Title: Cardiovascular Magnetic Resonance in Patients With Myocardial Infarction: Current and Emerging Applications
Topic: Noninvasive Cardiology
Date Posted: 2/2/2010
Author(s): Kim HW, Farzaneh-Far A, Kim RJ.
Citation: J Am Coll Cardiol 2009;55:1-16.
Clinical Trial: No
Perspective: This is a state-of-the-art review of the role of cardiac magnetic resonance imaging (CMR) in patients with acute and chronic myocardial infarction (MI). Ten points to remember include:
1. MI is a leading cause of morbidity and mortality for which a broad range of ever-changing therapeutic and diagnostic options are available. Outcomes are directly related to MI size. Similarly, diagnostic tests for detection of MI are also dependent on a critical mass of involved myocardium for detection. Current recommendations suggest a combination of electrocardiographic, enzymatic, and imaging techniques including CMR, echocardiography, and radionuclide imaging to establish the diagnosis.
2. CMR is a multi-technique imaging modality dependent on both hardware and software for acquisition. Acquisition software can be modified with different pulse sequences to obtain different unique and nonoverlapping data. A comprehensive CMR exam will include multiple pulse sequences designed to define cardiac anatomy and blood flow and to detect thrombus, infarction, perfusion, etc. Many CMR artifacts are specific to the pulse sequence utilized and, as such, will not be present on all images.
3. Commonly used CMR techniques include cine imaging for cardiac function, determination of ventricular volumes, and left ventricular mass as well as valvular morphology. CMR determined chamber size and mass are highly accurate and reproducible.
4. Other CMR techniques include specific imaging for acute myocardial injury as well as perfusion imaging at stress and with rest.
5. Use of gadolinium contrast for delayed imaging is a highly specific marker of MI. Gadolinium is excluded from normal, active myocytes and is sequestered in the interstitium. As such, when detected late after injection, it is a marker of nonviable areas of myocardium, but is not necessarily specific for ischemic heart disease.
6. The specific pattern of late gadolinium enhancement may allow a more specific diagnosis. The effects of coronary occlusion, typically spread in a wavefront from the endocardium to the epicardium and a matching pattern of gadolinium hyperenhancement, may be specific for the effects of coronary occlusion. Other diseases, such as acute myocarditis, present with patchy or mid-myocardial enhancement.
7. The spatial resolution of delayed enhancement (DE)-CMR is exceptionally high and in the clinical setting allows detection of MI involving as little as 1 g of myocardium. In comparison, wall motion abnormalities detected with echocardiography or other techniques will be dependent on a threshold of subendocardial involvement, and SPECT imaging may require >10 g of myocardial involvement before an abnormality is reliably detected.
8. In addition to detecting both acute and chronic MI, CMR may be useful for detecting complications such as aneurysm formulation, right ventricular involvement, pericarditis, and left ventricular thrombus.
9. Using DE-CMR as a marker for MI, a substantial number of clinically and electrocardiographically silent MIs are detected. DE-CMR detects 2-3 times more clinically occult MIs than does an electrocardiogram.
10. Because of the high spatial resolution and reproducibility of CMR for detecting and quantifying MI, it may serve as an accurate endpoint for clinical trials in which reduction in myocardial size rather than mortality is a surrogate endpoint. It has implications for allowing reduced sample size to be used in clinical trials. William F. Armstrong, M.D., F.A.C.C.
Title: Ginkgo Biloba for Preventing Cognitive Decline in Older Adults: A Randomized Trial
Topic: Prevention/Vascular
Date Posted: 2/5/2010
Author(s): Snitz BE, O’Meara ES, Carlson MC, et al., on behalf of the Ginkgo Evaluation of Memory (GEM) Study Investigators.
Citation: JAMA 2009;302:2663-2670.
Clinical Trial: yes
Study Question: Does the herbal product Ginkgo biloba have an effect on long-term cognitive functioning in older adults?
Methods: The Ginkgo Evaluation of Memory (GEM) study is a randomized, double-blind, placebo-controlled clinical trial of 3,069 community-dwelling participants ages 72-96 years, which was conducted in six academic medical centers in the United States between 2000 and 2008. Median follow-up was 6.1 years. Participants received either twice-daily dose of 120 mg extract of G. biloba (n = 1,545) or identical appearing placebo (n = 1,524). Primary outcome was the rates of change over time in the Modified Mini-Mental State Examination (3MSE), in the cognitive subscale of the Alzheimer Disease Assessment Scale (ADAS-Cog), and in neuropsychological domains of memory, attention, visual-spatial construction, language, and executive functions, based on sums of z scores of individual tests.
Results: Annual rates of decline in z scores did not differ between G. biloba and placebo groups in any domains, including memory, attention, visuospatial abilities, language, and executive functions. For the 3MSE and ADAS-Cog, rates of change varied by baseline cognitive status (mild cognitive impairment), but there were no differences in rates of change between treatment groups. There was no significant effect modification of treatment on rate of decline by age, sex, race, education, APOE*E4 allele, or baseline mild cognitive impairment.
Conclusions: Compared with placebo, the use of G. biloba, 120 mg twice daily, did not result in less cognitive decline in older adults with normal cognition or with mild cognitive impairment.
Perspective: Like the great majority of studies funded by the National Institutes of Health designed to test the value of vitamin and herbal supplements, this excellent study shows no value for ginkgo, which has been taken by at least one third of my older patients over the past 15 years. The cost of the studies has been substantial and seems to have done little to reduce the excessive use and marketing of supplements. Melvyn Rubenfire, M.D., F.A.C.C.