Right and left ventricular uptake with Rb-82 PET myocardial perfusion imaging: markers of left main or 3 vessel disease

Clinical significance of quantitative assessment of right ventricular glucose metabolism in patients with heart failure with reduced ejection fraction

PURPOSE

Dynamic ¹⁸F-fluorodeoxyglucose (FDG) PET can be used to quantitatively assess the rate of myocardial glucose uptake (MRGlu). The aim of this study was to evaluate the clinical significance and prognostic value of right ventricular (RV) MRGlu in patients with coronary artery disease and heart failure with reduced ejection fraction.

METHODS

Patients with left ventricular ejection fraction (LVEF) ≤ 40% were consecutively enrolled for FDG PET between November 2012 and May 2017. Global LV and RV MRGlu (μmol/min/100 g) were analyzed. Outcome events were independently assessed using electronic medical records to determine hospitalization for revascularization, new-onset ischemic events, heart failure, cardiovascular, and all-cause death. Differences between LV and RV MRGlu and associations with clinical characteristics and echocardiographic data were evaluated. Associations among FDG PET findings and outcomes were analyzed using Kaplan-Meier survival analysis.

RESULTS

Seventy-five patients (mean age 62.2 ± 12.7 years, male 85.3%, LVEF 19.3 ± 8.6%) were included for analysis. The mean glucose utilization ratio of RV-to-LV (RV/LV MRGlu) was 89.5 ± 264.9% (r = 0.77, p < 0.001). Positive correlations between RV MRGlu and maximal tricuspid regurgitation peak gradient (r = 0.28, p = 0.033) and peak tricuspid regurgitation jet velocity (r = 0.29, p = 0.021) were noted. LVEF was positively correlated with LV MRGlu (r = 0.27, p = 0.018), but negatively correlated with end-diastolic volume (r = - 0.37, p = 0.001), end-systolic volume (r = - 0.54, p < 0.001), and RV/LV MRGlu (r = - 0.40, p < 0.001). However, RV MRGlu was not well correlated with LVEF. Forty-three patients received revascularization procedures after FDG PET, and 13 patients died in a mean follow-up period of 496 ± 453 days (1-1788 days), including nine cardiovascular deaths. Higher RV and LV MRGlu values, LVEF ≤ 16% and LV end-diastolic volume ≥ 209 ml of gated-PET were associated with poor overall survival and cardiac outcomes.

CONCLUSIONS

In patients with coronary artery disease and ischemic cardiomyopathy, RV glucose utilization was positively correlated with RV pressure overload, but not LVEF. Global LV and RV MRGlu, LVEF, and LV end-diastolic volume showed significant prognostic value.

Left main coronary artery disease: A review of the spectrum of noninvasive diagnostic modalities

Medically managed significant left main (LM) stem disease has been considered a determinant of increased cardiac mortality approaching 50% at 3-year follow-up. Despite the clinical significance of LM disease, studies comparing the various diagnostic modalities, especially noninvasive, are sparse. Clinicians, particularly imagers, should be aware of the strengths and weaknesses of existing modalities to diagnose LM disease as integrating many clues (history, symptoms, electrocardiogram, and stress hemodynamics are essential to suspect this diagnosis and proceed to the next step). Here we review the existing data on the current role of electrocardiography, nuclear myocardial perfusion imaging (single photon emission computed tomography and positron emission tomography), stress echocardiography, cardiac computed tomography, and cardiac magnetic resonance imaging in diagnostic evaluation of LM disease. Wherever applicable we have extended our discussion to multivessel coronary artery disease encompassing scenarios where LMS can present as LM equivalent with or without extensive multivessel coronary artery disease.

Clinical PET Myocardial Perfusion Imaging and Flow Quantification

Cardiac PET imaging is a powerful tool for the assessment of coronary artery disease. Many tracers with different advantages and disadvantages are available. It has several advantages over single photon emission computed tomography, including superior accuracy and lower radiation exposure. It provides powerful prognostic information, which can help to stratify patients and guide clinicians. The addition of flow quantification enables better detection of multivessel disease while providing incremental prognostic information. Flow quantification provides important physiologic information, which may be useful to individualize patient therapy. This approach is being applied in some centers, but requires standardization before it is more widely applied.

