[Adenosine stress protocols for myocardial perfusion imaging]

Withholding or continuing beta-blocker treatment before dipyridamole myocardial perfusion imaging for the diagnosis of coronary artery disease? A randomized clinical trial

BACKGROUND

Although it has been shown that acute beta-blocker administration may reduce the presence or severity of myocardial perfusion defects with dipyridamole stress, little information is available about the potential effect of chronic beta-blocker treatment on the sensitivity of dipyridamole myocardial perfusion imaging (DMPI).

METHODS

As a randomized clinical trial, one hundred twenty patients (103 male and 17 female) with angiographically confirmed CAD who were on long-term beta blocker therapy (≥3 months) enrolled in a randomized clinical trial study. The patients were allocated into two groups: Group A (n=60) in whom the beta-blocker agent was discontinued for 72h before DMPI and Group B (n=60) without discontinuation of beta-blockers prior to DMPI.

RESULTS

No significant difference was noted between the groups concerning age, sex, type of the injected radiotracer and number of involved coronary vessels. The mean rank of total perfusion scores for whole myocardium (irrespective of reversibility or irreversibility) in group B was not significantly different from that of group A, (65.75 vs. 55.25, P=0.096). Regarding the only irreversible perfusion defects, the mean rank of perfusion score in group B was higher than that of group A for whole myocardium (72 vs. 49, P=0.0001); however, no difference was noted between two groups for only reversible perfusion defects (61.0 vs. 60.0, P=0.898). The overall sensitivity of DMPI for the diagnosis of CAD in group A (91.7%) was not statistically different from group B (90%).

CONCLUSION

Beta-blocker withholding before DMPI did not generally affect the sensitivity of the test for the diagnostic purposes in our study. Thus, beta-blocker withdrawal for just the purpose of diagnostic imaging is not mandatory particularly when medication discontinuation may cause the patients to face increased risk of heart events.

[Study of efficacy and safety of pharmacological stress tests in nuclear cardiology]

BACKGROUND/AIM

Treadmill test combined with myocardial perfusion scintigraphy (MPS) is a commonly used technique in the assessment of coronary artery disease. Many patients who cannot adequately perform exercise stress testing may nevertheless undergo pharmacological tests, most commonly with the vasodilator agents (adenosine and dipyridamole), as well as the positive inotropic agent dobutamine. Patients undergoing vasodilators stress testing with either dipyridamole or adenosine also perform simultaneous low-intensity exercise. The aim of this study was to compare various pharmacological stress tests alone or in combination with low intensity exercise as preparation for MPS in regard to incidence of adverse effects, quality of diagnostic image and the acquisition initial time.

METHODS

A total of 2 205 patients underwent pharmacological stress tests. Pharmacological stress test with adenosine was applied in 493 patients. In 405 of them we performed concomitant low level exercise (50 W) by bicycle ergometar (AdenoEX). In 88 of them we performed adenosine abbreviated protocol (AdenoSCAN). In 1 526 patients we performed pharmacological stress test with dipyridamole. In 871 of them we performed concomitant low level exercise (50 W) by bicycle ergometar (DipyEX), and in 775 we used only dipyridamole protocol (DipySCAN). In 186 patients we used pharmacological stress test with dobutamine. We followed side effects of adenosine, dipyiridamole and dobutamine, compared results between protocols with concomitant low level exercise and vasodilatators only. We also compared image quality, and suggested time of acquisition after stress test.

RESULTS

We found numerous side effects especially with adenosine, but these effects were short-lived and not required active interventions. Benefit with concomitant exercise in booth AdenoEX and DipyEX included decreased side effects (AdenoEX vs AdenoSCAN 620% vs 87%, respectively, and DipyEX vs DipySCAN 37% vs 59%, respectively) improved safety and patients tolerance, improved target-to-background ratios because of less subdiaphragmal activity, and earlier acquisition time. Because of producing a lot of arrhythmias (in 49% of patients) dobutamin was considered a last choice for pharmacological stress testing.

CONCLUSION

Safety and efficacy of vasodilatators (adenosine, dipyridamole) pharmacological stress tests are good, but with concomitant exercise even better. The safety and efficacy of adenosin are better than those of dipyridamole. AdenoEX protocol provides good safety and patients tolerancy. In light of these benefits we recommend AdenoEX whenever possible. Dobutamine is the last pharmacological toll for MPS.

[Diagnostic significance of myocardial perfusion scintigraphy in identification and localisation of culprit lesions in patients undergoing elective PTCA]

BACKGROUND/AIM

The coronary angiography provides information on the anatomical state of the coronary tree, while myocardial perfusion scintigraphy (MPI) facilitates the evaluation of the grade of ischaemia that a particular stenosis produces. The purpose of MPI is to detect the coronary stenosis that provokes the ischaemia and is termed the "culprit lesion". The aim of this study was to evaluate the accuracy of 1-day DypEX 99mTc-tetrofosmin tomography in the identification and localization of culprit lesion in the patients with known coronary artery disease (CAD).

METHODS

Ninety-one (91) patients with known CAD were studied. In all of them significant coronary narowing (> 75% luminal stenosis) was angiographically detected. All the patients were submitted to 2 i.v. injections of 99mTc-tetrofosmin, one in a peak of pharmacologic dipyridamole stress protocol with concomitant low level bicycle exercise 50W (DypEX) and the other 3 h after exercise. Quantification of regional tetrofosmin uptake was performed using short-axis myocardial tomogram that was divided on 17 segments for each study. Reversibility score (RS) > or =3 determinated culprit lesion. Two of segments with scor 5 (index of reversibility scor--IRS) in the territory of coronary artery stenoses determinated culprit lesion.

RESULTS

A total of 273 vascular territories (4641 segments) were analyzed before percutaneous coronary intervention (PCI). Overall sensivity, specificit, and accuracy using RS > or =3 and IRS were 90.1%, 87.1%, 89.4%, with positive predictive value 95.8%, and 94.1%, 93.3%, 94%, with positive predictive value 98%, respectively.

CONCLUSION

RS and IRS significantly improve sensitivity, specificity, and accuracy for determination of culprit lesion in patients undergoing PCI.