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Myocardial blood flow at rest and contractile reserve in patients with chronic coronary artery disease and left
J A Panza1, V Dilsizian, R V Curiel
1Cardiology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA. panzaj@gwgate.nhlbi.nih.gov
Insights
Resting myocardial blood flow is crucial for preserving contractile reserve in patients with coronary artery disease and left ventricular dysfunction. Myocardial blood flow influences the effectiveness of dobutamine echocardiography in assessing myocardial viability.
Area of Science:
- Cardiology
- Nuclear Cardiology
- Echocardiography
Background:
- Chronic left ventricular dysfunction in coronary artery disease can impair myocardial response to dobutamine.
- Hibernating myocardium, caused by reduced coronary blood flow, is a key factor.
- Understanding this relationship is vital for managing heart conditions.
Purpose of the Study:
- To investigate the link between resting myocardial blood flow and contractile reserve.
- To assess how coronary artery disease affects the heart's response to dobutamine.
- To determine the role of perfusion in myocardial viability assessment.
Main Methods:
- 23 patients with coronary artery disease and left ventricular dysfunction were studied.
- Transesophageal echocardiography with dobutamine infusion was performed.
- Positron emission tomography (PET) assessed resting myocardial blood flow using 15O-water or 13N-ammonia.
Main Results:
- Myocardial regions with preserved contraction showed higher blood flow than dyssynergic regions.
- No correlation between blood flow and dobutamine response was found in normally contracting regions.
- A significant correlation between resting blood flow and contractile reserve was observed in diminished contraction regions (r=0.53, P<.0001).
- Dobutamine response varied significantly with reduced blood flow levels.
Conclusions:
- Resting myocardial blood flow is essential for maintaining contractile reserve in patients with coronary artery disease.
- Regional perfusion dictates the likelihood of a positive dobutamine response in dyssynergic areas.
- Myocardial blood flow assessment is critical for interpreting dobutamine echocardiography in evaluating myocardial viability.
Background:
The mechanisms that determine chronic left ventricular dysfunction in coronary artery disease (in particular, critical reductions in coronary artery blood flow leading to hibernating myocardium) may affect the ability of the myocardium to respond to inotropic stimulation with dobutamine. This study was designed to investigate the relationship between resting myocardial blood flow and contractile reserve in patients with coronary artery disease and chronic left ventricular dysfunction.
Methods And Results:
Twenty-three patients (21 men and 2 women; age 61 +/- 9 years) underwent transesophageal echocardiography during infusion of dobutamine (2.5 microg/kg to 40 microg/kg per minute) and positron emission tomography (PET) with 150-water (9 patients) or 13N-ammonia (14 patients). Systolic wall thickening at each dose of dobutamine and resting myocardial blood flow were quantitatively analyzed in 8 anatomically matched regions at mid-ventricular level. Myocardial regions with preserved contraction had higher blood flow compared with regions with basal dyssynergy (0.99 +/- 0.3 vs 0.65 +/- 0.3 mL/min/gm; P < .0001). Among myocardial regions with preserved resting contraction, no relation was observed between blood flow and the response to dobutamine (r = 0.06). In contrast, among myocardial regions with diminished resting contraction, a significant correlation was observed between resting blood flow and contractile reserve (r = 0.53; P < .0001). The maximum increase in percent systolic wall thickening with dobutamine was 32.8% +/- 14% in regions with normal blood flow, 21.5% +/- 17% in regions with mildly to moderately reduced blood flow, and 10.7% +/- 10% in regions with severely reduced blood flow (P < .0001).
Conclusions:
These findings emphasize the importance of resting myocardial blood flow for the preservation of contractile reserve in patients with coronary artery disease and left ventricular dysfunction. Because a positive inotropic response to dobutamine is more likely to occur in dyssynergic regions with preserved rather than reduced myocardial blood flow, regional perfusion may determine in which circumstances dobutamine echocardiography contributes to the assessment of myocardial viability.