American Heart Association

Monthly Archives: March 2013

Outcomes of Carotid Endarterectomy in the Elderly

Aaron Tansy, MD

Carotid endarterectomy (CEA) is standard therapy for symptomatic internal carotid stenosis. However, benchmark trials that demonstrated the procedure’s efficacy did not enroll patients > 80 years leaving unanswered whether CEA may be a favorable treatment in this cohort as well. Now in an upcoming issue of Stroke, Kumar Rajamani and colleagues provide a first attempt to address this question: a retrospective analysis of outcomes in elderly patients who underwent CEA.

The investigators culled data from the CARE© Registry, a multi-hospital, clinical procedures registry, and evaluated the effects of age (stratified into 4 groups: 70-74, 75-79, 80-84, and >/85) and symptomatic status (asymptomatic or symptomatic) on primary composite outcome (in-patient stroke/death/MI), singular morbidities, and mortality following CEA. A total of 4149 patients underwent CEA, 1/3 of which were symptomatic. Analysis revealed with increasing age came significantly increasing risk of the composite outcome and mortality after CEA with those >/85 years at highest risk. In addition, increased age (>75) increased risk of mortality for those in the asymptomatic sub-group. Conversely, increased age did not alter risk for mortality in the symptomatic group or for morbidity in either sub-group.

Although not reflective of all hospitals performing CEA’s, this study reveals a few key facts about current CEA practice generally in the US. For one, the vast majority of patients > 70 years currently undergoing CEA have asymptomatic carotid stenosis. Further, this subgroup appears at highest risk for CEA-related death independent of complications such as MI or stroke. Lastly, those oldest who undergo CEA are most likely to suffer complications or death.

Although in the original trials it was not superior to medical therapy (aspirin) for stroke risk reduction in asymptomatic patients, CEA did provide non-significantly better benefit long-term prompting its consideration in younger patients whose long-term risk of stroke was considered higher than their long-term risk of death. Given that standard medical therapy today has supplanted aspirin with more effective antiplatelet agents and high-dose statins, it is now even less likely that CEA provides significant benefit over current medical therapy especially in the elderly. Thus, while only one retrospective evaluation, this study raises an important question for which we should give pause and concern: when we already have effective medical therapies in place, should we continue to engage in a surgical practice on asymptomatic patients that research, to this point, has yet to support as clearly beneficial and, even more worrisome, now supports only as harmful?

The Effect of Graduated Compression Stockings on Long-term Outcomes

Waimei Tai, MD

Dennis. et. al. recently published a study demonstrating the relative non-efficacy of graduated compression stockings in patients after ischemic or hemorrhagic stroke. Patients were enrolled within three days of their index event and wore the T.E.D stockings until they were mobile, discharged from the hospital, or they refused to wear them.  Overall, there was no added benefit by wearing these stockings. Given the short term utility of the stockings, I can’t imagine how the stockings effects would last longer than the duration of the hospitalization, but they did monitor the patients for thromboembolic events for 6 months after enrollment.

Not surprisingly, this study confirms similar results as other non-stroke specific cohorts of patients. In fact, our hospital has already determined after reviewing best practices, to avoid graduated compression stockings (both knee high and thigh high) for routine DVT prophylaxis.
For general ischemic stroke patients, the AHA guidelines (and JCAHO core measures) recommend chemical prophylaxis within 48 hours of index event. For those patients for which this is contraindicated, sequential compression device is used.

What do you use at your hospital? How should we best incorporate new information to allow best practices be advanced to clinical practice in your hospital?

Diffusion-weighted MR imaging may underestimate acute ischemic lesions

Jiaying (Jayne) Zhang, MD 

It is widely accepted that Diffusion-weighted Imaging (DWI) is the most sensitive and reliable at detecting early ischemic tissue. However, there exists a lesser known phenomenon called Reversed Discrepancy (RD) between Computed Tomography (CT) and DWI that seems to contradict this general concept. Reversed Discrepancy is the failure of DWI to detect early CT ischemic lesion showing parenchymal hypoattenuation. Though the significant of early ischemic changes on CT within 3 hours of symptom onset can be controversial, it can be indicative of critical hypoperfusion and irreversible ischemia with high risk of symptomatic hemorrhage after tissue plasminogen activator (tPA) treatment.

In this study by Kawano et al, the authors aimed to describe the clinical significance of RD including the factors associated with the development of RD in stroke patients within 3 hours of onset. A total of 164 patients with ischemic stroke in the anterior circulation who underwent both CT and MRI within 3 hours of onset were retrospectively analyzed. RD was found in 24% of the study population. Interestingly, RD group patients tended to be older, had a higher admission NIHSS, higher rate of atrial fibrillation and higher rate of proximal ICA/MCA occlusion. Atrial fibrillation was also independently associated with the presence of RD.

