Combined evaluation of regional coronary artery calcium and myocardial perfusion by 82Rb PET/CT in predicting lesion-related outcome

The prognostic value of visual and automatic coronary calcium scoring from low-dose computed tomography-[15O]-water positron emission tomography

AIMS

The study aimed, firstly, to validate automatically and visually scored coronary artery calcium (CAC) on low-dose computed tomography (CT) (LDCT) scans with a dedicated calcium scoring CT (CSCT) scan and, secondly, to assess the added value of CAC scored from LDCT scans acquired during [15O]-water-positron emission tomography (PET) myocardial perfusion imaging (MPI) on prediction of major adverse cardiac events (MACE).

METHODS AND RESULTS

Five hundred seventy-two consecutive patients with suspected coronary artery disease, who underwent [15O]-water-PET MPI with LDCT and a dedicated CSCT scan were included. In the reference CSCT scans, manual CAC scoring was performed, while LDCT scans were scored visually and automatically using deep learning approach. Subsequently, based on CAC score results from CSCT and LDCT scans, each patient's scan was assigned to one out of five cardiovascular risk groups (0, 1-100, 101-400, 401-1000, >1000), and the agreement in risk group classification between CSCT and LDCT scans was investigated. MACE was defined as a composite of all-cause death, non-fatal myocardial infarction, coronary revascularization, and unstable angina. The agreement in risk group classification between reference CSCT manual scoring and visual/automatic LDCT scoring from LDCT was 0.66 [95% confidence interval (CI): 0.62-0.70] and 0.58 (95% CI: 0.53-0.62), respectively. Based on visual and automatic CAC scoring from LDCT scans, patients with CAC > 100 and CAC > 400, respectively, were at increased risk of MACE, independently of ischaemic information from the [15O]-water-PET scan.

CONCLUSION

There is a moderate agreement in risk classification between visual and automatic CAC scoring from LDCT and reference CSCT scans. Visual and automatic CAC scoring from LDCT scans improve identification of patients at higher risk of MACE.

Impact on cardiovascular outcome of coronary revascularization-induced changes in ischemic perfusion defect and myocardial flow reserve

PURPOSE

We evaluated the impact on cardiovascular outcome of coronary revascularization-induced changes in ischemic total perfusion defect (ITPD) and myocardial flow reserve (MFR) as assessed by 82Rb positron emission tomography (PET)/computed tomography (CT) imaging.

METHODS

The study included 102 patients referred to 82Rb PET/CT myocardial perfusion imaging before and after coronary revascularization. All patients were followed for the occurrence of cardiovascular events (cardiac death, nonfatal myocardial infarction, repeated revascularization, and heart failure) after the second imaging study.

RESULTS

During a median follow-up of 20 months, 21 events occurred. The clinical characteristics were comparable between patients with and without events. In the overall study population, after revascularization, there was a significant reduction (P < 0.001) of ITPD, while hyperemic myocardial blood flow (MBF) (P < 0.01) and MFR (P < 0.05) significantly improved. Event rate was higher in patients with ITPD (P < 0.005) or MFR (P < 0.001) worsening compared to those with unchanged or improved ITPD or MFR. At Cox univariable analysis, ITPD and MFR worsening resulted in predictors of events (both P < 0.05). Patients with worsening of both ITPD and MFR had the worst event-free survival (log-rank 32.9, P for trend < 0.001).

CONCLUSIONS

In patients with stable CAD, worsening of ITPD and MFR after revascularization procedures is associated with higher risk of cardiovascular events. Follow-up MPI with 82Rb PET/CT may improve risk stratification in patients submitted to coronary revascularization.

Comparing various AI approaches to traditional quantitative assessment of the myocardial perfusion in [82Rb] PET for MACE prediction