Cardiac PET perfusion: prognosis, risk stratification, and clinical management

Myocardial perfusion imaging (MPI) with PET has expanded significantly over the past decade. With the wider availability of PET scanners and the routine use of quantitative blood flow imaging, the clinical use of PET MPI is expected to increase further. PET MPI is a powerful tool to identify risk, to quantify risk, and to guide therapy in patients with known or suspected coronary artery disease. A large body of evidence supports the prognostic value of PET MPI and ejection fraction in intermediate- to high-risk subjects, in women, in obese individuals, and in post-coronary artery bypass grafting individuals. A normal perfusion study indicates low risk (<1% annualized rate of cardiac events of cardiac death and non-fatal myocardial infarction), while an abnormal study indicates high risk. With accurate risk stratification, high-quality images, and quantitation, PET MPI may transform the management of patients with known or suspected coronary artery disease.

Detection and severity classification of extracardiac interference in ⁸²Rb PET myocardial perfusion imaging

PURPOSE

Myocardial perfusion imaging (MPI) is used for diagnosis and prognosis of coronary artery disease. When MPI studies are performed with positron emission tomography (PET) and the radioactive tracer rubidium-82 chloride ((82)Rb), a small but non-negligible fraction of studies (∼10%) suffer from extracardiac interference: high levels of tracer uptake in structures adjacent to the heart which mask the true cardiac tracer uptake. At present, there are no clinically available options for automated detection or correction of this problem. This work presents an algorithm that detects and classifies the severity of extracardiac interference in (82)Rb PET MPI images and reports the accuracy and failure rate of the method.

METHODS

A set of 200 (82)Rb PET MPI images were reviewed by a trained nuclear cardiologist and interference severity reported on a four-class scale, from absent to severe. An automated algorithm was developed that compares uptake at the external border of the myocardium to three thresholds, separating the four interference severity classes. A minimum area of interference was required, and the search region was limited to that facing the stomach wall and spleen. Maximizing concordance (Cohen's Kappa) and minimizing failure rate for the set of 200 clinician-read images were used to find the optimal population-based constants defining search limit and minimum area parameters and the thresholds for the algorithm. Tenfold stratified cross-validation was used to find optimal thresholds and report accuracy measures (sensitivity, specificity, and Kappa).

RESULTS

The algorithm was capable of detecting interference with a mean [95% confidence interval] sensitivity/specificity/Kappa of 0.97 [0.94, 1.00]/0.82 [0.66, 0.98]/0.79 [0.65, 0.92], and a failure rate of 1.0% ± 0.2%. The four-class overall Kappa was 0.72 [0.64, 0.81]. Separation of mild versus moderate-or-greater interference was performed with good accuracy (sensitivity/specificity/Kappa = 0.92 [0.86, 0.99]/0.86 [0.71, 1.00]/0.78 [0.64, 0.92]), while separation of moderate versus severe interference severity classes showed reduced sensitivity/Kappa but little change in specificity (sensitivity/specificity/Kappa = 0.83 [0.77, 0.88]/0.82 [0.77, 0.88]/0.65 [0.60, 0.70]). Specificity was greater than sensitivity for all interference classes. Algorithm execution time was <1 min.

CONCLUSIONS

The algorithm produced here has a low failure rate and high accuracy for detection of extracardiac interference in (82)Rb PET MPI scans. It provides a fast, reliable, automated method for assessing severity of extracardiac interference.

Quantification of myocardial blood flow using PET to improve the management of patients with stable ischemic coronary artery disease

ABSTRACT 

Cardiac PET has been evolving over the past 30 years. Today, it is accepted as a valuable imaging modality for the noninvasive assessment of coronary artery disease. PET has demonstrated superior diagnostic accuracy for the detection of coronary artery disease compared with single-photon emission computed tomography, and also has a well-established prognostic value. The routine addition of absolute quantification of myocardial blood flow increases the diagnostic accuracy for three-vessel disease and provides incremental functional and prognostic information. Moreover, the characterization of the vasodilator capacity of the coronary circulation may guide proper decision-making and monitor the effects of lifestyle changes, exercise training, risk factor modification or medical therapy for improving regional and global myocardial blood flow. This type of image-guided approach to individualized patient therapy is now attainable with the routine use of cardiac PET flow reserve imaging.

Nuclear perfusion imaging for functional evaluation of patients with known or suspected coronary artery disease: the future is now

Nuclear imaging, with both single-photon emission computed tomography and PET, has a well-established role in the assessment of patients with known or suspected coronary artery disease. There is a large body of evidence regarding the diagnostic accuracy and prognostic value of these modalities, however, they continue to evolve rapidly with advances in camera and tracer technology, as well as changes in imaging protocols to increase lab efficiency, improve image quality and to decrease radiation exposure to patients. Nuclear imaging also provides insights into atherogenesis at a molecular level and can be combined with other imaging modalities, providing both functional and structural data and complimentary information on the presence of coronary disease and its functional implications.