Clinical utility of coronary calcium scoring after nonischemic myocardial perfusion imaging

Obtaining a Coronary Artery Calcium Score with Myocardial Perfusion Imaging

A coronary artery calcium score adds diagnostic and prognostic information to myocardial perfusion imaging and has been shown to alter management. Whenever feasible, coronary calcium assessment should be performed routinely in patients without known coronary artery disease at the time of myocardial perfusion imaging.

The additive prognostic value of coronary calcium score (CCS) to single photon emission computed tomography myocardial perfusion imaging (SPECT-MPI)-real world data from a single center

AIMS

Single-photon emission computed tomography myocardial perfusion imaging [SPECT-MPI] is a functional test for coronary ischemia. We aimed to assess the additive prognostic value of coronary calcium score (CCS) to SPECT-MPI in stable patients.

METHODS

This study is a retrospective analysis of 655 patients who underwent SPECT-MPI with CCS (2012 to 2017). Receiver operator characteristic (ROC) identified CCS cutoff value for all-cause mortality: CCS+ if > cutoff value and MPI+ if ≥ 5% total perfusion defect (TPD). Patients were divided into 1 MPI-/CCS-; 2 MPI+/CCS-; 3 MPI-/CCS+; 4 MPI+/CCS+ and compared. Cox proportional hazard analysis identified predictors of mortality.

RESULTS

CCS cutoff for all-cause mortality was > 216 (C statistic 0.756, P < 0.0001). In MPI+ groups, mean TPD was similar (13.4% and 13.1% respectively) but mortality was higher in the CCS+ (12.5% vs. 4.8%, P = 0.22) as was the severe LV systolic dysfunction (8.0% vs. 0%, P = 0.095). In MPI- groups, mean TPD was similar (0.7% and 0.9% respectively) but all-cause mortality was higher in the CCS+ (10.7% vs. 1.6%, P < 0.0001) as was severe LVSD (2.9 % vs. 0.3% P = 0.016). Age, smoking, renal impairment ,and CCS > 216 were independent predictors of mortality.

CONCLUSIONS

Patients with raised CCS on SPECT-MPI have increased mortality and poor LV function despite a negative MPI.

High prevalence of sternal foramina in indigenous Bolivians compared to Midwest Americans and indigenous North Americans (sternal foramina in indigenous Bolivians)

The sternal foramen, usually an asymptomatic osteological defect, can lead to catastrophic consequences if not recognized prior to certain medical procedures. This study reports the prevalence of a sternal foramen in two South Amerindian populations compared with other published populations. We evaluated the presence of sternal foramina using thoracic computed tomography scans of 1334 (48% female) participants from two indigenous populations of Bolivia (n = 900 Tsimane, 434 Moseten). The prevalence of sternal foramina was compared to two U.S. populations of similar sex/age distribution (n = 572 Midwest Americans, 131 self-identified Native North Americans) via similar CT scans. A sternal foramen was significantly more common in the two Bolivian populations (prevalence ranging from 12.8 to 13.4%), compared to 4.4-5.1% in the two U.S. groups, consistent with prior estimates in studies from industrialized populations. Males had higher frequency of a sternal foramen compared to females in each of the four groups (OR = 1.904, 95% CI: 1.418-2.568, p < 0.001). Age was not associated with sternal foramen presence. These data show both a higher rate of sternal foramina in the South Amerindian populations versus comparator populations in North America and the highest rate of any studied living population. Although it is not possible to determine from our data the relative contribution of genetics versus early life or environmental causes to the higher rates of sternal foramen, we note that small prior studies have likewise demonstrated a higher prevalence in lower income countries. Further determination of the contributing factors warrants greater investigation and research.

Incremental prognostic value of visually estimated coronary artery calcium in patients undergoing positron emission tomography imaging

Objective

Visually estimated coronary artery calcium (VECAC) from chest CT or attenuation correction (AC)/CT obtained during positron emission tomography (PET)–myocardial perfusion imaging (MPI) is feasible. Our aim was to determine the prognostic value of VECAC beyond conventional risk factors and PET imaging parameters, including coronary flow reserve (CFR).

Methods

We analysed 608 patients without known coronary artery disease who underwent PET–MPI between 2012 and 2016 and had AC/CT and/or chest CT images. We used Cox regression to estimate the association of VECAC categories (≤10, 11–400, >400 Agatston units (AU)) with the primary outcome of all-cause death, acute coronary syndrome or stroke (mean follow-up 4.3±1.8 years). C-statistics assessed the relationship between PET parameters and VECAC with the primary outcome.

