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Exercise supplementation to dipyridamole
prevents hypotension, improves ECG sensitivity and increases
heart to liver activity ratio on Tc- 99m sestamibi imaging.
JV Vitola, JC Brambatti, FC Caligaris, LR
Lesse, PR Nogueira, AI Joaquim, M Loyo, FV Salis, EV Paiva, W
Chalela, JC Meneghetti. Heart Institutes of Rio Preto and São
Paulo, Brazil.
Dipyridamole can be used to evaluate patients
unable to exercise adequately. Unfortunately, it has limitations,
including frequent side effects, a low sensitivity of the
electrocardiogram (ECG), and the increased splancnic
vasodilation, leading to a high concentration of tracers in the
liver, frequently creating inferior wall artifacts. There are
benefits from adding exercise to dipyridamole, including a
reduction of thallium in the liver. Whether this also occurs
with Tc-99m sestamibi (MIBI), and to what degree, remains to be
shown. This is a pertinent question considering the differences
in biodistribution, elimination pathways and time interval for
imaging between these 2 tracers. Exercise supplementation also
increases ECG positivity, but the impact on ECG sensitivity and
specificity has not been determined. The current study was
designed to evaluate these effects. Ninety consecutive patients
undergoing dipyridamole myocardial SPECT, using MIBI, who were
limited but not completely disabled for exercise, were evaluated
using our protocol of exercise supplementation (DipEx).
Dipyridamole was infused over 4 minutes and exercise on the
treadmill was added after the third minute. The tracer was
injected always between minutes 6 and 9. The findings were
compared to a control group (Dip) made of 99 patients undergoing
dipyridamole infusion alone. All patients with left bundle
branch block, pacemaker and atrial fibrilation were excluded.
Patients tolerated well the protocol exercising 4.2 ± 1.3
minutes. Compared to Dip, patients on the DipEx group had no
hypotension (6 vs 0%, p=0.03) a higher sensitivity of the ECG to
detect ischemia (6% vs 34%, p=0.003), and a higher heart to
liver activity ratio (1.3 ± 0.4 vs 1.6 ± 0.5, p=0.0000). The
increase in ECG sensitivity on the DipEx group was associated
with a significant drop in specificity compared to the Dip group
(67 vs 100%, p=0.000001). In conclusion, our results show that
exercise supplementation to dipyridamole results in several
benefits during MIBI imaging, including a significant increase
in the heart to liver activity ratio and can be used in patients
who are not completely unable to exercise.
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