Correct spatial normalization of myocardial perfusion SPECT improves detection of multivessel coronary artery disease

Artifacts in Quantitative analysis of myocardial perfusion SPECT, using Cedars-Sinai QPS Software

Quantitative analysis of myocardial perfusion Single photon emission computerized tomography (SPECT) images is increasingly applied in modern nuclear cardiology practice, assisting in the interpretation of myocardial perfusion images (MPI). There are different extensively validated state-of-the-art software packages, including QPS (cedars-Sinai), Corridor 4DM (University of Michigan) and Emory cardiac toolbox (Emory university), providing highly accurate and reproducible data. However, these software packages may suffer from potential artifacts related to patient or technical factors. By recognizing the source of such artifacts, the interpreting physician can avoid misinterpretation of MPI study. In this review, we discuss some of technical pitfalls that may occur in Quantitative Perfusion SPECT software (QPS, cedars-Sinai Medical center).

Effects of Transendocardial Delivery of Bone Marrow-Derived CD133+ Cells on Left Ventricle Perfusion and Function in Patients With Refractory Angina: Final Results of Randomized, Double-Blinded, Placebo-Controlled REGENT-VSEL Trial

RATIONALE

New therapies for refractory angina are needed.

OBJECTIVE

Assessment of transendocardial delivery of bone marrow CD133⁺ cells in patients with refractory angina.

METHODS AND RESULTS

Randomized, double-blinded, placebo-controlled trial enrolled 31 patients with recurrent Canadian Cardiovascular Society II-IV angina, despite optimal medical therapy, ≥1 myocardial segment with inducible ischemia in Tc-99m SPECT who underwent bone marrow biopsy and were allocated to cells (n=16) or placebo (n=15). Primary end point was absolute change in myocardial ischemia by SPECT. Secondary end points were left ventricular function and volumes by magnetic resonance imaging and angina severity. After 4 months, there were no significant differences in extent of inducible ischemia between groups (summed difference score mean [±SD]: 2.60 [2.6] versus 3.63 [3.6], P=0.52; total perfusion deficit: 3.60 [3.6] versus 5.01 [4.3], P=0.32; absolute changes of summed difference score: -1.38 [5.2] versus -0.73 [1.9], P=0.65; and total perfusion deficit: -1.33 [3.3] versus -2.19 [6.6], P=0.65). There was a significant reduction of left ventricular volumes (end-systolic volume: -4.3 [11.3] versus 7.4 [11.8], P=0.02; end-diastolic volume: -9.1 [14.9] versus 7.4 [15.8], P=0.02) and no significant change of left ventricular ejection fraction in the cell group. There was no difference in number of patients showing improvement of ≥1 Canadian Cardiovascular Society class after 1 (41.7% versus 58.3%; P=0.68), 4 (50% versus 33.3%; P=0.63), 6 (70% versus 50.0%; P=0.42), and 12 months (55.6% versus 81.8%; P=0.33) and use of nitrates after 12 months.

CONCLUSION

Transendocardial CD133⁺ cell therapy was safe. Study was underpowered to conclusively validate the efficacy, but it did not show a significant reduction of myocardial ischemia and angina versus placebo.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01660581.

Very high coronary artery calcium score with normal myocardial perfusion SPECT imaging is associated with a moderate incidence of severe coronary artery disease

PURPOSE

Myocardial perfusion imaging (MPI) has limitations in the presence of balanced multivessel disease (MVD) and left main (LM) coronary artery disease, occasionally resulting in false-normal results despite the high cardiovascular risk associated with this condition. The purpose of this study was to assess the incidence of severe coronary artery disease (CAD) in the presence of a very high Agatston coronary artery calcium (CAC) score (>1,000) in stable symptomatic patients without known CAD but with normal MPI results.

METHODS

A total of 2,659 prospectively acquired consecutive patients were referred for MPI and evaluation of CAC score by CT. Of this patient population, 8 % (222/2,659) had ischemia without myocardial infarction (MI) on MPIand 11 % (298/2,659) had abnormal MPI (MI and/or ischemia). On presentation 1 % of the patients (26/2,659) were symptomatic, had a CAC score >1,000 and normal MPI results. The definition of normal MPI was strict and included a normal hemodynamic response without ischemic ECG changes and normal imaging, particularly absence of transient ischemic dilation. All of these 26 patients with a CAC score >1,000 and normal MPI findings underwent cardiac catheterization.

