Persistent primary coronary dilation induced by transatrial delivery of nitroglycerin into the pericardial space: a novel approach for local cardiac drug delivery

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.

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.

Nanoparticles administered intrapericardially enhance payload myocardial distribution and retention

Pharmacological therapies for cardiovascular diseases are limited by short-term pharmacokinetics and extra-cardiac adverse effects. Improving delivery selectivity specifically to the heart, wherein therapeutic drug levels can be maintained over time, is highly desirable. Nanoparticle (NP)-based pericardial drug delivery could provide a strategy to concentrate therapeutics within a unique, cardiac-restricted compartment to allow sustained drug penetration into the myocardium. Our objective was to explore the kinetics of myocardial penetration and retention after pericardial NP drug delivery. Fluorescently-tagged poly(lactic-co-glycolic acid) (PLGA) NPs were loaded with BODIPY, a fluorophore, and percutaneously administered into the pericardium via subxiphoid puncture in rabbits. At distinct timepoints hearts were examined for presence of NPs and BODIPY. PLGA NPs were found non-uniformly distributed on the epicardium following pericardial administration, displaying a half-life of ~2.5days in the heart. While NPs were mostly confined to epicardial layers, BODIPY was capable of penetrating into the myocardium, resulting in a transmural gradient. The distinct architecture and physiology of the different regions of the heart influenced BODIPY distribution, with fluorophore penetrating more readily into atria than ventricles. BODIPY proved to have a long-term presence within the heart, with a half-life of ~7days. Our findings demonstrate the potential of utilizing the pericardial space as a sustained drug-eluting reservoir through the application of nanoparticle-based drug delivery, opening several exciting avenues for selective and prolonged cardiac therapeutics.

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.

Potential of gene therapy as a treatment for heart failure

Advances in understanding the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology, make gene-based therapy a promising treatment option for heart conditions. Cardiovascular gene therapy has benefitted from recent advancements in vector technology, design, and delivery modalities. There is a critical need to explore new therapeutic approaches in heart failure, and gene therapy has emerged as a viable alternative. Advances in understanding of the molecular basis of myocardial dysfunction, together with the development of increasingly efficient gene transfer technology, has placed heart failure within reach of gene-based therapy. The recent successful and safe completion of a phase 2 trial targeting the cardiac sarcoplasmic/endoplasmic reticulum Ca2+ ATPase pump (SERCA2a) has the potential to open a new era for gene therapy for heart failure.

Percutaneous methods of vector delivery in preclinical models

Cardiovascular disease remains a leading cause of hospitalization and mortality worldwide. Conventional heart failure treatment is making steady and substantial progress to reduce the burden of disease. Nevertheless novel therapies and especially cardiac gene therapy have been emerging in the past and successfully made their way into first clinical trials. Gene therapy was initially a visionary treatment strategy for inherited, monogenetic diseases but has now developed to have potential for polygenic diseases as atherosclerosis, arrhythmias and heart failure. These novel therapeutic strategies require testing in clinically relevant animal models to transition from 'bench to bedside'. One of the major hurdles for effective cardiovascular gene therapy is the delivery of the viral vectors to the heart. In this review we present the currently available vector-mediated cardiac gene delivery methods in vivo considering the specific merits and deficiencies.

Adjuvant early and late cardioprotective therapy: access to the heart

Coronary heart disease is still the leading cause of death in industrialized nations, occurring either as acute coronary occlusion and myocardial infarction or as chronic ischaemic cardiomyopathy caused by continuous obstruction of one or more coronary arteries. Even after successful reperfusion, an additional loss of otherwise vital cardiomyocytes may occur in the primary ischaemic area, called lethal reperfusion injury. In experimental settings, delivery of therapeutic agents targeting the reperfusion injury reduces the infarct size by 30%. In addition to the choice of therapeutic agent and time point, the mode of application may be crucial for the therapeutic success. Therefore, this review focuses on the current and future administration techniques for early and late post-myocardial infarction therapies.

