This study reveals our single-center experience of epicardial ablation of VA with regard to two different puncture techniques, complication management and the incidence of pericardial adhesions during the initial epicardial puncture, as well as after multiple epicardial approaches. Major findings of this study were (1) a higher incidence of major complications when performing an inferior oriented epicardial puncture compared to an anterior oriented epicardial puncture (10.1% vs 4.9%; p = 0.16); (2) adhesion within the epicardial space of 9% during first and up to 47% in patients with two or more epicardial procedures (3) prolonged procedure parameters when performing an inferior epicardial access.
Correlation of complications within the two groups
Since Sosa et al. reported about their experience of successful percutaneous epicardial VT Ablation in 1997 in patients with Chagas disease [
3] the number of epicardial VT ablation procedures increased rapidly. For more than one decade the AP-guided inferior oriented epicardial puncture technique has been the gold standard in approaching the epicardial space, even though the risk of potential access related complications were high and well known [
4,
7]. Pericardial tamponade is still the most frequent complication in these procedures ranging from 6% up to 30% reported in the literature [
7,
17,
20]. In our patient cohort, the overall incidence of pericardial bleeding complications was similar (8.9%). In addition, several reports on complications like abdominal organ perforations or collateral damages of coronary arteries have been published over the last years [
7,
19,
21]. These complications were mainly observed while performing an AP-guided inferior-oriented puncture approach. In our cohort the incidence of major complications was 10.1% when performing an inferior epicardial approach. Comparison between the above-mentioned studies and our results are difficult since most reports did not differentiate explicitly between puncture-related and overall procedural complications. However, we also observed a not negligible number of severe abdominal collateral damages. In 5 patients (2.6%) perforations or accidental punctures of the liver, colon or gastric vessels occurred with the necessity of emergent surgery. We did not observe these complications at all when performing an anterior epicardial access approach with additional LAO 90° fluoroscopical guidance. There might be different reasons for this observation: First, during anterior epicardial access approach the needle is advanced right below the sternum after subxiphoidal puncture in a shallow angle. Therefore, it may enter the fibrous pericardium without penetrating the diaphragm with a lower risk of vessel injuries on the one hand, and without any other adjacent organs on the „pathway “ between the subxiphoid puncture side and pericardial access side (Fig.
2). Additionally, early imaging studies from the 1980s reported that pericardial fluid distribution in the supine position is mostly located anterior [
22], which may facilitate a less difficult dry puncture performing an anterior epicardial puncture compared to a posterior access approach into the epicardial space. Nonetheless, the most common complication in our patient cohort was pericardial bleeding and consecutive tamponade. Interestingly, a previous study by Keramati et al. reported about no pericardial bleeding complications (> 80 ml blood) after LAO guided and anterior-oriented puncture and no emergent cardiac surgery or procedure-related mortality [
13]. Even though we observed pericardial bleeding in 4 patients (4.9%) in the anterior epicardial group, we also did not experience any need for emergent cardiac surgery or procedure-related mortality. However, patients in the study mentioned above suffered from ARVC in a certain proportion and may have had less comorbidities compared to our patient population. The authors also state that they did not perform endocardial mapping in all patients and consecutively did not heparinize them.
Complication prevention and management
Besides the observation of specific complications arising from the two epicardial puncture techniques, some general considerations seem to be relevant, that may help avoiding complications. A preprocedural abdominal sonography can be a helpful tool to discriminate the dimensions of the liver, especially in patients with acute decompensation of heart failure. In these cases, a more lateral puncture site, guided by previous sonography findings, might be reasonable.
