Evaluating the prognostic value of positron-emission tomography myocardial perfusion imaging using automated software to calculate perfusion defect size

External validation of models for estimating pretest probability of coronary artery disease among individuals undergoing myocardial perfusion imaging

BACKGROUND

Clinical decisions regarding the appropriateness of noninvasive cardiac imaging among individuals with suspected coronary artery disease (CAD) rely heavily on the pretest probability of coronary artery disease (pCAD), often estimated from clinical prediction models. These models have not been validated among individuals undergoing noninvasive myocardial perfusion imaging (MPI) for suspected CAD. Thus, the objective of this study was to compare the extent of agreement and predictive performance between four published pCAD models among individuals undergoing positron emission tomography (PET MPI).

METHODS

This cross-sectional study performed at a cardiac referral center included 2383 patients with stable symptoms undergoing PET MPI for the evaluation of suspected CAD. pCAD was estimated on a per-patient basis using four distinct pCAD estimation models. All pCAD estimates were calibrated to a common standard to allow fair comparisons of agreement and predictive performance. Pairwise pCAD model disagreement was defined as percent discordance in classifying patients as low versus intermediate pCAD (<10% vs. ≥10%). Predictive performance was quantified by c-statistics with abnormal myocardial perfusion as a binary outcome.

RESULTS

Pairwise pCAD estimates demonstrated non-negligible disagreement with percent discordance between models ranging from 11% to 23%. Agreement worsened when higher thresholds for distinguishing low-intermediate pCAD were employed. All pCAD models demonstrated poor predictive performance for identifying abnormal stress perfusion with c-statistics ranging from 0.554 to 0.616.

CONCLUSIONS

pCAD estimation models showed suboptimal agreement and poor predictive performance in patients undergoing PET MPI. The transportability of pCAD models to MPI patients should be questioned and further evaluated in future studies.

Prognostic value of positron emission tomography myocardial perfusion imaging beyond traditional cardiovascular risk factors: Systematic review and meta-analysis

Background

Despite substantive growth in utilization of positron emission tomography (PET) myocardial perfusion imaging (MPI), evidence on its prognostic value is limited. We aimed to comprehensively evaluate the prognostic literature of PET perfusion measures according to the most recent American Heart Association recommendations for assessment of novel cardiovascular biomarkers.

Methods

We searched the literature for studies reporting associations of PET MPI measures and outcomes in patients with known or suspected coronary artery disease. We documented hazard ratios (HR) and 95% confidence intervals (CI) of association effects and quantitatively synthesized them with random-effects meta-analyses. Discrimination, calibration and risk reclassification after addition of PET MPI measures to standard prognostic models were documented.

Results

We identified 20 eligible studies with median n = 551 patients. In meta-analyses, the extents of ischemic and scarred myocardium were significantly associated with cardiac death. Meta-analyses of multivariate estimates for abnormal summed stress score ≥ 4 and myocardial perfusion reserve < 2 revealed significant associations with major adverse cardiovascular events [HR (95% CI) 2.30 (1.53–3.44) and 2.11 (1.33–3.36), respectively]. Changes in model discrimination, calibration or risk reclassification were reported in 5 studies (8 prognostic evaluations). There were marginal improvements in discrimination based on C index and no improvements in model calibration. Net reclassification index ranged from 9.8% to 14.2% and risk classification was significantly improved in 4/5 prognostic evaluations.

Conclusions

PET MPI measures were strongly associated with adverse patient outcomes. Risk classification was more consistently improved than discrimination and calibration after addition of PET MPI measures, but reporting of such metrics was overall limited.

Comparing changes in severe versus mild perfusion defect size in patients who underwent serial rubidium-82 positron emission tomography myocardial perfusion imaging

Serial myocardial perfusion imaging (MPI) is valuable for assessing coronary disease progression and treatment efficacy. Previous serial MPI studies emphasized severe perfusion defects, with no attention given to milder perfusion defects. Thus, this study sought to compare and identify predictors of change in severe versus mild perfusion defect size in patients who underwent serial positron emission tomography (PET) MPI. Serial PET MPI was performed in 551 patients with an average of 1.9 years between scans. Severe and mild perfusion defect size at both PETs were derived from automated software as percentage of left ventricular mass with relative tracer activity <60% (severe) and between 61% and 80% of maximum tracer activity (mild), respectively. Predictors of change in severe and mild perfusion defect size between PETs were determined. Overall, severe perfusion defect sizes improved (p <0.001) and mild perfusion defect sizes worsened (p <0.001) between PETs with individual changes being highly variable. In individuals with negligible changes in severe defect size (±2%), changes in mild defect size ranged from a worsening of 47% to an improvement of 48% of left ventricular mass. The strongest predictors of change in severe defect size were indicators of obstructive coronary disease including interval myocardial infarction, interval revascularization, history of myocardial infarction, and history of bypass surgery. Strong predictors of change in mild defect size were cardiac risk factors including male gender, body mass index, diabetes, and smoking. In conclusion, changes in mild perfusion defects may provide valuable secondary information for evaluating treatment efficacy in patients who underwent serial MPI.

Prognostic value of PET myocardial perfusion imaging in obese patients

OBJECTIVES

This study sought to determine and compare the prognostic and incremental value of positron emission tomography (PET) in normal, overweight, and obese patients.

BACKGROUND

Cardiac rubidium 82 (Rb-82) PET is increasingly being used for myocardial perfusion imaging (MPI). A strength of PET is its accurate attenuation correction, thereby potentially improving its diagnostic accuracy in obese patients. The prognostic value of PET in obese patients has not been well studied.

