82-rubidium positron emission tomography determined myocardial flow reserve and outcomes following cardiac revascularisation - A multicentre registry study

BACKGROUND

Finding patients with chronic coronary syndromes (CCS) whom revascularization could benefit, is complicated. Myocardial flow reserve (MFR), a measurement of myocardial perfusion, has proven prognostic value on survival and risk of major adverse cardiac events (MACE). We investigated if MFR identifies who may benefit from revascularization.

METHODS

Among 7462 patients from Danish hospitals examined with 82Rb PET between January 2018 and August 2020, patients with ≥5% reversible perfusion defects were followed for MACE and all-cause mortality. Associations between revascularisation (within 90 days) and outcomes according to MFR (< and ≥ 2) was assessed by Cox regression adjusted by inverse probability weighting for demographics, cardiovascular risk factors, comorbidities, and 82Rb PET variables.

RESULTS

Of 1806 patients with ≥5% reversible perfusion defect, 893 (49%) had MFR < 2 and 491 underwent revascularisation (36.6% in MFR < 2 versus 17.9% MFR ≥ 2, p < 0.001). During a median follow-up of 37.0 [31.0-45.8 IQR] months, 251 experienced a MACE and 173 died. Revascularisation was associated with lower adjusted risk of all-cause mortality (hazard ratio [HR], 0.51 [95% CI, 0.30-0.88], p = 0.015) and MACE (HR, 0.54 [0.33-0.87], p = 0.012) in patients with MFR < 2 but not MFR ≥ 2 for all-cause mortality (HR 1.33 [0.52-3.40], p = 0.542) and MACE (HR 1.50 [0.79-2.84], p = 0.211). MFR significantly modified the association between revascularisation and MACE, but not all-cause mortality (interaction p-value 0.021 and 0.094, respectively).

CONCLUSIONS

Revascularization was associated with improved prognosis among patients with impaired MFR. No association was seen in patients with normal MFR. In patients with regional ischemia, MFR may identify patients with a prognostic benefit from revascularization.

Coronary microvascular disease assessed by 82Rb-PET-CT is an independent prognostic marker of all-cause mortality

Background

Coronary microvascular disease (CMD) is a major contributor to e.g. heart failure and angina pectoris, as well as being associated with an increased risk of adverse events. CMD is diagnosed by reduced myocardial blood flow reserve (MBFR), preferably by Positron emission tomography myocardial perfusion CT (PET-CT).

Purpose

We aim to determine whether reduced MBFR is associated with an increased hazard of all-cause mortality independently of the extent of perfusion defects in patients suspected of obstructive coronary artery disease.

Method

We conducted a multicenter study of all patients referred for 82Rubidium PET-CT imaging between January 2018 and August 2020. Rest and stress examinations were performed using standard imaging protocols. Percentage of perfusion defects were calculated based on summed rest- and difference score. CMD was defined as MBFR ≤2. Patients were followed for all-cause mortality through national registries with no loss to follow-up.

Results

Among the 7156 patients studied, 61.8% were men, median age was 69 [61–76 IQR] years, 14.1% had LVEF ≤40%, 58.4% had a previous diagnosis of ischemic heart disease (IHD), 20.1% had atrial fibrillation and 38.9% had MBFR ≤2.

A total of 571 (7.8) deaths were observed, more frequently in MBFR ≤2 compared to MBFR &gt;2 (4.2% vs 13.2%, p&lt;0.001). MBFR was significantly associated with reversible hypoperfusion (r2=−0.33, p&lt;0.0001). In Kaplan-Meier estimation MBFR ≤2 was significantly associated to all-cause mortality in the overall population as well as in clinically relevant subgroups defined by the extent of reversible and/or irreversible perfusion defects (p&lt;0.05 for all, fig. 1). In multivariate Cox-analysis adjusting for age, sex, Charlson's Co-morbidity index, eGFR, LVEF and LVEF-reserve and stratifying by diabetes, MBFR ≤2 remained a robust predictor of all-cause mortality with a HR 1.73, 95% CI: 1.62–2.19, p&lt;0.0001 (fig. 2). No interaction was found between MBFR and reversible hypoperfusion. In subgroup analysis including only patients with no reversible perfusion defects (n=3095), MBFR ≤2 was still strongly associated with a HR of 2.00, 95% CI: 1.29–3.11, p&lt;0.001 for all-cause mortality.

