Transatrial access to the normal pericardial space: a novel approach for diagnostic sampling, pericardiocentesis, and therapeutic interventions

Feasibility of Transatrial Access for Epicardial Ablation: Evaluation of 2 Different Techniques in Swine

BACKGROUND

The subxiphoid pericardial access is technically difficult and has a considerable rate of complications, thus transatrial access may be an alternative.

OBJECTIVES

This study sought to assess the feasibility and safety of this strategy regarding periprocedural period and after 1-week follow-up.

METHODS

The investigators performed epicardial mapping through transatrial puncture in 20 swine. Animals were divided into group A, in which aspiration of the sheath was performed to maintain negative pressure after the withdraw of the catheters, and group B, in which a device (Konar-MF VSD Occluder) was delivered to occlude the right atrial appendage perforation. Bleeding was investigated immediately and 1 week after.

RESULTS

Access was safe in 19 of 20 animals (95%) with small amount of bleeding (6.4 ± 6 mL). In group A (n = 10), 1 animal presented hemopericardium right after the puncture. In the other 9, epicardial ablation was performed and 60.0 ± 28.0 mL of blood was aspirated without events. After 1 week, fibrin-hemorrhagic pericarditis was identified in 3 animals. In group B (n = 10), reaching the epicardial surface was possible in all animals. An adequate position of the prosthesis was obtained in 90% (9 of 10). One death occurred in the immediate postoperative period, secondary to pneumothorax. After 1 week, postmortem analysis showed absence of pericardial bleeding and a normal-appearing pericardium in the 8 animals with adequate prosthesis position.

CONCLUSIONS

Transatrial access allows epicardial mapping and ablation. Sheath removal after negative pressure contributes to achieving acute bleeding control but does not prevent its occurrence. The use of the device prevents bleeding and hemorrhagic pericarditis.

Novel dry pericardiocentesis: Transvenous puncture of the right ventricle with the back end of a 0.014-inch PTCA guidewire and a 1.8 Fr microcatheter

Background

Dry transthoracic pericardiocentesis is challenging and carries the risk of right ventricle (RV) or coronary artery injury. The RV can usually control bleeding automatically. For example, most perforations of the RV caused by pacemaker leads are treated without open surgery. Thus, we performed a transvenous puncture of the RV for dry pericardiocentesis with the back end of a 0.014-inch percutaneous transluminal coronary angioplasty (PTCA) guidewire and a 1.8 Fr microcatheter.

Methods

The back end of a 0.014-inch PTCA guidewire within a 1.8 Fr microcatheter was used to transvenously punctured through the middle of the acute margin of the RV into the pericardial space in 12 Yorkshire swine and 5 beagles. PTCA balloons of different diameters were used to dilate the puncture holes for 15 min under anticoagulation in all the animals to assess the ability of the RV to control the bleeding. Then, for 3 days, the puncture hole was dilated by a 6 Fr catheter in 9 swine and 5 dogs.

Results

The puncture was successful in all the animals. After withdrawal of the 2.5-mm balloon or the 6 Fr catheter, none of the animals exhibited pericardial effusion, as observed by echocardiography. There was no sustained ventricular arrhythmia or other complications. All the animals survived.

Conclusion

Transvenous puncture of the right ventricle with the back end of a 0.014-inch PTCA guidewire and 1.8 Fr microcatheter may be feasible and have a good safety margin.

Access routes, devices and guidance methods for intrapericardial delivery in cardiac conditions

Drug deposition into the intrapericardial space is favourable for achieving localised effects and targeted cardiac delivery owing to its proximity to the myocardium as well as facilitating optimised pharmacokinetic profiles and a reduction in systemic side effects. Access to the pericardium requires invasive procedures but the risks associated with this have been reduced with technological advances, such as combining transatrial and subxiphoid access with different guidance methods. A variety of introducer devices, ranging from needles to loop-catheters, have also been developed and validated in pre-clinical studies investigating intrapericardial delivery of therapeutic agents. Access techniques are generally well-tolerated, self-limiting and safe, although some rare complications associated with certain approaches have been reported. This review covers these access techniques and how they have been applied to the delivery of drugs, cells, and biologicals, demonstrating the potential of intrapericardial delivery for treatments in cardiac arrhythmia, vascular damage, and myocardial infarction.

Techniques for Percutaneous Access

Percutaneous epicardial access continues to have a growing role within cardiac electrophysiology. The classic approach has typically been with a Tuohy needle via a subxiphoid approach guided by fluoroscopic landmarks and tactile feedback. Recent developments have highlighted the role of the micropuncture needle, electroanatomic mapping, and real-time pressure sensors to reduce complications. Further, different access sites, such as the right atrial appendage, have been described and may offer a novel approach to percutaneous epicardial access. In addition, future directions of percutaneous access may involve direct visualization, near-field impedance monitoring, and real-time virtual imaging.

Percutaneous Epicardial Approach to Catheter Ablation of Cardiac Arrhythmias

Since their introduction >2 decades ago, percutaneous catheter-based epicardial mapping and ablation have become widely adopted by cardiac electrophysiologists around the world. Although epicardial mapping has been used for catheter ablation of a wide variety of cardiac arrhythmias, its most common use is for ablation of intramural and subepicardial substrates that give rise to ventricular tachycardia, particularly in patients with nonischemic cardiomyopathy. As such, the subxiphoid percutaneous epicardial approach has emerged as an important adjunct, and, in some cases, is the preferred strategy in this regard. This review discusses the rationale and indications for epicardial catheter mapping and/or ablation. This paper also reviews the prevalence of epicardial arrhythmias and their electrocardiographic criteria. In addition, it examines the anatomy of the pericardium and commonly used epicardial access techniques, as well as the optimal methodologies for epicardial mapping and ablation and the impact of epicardial fat. Finally, this review discusses the potential of the various complications associated with the percutaneous epicardial approach, in addition to patient-specific risk factors, and potential strategies to mitigate the risk of complications.