Results

Mean age was 58±11 years, 65% were women and 67% were black. VECAC ≤10, 11–400 and >400 AU was observed in 68%, 12% and 20% of subjects, respectively. Compared with VECAC ≤10, VECAC categories 11–400 (HR 2.25, 95% CI 1.24 to 4.08) and >400 AU (HR 3.05, 95% CI 1.87 to 4.98) were associated with the primary outcome after adjusting for traditional risk factors, MPI findings and CFR. Adding VECAC to a model that included PET–MPI, CFR and clinical risk factors improved the prognostic value for the primary outcomes (c-statistic 0.71 to 0.75 with VECAC, p=0.01).

Conclusions

VECAC is a potent predictor of events beyond traditional risk factors and PET imaging markers, including CFR. These data further support the importance for routine VECAC implementation.

Effect of Elevated Calcium Score on Normal Myocardial Perfusion Study on Clinician Management of Coronary Artery Disease Risk Factors

Elevated coronary artery calcification (CAC) scores are associated with higher cardiovascular (CV) risk even with normal stress myocardial perfusion imaging (MPI). Whether referring providers appropriately manage subclinical CV disease is unclear. We hypothesized that ordering clinicians would intensify medical therapy for CV disease in response to normal MPI and CAC ≥ 300. We conducted a cohort study on patients without known CV disease who underwent MPI and CAC scoring. Medical management of CV disease and clinical outcomes were assessed. Of 299 patients who underwent stress MPI, 62 patients had normal MPI and CAC ≥ 300. Documentation of elevated CAC score was noted in the final interpretation for 52% (n = 32) of MPI reports. During follow-up, treatment change in aspirin, cholesterol medications, and/or antihypertensive medication was made in 40% of these patients. Aspirin use increased from 71% to 82% (P < 0.001); statin use increased from 68% to 76% (P < 0.001). Several patients remained on suboptimal lipid or antiplatelet regimens without documented contraindication. Among patients with normal MPI, many have CAC ≥ 300. Not all MPI reports adequately call attention to this finding associated with elevated CV risk. Despite the elevated CAC score, some patients were not optimized medically.

Automated calcium scores collected during myocardial perfusion imaging improve identification of obstructive coronary artery disease

Background

Myocardial perfusion imaging (MPI) is an accurate noninvasive test for patients with suspected obstructive coronary artery disease (CAD) and coronary artery calcium (CAC) score is known to be a powerful predictor of cardiovascular events. Collection of CAC scores simultaneously with MPI is unexplored.

Aim

We aimed to investigate whether automatically derived CAC scores during myocardial perfusion imaging would further improve the diagnostic accuracy of MPI to detect obstructive CAD.

Methods

We analyzed 150 consecutive patients without a history of coronary revascularization with suspected obstructive CAD who were referred for 82Rb PET/CT and available coronary angiographic data. Myocardial perfusion was evaluated both semi quantitatively as well as quantitatively according to the European guidelines. CAC scores were automatically derived from the low-dose attenuation correction CT scans using previously developed software based on deep learning. Obstructive CAD was defined as stenosis >70% (or >50% in the left main coronary artery) and/or fractional flow reserve (FFR) ≤0.80.

Results

In total 58% of patients had obstructive CAD of which seventy-four percent were male. Addition of CAC scores to MPI and clinical predictors significantly improved the diagnostic accuracy of MPI to detect obstructive CAD. The area under the curve (AUC) increased from 0.87 to 0.91 (p: 0.025). Sensitivity and specificity analysis showed an incremental decrease in false negative tests with our MPI + CAC approach (n = 14 to n = 4), as a consequence an increase in false positive tests was seen (n = 11 to n = 28).

Conclusion

CAC scores collected simultaneously with MPI improve the detection of obstructive coronary artery disease in patients without a history of coronary revascularization.

Coronary calcium score influences referral for invasive coronary angiography after normal myocardial perfusion SPECT

BACKGROUND

In patients with normal SPECT but persistent complaints, invasive angiography may exclude obstructive coronary disease. We assessed whether high coronary artery calcium (CAC) scores are associated with increased referral for invasive angiography following normal SPECT.

METHODS AND RESULTS

2286 consecutive patients (mean age 60 ± 12, 39% male) with normal SPECT were assessed. All patients underwent simultaneous CAC scoring. Patients were categorized into four groups based on their CAC score: CAC = 0 (n = 694), CAC 1 to 100 (n = 891), CAC 101 to 400 (n = 368), and CAC >400 (n = 333). The decision to perform angiography was left to the discretion of treating physician. Follow-up angiography was confined to the first 60 days after SPECT. Occurrence of MACE (late revascularization, myocardial infarction or death) was recorded. Overall, 100 patients (4.4%) underwent early angiography with increasing rates in higher CAC score groups (1.0%, 2.6%, 8.4%, and 11.7%), respectively, P < .001). A CAC score >400 (OR 3.56, 95% CI 2.19 to 5.77, P < .001) was independently associated with referral to angiography. Similarly, CAC score >400 was an independent predictor for MACE (HR 9.26, 95% CI 5.06 to 16.93). Early angiography did not influence prognosis (HR 1.57, 95% CI 0.91 to 2.73).

