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The incidence of cerebrovascular events appears highest within 24 hours after transcatheter aortic valve replacement (TAVR), though it remains elevated for up to 2 months, according to results of a study published in the December 2011 issue of JACC: Cardiovascular Interventions. The authors suggest that this may have implications for patient selection and antithrombotic strategies.

Investigators led by John G. Webb, MD, of St. Paul’s Hospital (Vancouver, Canada), assessed 253 patients who underwent TAVR between January 2005 and November 2009. Assessments were performed at baseline, discharge, 1 and 6 months, and yearly for cerebrovascular events and death. Patients enrolled in the PARTNER trial were excluded from this study.

Risk Period Established

During the median follow-up period of 455 days, 23 patients experienced a cerebrovascular event (stroke or TIA). Patients who had a cerebrovascular event had a higher incidence of baseline cerebrovascular disease (48% vs. 20%, P = 0.007).

Most cerebrovascular events occurred within 2 months of TAVR (n = 20, 87%), of which half occurred with the first 24 hours of the procedure (n = 11). The early events were mostly ischemic strokes (n = 9), of which 2 occurred after documented episodes of prolonged hypotension requiring resuscitation during TAVR. TIA was seen in 2 patients.

Event incidence remained high through the first month (n = 6, 2.5%) and became lower in the second (n = 2, 0.8%). Late events were infrequent (n = 4).

As for predictors and risk factors of cerebrovascular events, patients who had early, in-hospital events trended toward higher mortality rates compared with those who did not (21% vs. 8%, P = 0.08). Twenty-three percent of patients had known prior cerebrovascular disease and more than one-third had atrial fibrillation. Other significant risk factors included:

• Smoking (47%)
• Hypertension (70%)
• Dyslipidemia (66%)
• Diabetes (25%)

Two thirds of patients (n = 168) were on clopidogrel—either a loading dose 6 hours before the procedure (n = 134) or a steady dose of 75 mg daily for more than 1 week (n = 34)—and 93% of patients (n = 234) were on aspirin before TAVR. Among patients who experienced a cerebrovascular event, 91% were on aspirin, 61% were on clopidogrel, and 35% were receiving antithrombotic therapy at the time.

A Clearer Picture of Procedural Risks

The findings are consistent with the already published PARTNER study and are the first to describe the timing and types of cerebrovascular events post-TAVR, note Dr. Webb and colleagues.

The details provided in these findings should aid clinicians in their treatment of the high-risk population of patients with a prior history of cerebrovascular disease. “These patients should be made aware of their risk during the consent process and managed with greater care,” the authors write.

In a telephone interview with TCTMD, Josep Rodés-Cabau, MD, of Laval University (Quebec City, Canada), said the current results “will help us to better understand the mechanisms associated with cerebrovascular events.”

In addition, Peter C. Block, MD, of Emory University Hospital (Atlanta, GA), told TCTMD in a telephone interview that the study’s findings “add to our database of what we can tell patients and what we can outline to help them make a decision about what they want to do.

“I think what John Webb and his group has done is a laudable bit of data collection,” he said. “They have shown what we have known intuitively since all of these data have come out for transcatheter valves.”

Still More to Determine

The biggest issue in the paper, Dr. Rodés-Cabau said, is similar to that seen in other papers on this topic. “The number of events is relatively low and you cannot really subdivide the events into early, acute, subacute, and late [categories],” he said. “Rather it’s a mix of events occurring acutely and during the follow up period, and I think that this can sometimes be a bit misleading.” He added that to better understand what is happening, the factors associated with event timing need to be better defined.

Because of the limited number of patients and the heterogeneous use of antiplatelet agents and vitamin K antagonists alone or in combination, the study authors conclude that they cannot determine which antithrombotic strategy is optimal. “With a more standardized antiplatelet/antithrombotic protocol in the future, a more meaningful comparison can be made with regards to their effect on preventing cerebrovascular events,” they write.

Dr. Rodés-Cabau added that the “complex population” of the study makes it difficult to assign a “uniform” antithrombotic treatment and that more data and research are needed to determine “individualized [treatments] depending on the characteristics of the patients.”

Proof that the stroke risk can be lowered with a different antithrombotic treatment would be the only pertinent finding, according to Dr. Block, for switching from the standard regimen.

“At the present time, no one has discussed or talked about or actually moved ahead to go to, for example, anticoagulation with coumadin [or] prasugrel instead of [clopidogrel] or any of the other antithrombin or antiplatelet agents,” Dr. Block observed. “We haven’t done that because the risk of stroke, although it has been important, has not yet been prohibitive.”

However, going forward new devices may show a decreased stroke rate based on their updated design alone, Dr. Block said. Even so, it is unrealistic to think that the stroke rate could ever be eliminated, as these events are “a fact of life” under these circumstances, he added.

“Some of the second-generation valves may have a lesser risk of stroke because they are designed differently,” Dr. Block concluded. “They may have much less stasis around them and therefore they may be far less able to produce sites for thromboembolism. But we still have to go across the transverse arch to deliver these catheter based valves and whenever you go across the transverse arch, there is risk. I can’t imagine you could get the stroke rate down to zero. Surgeons have a stroke rate of less than 5%, but they still have a real stroke rate.”

Study Details

The median age of all patients in the study was 85 years and 51% were men. The median STS score was 8.1%.

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