Half of Strokes Early After TIA Occur Within 24 Hours

Susan Jeffrey

June 04, 2009

June 3, 2009 — A new study shows that nearly half of all strokes that occur after a transient ischemic attack (TIA) occur within the first 24 hours, highlighting the need for emergent intervention, the researchers say.

The good news is that the ABCD2 score, a validated risk score, was reliable in this hyperacute phase, meaning that "appropriately triaged emergency assessment and treatment are feasible," the researchers, with senior author Peter M. Rothwell, MD, from the Stroke Prevention Research Unit at Oxford University and John Radcliffe Hospital, in the United Kingdom, conclude.

This is the first rigorous population-based study of the risk for recurrent stroke within 24 hours of TIA, Dr. Rothwell told Medscape Neurology. "We found that nearly half of all the strokes that occur within 30 days after a TIA actually occur within those first 24 hours, so unless we intervene more quickly and treat it as a true emergency, rather than a 'see-urgently' problem, we'll miss the opportunity to prevent some of those early recurrent strokes," he said.

The results, reported on behalf of the Oxford Vascular Study, are published in the June 2 issue of Neurology.

Risk Underestimated

Over the past few years, Dr. Rothwell's group and others have been examining the natural history of TIA and minor strokes, looking at extent to which the early risk for recurrent stroke has been underestimated in the past and trying to determine how best to prevent recurrent events after the warning signal of TIA has occurred.

Results of the Early Use of Existing Preventive Strategies for Stroke (EXPRESS) trial, of which Dr. Rothwell was principal investigator, showed that urgent aggressive intervention after a TIA or minor stroke cut the 90-day risk for recurrent stroke by 80%, as well as reducing fatal and nonfatal stroke, disability, hospital admission days, and costs by the same magnitude (Rothwell PM et al. Lancet 2007; 370:1398-1400; Luengo-Fernandez R et al. Lancet Neurol 2009;8:218-219).

On the basis of these kinds of findings, clinical guidelines in most countries have changed significantly, recommending that patients should be assessed within 24 hours of a TIA or minor stroke, down from a recommendation of 7 days only a year ago.

Still, while 24 hours is better than 7 days, "it's still not quite a medical emergency," he said. In this paper, they sought to determine the real risk for recurrence in the 24 hours following a TIA, "to see what the very early risk really is in the first few hours and what might be gained, therefore, by seeing patients even earlier, as well as what might be gained by better public education to get patients to present immediately when they have 1 of these minor episodes."

The ABCD2 risk score aims to help clinicians identifying those at highest risk but was derived for prediction of the risk for stroke at 7 days and has not been examined in this hyperacute phase, Dr. Rothwell noted.

Using data from the Oxford Vascular Study, a prospective, population-based incidence study of TIA and stroke, they determined the risk for recurrent stroke at 6, 12, and 24 hours after an index event.

Of 1247 patients with a first TIA or stroke, 35 had recurrent strokes within 24 hours, all of them in the same arterial territory, the authors report. In 25 of these patients with recurrent strokes, the initial event was a TIA.

Of the 488 patients in total whose initial event was a TIA, 42% of the 25 events that occurred within the first 30 days actually occurred within the first 24 hours.

Stroke Risk at 6, 12, and 24 Hours Following Transient Ischemic Attack

Time Point, h Stroke Risk (%) 95% CI
6 1.2 0.2 – 2.2
12 2.1 0.8 – 3.2
24 5.1 3.1 – 7.1

"The other thing we were keen to do was make sure that the ABCD2 risk score, which is now embedded in all the national and international guidelines, actually worked for the risk of stroke within the first few hours," Dr. Rothwell noted. "The guidelines say that patients with scores less than 4 needn't be seen quite so urgently as those with higher scores, but that's only really been looked at for 7-day risk."

What they found is that basic triage using the ABCD2 score "still seems reasonable in patients that present within the first few hours," he said. The 12- and 24-hour risks were strongly related to the risk score (P = .02 and .0003, respectively). However, these findings were still based on small numbers of outcomes, they caution, and further studies on this would help to confirm their results.

Of some concern, 16 of the 25 (64%) recurrent stroke patients with TIA as their initial event did seek medical attention, usually from their family doctor, after their TIA but did not receive antiplatelet therapy acutely, nor were they sent to the acute intervention clinic at their institution. "However, the fact that the majority of patients sought medical attention prior to their recurrence indicates that emergency triage and treatment are feasible, if front-line services recognize the need," the authors write.

Dr. Rothwell added that he sees the medical profession and neurologists in particular as getting the message that patients presenting with a TIA and a high risk score need to be seen "immediately, rather than tomorrow, which is the current guideline."

"I think the bigger challenge is to get that message over to the public, because at the moment only about 50% of patients who have a TIA seek medical attention within 24 hours, and a lot of patients don't seek medical attention at all," he said.

TIA: A Medical Emergency

Asked for comment on these findings, Philip B. Gorelick, MD, professor and head of the department of neurology and rehabilitation and director of the Center for Stroke Research at the University of Illinois College of Medicine at Chicago, said that accumulating data confirm that recent TIA should be treated as a medical emergency.

A recent change in the definition of TIA by the American Heart Association/American Stroke Association (Easton JD et al. Stroke 2009;40:2276-2293) supports this conclusion, Dr. Gorelick noted, suggesting that neuroimaging and diagnostic workup should be carried out within 24 hours of a TIA when patients present within this time period and that it is reasonable to hospitalize patients who have had such an episode within the previous 72 hours if they have an ABCD2 score of 3 or more, he added

Importantly, it is critical to rapidly determine the etiology of TIA — for example, whether it results from a cardiac source embolism or large artery disease, Dr. Gorelick noted. "Currently, a tissue-based definition of TIA has been adopted. In aggregate data, it has been estimated that about 39% of [magnetic resonance imaging] diffusion-weighted image studies in patients with TIA show a cerebral ischemic injury pattern, and therefore a cerebral infarction has actually occurred."

The current study emphasizes again the importance of rapid diagnosis and treatment, since there was a 5.1% risk for stroke in the first 24 hours after TIA, with many of the strokes leading to a poor outcome, he said. "Furthermore, the 7-day stroke rate was close to 10%," he noted. "Although 64% of these early cases sought urgent medical attention prior to recurrent stroke, none received antiplatelet therapy acutely."

The lesson from this and other studies is that TIA is not benign, and urgent diagnosis and treatment is indicated, even though this may not occur in real-world experience, Dr. Gorelick concluded. In this effort, the ABCD2 score is a reliable clinical tool that assesses the acute risk for stroke in TIA patients.

"We need to continue to educate the public and healthcare professionals about the importance of recent TIA as a predictor of stroke and the urgency of diagnosis and treatment," Dr. Gorelick told Medscape Neurology. "Emergency TIA assessment and treatment programs have proven to dramatically reduce the risk of stroke after TIA. Widespread establishment of such programs should be considered, as we need to get TIA patients under the care of those who have experience in vascular neurology and who can make a difference."

The study was funded by the UK Medical Research Council, the National Institute of Health Research, the Stroke Association, the Dunhill Medical Trust, and the Oxford Partnership Comprehensive Biomedical Research Centre. The authors report no disclosures.

Neurology. 2009;72:1941-1947. Abstract