Brief ReportPatient-tailored risk assessment of obstructive coronary artery disease using Rubidium-82 PET-based myocardial flow quantification with visual interpretation
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 patientās 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: 18ā27].
Of the
Discussion
In this study, we estimated the patientās 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 patientās 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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