Assessing the individual risk of Major Adverse Cardiac Events (MACE) is of major importance as cardiovascular diseases remain the leading cause of death worldwide. Quantitative Myocardial Perfusion Imaging (MPI) parameters such as stress Myocardial Blood Flow (sMBF) or Myocardial Flow Reserve (MFR) constitutes the gold standard for prognosis assessment. We propose a systematic investigation of the value of Artificial Intelligence (AI) to leverage [82 Rb] Silicon PhotoMultiplier (SiPM) PET MPI for MACE prediction. We establish a general pipeline for AI model validation to assess and compare the performance of global (i.e. average of the entire MPI signal), regional (17 segments), radiomics and Convolutional Neural Network (CNN) models leveraging various MPI signals on a dataset of 234 patients. Results showed that all regional AI models significantly outperformed the global model ( p < 0.001 ), where the best AUC of 73.9% (CI 72.5-75.3) was obtained with a CNN model. A regional AI model based on MBF averages from 17 segments fed to a Logistic Regression (LR) constituted an excellent trade-off between model simplicity and performance, achieving an AUC of 73.4% (CI 72.3-74.7). A radiomics model based on intensity features revealed that the global average was the least important feature when compared to other aggregations of the MPI signal over the myocardium. We conclude that AI models can allow better personalized prognosis assessment for MACE.

Combined evaluation of CAC score and myocardial perfusion imaging in patients at risk of cardiovascular disease: where are we and what do the data say

Advances in the prevention and treatment of cardiovascular disease (CVD) over the last decades have led to a marked reduction in mortality for CVD. Nevertheless, atherosclerosis leading to coronary artery disease and stroke remains one of the most common causes of death in the world. The usefulness of imaging tests in the early identification of disease led to identify subjects at major risk of poor outcomes, suggesting risk factor modification. The aim of this article is to analyze the state of art of combined imaging in patients at risk of CVD referred to MPI evaluation, to highlight the present and potential features able to provide incremental prognostic information to help clinicians in patient management and to reduce adverse events.

Comparison of the prognostic value of impaired stress myocardial blood flow, myocardial flow reserve, and myocardial flow capacity on low-dose Rubidium-82 SiPM PET/CT

BACKGROUND

The most reliable quantitative variable on Rubidium-82 (82Rb) cardiac PET/CT for predicting major adverse cardiovascular events (MACE) has not been characterized with low-dose silicon photomultipliers (SiPM) technology, which allows halving injected activity and radiation dose delivering less than 1.0 mSv in a 70-kg individual.

METHODS AND RESULTS

We prospectively enrolled 234 consecutive participants with suspected myocardial ischemia. Participants underwent 82Rb cardiac SiPM PET/CT (5 MBq/kg) and were followed up for MACE over 652 days (interquartile range 559-751 days). For each participant, global stress myocardial blood flow (stress MBF), global myocardial flow reserve (MFR), and regional severely reduced myocardial flow capacity (MFCsevere) were measured. The Youden index was used to select optimal thresholds. In multivariate analysis after adjustments for clinical risk factors, reduced global stress MBF < 1.94 ml/min/g, reduced global MFR < 1.98, and regional MFCsevere > 3.2% of left ventricle emerged all as independent predictors of MACE (HR 4.5, 3.1, and 3.67, respectively, p < 0.001). However, only reduced global stress MBF remained an independent prognostic factor for MACE after adjusting for clinical risk factors and the combined use of global stress MBF, global MFR, and regional MFCsevere impairments (HR 2.81, p = 0.027).

CONCLUSION

Using the latest SiPM PET technology with low-dose 82Rb halving the standard activity to deliver < 1 mSv for a 70-kg patient, impaired global stress MBF, global MFR, and regional MFC were powerful predictors of cardiovascular events, outperforming traditional cardiovascular risk factors. However, only reduced global stress MBF independently predicted MACE, being superior to global MFR and regional MFC impairments.

Prediction of outcome by 82Rb PET/CT in patients with ischemia and nonobstructive coronary arteries

BACKGROUND

The purpose of this study was to assess the prognostic value of cardiac 82Rb positron emission tomography (PET)/computed tomography (CT) imaging in patients with myocardial ischemia of nonobstructive coronary arteries (INOCA).

METHODS

We retrospectively evaluated 311 INOCA patients who underwent rest stress 82Rb PET/CT. Cardiac end points were cardiac death, myocardial infarction, or late coronary revascularization. A parametric survival model was also used to identify how the variables influenced time to event.

RESULTS

During a median follow-up of 37 months (range 6-108), 23 (7%) cardiac events occurred. In patients with events total perfusion defect (TPD) was higher and myocardial flow reserve (MFR) lower compared to those without events (both P < .001). At multivariable Cox analysis, increased TPD (i.e., ≥ 5%) and reduced MFR (i.e., < 2) were predictors of events (both P < .001). At Weibull survival analysis, the highest probability of cardiac events and risk acceleration were observed in patients with both increased TPD and reduced MFR. Annualized event rate was higher in patients with reduced MFR compared to those with preserved MFR (P < .001).

