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Incidence and significance of adhesions encountered during epicardial mapping and ablation of ventricular tachycardia in patients with no history of prior cardiac surgery or pericarditis
Pericardial adhesions can prevent epicardial access and restrict catheter movement during mapping and ablation of ventricular tachycardia (VT). The incidence of adhesions in patients without prior cardiac surgery or clinically evident pericarditis is not known.
Objective
To describe the incidence of pericardial adhesions and explore their impact in patients without prior cardiac surgery or pericarditis.
Methods
A retrospective search of our ablation database containing patients who underwent epicardial ablation for VT was undertaken. Adhesions were diagnosed with routine contrast pericardiography after pericardial entry. Demographics and long-term outcomes were compared between patients with and without adhesions.
Results
Between 2004 and 2016, successful epicardial entry was achieved in 188 of 192 attempts (98%). In 155 first-time epicardial access attempts, pericardial adhesions were diagnosed in 13 (8%). When comparing baseline demographics, there was no significant difference. However, adhesions tended to occur more frequently with severe renal impairment (2% of patients without adhesions vs 15% of patients with adhesions, P = .07). No patient with a structurally normal heart had adhesions present. Adhesions were associated with limited epicardial mapping (3% of patients without adhesions vs 85% of patients with adhesions, P < .001) and lower short-term procedural success (68% of patients without adhesions vs 46% of patients with adhesions, P = .02), but complication rates were similar. The presence of adhesions did not translate into lower VT-free survival (P = .64) or freedom from a combined end point of VT recurrence, death, or transplant at 1 year (P = .93).
Conclusion
Adhesions may be unexpectedly encountered in patients without prior cardiac surgery or pericarditis. When present, they can limit mapping and may be associated with lower short-term success. Larger studies are required to determine their impact on long-term outcomes.
Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): a multicentre randomised controlled trial.
has improved our ability to treat patients when endocardial ablation has failed because of a predominantly epicardial substrate. Epicardial access can be achieved in most patients, and catheters can usually be maneuvered without restriction.
However, the presence of pericardial adhesions, usually attributed to prior pericarditis or cardiac surgery, can interfere with catheter movement in the epicardial space.
Percutaneous access of the epicardial space for mapping ventricular and supraventricular arrhythmias in patients with and without prior cardiac surgery.
Whereas adhesions after cardiac surgery are nearly a universal finding, the incidence and impact of adhesions in patients undergoing a first epicardial procedure with no prior clinically evident pericarditis or prior cardiac surgery is not known. Further, little is known about the risk of pericardial adhesions after previous epicardial mapping and whether factors such as use of pericardial contrast injection or pericardial bleeding during the index case affect the likelihood of successful repeat epicardial access. Therefore, the aim of this study was to identify the incidence of adhesions in patients without prior pericarditis or cardiac surgery who were undergoing first-time and repeat epicardial procedures and to evaluate their effect on short-term and long-term outcomes.
Methods
Patient population
The participants in this study comprised consecutive patients of age >18 years who underwent catheter ablation of ventricular tachycardia (VT) via percutaneous epicardial access. Exclusion criteria were documented prior cardiac surgery or those with a prior history of clinical pericarditis. The etiology of structural heart disease was established according to conventional diagnostic criteria, and patients were imaged preprocedurally with cardiac magnetic resonance imaging or transthoracic echocardiography or both. Where possible, antiarrhythmic drug therapy was withdrawn 5 half-lives prior to the procedure except in those patients on amiodarone. The study was approved by an institutional review board.
Epicardial access technique and identification of adhesions
The decision to perform epicardial access was based on one of the following: electrocardiogram of the clinical tachycardia suggestive of an epicardial origin, preprocedure imaging or cardiac etiology suggestive of epicardial substrate, prior failed endocardial ablation procedure, or “no entry” left ventricle (LV) (eg, LV thrombus). All information regarding epicardial puncture, the presence of adhesions, and impact of adhesions on mapping were documented in detail in the procedure reports.
Access to the pericardium was usually obtained prior to the administration of systemic anticoagulation in accordance with institutional protocol.