Technologies for intrapericardial delivery of therapeutics and cells

The pericardium, which surrounds the heart, provides a unique enclosed volume and a site for the delivery of agents to the heart and coronary arteries. While strategies for targeting the delivery of therapeutics to the heart are lacking, various technologies and nanodelivery approaches are emerging as promising methods for site specific delivery to increase therapeutic myocardial retention, efficacy, and bioactivity, while decreasing undesired systemic effects. Here, we provide a literature review of various approaches for intrapericardial delivery of agents. Emphasis is given to sustained delivery approaches (pumps and catheters) and localized release (patches, drug eluting stents, and support devices and meshes). Further, minimally invasive access techniques, pericardial access devices, pericardial washout and fluid analysis, as well as therapeutic and cell delivery vehicles are presented. Finally, several promising new therapeutic targets to treat heart diseases are highlighted.

Pericardial Effusion and Compressive Disorders of the Heart: Influence of New Technology on Unraveling its Pathophysiology and Hemodynamics

Constrictive pericarditis and cardiac tamponade cause severe diastolic dysfunction, but do not depress systolic function until the agonal state has been reached. Multimodality cardiovascular imaging has brought the nuances of pericardial disease to the domain of the practicing cardiologist. This introduction is a revised article originally written by the late Dr Shabetai for a pericardial diseases textbook which was not published. He was the editor of previous Pericardial Diseases issue for Cardiology Clinics in the 1980s, it is most appropriate to begin our issue with his insights. The remaining articles describe advances in diagnosis and management, focusing on clinically important aspects of pericardial diseases.

Intentional Right Atrial Exit and Carbon Dioxide Insufflation to Facilitate Subxiphoid Needle Entry Into the Empty Pericardial Space: First Human Experience

OBJECTIVES

The purpose of this study was to test whether a microcatheter can safely be advanced across the right atrial appendage to access the pericardium and then withdrawn despite subsequent high-intensity anticoagulation. We also tested whether transatrial pericardial insufflation of carbon dioxide (CO₂) would enhance the safety of subxiphoid needle access to the empty pericardium by separating the heart from the anterior pericardium.

BACKGROUND

Subxiphoid needle access to the empty pericardium, required for left atrial suture ligation and epicardial ablation for rhythm disorders, risks myocardial or coronary laceration.

METHODS

A catheter from the femoral vein engaged the right atrial appendage for angiographic confirmation of position. Through that catheter, the back end of a 0.014- or 0.018-inch guidewire crossed the right atrial wall to enter the pericardium and delivered a 2.4-F microcatheter. CO₂ 1 to 2 ml/kg was insufflated into the pericardium immediately before subxiphoid needle access under lateral projection fluoroscopy. Thirteen patients undergoing subxiphoid suture ligation of the left atrial appendage consented to participate in this research protocol.

RESULTS

Right atrial exit succeeded in 11 subjects (85%) and failed uneventfully in 2 subjects. CO₂ insufflation of 96 ± 22 ml achieved 12 ± 4 mm separation of the anterior pericardium from the myocardial wall, allowed rapid and successful subxiphoid anterior needle and guidewire entry in all 11 subjects, and did not have any evident hemodynamic effects. The immediate pericardial aspirate was serous in all but 1 subject.

CONCLUSIONS

We report the first human intentional transatrial exit procedure. Transatrial microcatheter access to the pericardium can be achieved safely. Pericardial insufflation with CO₂ makes subxiphoid access to the empty pericardium rapid and safe. Although our clinical experience to date remains small, with further experience, this approach may prevent the life-threatening complications of "dry" subxiphoid pericardial access.

Intentional right atrial exit for microcatheter infusion of pericardial carbon dioxide or iodinated contrast to facilitate sub-xiphoid access

OBJECTIVES

We test the safety of transatrial pericardial access using small catheters, infusion of carbon dioxide (CO2 ) or iodinated contrast to facilitate sub-xiphoid access, and catheter withdrawal under full anticoagulation.

BACKGROUND

Sub-xiphoid pericardial access is required for electrophysiological and structural heart interventions. If present, an effusion protects the heart from needle injury by separating the myocardium from the pericardium. However, if the pericardium is 'dry' then there is a significant risk of right ventricle or coronary artery laceration caused by the heart beating against the needle tip. Intentional right atrial exit is an alternative pericardial access route, through which contrast media could be infused to separate pericardial layers.

METHODS

Transatrial pericardial access was obtained in a total of 30 Yorkshire swine using 4Fr or 2.8Fr catheters. In 16 animals, transatrial catheters were withdrawn under anticoagulation and MRI was performed to monitor for pericardial hemorrhage. In 14 animals, iodinated contrast or CO2 was infused before sub-xiphoid access was obtained.

RESULTS

Small effusions (mean 18.5 ml) were observed after 4Fr (1.3 mm outer-diameter) but not after 2.8Fr (0.9 mm outer-diameter) transatrial catheter withdrawal despite full anticoagulation (mean activated clotting time 383 sec), with no hemodynamic compromise. Pericardial CO2 resorbed spontaneously within 15 min.

