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Absolute blood flow and oxygen consumption in stunned myocardium in patients with coronary artery disease
Edward Barnes1, Roger J C Hall, David P Dutka
1MRC Clinical Sciences Centre and Division of Cardiology, National Heart and Lung Institute, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom.
Insights
In patients with coronary artery disease (CAD), dobutamine causes reversible left ventricular dysfunction despite normal myocardial blood flow (MBF) and oxygen consumption (MMRO(2)). This stunning correlates with coronary stenosis severity and reduced peak MBF.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Nuclear Cardiology
Background:
- Animal models show normal or near-normal myocardial blood flow (MBF) and myocardial oxygen consumption (MMRO(2)) in stunned myocardium.
- The severity of stunning in these models is linked to the degree of preceding ischemia.
Purpose of the Study:
- To demonstrate normal MBF and MMRO(2) in post-ischemic myocardium with reversible dysfunction in patients with coronary artery disease (CAD).
- To investigate the relationship between the severity of reversible dysfunction and the degree of preceding ischemia.
Main Methods:
- Positron emission tomography with oxygen 15-labelled water (H(2)(15)O) and oxygen 15-labelled oxygen ((15)O(2)) were used to measure MBF and MMRO(2) in 14 CAD patients.
- Quantitative echocardiography assessed global ejection fraction and regional left ventricular (LV) systolic function (SF) during and after dobutamine-induced ischemia.
Main Results:
- Dobutamine induced reversible reductions in ejection fraction and SF, which recovered within 120 minutes.
- MBF and MMRO(2) remained normal in regions with reversible LV dysfunction.
- The severity of LV dysfunction correlated with coronary stenosis severity and reduced peak MBF.
Conclusions:
- Dobutamine induces prolonged, reversible LV dysfunction in CAD patients even with normal MBF, confirming myocardial stunning.
- Myocardial stunning in this context is related to coronary stenosis severity and diminished peak MBF.
- Myocardial oxygen consumption in stunned myocardium is normal.
Objectives:
In patients with coronary artery disease (CAD), we sought to demonstrate normal myocardial blood flow (MBF) and myocardial oxygen consumption (MMRO(2)) to post-ischemic myocardium that exhibited reversible dysfunction and the relation between the severity of the dysfunction and the preceding ischemia.
Background:
In animal models of stunning, MBF and MMRO(2) are normal or near normal, and the severity of stunning is related to the degree of the preceding ischemia.
Methods:
Myocardial blood flow and MMRO(2) were measured using positron emission tomography and oxygen 15-labelled water (H(2)(15)O) and oxygen 15-labelled oxygen ((15)O(2)), respectively, in 14 patients with CAD and normal left ventricular (LV) function. Global ejection fraction and regional LV systolic function (SF) were measured using quantitative echocardiography during and after dobutamine-induced ischemia.
Results:
Ejection fraction and SF were reduced 30 min after dobutamine (both: p < 0.01) but recovered by 120 min. Myocardial blood flow (ml/min per g) to regions with reversible LV dysfunction was normal at baseline and during dysfunction (0.88 [0.82 to 0.99] and 1.09 [0.75 to 1.37], respectively, p = NS) as was MMRO(2) (ml/min per 100 g) (16.64 [10.16 to 16.18] and 11.68 [8.43 to 15.30] respectively, p = NS). Left ventricular dysfunction was related to stenosis severity and peak MBF. Regions were divided into those subtended by a stenosis of <50%, 50% to 80% and >80% luminal diameter. Systolic function 30 min after dobutamine was 93.9% (83.4% to 104.4%) (p = NS), 85.4% (80.0% to 90.9%) and 67.4% (56.2% to 78.7%) (both: p < 0.001), respectively. Peak MBF was 2.0 (1.71 to 2.31), 1.75 (1.65 to 1.85) (p = 0.01 compared with <50%) and 1.47 (1.33 to 1.60) (p = 0.03 compared with 50% to 80% and p = 0.002 compared with <50%), respectively.
Conclusions:
In patients with CAD, dobutamine produces prolonged, but reversible, LV dysfunction when MBF is normal, confirming stunning. This stunning is related to the severity of the coronary stenosis and the reduction in peak MBF. Myocardial oxygen consumption to stunned myocardium is normal.
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