The right anterior oblique projection was used to direct access in the anterior/posterior plane, and the left anterior oblique was used to direct the needle (17-gauge Tuohy) leftward tangentially to the cardiac silhouette. After pericardial entry, a guidewire was advanced to the left heart border in the left anterior oblique projection, and 10 mL of contrast was injected into the pericardial space through a soft-tip 5F dilator to allow for visualization of adhesions (Figure 1 and Video 1). An initial aspirate through the 5F dilator was performed for early detection of pericardial bleeding.
Figure 1Visualization of adhesions on biplane fluoroscopy after contrast pericardiography. The J-tipped guide wire can be seen to buckle in the presence of adhesions, which are highlighted by contrast pooling (dashed line). CS = coronary sinus; His = His catheter; LAO = left anterior oblique; Quad = quadripolar catheter; RAO = right anterior oblique.
We defined a failed access as failure of entry into the pericardium sufficient to enable contrast injection into the pericardial space. The presence of adhesions was diagnosed by any of the following: failure to advance the wire freely in the pericardial space, appearance of nonuniform contrast pooling, or resistance to catheter movement during mapping. In cases where dense adhesions at the access site prevented sheath insertion, discretionary attempts were made to enter the pericardium at an alternative site either during the same procedure, or at a later date if trauma from the initial attempts was considered problematic (Figure 2 and Video 2). The locations of adhesions were documented from retrospective review of biplane fluoroscopic images.
Figure 2Fluoroscopic images of an epicardial access that was initially unsuccessful due to adhesions requiring a separate apical puncture to gain access. A and B: Staining of pericardium marks the initial unsuccessful puncture site 1. Contrast pooling and wire buckling confirms presence of adhesions. C: Corresponding 3-dimensional geometry in orthogonal views of the same patient, demonstrating incomplete epicardial geometry creation due to adhesions. D: Voltage map of the mapped epicardial surface (0.5–1.0 mV). LAO = left anterior oblique; LL = left lateral; LV = left ventricle; RAO = right anterior oblique.
A SL-0 sheath (St Jude Medical, St Paul, MN) or a bidirectional steerable sheath (Agilis, St Jude Medical, St Paul, MN) was then inserted into the pericardial space. Whenever an ablation catheter was not present in the sheath, an alternative mapping or angiographic catheter (Berman wedge) was always placed inside the sheath to avoid trauma from an exposed sheath tip. In most cases, the pericardium was double-wired to retain pericardial access in the event of inadvertent loss of the primary access.
At the conclusion of the procedure, any fluid present was withdrawn from the pericardial space, as verified by intracardiac echocardiography. Methylprednisolone 250 mg was then instilled. If >20 mL of blood was aspirated, a pigtail drain was retained overnight. All patients underwent transthoracic echocardiography prior to pericardial drain removal.
Mapping and ablation
Our strategy for ablation of scar-mediated VT at our center has been previously reported.
Epicardial mapping was usually undertaken at the start of the procedure to minimize the duration of full anticoagulation. High-density electroanatomic maps were created using established cutoffs for scar with CARTO (Biosense Webster, Diamond Bar, CA) or NavX (St Jude Medical, St Paul, MN). Mapping was performed with a multipolar catheter (2-2-2 duodeca [Livewire, St Jude Medical, St Paul, MN] or the 5 spline 20-pole PentaRay [Biosense Webster, Diamond Bar, CA]) or with a conventional open-irrigated ablation catheter at the operator’s discretion. All sites displaying abnormal, fractionated, or late electrograms were tagged. If adhesions that were believed to impede access to an area of interest were encountered, gentle mechanical adhesiolysis could be undertaken. The method of adhesiolysis has been described previously.
