The Effect of Heat Exposure on Myocardial Blood Flow and Cardiovascular Function.

BACKGROUND: Heat extremes are associated with greater risk for cardiovascular death. The pathophysiologic mechanisms mediating this association are unknown. OBJECTIVE: To quantify the myocardial blood flow (MBF) requirements of heat exposure. DESIGN: Experimental study. (ClinicalTrials.gov: NCT04549974). SETTING: Laboratory-based. PARTICIPANTS: 61 participants, comprising 20 healthy young adults (mean age, 28 years), 21 healthy older adults (mean age, 67 years), and 20 older adults with coronary artery disease (CAD) (mean age, 70 years). INTERVENTION: Participants were heated until their core temperature increased 1.5 °C; MBF was measured before heat exposure and at every increase of 0.5 °C in core temperature. MEASUREMENTS: The primary outcome was MBF measured by positron emission tomography-computed tomography. Secondary outcomes included heart rate, blood pressure, and body weight change. RESULTS: At a core temperature increase of 1.5 °C, MBF increased in healthy young adults (change, 0.8 mL/min/g [95% CI, 0.5 to 1.0 mL/min/g]), healthy older adults (change, 0.7 mL/min/g [CI, 0.5 to 0.9 mL/min/g]), and older adults with CAD (change, 0.6 mL/min/g [CI, 0.3 to 0.8 mL/min/g]). This represented a 2.08-fold (CI, 1.75- to 2.41-fold), 1.79-fold (CI, 1.59- to 1.98-fold), and 1.64-fold (CI, 1.41- to 1.87-fold) change, respectively, from preexposure values. Imaging evidence of asymptomatic heat-induced myocardial ischemia was seen in 7 adults with CAD (35%) in post hoc analyses. LIMITATIONS: In this laboratory-based study, heating was limited to about 100 minutes and participants were restricted in movement and fluid intake. Participants refrained from strenuous exercise and smoking; stopped alcohol and caffeine intake; and withheld ß-blockers, calcium-channel blockers, and nitroglycerin before heating. CONCLUSION: Heat exposure that increases core temperature by 1.5 °C nearly doubles MBF. Changes in MBF did not differ by age or presence of CAD, but some older adults with CAD may experience asymptomatic myocardial ischemia. PRIMARY FUNDING SOURCE: Canadian Institutes of Health Research.

Mycotic Coronary Aneurysm Associated With Biventricular Fistula.

The incidence of coronary artery aneurysm is between 1.4% and 4.9% based on autopsy or angiographic series. Mycotic coronary arteries aneurysms are very rare and represent less than 3% of all coronary aneurysms. We report the case of a patient who presented with multiple coronary mycotic aneurysms.

Flashy lungs and sarcoidosis: not always a sign of disease activity.

This is the case of a 68-year-old man with known cardiac sarcoidosis undergoing treatment with methotrexate who presented with new onset of dyspnea and lipothymia. FDG-PET/CT revealed pathological uptake within lung parenchyma which resolved following discontinuation of methotrexate, compatible with methotrexate-induced pneumonitis. This is the first case of methotrexate-induced pneumonitis documented by FDG-PET/CT.

Hyperventilation testing in the diagnosis of vasospastic angina: A clinical review and meta-analysis.

