State of the art review: Stroke imaging, drug-eluting coronary stents, myocardial necrosis, acute coronary syndrome, abdominal aortic aneurysms

Early 2007 has been a robust period for the publication of meaningful cardiac imaging research. The National Institute of Neurological Disorders and Stroke's landmark comparison of noncontrast CT and MRI for stroke confirmed what many neuroradiologists suspected: MRI is the new gold standard for the initial diagnosis and subsequent evaluations of acute stroke. In another compelling study, Swedish researchers found that heart patients equipped with drug-eluting stents are more like to die in the three years following installation than patients who received bare metal stents.

Stroke imaging

Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke: a prospective comparison

Lancet 2007;369(9558):293-298

The scale weighing the diagnostic merits of MRI and noncontrast CT for initial evaluation of stroke tipped dramatically in favor of MRI in January with the publication of this NINDS study. The blinded, prospective single-center trial, conducted in a typical community hospital, found that MRI is three times more sensitive to the presence of ischemic stroke than noncontrast CT. The findings led senior author Dr. Steven Warach, section chief of stroke diagnostics and therapeutics, to recommend MRI as the first choice for stroke diagnosis and evaluation."From the standpoint of wanting the most accurate diagnosis, MRI should be the preferred neuroimaging evaluation of possible stroke unless there is a contraindication to MRI," Warach said. The findings have implications for many hospitals where the immediate response to stroke is gauged with noncontrast CT. The 54% accuracy rate of CT in the Lancet study may explain why many neurologists do not trust it when deciding whether to recommend tPA thrombolysis. Compared to final clinical results, MRI is 86% accurate."There are financial considerations, and each hospital and department will have to look at those, but it is going to be hard to argue a diagnostic test that is twice as accurate as another would not be in the patient's best interest," Warach said.

Coronary artery stents

Long-term outcomes with drug-eluting stents versus bare-metal stens in Sweden

NEJM 2007, published at www.nejm.org Feb. 12, 2007

A large, long-term outcomes study has raised questions about the safety of drug-eluting coronary artery stents. Dr. Bo Lagerqvist and colleagues with the Swedish Coronary Angiography and Angioplasty Registry found that drug-eluting stents are associated with an increased death rate compared to bare-metal stents. The conclusions of the SCAAR were based on three-year follow-up evaluations of 6033 patients treated with drug-eluting stents and 13,738 patients who received bare-metal stents following angioplasty for coronary artery disease. Lagerqvist observed a trend toward fewer cardiac events for the drug-eluting stent group six months after installation. After six months, patients with drug-eluting stents had a significantly higher adverse event rate, with 12.7 more events per 1000 patients per year than the bare-metal stent group. The risk of death was 0.5 percentage points higher and the composite death and myocardial infarction rate was 0.5 to 1 percentage points higher per year for patients equipped with drug-eluting stents.

Myocardial necrosis

Diagnostic value of contrast-enhanced magnetic resonance imaging and single-photon emission computed tomography for detection of myocardial necrosis early after acute myocardial infarction

J Am Coll Cardio 2007;49(2):208-216

Contrast-enhanced MRI proved superior to SPECT for detecting myocardial necrosis in this study of 75 patients with acute myocardial infarction. Dr. Markus Schwaiger's research group at the Technical University of Munich found that MRI performed seven days after coronary angioplasty was 10 percentage points more sensitive than SPECT for the detection of MI (97% vs. 87%). MRI more reliably detected small infarctions in patients with elevated troponin T levels, and MRI had an 85% to 46% advantage in sensitivity over SPECT for finding non-Q-wave infarctions. The sensitivity of MRI for myocardial infarction remained high regardless of the location of the coronary artery occlusion, while SPECT was less sensitive when the occlusion resided in the left circumflex artery, according to principle investigator Dr. Tarq Ibrahim.

Acute coronary syndrome

Prognostic value of SPECT myocardial perfusion imaging in patients with elevated cardiac troponin I levels and atypical clinical presentation

Journal of Nuclear Cardiology 2007;14(1):53-58

In a study of 156 consecutive patients, Dr. Marcelo Di Carli's group in the nuclear medicine division of Brigham and Women's Hospital determined the prognostic value of perfusion SPECT in patients with atypical clinical presentations for acute coronary syndrome and unexpectedly high cardiac troponin I enzyme levels. Perfusion SPECT was performed within 30 days of the initial presentation of ACS symptoms, according to principle investigator Dr. Sharmila Dorbala. Nearly all patients were initially found to have low or intermediate risk of ACS, but the six-month event rate was high with 13 cardiac deaths or nonfatal myocardial infarctions. Abnormal perfusion SPECT was associated with a threefold higher risk of death from all causes and a sevenfold higher risk of cardiac-related death than normal SPECT studies.

Abdominal aortic aneurysm

Rapid assessment of abdominal aortic aneurysms by 3-dimensional ultrasonography

Journal of Ultrasound in Medicine2007;26:223-226

Dr. Christiane M. Nyhsen, a radiologist at Freeman Hospital in Newcastle upon Tyne, U.K., demonstrated a close correlation between 3D and conventional 2D ultrasound for AAA diagnosis and measurement. Based on experience with 30 consecutive patients, she found no bias between the two tests and a close correlation between anteroposterior maximum diameters and the transverse maximum diameters acquired in the coronal plane with the two techniques. Three-D was preferred for its speed and convenience. AP and TS views were typically acquired in three seconds per view. Volume data sets were saved digitally for review after the patient left the department, Nyhsen said.