CONCLUSIONS

CAC scoring impacts clinical decision-making and increases referral rates for invasive angiography after normal SPECT.

Is coronary calcium scoring too late? Total body arterial calcium burden in patients without known CAD and normal MPI

BACKGROUND

Patients with normal myocardial perfusion imaging (MPI) have a good prognosis. However, pre-clinical coronary and extracoronary atherosclerosis may exist in the absence of myocardial ischemia.

METHODS

154 Egyptian patients (mean age 53 years) underwent whole-body non-contrast CT following normal MPI.

RESULTS

Atherosclerosis in the form of calcification was observed in ≥1 vascular bed in 115 of 154 (75%) patients. This included the iliofemoral (62%), abdominal aorta (53%), thoracic aorta (47%), coronary (47%), and carotid (25%) vascular beds. Mean total body calcium score was 3172 ± 530 AU. Extracoronary atherosclerosis in patients with a zero coronary artery calcium (CAC) score was common, occurring in the above-listed beds 42%, 36%, 29%, and 7% of the time, respectively. CAC was rarely present without iliofemoral or abdominal aortic calcification.

CONCLUSION

Quantitative assessment of calcification in different vascular beds demonstrates that extracoronary atherosclerosis is common in patients who have normal MPI. Atherosclerotic calcifications are most common in the iliofemoral arteries and abdominal aorta, which typically predate coronary calcifications. An imaging strategy to detect extracoronary atherosclerosis could lead to greater understanding of the natural history of atherosclerosis in its long pre-clinical phase and possibly to earlier preventive strategies.

Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study

BACKGROUND

Conventional coronary artery disease risk factors might potentially explain at least 90% of the attributable risk of coronary artery disease. To better understand the association between the pre-industrial lifestyle and low prevalence of coronary artery disease risk factors, we examined the Tsimane, a Bolivian population living a subsistence lifestyle of hunting, gathering, fishing, and farming with few cardiovascular risk factors, but high infectious inflammatory burden.

METHODS

We did a cross-sectional cohort study including all individuals who self-identified as Tsimane and who were aged 40 years or older. Coronary atherosclerosis was assessed by coronary artery calcium (CAC) scoring done with non-contrast CT in Tsimane adults. We assessed the difference between the Tsimane and 6814 participants from the Multi-Ethnic Study of Atherosclerosis (MESA). CAC scores higher than 100 were considered representative of significant atherosclerotic disease. Tsimane blood lipid and inflammatory biomarkers were obtained at the time of scanning, and in some patients, longitudinally.

FINDINGS

Between July 2, 2014, and Sept 10, 2015, 705 individuals, who had data available for analysis, were included in this study. 596 (85%) of 705 Tsimane had no CAC, 89 (13%) had CAC scores of 1-100, and 20 (3%) had CAC scores higher than 100. For individuals older than age 75 years, 31 (65%) Tsimane presented with a CAC score of 0, and only four (8%) had CAC scores of 100 or more, a five-fold lower prevalence than industrialised populations (p≤0·0001 for all age categories of MESA). Mean LDL and HDL cholesterol concentrations were 2·35 mmol/L (91 mg/dL) and 1·0 mmol/L (39·5 mg/dL), respectively; obesity, hypertension, high blood sugar, and regular cigarette smoking were rare. High-sensitivity C-reactive protein was elevated beyond the clinical cutoff of 3·0 mg/dL in 360 (51%) Tsimane participants.

INTERPRETATION

Despite a high infectious inflammatory burden, the Tsimane, a forager-horticulturalist population of the Bolivian Amazon with few coronary artery disease risk factors, have the lowest reported levels of coronary artery disease of any population recorded to date. These findings suggest that coronary atherosclerosis can be avoided in most people by achieving a lifetime with very low LDL, low blood pressure, low glucose, normal body-mass index, no smoking, and plenty of physical activity. The relative contributions of each are still to be determined.

FUNDING

National Institute on Aging, National Institutes of Health; St Luke's Hospital of Kansas City; and Paleocardiology Foundation.

Changes in cardiovascular medication after coronary artery calcium scanning and normal single photon emission computed tomography myocardial perfusion imaging in symptomatic patients

The impact of coronary artery calcium (CAC) scoring on subsequent changes in cardiovascular medication use in symptomatic patients with normal myocardial perfusion imaging (MPI) findings is not well established. The aim of the current study was to evaluate changes in aspirin and statin use in patients suspected for coronary artery disease after CAC scoring and normal single photon emission computed tomography (SPECT) MPI.