BACKGROUND: Given the limited access to invasive vasospastic reactivity testing in Western Countries, there is a need to further develop alternative non-invasive diagnostic methods for vasospastic angina (VSA). Hyperventilation testing (HVT) is defined as a class IIa recommendation to diagnose VSA by the Japanese Society of Cardiology. METHODS: In this systematic review and meta-analysis reported according to the PRISMA statement, we review the mechanisms, methods, modalities and diagnostic accuracy of non-invasive HVT for the diagnostic of VSA. RESULTS: A total of 106 articles published between 1980 and 2022 about VSA and HVT were included in the systematic review, among which 16 were included in the meta-analysis for diagnostic accuracy. Twelve electrocardiogram-HVT studies including 804 patients showed a pooled sensitivity of 54% (95% confidence intervals [CI]; 30%-76%) and a pooled specificity of 99% (95% CI; 88%-100%). Four transthoracic echocardiography-HVT studies including 197 patients revealed a pooled sensitivity of 90% (95% CI; 82%-94%) and a pooled specificity of 98% (95% CI; 86%-100%). Six myocardial perfusion imaging-HVT studies including 112 patients yielded a pooled sensitivity of 95% (95% CI; 63%-100%) and a pooled specificity of 78% (95% CI; 19%-98%). Non-invasive HVT resulted in a low rate of adverse events, ventricular arrhythmias being the most frequently reported, and were resolved with the administration of nitroglycerin. CONCLUSIONS: Non-invasive HVT offers a safe alternative with high diagnostic accuracy to diagnose VSA in patients with otherwise undiagnosed causes of chest pain.

Molecular imaging of large vessel vasculitis.

Large vessel vasculitis (LVV) affects mainly large arteries with giant cell arteritis (GCA) and Takayasu arteritis (TAK) being the two most frequent forms. Clinical symptoms can be non-specific, including headache, fatigue, weight loss, and change in vision. Untreated, LVV may also lead to serious complications such as blindness, aortic aneurysm and dissection. Therefore, rapid recognition of the disease leading to accurate diagnosis and appropriate treatment is essential. FDG-PET/CT imaging has emerged as a sensitive marker of active vascular inflammation and its use in the management of LVV is now integrated in guidelines. In this article, we will discuss the role of FDG-PET/CT for the diagnosis of LVV and monitoring of therapy, as well as review technical and interpretation parameters.

FDG-PET/CT and rest myocardial perfusion imaging to predict high-degree atrioventricular block recovery in cardiac sarcoidosis.

BACKGROUNDS: High-degree atrioventricular block (AVB) recovery in CS has been shown to be highly variable despite immunosuppressive treatment, with no reliable tool available to predict odds of reversibility. This study sought to evaluate the potential of combined fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and resting myocardial perfusion imaging (rMPI) to predict reversibility of newly diagnosed high-grade AVB in cardiac sarcoidosis (CS). METHODS: We performed a single-center, retrospective analysis of patients with CS presenting with high-grade AVB who underwent combined FDG-PET/CT and rMPI. The 2016 JCS and the 2014 HRS diagnostic criteria were used for the diagnosis of CS. Patients with a history of coronary artery disease or prior immunosuppressive treatment were excluded. Patients were divided into AVB recovery and non-recovery subgroups. CS disease staging was based on FDG-PET and rMPI findings: (Stage 0) normal FDG-PET and rMPI (Stage 1) positive FDG-PET and normal rMPI (Stage 2) positive FDG-PET with perfusion deficits on rMPI (Stage 3) normal FDG-PET with perfusion deficits on rMPI. RESULTS: Twenty-seven patients, including 13 demonstrating AVB recovery, were identified. Eleven out of fourteen (78.6%) patients presenting with stage 1 CS demonstrated AVB recovery. Stage 1 CS was significantly more present in the recovery group compared to the non-recovery group (84.6% vs 21.4%, P = .002). Eleven presented with stage 2 CS, with only 2 (18.2%) recovering AV nodal conduction. Stage 2 CS presented more frequently in the non-recovery group (64.3% vs 15.4%, P = .020). CONCLUSIONS: Combined FDG-PET and rMPI employed to stage CS disease presenting with high-degree AVB appears to have good performance for predicting likelihood of recovery.

Non-invasive diagnosis of vasospastic angina.

Vasospastic angina (VSA), or variant angina, is an under-recognized cause of chest pain and myocardial infarction, especially in Western countries. VSA leads to a declined quality of life and is associated with increased morbidity and mortality. Currently, the diagnosis of VSA relies on invasive testing that requires the direct intracoronary administration of ergonovine or acetylcholine. However, invasive vasoreactivity testing is underutilized. Several non-invasive imaging alternatives have been proposed to screen for VSA. This review aims to discuss the strengths and limitations of available non-invasive imaging tests for vasospastic angina.