Concomitant intravenous nitroglycerin with intracoronary delivery of AAV1.SERCA2a enhances gene transfer in porcine hearts

SERCA2a gene therapy improves contractile and energetic function of failing hearts and has been shown to be associated with benefits in clinical outcomes, symptoms, functional status, biomarkers, and cardiac structure in a phase 2 clinical trial. In an effort to enhance the efficiency and homogeneity of gene uptake in cardiac tissue, we examined the effects of nitroglycerin (NTG) in a porcine model following AAV1.SERCA2a gene delivery. Three groups of Göttingen minipigs were assessed: (i) group A: control intracoronary (IC) AAV1.SERCA2a (n = 6); (ii) group B: a single bolus IC injection of NTG (50 µg) immediately before administration of intravenous (IV) AAV1.SERCA2a (n = 6); and (iii) group C: continuous IV NTG (1 µg/kg/minute) during the 10 minutes of AAV1.SERCA2a infusion (n = 6). We found that simultaneous IV infusion of NTG and AAV1.SERCA2a resulted in increased viral transduction efficiency, both in terms of messenger RNA (mRNA) as well as SERCA2a protein levels in the whole left ventricle (LV) compared to control animals. On the other hand, IC NTG pretreatment did not result in enhanced gene transfer efficiency, mRNA or protein levels when compared to control animals. Importantly, the transgene expression was restricted to the heart tissue. In conclusion, we have demonstrated that IV infusion of NTG significantly improves cardiac gene transfer efficiency in porcine hearts.

Delivery of gelfoam-enabled cells and vectors into the pericardial space using a percutaneous approach in a porcine model

Intrapericardial drug delivery is a promising procedure, with the ability to localize therapeutics with the heart. Gelfoam particles are nontoxic, inexpensive, nonimmunogenic and biodegradable compounds that can be used to deliver therapeutic agents. We developed a new percutaneous approach method for intrapericardial injection, puncturing the pericardial sac safely under fluoroscopy and intravascular ultrasound (IVUS) guidance. In a porcine model of myocardial infarction (MI), we deployed gelfoam particles carrying either (a) autologous mesenchymal stem cells (MSCs) or (b) an adenovirus encoding enhanced green fluorescent protein (eGFP) 48 h post-MI. The presence of MSCs and viral infection at the infarct zone was confirmed by immunoflourescence and PCR. Puncture was performed successfully in 16 animals. Using IVUS, we successfully determined the size of the pericardial space before the puncture, and safely accessed that space in setting of pericardial effusion and also adhesions induced by the MI. Intrapericardial injection of gelfoam was safe and reliable. Presence of the MSCs and eGFP expression from adenovirus in the myocardium were confirmed after delivery. Our novel percutaneous approach to deliver (stem-) cells or adenovirus was safe and efficient in this pre-clinical model. IVUS-guided delivery is a minimally invasive procedure that seems to be a promising new strategy to deliver therapeutic agents locally to the heart.

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.

Future Developments in Nonsurgical Epicardial Therapies

The unique anatomic position of the pericardium in juxtaposition to central cardiac structures enables it to serve as the ideal vantage point for the delivery of novel cardiovascular therapies. Development of new tools to permit delivery of therapy in the closed pericardial space holds promise for near-surgical access to the heart, without open surgical morbidity. Early observations raise hope for the availability of epicardial leads to enhance cardiac resynchronization therapy designed for subxiphoid nonsurgical percutaneous delivery. Emerging technologies for left atrial appendage ligation may offer new strategies for preventing stroke.

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.

The role of periadventitial fat in atherosclerosis

CONTEXT

It has become increasingly evident that adipose tissue is a multifunctional organ that produces and secretes multiple paracrine and endocrine factors. Research into obesity, insulin resistance, and diabetes has identified a proinflammatory state associated with obesity. Substantial differences between subcutaneous and omental fat have been noted, including the fact that omental fat produces relatively more inflammatory cytokines. Periadventitial fat, as a specific adipose tissue subset, has been overlooked in the field of atherosclerosis despite its potential diagnostic and therapeutic implications.