METHODS

In the current study, 1,033 stable symptomatic patients without a known history of coronary artery disease with normal SPECT MPI who underwent concomitant CAC scoring were included. All patients had a clinical indication for imaging, mainly atypical chest pain and dyspnea, and were referred from the outpatient clinic of our hospital. Data regarding posttest medication change (either starting or discontinuation of aspirin and statin therapy at the subsequent outpatient visit) were retrospectively collected. Patients were categorized into 4 groups based on their CAC score.

RESULTS

Mean age of the patients was 61±11 years and 39% were male. At baseline, 35% of the patients used aspirin and 39% used statin. In patients with CAC scores 0, 1-99, 100-399, and ≥400, aspirin was started in 1%, 4%, 9%, and 9%, respectively, and statin was started in 0%, 7%, 18%, and 24% of the patients, respectively (P<.001). Aspirin was discontinued in 19%, 11%, 7%, and 1% and statin was discontinued in 8%, 6%, 2%, and 0% (P<.001) of the patients in these respective CAC score categories. After correction for differences in risk factors and baseline medication use, increased CAC was independently associated with posttest aspirin (odds ratio 4.6, 11.2, and 27.1 for CAC scores 1-99, 100-399, and ≥400, respectively; P<.001) and statin use (odds ratio 4.4, 19.4, and 60.9 for CAC scores 1-99, 100-399, and ≥400, respectively; P<.001).

CONCLUSIONS

Higher CAC scores are associated with the initiation of aspirin and statin therapy in patients with normal SPECT MPI. In patients with lower CAC scores, discontinuation of cardioprotective medication is more likely. CAC score is independently associated with posttest statin and aspirin use.

Value of Exercise ECG for Risk Stratification in Suspected or Known CAD in the Era of Advanced Imaging Technologies

Exercise stress electrocardiography (ExECG) is underutilized as the initial test modality in patients with interpretable electrocardiograms who are able to exercise. Although stress myocardial imaging techniques provide valuable diagnostic and prognostic information, variables derived from ExECG can yield substantial data for risk stratification, either supplementary to imaging variables or without concurrent imaging. In addition to exercise-induced ischemic ST-segment depression, such markers as ST-segment elevation in lead aVR, abnormal heart rate recovery post-exercise, failure to achieve target heart rate, and poor exercise capacity improve risk stratification of ExECG. For example, patients achieving ≥10 metabolic equivalents on ExECG have a very low prevalence of inducible ischemia and an excellent prognosis. In contrast, cardiac imaging techniques add diagnostic and prognostic value in higher-risk populations (e.g., poor functional capacity, diabetes, or chronic kidney disease). Optimal test selection for symptomatic patients with suspected coronary artery disease requires a patient-centered approach factoring in the risk/benefit ratio and cost-effectiveness.

Relationship between Calcium Score and Myocardial Scintigraphy in the Diagnosis of Coronary Disease

Half the patients with coronary artery disease present with sudden death - or acute infarction as first symptom, making early diagnosis pivotal. Myocardial perfusion scintigraphy is frequently used in the assessment of these patients, but it does not detect the disease without flow restriction, exposes the patient to high levels of radiation and is costly. On the other hand, with less radiological exposure, calcium score is directly correlated to the presence and extension of coronary atherosclerosis, and also to the risk of cardiovascular events. Even though calcium score is a tried-and-true method for stratification of asymptomatic patients, its use is still reduced in this context, since current guidelines are contradictory to its use on symptomatic diseases. The aim of this review is to identify, on patients under investigation for coronary artery disease, the main evidence of the use of calcium score associated with functional evaluation and scintigraphy.

SPECT Myocardial Blood Flow Quantitation Concludes Equivocal Myocardial Perfusion SPECT Studies to Increase Diagnostic Benefits

Recently, myocardial blood flow quantitation with dynamic SPECT/CT has been reported to enhance the detection of coronary artery disease in human. This advance has created important clinical applications to coronary artery disease diagnosis and management for areas where myocardial perfusion PET tracers are not available. We present 2 clinical cases that undergone a combined test of 1-day rest/dipyridamole-stress dynamic SPECT and ECG-gated myocardial perfusion SPECT scans using an integrated imaging protocol and demonstrate that flow parameters are capable to conclude equivocal myocardial perfusion SPECT studies, therefore increasing diagnostic benefits to add value in making clinical decisions.

The influence of coronary calcium score on the interpretation of myocardial perfusion imaging

PURPOSE

Coronary artery calcium (CAC) scores influence the pre-test likelihood of ischemia in patients undergoing myocardial perfusion imaging (MPI). We investigated the influence of CAC score knowledge on the visual interpretation of MPI in patients referred for the diagnostic work-up of suspected coronary artery disease.

METHODS

We retrospectively analyzed symptomatic patients who were referred for MPI. For the current analysis, we selected 151 patients who underwent SPECT MPI with simultaneous CAC scoring. MPI was visually interpreted in two separate sessions, first without and then with knowledge of the CAC score. MPI results were classified into four groups: normal, fixed defects, ischemia, and equivocal.