CONCLUSIONS

Intentional transatrial exit into the pericardium using small catheters is safe and permits infusion of CO2 or iodinated contrast to separate pericardial layers and facilitate sub-xiphoid access. This reduces the risk of right ventricular or coronary artery laceration. 2.8Fr transatrial catheter withdrawal does not cause any pericardial hemorrhage, even under full anticoagulation.

Transatrial intrapericardial tricuspid annuloplasty

OBJECTIVES

This study sought to demonstrate transcatheter deployment of a circumferential device within the pericardial space to modify tricuspid annular dimensions interactively and to reduce functional tricuspid regurgitation (TR) in swine.

BACKGROUND

Functional TR is common and is associated with increased morbidity and mortality. There are no reported transcatheter tricuspid valve repairs. We describe a transcatheter extracardiac tricuspid annuloplasty device positioned in the pericardial space and delivered by puncture through the right atrial appendage. We demonstrate acute and chronic feasibility in swine.

METHODS

Transatrial intrapericardial tricuspid annuloplasty (TRAIPTA) was performed in 16 Yorkshire swine, including 4 with functional TR. Invasive hemodynamics and cardiac magnetic resonance imaging (MRI) were performed at baseline, immediately after annuloplasty and at follow-up.

RESULTS

Pericardial access via a right atrial appendage puncture was uncomplicated. In 9 naïve animals, tricuspid septal-lateral and anteroposterior dimensions, the annular area and perimeter, were reduced by 49%, 31%, 59%, and 24% (p < 0.001), respectively. Tricuspid leaflet coaptation length was increased by 53% (p < 0.001). Tricuspid geometric changes were maintained after 9.7 days (range, 7 to 14 days). Small effusions (mean, 46 ml) were observed immediately post-procedure but resolved completely at follow-up. In 4 animals with functional TR, severity of regurgitation by intracardiac echocardiography was reduced.

CONCLUSIONS

Transatrial intrapericardial tricuspid annuloplasty is a transcatheter extracardiac tricuspid valve repair performed by exiting the heart from within via a transatrial puncture. The geometry of the tricuspid annulus can interactively be modified to reduce severity of functional TR in an animal model.

Myocardial drug distribution generated from local epicardial application: potential impact of cardiac capillary perfusion in a swine model using epinephrine

Prior studies in small mammals have shown that local epicardial application of inotropic compounds drives myocardial contractility without systemic side effects. Myocardial capillary blood flow, however, may be more significant in larger species than in small animals. We hypothesized that bulk perfusion in capillary beds of the large mammalian heart not only enhances drug distribution after local release, but also clears more drug from the tissue target than in small animals. Epicardial (EC) drug releasing systems were used to apply epinephrine to the anterior surface of the left heart of swine in either point-sourced or distributed configurations. Following local application or intravenous (IV) infusion at the same dose rates, hemodynamic responses, epinephrine levels in the coronary sinus and systemic circulation, and drug deposition across the ventricular wall, around the circumference and down the axis, were measured. EC delivery via point-source release generated transmural epinephrine gradients directly beneath the site of application extending into the middle third of the myocardial thickness. Gradients in drug deposition were also observed down the length of the heart and around the circumference toward the lateral wall, but not the interventricular septum. These gradients extended further than might be predicted from simple diffusion. The circumferential distribution following local epinephrine delivery from a distributed source to the entire anterior wall drove drug toward the inferior wall, further than with point-source release, but again, not to the septum. This augmented drug distribution away from the release source, down the axis of the left ventricle, and selectively toward the left heart follows the direction of capillary perfusion away from the anterior descending and circumflex arteries, suggesting a role for the coronary circulation in determining local drug deposition and clearance. The dominant role of the coronary vasculature is further suggested by the elevated drug levels in the coronary sinus effluent. Indeed, plasma levels, hemodynamic responses, and myocardial deposition remote from the point of release were similar following local EC or IV delivery. Therefore, the coronary vasculature shapes the pharmacokinetics of local myocardial delivery of small catecholamine drugs in large animal models. Optimal design of epicardial drug delivery systems must consider the underlying bulk capillary perfusion currents within the tissue to deliver drug to tissue targets and may favor therapeutic molecules with better potential retention in myocardial tissue.

A Novel Amiodarone-Eluting Biological Glue for Reducing Postoperative Atrial Fibrillation

Objective:

Postoperative atrial fibrillation (POAF) is the most common complication after cardiac surgery, leading to increased morbidity and mortality. The aim of this preliminary study was to evaluate a novel drug delivery system for local release of amiodarone.

Methods:

In the current prospective study, 9 goats underwent attachment of right atrial (RA) epicardial electrodes. Alginate-based glue with amiodarone was applied to the RA of the treatment groups. Rapid atrial response (RAR) to burst pacing was assessed before application and in the third postoperative day (POD3). Average RAR frequency was defined as the average percentage of inductions resulting in RAR per animal. Myocardial and extracardiac tissue amiodarone concentrations were analyzed.

Results:

Differences in RAR proportions between baseline and POD3 were greater in the treatment group versus the control group ( P = .034). Average RAR frequency was reduced by 34% in the treatment group (baseline: 65%; POD3: 31%), while it was increased by 11.3% in the control (baseline:43.8%; POD3: 55%). The treatment group demonstrated a greater proportion of animals meeting the success criterion of net percentage reduction in RAR frequency greater than 25% ( P = .047). The average amount of total amiodarone detected in the RA was 104.4 ± 28.9 µg; the transmural concentration was linearly distributed ( P < .0001). Extracardiac tissue concentrations were below the detection level.

