Fast myocardial perfusion imaging with 99mTc in challenging patients using conventional SPECT cameras.

BACKGROUND: We attempted to validate the performance of a fast myocardial perfusion imaging (MPI) protocol in diagnostically challenging patients. METHODS: 78 patients with ΒΜΙ > 24.9, LVH or three vessels disease underwent two sequential gated-MPI studies. The first at 15 (Early Imaging, EI) and the second at 45 (Late Imaging, LI) minutes post 99mTc-injection, at both stress and rest. Counts over heart (H), liver (Liv) and subdiaphragmatic space (Sub) and image quality, and myocardial perfusion and function parameters were compared between the two protocols. Coronary angiography was performed within 2 months from MPI, and ROC analysis was used to compare the diagnostic accuracy for the detection of ≥50% diameter luminal stenosis. RESULTS: Quality was optimal-good in 93% of EI and 98% of LI studies (P = .12), H/Liv and stress H/Sub ratios were similar, but rest H/Sub ratio was lower in EI (P = .009). SSS [10 (0 to 46) vs 9 (0 to 36), P = .006] and SDS [3 (0 to 35) vs 2 (0 to 34), P = .02] were higher in EI protocol. LVEF, motion and thickening scores did not differ between the two protocols. A highly significant (P < .001) linear relationship with clinically negligible mean differences in Bland-Altman analysis was observed for all perfusion and function-related data. Sensitivity (EI 81%, LI 80%) and specificity (65% for both) did not differ (P = .23) between the two protocols. CONCLUSION: The fast protocol is technically feasible and diagnostically accurate compared to the established protocol in diagnostically challenging patients.

Prognostic value of the Duke treadmill score in octogenarians undergoing myocardial perfusion imaging.

OBJECTIVES/BACKGROUND: Although Duke treadmill score (DTS) is the most widely used risk stratification method in younger patients undergoing exercise treadmill test (ETT) its specific value in the elderly is not established. METHODS: 137 patients aged ≥80 years who underwent ETT myocardial perfusion imaging (MPI) were studied. DTS and MPI (including summed stress scores, SSS) related data were registered per patient and follow up was performed to document cardiac death (CD), myocardial infarction (MI) and late (>3 months) revascularization (LR). Kaplan Meir and Cox regression survival analysis were employed to determine the prognostic value of DTS in relation to MPI data for these endpoints. RESULTS: After a median follow up duration of 6.7 years 28 deaths, 7 CDs, 4 non fatal MIs and 12 LRs were observed. Incidence rates of CD/MI were significantly different only between low and high risk SSS categories (p = 0.044). Risk groups by DTS had no significant differences in survival free of CD/MI (p = 0.743) in contrast to risk groups according to SSS (p = 0.026), while both DTS and SSS based risk groups had significantly different survival free of CD/MI or LR. SSS was a significant univariate predictor of both CD/MI (HR 1.088, p = 0.019) and CD/MI or LR (HR 1.095, p < 0.001), but DTS only of the latter endpoint (HR 0.909, p = 0.003). CONCLUSIONS: In octogenarians DTS was found to be a significant predictor of the LR related endpoint but not of the hard endpoint of CD/MI, in contrast to SSS which was a powerful predictor of both soft and hard cardiac endpoints.

Reversible reduction of cardiac sympathetic innervation after coronary artery bypass graft surgery: an observational study using serial iodine 123-labeled meta-iodobenzyl-guanidine (MIBG) imaging.

OBJECTIVES: Various types of surgical and interventional procedures have been reported to cause cardiac sympathetic denervation. We aimed at evaluating the effects of coronary artery bypass grafting (CABG) in cardiac sympathetic innervation through meta-iodobenzyl-guanidine (MIBG) imaging. METHODS: MIBG imaging was performed in 21 patients with coronary artery disease (CAD) 1 day before and 1 week and 6 months after CABG with concomitant measurements of corrected QT interval. In each study we evaluated MIBG defect score in a 16-segment left ventricular model, MIBG-defect size (percent) from generated polar maps, and heart/mediastinum ratio. RESULTS: Mean MIBG defect score and size were increased (32 ± 9.5 vs 24 ± 5, P < .0001, and 49.5% ± 20.4% vs 37% ± 8.7%, P = .004, respectively) and mean heart/mediastinum ratio was reduced (1.5 ± 0.4 vs 1.9 ± 0.3, P < .0001) at 1 week after CABG. At 6 months these indices had no significant differences compared with their pre-CABG values. Mean corrected QT interval demonstrated no significant changes. Increase in MIBG score in the second imaging was associated with adverse events related to arrhythmia and myocardial dysfunction during the 6-month follow-up period in a binary logistic regression model. CONCLUSIONS: CABG is associated with clinically important but reversible reduction in cardiac sympathetic nerve function, with periprocedural effects (cardioplegia, hypothermia, ischemia, direct nerve injury) being possible mechanisms for this finding.

Stress test with dual isotope studies for the documentation of classical ischemic preconditioning.

OBJECTIVES: We investigated whether myocardial perfusion imaging (MPI) can demonstrate the effect of classical preconditioning. METHODS: 21 patients with documented coronary artery disease (stenosis>or=70%) underwent two exercise stress tests (EST) with concomitant MPI, using TL-201 for the first and tetrofosmin-Tc-99m for the second. A third MPI was performed at rest, using Tc-99m. Total defect score was derived by summing tracer uptake in a 17 segments left ventricle model, graded on a 5-point scale. Tomographic images were also analyzed quantitatively, to derive the total defect size. RESULTS: Maximum ST depression did not differ significantly between the two EST (2.2+/-1 vs 2.2+/-1 mm, p=NS), however in the second EST longer times for onset of ischemic changes (228+/-94 vs 265+/-103 s, p=0.01) and appearance of angina (282+/-153 vs 328+/-177 s, p=0.04) were observed. Exercise perfusion abnormalities were significantly lower in the second MPI, in terms of both total defect score (19.2+/-11.5 vs 10+/-10.4, p<0.0001) and total defect size (28.3+/-16.9 vs 13.8+/-15.8, p<0.0001). CONCLUSION: Significant improvement in perfusion pattern was demonstrated in the second MPI, accompanied by delayed appearance of ischemic manifestations. The improvement in myocardial perfusion extends far beyond the changes that can be attributed to differences in myocardial uptake between tracers, reflecting the effect of classical preconditioning.