RESULTS

Mean age of the patients was 64 ± 11 years, 56% were male. Without knowledge of the CAC score MPI was evaluated as normal in 36%, compared to 40% with knowledge of the CAC score (P = 0.636). Overall, the addition of the CAC score changed the interpretation of MPI in 56 patients (37%). Importantly, the frequency of equivocal MPI interpretations decreased from 21% without knowledge of CAC score to 9% with knowledge of CAC score (P = 0.002).

CONCLUSIONS

Knowledge of the CAC score has a major impact on the interpretation of MPI, increasing the interpretative certainty.

Influence of iterative image reconstruction on CT-based calcium score measurements

Iterative reconstruction techniques for coronary CT angiography have been introduced as an alternative for traditional filter back projection (FBP) to reduce image noise, allowing improved image quality and a potential for dose reduction. However, the impact of iterative reconstruction on the coronary artery calcium score is not fully known. In 112 consecutive stable patients with suspected coronary artery disease, the coronary calcium scores were assessed. Comparisons were made between the Agatston, volume and mass scores obtained with traditional FBP, and by using adaptive statistical iterative reconstruction (ASIR). A significant reduction of the Agatston score, volume score and mass score was observed for ASIR when compared to FBP, with median differences of resp. 26, 5 mm(3) and 1 mg. Using the ASIR reconstruction, the number of patients with a calcium score of zero increased by 13 %. Iterative CT reconstruction significantly reduces the Agatston, volume and mass scores. Since the calcium score is used as a prognostic tool for coronary artery disease, caution must be taken when using iterative reconstruction.

Myocardial perfusion imaging in stable symptomatic patients with extensive coronary atherosclerosis

PURPOSE

High coronary artery calcium (CAC) scores are associated with a high likelihood of ischaemia and obstructive coronary disease. Myocardial perfusion imaging (MPI) is a key investigation to determine the need for revascularization. However, the value of MPI in presence of extensive CAC has so far only been demonstrated in asymptomatic patients, whereas its value in symptomatic patients remains largely unclear. Therefore, we studied the impact of MPI in symptomatic patients with a CAC score ≥ 1,000.

METHODS

We included 282 patients (mean age 69 ± 9 years, 63% men) without a history of coronary disease with suspected stable angina referred for MPI and with a CAC score ≥ 1,000. On follow-up at 18 months invasive angiography, coronary revascularization, nonfatal myocardial infarction and death were recorded.

RESULTS

MPI was normal in 54 %, equivocal in 10 % and abnormal in 37 % (fixed defect 9 % and ischaemia 28 %) of patients. More abnormal MPI findings were observed in men, smokers and those with even higher CAC scores. During follow-up, 1 patient (with nonischaemic MPI) died from a cardiac cause, 1 patient (with ischaemic MPI) suffered a myocardial infarction and 92 patients (33 %) underwent revascularization. Ischaemia on MPI was a strong predictor of coronary revascularization (odds ratio 13.1; 95 % CI 7.1-24.3; p < 0.001).

CONCLUSION

Ischaemia on MPI is observed in approximately 30 % of patients with a CAC score ≥ 1,000, and is a strong predictor of coronary revascularization. However, nonischaemic MPI does not exclude revascularization, and patients with persisting complaints should be considered for invasive angiography.

A head-to-head comparison of the coronary calcium score by computed tomography with myocardial perfusion imaging in predicting coronary artery disease

Objectives

The coronary artery calcium (CAC) score has been shown to predict future cardiac events. However the extent to which the added value of a CAC score to the diagnostic performance of myocardial perfusion imaging (MPI) by single photon emission computed tomography (SPECT) is unclear. The purpose of this study is to investigate the correlation between CAC score and SPECT in patients with suspected coronary artery disease.

Methods

A retrospective review of the CAC scores by use of the Agatston calcium scoring method and cardiac SPECT diagnostic reports was conducted in 48 patients, who underwent both coronary computed tomography (CT) and SPECT examinations due to suspected coronary artery disease. A Pearson correlation test was used to determine the relation between CAC scores and MPI-SPECT assessments with regard to the evaluation of the extent of disease.

Results

Forty-seven percent of the patients had CAC scores more than 100, while 42% of these patients demonstrated abnormal, or probably abnormal, MPI-SPECT. Of the 23% of patients with a zero CAC score, only 7% had normal MPI-SPECT findings. No significant correlation was found between the CAC scores and MPI-SPECT assessments (r value ranged from 0.012 to 0.080), regardless of the degree of coronary calcification.

Conclusions

There is a lack of correlation between the CAC scores and the MPI-SPECT findings in the assessment of the extent of coronary artery disease. CAC scores and MPI-SPECT should be considered complementary approaches in the evaluation of patients with suspected coronary artery disease.

