(Circulation. 1997;96:3992-4001.)
© 1997 American Heart Association, Inc.
Articles |
Nitroglycerin Enhances the Ability of Dobutamine Stress Echocardiography to Detect Hibernating Myocardium
From the Division of Cardiology, Hartford Hospital, University of Connecticut School of Medicine (Hartford).
Correspondence to Chunguang Chen, MD, Division of Cardiology, Hartford Hospital, 80 Seymour St, Hartford, CT 06102.
Background A biphasic response of wall thickening with initial improvement and subsequent deterioration during dobutamine stress echocardiography (DSE) has been increasingly used for detection of hibernating myocardium. However, the improvement of wall thickening at low-dose DSE may be limited in hibernating myocardium by severe hypoperfusion. Nitroglycerin (NTG) improves myocardial perfusion, reduces oxygen demand, and may enhance low-dose dobutamine to improve wall thickening.
Methods and Results A pig model of myocardial hibernation of 24
hours to 7 days was created through severe left anterior descending
coronary artery stenosis with coronary flow
reductions of 
40%, producing severe regional left
ventricular dysfunction but no infarction in seven pigs.
Myocardial infarction was produced in five pigs with occlusion of the
artery. DSE was performed with incremental doses with and without an
NTG infusion of 50 to 100 µg/min. In the hibernating group, NTG alone
improved wall thickening in the hibernating region modestly from
11.4±7.2% at baseline to 19.1±7.0%. The improvement was associated
with increased regional coronary flow from 0.46±0.12 to
0.55±0.13 mL · beat-1 · 100 g
myocardium-1 (P<.05). There
was an additive effect of NTG to low-dose (2.5 to 5 µg ·
kg-1 · min-1) dobutamine
on wall thickening in the hibernating region. The improvement of wall
thickening of hibernating myocardium with NTG and
dobutamine, from 23.7±11.1% to 31.1±8.9%
(P<.001), was associated with an increase in regional
coronary flow (P<.01). NTG did not prevent high
doses of dobutamine from inducing deterioration of wall
thickening in hibernating myocardium. In the infarcted
group, no improvement in wall thickening was observed in infarcted
regions during NTG infusion, dobutamine infusion, or the
combination.
Conclusions NTG enhances the improvement of wall thickening at low-dose dobutamine and does not prevent high-dose dobutamine from inducing ischemia in hibernating myocardium. Thus, NTG augments the biphasic response of wall thickening and improves the accuracy of DSE for detecting viable myocardium.
Key Words: coronary disease ischemia • stunning • echocardiography • nitroglycerin
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