CONCLUSION

In patients with INOCA, the combined evaluation of myocardial perfusion and coronary vascular function by 82Rb PET/CT is able to identify those at higher risk of cardiac events.

Computed tomography and nuclear medicine for the assessment of coronary inflammation: clinical applications and perspectives

There is increasing evidence that in patients with atherosclerotic cardiovascular disease (ASCVD) under optimal medical therapy, a persisting dysregulation of the lipid and glucose metabolism, associated with adipose tissue dysfunction and inflammation, predicts a substantial residual risk of disease progression and cardiovascular events. Despite the inflammatory nature of ASCVD, circulating biomarkers such as high-sensitivity C-reactive protein and interleukins may lack specificity for vascular inflammation. As known, dysfunctional epicardial adipose tissue (EAT) and pericoronary adipose tissue (PCAT) produce pro-inflammatory mediators and promote cellular tissue infiltration triggering further pro-inflammatory mechanisms. The consequent tissue modifications determine the attenuation of PCAT as assessed and measured by coronary computed tomography angiography (CCTA). Recently, relevant studies have demonstrated a correlation between EAT and PCAT and obstructive coronary artery disease, inflammatory plaque status and coronary flow reserve (CFR). In parallel, CFR is well recognized as a marker of coronary vasomotor function that incorporates the haemodynamic effects of epicardial, diffuse and small-vessel disease on myocardial tissue perfusion. An inverse relationship between EAT volume and coronary vascular function and the association of PCAT attenuation and impaired CFR have already been reported. Moreover, many studies demonstrated that 18F-FDG PET is able to detect PCAT inflammation in patients with coronary atherosclerosis. Importantly, the perivascular FAI (fat attenuation index) showed incremental value for the prediction of adverse clinical events beyond traditional risk factors and CCTA indices by providing a quantitative measure of coronary inflammation. As an indicator of increased cardiac mortality, it could guide early targeted primary prevention in a wide spectrum of patients. In this review, we summarize the current evidence regarding the clinical applications and perspectives of EAT and PCAT assessment performed by CCTA and the prognostic information derived by nuclear medicine.

Radionuclide Tracers for Myocardial Perfusion Imaging and Blood Flow Quantification

Myocardial perfusion imaging by nuclear cardiology is widely validated for the diagnosis, risk stratification, and management of patients with suspected or known coronary artery disease. Numerous radiopharmaceuticals are available for single-photon emission computed tomography and PET modalities. Each tracer shows advantages and limitations that should be taken into account in performing an imaging examination. This review aimed to summarize the state-of-the-art radiotracers used for myocardial perfusion imaging and blood flow quantification, highlighting the new technologic advances and promising possible applications.

Prognostic implications of myocardial perfusion imaging by 82-rubidium positron emission tomography in male and female patients with angina and no perfusion defects

AIMS

Myocardial perfusion imaging with 82-rubidium positron emission tomography (82Rb-PET) is increasingly used to assess stable coronary artery disease (CAD). We aimed to evaluate the prognostic value of 82Rb-PET-derived parameters in patients with symptoms suggestive of CAD but no significant reversible or irreversible perfusion defects.

METHODS AND RESULTS

Among 3726 consecutive patients suspected of stable CAD who underwent 82Rb-PET between January 2018 and August 2020, 2175 had no regional perfusion defects. Among these patients, we studied the association of 82Rb-PET-derived parameters with a composite endpoint of all-cause mortality, hospitalization for unstable angina pectoris, acute myocardial infarction, heart failure, or ischaemic stroke. During a median follow up of 1.7 years (interquartile range 1.1-2.5 years), there were 148 endpoints. Myocardial blood flow (MBF) reserve (MFR), MBF during stress, left ventricular ejection fraction (LVEF), LVEF-reserve, heart rate reserve, and Ca score were associated with adverse outcomes. In multivariable Cox model adjusted for patient and 82Rb-PET characteristics, MFR < 2 (hazard ratio (HR) 1.75, 95% confidence interval (CI) 1.24-2.48), LVEF (HR 1.38 per 10% decrease, 95% CI 1.24-1.54), and LVEF-reserve (HR 1.19 per 5% decrease, 95% CI 1.07-1.31) were significant predictors of endpoints. Results were consistent in subgroups defined by gender, history of ischaemic heart disease, low LVEF, and atrial fibrillation.