Usefulness of coronary calcium scoring to myocardial perfusion SPECT in the diagnosis of coronary artery disease in a predominantly high risk population

Coronary calcium scoring (CCS) adds to the diagnostic performance of myocardial perfusion single-photon emission computed tomography (SPECT) to assess the presence of significant coronary artery disease (CAD). Patients with a high pre-test likelihood are expected to have a high CCS which potentially could enhance the diagnostic performance of myocardial perfusion SPECT in this specific patient group. We evaluated the added value of CCS to SPECT in the diagnosis of significant CAD in patients with an intermediate to high pre-test likelihood. In total, 129 patients (mean age 62.7 ± 9.7 years, 65 % male) with stable anginal complaints and intermediate to high pre-test likelihood of CAD (median 87 %, range 22-95) were prospectively included in this study. All patients received SPECT and CCS imaging preceding invasive coronary angiography (CA). Fractional flow reserve (FFR) measurements were acquired from patients with angiographically estimated 50-95 % obstructive CAD. For SPECT a SSS > 3 was defined significant CAD. For CCS the optimal cut-off value for significant CAD was determined by ROC curve analysis. The reference standard for significant CAD was a FFR of <0.80 acquired by CA. Significant CAD was demonstrated in 64 patients (49.6 %). Optimal CCS cut-off value for significant CAD was >182.5. ROC curve analysis for prediction of the presence of significant CAD for SPECT, CCS and the combination of CCS and SPECT resulted in an area under the curve (AUC) of 0.88 (95 % CI 81-94), 0.75 (95 % CI 66-83 %) and 0.92 (95 % CI 87-97 %) respectively. The difference of the AUC between SPECT and the combination of CCS and SPECT was 0.05 (P = 0.12). The addition of CCS did not significantly improve the diagnostic performance of SPECT in the evaluation of patients with a predominantly high pre-test likelihood of CAD.

Combination of myocardial perfusion imaging and coronary artery calcium scanning: potential synergies for improving risk assessment in subjects with suspected coronary artery disease

For many years, the mainstay of noninvasive evaluation of patients suspected of ischemic cardiovascular disease (CVD) centered on the use of myocardial perfusion imaging (MPI). In recent years, the advent of newer modalities such as coronary artery calcium (CAC) scanning, coronary CT angiography, and MRI have broadened the means of assessing cardiac patients for this purpose. Moreover, the advent of these newer modalities has created potential synergies whereby combinations of tests may be clinically useful. In this review, we assess the potential synergies between MPI, whether assessed by single photon emission computed tomography (SPECT) or positron emission tomography (PET), and CAC scanning. Whereas MPI has long been used for diagnostic assessment and for risk stratification purposes, the emerging uses of CAC scanning now appear multifold: screening for CVD, triaging patients for diagnostic stress testing, improving risk stratification in patients following stress testing, and enhancing the direct management of patients' CVD risk following CAC scanning. Recent work suggests that CAC scanning may be emerging as the initial test of choice for most asymptomatic patients. The advent of hybrid SPECT-CT and PET-CT scanners may signify an important new opportunity for the combined use of these modalities in the higher-risk asymptomatic patient population.

Agreement of visual estimation of coronary artery calcium from low-dose CT attenuation correction scans in hybrid PET/CT and SPECT/CT with standard Agatston score

OBJECTIVES

We sought to evaluate the accuracy and reproducibility of visual estimation of coronary artery calcium (CAC) from computed tomography attenuation correction (CTAC) scans performed for hybrid positron emission tomography (PET)/computed tomography (CT) and single-photon emission computed tomography (SPECT)/CT myocardial perfusion imaging (MPI).

BACKGROUND

At the time of MPI, hybrid systems obtain a low-dose, non-electrocardiogram (ECG)-gated CT scan that is used to perform attenuation correction. Utility of this CTAC scan in estimating actual CAC as measured by Agatston score (AS) on standard ECG-gated scans has not been previously studied.

METHODS

A total of 492 patients, from 3 centers, receiving both MPI with CTAC and a standard CAC scan were studied. At each site, experienced readers blinded to AS reviewed CTAC images, visually estimating CAC on a 6-level scale: classifying patients as estimated AS of 0, 1 to 9, 10 to 99, 100 to 300, 400 to 999, or ≥1,000. Agreement between visually estimated coronary artery calcium (VECAC) on CTAC and AS, measured standardly and converted to the same scale, was evaluated, as was inter-reader agreement.

RESULTS

Although CTAC images are low dose and nongated, a high degree of association was observed between VECAC and AS, with 63% of VECACs in the same category as the AS category and 93% within 1 category. Weighted kappa was 0.89 (95% confidence interval: 0.88 to 0.91, p < 0.0001). High weighted kappa statistics were observed for each site, scanner type, and sex. Readers reported identical scores in 65% of cases and scores within 1 category in 93%.