Integration of 3D nuclear imaging in 3D mapping system for ventricular tachycardia ablation in patients with implanted devices: Perfusion/voltage retrospective assessment of scar location.

Background: The identification of low-voltage proarrhythmic areas for catheter ablation of scar-mediated ventricular tachycardia (VT) remains challenging. Integration of myocardial perfusion imaging (single-photon emission computed tomography/computed tomography; SPECT/CT) and electroanatomical mapping (EAM) may improve delineation of the arrhythmogenic substrate. Objective: To assess the feasibility of SPECT/CT image integration with voltage maps using the EnSite Precision system (Abbott) in patients undergoing scar-mediated VT ablation. Methods: Patients underwent SPECT/CT imaging prior to left ventricular (LV) EAM with the EnSite Precision mapping system. The SPECT/CT, EAM data, and ablation lesions were retrospectively co-registered in the EnSite Precision system and exported for analysis. Segmental tissue viability scores were calculated based on SPECT/CT perfusion and electrogram bipolar voltage amplitude. Concordance, specificity, and sensitivity between the 2 modalities as well as the impact of SPECT/CT spatial resolution were evaluated. Results: Twenty subjects (95% male, 67 ± 7 years old, left ventricular ejection fraction 36% ± 11%) underwent EAM and SPECT/CT integration. A concordance of 70% was found between EAM and SPECT/CT for identification of cardiac segments as scar vs viable, with EAM showing a 68.5% sensitivity and 76.4% specificity when using SPECT/CT as a gold standard. Projection on low-resolution 3D geometries led to an average decrease of 38% ± 22% of the voltage points used. Conclusion: The study demonstrated the feasibility of integrating SPECT/CT with EAM performed retrospectively for characterization of anatomical substrates during VT ablation procedures.

Improving Detection of CAD and Prognosis with PET/CT Quantitative Absolute Myocardial Blood Flow Measurements.

PURPOSE OF REVIEW: The purpose of this review is to provide an overview of the role of PET MPI in the detection of CAD, focussing on the added value of MBF for diagnosis and prognostication. RECENT FINDINGS: Positron emission tomography (PET) myocardial perfusion imaging (MPI) is increasingly used for the risk stratification of patients with suspected or established coronary artery disease (CAD). PET MPI provides accurate and reproducible non-invasive quantification of myocardial blood flow (MBF) at rest and during hyperemia, providing incremental information over conventional myocardial perfusion alone. Inclusion of MBF in PET MPI interpretation improves both its sensitivity and specificity. Moreover, quantitative MBF measurements have repeatedly been shown to offer incremental and independent prognostic information over conventional clinical markers in a broad range of conditions, including in CAD. Quantitative MBF measurement is now an established and powerful tool enabling accurate risk stratification and guiding patients' management. The role of PET MPI and flow quantification in cardiac allograft vasculopathy (CAV), which represents a particular form of CAD, will also be reviewed.

Impact of rubidium imaging availability on management of patients with acute chest pain.

OBJECTIVE: Evaluate the impact of 82-Rubidium positron emission tomography (PET) myocardial perfusion imaging (MPI) availability on patient management presenting at the emergency department (ED) with chest pain (CP). METHODS: This is a single-center retrospective study of clinical databases. Patients presenting with CP with a non-definitive suspicion of acute coronary syndrome (ACS) at the ED between April 2016 and February 2020 were divided into 2 groups based on PET availability. The proportion of invasive coronary angiography (ICA) without significant coronary artery disease (CAD), length of stay (LoS), and additional downstream testing were evaluated. RESULTS: There were 21,242 ED visits for CP without definitive ACS: 5,492 when PET is not available and 15,750 when PET is available. When PET is available, proportion of patients undergoing a MPI study was greater (20.7% vs 17.6%, P<0.0001), proportion of ICA without significant CAD was similar (18.5% vs 21.4%, P=0.24), and median ED LoS was shorter (16.6 vs 18.1 hours, P=0.03). Patients undergoing SPECT MPI had significantly more downstream testing (8.9% vs 6.4%, P=0.003) and a higher rate of coronary angiogram without significant CAD (21.2% vs 14.2%, P=0.09) compared to those who underwent PET MPI. CONCLUSION: Availability of PET MPI was associated with an increased number of MPI referral from the ED, similar rates of ICA without significant CAD, decreased LoS, and fewer downstream testing.

