Treadmill exercise test with dual isotope scintigraphy documents the second window of preconditioning in humans

In experimental studies, two windows of preconditioning have been identified, one lasting 1-2h and a second one (SWOP) starting 24h later and lasting 3-4 days. We sought to document SWOP in humans, using scintigraphy as an objective method of imaging.

Nineteen male patients, aged 62+/-7 years with documented coronary artery disease underwent two treadmill exercise tests (at baseline and 30 h later) and three tomographic perfusion studies (during the first exercise test, during the redistribution phase 4 h later and during the second exercise test 30 h later) with two different isotopes. Thallium-201 (TL) was used for the assessment of the first exercise and the redistribution phase, whereas technetium 99m tetrofosmin (TET) was used 30 h later for the evaluation of SWOP. Both exercise tests terminated at the same time-point. The distribution of TL and TET uptake was analyzed qualitatively using a 5-point scale on a 17-segment myocardial model. Perfusion score was derived by summing the uptake of all segments, while total perfusion defect by subtracting the polar map of the first exercise test from that of the second exercise test.

Anginal symptoms were reported by 13 of 19 patients (68%) in the first test versus only 2 of 19 patients (11%) in the second one (p=0.001). The mean maximum ST segment depression was significantly reduced in the second test (from 1.58+/-0.73 to 0.82+/-1.07, p<0.01). Similarly, the perfusion score was reduced from 21.0+/-7.4 to 14.2+/-5.7 in the second test (p<0.01) and the total defect size from 24+/-16 to 12+/-14 (p<0.01).

The myocardial perfusion improvement during the second exercise study confirms objectively the existence of SWOP in humans.