In patients with iatrogenic injury of abdominal organs, symptoms like abdominal pain began on average 6–8 h after cessation of the procedure. This underlines the necessity of careful monitoring, even in patients initially stable and asymptomatic after the procedure. Abdominal sonography for organ injury and free fluids can be a useful tool for efficient bedside examination and early diagnosis if abdominal organ injury is suspected, while an abdominal CT-scan represents the most accurate and sensitive diagnostic instrument. Another important issue seems to be the risk of accidental puncture of the RV, which does not necessarily result in severe bleeding complications if the sheath has not been advanced into the RV completely. To overcome the risk of bleeding complications after accidental puncture of the RV, several groups analyzed different techniques and tools [
7,
23]. One important tool can be the use of a micropuncture needle (needle in needle technique) [
9,
24]. A LAO guided anterior-oriented puncture technique performed with a micropuncture needle might be a beneficial combination to prevent RV puncture, even though radiation exposure is particularly high for the operator when using a LAO 90° angulation.
An aggravating factor in this context might be anticoagulation management. The risk of severe bleeding complications can overweigh the risk of thrombus formation. Therefore, if anticoagulation is needed, the possibility of administration after completed epicardial puncture should always be considered thoroughly and on an individual base.
Furthermore, in situations of severe bleeding events a standardized complication management protocol can be essential and lifesaving. The majority of patients suffering from bleeding complications did not require complex open-heart surgery, as bleeding terminated while the patients were stabilized using our coordinated algorithm. One patient of our cohort underwent emergent cardiac surgery due to massive thrombus formation within the pericardial space after antagonization of heparin with protamine and additional administration of fibrinogen. Therefore, we would recommend a careful administration of sole protamine performed only under simultaneous flushing of the epicardial space (with non-heparinized saline) and consecutive aspiration. However, this complication algorithm has to be evaluated prospectively.
Simultaneous endocardial mapping was performed during most of the epicardial ablation procedures. Inappropriate mapping and/or transseptal puncture during endocardial mapping, as well as coronary perforation are possible additional causes of pericardial tamponade. In these situations, blood-gas analysis to identify saturated from unsaturated blood within the epicardial space may help differentiating a RV perforation from a LA or left ventricle perforation.
Another important factor in complication prevention is the operator experience in these high risk procedures. Even though we observed a reduction of complications over the study time and some operators at our institution gained more experience, it must be taken into account that there was fluctuation among the operators over the period of almost fifteen years and the analyzed procedures were carried out by different interventionalists. Due to this fluctuation and the high number of different invasive electrophysiologists performing epicardial VT ablation procedures at our high-volume center, the influence of the experience of the individual operator on the overall complication rate appears very small compared to the puncture technique in general.
Epicardial access after multiple procedures and adhesions
Even after reducing the risk of major complications with all available techniques and tools, many factors, like comorbidities and patient selection influence procedural safety. Limited access to the epicardium due to adhesions can also increase the risk of complications [
14]. Adhesions after prior cardiac surgery are almost universal and the only attempt for an anterior oriented access within this subgroup failed, most likely since post-surgery adhesions usually concern the anterior or lateral pericardium. Less is known about the prevalence of adhesions in patients without previous cardiac surgery or a history of perimyocarditis. A recent study reported about 155 epicardial procedures with 8% adhesions after the first and 13% after the second epicardial ablation [
15]. Our data are in line with the findings concerning de novo adhesions, but the incidence of adhesions in repeated epicardial procedures was distinctly higher in our cohort. However, the periprocedural risk increases when having adhesions and may require blunt dissection of adhesions with a steerable sheath or even a surgical creation of a pericardial window and manual dissection of the adhesions by the hand of the cardiac surgeon. A blunt dissection of adhesions with a steerable sheath increases the risk of bleeding complications in theory but has not been investigated systematically so far. Taking all this into consideration a critical use-risk analysis should be performed prior to every epicardial ablation, especially before repeated approach for epicardial access in the same patient.
Limitations
This was a retrospective study with its typical limitations. Our analysis contains only cases of intrahospital complications and mortality without further follow-up. Further studies are necessary to prospectively evaluate these results. More importantly, AP guided inferior-oriented puncture was initially used and changed to LAO guided anterior-oriented puncture after gaining more experience and knowledge about epicardial puncture and potential complications. Nevertheless, our analysis is to our knowledge the first study in a large patient cohort comparing these two epicardial puncture techniques.