OBJETIVO: Evaluar el impacto de la tomografía por emisión de positrones (PET) con 82-Rubidio y la disponibilidad de imágenes de perfusión miocárdica (MPI) en el manejo de los pacientes que se presentan en el servicio de urgencias (ED) con dolor torácico (CP). MéTODOS: Este es un estudio retrospectivo de bases de datos clínicas de un solo centro. Pacientes que presentaron CP con sospecha no definitiva de síndrome coronario agudo (ACS) en el ED entre abril de 2016 y febrero de 2020, se dividieron en 2 grupos según la disponibilidad de PET. Se evaluó la proporción de angiografía coronaria invasiva (ICA) sin enfermedad arterial coronaria (CAD) significativa, la duración de la estancia (LoS) y las pruebas posteriores adicionales. RESULTADOS: Hubo 21,242 visitas al ED por CP sin ACS definitivo: 5,492 cuando no se dispone de PET y 15.750 cuando se dispone de PET. Cuando se dispone de PET, la proporción de pacientes sometidos a estudio de MPI fue mayor (20.7% vs 17.6%, p=0.03). Los pacientes que se sometieron a SPECT MPI tuvieron significativamente más pruebas posteriores (8.9 % frente a 6.4 %, p = 0.003) y una tasa más alta de angiografía coronaria sin CAD significativa (21.2 % frente a 14.2 %, p = 0.09) en comparación con los que se sometieron a PET MPI. CONCLUSIóN: La disponibilidad de PET MPI se asoció con un mayor número de referencias de MPI desde el ED, tasas similares de ICA sin CAD significativa, disminución de LoS y menos pruebas posteriores.

[18F]FDG-PET CT for the evaluation of native valve endocarditis.

BACKGROUND: We examined the use of [18F]FDG-PET/CT for the diagnosis of native valve endocarditis (NVE). METHODS: PET/CT images in patients with suspected NVE were retrospectively reviewed independently by two experienced physicians blinded to all clinical information. The gold standard consisted of surgical findings, when available, or the modified Duke criteria. RESULTS: Fifty four subjects were included, 31 (57%) with a diagnosis of NVE. [18F]FDG-PET/CT correctly identified 21/31 (67.7%) subjects, yielding a sensitivity and specificity of 68% (95% CI 49-83%) and 100% (95% CI 85-100%), respectively. The sensitivity and specificity of the modified Duke criteria were 48% and 74%, respectively. Positive and negative predictive values of PET were 100% (95% CI 84-100%) and 70% (95% CI 51-84%), respectively. Modifying the Duke criteria to include [18F]FDG-PET positivity as a major criterion increased sensitivity to 77% without affecting specificity and led to the correct reclassification of 8/18 (44.4%) subjects from Possible IE to Definite IE. CONCLUSION: The addition of a positive [18F]FDG-PET/CT as a major criterion in the modified Duke Criteria improved performance of the criteria for the diagnosis of NVE, particularly in those subjects with Possible IE.

Comparison of 18F-sodium fluoride positron emission tomography imaging and 99mTc-pyrophosphate in cardiac amyloidosis.