What is striking about this study is the frequency of RD identified this group of patients presenting within the 3 hour window. This means, as the authors pointed out, that RD is more commonly encountered in acute stroke imaging than previously thought. But what is the pathophysiological significance of this phenomenon? Although the exact cause is not known, it is theorized that RD may be related to early spontaneous reperfusion resulting in pseudonormalization of Apparent-diffusion coefficient (ADC) and hence by this mechanism explain the potential reversibility of RD. Another mechanistic consideration to explore in the future is the state and extent of the collateral circulation on the symptomatic side. Perhaps poor collateral flow is a factor associated with the development of RD and that is why patients with RD tend to have a higher NIHSS and rate of proximal occlusions.

Statins Reduce Neurologic Injury in Asymptomatic Carotid Endarterectomy

Waimei Tai, MD

Heyer et. al. had a prospective observational study of 328 patients with asymptomatic stenosis who were observed to be on a statin or not on a statin. There were no statistical differences in the two cohorts (statin vs. no statin) although there appeared to be a trend of younger people in the statin arm (likely confounded as non-prescription of statins is higher in older patients for any reason). 

They also concluded that patients had better cognitive function if they had a statin prescription. Certainly it makes sense if those on a statin had a lower peri-operative stroke incidence (0.0% vs 3.1%) it makes sense that cognitive function for the cohort without strokes would be higher. 

It would be interesting to know the relationship between the patient’s cholesterol levels, cognitive function, and statin use as other studies have suggested a correlation between lower cholesterol levels and poorer cognitive function, although the pathophysiology maybe different (statins in periop phase maybe protective against stroke, naturally low cholesterol levels maybe correlated with other markers of neurodegenerative disease).

For the time being, I think I will continue statin prescription for my asymptomatic carotid patients, as I think it’s reasonable to treat large vessel carotid disease with optimal cholesterol lowering/plaque stabilizing medication. Whether they need to get carotid endarterectomy, now that’s another question. 

How do you treat your asymptomatic carotid patients?

Exploring Intracranial Aneurysms Using Carbon Birth Dating

Osman Mir, MD

Etminan N, Dreier R, Buchholz BA, Bruckner P, Steiger H-J, Hänggi D, et al. Exploring the Age of Intracranial Aneurysms Using Carbon Birth Dating: Preliminary Result. Stroke. STROKEAHA.112.67380. Published Ahead of Print on January 17, 2013.

SAH accounts for % of strokes. Prevalance studies have shown that % of people have aneurysms. SAH is a devastating disease though. It carries high morbidity and mortality. However it is not precisely known what are the predictors of rupture in SAH. In this journal of stroke Etminan et al explore a really novel hypothesis regarding prediction of rupture in aneurysms. They looked at feasibility of carbon dating of Aneurysms. Essentially carbon dating of aneurysms could establish the age of the collagen in the aneurysm wall. This in comparison with carbon dating of the person’s age called birth dating could lead to some idea about rapid collagen turn over in aneurysms, which might possibly lead to rupture. Etminan et al also looked at the ratio of C14to Carbon in the collagen which they expressed as F14C. In this study what the authors found was that all collagen samples from aneurysms were less than 5 years of age. This was true regardless of the rupture status or the age of the patient. However in patients who had a ruptured aneurysm F14C was directly correlated to the patients’ age and Aneurysm size. 

This is a fascinating study which shows the feasibility of this process. However given the small sample size it is difficult to make any conclusions. This is primarily exploratory hypothesis generating manuscript. What this study does is provides a way to answer questions in a larger sample size with a similar study design. Another limitation of aneurysm dating is that only aneurysms which are getting clipped can be used in the study. Most of the aneurysms are now being coiled. Nevertheless F14C dating of aneurysms can potentially help in understanding the development and structural stability of ruptured and unruptured aneurysms.

ABCD2 Validity and Reliability

Diogo C. Haussen, MD
In medicine, scales are mostly used to classify extend of a variable related to a disease process aiming to define uniformization for a specific relation. This process is ubiquitous to all specialties and diseases, and turns out to be extremely important not only in clinical practice but also in research grounds. Therefore, understanding the interrater reliability and its convergent validity (the degree to which two measures that should be theoretically correlated are in fact related) of a scale is paramount.
The ABCD2 score has been increasingly utilized to triage patients with transient ischemic attack. Ishida et al report a straightforward and interesting report that indicates that retrospective estimation of ABCD2 is considerably inaccurate. The authors compared the prospectively determined ABCD2 scoring (established at the time of the emergency room visit) with retrospective scoring through chart review in 102 TIA patients. The correlation coefficient between the two raters that performed retrospective analysis was very good. However, the agreement between retrospective and prospective ABCD2 score rating was only 44%. This is solely slightly better than two times chance alone. The suboptimal convergent validity may, in part, explain the “mixed results” of the previous observational ABCD2 validation studies described in the manuscript. Although the study did not evaluate the predictive value of retrospective ABCD2 scoring for stroke risk, this report exemplifies the major limitations of retrospective analyses, and draws attention to the importance of validation studies for scales utilized in practice or research.