Conclusions:

Local alginate-based amiodarone delivery demonstrated an RAR frequency reduction of clinical importance in response to burst pacing. The electrophysiological response was achieved while maintaining below-detection systemic drug levels. Current findings may point to the system’s future applicability in reducing POAF risk in humans.

Real-time cardiovascular magnetic resonance subxiphoid pericardial access and pericardiocentesis using off-the-shelf devices in swine

BACKGROUND

Needle access or drainage of pericardial effusion, especially when small, entails risk of bystander tissue injury or operator uncertainty about proposed trajectories. Cardiovascular magnetic resonance (CMR) might allow enhanced imaging guidance.

METHODS AND RESULTS

We used real-time CMR to guide subxiphoid pericardial access in naïve swine using commercial 18G titanium puncture needles, which were exchanged for pericardial catheters. To test the value of CMR needle pericardiocentesis, we also created intentional pericardial effusions of a range of volumes, via a separate transvenous-transatrial catheter. We performed these procedures in 12 animals.

CONCLUSIONS

CMR guided pericardiocentesis is attractive because the large field of view and soft tissue imaging depict global anatomic context in arbitrary planes, and allow the operator to plan trajectories that limit inadvertent bystander tissue injury. More important, CMR provides continuous visualization of the needle and target throughout the procedure. Using even passive needle devices, CMR enabled rapid pericardial needle access and drainage. We believe this experience supports clinical testing of real-time CMR guided needle access or drainage of the pericardial space. We suspect this would be especially helpful in "difficult" pericardial access, for example, in distorted thoracic anatomy or loculated effusion.

High concentrations of drug in target tissues following local controlled release are utilized for both drug distribution and biologic effect: an example with epicardial inotropic drug delivery

Local drug delivery preferentially loads target tissues with a concentration gradient from the surface or point of release that tapers down to more distant sites. Drug that diffuses down this gradient must be in unbound form, but such drug can only elicit a biologic effect through receptor interactions. Drug excess loads tissues, increasing gradients and driving penetration, but with limited added biological response. We examined the hypothesis that local application reduces dramatically systemic circulating drug levels but leads to significantly higher tissue drug concentration than might be needed with systemic infusion in a rat model of local epicardial inotropic therapy. Epinephrine was infused systemically or released locally to the anterior wall of the heart using a novel polymeric platform that provides steady, sustained release over a range of precise doses. Epinephrine tissue concentration, upregulation of cAMP, and global left ventricular response were measured at equivalent doses and at doses equally effective in raising indices of contractility. The contractile stimulation by epinephrine was linked to drug tissue levels and commensurate cAMP upregulation for IV systemic infusion, but not with local epicardial delivery. Though cAMP was a powerful predictor of contractility with local application, tissue epinephrine levels were high and variable--only a small fraction of the deposited epinephrine was utilized in second messenger signaling and biologic effect. The remainder of deposited drug was likely used in diffusive transport and distribution. Systemic side effects were far more profound with IV infusion which, though it increased contractility, also induced tachycardia and loss of systemic vascular resistance, which were not seen with local application. Local epicardial inotropic delivery illustrates then a paradigm of how target tissues differentially handle and utilize drug compared to systemic infusion.

Local epicardial inotropic drug delivery allows targeted pharmacologic intervention with preservation of myocardial loading conditions

Local myocardial application of inotropes may allow the study of pharmacologically augmented central myocardial contraction in the absence of confounding peripheral vasodilating effects and alterations in heart loading conditions. Novel alginate epicardial (EC) drug releasing platforms were used to deliver dobutamine to the left ventricle of rats. Pressure-volume analyses indicated that although both local and systemic intravenous (i.v.) use of inotropic drugs increase stroke volume and contractility, systemic infusion does so through heart unloading. Conversely, EC application preserves heart load and systemic blood pressure. EC dobutamine increased indices of contractility with minimal rise in heart rate and lower reduction in systemic vascular resistance than i.v. infusion. Drug sampling showed that dobutamine concentration was 650-fold higher in the anterior wall than in the inferior wall. The plasma dobutamine concentration with local delivery was about half as much as with systemic infusion. These data suggest that inotropic EC delivery has a localized effect and augments myocardial contraction by different mechanisms than systemic infusion, with far fewer side effects. These studies demonstrate a pharmacologic paradigm that may improve heart function without interference from effects on the vasculature, alterations in heart loading, and may ultimately improve the health of heart failure patients.

Pericardial approach for cardiac therapies: old practice with new ideas

Treatment of cardiac disease via the epicardium fell under the domain of cardiac surgery due to the need for an open thoracotomy. Since an open thoracotomy is invasive in nature and has the potential for complications, a minimally invasive and percutaneous approach would be more attractive for suitable patients. The recent success of epicardial ablation of refractory arrhythmia via the percutaneous pericardial approach has increased the potential for delivery of epicardial therapies. Epicardial ablation has increased the success and safety since anti-coagulation and transseptal catheterization for left atrial arrhythmias is not required. The pericardial space has also been used to deliver therapy for several cardiac diseases. There are reports on successful delivery of drugs and their efficacy. Even though there was a wide range of efficacies reported in those studies, the reported complication rates are strikingly low, which suggests that direct delivery of drugs to the epicardium via the pericardial space is safe. Furthermore, recent animal studies have supported the feasibility of epicardial delivery of biological agents, including genes, cells, and even genetically engineered tissue for therapeutic purposes. In conclusion, percutaneous pericardial cannulation of closed pericardial space can play a significant role in providing non-surgical therapy for cardiovascular diseases. However, it requires skills and operator experiences. Therefore, there is need to further develop new tools, safer techniques, and effective procedure environment before generalizing this procedure.