BACKGROUND: Pyrophosphate (PYP) scintigraphy provides high diagnostic accuracy for the detection of transthyretin (ATTR) cardiac amyloidosis (CA). There has recently been emerging interest in using 18F-sodium fluoride (NaF) for this application, yet its sensitivity has never been directly compared to that of PYP, the current molecular gold standard METHODS: Twelve subjects with ATTR-CA and 5 controls referred for PYP-SPECT were prospectively enrolled. 18F-NaF PET/CT scans were performed at 1 and 3 hours. Qualitative and quantitative analyses of the images were performed, and the sensitivity of 18F-NaF PET/CT and PYP-SPECT were compared RESULTS: Visual interpretation of NaF PET/CT yielded a sensitivity of 0.25 (95% CI 0.089 to 0.53) for the detection of ATTR-CA, which is significantly inferior to that of PYP-SPECT/CT (100%, P = .016). Visual interpretation at 3 hours yielded a similar sensitivity of 0.30 (95% CI 0.11 to 0.60, P = 1.00). There were no false-positive NaF PET studies. Mean target-to-background ratio (TBRmean) at 1h did not differ significantly (P = .21) in ATTR-CA subjects (0.83 ± 0.15) compared to controls (0.72 ± 0.15). Receiver operating characteristic (ROC) analysis yielded an area under the curve (AUC) of 0.69 ± 0.16 (95% CI 0.37 to 1.00, P = .23). CONCLUSION: With qualitative and quantitative analyses, sensitivity of NaF PET/CT is significantly inferior to that of PYP-SPECT for the diagnosis of ATTR-CA.

SPECT imaging of pulmonary vascular disease in bleomycin-induced lung fibrosis using a vascular endothelium tracer.

BACKGROUND: Pulmonary hypertension (PH) complicating idiopathic pulmonary fibrosis (IPF) is associated to worse outcome. There is a great need for a non-invasive diagnostic modality to detect and evaluate the severity of pulmonary vascular disease (PVD). 99mTc-PulmoBind is a novel imaging agent that binds to the adrenomedullin (AM) receptor on the pulmonary microvascular endothelium. SPECT imaging employing the endothelial cell tracer 99mTc-PulmoBind was used to assess PVD associated with lung fibrosis. METHODS: Rats with selective right lung bleomycin-induced fibrosis were compared to control rats. SPECT imaging was performed after three weeks with 99mTc-PulmoBind and 99mTc-macroaggregates of albumin (MAA). PH and right ventricular (RV) function were assessed by echocardiography. Lung perfusion was evaluated by fluorescent microangiography. Lung AM receptor expression was measured by qPCR and by immunohistology. Relevance to human IPF was explored by measuring AM receptor expression in lung biopsies from IPF patients and healthy controls. RESULTS: The bleomycin group developed preferential right lung fibrosis with remodeling and reduced perfusion as assessed with fluorescent microangiography. These rats developed PH with RV hypertrophy and dysfunction. 99mTc-PulmoBind uptake was selectively reduced by 50% in the right lung and associated with reduced AM receptor expression, PH and RV hypertrophy. AM receptor was co-expressed with the endothelial cell protein CD31 in alveolar capillaries, and markedly reduced after bleomycin. Quantitative dynamic analysis of 99mTc-PulmoBind uptake in comparison to 99mTc-MAA revealed that the latter distributed only according to flow, with about 60% increased left lung uptake while left lung uptake of 99mTc-PulmoBind was not affected. Lung from human IPF patients showed important reduction in AM receptor expression closely associated with CD31. CONCLUSIONS: SPECT imaging with 99mTc-PulmoBind detects PVD and its severity in bleomycin-induced lung fibrosis. Reduced AM receptor expression in human IPF supports further clinical development of this imaging approach.

Assessing cardiovascular infection and inflammation with FDG-PET.

FDG-PET has been shown to be a useful imaging modality for the assessment of cardiovascular infection and inflammatory pathologies. However, interpretation of these studies can be challenging in light of the variability of physiological myocardial uptake and, occasionally, interpreter's lack of familiarity with the typical findings present in cardiac pathologies. In this article, we review established and emerging applications for cardiovascular infection and inflammation imaging with FDG-PET and present typical examples of representative pathologies.

Examining the sensitivity of 18F-NaF PET for the imaging of cardiac amyloidosis.