CONCLUSION

MFR, LVEF, and LVEF-reserve derived from 82Rb-PET provide prognostic information on cardiovascular outcomes in patients with no perfusion defects. This may aid in identifying patients at risk and might provide an opportunity for preventive interventions.

Incremental value of 18F-FDG cardiac PET imaging over dobutamine stress echocardiography in predicting myocardial ischemia in patients with suspected coronary artery disease

BACKGROUND

To assess the incremental value of 18F-fluorodeoxyglucose (FDG) cardiac positron emission tomography (PET) over dobutamine stress echocardiography (DSE) in predicting myocardial ischemia in patients with suspected coronary artery disease (CAD).

METHODS

Forty-one patients with suspected CAD underwent within 7 days apart rest-stress cardiac PET with 82Rb and DSE followed by cardiac 18F-FDG PET imaging. 18F-FDG images were scored on a 0 (no discernible uptake) to 2 (intense uptake) scale. Logistic regression analysis was performed to identify predictors of stress-induced ischemia. The incremental value of 18F-FDG PET over DSE in detecting ischemia at 82Rb PET cardiac imaging was assessed by the likelihood ratio chi-square and net reclassification index.

RESULTS

On 82Rb-PET imaging, myocardial ischemia (ischemic total perfusion defect ≥ 5%) was detected in 20 (49%) patients. Inducible ischemia was found in 22 (54%) patients on DSE (biphasic or worsening response pattern in ≥ 1 segment) and in 21 (51%) patients on 18F-FDG PET (uptake score of 2 in ≥ 1 segment). 18F-FDG PET resulted as statistically significant predictor of ischemia on 82Rb-PET. The addition of 18F-FDG PET to DSE increased the likelihood of ischemia on 82Rb-PET (P < .05). 18F-FDG PET was able to reclassify the probability of stress-induced myocardial ischemia on both patient and vessel analyses.

CONCLUSION

18F-FDG PET performed after dobutamine stress test may provide incremental value to DSE in the evaluation of myocardial ischemia. These results suggest that stress-induced myocardial ischemia can be imaged directly using 18F-FDG PET after dobutamine stress test.

Added value of coronary artery calcium score in the reporting of SPECT versus PET myocardial perfusion imaging

BACKGROUND

Knowledge of coronary artery calcium score (CACS) influences the interpretation of myocardial perfusion imaging (MPI) with SPECT; however, the impact on PET interpretation remains unclear. We compared the added value of CACS to reporting MPI using SPECT vs PET.

METHODS

We retrospectively included 412 patients. 206 patients who underwent Rb-82 PET were propensity-based matched to a cohort of 4018 patients who underwent cadmium-zinc-telluride SPECT MPI to obtain a comparable group of 206 SPECT patients. Next, we created four image sets: SPECT MPI-only, PET-only, SPECT + CACS, and PET + CACS. Two physicians interpreted the 824 images as normal, equivocal, or abnormal for ischemia or irreversible defects. Additionally, event rates were compared between PET and SPECT groups during 30-month follow-up.

RESULTS

PET yielded more scans interpreted as normal than SPECT (88% vs 80%, respectively, P = 0.015). Adding CACS to SPECT increased the percentage of normal scans to 86% (P = 0.014), whereas this effect was absent for PET (90%, P = 0.77). Annualized event rates for images interpreted as normal did not differ and varied between 0.7 and 2.0% (P > 0.084).

CONCLUSION

Adding CACS correctly increased the percentage of normal scans for SPECT MPI but not for PET, possibly limiting the effect of adding CACS to reporting PET.

Regional myocardial perfusion imaging in predicting vessel-related outcome: interplay between the perfusion results and angiographic findings

BACKGROUND

Despite myocardial perfusion imaging (MPI) by cadmium-zinc-telluride (CZT) single-photon emission computed tomography (SPECT) camera is largely used in the diagnosis and risk stratification of patients with suspected or known coronary artery disease (CAD), no data are available on the prognostic value of a regional MPI evaluation. We evaluated the prognostic value of regional MPI by the CZT camera in predicting clinical outcomes at the vessel level in patients with available angiographic data.