The Pericardial Space: Obtaining Access and an Approach to Fluoroscopic Anatomy

The pericardial space is now increasingly used as a means and vantage point for mapping and ablating various arrhythmias. In this review, present techniques to access the pericardial space are examined and potential improvements over this technique discussed. The authors then examine in detail the regional anatomy of the pericardial space relevant to the major arrhythmias treated in contemporary electrophysiology. In each of these sections, emphasis is placed on anatomic fluoroscopic correlation and avoiding complications that may result.

A transatrial pericardial access: lead placement as proof of concept

A safe, easy, and quick access into the pericardial space may provide a window for diagnostics and therapeutics to the heart. The objective of this study was to provide proof of concept for an engagement and access catheter that allows access to the pericardial space percutaneously. A multilumen catheter was developed to allow navigation and suction fixation to the right atrial appendage/wall in a normal swine model. Advancement through the multilumen catheter using a second catheter with a distal needle tip allows access to the pericardial space without pericardial puncture and advancement of a standard guide wire into the space. Navigation into the pericardial space was undertaken by fluoroscopy alone and was accomplished in 10 swine (5 acute and 5 chronic). As a specific application of this pericardial access method, a pacing lead was implanted on the epicardial surface. Five chronic swine experiments were conducted with successful pacing engagement verified by lead impedance and pacing threshold and sensing. Lead impedance exceeded 1,000 Ω preengagement and dropped by an average of 200 Ω upon implant (769 ± 498 Ω). Pacing thresholds at 0.4 ms ranged from ∼0.5 to 2.1 V acutely (1.03 ± 0.92 V). No cardiac effusion or tamponade was observed in any of the acute or chronic studies. The ability to engage, maintain, and retract the right atrial appendage/wall and to engage an epicardial lead was successfully demonstrated. These findings support the feasibility of safe access into the pericardial space in a normal swine model and warrant further investigations for clinical translation.

Long-term pericardial catheterization is associated with minimum foreign-body response

OBJECTIVES

The goals of this study were to assess the feasibility and to characterize the foreign-body response of a long-term catheter in the pericardium.

BACKGROUND

Long-term access to the normal pericardial space provides opportunities for diagnostic sampling and therapeutic intervention.

METHODS

After thoracotomy, in 7 anesthetized canines, the pericardium was opened and a 5 French silicone vascular access catheter was advanced 10 cm into the pericardial sac toward the apex of the heart. A hydraulic coronary balloon occluder was implanted (N=6). Pericardium was sealed with Prolene suture. Catheters were tunneled to the nape of the neck, attached to a subcutaneous vascular access port, and buried in the fascia. Animals underwent multiple experimental coronary artery occlusions across months. At sacrifice, we assessed the histopathological response of pericardium and epicardium to chronically indwelling silicone catheters.

RESULTS

Post-mortem examinations were performed at 213 days post-operatively (mean, range=96-413, N=6), with one animal maintained for longer-term study. At sacrifice, all catheters were bidirectionally patent and completely mobile in the pericardium without evidence of tissue overgrowth around the intrapericardial segment. Adhesion tissue was found only at the site of catheter entry through the pericardium. Microscopic histopathological examination at catheter entry site, surrounding pericardium, and myocardium revealed minimum chronic inflammation.

CONCLUSIONS

This subcutaneous system provides dependable, chronic access to the normal pericardial space for drug delivery and sampling. The presence of a chronic silicone catheter in the pericardium does not precipitate clinically significant pathologic changes even after repeated ischemic events.

Transauricular Arterial or Venous Access for Cardiovascular Experimental Protocols in Animals

PURPOSE

To describe a safe percutaneous method of transauricular endovascular access in small and large animals that uses basic catheter-based interventional skills and renders surgery and general anesthesia with intubation unnecessary.

MATERIALS AND METHODS

Twenty New Zealand White rabbits and five domestic juvenile swine were used in the experiments. Animals were restrained in the supine position after induction of dissociative anesthesia. Transauricular endovascular access was accomplished by percutaneous catheterization of the auricular artery or vein, roadmap imaging, introduction of a 0.018-inch hydrophilic guide wire, and over-the-wire vascular sheath insertion after serial tract dilations.

RESULTS

Technical success rates were 90% and 100% for intraarterial and endovenous access in the rabbit, respectively, and 100% for both routes in the pig. The largest sheaths inserted were 5 F in the rabbits' aortae, 7 F in the rabbits' venae cavae, 6 F in the pigs' aortae, and 8 F in the pigs' venae cavae. Animal recovery was uneventful, and 48-hour necropsy detected only minor perivascular hematoma in cases of transauricular intraarterial access. Peripheral, intracoronary, intrapulmonary, and intracerebral selective vascular access was safe and feasible. A method of reserving the transauricular endovascular access for future interventions or follow-up by placement of indwelling hydrophilic catheters was also established.

CONCLUSIONS

Transauricular endovascular access is a successful technique for establishing and maintaining intraarterial or endovenous vascular access. It obviates surgical cutdown and sacrifice of the femoral and cervical vessels and might considerably improve and expedite cardiovascular experimental protocols in small and large animals.

