Multi-center study of inter-rater reproducibility, image quality, and diagnostic accuracy of CZT versus conventional SPECT myocardial perfusion imaging.

BACKGROUND: Cadmium-zinc-telluride (CZT)-based detectors exhibit higher diagnostic sensitivity in myocardial perfusion imaging (MPI) than conventional Anger-MPI for detection of coronary artery disease (CAD); however, reduced specificity and diagnostic accuracy of CZT-MPI were observed. This study aims to compare these different camera systems and to examine the degree of inter-rater reproducibility among readers with varying experience in MPI. METHODS: 83 patients who underwent double stress/rest examinations using both a CZT and conventional SPECT cameras within one visit were included. Anonymized and randomized MPI-images were distributed to 15 international readers using a standardized questionnaire. Subsequent coronary angiography findings of ten patients served as a reference for analysis of sensitivity and specificity. RESULTS: Image quality was significantly better in CZT-MPI with significantly lower breast attenuation (P < 0.05). CZT-MPI exhibited higher sensitivity than Anger-MPI (87.5% vs. 62.5%) and significantly reduced specificity (40% vs. 100%). Readers experienced with both camera systems had the highest inter-rater agreement indicating higher reproducibility (CZT 0.54 vs. conv. 0.49, P < 0.05). CONCLUSIONS: Higher diagnostic sensitivity of CZT-MPI offers advantages in detection of CAD yet potentially of at the cost of reduced specificity, therefore it requires special training and a differentiated evaluation approach, especially for non-experienced readers with such camera systems.

Differential risk reclassification improvement by exercise testing and myocardial perfusion imaging in patients with suspected and known coronary artery disease.

OBJECTIVE: The objective of this study is to compare the incremental prognostic and net risk reclassification value of exercise testing alone vs exercise myocardial perfusion imaging (MPI) for estimating the risk of death in patients with suspected and known coronary artery disease (CAD). METHODS: 6702 patients with suspected CAD and 2008 with known CAD had treadmill exercise MPI and were followed for 2.5 ± 0.9 years for the occurrence of all-cause death. The estimation of risk of death and net reclassification improvement (NRI) were examined in three models. Model 1: clinical variables; Model 2: model 1+Duke Treadmill Score; and Model 3: model 2+ MPI variables. Risk estimates were categorized as <1%, 1-3%, and >3% risk of death per year. RESULTS: In patients with suspected CAD, the global Chi-square for predicting risk of death increased significantly for Model 2 compared to Model 1 (74.78 vs 63.86 to (P = .001). However, adding MPI variables in Model 3 did not further improve predictive value (Chi-square 79.38, P = .10). In patients with suspected CAD risk, reclassification improved significantly in Model 2 over Model 1 (NRI = 0.12, 95% CI 0.02 to 0.22, P = .019), but not in Model 3 (NRI = 0.0009, 95% CI -0.072 to 0.070; P = .98). In contrast, in patients with known CAD Model 2 did not yield significant improvements for predicting risk and risk reclassification compared to Model 1. However, global Chi-square of Model 3 was significantly higher than that of Model 2 (30.03 vs 6.56, P < .0001) with associated significant reclassification improvement (NRI = 0.26 95% CI 0.067 to 0.46. P = .0084). CONCLUSION: Risk reclassification by diagnostic testing is importantly influenced by baseline characteristics of patient cohorts. In patients with suspected CAD, NRI is predominately achieved by exercise variables, whereas in patients with known CAD, greatest NRI is obtained by MPI variables.

Single-photon emission computed tomography myocardial perfusion imaging-assessed stress perfusion defect severity is associated with mortality independent of ethnicity in an Asian population.