RESULTS

Of these 26 patients, 58 % (15/26) had severe disease (≥70 % stenosis) leading to revascularization. Of this group, 47 % (7/15) underwent percutaneous intervention, and 53 % (8/15) underwent coronary artery bypass grafting. All of these 15 patients had either MVD (14/15) or LM coronary artery disease (1/15), and represented 0.6 % (15/2,659) of all referred patients (95 % CI 0.3 - 0.9 %). The majority, 90 % (8/9), had severe CAD with typical chest pain.

CONCLUSION

A very high CAC score (>1,000) with normal MPI in a small subset of symptomatically stable patients was associated with a moderate incidence of severe CAD (95 % CI 37 - 77 %). Larger studies and/or a meta-analysis of small studies are needed to more precisely estimate the incidence of CAD in this population. This study also supports the concept that a normal MPI result in patients with severe CAD may be due to balanced MVD.

Improved quantification and normal limits for myocardial perfusion stress-rest change

We aimed to improve the quantification of myocardial perfusion stress-rest changes in myocardial perfusion SPECT (MPS) studies for the optimal automatic detection of ischemia and coronary artery disease (CAD).

METHODS

Rest-stress (99m)Tc MPS studies (997 cases; 651 consecutive cases with correlating angiography and 346 cases with less than 5% likelihood (low likelihood [LLK]) of CAD) were analyzed. Normal limits for stress-rest changes were derived from additional LLK patients (40 women, 40 men). We computed the global stress-rest change (C-SR) by integrating direct stress-rest changes for each polar map pixel. Additionally, stress-rest change and total perfusion deficit (TPD) at stress were combined in 1 variable (C-TPD) for the optimal detection of CAD.

RESULTS

The area under the receiver-operating-characteristic curve (AUC) for C-SR (0.92) was larger than that for stress TPD-rest TPD (0.88) for the identification of stenosis of 70% or more (P < 0.0001). AUC (0.94) and sensitivity (90%) for C-TPD were higher than those for stress TPD (0.91 and 83%, respectively) (P < 0.0001), whereas specificity remained the same (81%).

CONCLUSION

C-SR and C-TPD provide higher diagnostic performance than difference between stress and rest TPD or stress hypoperfusion analysis.

Anatomic correlates of a normal perfusion scan using 64-slice computed tomographic coronary angiography

Both myocardial perfusion imaging (MPI) and multislice computed tomography (MSCT) are currently used to detect coronary artery disease (CAD). However, MSCT permits early detection of atherosclerosis while myocardial perfusion is still normal. In addition, MPI results can be normal despite the presence of high-risk CAD (left main and balanced 3-vessel CAD). In this study, the range of anatomic findings using MSCT in patients with normal MPI results was evaluated. In 180 patients presenting with chest pain, MPI (with gated single-photon emission computed tomography) and 64-slice MSCT were performed. In patients with normal MPI results, prevalences of completely normal coronary arteries, nonobstructive CAD, and obstructive CAD were determined using MSCT. The occurrence of high-risk CAD, including left main and 3-vessel disease, was also evaluated. Normal MPI and adequate MSCT findings were obtained in 97 patients (54%; 50% women; average age 58 +/- 12 years; 5% with known CAD). A total of 38 patients (39%) showed normal coronary anatomy, whereas nonsignificant and significant CAD were observed in 37 (38%) and 18 patients (19%), respectively. Importantly, only 4 patients (4%) presented with high-risk CAD using 64-slice MSCT, 2 with left main and 2 with 3-vessel disease. In conclusion, a normal MPI result can be associated with a wide range of anatomic observations and cannot exclude the presence of both nonobstructive and obstructive CAD. However, importantly, the prevalence of high-risk CAD was rare.

