then introduced to the pericardial space, and the needle is exchanged for the pericardial drainage catheter.
Just as with our technique, the device with the blunt-tip needle and associated intraflow infusion system is inexpensive, and the technique appears to be well tolerated. Its safety, however, remains to be evaluated further. Although a blunt-tip needle was used in an attempt to eliminate possible complications, it was reported that, in one of 10 patients, hemopericardium occurred during the procedure and that drainage was required; three other patients developed retrosternal discomfort and pericardial friction rub (12). This may, in part, be attributed to the relatively large bore of the needle (17 gauge). In contrast, the puncture needle we used in the present study had a 21-gauge bore, which appears to be less invasive and safer. Moreover, before the guidewire was introduced, we performed aspiration from the needle to ensure that there would be no damage to the vessel if no blood was aspirated. In our study, no hemopericardium or hemomediastinum was observed in any animals, and this result supported the safety of the technique, although a definite conclusion cannot be reached because this study was based on a limited number of animals.
Pericardial access in the normal heart with a transvenous approach also has been reported. Verrier et al (7) described transatrial access to the normal pericardium in 1998. In their initial experiments in pigs, a 6- or 8-F guiding catheter was introduced from the femoral vein and positioned in the right atrial appendage, through which a custom-fabricated, 21-gauge needle mounted at the tip of a 4-F catheter was inserted to perforate the right atrium. Thereafter, a catheter was placed into the pericardial space with the help of a guidewire. This technique was later simplified by replacing the needle-catheter system with a coaxial infusion wire–microwire device (8).
The technique evaluated in this study has been demonstrated to be feasible in animal experiments; nevertheless, some issues about safety need to be addressed before it is applied in humans. Since a guiding catheter with a coaxial system is used, systemic heparin administration usually is needed. This disturbs the physiologic coagulation mechanism and leads to a potential occurrence of hemopericardium during the procedure. In addition, relative low pressure within the right atrium has been regarded as one factor that is related to safety in healthy subjects, but it could be hazardous in patients with elevated right atrial pressure.
The other technique for transvenous access to normal pericardium with a jugular approach was reported by March et al (9). In the procedure, a 7-F hollow helical-tipped catheter was placed from the jugular vein into the right ventricle to the cardiac apex, with the catheter tip directed inferiorly. The helical tip penetrated the myocardium with a turning maneuver. Although no significant bleeding was revealed in 11 dogs, the technique seems to be far from safe because of the risk of hemopericardium.
Furthermore, both types of transvenous access discussed previously have an inherent drawback whereby they are limited to the bolus administration of drugs in intrapericardial therapy. The technique we developed, however, appears to be more favorable because it has the potential to be used in chronic or repeated delivery of therapeutic agents by means of an indwelling infusion catheter.
Although this technique is designed for access to the normal pericardium and aims at future intrapericardial therapy, especially for coronary ischemia and arrhythmia, it could be used in current clinical practice, which includes application in epicardial mapping, ablation, and diagnostic sampling of fluid. Moreover, it offers an alternative type of access in pericardiocentesis for drainage of effusion and delivery of chemicals in the treatment of pericardial malignancy.
The major limitation of this study was the small sample size of animals. Evaluation of possible subacute or chronic complications, such as delayed hemopericardium, hemomediastinum, and pericarditis, remains to be performed. The pathologic evidence in regard to the hypothesized minimal damage to the myocardium at the puncture site is yet absent.
In conclusion, we developed a technique for subxiphoid access to normal pericardium by using a micropuncture set. Although the initial results were favorable in the evaluation of the feasibility and safety of the technique, further study is needed in a large animal population, as well as in clinical trials.
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ACKNOWLEDGMENTS
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We thank Professor Ho-Young Song for helpful revision of the original manuscript.
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FOOTNOTES
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Authors stated no financial relationship to disclose.
Author contributions: Guarantor of integrity of entire study, F.S.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, F.S.; experimental studies, all authors; and manuscript editing, F.S., M.M.
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References
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ABSTRACT
INTRODUCTION