CONCLUSIONS

CAC can be visually assessed from low-dose CTAC scans with high agreement with AS. CTAC scans should be routinely assessed for VECAC.

Clinical Role of Hybrid Imaging

Recent technological advances have fueled the growth in hybrid radionuclide and CT imaging of the heart. Noninvasive imaging studies are reliable means to diagnose coronary artery disease (CAD), stratify risk, and guide clinical management. Myocardial perfusion scintigraphy is a robust, widely available noninvasive modality for the evaluation of ischemia from known or suspected CAD. Cardiac CT (coronary artery calcium score and coronary CT angiography) has emerged as a clinically robust noninvasive anatomic imaging test, capable of rapidly diagnosing or excluding obstructive CAD. Both anatomic and functional modalities have strengths and weaknesses, and can complement each other by offering integrated structural and physiologic information. As we discuss below, in selected patients, hybrid imaging may facilitate more accurate diagnosis, risk stratification, and management in a "one-stop shop" setting.

Diagnostic and clinical benefit of combined coronary calcium and perfusion assessment in patients undergoing PET/CT myocardial perfusion stress imaging

BACKGROUND

A limitation of stress myocardial perfusion imaging (MPI) is the inability to detect non-obstructive coronary artery disease (CAD). One advantage of MPI with a hybrid CT device is the ability to obtain same-setting measurement of the coronary artery calcium score (CACS).

METHODS AND RESULTS

Utilizing our single-center nuclear database, we identified 760 consecutive patients with: (1) no CAD history; (2) a normal clinically indicated Rb-82 PET/CT stress perfusion study; and (3) a same-setting CAC scan. 487 of 760 patients (64.1%) had subclinical CAD based on an abnormal CACS. Of those with CAC, the CACS was > or =100, > or =400, and > or =1000 in 47.0%, 22.4%, and 8.4% of patients, respectively. Less than half of the patients with CAC were receiving aspirin or statin medications prior to PET/CT imaging. Patients with CAC were more likely to be initiated or optimized on proven medical therapy for CAD immediately following PET/CT MPI compared to those without CAC.

CONCLUSIONS

Subclinical CAD is common in patients without known CAD and normal myocardial perfusion assessed by hybrid PET/CT imaging. Identification of CAC influences subsequent physician prescribing patterns such that those with CAC are more likely to be treated with proven medical therapy for the treatment of CAD.

Integration of coronary anatomy and myocardial perfusion imaging

Advances in cardiovascular imaging have resulted in the development of multiple noninvasive techniques to evaluate myocardial perfusion and coronary anatomy, each of which has unique strengths and limitations. For example, CT angiography can directly visualize the presence of atherosclerosis, but the hemodynamic effect of many lesions identified by this technique is unknown. Alternatively, myocardial perfusion imaging enables a physiological assessment, but it may underestimate the extent of atherosclerosis in patients with multivessel disease. Dual-modality simultaneous imaging or multimodal sequential imaging techniques facilitate integration of information on both myocardial perfusion and coronary anatomy, and thus have the potential to improve diagnostic and prognostic evaluation, which could translate into improved care of patients. This Review discusses the strengths and limitations of the currently available individual noninvasive techniques for imaging coronary anatomy and myocardial perfusion. Approaches to integration of these imaging modalities are described, followed by an exploration of the clinical utility and future directions of hybrid imaging.

The coronary artery calcium score and stress myocardial perfusion imaging provide independent and complementary prediction of cardiac risk

OBJECTIVES

This study sought to examine the relationship between coronary artery calcium score (CACS) and single-photon emission computed tomography (SPECT) results for predicting the short- and long-term risk of cardiac events.

BACKGROUND

The CACS and SPECT results both provide important prognostic information. It is unclear whether integrating these tests will better predict patient outcome.

METHODS

We followed-up 1,126 generally asymptomatic subjects without previous cardiovascular disease who had a CACS and stress SPECT scan performed within a close time period (median 56 days). The median follow-up was 6.9 years. End points analyzed were total cardiac events and all-cause death/myocardial infarction (MI).

RESULTS

An abnormal SPECT result increased with increasing CACS from <1% (CACS < or =10) to 29% (CACS >400) (p < 0.001). Total cardiac events and death/MI also increased with increasing CACS and abnormal SPECT results (p < 0.001). In subjects with a normal SPECT result, CACS added incremental prognostic information, with a 3.55-fold relative increase for any cardiac event (2.75-fold for death/MI) when the CACS was severe (>400) versus minimal (< or =10). Separation of the survival curves occurred at 3 years after initial testing for all cardiac events and at 5 years for death/MI.

CONCLUSIONS

The CACS and SPECT findings are independent and complementary predictors of short- and long-term cardiac events. Despite a normal SPECT result, a severe CACS identifies subjects at high long-term cardiac risk. After a normal SPECT result, our findings support performing a CACS in patients who are at intermediate or high clinical risk for coronary artery disease to better define those who will have a high long-term risk for adverse cardiac events.

