Our study of 1500 consecutive CA procedures performed in a medium-volume center considers a large data set outside the high-volume centers, showing relatively low overall incidence of CA-related tamponade (0.8%), with no case fatality. Similar to the reports from high-volume centers, periprocedural tamponade in our center most commonly occurred with AF ablation (3.6%) [1, 2, 4, 6, 7].
Risk Factors for Tamponade
In our center, tamponade due to RF-CA was significantly more frequent in older patients, with pre-procedural oral anticoagulation, with a transseptal procedure, left-sided or AF ablation, with the use of irrigated-tip catheters and during the procedures with prolonged fluoroscopy. The only multivariable predictor of tamponade was AF ablation. Other reports additionally described VA ablation, female sex and the operator’s (in)experience as the risk factor for RF-CA major complications [2, 6, 12]. Specific risks of tamponade during AF ablation are: redo procedure, linear LA ablation and use of RF power >45 W [4, 12, 13].
The presumed mechanisms of perforation in our study were mechanical catheter manipulation, excessive tissue ablation and misdirected TSP. The use of a long steerable sheath improves catheter stability and ablation efficiency, but also enhances the catheter contact force to the tissue, increasing the risk of perforation . The application of contemporary contact force measurement technology may reduce the perforation rate during RFCA .
TSP guided only by fluoroscopy is complicated by tamponade in 0.1–3.2% of cases [5, 10]. ICE and TEE provide direct visualization of the septum and offer a safer TSP, especially in atypical anatomy, a resistant/elastic septum and inexperienced operators [16, 17]. Use of ICE during the AF ablation can provide many other potential benefits, such as the detection of LA thrombus or spontaneous echo-contrast formation, monitoring of catheter position and catheter-tissue contact, early identification of pericardial effusion during ablation, optimal RF energy titration and reduction of radiation exposure time [17–19]. However, routine application of TEE requires general anesthesia in many patients and may contribute to esophageal injury during AF ablation , while use of ICE increases the cost of the procedure .
More intensive anticoagulation and higher intracavital pressure increase the risk of tamponade during left-sided procedures . Therefore, it is not surprising that in our study the majority of tamponade cases occurred as a complication of a left-sided AF ablation.
Tamponade is the most frequent cause of fatal AF ablation outcome and is responsible for a quarter of all procedure-related deaths . It has been shown that AF ablation carries a significantly higher risk of perforation compared with other transseptal procedures, such as left-sided AP ablation or balloon mitral valvuloplasty . Dual transseptal access, prolonged LA catheter manipulation time, a thin LA wall, necessity of transmural and extensive ablation as well as irrigated-tip catheter use may explain a higher tamponade rate in AF ablation in comparison to other types of procedures in the present study. In comparison to RF conventional-tip catheters, externally irrigated-tip catheters create a deeper and wider lesion and increase the risk of tissue overheating and “steam-pop” [4, 13].
Perforation Predilection Sites
Thinned LA wall segments (the appendage, vestibular part of the mitral annulus, posterior roof), the RV apex and distal CS represent perforation predilection sites during EP procedures [5, 7, 23].
In a study of 15 patients with AF ablation-related tamponade, the LA was perforated in nine, the RV in five and the RA in one patient . Likewise, in our study, the LA perforation most frequently occurred during AF ablation (in 7 out of 10 patients with AF and tamponade). As opposed to other studies, there were no RV perforations in the present study, most probably because of the simplified catheter setup during AF ablation as well as the absence of a RV stimulating catheter. In our study, one procedure of typical AFL ablation led to RA perforation. Although the cavo-tricuspid isthmus ablation is one of the safest procedures, this complication has also been recognized by other authors .