Attenuation correction reveals gender-related differences in the normal values of transient ischemic dilation index in rest-exercise stress sestamibi myocardial perfusion imaging

BACKGROUND

Transient ischemic dilation (TID) has been established as an important independent marker of severe and extensive coronary artery disease (CAD) in myocardial perfusion imaging (MPI). The accuracy of the TID index is dependent on a well-determined threshold (normal limits) between normal and abnormal values for each study protocol. To date, the effects of neither gender nor attenuation correction (AC) on TID normal limits have been established. Thus, the objectives of this study were to determine if AC processing changes the normal value of the TID index and if there were gender-related differences in the TID index of normal patients who had undergone rest/exercise-stress technetium-99m sestamibi MPI.

METHODS AND RESULTS

Seventy-five patients (33 women, 42 men; mean age, 57.7 +/- 11.7 y and 55.9 +/- 10.0 y, respectively) with less than a 5% likelihood of CAD, who had undergone low-dose rest/high-dose exercise-stress Tc-99m sestamibi MPI, were studied. All studies were acquired using simultaneous emission/transmission scans and were corrected for attenuation, scatter, and resolution effects using the ExSPECT II method. Both the AC and non-AC studies were analyzed using the Emory Cardiac Toolbox (ECTb; Syntermed, Inc, Atlanta, Ga) quantitative software. The TID index was calculated automatically as the ratio of stress mean left ventricular volumes to rest mean left ventricular volumes by ECTb. Patients were grouped by gender and the TID indices from AC and non-AC studies were compared. Linear regressions of the TID index and body mass index were analyzed to exclude differences in body size between male and female patients as a confounding factor in gender-related differences in TID. The TID index upper normal limits were calculated as the mean value plus 2 standard deviations (SDs). AC processing did not change the TID index significantly whether the genders were combined or separated (AC TID = 0.97 +/- 0.14 vs non-AC TID = 0.98 +/- 0.12 for all patients). Female patients showed higher mean TID indices than male patients in both AC (1.01 +/- 0.15 vs 0.95 +/- 0.12) and non-AC studies (1.00 +/- 0.15 vs. 0.97 +/- 0.10), but this difference was statistically significant only in AC studies (p = .03). TID indices remained constant across the range of body mass index studied. The TID index upper normal limit was 1.31 for female and 1.18 for male patients.

CONCLUSION

TID normal values for rest/exercise-stress Tc-99m sestamibi MPI are gender-dependent and not affected by AC processing. Thus, diagnosticians should take into account these gender-related differences, as compared with the traditional value generated from mostly male populations, to ensure both men and women have the same overall accuracy of using the TID index in the diagnosis and prognosis of CAD.

Automated quantification of myocardial perfusion SPECT using simplified normal limits

BACKGROUND

To simplify development of normal limits for myocardial perfusion SPECT (MPS), we implemented a quantification scheme in which normal limits are derived without visual scoring of abnormal scans or optimization of regional thresholds.

METHODS AND RESULTS

Normal limits were derived from same-day TI-201 rest/Tc-99m-sestamibi stress scans of male (n = 40) and female (n = 40) low-likelihood patients. Defect extent, total perfusion deficit (TPD), and regional perfusion extents were derived by comparison to normal limits in polar-map coordinates. MPS scans from 256 consecutive patients without known coronary artery disease, who underwent coronary angiography, were analyzed. The new method of quantification (TPD) was compared with our previously developed quantification system and visual scoring. The receiver operator characteristic area under the curve for detection of 50% or greater stenoses by TPD (0.88 +/- 0.02) was higher than by visual scoring (0.83 +/- 0.03) ( P = .039) or standard quantification (0.82 +/- 0.03) ( P = .004). For detection of 70% or greater stenoses, it was higher for TPD (0.89 +/- 0.02) than for standard quantification (0.85 +/- 0.02) ( P = .014). Sensitivity and specificity were 93% and 79%, respectively, for TPD; 81% and 85%, respectively, for visual scoring; and 80% and 73%, respectively, for standard quantification. The use of stress mode-specific normal limits did not improve performance.

CONCLUSION

Simplified quantification achieves performance better than or equivalent to visual scoring or quantification based on per-segment visual optimization of abnormality thresholds.