Suppression of Calcium-Induced Repolarization Heterogeneity as a Mechanism of Nitroglycerin??s Antiarrhythmic Action

This study examined whether the antifibrillatory action of nitroglycerin (NTG) is attributable to reduction in calcium-induced heterogeneity of repolarization independent of autonomic and coronary vasodilatory influences. The effects of intrapericardial (IPC) NTG on coronary blood flow, contractility, repolarization, and arrhythmia susceptibility were measured in anesthetized pigs (N = 43). Autonomic influences were minimized by vagotomy and beta-adrenergic blockade (metoprolol, 1.25 mg/kg, intravenous). Electrophysiological parameters were tested at 30 min, a time when coronary hemodynamics had returned to baseline. Intracoronary calcium chloride (CaCl2, 50-mg bolus) injection augmented contractility (dP/dt(max), 1760 +/- 144 to 2769 +/- 274 mmHg/s, and following NTG, 1531 +/- 384 to 2138 +/- 242 mmHg/s, P < 0.0002), reflecting increased myocardial intracellular calcium. Calcium increased repolarization heterogeneity (interlead precordial T-wave heterogeneity, 95 +/- 15 to 264 +/- 33 microV, P < 0.006; T(peak)-T(end), an index of transmural dispersion of repolarization, 37 +/- 3 to 76 +/- 6 ms, P < 0.05) and lowered repetitive extrasystole threshold (RET; 24 +/- 2 to 13 +/- 1 mA, and following NTG, 32 +/- 4 to 18 +/- 1 mA, P < 0.0001). IPC NTG raised the RET from baseline by 33% and blunted calcium-induced contractility (dP/dt(max) by 23%, P < 0.05), repolarization changes (T-wave heterogeneity by 24%, P < 0.006; T(peak)-T(end) by 18%, P = 0.04), and arrhythmia vulnerability (RET by 39%, P < 0.003). Thus, the capacity of NTG to suppress calcium-induced repolarization heterogeneity is an important mechanism of its antiarrhythmic action, which is independent of autonomic and vasodilatory actions.

Subxiphoid access to normal pericardium with micropuncture set: technical feasibility study in pigs

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.

Transvenous access to the pericardial space: an approach to epicardial lead implantation for cardiac resynchronization therapy

BACKGROUND

Percutaneous access to the pericardial space (PS) may be useful for a number of therapeutic modalities including implantation of epicardial pacing leads. We have developed a catheter-based transvenous method to access the PS for implanting chronic medical devices.

METHODS

In eight pigs, a transseptal Mullins sheath and Brockenbrough needle were introduced into the right atrium (RA) from the jugular vein under fluoroscopic guidance. The PS was entered through a controlled puncture of the terminal anterior superior vena cava (SVC) (n = 7) or right atrial appendage (n = 1). A guidewire was advanced through the transseptal sheath, which was then removed leaving the wire in PS. The guidewire was used to direct both passive and active fixation pacing leads into the PS. Pacing was attempted and lead position was confirmed by cine fluoroscopy. Animals were sacrificed acutely and at 2 and 6 weeks.

RESULTS

All animals survived the procedure. Pericardial effusion (PE) during the procedure was hemodynamically significant in four of the eight animals. At necropsy, lead exit sites appeared to heal without complication at 2 and 6 weeks. Volume of pericardial fluid was 10.8 +/- 6.2 mL and appeared normal in four of the six chronic animals. Moderate fibrinous deposition was observed in two animals, which had exhibited significant over-procedural PE.

CONCLUSIONS

Access to the PS via a transvenous approach is feasible. Pacing leads can be negotiated into this region. The puncture site heals with the lead in place. Further development should focus on eliminating PE and performing this technique in appropriate heart failure models.

Potent antifibrillatory effects of intrapericardial nitroglycerin in the ischemic porcine heart

OBJECTIVES

We investigated the antiarrhythmic effects of intrapericardial nitroglycerin (NTG) during acute myocardial ischemia in the porcine heart.

BACKGROUND

Nitroglycerin is a nitric oxide donor that exerts potent effects on the cardiovascular system. Intrapericardial administration allows investigation of pharmacologic actions on cardiac tissue in an in vivo system while minimizing the confounding influences of systemic effects.

METHODS

In 29 closed-chest pigs, myocardial ischemia was induced by intraluminal balloon occlusion of the left anterior descending coronary artery. Arrhythmia incidence was monitored during 5-min balloon inflations performed without drug and at 15, 45, 75, and 105 min after NTG (4,000 microg bolus) administered by percutaneous transatrial access into the pericardial space. Electrocardiograms were monitored for ischemia-induced T-wave alternans (TWA), a marker of electrical instability. The antiadrenergic potential of NTG was investigated by examining the drug's suppression of dobutamine-induced increase in myocardial contractility.

RESULTS

Control coronary artery occlusion provoked ventricular fibrillation (VF) in all animals. Intrapericardial NTG suppressed VF at 45 min in all six pigs (p < 0.05) and reduced TWA across a parallel time course (from 459.1 +/- 144.4 microV before drug to 42.22 +/- 13.96 microV at 45 min, p = 0.047). The antifibrillatory effect occurred as early as 15 min and persisted for up to 75 min. Augmentation of maximum of the first time derivative of left ventricular pressure by dobutamine was blunted by intrapericardial NTG (from 3,999 +/- 196 mm Hg/s before NTG to 3,543 +/- 220 mm Hg/s at 15 min, p = 0.012).

CONCLUSIONS

Intrapericardial NTG exerts a robust antifibrillatory action. Potential mechanisms include reduction in electrical instability and blunting of adrenergic effects.