BACKGROUND: Ischemic heart disease is growing by epidemic proportions in Asia. Among patients in Western populations with similar myocardial perfusion imaging (MPI) ischemia severity, ethnicity is independently associated with mortality. We aimed to determine the differential prognostic value of MPI abnormality severity among three major Asian ethnic groups. METHODS: From 16,921 consecutive patients, we used summed stress score to define increasing abnormal scan severity groups (minimal, mild, moderate, and severe) among Chinese, Indian, and Malay patients. We determined mortality from the national death registry. Using multivariable Cox regression models, we examined the association between ethnicity and mortality. RESULTS: Chinese patients were older than Indians or Malays. Annual all-cause death rates increased with increasing abnormal scan severity in all three ethnicities. After adjustment, ethnicity was not associated with mortality. With Chinese as the reference group, adjusted hazard ratio and 95% CI for Malays and Indians were 1.29 (0.95-1.77) and 1.06 (0.74-1.50) in the minimally abnormal scan group, and 1.20 (0.75-1.91) and 0.82 (0.47-1.45) in the severely abnormal scan group, respectively. CONCLUSIONS: Mortality risk is related to the severity of scan abnormality and is independent of ethnicity in Asians. Our findings emphasize the continued utility of MPI in guiding risk stratification in Asia.

Going beyond summed stress scores: Correlating global and territorial coronary flow reserve by single photon emission tomography with routine myocardial perfusion imaging.

a Background: Technological advancement in the recent years has enabled the application of single photon emission tomography (SPECT) to evaluate myocardial blood flow (MBF). This method offers increased sensitivity in the assessment of coronary health, quantifiable through non-invasive imaging beyond the more conventional methods such as with myocardial perfusion imaging (MPI). b Aims: To correlate MBF, derived by dynamic SPECT, both global and by coronary territories to the summed stress scores (SSS) on conventional MPI. c Methods: Images obtained from dipyridamole-gated SPECT MPI stress and rest studies performed on recruited subjects were examined. We calculated the global and regional coronary flow reserve (CFR) via a standard software package, taken as the ratio of stress MBF to rest MBF, using CFR<2.5 as the cut off. d Results: Amongst the 90 recruited subjects (mean age 67 ± 8 years; of which 76% were males), 49% had MPI within normal limits (summed stress score (SSS) 0-3; Left ventricular ejection fraction (LVEF) > 50%). We observed a progressive reduction in global and regional CFR across the normal SSS category to that of severely abnormal (SSS >13). Reduced global CFR with correspondent lower CFR across the regional arteries were detected in scans within normal limits of MPI scans in subjects who were older (69 ± 7 vs. 62 ± 9 years, p = 0.034). Decreasing CFR was significantly associated with increasing age across the regional arteries. e Conclusion: In our study we depict the global and regional MBF values obtained via SPECT MPI in correlation to the respective SSS categories. Our data proposes that dynamic SPECT has a part in refining cardiac risk stratification, particularly in the older adult population, who are at greater risk.

Correlation between clinical outcomes and appropriateness grading for referral to myocardial perfusion imaging for preoperative evaluation prior to non-cardiac surgery.

BACKGROUND: In a previous study, we have found that referral to myocardial perfusion imaging(MPI) for preoperative evaluation of patients before non-cardiac surgery was the most common cause of inappropriate referral based on AHA/ACC Appropriate Use Guidelines, though 40% of scans graded as inappropriate had abnormal MPI results. The aim of this study was to correlate appropriateness grading with (1) the outcome of MPI scans, and (2) the clinical outcome of patients after surgery, so as to determine if the predictive value of MPI was related to appropriateness grading. METHODS: All consecutive patients referred to the MPI laboratory of our center from March 2009 to July 2009 for preoperative risk stratification were prospectively studied. Patients' medical records and stress data were collected, and all imaging results were recorded. Based on appropriate use criteria (AUC), MPI studies were classified into appropriate, inappropriate, uncertain or unclassified. MPI studies were classified on the basis of their results into normal or abnormal scans. Primary clinical outcome measured was the occurrence of any major cardiac and cerebrovascular event during follow-up up to 90 days. RESULTS: There were 176 referrals for preoperative evaluation. 39.8% (n 5 70) of these referrals were graded as inappropriate. Based on AUC, referrals for MPI in intermediate- and high-risk groups with poor functional class were graded as appropriate, while referrals for MPI in low-risk and intermediate risk groups with normal functional class were graded as inappropriate referrals. The overall event rate was 6.25%. Cumulative death rate at 90 days was 1.7%, non-fatal MI 4%, and occurrence of stroke occurred in 0.6%. The primary outcome was higher in the intermediate group with poor functional class (13%) and high-risk group (64%) than the low-risk and intermediate risk groups with good functional class (4%). In the high-risk group, an abnormal MPI scan was associated with an extremely high event rate (50%) that was significantly greater than the event rate in patients with a normal MPI result (14%) (P 5 .01). Although 40% of preoperative low-risk and intermediate risk patients had an abnormal MPI result, their over all event rates were low (0 and 4%, respectively), with no difference in the rate of events between patients with normal and abnormal MPI scans in the inappropriate group. CONCLUSIONS: In conclusion, in correlating the relationship between appropriateness grading by AUC with the outcome of MPI scans and subsequent event rates, we found that MPI results predicted outcome in appropriately tested patients, but not in patients whose tests were classified as inappropriate, in whom event rates were low, regardless of the results of testing. Our findings support the AUC recommendations for the selective role of testing in preoperative risk stratification,which use the type of surgery and functional class to determine the appropriateness of referral.