Conclusion

MBFR ≤2 is a robust predictor of all-cause mortality independently of the extent of reversible- and/or irreversible perfusion defects. Information of MBFR should be incorporated in the clinical risk stratification of patients being investigated for ischemia.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Research Committee, Bispebjerg & Frederiksberg University Hospital, scientific scholarship

Myocardial blood flow reserve assessed by 82Rb-PET-CT is associated with small-vessel disease in the kidney and brain

Background

Coronary microvascular dysfunction (CMD) may be linked to small-vessel disease in other vascular beds as a part of multisystem disorder. However, there are limited data in support of this.

Purpose

We aim to determine whether reduced myocardial blood flow reserve (MBFR) is associated with an increased hazard of small-vessel disease in the kidneys and brain.

Method

We conducted a multicenter study of all patients consecutively referred for 82Rubidium-Positron emission tomography (82Rb-PET) myocardial perfusion CT imaging between January 2018 and August 2020. CMD was defined as MBFR ≤2. Patients were followed through national registries using ICD-10 codes with no loss to follow-up for microvascular events (ME) defined as chronic kidney disease, stroke, affective disorders, and dementia. Despite the heterogeneity of outcomes, they all play a crucial role in ME, with vascular dementia, affective disorders, and both ischemic and hemorrhagic strokes being major contributors to cerebral ME.

Results

Among the 7156 patients studied, 61.8% were men, median age was 69 [61–76 IQR] years, 14.1% had LVEF ≤40%, 58.4% had a previous diagnosis of ischemic heart disease (IHD) and 20.1% had atrial fibrillation. 38.9% had MBFR ≤2. MBFR was significantly associated with eGFR at baseline (r2=0.22, p&lt;0.0001). After multivariable adjustment for demographics, cardiovascular risk factors, LVEF and reversible perfusion defects, MBFR remained significantly associated with eGFR, also in patients with no perfusion defects (β=0.039, 95% Cl 0.03–0.05, p&lt;0.001 in all patients and β=0.039, 95% Cl 0.02–0.05, p&lt;0.001, in patients with ≤5% reversible- and ≤5% irreversible hypoperfusion). During follow-up, a total of 677 (9.5%) ME were observed (480 (6.7%) cerebral ME and 197 (2.7%) renal ME). ME was more frequent in patients with MBFR ≤2 compared to MBFR &gt;2 (11.2% vs. 5.5%, p&lt;0.001).

In crude analysis MBFR ≤2 was significantly associated with ME (p&lt;0.0001, Fig. 1) as well as renal- and cerebral ME (both p&lt;0.001). Similar results were found in subgroup analysis of patients with diabetes, normal kidney function (eGFR ≥60) or no perfusion defects, respectively (Fig. 1). After multivariate adjusting for demographics, IHD, cardiovascular risk factors, Charlson's Comorbidity index, atrial fibrillation and stratifying by chronic kidney disease stages, MBFR remained a significant predictor of ME (HR 1.43, 95% CI 1.15–1.78, p&lt;0.001, fig. 2). In subgroup analysis including only patients with no reversible perfusion defects, MBFR ≤2 was associated with a HR of 2.04, 95% CI 1.43–2.91, p&lt;0.0001 for ME.

Conclusion

This is the first larger cohort study relating CMD to microvascular outcome in the kidneys and brain. We conclude that CMD is an independent predictor of cerebral and renal ME. Data support the hypothesis that CMD is part of a systemic vascular disorder.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Research Committee, Bispebjerg & Frederiksberg University Hospital, scientific scholarship

15O-water PET for evaluation of cardiopulmonary perfusion in complex cyanotic heart disease

Background

Dynamic ¹⁵O-water PET may provide information about cardiopulmonary circulation complementary to MRI and CT in complex cyanotic heart disease.

Case presentation

We present a case in which a ¹⁵O-water PET scan was used for the first time to map the complex circulation in a univentricular heart patient with dual pulmonary blood supply. The pulmonary blood supply consisted of partially oxygenated blood led from the univentricle to the lungs by the pulmonary artery, plus of venous blood from the upper body lead by a bidirectional Glenn anastomosis to the right pulmonary artery. Despite the bidirectional Glenn anastomosis, the patient developed increasing cyanosis and was considered for heart transplantation. Pulmonary perfusion measurements using MRI were inconclusive due to metal artifacts, and the patient was referred for a ¹⁵O-water PET scan. The scan showed significant venovenous collaterals bypassing the lungs. Only the left upper lung lobe was properly perfused. The mean transit time from the superior vena cava to the left ventricle was approximately four times longer than would be expected from a healthy person.