The catheter tip was deflected and undeflected while the shaft was advanced or retracted with or without the aid of a deflectable sheath. However, if adhesions could not be disrupted with gentle efforts, no further attempt was made. Mapping was defined as limited if the presence of adhesions prevented the catheter form being maneuvered to an area of interest, or if pericardial bleeding during the procedure thought to be secondary to adhesiolysis prevented continued mapping or ablation (Figure 2). If initial pericardial entry was successful, allowing pericardiography and catheter placement, and then severely restricted catheter movement was encountered, epicardial mapping was defined as abandoned after successful access. Ablation was performed epicardially at sites with late potentials, at sites with pace mapping match >10 of 12 leads, at sites with diastolic activation during tachycardia, or in the case of focal VT, at the site of earliest activation. Prior to ablation, coronary angiography and high-output pacing were performed to avoid ablation near coronary arteries or the phrenic nerve. Radiofrequency lesions were applied for 60 s at 30–50 W using an open or closed-loop irrigated ablation catheter (ThermoCool, Biosense Webster, Diamond Bar, CA; FlexAbility, St Jude Medical, St Paul, MN; Chilli, Boston Scientific, Natick, MA). Following ablation, programmed stimulation was performed, and further VTs were targeted at the discretion of the operator. Short-term success was defined as complete noninducibility after programmed stimulation with ≤3 extrastimuli down to 200 ms or refractoriness from the right ventricle (RV) and LV, partial success if the clinical VT was noninducible, and failure if the clinical VT was inducible at the end of the procedure.
Echocardiography
In patients identified to have adhesions during the procedure, a review of preprocedure echocardiography was undertaken to determine whether it was possible to identify the presence and location of adhesions. Images of sufficient quality to delineate the epicardial surface from the pericardium were reviewed by 2 experienced cardiologists. All standard views were screened for the presence of a pericardial effusion >0.5 cm, loculations and fibrinous stranding, and tethering—defined as the lack of independent movement of the parietal and visceral pericardium in a circumscribed area giving the appearance of 1 surface being pulled by the other (Video 3).
Follow-up
All patients were followed up at 1, 3, 6 and 12 months post procedure if they were followed up at our institution. For patients followed up elsewhere, clinical follow-up was based on records from referring physicians or direct phone conversations with the patient. The primary end point at follow-up was freedom from sustained VT requiring implantable cardioverter defibrillator therapy. A secondary end point comprised a combination of VT recurrence, transplant/ventricular assist device (VAD) implantation, or death. Major procedure-related complications were defined as any short-term adverse event within the index admission that lead to escalation of care or delayed inpatient stay post procedure and were categorized as intraprocedural and postprocedural complications.
Statistical analysis
The distribution of continuous variables was assessed for normality using the Shapiro-Wilk test. Comparisons between groups of continuous data were performed by t test after controlling for equality of variance with the Levene test. Nonnormal distributed variables were analyzed with Mann-Whitney U test and categorical data were compared with the Fisher exact test. Event-free survival was examined using the Kaplan-Meier method and significance determined by the log-rank test. For the time to event analysis, only the time to the first event was considered, after which the patients were censored. Where patients had repeat procedures, only the first procedure was considered in the analysis. Statistical significance was set at 2-tailed P < .05. Analysis was performed with SPSS Version 22 (IBM, Armonk, NY).
Results
Between 2004 and 2016, 416 VT ablations were undertaken at our institution. Of these, 234 procedures (56%) in 201 patients had combined endocardial and epicardial mapping and ablation. Of the 234 epicardial procedures, 192 procedures (82%) in 163 patients utilized the percutaneous approach and 41 procedures (18%) required surgical access.
Incidence and predictors of adhesions
Pericardial entry was achieved in 188 of 192 percutaneous procedures (98%). Of the 4 that failed, 3 failures were due to traumatic access attempts and the other due to a lacerated left internal mammary artery. Of the 188 procedures in which successful epicardial access was achieved, 155 were first-time pericardial punctures. Among these, adhesions were present in 13 (8%) (Figure 3). The remaining 142 procedures with no adhesions and no prior epicardial procedures made up the control group.
Figure 3Flowchart showing the incidence of adhesions at first epicardial access.
Patient demographics of the 2 groups are shown in Table 1. There was no significant difference in baseline characteristics between the 2 groups. However, patients with adhesions tended to have a higher proportion of severe renal impairment (2% vs 15%, P = .07). It was notable that no patient with a structurally normal heart had adhesions. Furthermore, no patient in the adhesions group had a prior diagnosis of a systemic autoimmune condition.
Effect of adhesions on procedure and long-term outcomes
Of the 13 cases of de novo adhesions, 11 had fluoroscopy images available for review. Adhesions were located in the midapical inferior LV in 3, the inferior RV and inferolateral LV in 2, the anterior RV in 2, the basal and midinferolateral LV in 2, and the apical inferior region in 1, and they were patchy and diffusely distributed in 1.
