Brief Report
Patient-tailored risk assessment of obstructive coronary artery disease using Rubidium-82 PET-based myocardial flow quantification with visual interpretation

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Abstract

Introduction

Our aim was to estimate the probability of obstructive CAD (oCAD) for an individual patient as a function of the myocardial flow reserve (MFR) measured with Rubidium-82 (Rb-82) PET in patients with a visually normal or abnormal scan.

Materials and Methods

We included 1519 consecutive patients without a prior history of CAD referred for rest-stress Rb-82 PET/CT. All images were visually assessed by two experts and classified as normal or abnormal. We estimated the probability of oCAD for visually normal scans and scans with small (5%ā€“10%) or larger defects (> 10%) as function of MFR. The primary endpoint was oCAD on invasive coronary angiography, when available.

Results

1259 scans were classified as normal, 136 with a small defect and 136 with a larger defect. For the normal scans, the probability of oCAD increased exponentially from 1% to 10% when segmental MFR decreased from 2.1 to 1.3. For scans with small defects, the probability increased from 13% to 40% and for larger defects from 45% to > 70% when segmental MFR decreased from 2.1 to 0.7.

Conclusion

Patients with > 10% risk of oCAD can be distinguished from patients with < 10% risk based on visual PET interpretation only. However, there is a strong dependence of MFR on patientā€™s individual risk of oCAD. Hence, combining both visual interpretation and MFR results in a better individual risk assessment which may impact treatment strategy.

Introduction

The use of myocardial blood flow (MBF) quantification using Rubidium-82 (Rb-82) in myocardial perfusion imaging (MPI) with positron emission tomography (PET) is rapidly increasing.1, 2, 3 This is mainly caused by the availability of Strontium-82/Rb-82 generators and the better accuracy of PET in comparison to SPECT imaging.4,5 Global myocardial flow reserve (MFR) values provide incremental prognostic value over visual interpretation of the PET scans and help better identify patients at risk of cardiac events.6,7 To prevent the development of cardiac events, a patient-tailored risk assessment of obstructive CAD (oCAD) is essential for choosing an appropriate treatment strategy. PET-based MFR in combination with visual assessment can be used for this purpose, as in clinical practice, PET is used to assess the presence, extent, and functional importance of oCAD.7,8 However, in assessing patientā€™s risk of oCAD, it is unclear how MFR should be combined with visual assessment, especially when they are discordant. How should the readers interpret patients with a normal scan and low MFR, or patients with an abnormal scan but high MFR? Hence, our aim was to estimate the probability of oCAD for an individual patient as a function of the MFR in patients with a visually normal scan as well as in patients with a visually abnormal scan.

Section snippets

Study population

We retrospectively included 1519 patients referred for rest and regadenoson-induced stress Rb-82 PET/CT (GE Discovery 690, GE Healthcare) without a prior history of CAD and of whom at least one-year follow-up was available. As this study was retrospective, approval by the medical ethics committee was, therefore, not required according to Dutch law. Nevertheless, all patients provided written informed consent for the use of their data for research purposes.

Patient preparation, data acquisition, and reconstruction

All subjects were asked to refrain from

Results

Of all 1519 patients, 83% (1259) had a scan which was classified as normal and the remaining patients had a scan which was classified as abnormal. These two groups did not differ in weight, body mass index (BMI), and the risk factors such as smoking, hypertension, dyslipidaemia, diabetes, and family history (P ā‰„ .07), as shown in Table 1. Yet patients with abnormal scans were older, taller, and more often male (P ā‰¤ .01). The median follow-up was 23 months [interquartile range: 18ā€“27].

Of the

Discussion

In this study, we estimated the patientā€™s probability of having oCAD based on the combination of visual assessment of Rb-82 PET scans and MFR values. Although a visual interpretation seems to be sufficient to discriminate patients with a probability > 10% from patients with a probability < 10% patients, our study showed that MFR can be used for a more patient-tailored risk assessment, as the probability of an individual patient having oCAD strongly depends on MFR (as shown in Figs. 1 and 2).

New Knowledge Gained

In clinical practice, Rb-82 PET-based MFR in combination with visual assessment is used to diagnose oCAD as recently recommended by guidelines.7,8 However, in diagnosing oCAD, it is unclear how visual assessment can be combined best with MFR, especially when MFR is discrepant from the qualitative interpretation. We provided a probability function that can be used in clinical practice and is of particular value for patients with a normal PET scan and low MFR and vice versa. In these cases, the

Conclusion

In estimating the probability of a patient having oCAD using Rb-82 PET, both visual interpretation and MFR measurements are essential. Patients with a probability > 10% can be distinguished from patients with a probability < 10% based on visual interpretation only. However, there is a strong dependence of MFR on patientā€™s individual probability of having oCAD: these probabilities may range from < 1% to > 80%. Hence, combining both visual interpretation and MFR results in a better individual

Disclosures

The authors have indicated that they have no financial conflict of interest.

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