Evaluation of the American College of Cardiology Foundation/American Society of Nuclear Cardiology appropriateness criteria for SPECT myocardial perfusion imaging in an Asian tertiary cardiac center.

BACKGROUND: Appropriate use criteria (AUC) for SPECT MPI have been published to address concern about the growth of cardiac imaging studies and the effective use of imaging, but there is no published data on its role outside the United States. METHODS: All consecutive patients referred to the MPI laboratory of our center from February 16 to June 19, 2009 were prospectively studied. Patients' medical records and stress data were collected and all imaging results were recorded. Based on AUC, MPI studies were classified into appropriate, inappropriate, uncertain, or unclassified. MPI studies were classified on the basis of their results into normal or abnormal scans. RESULTS: There were 1,623 patients (mean age 61 years ± 11, 61% males). Most common indications for SPECT were evaluation of ischemic equivalent for coronary artery disease (CAD), risk assessment post-revascularization, and preoperative evaluation for non-cardiac surgery. 10% of referrals were classified as inappropriate, 5% uncertain, and 3% unclassified. Women (48.4% vs 40.6% for men, P = .063) and asymptomatic patients (50.2% vs 14.3% for symptomatic, P < .001) had a higher proportion of inappropriate studies. The preoperative group had the highest proportion of inappropriate studies (59%). Appropriate referrals had a higher proportion of abnormal SPECT results than inappropriate referrals (40% vs 27%, OR 2.08, 95% CI 1.56-2.77, P < .001). CONCLUSIONS: The pattern of referrals for SPECT MPI in an Asian center appears to vary from published reports in the United States. Preoperative evaluation for low-risk surgery appears to be the most common source of inappropriate referrals in our institution. Inappropriate referrals have a higher proportion of normal studies, but 27% were still reported as abnormal.

Impact of COVID-19 Pandemic on Cardiovascular Testing in Asia: The IAEA INCAPS-COVID Study.

Background: The coronavirus disease-2019 (COVID-19) pandemic significantly affected management of cardiovascular disease around the world. The effect of the pandemic on volume of cardiovascular diagnostic procedures is not known. Objectives: This study sought to evaluate the effects of the early phase of the COVID-19 pandemic on cardiovascular diagnostic procedures and safety practices in Asia. Methods: The International Atomic Energy Agency conducted a worldwide survey to assess changes in cardiovascular procedure volume and safety practices caused by COVID-19. Testing volumes were reported for March 2020 and April 2020 and were compared to those from March 2019. Data from 180 centers across 33 Asian countries were grouped into 4 subregions for comparison. Results: Procedure volumes decreased by 47% from March 2019 to March 2020, showing recovery from March 2020 to April 2020 in Eastern Asia, particularly in China. The majority of centers cancelled outpatient activities and increased time per study. Practice changes included implementing physical distancing and restricting visitors. Although COVID testing was not commonly performed, it was conducted in one-third of facilities in Eastern Asia. The most severe reductions in procedure volumes were observed in lower-income countries, where volumes decreased 81% from March 2019 to April 2020. Conclusions: The COVID-19 pandemic in Asia caused significant reductions in cardiovascular diagnostic procedures, particularly in low-income countries. Further studies on effects of COVID-19 on cardiovascular outcomes and changes in care delivery are warranted.

Assessing the need for nuclear cardiology and other advanced cardiac imaging modalities in the developing world.

