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CLINICAL STUDY: MYOCARDIAL ISCHEMIA

Absolute blood flow and oxygenconsumption in stunned myocardiumin patients with coronary artery disease

^* MRC Clinical Sciences Centre and Division of Cardiology, National Heart and Lung Institute, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom

Manuscript received May 14, 2001; revised manuscript received October 19, 2001, accepted November 2, 2001.

^* Reprint requests and correspondence: Prof. Paolo Camici, MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College of Science, Technology and Medicine, Hammersmith Hospital, London, England W12 0NN, United Kingdom.
paolo.camici{at}csc.mrc.ac.uk

OBJECTIVES: In patients with coronary artery disease (CAD), we sought to demonstrate normal myocardial blood flow (MBF) and myocardial oxygen consumption (MMRO₂) 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 MMRO₂ are normal or near normal, and the severity of stunning is related to the degree of the preceding ischemia.

METHODS: Myocardial blood flow and MMRO₂ were measured using positron emission tomography and oxygen 15-labelled water (H₂¹⁵O) and oxygen 15-labelled oxygen (¹⁵O₂), 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 MMRO₂ (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.

Abbreviations and Acronyms   AP2CH   apical two-chamber   AP4CH   apical four-chamber   CAD   coronary artery disease   C15O   oxygen 15-labelled carbon monoxide   EF   ejection fraction   H215O   oxygen 15-labelled water   LV   left ventricular   MBF   myocardial blood flow   MMRO2   myocardial oxygen consumption   PET   positron emission tomography   RPP   rate pressure product   SBP   systolic blood pressure   SF   shortening fraction   SFnorm   regions not demonstrating post-ischemic dysfunction   SFdysfunction   regions demonstrating post-ischemic dysfunction   SPECT   single photon emission computed tomography   15O2   oxygen 15-labelled oxygen

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