Procedural data for the 2 groups are shown in Table 2. Of the variables assessed, the presence of adhesions was significantly associated with limited epicardial mapping (3% vs 85%, P < .001). The extent of limitations comprised incomplete mapping in 4 (31%), severe restriction of catheter movement after successful pericardial entry necessitating abandonment of epicardial access in 5 (38%), and bleeding in 2 (15%), which was due to traumatic epicardial access attempts in 1 and adhesiolysis in the other. In the no-adhesions group, epicardial mapping was limited by bleeding in 4 (3%). Adhesiolysis was performed in 2 of 13 and was successful in facilitating access to areas of interest.
Table 2Procedure-related data
No adhesions, n = 140
Adhesions, n = 13
P value
Ablation indication, n (%)
Symptoms
20 (14)
1 (8)
NS
ICD therapy
62 (44)
6 (46)
VT storm
59 (42)
5 (46)
Epicardial access limited, n (%)
4 (3)
11 (85)
<.001
Reason
Limited mapping—adhesions
NA
4
Access abandoned—adhesions
NA
5
Bleeding
4
2
Induced VT, median (IQR)
1 (2)
1.5 (3)
.93
Mechanical circulatory support, n (%)
RF number, median (IQR)
26 (31)
31 (28)
.20
RF time, s, median (IQR)
1398 (1568)
1150 (1449)
.35
Procedure time, min, mean (SD)
387 (134)
401 (373)
.39
Fluoroscopy time, min, median (IQR)
72 (42)
92 (101)
.36
Outcome, n (%)
Complete success
97 (68)
6 (46)
.02
Partial
31 (22)
2 (15)
Failure
14 (10)
5 (38)
Procedure-related complications
Total, n (%)
17 (12)
3 (19)
.38
Intraprocedural:
8 (6)
3 (19)
Tamponade
4 (3)
2 (13)
AV block
1 (1)
0
Device lead displacement
0
1 (6)
Intraprocedure-sustained deterioration
1 (1)
0
Transient phrenic nerve palsy
2 (1)
0
Post procedure:
9 (6)
0 (0)
Heart failure/cardiogenic shock
8 (6)
0
CVA
1 (1)
0
CVA = cerebrovascular accident; ICD = implantable cardioverter defibrillator; IQR = interquartile range; NA = not applicable; RF= radiofrequency; SD = standard deviation; VT = ventricular tachycardia.
The presence of adhesions appeared to translate to differences in short-term outcome, with 68% vs 46% achieving complete success, 22% vs 15% partial success, and 10% vs 38% failed procedures in the absence and presence of pericardial adhesions, respectively (P = .02). Reasons for failure in the adhesion group were bleeding in 2, an intramyocardial focus in 1, and restricted access to an area of interest in 1. In the no-adhesion group, procedural failure was documented to be due to bleeding in 2, an intramyocardial focus in 1, proximity to a coronary artery in 7, noninducibility combined with lack of substrate in 3, and sustained hemodynamic deterioration in 1.
Overall complication rates were similar when comparing the 2 groups 12% vs 19% (P = .38). However, there tended to be a higher proportion of intraprocedural complications, mainly because of pericardial effusions requiring removal of fluid through the sheath when causing an adverse hemodynamic effect, in the adhesions group (6% vs 19%).
Median follow-up for the study population was 365 days (interquartile range [IQR] 747). One-year event-free survival from the primary end point of VT recurrence between the 2 groups was not statistically different (P =.64) (Figure 4). Further, using a combined secondary end point of VT recurrence, VAD implantation/transplant, or death, no difference was seen between groups (P = .93) (Figure 5). At 1 year, 59 (41%) vs 4 (31%) had VT recurrence, 19 (13%) vs 2 (15%) had died, and 3 (2%) vs 1 (8%) had VAD implantation or had heart transplant when comparing the no-adhesions vs adhesions group, respectively.
Figure 4Kaplan-Meier curve of ventricular tachycardia–free survival in the presence and absence of adhesions.