OBJECTIVE

To review (1) evidence for the role of adventitial and periadventitial fat in vessel remodeling after injury, (2) the relationship between adventitial inflammation and atherosclerosis, (3) the association between periadventitial fat and plaque inflammation, and (4) the diagnostic and therapeutic implications of these roles and relationships for the progression of atherosclerosis.

DATA SOURCES

We present new data showing greater uptake of iron, administered in the form of superparamagnetic iron oxide, in the periadventitial fat of atherosclerotic mice than in control mice. In addition, macrophage density in the periadventitial fat of lipid-rich plaques is increased compared with fibrocalcific plaques.

CONCLUSIONS

There is a striking paucity of data on the relationship between the periadventitial fat of coronary arteries and atherosclerosis. Greater insight into this relationship might be instrumental in making strides into the pathophysiology, diagnosis, and treatment of coronary artery disease.

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.

Intrapericardial drug delivery: pharmacologic properties and long-term safety in swine

BACKGROUND

Intrapericardial drug delivery is a promising new technique, but the pharmacologic properties of various agents delivered via this route are not known. Furthermore, the long-term safety of intrapericardial catheters has not been previously examined.

METHODS

Using a pericardial access device, a catheter connected to a drug-delivery system was implanted in five pigs. Plasma levels and electrocardiographic measurements were obtained after intravenous and intrapericardial administration of digoxin and procainamide. Histological examination was performed after the device had been implanted for a total of 6 months.

RESULTS

The QTc interval did not change significantly after digoxin or procainamide intravenous administration. QTc decreased by 47+/-23 ms (p=0.046) 8 h after digoxin intrapericardial administration and increased by 128+/-60 ms (p=0.002) 1 h after procainamide intrapericardial administration. The QRS duration did not change significantly after intravenous administration of either agent, but it increased by 17+/-9 ms (p=0.004) 1 h and by 15+/-4 ms (p=0.01) 8 h after procainamide intrapericardial administration. After intravenous procainamide the RR interval decreased, but it did not change significantly after intrapericardial administration of either agent. Histology showed moderate inflammatory infiltration and fibrosis adjacent to the catheter.

CONCLUSIONS

Intrapericardial delivery of digitalis and procainamide produces unique electrophysiological properties. In contrast to satisfactory success of the implantation technique, long-term dwell of the catheter in the pericardium induces moderate, albeit probably clinically significant, fibrosis.

Intrapericardial Delivery Enhances Cardiac Effects of Sotalol and Atenolol

Targeting drugs to the heart by intrapericardial (i.p.c.) delivery may be a promising strategy to obtain higher drug efficiencies with lesser side effects. We examined whether i.p.c. delivery of sotalol and atenolol in rats offers advantages over intravenous (i.v.) application. Following sustained IPC infusion of sotalol or atenolol, pericardial fluid levels exceeded plasma levels 97 and 134 times respectively (P < 0.01) resulting in 3.8 and 4.7 times higher overall left ventricular tissue drug levels (P < 0.05). In a second experiment, the effects of the i.p.c. or i.v. beta-blocker infusions on nitroprusside-induced tachycardia were studied in conscious rats. For both drugs, i.p.c. infusion of 0.03 mg/kg.h produced similar antitachycardiac effects as the 1 mg/kg.h i.v. dose. In a third set of studies, dP/dt max challenged by dobutamine infusion was assessed to study ventricular contractile function after i.v. and i.p.c. sotalol in anesthetized rats. i.p.c. sotalol infusion attenuated the dobutamine response curve to a greater extent than i.v. (P < 0.01). In conclusion, i.p.c. infusion of sotalol and atenolol results in high cardiac tissue concentrations with low systemic drug levels. Similar antitachycardiac effects can be obtained at a 10- to 30-fold lower dose compared with i.v. delivery. Also, depression of ventricular contractility is acquired at a substantially lower i.p.c. sotalol dose. Thus, beta-blocking properties of sotalol and atenolol can be greatly enhanced by applying them i.p.c.

