JACC Viewpoint: Studies Needed on Long-term Consequences of ‘Silent’ Cerebral Infarcts
As the scope of vascular procedures and technologies has broadened, imaging has revealed an increasing number of asymptomatic cerebral embolic complications. A viewpoint article published online September 19, 2012, ahead of print in the Journal of the American College of Cardiology suggests that these events deserve serious study since little is known about their potential long-term effects on cognitive function.
Several small studies have failed to link the presence of new lesions seen on diffusion-weighted imaging (DWI) following vascular procedures with clear neurological deficits. These silent DWI lesions typically are small (1-3 mm) but can be larger, according to Daryl R. Gress, MD, of the University of Virginia (Charlottesville, VA). In fact, multiple lesions per procedure are common, he writes, with 1 to 5 often described.
Dr. Gress adds that the literature suggests there are approximately 600,000 patients with new brain injury each year in the United States as a result of various procedures, including transcatheter aortic valve replacement (TAVR). By his estimate, TAVR claims the top spot as the procedure with the highest incidence of new brain lesions, followed by surgical aortic valve replacement (table 1).
Table 1. Procedures Associated with New Lesions on Imaging
Procedures |
No. of Annual US Patients |
Incidence of New Brain Lesions |
No. of Annual US Patients with New Brain Lesions |
TAVR |
10,000 |
68%-91% |
7,000-9,000 |
Surgical Aortic Valve Replacement |
|
|
|
CABG |
242,000 |
16%-51% |
39,000-123,000 |
CAS |
70,000 |
15%-67% |
11,000-47,000 |
Abbreviations: CABG, coronary artery bypass grafting; CAS, carotid artery stenting.
Other procedures potentially associated with new brain lesions include coronary angiography, PCI, atrial fibrillation ablation, carotid endarterectomy, cerebral angiography, and endovascular aneurysm. Together, these lesions may account for 13% to 24% of all new brain lesions in US patients, according to Dr. Gress. But he suggests that these figures may underestimate the true scope of the phenomenon and suggests that the occurrence of procedure-related asymptomatic lesions likely rivals clinical stroke, estimated at approximately 750,000 cases per year in the United States.
While conceding that vascular procedures and interventions provide important clinical benefits across a “vast section of predominantly older individuals,” Dr. Gress says data are accumulating to suggest that these new silent infarcts are much more frequent than previously thought and could pose a significant problem if they are found to be involved in accelerated cognitive loss and premature senescence.
“The eventual management of these risks will require multiple strategies, including improved pharmacological manipulation of clotting and platelet aggregation, safer device design and technique, and development of effective protection devices,” he writes.
Looking for Answers
Dr. Gress suggests that researchers should work to develop safer procedures with decreased risk of microinfarctions using DWI lesions as a marker. Furthermore, he believes clinicians are obligated to “take on the effort to study the long-term sequelae of these DWI lesions, recognizing that this is a monumental undertaking requiring extensive planning and expense.”
In a telephone interview with TCTMD, Peter C. Block, MD, of Emory University School of Medicine (Atlanta, GA), agreed with this assessment.
“There’s no question that we should pursue this and try to figure out whether or not these lesions are important,” he said. “From a practical standpoint we have not seen a lot of bad things happen as a result of them except for true strokes, which of course are always bad. It’s all still theoretical that these silent infarcts make a difference. It’s theoretical what that difference is, and the more we learn about it, everybody benefits.”
Dr. Block said the article is timely and appropriate for interventional cardiologists as well as cardiac surgeons because it may be time to stop accepting stroke rates of 2% to 3% for open aortic valve replacement and acknowledge that TAVR can lower those rates if operators properly “snare some of these thromboemboli” and potentially minimize new lesions going forward. “To me, that’s the exciting challenge here,” Dr. Block added. “We are being naïve to say [silent infarcts] don’t matter when in fact we have no proof of that.”
Bright Spots, Not Infarcts
In a telephone interview with TCTMD, Christopher J. White, MD, of the Ochsner Heart and Vascular Institute (New Orleans, LA), offered a slightly different perspective.
“It’s perfectly appropriate to raise the concern, but these are not infarcts,” he said. “These are ‘bright spots’ that we see on imaging that no one can explain. They are transient sometimes. I’ve seen them go away with serial imaging after carotid stenting. Now, certainly it would be inappropriate to stick our heads in the sand and not be aware of them, but raising concern about a potential problem is not the same as saying there is a definite problem when we know most of these are asymptomatic.”
Dr. White added that data demonstrate that new DWI lesions show up less frequently after carotid stenting when proximal protection is used as opposed to distal protection. “If we knew there was definite harm associated with these lesions, we would obviously always use proximal protection, but we don’t know that and sometimes [distal protection] is easier on the patient,” he said. “Without knowing how bad these things are I can’t say that I would change my clinical practice to avoid a few bright spots. Should we be thinking about it and asking questions and encouraging dialogue? The answer is yes. But we also need to be aware that everything in medicine is a trade-off. There are no absolutes.”
Dr. White said that while studying the issue as Dr. Gress suggests is important, researchers have to first determine if they are measuring a real endpoint or a surrogate. “It’s safe to say these [lesions] are not good things,” he concluded. “But I think we will find that while there are reasons to avoid having them happen, that is not sufficient to avoid doing a necessary procedure, like a bypass or carotid stenting.”
Source:
Gress DR. The problem with asymptomatic cerebral embolic complications in vascular procedures: What if they are not asymptomatic? J Am Coll Cardiol. 2012;Epub ahead of print.
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L.A. McKeown is a Senior Medical Journalist for TCTMD, the Section Editor of CV Team Forum, and Senior Medical…
Read Full BioDisclosures
- Dr. Gress reports serving on the scientific advisory boards of and holding stock options in Keystone Heart and Ornim Medical and serving as a consultant to Medtronic.
- Dr. Block reports no relevant conflicts of interest.
- Dr. White reports serving as the national principal investigator of the CABANA trial, which evaluated a filter device and was sponsored by Boston Scientific.
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