Regional myocardial blood flow reserve impairment and metabolic changes suggesting myocardial ischemia in patients with idiopathic dilated cardiomyopathy.
OBJECTIVE
We performed positron emission tomography (PET) to evaluate myocardial ischemia in patients with idiopathic dilated cardiomyopathy (IDC).


BACKGROUND
Patients with IDC have anatomically normal coronary arteries, and it has been assumed that myocardial ischemia does not occur.


METHODS
We studied 22 patients with IDC and 22 control subjects using PET with nitrogen-13 ammonia to measure myocardial blood flow (MBF) at rest and during dipyridamole-induced hyperemia. To investigate glucose metabolism, fluorine-18 deoxyglucose (18FDG) was used. For imaging of oxygen consumption, carbon-11 acetate clearance rate constants (k(mono)) were assessed at rest and during submaximal dobutamine infusion (20 microg/kg body weight per min).


RESULTS
Global MBF reserve (dipyridamole-induced) was impaired in patients with IDC versus control subjects (1.7 +/- 0.21 vs. 2.7 +/- 0.10, p < 0.05). In patients with IDC, MBF reserve correlated with left ventricular (LV) systolic wall stress (r = -0.61, p = 0.01). Furthermore, in 16 of 22 patients with IDC (derived by dipyridamole perfusion) mismatch (decreased flow/increased 18FDG uptake) was observed in 17 +/- 8% of the myocardium. The extent of mismatch correlated with LV systolic wall stress (r = 0.64, p = 0.02). The MBF reserve was lower in the mismatch regions than in the normal regions (1.58 +/- 0.13 vs. 1.90 +/- 0.18, p < 0.05). During dobutamine infusion k(mono) was higher in the mismatch regions than in the normal regions (0.104 +/- 0.017 vs. 0.087 +/- 0.016 min(-1), p < 0.05). In the mismatch regions 18FDG uptake correlated negatively with rest k(mono) (r = -0.65, p < 0.05), suggesting a switch from aerobic to anaerobic metabolism.


CONCLUSIONS
Patients with IDC have a decreased MBF reserve. In addition, low MBF reserve was paralleled by high LV systolic wall stress. These global observations were associated with substantial myocardial mismatch areas showing the lowest MBF reserves. In geographically identical regions an abnormal oxygen consumption pattern was seen together with a switch from aerobic to anaerobic metabolism. These data support the notion that regional myocardial ischemia plays a role in IDC.
van den Heuvel
A F
AF
Department of Cardiology, University Hospital Groningen, The Netherlands.
van Veldhuisen
D J
DJ
van der Wall
E E
EE
Blanksma
P K
PK
Siebelink
H M
HM
Vaalburg
W M
WM
van Gilst
W H
WH
Crijns
H J
HJ
D000328:Adult; D000368:Aged; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003326:Coronary Circulation / Q000502:physiology*; D004176:Dipyridamole; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D006940:Hyperemia / Q000000981:diagnostic imaging / Q000503:physiopathology; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology; D012016:Reference Values; D014055:Tomography, Emission-Computed; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000503:physiopathology
D019788:Fluorodeoxyglucose F18; D004176:Dipyridamole