Figure 5Kaplan-Meier curve for the combined end point of ventricular tachycardia recurrence, transplant/ventricular assist device implantation, or death.
Repeat access after a single epicardial procedure was performed in 26 patients at a median of 97 days (IQR 469) (Figure 6). Of these patients, repeat access was performed in 3 patients who had adhesions on the index epicardial procedure. Access was obtainable in all 3 instances, of which 1 case had a prior failed access, which was overcome by using an apical approach. Successful access led to short-term procedure success in all 3 cases, but with limited mapping area; however, this limited mapping did not restrict access to critical regions of interest. In 23 patients with no prior adhesions, 3 had developed new adhesions by second access; all 3 had received intrapericardial methylprednisolone at the previous procedure. In these 3 cases, short-term success was achieved without complication, despite a limitation of catheter movement to noncritical areas in 2 cases and eventual abandonment of epicardial access in the other, with successful endocardial ablation. Only 2 patients underwent 3 epicardial punctures, of which 1 had developed adhesions. Low numbers of procedures precluded meaningful evaluation of variables associated with the development of adhesions. However, estimated pericardial bleeding ≥100 mL and pigtail placement at the prior procedure was documented in 1 of 4 patients who subsequently developed adhesions compared with 2 of 21 with no adhesions. Furthermore, there was no statistical difference in the median time since previous epicardial access: 87 days (IQR 443) for no subsequent adhesions vs 244 days (IQR not applicable) for adhesions. In addition, there were no significant differences in procedure duration or radiofrequency ablation time between patients who subsequently developed adhesion and those that did not.
Figure 6Flowchart demonstrating the incidence of adhesions after repeat epicardial access.
Twenty preprocedure echocardiograms were available for review in patients with confirmed adhesions. Insufficient delineation of surfaces was present in 4 scans. No significant pericardial effusion was seen in any of the scans. In the absence of an effusion, it was not possible to identify loculations. However, the appearance of tethering where the visceral and parietal pericardium were adhered together at a focal point was seen in 3 scans and only on long-axis views.
Discussion
The main finding from this study is that the incidence of pericardial adhesions in patients with no history of pericarditis or cardiac surgery undergoing a first epicardial puncture is 8% overall. When adhesions are present, they lead to difficulties in mapping in 85% of procedures and are associated with higher rates of short-term procedural failure when compared with those of procedures without adhesions. On a second epicardial access, adhesions were found in 13% of patients with no prior adhesions. Subsequent epicardial access in patients with prior adhesions was achievable with an acceptable short-term outcome.
To our knowledge, this is the first study to document the presence of adhesions and describe their impact on procedural and long-term outcomes for ablation of ventricular arrhythmias in patients with no history of clinical pericarditis or cardiac surgery. Epicardial access for ablation of VT is achievable in 75%–100% of patients in the reported case series, but when attempts to access have been unsuccessful, the failure has been attributed to pericarditis and previous cardiac surgery.
Percutaneous access of the epicardial space for mapping ventricular and supraventricular arrhythmias in patients with and without prior cardiac surgery.
There are limited data on the predictors of adhesions in patients without prior cardiac surgery. In our study, the small number of patients in the adhesions group meant that statistical analysis was underpowered, but it was notable that no patient without structural heart disease was found to have adhesions. Furthermore, patients with a prior diagnosis of myocarditis appeared to be equally distributed. Of the variables that were examined, only severe renal impairment tended to be more frequently associated with the presence of adhesions, possibly because of asymptomatic chronic uremic pericarditis. Further, although patients did not have overt clinically evident pericarditis, it is possible that subclinical pericarditis may have occurred in some patients.
Several case series have examined the impact of adhesions on epicardial ablation in postsurgical patients. One study of 10 patients with prior noncoronary artery bypass surgery or pericarditis reported that blunt dissection with a steerable sheath allowed successful mapping in 90%, with a short-term success rate of 80% and a complication rate of 10%.
In a subsequent study of epicardial access in 18 patients with prior cardiac surgery, including coronary surgery in 10, successful access was obtained in 67% and short-term success achieved in 72% with mechanical adhesiolysis. In that study, a complication rate of 22% was seen.