METHODS

A total of 7,061 patients who had undergone Rb-82 PET MPI were entered into a multicenter observational registry. All patients underwent pharmacologic Rb-82 PET and were followed for cardiac death and all-cause mortality. Based on body mass index (BMI), patients were categorized as normal (<25 kg/m(2)), overweight (25 to 29.9 kg/m(2)), or obese (≥30 kg/m(2)). Using a 17-segment model and 5-point scoring system, the percentage of abnormal myocardium was calculated for stress and rest patients categorized as normal (0%), mild (0.1% to 9.9%), moderate (10% to 19.9%), and severe (≥20%).

RESULTS

A total of 6,037 patients were followed for cardiac death (median: 2.2 years) and the mean BMI was 30.5 ± 7.4 kg/m(2). A total of 169 cardiac deaths were observed. PET MPI demonstrated independent and incremental prognostic value over BMI. Normal PET MPI conferred an excellent prognosis with very low annual cardiac death rates in normal (0.38%), overweight (0.43%), and obese (0.15%) patients. As well, both moderately and severe obese patients with a normal PET MPI had excellent prognosis (0.20% and 0.10%, respectively). The net reclassification improvement of PET was 0.46 (95% confidence interval [CI]: 0.31 to 0.61), and appeared similar in the moderately and severe obese patients which were 0.44 (95% CI: 0.12 to 0.76) and 0.63 (95% CI: 0.27 to 0.98), respectively.

CONCLUSIONS

Rb-82 PET has incremental prognostic value in all patients irrespective of BMI. In the obese population, where other modalities may have reduced diagnostic accuracy, cardiac PET appears to be a promising noninvasive modality with prognostic value.

PET/MRI: current state of the art and future potential for cardiovascular applications

Positron emission tomography-magnetic resonance imaging (PET/MRI) is emerging as a novel diagnostic modality with exciting potential for a role in multiple cardiovascular applications. The combination of the high sensitivity of PET tracers with the excellent spatial resolution and tissue characterization of cardiac MRI will provide complementary information in a variety of cardiac pathologies. While initial efforts have focused on the combination of MRI and PET for assessment of coronary artery disease, cardiomyopathy, viability, and inflammation, this new technology holds enormous potential for molecular cardiovascular imaging. This article will review the development of PET/MRI, review the current research, and discuss potential future applications.

Association between neutrophil-lymphocyte ratio and impaired myocardial perfusion in patients with known or suspected coronary disease

OBJECTIVE

To determine whether an elevated neutrophil-lymphocyte ratio (NLR) is associated with chronically impaired myocardial perfusion in patients with known or suspected coronary disease.

BACKGROUND

Elevated NLRs are positively associated with cardiac events, anatomic coronary disease, and myocardial infarct size. However, no study has evaluated the association between NLR and chronically impaired myocardial perfusion.

METHODS

This study included 683 patients undergoing cardiac positron emission tomography (PET) with a calculable NLR within 90 days of PET. The primary outcome was myocardial perfusion defect size measured in percent of left ventricular mass (%LV60).

RESULTS

NLR was independently associated with %LV60 when analyzed as both a continuous and binary outcome (p < 0.001). Individuals with NLR above the 90th percentile had a 5-fold increased likelihood of significant perfusion defects compared to individuals with NLR between the 10th and 25th percentiles (Odds ratio = 4.7, p < 0.001).

CONCLUSION

An elevated NLR demonstrated strong associations with myocardial perfusion.

Prognostic value of stress myocardial perfusion positron emission tomography: results from a multicenter observational registry

OBJECTIVES

The primary objective of this multicenter registry was to study the prognostic value of positron emission tomography (PET) myocardial perfusion imaging (MPI) and the improved classification of risk in a large cohort of patients with suspected or known coronary artery disease (CAD).

BACKGROUND

Limited prognostic data are available for MPI with PET.

METHODS

A total of 7,061 patients from 4 centers underwent a clinically indicated rest/stress rubidium-82 PET MPI, with a median follow-up of 2.2 years. The primary outcome of this study was cardiac death (n = 169), and the secondary outcome was all-cause death (n = 570). Net reclassification improvement (NRI) and integrated discrimination analyses were performed.

RESULTS

Risk-adjusted hazard of cardiac death increased with each 10% myocardium abnormal with mildly, moderately, or severely abnormal stress PET (hazard ratio [HR]: 2.3 [95% CI: 1.4 to 3.8; p = 0.001], HR: 4.2 [95% CI: 2.3 to 7.5; p < 0.001], and HR: 4.9 [95% CI: 2.5 to 9.6; p < 0.0001], respectively [normal MPI: referent]). Addition of percent myocardium ischemic and percent myocardium scarred to clinical information (age, female sex, body mass index, history of hypertension, diabetes, dyslipidemia, smoking, angina, beta-blocker use, prior revascularization, and resting heart rate) improved the model performance (C-statistic 0.805 [95% CI: 0.772 to 0.838] to 0.839 [95% CI: 0.809 to 0.869]) and risk reclassification for cardiac death (NRI 0.116 [95% CI: 0.021 to 0.210]), with smaller improvements in risk assessment for all-cause death.

CONCLUSIONS

In patients with known or suspected CAD, the extent and severity of ischemia and scar on PET MPI provided powerful and incremental risk estimates of cardiac death and all-cause death compared with traditional coronary risk factors.