A new diagnostic and therapeutic approach to pericardial effusion: transbronchial needle aspiration

Pericardiocentesis was introduced during the 19th century, and reached its current level of development with the introduction of two-dimensional echocardiography. Although there is general agreement that complications are rare with skilled operators, a diagnostic and therapeutic problem often occurs when there is a posterior pericardial effusion, as it is not easy to quantify by echocardiography, and difficult to drain through a percutaneous access; therefore, it is usually treated surgically. We describe a new approach to pericardial effusion by a transbronchial access through the left lower lobe bronchus (which allows both diagnosis and evacuation of abundant amounts of fluid), or through the distal trachea (for diagnostic purpose only, in the presence of pericardial effusions filling the aortic recess of the pericardium). The technique is rather easy for operators skilled in transbronchial needle aspiration, and is safe, economical, and well tolerated.

Pericardial anatomy for the interventional electrophysiologist

Investigators are beginning to exploit the pericardial space for a number of cardiovascular applications, including catheter ablation of cardiac arrhythmias, cardiovascular drug therapy, and cardiac pacing. This review explores the anatomy of the pericardial space and the anatomic variants that may be encountered in this novel approach to the heart.

Intrapericardial administration of basic fibroblast growth factor: myocardial and tissue distribution and comparison with intracoronary and intravenous administration

Growth factor-induced angiogenesis is being investigated in ischemic heart disease. Intracoronary and intravenous delivery are the most practical, but are limited by low myocardial uptake and significant systemic recirculation. The pericardial space may act as a drug delivery reservoir with increased myocardial uptake and reduced systemic toxicities. This study was designed to investigate the myocardial and tissue deposition and retention of basic fibroblast growth factor (FGF-2) after intrapericardial administration in normal and chronically ischemic animals. Twelve Yorkshire pigs were used for the study [six normal and six animals with chronic myocardial ischemia (ameroid constrictor on LCx)] with bolus intrapericardial administration of (125)I-FGF-2 (25 micro Ci) with 30 micro g of cold FGF-2 and 3 mg of heparin. Tissue and myocardial distribution was determined at 1 and 24 hr by measuring (125)I-bFGF-specific activity. In addition, regional myocardial deposition was determined using (125)I-bFGF activity and organ level autoradiography. The heart (pericardium and myocardium) accounted for the majority of (125)I-bFGF activity in ischemic animals (30.9% at 1 hr and 23.9% at 24 hr). Left anterior descending artery territory activity/gm of tissue for nonischemic and ischemic animals was 0.01% and 0.01% at 1 hr and 0.0009% and 0.12% at 24 hr, respectively. LCx territory activity for nonischemic and ischemic animals was 0.006% and 0.008% at 1 hr and 0.03% and 0.05% at 24 hr, respectively. Endocardial activity was low at all time points. Liver uptake was 0.47% (nonischemic) and 0.34% (ischemic) at 1 hr and 0.23% (nonischemic) and 0.54% (ischemic) at 24 hr. Intrapericardial delivery of FGF-2 provides markedly higher myocardial deposition and retention and lower systemic recirculation than intracoronary or intravenous delivery at the expense of poor subendocardial penetration. This limitation, however, did not affect its efficacy.

Simultaneous intra/extravascular administration of antiproliferative agents as a new strategy to inhibit restenosis: the peak of reactive cell proliferation as a hallmark for the duration of the treatment

BACKGROUND

Strictly intravascular approaches for the treatment of postangioplasty restenosis are effective in the intima and the inner parts of the media but may be insufficient to control redundant pathways in the more outer parts of the media and the adventitia. An inverse situation may occur subsequently to a strictly extravascular approach, like the recently suggested pericardial approach in pigs. We hypothesized that simultaneous intra/extravascular administration of anti-restenotic agents inhibits restenosis by blocking all stimulatory pathways in the entire arterial wall.

METHODS

Fresh hearts of 25 domestic pigs were obtained from a local slaughterhouse. Left anterior descending coronary arteries (LAD) were harvested, cut into cylindric 5 mm segments, and cultured as ex vivo porcine organ cultures (POCs). After 9 bar ballooning simultaneous intra/extravascular administration of high dose diltiazem (50 microg/mL) was carried out for a period of 1, 2, 3, 4, 5, 6, and 7 days. At day 7 and 28 proliferative activity (BrdU), neointimal thickening, and staining against smooth muscle alpha-actin and vWF was analysed.

RESULTS

7 days after ballooning administration of diltiazem for 4, 5, 6, and 7 days inhibited reactive cell proliferation by more than 50% (n.s.) as compared to control, 28 days after ballooning administration for 6 and 7 days inhibited neointimal thickening by more than 75% (p < 0.05). Simultaneous intra/extravascular administration of high dose diltiazem did not affect the expression of vWF in endothelial cells or smooth muscle alpha-actin in smooth muscle cells.

CONCLUSIONS

Simultaneous intra/extravascular administration of high dose diltiazem (50 microg/mL) has to be maintained for at least 6 days to achieve a significant inhibition of neointimal thickening. The data demonstrate the importance of the maximal reactive cell proliferation (= day 7 in the POC-model) for the calculation of the duration of the treatment period.

Transthoracic epicardial catheter ablation to treat recurrent ventricular tachycardia

Nonsurgical epicardial transthoracic catheter ablation is a minimally invasive procedure that has proven to be efficacious for the treatment of ventricular tachycardia (VT). The usefulness of this technique depends on the prevalence of epicardial circuits, which seem more frequent in Chagasic than post-myocardial infarction VT. This approach is limited by concern regarding the potential adverse effects of radiofrequency (RF) ablation on the coronary arteries. However, the effects of RF ablation delivered in the vicinity of a major coronary artery are limited to the medial artery. Severe intimal hyperplasia and intravascular thrombosis may occur only when RF ablation is delivered above the artery. Moreover, susceptibility to damage is inversely proportional to the vessel size. Coronary artery injury is an uncommon (< 1%) complication that could be prevented by a coronary angiogram prior to ablation. Hemopericardium, another predictable complication occurring in 10% of patients, can be easily controlled in the electrophysiology laboratory.