In our institution, we have opted for surgical epicardial access as the initial approach in patients with prior cardiac surgery. Our series shows significantly more short-term procedural failures in the presence of pericardial adhesions. Attempts were made to mechanically disrupt adhesions in 2 cases, resulting in bleeding in 1, and so further attempts were limited because of unfavorable risk-to-benefit ratio when operators considered that potentially major complications could result.
In the case in which bleeding occurred, a deflectable sheath was used to perform adhesiolysis, and it is possible that excessive force generated by the sheath vs a catheter alone may have been contributory. Furthermore, it is routine at our center to perform epicardial access and mapping prior to endocardial mapping and ablation. Therefore, any bleeding encountered during epicardial access prevented heparinization for endocardial mapping. This may partly account for the number of short-term failures in the adhesions group. In other centers, endocardial mapping is performed prior to epicardial access and therefore anticoagulation can be safely reversed prior to epicardial puncture. Despite a high rate of short-term procedural failure in the adhesion group, the presence of adhesions did not translate to poorer 1-year outcomes, but this finding could be due to the small numbers involved in the analysis.
One study has examined the feasibility and implications of repeat epicardial access among 30 patients requiring a second epicardial procedure.
At the second procedure, adhesions were encountered in 23% of their cohort, although it was not reported whether those patients had prior adhesions at the first epicardial procedure. Analysis of factors related to the development of adhesions after a first procedure was not significantly related; such factors included initial traumatic puncture, amount of ablation, and administration of intrapericardial steroids. In our experience, 13% of patients developed adhesions after a first epicardial procedure. Although mapping was limited in these patients, short-term procedural success was achieved in all 3 cases without complication. In addition, the presence of adhesions at the first procedure did not necessarily prevent a second epicardial attempt, providing an alternative puncture site was selected.
Since percutaneous epicardial access for ablation was established at our institution, it has been protocol to perform contrast pericardiography to detect adhesions and to anticipate difficulties with mapping. However, this is not established practice at all centers, because of a lack of data supporting its use to date and partly because of concerns that contrast may act as a caustic agent and promote the development of adhesions. Although numbers were limited in our study, the proportion of newly developed adhesions remained low (8% de novo vs 13% on repeat procedures). Even if contrast does promote the development of adhesions, the combination of serial dilution with catheter irrigation fluid and repeated aspiration together with removal of fluid at the end of the procedure may minimize this risk. Although no randomized data support our protocol, we believe that it may help to avoid complications that may be associated with unexpected adhesions.
The ability to identify adhesions preprocedure has benefits with regards to procedural planning and access approach. Although we could deduce their presence indirectly by the appearance of tethering on echocardiography, this observation could only be achieved in patients with good echocardiographic windows and sufficient long axis ventricular function to be able to visualize this phenomenon which will likely limit its use. However, it is possible that dedicated views and prospective scanning may be able to increase the sensitivity. Magnetic resonance imaging also has the ability to identify tethering using dynamic tagging, which may be an alternative modality to identify the presence of adhesions.
This was a retrospective study involving a small cohort of patients undergoing epicardial access at a single institution, thereby limiting statistical analysis. Although contrast pericardiograms were performed in every case, it is possible that adhesions may have been missed if contrast was unevenly distributed in the pericardial space. When adhesions were encountered, the decision to attempt mechanical disruption and to abandon epicardial access was discretionary. Therefore, it is unknown whether a more aggressive strategy would have led to improved outcomes. Because of the retrospective nature of the study, documented morphology of implantable cardioverter defibrillator electrograms for VT episodes post ablation compared with those seen during the VT ablation procedure was not possible. It was therefore unclear whether the recurrence was due to the prior documented clinical VT.
Conclusion
Adhesions can be found in a small proportion of patients with no prior history of clinically evident pericarditis or cardiac surgery undergoing first-time epicardial ablation. When they are present, mapping is often limited without aggressive attempts at mechanical adhesiolysis, and the presence of adhesions may be associated with poorer short-term outcomes. However, larger series are required to determine the impact of adhesions on long-term outcomes.
Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): a multicentre randomised controlled trial.
Percutaneous access of the epicardial space for mapping ventricular and supraventricular arrhythmias in patients with and without prior cardiac surgery.
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