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

Living Anatomy of the Pericardial Space: A Guide for Imaging and Interventions

The pericardium of the human heart has received increased attention in recent times due to interest in the epicardial approach for cardiac interventions to treat cardiac arrhythmias refractory to conventional endocardial approaches. To support further clinical application of this technique, it is fundamental to appreciate the living anatomy of the pericardial space, as well as its relationships to the surrounding structures. The anatomy of the pericardial space, however, is extremely difficult regions to visualize. This is due to its complex 3-dimensionality, and the "potential" nature of the space, which becomes obvious only when there is collection of pericardial fluid. This potential space, which is bounded by the epicardium and pericardium, can now be visualized by special techniques as we now report, permitting appreciation of its living morphology. Current sources of knowledge are limited to the dissection images, surgical images, and/or illustrations, which are not necessarily precise or sufficient to provide relevant comprehensive anatomical knowledge to those undertaking the epicardial approach. The authors demonstrate, for the first time to their knowledge, the 3-dimensional living anatomy of the pericardial space relative to its surrounding structures. They also provide correlative anatomy of the left sternocostal triangle as a common site for subxiphoid access. The authors anticipate their report serving as a tool for education of imaging and interventional specialists.

Anatomy of the Pericardial Space

The pericardial cavity and its boundaries are formed by the reflections of the visceral and parietal pericardial layers. This space is an integral access point for epicardial interventions. As the pericardial layers reflect over the great vessels and the heart, they form sinuses and recesses, which restrict catheter movement. The epicardial vasculature is also important when performing nearby catheter ablation. The phrenic nerve and esophagus are other important structures to appreciate so as to avoid collateral injury. In addition, the Larrey space, or left sternocostal triangle, is a key avascular window through which pericardial access can be safely achieved.

Percutaneous Pericardial Resection: A Novel Potential Treatment for Heart Failure With Preserved Ejection Fraction

BACKGROUND

People with heart failure and preserved ejection fraction develop increases in left ventricular (LV) end-diastolic pressures during exercise that contribute to dyspnea. In normal open-chest animal preparations, the pericardium restrains LV filling when central blood volume increases. We hypothesized that resection of the pericardium using a minimally invasive epicardial approach would mitigate the increase in LV end-diastolic pressure that develops during volume loading in normal and diseased hearts with the chest intact.

METHODS AND RESULTS

Invasive hemodynamic assessment was performed at baseline and after saline load before and after pericardial resection in normal canines with open (n=3) and closed chest (n=5) and in a pig model with features of human heart failure and preserved ejection fraction with sternum intact (n=4). In closed-chest animals, pericardiotomy was performed using a novel subxiphoid procedure. In both experimental preparations of normal dogs, pericardiotomy blunted the increase in LV end-diastolic pressure with saline infusion, while enhancing the saline-mediated increase in LV end-diastolic volume. With chest intact in the pig model, percutaneous pericardial resection again blunted the increase in LV end-diastolic pressure secondary to volume expansion (+4±3 versus +13±5 mm Hg; P=0.014), while enhancing the saline-mediated increase in LV end-diastolic volume (+17±1 versus +10±2 mL; P=0.016).

CONCLUSIONS

This proof of concept study demonstrates that pericardial resection through a minimally invasive percutaneous approach mitigates the elevation in LV filling pressures with volume loading in both normal animals and a pig model with diastolic dysfunction. Further study is warranted to determine whether this method is safe and produces similar acute and chronic hemodynamic benefits in people with heart failure and preserved ejection fraction.

Percutaneous Epicardial Pacing using a Novel Insulated Multi-electrode Lead

INTRODUCTION

Epicardial cardiac resynchronization therapy (CRT) permits unrestricted electrode positioning. However, this requires surgical placement of device leads and the risk of unwanted phrenic nerve stimulation. We hypothesized that shielded electrodes can capture myocardium without extracardiac stimulation.

METHODS

In 6 dog and 5 swine experiments, we used a percutaneous approach to access the epicardial surface of the heart, and deploy novel leads housing multiple electrodes with selective insulation. Bipolar pacing thresholds at prespecified sites were tested compare electrode threshold data both facing towards and away from the epicardial surface.

RESULTS

In 151 paired electrode recordings (70 in 6 dogs; 81 in 5 swine), thresholds facing myocardium were lower than facing away (median [IQR] mA: dogs 0.9 [0.4-1.6] vs 4.6 [2.1 to >10], p<0.0001; swine 0.5 [0.2-1] vs 2.5 [0.5-6.8], p<0.0001). Myocardial capture was feasible without extracardiac stimulation at all tested sites, with mean ± SE threshold margin 3.6±0.7 mA at sites of high output extracardiac stimulation (p=0.004).

CONCLUSION

Selective electrode insulation confers directional pacing to a multielectrode epicardial pacing lead. This device has the potential for a novel percutaneous epicardial resynchronization therapy that permits placement at an optimal pacing site, irrespective of the anatomy of the coronary veins or phrenic nerves.

Left atrial appendage exclusion for atrial fibrillation

Percutaneous left atrial appendage (LAA) closure is being increasingly used as a treatment strategy to prevent stroke in patients with atrial fibrillation (AF) who have contraindications to anticoagulants. Several approaches and devices have been developed in the last few years, each with their own unique set of advantages and disadvantages. In this article, the published studies on surgical and percutaneous approaches to LAA closure are reviewed, focusing on stroke mechanisms in AF, LAA structure and function relevant to stroke prevention, practical differences in procedural approach, and clinical considerations surrounding management.