Exercise-induced myocardial perfusion abnormalities in sickle beta-thalassemia: Tc-99m tetrofosmin gated SPECT imaging study.
OBJECTIVE
To determine the mechanism of myocardial ischemia in patients with sickle beta-thalassemia, we performed a scintigraphic evaluation of myocardial perfusion during exercise.


METHODS
We studied 30 patients with sickle beta-thalassemia, (mean [+/-SD] age, 37 +/- 10 years) who had no electrocardiographic (ECG), radiographic, or echo-Doppler signs of pulmonary hypertension, left ventricular hypertrophy, or impaired contractility. All patients had a hemoglobin level greater than 7 g/dL. Treadmill exercise test was performed according to the Bruce protocol. Myocardial perfusion was assessed by single-photon emission computed tomography, using Tetrofosmin Tc-99 m Myoview as radiotracer, at peak exercise and again 4 hours later.


RESULTS
Eight patients (27%) developed stress-induced scintigraphic perfusion abnormalities that were reversible in all but 1 patient. Subsequent coronary angiograms were normal in all 8 patients. ST segment depression was seen during exercise in 5 of the 7 patients who had reversible perfusion defects. Except for a significantly greater white blood cell count, these 5 patients did not differ from the rest of patients by sex, age, hemoglobin level, percentage hemoglobin F, beta-thalassemia genotype, or risk factors for coronary artery disease. Three of the 5 patients with perfusion and ECG abnormalities (and another with only perfusion defects) developed a stress-induced sickling crisis.


CONCLUSIONS
Physical stress may induce myocardial ischemia in sickle beta-thalassemia patients with normal coronary arteries and elicit painful crises. The sickling process, activated by exercise, could be the common underlying mechanism.
Aessopos
A
A
First Department of Medicine, University of Athens, Medical School, Laiko Hospital, Athens, Greece.
Tsironi
M
M
Vassiliadis
I
I
Farmakis
D
D
Fountos
A
A
Voskaridou
E
E
Perakis
A
A
Defteraios
S
S
Loutradi
A
A
Loukopoulos
D
D
D000328:Adult; D000704:Analysis of Variance; D000755:Anemia, Sickle Cell / Q000503:physiopathology*; D003326:Coronary Circulation; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D018709:Statistics, Nonparametric; D015899:Tomography, Emission-Computed, Single-Photon; D017086:beta-Thalassemia / Q000503:physiopathology*
D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin