How to Perform an Epicardial Access
Mauricio I. Scanavacca, MD, PhD; Sissy Lara Melo, MD, PhD; Carina A. Hardy, MD; Cristiano Pisani, MD; Eduardo Sosa, MD, PhD
Subepicardial myocardial fibers may be the source of origin of cardiac arrhythmias in patients with1,2 or without3 structural heart diseases, and one of the reasons for unsuccessful RF catheter ablation in patients, in which endocardial ablation was unable to reach such fibers.
Electrophysiologists have been searching subepicardial fibers by two techniques: exploring the coronary sinus, as well as the great cardiac vein and its branches,4 and using the direct access to the pericardial space through the subxiphoid approach.5,6 The transvenous access is very useful when the target fibers are related to the mitral annulus or located close to the coronary vascular system. The subxiphoid access has been useful to access beyond those places, exploring extensive areas of the epicardial surface of the heart. Figure 45.1 shows a combination of endocardial and epicardial electroanatomic map and a scar-related VT that is predominantly subepicardial. In these cases, RF epicardial ablation is very effective to interrupt the macroreentrant circuit and render VT no more inducible.
In this chapter, we will focus on how to perform and to avoid complications when performing the percutaneous subxiphoid access to the pericardial space, and also how to solve the most common related problems.
Before Scheduling the Pericardial Space Access
Before scheduling a patient for an epicardial procedure, there are three important points to consider:
1. Whether epicardial access should be performed in the first procedure, or should be scheduled after an unsuccessful endocardial approach;
2. Whether adequate technical conditions are present to perform the epicardial access procedure safely; and
3. Whether a review of clinical data and image evaluation exams could anticipate problems during the procedure.
In patients with ventricular arrhythmias referred to catheter ablation, clinical characteristics, image exams evaluation, ECG patterns,7 and results of previous procedures3 give us the probability of the subepicardial myocardial fibers as the source of origin in a given patient. Patients with structural heart disease and recurrent sustained VT related to nonischemic diseases, such as Chagas disease and dilated cardiomyopathy (excluding bundle branch reentry), usually have multiple morphologies and high probability of any associated epicardial VT.8 Substrate image evaluations, either by MRI with gadolinium and late enhancement or CT scan in patients with ICDs, are also useful for identifying epicardial substrate related to those arrhythmias. In patients with a high probability of epicardial source of origin, we usually schedule an epicardial mapping in the first procedure. Patients presenting with VT late after myocardial infarction with inferior scar,9 very wide QRS, pseudo–delta wave pattern, and prolonged deflection time index are also scheduled to the epicardial mapping in the first procedure. Patients with idiopathic VTs also can undergo epicardial mapping when the regular exploration at RVOT, aortic cusps, and CS and its branches3 were unsuccessful. The VT morphology on the ECG also helps to make this decision. Other patients are usually referred to epicardial mapping after an unsuccessful endocardial approach, mainly when adequate endocardial EP signals were not found in the first procedure.
Despite the subxiphoid epicardial access being a usually safe procedure and the rarity of severe complications, ventricular perforation and pericardial bleeding can happen, and the EP lab must be prepared for this complication. Then, just in case, it is important to have a cell-saver system to infuse the pericardial bleeding safely and a surgical team available.
Pericardial adhesions can make the pericardial access difficult or impossible. Then an echocardiogram or preferentially an MRI is useful to evaluate the status of pericardial membranes when evaluating the arrhythmia’s substrate. The knowledge of coronary anatomy is also required before the procedure (angiography, MRI, or CT scans). Based on VT 12-lead ECG, we can anticipate the plausible area that we will have to approach and estimate the risks for damaging coronary circulation during catheter ablation. During the procedure a new angiography will be performed again to confirm the safety for RF delivery. Liver and colon can be in risk of perforation during subxiphoid epicardial access. Clinical data and abdominal examination are important in order to identify patients with possible liver enlargement (heart failure) or colon dilatation (Chagas disease, idiopathic dilatation), and complementary evaluation with abdominal ultrasound, X-ray, or CT scan also may be useful for better investigation.
There are 2 main concerns when one decides to access the pericardial space through the subxiphoid approach. The first is how to make the puncture while avoiding injury to intraabdominal organs; the second is how to introduce the needle in such small pericardial space without promoting cardiac damage and pericardial bleeding.
When deciding to perform the subxiphoid puncture, it is important to remember that before reaching the pericardial space, the needle introduced through the subxiphoid approach will cross the upper peritoneal cavity, trespassing an area with potential risk of intraabdominal organ injury. Figure 45.2 shows a thoracic and abdominal sagittal CT scan view demonstrating the relationships between heart, liver, and transverse colon, the main intraperitoneal organs in risk of perforation when subxiphoid puncture is performed. The left lobe of the liver has a close relation to diaphragmatic aspect of the ventricles, and it is always in risk during such procedure, mainly when patient has heart failure and liver enlargement. The stomach and transverse colon are usually in a deeper position and are not in risk in normal conditions. When needle is positioned at 45° and puncture is performed laterally to the xiphoid appendix, close to the ribs, it usually will reach the cardiac border safely (Figure 45.3). However, there is a considerable risk of liver or even colon perforation if this angle is maintained and puncture is performed below this area. Thus, diminishing the angle of puncture to 30° or 15° is safer to avoid intraperitoneal structures (Figure 45.4). The problem is that the needle tip may hit the ribs if it is too close to the ribs’ border. To avoid this situation, it is important to compress the epigastric area with the left hand in order to create a space before performing needle penetration (Figure 45.5). In general, performing the puncture 1 to 2 cm from the rib border, with a small angle, makes possible a comfortable needle introduction, with low risk of intraabdominal injury. However, patients with significant colon dilatation present a considerable risk of perforation independently of the needle position. This is a common situation in South America, where Chagas disease is frequent and megacolon may be present in 10% of the patients referred for VT ablation. Figure 45.6A shows an example in which we were not able to perform a safe subxiphoid puncture because of a megacolon. For safety, we asked for a surgeon to introduce 2 sheaths in the pericardial space through a small subxiphoid window before we initiated the procedure.