Conclusion

The case illustrates that ¹⁵O-water PET can complement CT and MRI for quantitative characterization of cardiopulmonary circulation in complex cyanotic heart disease.

Human lung microvascular endothelial cells activate allogeneic T cells through an LFA-3-dependent, but CD86-independent mechanism

To date, immunosuppressive therapy for allograft rejection is based on a generalized inhibition of the recipient's T cells, rendering the individual less resistant to infections and malignancies. In order to change this therapeutic approach towards the induction of specific transplant tolerance, it is essential to identify the cells and molecular pathways involved in direct allorecognition. An in vitro model with interferon-gamma (IFN-gamma)-stimulated human lung microvascular endothelial cells (HMVEC-L) as targets and allogenic T cells as responders was used to identify donor cells for recipient cellular immunorecognition. HMVEC-L activated purified allogenic T cells in cocultures. This activation was partly mediated by lymphocyte function antigen-3 (LFA-3), but not CD86, as shown by monoclonal antibody (mAb) inhibition. This finding was supported by the expression of LFA-3 antigen, but not CD86, on IFN-gamma-stimulated HMVEC-L. Surprisingly, even in the absence of T-cell proliferation, T cells were capable of enhancing LFA-3 antigen, but not CD86 expression on HMVEC-L. In conclusion, HMVEC-L are capable of direct allostimulation of human T cells, partly through an LFA-3-dependent costimulatory pathway. Since ICAM-1 expression on HMVEC is greatly enhanced by IFN-gamma and T cell coculturing, this molecule may serve as an additional costimulator. A reciprocal HMVEC-L stimulation by allogenic T-cells occurs, even without T-cell proliferation, possibly representing a preproliferative phase. Since this study included a single target as well as responder cell donor, further studies with multiple donors are needed to evaluate possible variations.

Increased urinary leukotriene E4 and eosinophil protein X excretion in patients with interstitial cystitis

PURPOSE

The role of cysteinyl containing leukotriene C4, D4 and E4, and eosinophil protein X in interstitial cystitis is unknown. Leukotriene E4, the end product of cysteinyl containing leukotrienes, and eosinophil protein X are markers of the activation of mast cells and eosinophils, respectively. Cysteinyl containing leukotrienes are potent and specific chemoattractants for eosinophils. We compared the urinary excretion of leukotriene E4 and eosinophil protein X in patients with interstitial cystitis and in healthy controls.

MATERIALS AND METHODS

Morning spot urine samples from nine patients with interstitial cystitis who fulfilled National Institute of Diabetes and Digestive and Kidney Diseases criteria were collected on the day of cystoscopy with biopsies. Aliquots of urine specimens were immediately centrifuged and the supernatants were stored at -80C until use. Urine samples from 9 healthy women served as controls. Urinary leukotriene E4 and eosinophil protein X were measured by enzyme immunoassay and radioimmunoassay, respectively. All determinations were performed in duplicate and normalized to urine creatinine.

RESULTS

Leukotriene E4 and eosinophil protein X were significantly increased in the morning urine of patients with interstitial cystitis compared with controls. The mean urinary excretion of leukotriene E4 plus or minus standard deviation was 148.8 +/- 62.5 and 62.2 +/- 17.5 ng./mmol. creatinine in patients and controls (p = 0.003), while the mean urinary excretion of eosinophil protein X was 109.7 +/- 70.4 and 43.7 +/- 22.0 microg./mmol. creatinine, respectively (p = 0.01). All urine cultures were negative. The mean mast cell count in detrusor biopsies in the interstitial cystitis group was 41 cells per mm.2 (range 5 to 84). Eosinophilic granulocytes were occasionally observed in the submucosa but not in the detrusor.

CONCLUSIONS

Our study shows that patients with interstitial cystitis and detrusor mastocytosis have increased urinary leukotriene E4 and eosinophil protein X. It is possible that cysteinyl containing leukotrienes and eosinophil protein X are involved in the pathogenesis of interstitial cystitis. Urinary leukotriene E4 and eosinophil protein X may be useful markers for assessing the grade of activation of mast cells and eosinophils in patients with interstitial cystitis and/or for confirming the diagnosis. However, it remains to be investigated whether the increase in urinary leukotriene E4 and eosinophil protein X correlates with interstitial cystitis symptoms.