METHODS AND RESULTS

Five hundred and forty-one subjects with suspected or known CAD referred to 99mTc-sestamibi gated CZT-SPECT cardiac imaging and with available angiographic data were studied. Both regional total perfusion deficit (TPD) and ischemic TPD (ITPD) were calculated separately for each vascular territory (left anterior descending, left circumflex, and right coronary artery). The outcome end points were cardiac death, target vessel-related myocardial infarction, or late coronary revascularization. The prevalence of CAD ≥ 50%, regional stress TPD, and regional ITPD was significantly higher in vessels with events as compared to those without (both P < 0.001). The receiver operating characteristics area under the curve for regional ITPD for the identification of vessel-related events was 0.81 (95% confidence interval 0.75-0.86). An ITPD value of 2.0% provided the best trade-off for identifying the vessel-related event. At multivariable analysis, both CAD ≥ 50% and ITPD ≥ 2.0% resulted in independent predictors of events.

CONCLUSIONS

Regional myocardial perfusion assessed by the CZT camera demonstrated good reliability in predicting vessel-related events in patients with suspected or known CAD.

Cardiac imaging for the assessment of patients being evaluated for liver transplantation

Cardiac risk assessment prior to liver transplantation has become widely accepted. With the emergence of nonalcoholic steatohepatitis among the leading causes of end-stage liver disease and the steady rise of the age of liver transplant recipients, the burden of cardiovascular diseases has markedly increased in this population. Selecting appropriate liver transplant candidates is crucial due to the increasing demand for scarce donor organs. The use of noninvasive cardiac imaging for pre-operative assessment of the cardiovascular status of liver transplant recipients has been on the rise, yet the optimal assessment strategy remains an area of active debate. In this review, we examine the relevant literature pertaining to the diagnostic and prognostic applications of noninvasive cardiac imaging in this population. We also propose a simple literature-based evaluation algorithm for CAD surveillance in liver transplant candidates.

Diagnostic value of clinical risk scores for predicting normal stress myocardial perfusion imaging in subjects without coronary artery calcium

BACKGROUND

We evaluated if risk scores commonly used to predict the absence of significant stenosis at coronary computed tomography (CT) angiography are useful to predict a normal stress myocardial perfusion imaging (MPI) study.

METHODS

Our cohort included a total of 1422 consecutive patients with zero coronary artery calcium score (ZCS) who underwent 82Rb PET/CT for evaluation of suspected coronary artery disease (CAD). Predictive models were constructed as reported by Genders et al. and Alshahrani et al., and the probability of abnormal summed stress score (SSS) and of reduced myocardial perfusion reserve (MPR) based on these risk scores was assessed.

RESULTS

In the overall population, the prevalence of abnormal SSS was 0.10 and the prevalence of reduced MPR was 0.17 (both P < .001).The observed frequencies of abnormal SSS and reduced MPR vs the probabilities predicted by the Genders and Alshahrani models were above the diagonal identity line, highlighting an underestimation of the observed occurrence by these models. The areas under the receiver operating characteristic curve of the Genders and Alshahrani models indicated lack of discriminative ability for predicting abnormal SSS (0.547 and 0.527) and reduced MPR (0.509 and 0.538). The Hosmer-Lemeshow test revealed that both models underestimated the observed occurrence of abnormal SSS and reduced MPR.

CONCLUSIONS

Available models were unable to identify among patients with ZCS those with a low probability of a normal stress MPI study. Thus, an optimal approach to rule out from MPI patients without detectable coronary calcium still needs to be improved.

Relation between myocardial blood flow and cardiac events in diabetic patients with suspected coronary artery disease and normal myocardial perfusion imaging

BACKGROUND

We assessed the prognostic value of structural abnormalities and coronary vasodilator function in diabetic patients referred to a PET/CT for suspected coronary artery disease (CAD).

METHODS

We studied 451 diabetics and 451 nondiabetics without overt CAD and normal myocardial perfusion. Myocardial blood flow (MBF) was computed from the dynamic rest and stress imaging. Myocardial flow reserve (MFR) was defined as ratio of hyperemic to baseline MBF and was considered reduced when < 2.