BACKGROUND: Conventional nuclear imaging with bone-seeking radiopharmaceuticals has been shown to be a sensitive test for the detection of transthyretin cardiac amyloidosis (ATTR); however, to date, few data exist on the utility of 18F-sodium fluoride (NaF) positron emission tomography (PET) in subjects with cardiac amyloidosis (CA). METHODS: Myocardial perfusion imaging and cardiac 18F-NaF PET/CT of 7 subjects with ATTR, four with light-chain CA (AL), and four controls were retrospectively reviewed. Qualitative interpretation and quantitative analyses with average left ventricular standardized uptake values (SUVmean) and target-to-background ratios (TBRmean) were performed. RESULTS: Average TBRmean was significantly increased in subjects with ATTR (0.98 ± 0.09) compared to AL (0.85 ± 0.08, P = .026) and CTL (0.82 ± 0.07, P = .020), while SUVmean was not (P = .14). Receiver-operator characteristic (ROC) analysis yielded an area under the curve (AUC) of 0.91, with a sensitivity/specificity of 75%/100% for TBRmean using a cutoff value of 0.89 for the diagnosis of ATTR. Qualitative interpretation resulted in a sensitivity/specificity of 57%/100% for ATTR. CONCLUSIONS: While 18F-NaF PET/CT demonstrates good diagnostic accuracy for ATTR, particularly when using quantitative analysis, the low TBRmean values observed in ATTR indicate poor myocardial signal. 18F-NaF PET/CT is not yet ready for clinical use in CA until further comparison studies are performed with 99mTc-DPD/PYP.

Site qualification and clinical interpretation standards for 99mTc-SPECT perfusion imaging in a multi-center study of MITNEC (Medical Imaging Trials Network of Canada).

BACKGROUND: Qualification and interpretation standards are essential for establishing 99mTc-SPECT MPI accuracy vs. alternative modalities. METHODS: Rest-stress 99mTc-SPECT phantom scans were acquired on 35 cameras. LV defects were quantified with summed stress (SSS) and difference scores (SDS) at 2 core labs. SDS ≥ 2 in the right coronary artery (RCA) was the qualifying standard. Twenty rest (R)-stress (S) patient images were acquired on qualified cameras and interpreted by core labs. Global scoring differences > 3 between labs or discordant clinical interpretations underwent review. Scoring, interpretation, image quality, and diagnostic parameter agreement were assessed. RESULTS: Phantom scans: visual scoring confirmed RCA-ischemia on all cameras. Regional SSS, SDS agreement was moderate to very good: ICC-r = 0.57, 0.84. Patient scans: 90% of global SSS, 85% of SDS differences were ≤ 3. Regional SSS, SDS agreement: ICC-r = 0.87, 0.86, and global abnormal (SSS ≥ 4) and ischemic (SDS ≥ 2) interpretation: ICC-r = 0.90 were excellent. Clinical interpretation agreement was 100% following review. Image quality agreement was 70%. Automated metrics also agreed: ischemic total perfusion deficit ICC-r = 0.75, reversible perfusion defect, transient ischemic dilation, and S-R LV ejection fraction ICC-r ≥ 0.90. CONCLUSION: Quantitative scoring and interpretation of scans were highly repeatable with site qualification and clinical interpretation standardization, indicating that dual-core lab interpretation is appropriate to determine 99mTc-SPECT MPI accuracy.

Detection of Native and Prosthetic Valve Endocarditis: Incremental Attributes of Functional FDG PET/CT over Morphologic Imaging.

