Risks of Cerebral Lesions & Cognitive Impairment: Living With A-Fib More Dangerous Than Having An Ablation

AF Symposium 2015

By Steve S. Ryan, PhD

Dr. Josef Kautzner of the Institute for Clinical and Experimental Medicine, Prague, Czech Republic gave a presentation entitled “Periprocedural Microembolization During AF Ablation—Mechanisms, Incidence and Clinical Significance.”

Dr. Kautzner’s agenda included demonstrating that living with “AF is more dangerous than its ablation.”

Silent Brain Lesions after Ablation?

Recent studies of mesh-type multielectrode catheters (not yet FDA-approved for use in the US) using MRIs of the brain have revealed silent cerebral ischemia—small lesions on the brain that don’t seem to produce any symptoms and tend to disappear over time. Worldwide experience suggests that small and medium lesions (less than 10mm) disappear at follow-up, while larger than 10 mm lesions remain. These larger lesions make up only a small proportion of the silent lesions found.

Dr. Kautzner pointed out that these silent lesions are common in many interventional procedures such as carotid artery stenting (37%) and TAVI (replacing the Aortic Valve) (68%-77%).

Though these small cerebral lesions don’t seem to cause symptoms, obviously doctors want to avoid creating any kind of lesions on the brain if at all possible.

Cognitive Dysfunction after Ablation?

In one study of “Post-Operative Cognitive Dysfunction (POCD)”, two days after standard ablations, about 25% of both paroxysmal and persistent patients experienced POCD, but by 90 days the POCD rates had dropped down to 13% of paroxysmal and 20% of persistent. No MRIs were done of these patients. (If this study had followed these patients for more than three months, the POCD rates for paroxysmal might well have dropped back down to near zero.)

Persistent patients had linear ablation lines added and ablation of complex fractionated electrograms (CFAEs). They also underwent more cardioversions during the procedure than paroxysmal patients. ¹

Silent Brain Lesions Before Ablation of Greater Concern

Of greater concern are the silent brain lesions which occur frequently before ablation. In MRI tests, a high proportion of A-Fib patients before ablation had silent cerebral infarctions or lesions (60%-80%). But the problem is that similar lesions were detected by MRI even in patients without documented A-Fib. Therefore, we still do not know how much A-Fib contributes to the development of such lesions. On the other hand, their presence may explain (at least in part) the association between A-Fib and dementia.

In one study 89% of paroxysmal and 92% of persistent A-Fib patients had at least one area of SCI (Silent Cerebral Ischemia). The number of SCI areas was higher in patients with persistent A-Fib. These silent brain lesions are associated with dementia. ²

Cognitive performance was significantly worse in patients with paroxysmal and persistent A-Fib than in controls in sinus rhythm. ³

How Silent Brain Lesions Develop During an Ablation

Dr. Kautzner described how these lesions might develop:

• Thrombi due to activation of the coagulation cascade after introduction of catheters. That’s why heparin and other anticoagulants are used before, during and after an RF ablation
• Particulate emboli (char)—making RF burns can potentially produce charring where small particles of heart tissue can break off and travel to the brain. This can be prevented by catheter cooling (irrigated-tip catheters) and prevention of tissue overheating
• Gaseous emboli (micro-bubbles) produced by air on sheaths/catheters or by heating/boiling of blood and heart tissue “steam pops.” Prevention—as above

Preventing Silent Brain Lesions During an Ablation

Dr. Kautzner described the procedures his center follows to prevent silent brain lesions:

• If CHA₂DS₂-VASc score of 0-1, no prior anticoagulation
• All others have uninterrupted warfarin (persistent have TEE before ablation)
• Aggressive heparinization from the beginning of the procedure, immediately after venous puncture
• Use of intracardiac echocardiography to monitor the procedure

The success of these strategies was documented in a study where DW-MRI and protein S100B testing were performed both before and the next day after the ablation. (DW stands for Diffusion Weighted Imaging MRI which is more sensitive in detecting small & early infarcts [lesions or tissue deaths]).

S100B testing checks the blood for calcium-binding proteins coming from the brain after a stroke. They predict post-ablation brain injury. In the example from Dr. Kautzner’s center, 1.7% of ablation patients had a new MRI lesion, while 5% had an increase of plasma S100B. (Plasma S100B testing seems to reveal more potential brain damage than an MRI and is certainly easier and cheaper to perform.)

Predictors of Post-Ablation Brain Injury Detected by Plasma S100B Testing

• Persistent A-Fib
• Procedure duration
• Cumulative dose of heparin (ACT—Activated Clotting Time)
• Cardioversion during the procedure
• Age
• CHA2DS2-VASC score
• Amount of RF burns. Patients who had a simple PVI ablation had fewer silent lesions than if linear lesions had to be made. If ablation for CFAEs had to be made, they had even more chance of silent lesions
• Single vs two transseptal punctures

Proposed Strategies to Minimize Risk of Silent Lesions

• Avoid interruption of anticoagulation before ablation
• Use TEE or ICE to detect any thrombus
• Systemic heparin from the beginning of the procedure
• Meticulous management of transseptal sheaths and catheters (including submersion of sheath assembly when loading with special catheters to avoid air bubbles on the sheaths)
• If using phased mesh RF catheters, avoid simultaneous activation of overlapping electrodes
• Consider avoidance of cardioversion during the ablation

Dr. Kautzner’s Conclusions

• Post-ablation asymptomatic cerebral microembolism can be detected with variable frequency
• Clinical consequences are unclear—some studies suggest possible cognitive decline
• On the other hand, there is much stronger evidence that atrial fibrillation is associated with a substantial risk of asymptomatic cerebral lesions and cognitive impairment
• Assessment of procedure-related brain damage (using DW-MRI or protein S100B) should become a standard for the monitoring of safety of novel technologies for ablation

Editor’s Comments:

A-Fib More Dangerous to Cognitive Ability than its Ablation: We are most grateful to Dr. Kautzner for his comprehensive study of A-Fib silent brain lesions. The bottom line is that there is inconclusive evidence that ablations produce lasting linear brain lesions and cognitive decline.

On the other hand, we know from many studies that A-Fib (before ablation) produces silent brain lesions in nearly 90% of cases and that these silent lesions are associated with dementia. Cognitive performance is significantly worse in people with A-Fib (both paroxysmal and persistent). As Dr. Kautzner says, “A-Fib is more dangerous than its ablation,” with regards to silent brain lesions and cognitive ability.

Importance and Frequency of Silent Brain Lesions: I, and I think most of the attendees, were surprised at how prevalent silent cerebral lesions were in patients with A-Fib, and how A-Fib patients have significantly worse cognitive performance. This is yet another reason not to leave patients in A-Fib, and for those of us with A-Fib to get treatment and/or an ablation as reasonably soon as possible.

S100B testing seems a great way to test for brain damage

S100B Testing: S100B testing seems a great way to test for brain damage after an ablation. Most centers (and insurance companies in the US) won’t routinely do an MRI after an ablation. But an S100B plasma test is more easily and cheaply performed, and may be more accurate than an MRI. But then the question for doctors and patients is what should be done if a S100B test comes out positive? If there are no brain damage symptoms, how concerned should we be?

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Last updated: Friday, November 25, 2016