Aggressive irrigated RF ablation, systemic anticoagulation and higher intracavital pressure are responsible for a significant risk of tamponade accompanying VA ablation [2, 8]. Additionally, the differences in the wall thickness are responsible for more frequent perforation of the RV as compared to the LV . In a series of 892 patients subjected to RFCA of VA, tamponade complicated 11 procedures (1.23%) . The laceration site was localized in the RV in seven, in the LV in only one and in three patients it remained undetermined. In the present study, there was only one tamponade due to VA ablation, this being an idiopathic VA in the LV basal inferior wall segment. It is possible that transaortic access to the LV inferior wall provides a greater contact force and perpendicular catheter tip orientation, predisposing the myocardium to perforation during RF . A low tamponade rate in the subpopulation of patients with VA (0.46%) could be explained by our practice of careful RF energy titration led by the impedance drop of ≤10 Ω. Namely, in VA ablation, the decrease of impedance ≥18 Ω was associated with a significantly more frequent occurrence of “steam-pop” and perforation .
Tamponade Management and Outcome
For pericardiocentesis, it is optimal to choose the shortest and safest route of the needle from the skin to the pericardium, the direction of the largest pericardial fluid accumulation and a technique the operator is most familiar with . In one study, the echocardiogram-guided apical approach was predominant (66.7%) , while in another study, the fluoroscopy-guided subxiphoid approach was mostly used (83.3%) , which is similar to our experience. In our study, subxiphoid access to the pericardium was achieved in the left lateral fluoroscopic projection, which clearly defines the path of the needle during puncture and best separates mediastinal, pericardial and myocardial structures . However, the subxiphoid access can be complicated by perforation of the RV, stomach, colon or liver [5, 7, 8]. Indeed, one of our patients underwent an urgent surgical abdomen exploration after pericardiocentesis because of suspected hollow organ perforation.
Life-saving pericardiocentesis can be performed via the transcardial approach, by the introduction of a long sheath over the catheter or by a needle through the myocardium into the pericardial space to achieve emergency drainage . After fluid evacuation, it is serially replaced with angiographic catheters of gradually smaller lumens until cessation of bleeding or surgical management . A similar experience in the present study was noted.
The probability of spontaneous bleeding cessation after pericardiocentesis depends on the site, size and geometry of the perforation, intracavital pressure and anticoagulation level . Continuous bleeding after pericardiocentesis requires urgent surgery. Previous studies have shown that only 13% of patients after atrial perforation and as much as 55% of patients after ventricular perforation underwent cardiac surgery [7, 8]. Similarly, in our study two (16.7%) patients were surgically treated after pericardiocentesis. In both cases the LA perforation caused tamponade. Since the number of AF ablation procedures is increasing, the necessity of intra-hospital cardiac surgery support is becoming an important issue. We believe that this should be emphasized because >50% of the centers currently perform AF ablations without in-house surgical back-up .
In the present study auto-transfusion was carried out in seven patients. Direct auto-transfusion is simple and requires no additional equipment; it may abolish the need for allogeneic blood transfusion and can “buy” time until surgery . However, direct auto-transfusion may cause systemic inflammation, and therefore the processing of the drained blood via the cell salvage system is recommended prior to its return . Auto-transfusion of a larger volume of blood, i.e., more than 1500 ml, may lead to consumptive coagulopathy [23, 25], which occurred in one patient in our study. In such circumstances, a timely replacement of coagulation factors and thrombocytes, an infusion of freshly frozen plasma or a whole-blood transfusion is necessary [23, 25].
In half of our patients with tamponade, the planned ablation set of lesions was completed despite perforation. In case of a smaller perforation, slow pericardial blood accumulation left sufficient time for the ablation to be completed before the development of tamponade; in another patient, a larger laceration led to massive hemorrhage and a sudden collapse soon after final “successful” RF application. Our study has also confirmed that ablation can be safely repeated after 4–8 months and, despite serious complications, in two-thirds of the patients it was possible to finally achieve arrhythmia elimination .
This study included a 5-year period, and the learning curve of individual operators might have significantly influenced the rate of complications. In addition, the mechanism and site of perforation in un-operated patients were determined indirectly. In our study, ICE and TEE were used in only 7.7% of transseptal procedures. It is possible that the routine use of ICE or TEE during the AF ablation procedure could significantly reduce the rates of cardiac tamponade and other mechanical complications. In the current study, AF ablation was performed with an interrupted warfarin strategy. Although an uninterrupted warfarin strategy reduces rates of thromboembolic stroke and minor bleeding in this setting, it deviates from the local surgical practice and has not been implemented in 40% of low-to-medium volume EP centers in Europe .