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.

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.

Pharmacokinetic advantage of intrapericardially applied substances in the rat

Intrapericardial application of therapeutic agents may open perspectives for target-directed therapy of the diseased heart. This study was performed to investigate whether intrapericardial drug application is beneficial from a pharmacokinetic point of view. Male Wistar rats were provided with intrapericardial and intravascular catheters for substance administration and sampling. Intrapericardial bolus injections of fluorescent macromolecules [fluorescein isothiocyanate (FITC)-rat IgG, molecular weight about 155 kDa; Texas Red rat serum albumin, mol. wt. 67 kDa; Texas Red fibroblast growth factor (FGF), mol. wt. 18 kDa; and FITC heparin, mean mol. wt. 18 kDa] resulted in substance concentrations in pericardial fluid that exceeded those in plasma, for several hours. Pericardial fluid volumes of catheter-instrumented rats, derived from (initial) central compartment volumes, ranged between 0.5 and 0.9 ml/kg. After chronic (7 days) intrapericardial infusions with osmotic minipumps, pericardial fluid/plasma concentration ratios (local advantages) were 7 to 10 for the fluorescent proteins and >30 for FITC-heparin. This can be explained by the low substance clearances in pericardial fluid compared with plasma. Local advantages of the small substances cortisol (mol. wt. = 362.5) and a carbonic acid derivative thereof (mol. wt. = 348) were 14 and 420. Intrapericardial infusion of (125)I-FGF-2 yielded 8 times higher cardiac tissue levels than systemic infusion, whereas (125)I-FGF-2 was found in the entire heart. Pharmacokinetic profiles of intrapericardially applied substances are such that desired local drug concentrations can be obtained at lower dosages, whereas systemic concentrations remain low (thus reducing the potential risk of peripheral side effects). Therefore, intrapericardial application of therapeutic agents provides a promising strategy for site-specific treatment of heart or coronary diseases.

Thoracoscopic monitoring for pericardial application of local drug or gene therapy

Cardiovascular gene therapy is a promising new approach for a variety of diseases. As far as gene therapy aimed at the myocardium is concerned a new transcutaneous delivery method may be into the pericardial sac.

OBJECTIVE

To evaluate the safety and applicability of the percutaneous pericardial delivery route for drug- or gene-therapy.

METHODS

A percutaneous pericardial access device called a perducer was used to deliver either Indian ink or methylene blue to the pericardium of male yorkshire pigs under hemodynamic surveillance. Animals were sacrificed after either 3 h or 3 days. Post mortem distribution of the injectate was evaluated macroscopically and microscopically.

RESULTS

With the perducer, the pericardial cavity was punctured in 10 pigs without hemodynamic complications. Although traces of dye could be seen in the pleural cavity in pigs sacrificed after 3 h, no evidence for dissemination was found in myocardial, lung, mediastinal lymph node and liver tissue in pigs sacrificed after 3 days. In two additional pigs the pericardium was punctured with the same perducer technique under simultaneous thoracoscopic monitoring. Visualization of the surface of the pericardium facilitated the procedure because pericardial fat could be avoided.

CONCLUSION

Obtaining access to the pericardium with the perducer technique is safe and feasible. In addition thoracoscopic guidance may improve success rate and offers the possibility of on line surveillance.

Elevated interleukin-1beta in pericardial fluid of patients with ischemic heart disease

BACKGROUND

Inflammatory cytokines may play an important role in the pathogenesis of atherosclerosis and heart failure. We have previously demonstrated that long-term treatment with interleukin (IL)-1beta in the coronary artery and myocardium promotes coronary arteriosclerosis and impairs cardiac function, respectively. The cytokines in pericardial fluid may reflect the extent of coronary atherosclerosis and may also directly promote the atherosclerotic process. This study was designed to examine the significance of cytokine concentrations in pericardial fluid of patients with cardiovascular disease.

