Endovascular Treatment of Stroke, Though Uncommon, Gains Ground

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In the 6 years after the first mechanical thrombectomy device entered the US market, the proportion of ischemic stroke patients who underwent endovascular treatment increased six-fold. A nationwide database study published online September 11, 2012, ahead of print in Stroke, links this shift to better survival but also greater disability.

An outside researcher interviewed by TCTMD, however, cautioned that endovascular therapy for stroke is still in its infancy.

For the observational study, Ameer E. Hassan, DO, of the University of Texas Health Science Center, San Antonio (Harlingen, TX), and colleagues derived data on ischemic stroke from the Nationwide Inpatient Sample of the Agency for Healthcare Research and Quality. Diagnostic and procedural codes were used to identify patients who received endovascular treatment. The researchers then compared outcomes between time periods that encompassed the US Food and Drug Administration approvals of 2 mechanical thrombectomy devices:

• 2004-2007: post-approval of the Merci Retriever (Concentric Medical, Mountain View, CA)
• 2008-2009: post-approval of the Penumbra system (Penumbra, Alameda, CA)

In-Hospital Mortality Drops for Endovascular Patients

Among 3,292,842 patients admitted to the hospital with ischemic stroke during the 6-year period, 72,342 (2.2%) received IV tissue plasminogen activator (tPA) and 13,799 (0.4%) underwent endovascular therapy. Use of IV tPA rose from 1.2% in 2004 to 3.4% in 2009 (P value not reported), while endovascular therapy increased from 0.1% to 0.6% (P < 0.0001). Endovascular treatment was used most often in patients younger than 45 years (1.3%) and least often in those aged 85 and older (0.2%).

Patients who received endovascular therapy in the post-Merci era were younger and less likely to have hypertension, congestive heart failure, and renal failure compared with those who followed in the post-Penumbra era. However, rates of in-hospital complications including intracranial hemorrhage and MI were similar between the 2 periods.

For the endovascular group, treatment in 2008-2009 was associated with shorter length of stay and a trend toward lower in-hospital mortality compared with treatment in 2004-2007. However, hospital charges were higher, as was the likelihood of discharge with moderate/severe disability (table 1).

Table 1. Endovascular Group: Hospital-Related Outcomes and Discharge Status

In-hospital mortality in patients who received IV tPA was 13.6% in 2004 and 11.1% in 2009 (P value not reported). For patients who received endovascular therapy, in-hospital mortality decreased from 32.4% in 2004 to 17.5% in 2009 (P = 0.0096). 

Multivariate logistic regression analysis that adjusted for age, gender, comorbidities, and secondary intracranial hemorrhage found that the likelihood of minimal disability held steady between 2004-2007 and 2008-2009 (OR 0.8; 95% CI 0.7-1.04; P = 0.1127). In addition, in-hospital mortality decreased (OR 0.7; 95% CI 0.6-0.9; P = 0.0072), while discharge with moderate/severe disability increased (OR 1.4; 95% CI 1.2-1.7; P = 0.0002) after the introduction of Penumbra.

Both Gains and Losses

“The results do not reflect on individual devices, but rather the time period that signifies greater availability and acceptance of new endovascular devices,” Dr. Hassan and colleagues stress. “Most endovascular treatments are a combination of intra-arterial thrombolytics and thrombectomy.”

Possible explanations for why endovascular treatment grew in popularity include “an increasing number of comprehensive stroke centers, increased physician acceptance, advanced imaging modalities, and better reimbursement for stroke hospitalizations subsequent to mechanical thrombectomy,” the researchers suggest. Better imaging, they add, may enable improved identification of candidates who present beyond the 3-hour time window recommended for thrombolysis.

The concurrent decrease in mortality and increase in disability indicate that newer therapies may have come at a cost. “Besides the increased costs of health care and support services in patients with disability, the acceptability of such an outcome for patients and families needs to be considered,” Dr. Hassan and colleagues advise, adding that futile recanalization attempts may be at work. “It is also possible that improvement in ancillary care such as neurocritical care and adherence to best practices have improved survival.”

A ‘Tiny’ Slice of Stroke Cases

In a telephone interview, Philip M. Meyers, MD, of Columbia University Medical Center (New York, NY), told TCTMD that the findings are “interesting” and highlight the fact that endovascular treatment of stroke is becoming more common. That being said, an absolute increase of 0.5% over 6 years is “a tiny number,” he stressed.

With 800,000 strokes occurring annually in the United States, interventional cardiologists have seen a window of opportunity, Dr. Meyers commented. However, “the reality is that [only a minority] of those are eligible for endovascular treatment. And probably not every stroke that is eligible for an endovascular procedure is getting one.”

At Columbia, he reported, “we see about 1,000 strokes a year but probably end up treating somewhere between 20 and 70 of those patients [with endovascular therapy], because most patients don’t come in time or have the right kind of stroke.”

Stroke Intervention ‘In Limbo’

In April 2012, the IMS III (Interventional Management of Stroke III) study—which Dr. Meyers referred to as “the only big trial we had”—stopped enrollment when the Data and Safety Monitoring Board decided it was unlikely to observe any benefit from adding intra-arterial tPA and thrombectomy to standard IV tPA. The problem was not lack of statistical power but rather that “the treatment itself just wasn’t cutting the mustard,” he said.

“So we’re definitely still in limbo with stroke intervention,” Dr. Meyers commented. “It’s very different from cardiac disease, where it was pretty easy to prove revascularization for acute MI helps people [if done quickly enough]. With stroke, there’s a lot of opportunity to do a lot of harm.”

Considering that the current study also showed a rise in disability, “it’s not clear we’re helping people,” he said, concluding that the biggest question now is how to improve patient selection.

Dr. Hassan and colleagues agree, noting that the discrepancy between morality and disability points to the “unsolved issues regarding the best selection criteria for identifying patients who could benefit from endovascular treatment. The results also identify gaps in implementation of new devices into routine practice in a manner that is consistent with clinical benefit observed in trials.”

Source:

Hassan AE, Chaudhry SA, Grigoryan M, et al. National trends in utilization and outcomes of endovascular treatment of acute ischemic stroke patients in the mechanical thrombectomy era. Stroke. 2012;Epub ahead of print.

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