BACKGROUND: In 2005, 80% of cardiovascular disease (CVD) deaths occurred in low- to middle-income countries (i.e., developing nations). Cardiovascular imaging, such as myocardial perfusion SPECT, is one method that may be applied to detect and foster improved detection of at-risk patients. This document will review the availability and utilization for nuclear cardiology procedures worldwide and propose strategies to devise regional centers of excellence to achieve quality imaging around the world. METHODS: As a means to establish the current state of nuclear cardiology, International Atomic Energy Agency member and non-member states were queried as to annual utilization of nuclear cardiology procedures. Other sources for imaging statistics included data from medical societies (American Society of Nuclear Cardiology, European Society of Cardiology, and the European Association of Nuclear Medicine) and nuclear cardiology working groups within several nations. Utilization was calculated by dividing annual procedural volume by 2007 population statistics (/100,000) and categorized as high (>1,000/100,000), moderate-high (250-999/100,000), moderate (100-249/100,000), low-moderate (50-99/100,000) and low (<50/100,000). RESULTS: High nuclear cardiology utilization was reported in the United States, Canada, and Israel. Most Western European countries, Australia, and Japan reported moderate-high utilization. With the exception of Argentina, Brazil, Colombia and Uruguay, South America had low usage. This was also noted across Eastern Europe, Russia, and Asia. Utilization patterns generally mirrored each country's gross domestic product. However, nuclear cardiology utilization was higher for developing countries neighboring moderate-high "user" countries (e.g., Algeria and Egypt); perhaps the result of accessible high-quality training programs. CONCLUSIONS: Worldwide utilization patterns for nuclear cardiology vary substantially and may be influenced by physician access to training and education programs. Development of regional training centers of excellence can guide utilization of nuclear cardiology through the application of guideline- and appropriateness-driven testing, training, continuing education, and quality assurance programs aiding developing nations to confront the epidemics of CVD.

Advanced analyses of computed tomography coronary angiography can help discriminate ischemic lesions.

BACKGROUND: Computed tomography coronary angiography (CTCA) image analysis enables plaque characterization and non-invasive fractional flow reserve (FFR) calculation. We analyzed various parameters derived from CTCA images and evaluated their associations with ischemia. METHODS: 49 (61 lesions) patients underwent CTCA and invasive FFR. Lesions with diameter stenosis (DS) ≥ 50% were considered obstructive. CTCA image processing incorporating analytical and numerical methods were used to quantify anatomical parameters of lesion length (LL) and minimum lumen area (MLA); plaque characteristic parameters of plaque volume, low attenuation plaque (LAP) volume, dense calcium volume (DCV), normalized plaque volume (NP Vol), plaque burden, eccentricity index and napkin-ring (NR) sign; and hemodynamic parameters of resistance index, stenosis flow reserve (SFR) and FFRB. Ischemia was defined as FFR ≤ 0.8. RESULTS: Plaque burden and plaque volume were inversely related to FFR. Multivariable logistic regression analysis identified the best anatomical, plaque and hemodynamic predictors, respectively, as DS (≥50% vs <50%; OR: 8.0; 95% CI: 1.6-39.4), normalized plaque volume (NP Vol) (≥4.3 vs <4.3; OR: 3.9; 95% CI: 1.1-14.0) and NR Sign (0 vs 1; OR: 13.6; 95% CI: 1.3-146.1), and FFRB (≤0.8 vs >0.8; OR: 44.4; 95% CI: 8.8-224.8). AUC increased from 0.70 with DS as the sole predictor to 0.81 after adding NP Vol and NR Sign; further addition of FFRB increased AUC to 0.93. CONCLUSION: Normalized plaque volume, napkin-ring derived from plaque analysis, and FFRB from numerical simulations on CTCA images substantially improved discrimination of ischemic lesions, compared to assessment by DS alone.

Rate or Rhythm Control of Atrial Fibrillation - Pearls for the Internist.

Atrial fibrillation is an epidemic in Asia that is increasingly prevalent. Apart from stroke risk stratification and management of anticoagulation, physicians managing this group of patients also need to determine an optimal strategy in terms of rate or rhythm control. With new techniques of catheter ablation to maintain patients in sinus rhythm, patients with atrial fibrillation now have more options for treatment, on top of pharmacological methods. This paper aims to review the current evidence for rate and rhythm control in both general patients and subgroups of interest commonly encountered in clinical practices such as obesity, heart failure and thyroid disease.