RESULTS

During a mean follow-up of 44 months 33 events occurred. Annualized event rate (AER) was higher in diabetic than nondiabetic patients (1.4% vs 0.3%, P < .001). Diabetic patients with reduced MFR had higher AER compared to those with preserved MFR (3.3% vs 0.4%, P  < .001). At Cox analysis, age, BMI and reduced MFR were independent predictors of events in diabetic patients. Patients with diabetes and reduced MFR had lower event-free survival compared to nondiabetic patients and MFR < 2 (P < .001). Event-free survival was similar in patients with diabetes and normal MFR and those without diabetes and reduced MFR.

CONCLUSIONS

Diabetic patients with reduced MFR had higher AER and lower event-free survival compared to those with preserved MFR and to nondiabetic patients.

Prognostic values of coronary artery calcium score and 123I-BMIPP SPECT in patients with non-ischemic heart failure with preserved ejection fraction

This study aimed to determine whether coronary artery calcium score (CACS) can be a prognostic indicator for the development of major adverse cardiac events (MACEs) and compare the value of CACS with that of the ¹²³I-betamethyl-p-iodophenyl-pentadecanoic acid (¹²³I-BMIPP) defect score (BDS) in patients with non-ischemic heart failure with preserved ejection fraction (NIHFpEF). Among 643 consecutive patients hospitalized due to acute heart failure, 108 (74 ± 13y) were identified to have NIHFpEF on non-contrast regular chest computed tomography and ¹²³I-BMIPP single-photon emission computed tomography (SPECT). We evaluated whether CACS and BDS were associated with MACEs using multivariate Cox models. Thirty-two MACEs developed at a mean follow-up period of 2.4 years. CACS > 0 (hazard ratio [HR] 2.38, 95% confidence interval [CI] 1.02-5.54) and higher BDS (HR 16.00, 95% CI 5.88-43.49) were significantly associated with the development of MACEs. The proportion of patients who experienced MACEs was significantly higher in the CACS > 0 and high BDS group than in the CACS = 0 and low BDS group (3% vs. 75%, p < 0.001). CACS, as well as BDS, could serve as potential prognostic indicators in patients with NIHFpEF.

Evolution of coronary artery calcium and absolute myocardial perfusion after percutaneous revascularization: A 3-year serial hybrid [15O]H2O PET/CT imaging study

BACKGROUND AND AIMS

The value of serial coronary artery calcium (CAC) scores to predict changes in absolute myocardial perfusion and epicardial vasomotor function is poorly documented. This study explored the association between progression of CAC score and changes in absolute myocardial perfusion.

METHODS

Fifty-three patients (26% female) with de novo single-vessel coronary artery disease underwent [¹⁵O]H₂O positron emission tomography/computed tomography at 1 month (baseline), 1 year, and 3 years after complete revascularization with percutaneous coronary intervention (PCI) to assess CAC scores, hyperemic myocardial blood flow (hMBF), coronary flow reserve (CFR) and cold pressor test MBF (CPT-MBF), within the context of the VANISH trial.

RESULTS

Baseline CAC score was 0 in 9%, 0.1-99.9 in 40%, 100-399.9 in 36% and ≥400 in 15% of patients, respectively. Mixed model-analysis allowed for averaging perfusion indices over all time points: hMBF (3.74 ± 0.83; 3.33 ± 0.79; 3.08 ± 0.78 and 2.44 ± 0.74 mL min^-1·g^-1) and CFR (3.82 ± 1.12; 3.17 ± 0.80; 3.19 ± 0.81; 2.63 ± 0.92) were lower among higher baseline CAC groups (p < 0.01; p = 0.03). However, no significant interaction was found between baseline CAC groups and time after PCI for all perfusion indices, denoting that evolution of perfusion indices over time was not significantly different between CAC groups. Furthermore, CAC progression was not correlated with evolution of hMBF (r = 0.08, p = 0.57), CFR (r = 0.09, p = 0.53) or CPT-MBF (r = 0.03, p = 0.82) during 3 years of follow-up.

CONCLUSIONS

Higher baseline CAC was associated with lower hMBF and CFR. However, both baseline CAC and its progression were not associated with evolution of absolute hMBF, CFR and CPT-MBF over time, suggesting that CAC score and progression of CAC are poor indicators of change in absolute myocardial perfusion.