METHODS

We measured concentrations of 10 major cytokines in the pericardial fluid of 56 consecutive patients obtained during open heart surgery, 27 with ischemic heart disease (IHD group), 21 with valvular heart disease (VHD group) and eight with congenital heart disease (CHD group).

RESULTS

The pericardial concentrations of IL-1beta (pg/ml) were significantly higher in the IHD group (60 +/- 15) than in the VHD (29 +/- 5) or the CHD group (26 +/- 4) (P < 0.05 both). There was no significant difference in pericardial concentrations of other cytokines among the three groups. In the IHD group, the IL-1beta concentrations were significantly elevated in patients who had undergone emergency operations or in those with unstable angina.

CONCLUSIONS

These results suggest that pericardial concentrations of IL-1beta may reflect the extent of ischemic heart disease and that elevated IL-1beta concentrations in pericardial fluid may also directly promote the process of coronary atherosclerosis.

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.

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.

Intrapericardial paclitaxel delivery inhibits neointimal proliferation and promotes arterial enlargement after porcine coronary overstretch

BACKGROUND

Catheter-based intrapericardial (IPC) delivery of therapeutic agents has recently been demonstrated. Paclitaxel is known to inhibit vascular smooth muscle cell proliferation. This study examined the effect of IPC instillation of paclitaxel on neointimal proliferation after balloon overstretch of porcine coronary arteries.

METHODS AND RESULTS

Overstretch injury of coronary arteries was followed by IPC administration of micellar paclitaxel at low dose (LD, 10 mg; n=6) or high dose (HD, 50 mg; n=7) or of control micelles (50 mg, n=5). Animals were euthanized 28 days after balloon dilation. Arterial injury indices were no different among the groups. The neointimal area, maximal intimal thickness, and adventitial thickness were significantly reduced in both LD (0.47+/-0.04 mm(2), 0.43+/-0.03 mm, and 0.35+/-0.02 mm, respectively) and HD (0.51+/-0.06 mm(2), 0.42+/-0.03 mm, and 0. 38+/-0.03 mm, respectively) paclitaxel groups compared with the control group (0.79+/-0.07 mm(2), 0.56+/-0.02 mm, and 0.47+/-0.02 mm, respectively; P:<0.001). Meanwhile, the vessel circumference measured at the external elastic lamina of paclitaxel-treated vessels was significantly larger than the control circumference. Apoptotic cells were found in the neointima. The apoptotic cell percentage was not different between the control (1.72%) and LD (2. 31%) groups but was higher in the HD group (7.07%, P:<0.0001 versus control and LD groups). Immunostaining for matrix metalloproteinase-2 revealed concurrent reduction in the HD group compared with the control and LD groups.

CONCLUSIONS

IPC space delivery of a single dose of paclitaxel significantly reduces vessel narrowing in this balloon-overstretch model. This effect is mediated by reduction of neointimal mass as well as positive vascular remodeling.

Clinical trials in coronary angiogenesis: issues, problems, consensus: An expert panel summary

The rapid development of angiogenic growth factor therapy for patients with advanced ischemic heart disease over the last 5 years offers hope of a new treatment strategy based on generation of new blood supply in the diseased heart. However, as the field of therapeutic coronary angiogenesis is maturing from basic and preclinical investigations to clinical trials, many new and presently unresolved issues are coming into focus. These include in-depth understanding of the biology of angiogenesis, selection of appropriate patient populations for clinical trials, choice of therapeutic end points and means of their assessment, choice of therapeutic strategy (gene versus protein delivery), route of administration, and the side effect profile. The present article presents a summary statement of a panel of experts actively working in the field, convened by the Angiogenesis Foundation and the Angiogenesis Research Center during the 72nd meeting of the American Heart Association to define and achieve a consensus on the challenges facing development of therapeutic angiogenesis for coronary disease.

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.