Long-Term Prognostic Value of Appropriate Myocardial Perfusion Imaging.

Appropriate use criteria (AUC) for single-photon emission computed tomography myocardial perfusion images (SPECT-MPIs) were developed to address the growth of cardiac imaging studies. Long-term prognostic value of AUC in SPECT-MPI has not been tested in existing cohorts. We sought to determine the long-term prognostic value of MPI classified as appropriate. AUC was evaluated in a prospectively designed cohort of patients who underwent clinically indicated MPI. MPI studies were classified based on 2009 AUC for SPECT-MPI. Data regarding downstream coronary angiography (cath), revascularization and all-cause mortality, cardiac death, and nonfatal myocardial infarction (MI) were collected from national registries. Among n = 1,129 MPI scans that received an appropriate grading, 148 all-cause deaths, 109 MIs, 58 cardiac deaths, 152 caths, 113 revascularization procedures occurred over a mean follow-up period of 5.4 ± 1.2 years (0.9% cardiac death rate per year, 1.8% MI rate per year). Most of the scans were low-risk normal MPI scans (summed stress score ≤3; 74.1%). An abnormal scan was associated with higher rates of MI (19.5% vs 6.2%, hazard ratio 1.72, p = 0.017) and cardiac death (13.4% vs 2.3%, hazard ratio 2.12, p = 0.016). In conclusion, MPI scans classified as appropriate have long-term prognostic value, despite a high proportion of low-risk scans. This provides support for clinicians to consider the use of appropriate grading in addition to MPI scan results in patient management.

Simplified Models of Non-Invasive Fractional Flow Reserve Based on CT Images.

Invasive fractional flow reserve (FFR) is the gold standard to assess the functional coronary stenosis. The non-invasive assessment of diameter stenosis (DS) using coronary computed tomography angiography (CTA) has high false positive rate in contrast to FFR. Combining CTA with computational fluid dynamics (CFD), recent studies have shown promising predictions of FFRCT for superior assessment of lesion severity over CTA alone. The CFD models tend to be computationally expensive, however, and require several hours for completing analysis. Here, we introduce simplified models to predict noninvasive FFR at substantially less computational time. In this retrospective pilot study, 21 patients received coronary CTA. Subsequently a total of 32 vessels underwent invasive FFR measurement. For each vessel, FFR based on steady-state and analytical models (FFRSS and FFRAM, respectively) were calculated non-invasively based on CTA and compared with FFR. The accuracy, sensitivity, specificity, positive predictive value and negative predictive value were 90.6% (87.5%), 80.0% (80.0%), 95.5% (90.9%), 88.9% (80.0%) and 91.3% (90.9%) respectively for FFRSS (and FFRAM) on a per-vessel basis, and were 75.0%, 50.0%, 86.4%, 62.5% and 79.2% respectively for DS. The area under the receiver operating characteristic curve (AUC) was 0.963, 0.954 and 0.741 for FFRSS, FFRAM and DS respectively, on a per-patient level. The results suggest that the CTA-derived FFRSS performed well in contrast to invasive FFR and they had better diagnostic performance than DS from CTA in the identification of functionally significant lesions. In contrast to FFRCT, FFRSS requires much less computational time.

Hemodynamic analysis of patient-specific coronary artery tree.

Local hemodynamic parameters, such as wall shear stress (WSS), oscillatory shear index and relative resident time (RRT), have been linked to coronary plaque initiation and progression. In this study, a left coronary artery tree model was reconstructed from computed tomography angiography images of a patient with multiple stenoses. The geometry of the coronary artery tree model was virtually restored by eliminating the lesions, essentially re-creating the virtually healthy artery anatomy. Using numerical simulations, flow characteristics and hemodynamic parameter distributions in the stenosed and virtually healthy models were investigated. In the virtually healthy artery model, disturbed flows were found at four locations, prone to initialization of plaque formation. Low WSS and high RRT were exhibited in three of the four locations, and high WSS and low RRT were exhibited in the fourth. These findings suggest that coronary plaque is more likely to form in locations with disturbed flow conditions characterized by low WSS and high RRT or high WSS and low RRT. In addition, clinical index of fractional flow reserve was found to significantly correlate with blood flow rate, rather than anatomic parameters, such as diameter stenosis, which implied the importance of hemodynamic environment in stenosis formation.