Coronary calcium scanning in geriatric cardiology

Coronary artery disease (CAD) is prevalent in the elderly, often leads to disability, and is the number one cause of death in this population. Older adults represent an increasingly important and challenging subset of the population with CAD. They are more likely to have comorbid conditions, atypical presentations, and unfavorable outcomes than their younger counterparts. The available data suggest that standard pharmacologic, thrombolytic, and definitive revascularization techniques have important roles in the treatment of geriatric patients but have been underutilized. Consequently, strategies for optimizing the prevention and treatment of CAD in the elderly are important from both the individual and societal perspectives. Coronary artery calcium has been shown to be highly specific for atherosclerosis, occurring only in the intima of the coronary arteries. There is evidence to show that elevated coronary calcium scores are predictive of future cardiovascular events, both independently of and incrementally to conventional cardiovascular risk factors. This article will review such a screening method, namely coronary calcium scanning, in the field of geriatric cardiology.

Combining myocardial perfusion imaging with computed tomography for diagnosis of coronary artery disease

PURPOSE OF REVIEW

To illustrate where the integration of computed tomography with myocardial perfusion single photon tomography may improve current diagnostic imaging paradigms and allow for enhanced risk stratification.

RECENT FINDINGS

Computed tomography has the advantage of detecting coronary atherosclerosis at its earliest stages and also identifying patients at high risk for having underlying myocardial ischemia, allowing initiation of appropriate therapeutic measures well before development of obstructive coronary artery disease. Single photon computed tomography can, conversely, clarify the anatomic findings of computed tomography, based on a functional assessment of myocardial blood flow, thereby guiding antiischemic and interventional therapies.

SUMMARY

Hybrid imaging with single photon tomography and computed tomography angiography may prove important from a diagnostic and therapeutic viewpoint in several clinical scenarios. It is likely that fusion imaging may more precisely tailor therapy, reduce healthcare costs and improve patient outcome over the next decade.

Hybrid SPECT-CT: Integration of CT coronary artery calcium scoring and angiography with myocardial perfusion

A natural extension of current imaging paradigms for diagnosing coronary artery disease may well be the integration of CT with myocardial perfusion single-photon CT (SPECT). Although there is a wealth of clinical information regarding the utility of SPECT, the value of CT in the cardiology arena has only recently been explored. CT has the advantage of detecting coronary atherosclerosis at its earliest stages, allowing initiation of appropriate therapeutic measures well before development of obstructive coronary artery disease. However, SPECT can clarify the anatomic findings of CT based on a functional assessment of myocardial blood flow, thereby guiding management decisions. Hybrid imaging with SPECT and CT angiography may prove important from a diagnostic and therapeutic view point in several clinical scenarios, and it is likely that over the next decade fusion imaging may more precisely tailor therapy, reduce healthcare costs, and improve patient outcome.

Coronary calcium scanning

While there is no doubt that high-risk patients (those with more than a 20% 10-year risk of a future cardiovascular event) need more aggressive preventive therapy, a majority of cardiovascular events occur in individuals at intermediate risk (10%-20% 10-year risk). Data suggest that it will be most cost-effective to concentrate screening efforts on this group of patients. Coronary artery calcium has been shown to be highly specific for atherosclerosis, occurring only in the intima of the coronary arteries. There is evidence to show that elevated coronary calcium scores are predictive of cardiovascular events, both independently of and incrementally to conventional cardiovascular risk factors. Based on current available data, patients with increased plaque burdens (increased coronary calcium scores) are approximately 10 times more likely to suffer a cardiac event over the next 3-5 years. Coronary calcium scores have outperformed conventional risk factors, high sensitivity C-reactive protein, and carotid intima-media thickness as a predictor of cardiovascular events. Both electron beam tomography and multidetector computed tomography can accurately detect and quantify the coronary calcium scores. In summary, coronary calcium detection significantly improves the accuracy of global cardiovascular risk prevention, the noninvasive tracking of the atherosclerotic burden, and the prediction of cardiovascular events.

Potential Indications for Coronary Angiography by Computed Tomography

Recent advances in computed tomography technology have made possible angiographic images of relatively small, moving vascular structures such as the coronary arteries. Computed tomographic coronary angiography is an exciting modality which has several obvious advantages over invasive catheterization, such as its relatively noninvasive nature and rapid speed of acquisition. However, significant drawbacks still exist, including limitations of spatial and temporal resolution and radiation exposure. Computed tomographic coronary angiography appears best suited as a diagnostic modality for the patient population with a low-to-moderate pretest probability of coronary artery disease, and for specific indications such as the imaging of coronary anomalies and bypass grafts and before biventricular pacemaker placement and atrial fibrillation ablation.