The cysteinyl leukotriene D4 receptor antagonist montelukast for the treatment of interstitial cystitis

PURPOSE

The presence of leukotriene D4 receptors in human detrusor myocytes and increased urinary leukotriene E4 in patients with interstitial cystitis and detrusor mastocytosis imply a role for cysteinyl containing leukotrienes as proinflammatory mediators in this disease. We examined the efficacy of the cysteinyl leukotriene 1 receptor antagonist montelukast for treating patients with interstitial cystitis and detrusor mastocytosis.

MATERIALS AND METHODS

Ten women in whom interstitial cystitis was diagnosed according to National Institute of Diabetes and Digestive and Kidney Diseases criteria and who also had detrusor mastocytosis with a minimum of 28 mast cells per mm.2 muscle tissue were included in this study. Patients received a single dose of montelukast daily for 3 months. The efficacy of treatment was determined by 24-hour urinary frequency, nocturia and pain using visual analog scales.

RESULTS

After 1 month of montelukast treatment there was a statistically significant decrease in 24-hour urinary frequency, nocturia and pain which persisted during the 3 months of treatment. After 3 months 24-hour urinary frequency had decreased from 17.4 to 12 voidings (p = 0.009), nocturia had decreased from 4.5 to 2.8 (p = 0.019) and pain had decreased from 46.8 to 19.6 mm. on a visual analog scale (p = 0.006). No side effects were observed during treatment.

CONCLUSIONS

Montelukast treatment resulted in significant improvement in urinary frequency and pain. Its efficacy for decreasing urinary frequency and pain imply a role of leukotriene receptor antagonists for managing interstitial cystitis but further placebo controlled clinical studies are needed.

High-dose stabilized chlorite matrix WF10 prolongs cardiac xenograft survival in the hamster-to-rat model without inducing ultrastructural or biochemical signs of cardiotoxicity

WF10 is a stabilized chlorite matrix with immunosuppressive effects. In vitro studies have demonstrated its ability to suppress T cells and delay or abolish antigen presentation. Hence, WF10 may prove useful to prolong graft survival after transplantation. In this study, we evaluated the use of high dose WF10 as a single drug regimen in the hamster-to-rat xenotransplantation model and searched for possible cardiotoxic side effects. WF10 prolonged cardiac xenograft survival, but did not induce tolerence or inhibit pathological signs of acute rejection. Hamsters from the donor population, receiving high dose WF10 for 5 days, were compared with a matched control group. Ultrastructural examination of cardiac tissue as well as biochemical analysis of the cardiac enzymes troponin I, myoglobin and MB isoenzyme of creatine kinase showed no signs of damage. Thus, while prolonging graft survival, high dose WF10 seems to be non-cardiotoxic and as such should not contribute to the differential diagnosis of acute graft failure.

The action of cysteinyl-leukotrienes on intracellular calcium mobilization in human detrusor myocytes

OBJECTIVE

To investigate the presence of leukotriene D4 receptors in fura-2-loaded human detrusor smooth muscle cells (DSMCs) by examining the ability of leukotriene D4 to raise intracellular-free Ca2+ concentration ([Ca2+]i), to determine the origin of the leukotriene D4-mediated rise in [Ca2+]i and to investigate whether the specific leukotriene D4 receptor antagonist montelukast inhibits the Ca2+ response induced by leukotriene D4.

MATERIALS AND METHODS

Detrusor muscle biopsies were obtained from patients with benign noninvasive bladder diseases undergoing cystoscopy. DSMCs were isolated using an explant technique and maintained in culture. Only primary cultures or cells passaged up to three times were used for experiments. DSMCs were characterized with immunohistochemical staining and their identity confirmed by transmission electron microscopy. [Ca2+]i was measured in single DSMCs using the Ca2+ probe fura-2 and fluorescence-ratio microscopy.

RESULTS

Immunohistochemical staining showed that 80-99% of the cells were positive for smooth muscle alpha-actin. The ultrastructural features of the cultured cells were those of smooth muscle cells and showed no differentiation in a fibroblastic or myofibroblastic direction. Leukotriene D4 increased the level of [Ca2+]i in a dose-dependent manner. Calcium was mobilized almost exclusively from intracellular Ca2+ stores. There was a dose-dependent inhibition of the increase in [Ca2+]i by montelukast.

CONCLUSION

The present study is the first to show the presence of specific leukotriene D4 receptors in human detrusor myocytes. This may have implications for a potential pathophysiological role of leukotriene D4 in patients with interstitial cystitis and other functional or inflammatory bladder disorders.