Transatrial access to the normal pericardial space for local cardiac therapy: preclinical safety testing with aspirin and pulmonary artery hypertension

The reliability, rapidity, and safety of nonsurgical, transatrial pericardial access for local cardiac therapy have been demonstrated in healthy animals. Since many patients take aspirin or have increased right-sided pressures, we evaluated the procedure's safety under these conditions. Transatrial pericardial access was performed in anesthetized pigs following aspirin administration (162 mg p.o., n = 6) or during experimental pulmonary artery hypertension (n = 4 different animals) and required only 3 minutes following guide catheter positioning. Platelet aggregability testing with arachidonic acid confirmed aspirin effectiveness. Mean pericardial fluid hematocrit was 0.1 +/- 0.1% after 2 days of aspirin therapy and 1.9 +/- 1.1% at sacrifice 24 hours later (NS). Mean pericardial fluid hematocrit was 1.0 +/- 0.5% after 45 minutes of pulmonary artery hypertension and 4.3 +/- 0.8% at sacrifice 30 minutes later (NS). Histologic analysis in both groups revealed a small thrombus and localized inflammation at the site of puncture. Neither aspirin use nor pulmonary artery hypertension causes significant bleeding into the pericardial space following transatrial access and thus does not preclude this route for local cardiac drug delivery.

Pericardial fluid as a new material for clinical heart research

This article will review the results of recent clinical studies relating to the pericardial fluid in patients with various heart diseases. In ischemic patients, several angiogenic growth factors are accumulated in a high concentration in pericardial fluid. These may contribute to the angiogenesis and arteriogenesis, which are self-protecting mechanisms of myocardial ischemia. In congestive heart failure, natriuretic peptides are released into the pericardial fluid in a higher concentration compared with plasma levels. This suggests that these peptides may act as autocrine and/or paracrine factors. Pericardial fluid from ischemic patients induces cell proliferation and apoptosis depending on the cell type. Intrapericardial drug administration may provide a reasonable therapeutic strategy for heart diseases. In conclusion, the analysis of pericardial fluid appears to be a logical approach for elucidation of the pathophysiology of the heart.

Intrapericardial beta-adrenergic blockade with esmolol exerts a potent antitachycardic effect without depressing contractility

Hyperadrenergic states of various etiologies can contribute to tachycardias. Systemic beta-adrenergic blockade suppresses sinus tachycardia but may adversely affect arterial blood pressure and contractility, because the drug gains access to myocardial cells as well as to the sinoatrial node. We examined whether intrapericardial beta-adrenergic blockade with esmolol could suppress tachycardia without reducing contractility as a result of limited drug diffusion, which would be sufficient to penetrate the superficial sinoatrial node but not the deeper myocardial layers. In five anesthetized pigs, we provoked a reflex heart rate increase of 50 beats/min with hemorrhage. The rapidly acting beta-adrenergic blocking agent esmolol (1 mg/kg) was administered intrapericardially using a new percutaneous transatrial access method and a catheter system that can be rapidly and safely introduced. Esmolol equivalently suppressed hemorrhage-induced sinus tachycardia when administered intrapericardially (from 192 to 158 beats/min at 5 min, p < 0.05) or intravenously (from 177 to 151 beats/min at 1 min, p < 0.05). The antitachycardic effect of intrapericardial esmolol was prolonged compared with intravenous esmolol (10 min vs. 3 min, p < 0.05). Intrapericardial esmolol did not affect blood pressure or left ventricular dP/dt max, an index of contractility, whereas intravenous esmolol decreased blood pressure at 1 min for 2 min (p < 0.05) and simultaneously decreased left ventricular dP/dt max at 1 min for < 2 min (p < 0.05). Intrapericardial esmolol suppresses adrenergically induced sinus tachycardia without decreasing contractility or blood pressure. The transatrial approach for intrapericardial delivery of certain 1-adrenergic blocking agents could be employed to control tachycardias in emergency care and surgical settings in patients with impaired cardiac contractility and propensity to hypotension.

Preclinical safety testing of percutaneous transatrial access to the normal pericardial space for local cardiac drug delivery and diagnostic sampling

The safety of a percutaneous method and streamlined catheter system to access the normal pericardial space via the right atrial appendage for drug delivery and diagnostic sampling was demonstrated in 20 anesthetized pigs. Access was successfully accomplished in all animals within 3 min of guide catheter positioning and was documented by fluoroscopic imaging and pericardial fluid sampling. The animals were sacrificed at 24 hr (n = 10) and 2 weeks (n = 10) for histopathologic analysis. Mean pericardial hematocrit was 1.1% +/- 0.3% at initial sampling, 4.3% +/- 1.4% at 24 hr (P = 0.005 vs. baseline), and 0.4% +/- 0.2% at 2 weeks (P = 0.13 vs. baseline). At 24 hr, there was local inflammatory reaction in the atrial wall and a small thrombus at the site of puncture. At 2 weeks, no significant inflammatory changes or pericarditis were evident. The technique is well tolerated with no apparent adverse complications. Advances in intrapericardial therapeutics and diagnostics will direct the clinical application of this novel approach in human subjects.