PURPOSE OF REVIEW: The clinical and incremental value of functional imaging with 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG PET/CT) for the diagnosis and management of patients with suspected native and prosthetic valve infective endocarditis (IE). RECENT FINDINGS: The diagnosis of IE is challenging because of the highly variable clinical presentations, especially in the case of prosthetic valve endocarditis (PVE). FDG PET/CT has been shown to play an important role for the diagnosis of PVE as a major Duke criterion. Whether FDG PET/CT could play a similar role in patients with suspected native valve endocarditis (NVE) is less well established. It is increasingly recognized that IE is a multisystem disorder, and identification of extra-cardiac manifestations on whole-body FDG PET/CT impacts management and prognosis of patients with IE. Finally, FDG PET/CT provides incremental prognostic value over other clinical and para-clinical parameters, enabling prediction of in-hospital mortality, IE recurrence, hospitalization, and new onset heart failure and embolic events. FDG PET/CT plays a key role in the investigation of patients with suspected IE, enabling detection of valvular infection and extra-cardiac manifestations of the infection which has important prognostic implications.

Tc-99m-pyrophosphate scintigraphy for the diagnosis of ATTR cardiac amyloidosis: Comparison of quantitative and semi-quantitative approaches.

BACKGROUND: ATTR cardiac amyloidosis (CA) can be diagnosed with Tc-99m-PYP scintigraphy. There are two recommended interpretative approaches: the quantitative heart-to-contralateral lung ratio (H/CL) at 1 hour and the semi-quantitative visual system at 3 hours. This study's aim was to compare both approaches and to apply the semi-quantitative method at 1 hour. METHODS: Tc-99m-PYP scans of 122 consecutive subjects were reviewed using both approaches. On 1 hour planar images, regions of interest were drawn over the heart and contralateral chest to determine H/CL. Myocardial uptake was graded on 1 and 3 hour SPECT images according to the semi-quantitative method. Concordance was examined using kappa statistics. RESULTS: 31, 10, and 81 studies were positive, negative, and equivocal, respectively, for ATTR-CA using the H/CL approach. Using the grading system, 35, 77, and 10 scans were positive, negative, and equivocal, respectively. The quantitative approach led to a significantly higher proportion of equivocal studies compared to the semi-quantitative approach (P < .0001). These approaches yielded discordant results in 2 subjects; biopsy results were concordant with SPECT grade. 1 and 3 hour SPECT grades provided concordant result in 99% of cases. CONCLUSIONS: The H/CL approach resulted in a high proportion of equivocal studies. Using SPECT imaging, the semi-quantitative approach minimized this proportion and showed high concordance at 1 and 3 hours.

Comparison of two dipyridamole infusion protocols for myocardial perfusion imaging in subjects with low likelihood of significant obstructive coronary artery disease.

BACKGROUND: Myocardial perfusion imaging (MPI) with positron emission tomography allows accurate measurements of myocardial blood flow (MBF). Stress MBF thresholds have been proposed to provide diagnostic and prognostic information in different pathology. Most studies relying on dipyridamole use a 5-minute infusion protocol, while current guidelines recommend a 4-minute infusion. The purpose of this study is to compare the effects of different dipyridamole infusion times on stress MBF. METHODS: The charts of 2,207 patients who underwent rubidium-82 MPI were retrospectively reviewed and 147 subjects with low likelihood of significant coronary artery disease (CAD) defined as calcium score = 0, body mass index < 45 kg·m-2, and summed stress score ≤ 3 were included. Of those, 65 were imaged with a 4-minute dipyridamole infusion (0.56 mg·kg-1) protocol and 82 with a 5-minute protocol (0.70 mg·kg-1). RESULTS: Stress MBF (3.23±0.76 vs 3.02±0.71 mL·min-1·g-1, P = 0.09), myocardial flow reserve (2.70±0.67 vs 2.85±0.74, P = 0.20), and coronary vascular resistance index (30±10 vs 31±9 mmHg × g × min·mL-1, P = 0.38) were not significantly different between the two protocols. The 5-minute protocol was associated with higher prevalence of symptoms (92.7% vs 81.5%, P = 0.04) and greater decrease in systolic blood pressure (- 9 vs - 6 mmHg, P = 0.03). CONCLUSIONS: The 4-minute and 5-minute dipyridamole infusion protocols produce comparable myocardial flow response, hemodynamic changes, and symptoms, in subjects with low likelihood of significant obstructive CAD.