Circulation. 2007;115:2903
doi: 10.1161/CIRCULATIONAHA.107.183531
(Circulation. 2007;115:2903.)
© 2007 American Heart Association, Inc.
Issue Highlights
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EARLY METOPROLOL ADMINISTRATION BEFORE CORONARY REPERFUSION RESULTS IN INCREASED MYOCARDIAL SALVAGE: ANALYSIS OF ISCHEMIC MYOCARDIUM AT RISK USING CARDIAC MAGNETIC RESONANCE, by Ibanez et al.
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The use of early β-blockade in the setting of acute myocardial
infarction is recommended by guidelines (oral, class I and intravenous,
class IIA) and is widely practiced. Nonetheless, the underlying
mechanism of effect has not been firmly established, particularly
for early intravenous therapy. Translational models have reported
inconsistent results on infarct size, perhaps partly because
infarct size has been measured indirectly using enzymatic release.
In this issue of
Circulation, Ibanez and colleagues use a porcine
occlusion/reperfusion model and cardiac magnetic resonance imaging
to examine the effect of intravenous metoprolol given during
coronary occlusion on infarct size in a randomized, placebo-controlled
format. Using recently validated cardiac magnetic resonance
techniques, they show that given a similar volume of myocardium
at risk, metoprolol was associated with greater myocardial salvage
and smaller initial infarct size, as well as greater recovery
of left ventricular function over 3 weeks. These interesting
data shed light on at least one of the potential underlying
mechanisms of effect of early β-blockade on infarct size
using contemporary methodology. In an accompanying editorial,
Bates examines these data within the perspective of the evolution
of the use of β-blockade early in the course of acute myocardial
infarction, with focus on contemporary trials and guidelines.
See p 2909 (editorial p
2904).
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HERITABILITY, LINKAGE, AND GENETIC ASSOCIATIONS OF EXERCISE TREADMILL TEST RESPONSES, by Ingelsson et al.
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The exercise treadmill test (ETT) is a standardized test used
routinely for detecting ischemic responses to a graded exercise
protocol. Several ETT measures are of prognostic importance,
including the blood pressure and heart rate responses during
exercise and recovery. In this issue of
Circulation, Ingelsson
and colleagues used data from a routine ETT performed in the
community-based Framingham Study sample. The authors evaluated
the heritability and genetic linkage of several hemodynamic
and chronotropic exercise responses and performed association
analyses relating these responses to variation in select candidate
genes. The authors report modest to high heritability for blood
pressure and heart rate responses and note suggestive evidence
for genetic linkage to select chromosomal loci. In association
analyses relating the exercise responses to 235 single-nucleotide
polymorphisms, none of the single-nucleotide polymorphisms was
associated with ETT responses after accounting for multiple
testing. These data establish that genetic influences contribute
to interindividual variability in ETT responses and motivate
additional studies using newer analytical methods (such as genome-wide
association) to elucidate the contribution of specific genes.
See p
2917.
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RELATIONSHIP BETWEEN BLOOD PRESSURE AND STROKE RECURRENCE IN PATIENTS WITH INTRACRANIAL ARTERIAL STENOSIS, by Turan et al.
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To protect the brain against hypoperfusion, it is a common belief
among clinicians that blood pressure should not run too low
in patients with intracranial stenosis. On the basis of long-term
data in >500 patients with angiographically verified stenosis
(50–99%) of an intracranial artery, Turan et al investigated
whether such a therapeutic approach is, indeed, justified. In
the Warfarin-Aspirin Symptomatic Intracranial Disease (WASID)
trial, ischemic stroke during follow-up increased with increasing
blood pressure before and after adjusting for other risk factors.
Specifically, this was also the case in the territory supplied
by the stenotic artery, both in patients with moderate as well
as those with severe narrowing of an intracranial blood vessel.
The risk of stroke was particularly pronounced in patients with
the highest systolic blood pressure. Thus, in patients with
known intracranial stenosis, higher blood pressure is associated
with a higher risk of stroke, a conclusion that contradicts
commonly held beliefs. The findings of Turan et al, therefore,
suggest that the current practice in the management of such
patients should be reconsidered. Interventional trials should
be performed in this patient population to determine whether
appropriate blood pressure lowering is as protective in this
patient population as it is in hypertensive patients at large.
See p 2969 (editorial p
2907).
Visit http://circ.ahajournals.org:
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Images in Cardiovascular Medicine
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Eosinophilic Heart Disease in Acute Myeloproliferative Disorder.
See p
e614.
Changes in Left Atrial and Pulmonary Venous Anatomy During Respiration: A 4-Dimensional Computed Tomography–Based Assessment and Implications for Atrial Fibrillation Ablation. See p e617.
Rapid Formation of Left Ventricular Giant Thrombus With Takotsubo Cardiomyopathy. See p e620.
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Correspondence
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See p
e622.
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