A New Definition for Transient Ischemic Attack and Stroke

Disclosure: Dr. Bravata: Robert Wood Johnson Foundation, Virginia's Health Services Research and Development, and ResMed Foundation; Significant.
Pub Date: Thursday, May 7, 2009
Author: Dawn M. Bravata, MD

Citation

Easton JD, Saver JL, Albers GW, et al. Definition and evaluation of transient ischemic attack: a scientific statement for healthcare professionals from the American Heart Association/American Stroke Association Stroke Council; Council on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular and Stroke Nursing; and the Interdisciplinary Council on Peripheral Vascular Disease. Stroke 2009. Published online before print May 7, 2009. 10.1161/STROKEAHA.108.192218.

Article Text

With the publication of the American Heart Association/American Stroke Association (AHA/ASA) Scientific Statement about Transient Ischemic Attack, the definitions of both stroke and transient ischemic attack (TIA) are revised.[1] Specifically, the diagnoses of stroke and TIA are no longer based on symptom duration but are based on evidence about brain infarction. The new diagnosis of TIA is "a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia without infarction." The new diagnosis of stroke is "an infarction of central nervous system tissue."

With these new definitions, the analogy between cerebrovascular disease and coronary artery disease is strengthened. Yet, I fear that my clinical colleagues will still not triage a patient with transient neurologic symptoms with the same sense of urgency that they have for a patient with chest pain. There are at least three reasons why TIA patients should receive urgent evaluation and management: (a) TIAs are common; (b) TIAs are associated with serious recurrent vascular events; and (c) most of the vascular events occur in the first few days after the TIA, so early interventions are the key to risk reduction.

There are between 200,000 and 500,000 TIAs in the United States each year.[1] TIA patients are at great risk of recurrent vascular events. Specifically, TIA patients are at higher risk of recurrent vascular events than patients who present with chest pain. For example, among chest pain patients, the combined recurrent vascular event rate (acute coronary syndrome, myocardial infarction or death) at 30 days is 15%.[2] Among TIA patients, the stroke rate at 30 days is 12% [3], and the combined recurrent vascular event rate (stroke, recurrent TIA, hospitalization for a cardiovascular event, or death) at 90 days is 25%.[4] At least half of these recurrent vascular events occur in the first week post-TIA.[4] For example, 5% of TIA patients will have a stroke in the first 2 days post-TIA.[4]

As we seek to improve the clinical care of patients with TIA, it may be helpful to speculate on the reasons for the relative lack of clinical urgency in the care of patients with TIA. First, as described above, clinicians (and patients) may be unaware of the degree to which TIA confers risk of serious adverse events.

Second, patients with TIA often present after the event has resolved. In so far as clinical urgency is commensurate with patient distress, asymptomatic patients are less likely to receive urgent intervention than patients who present with an acute symptomatic event.

Third, there may be a sense of clinical nihilism surrounding the care of patients with cerebrovascular disease. If this exists, it is likely a historical phenomenon, from a time when few management strategies were available. In our current era, the more likely contributing factor is the lack of randomized controlled trials that demonstrate the benefits of a particular intervention in improving post-TIA outcomes.

Fourth, despite the existence of guidelines [5], there may be confusion around the standard of care. For example, there is variation in practice related to post-TIA emergency department evaluation and hospitalization. The variation in practice increases with increasing delay from the time of symptom onset to the time of presentation.

Fifth, there may be confusion about the diagnosis of TIA. Given that the diagnosis of TIA is made most often on the basis of the medical history and given that other clinical entities can mimic a TIA, clinicians may be hesitant about declaring the patient as having had a TIA.

Finally, most internal medicine and family practice residencies have substantial clinical cardiology training with relatively less training in neurology. Although most patients with TIA and stroke are cared for in the long term by primary care internists or family practitioners, the relative lack of training in neurology may contribute to a sense of diagnostic discomfort or clinical uncertainty for patients with TIA.

I do not believe that the change in the definition of TIA and stroke, from the time when reversible ischemic neurologic deficit (RIND) was in use, plays a role in the relative lack of clinical urgency in the care of patients with TIA.

In addition to the revised diagnostic definitions, the new AHA/ASA Scientific Statement provides a strong recommendation in favor of magnetic resonance imaging (MRI) within 24 hours of TIA symptom onset.[1] The authors review the data that demonstrate the prognostic importance of post-TIA, diffusion-weighted MRI results. However, given the expense of providing 24-hour-a-day MRI capability, hospital administrators may ask how MRI will change clinical decision-making. For example, decision-making about the need for hospitalization can be based on the ABCD [2] score but could also include hospitalization for patients with positive diffusion-weighted MRI.

In conclusion, the authors of the new AHA/ASA Scientific Statement are to be congratulated for this important advance in cerebrovascular science. The AHA should now clarify the terminology about acute neurovascular syndromes. The National Institutes of Health, Department of Veterans Affairs, AHA, and others should fund intervention trials that target TIA patients. Graduate medical education programs should make high-quality clinical neurology training a mandatory component of internal medicine and family practice training. The AHA/ASA, National Stroke Association, Centers for Disease Control and Prevention, and others should improve public and provider awareness about the risks that TIA confers to patients so that they can seek and obtain the care they need to prevent stroke and other vascular events.

References

Easton D, Saver J, Albers G, et al. Definition and evaluation of transient ischemic attack. 2009.
Rao S, Ohman EG, Granger CB, et al. Prognostic value of isolated troponin elevation across the spectrum of chest pain syndromes. Am J Cardiol 2003; 91:936-940.
Lovett J, Dennis M, Sandercock P, et al. Very early risk of stroke after a first transient ischemic attack. Stroke 2003;34:e138-e140.
Johnston S, Gress D, Browner W, et al. Short-term prognosis after emergency department diagnosis of TIA. JAMA 2000;284:2901-2906.
Adams R, Albers G, Alberts M, et al. Update to the AHA/ASA recommendations for the prevention of stroke in patients with stroke and transient ischemic attack. Stroke 2008;39:1647-1652.

-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association --