Increased basal myocardial perfusion in patients with chronic kidney disease without symptomatic coronary artery disease

Prognostic Impact of Coronary Flow Reserve in Patients With CKD

Introduction

Both coronary flow reserve (CFR) and chronic kidney disease (CKD) are known to be associated with adverse cardiac events. However, it is unclear how these prognostic factors are interrelated. This study evaluated the association between intracoronary physiologic indexes and CKD and their prognostic implications.

Methods

A total of 351 patients without left ventricular systolic dysfunction (ejection fraction ≥ 40%) and not on dialysis whose revascularization was deferred based on fractional flow reserve (FFR) > 0.80 were analyzed. Depressed CFR was defined as CFR ≤ 2.0. The primary outcome was a composite of cardiac death or hospitalization for heart failure at 3 years.

Results

Patients with CKD showed lower CFR than the non-CKD population (3.28 ± 1.77 vs. 2.60 ± 1.09, P < 0.001), mainly driven by increased resting coronary flow. There was no significant difference in hyperemic coronary flow, FFR, and index of microvascular resistance between the 2 groups. CFR was significantly associated with estimated glomerular filtration rate (eGFR) (P = 0.045), and the proportion of depressed CFR was significantly increased with higher CKD stages (P = 0.011). The risk of cardiac death or hospitalization for heart failure was the lowest in the non-CKD and preserved CFR group (11.9%) and the highest in the CKD and depressed CFR group (60.0%, overall log rank P < 0.001). Both CKD (adjusted hazard ratio [HR_adj] 2.614, 95% confidence interval [CI] 1.505-4.539, P < 0.001) and depressed CFR (HR_adj 3.237, 95% CI 2.015-5.199, P < 0.001) were independently associated with the risk of the primary outcome.

Conclusion

There was a significant association between severity of CKD and CFR. Both CKD and depressed CFR showed independent association with higher risk of cardiac death or hospitalization for heart failure.

Coronary flow abnormalities in chronic kidney disease: A systematic review and meta-analysis

BACKGROUND

Coronary vasomotion abnormalities have been described in small studies but not studied systematically. We aimed to review the present literature and analyze it to improve our understanding of chronic kidney disease (CKD) related-coronary microvascular dysfunction.

OBJECTIVE

Coronary flow reserve (CFR) is a well-known measure of coronary vasomotion. We aimed to assess the difference in CFR among participants with and without CKD.

METHODS

PubMed, Embase, and Cochrane CENTRAL were systematically reviewed to identify studies that compared CFR in participants with and without CKD. We estimated standardized mean differences in mean CFR reported in these studies. We performed subgroup analyses according to imaging modality, and the presence of significant epicardial coronary artery disease.

RESULTS

In 14 observational studies with 5966 and 1410 patients with and without CKD, the mean estimated glomerular filtration rate (eGFR) was 29 ± 04 and 87 ± 25 ml/min/1.73 m² , respectively. Mean CFR was consistently lower in patients with CKD in all studies and the cumulative mean difference was statistically significant (2.1 ± .3 vs. 2.7 ± .5, standardized mean difference -.8, 95% CI -1.1, -.6, p < .05). The lower mean CFR was driven by both significantly higher mean resting flow velocity (.58 cm/s, 95% CI .17, .98) and lower mean stress flow velocity (-.94 cm/s, 95% CI -1.75, -.13) in studies with CKD. This difference remained significant across diagnostic modalities and even in absence of epicardial coronary artery disease. In meta-regression, there was a significant positive relationship between mean eGFR and mean CFR (p < .05).

CONCLUSION

Patients with CKD have a significantly lower CFR versus those without CKD, even in absence of epicardial coronary artery disease. There is a linear association between eGFR and CFR. Future studies are required to understand the mechanisms and therapeutic implications of these findings.

KEY POINTS

In this meta-analysis of observational studies, there was a significant reduction in coronary flow reserve in studies with chronic kidney disease versus those without. This difference was seen even in absence of epicardial coronary artery disease. In meta-regression, a lower estimate glomerular filtration rate was a significant predictor of lower coronary flow reserve. Coronary microvascular dysfunction, rather than atherosclerosis-related epicardial disease may underly increase cardiovascular risk in a patient with chronic kidney disease.

Coronary artery calcium burden, carotid atherosclerotic plaque burden, and myocardial blood flow in patients with end-stage renal disease: A non-invasive imaging study combining PET/CT and 3D ultrasound

BACKGROUND

Imaging-based measures of atherosclerosis such as coronary artery calcium score (CACS) and coronary flow reserve (CFR) as well as carotid atherosclerotic plaque burden (cPB) are predictors of cardiovascular events in the general population. The objective of this study was to correlate CACS, cPB, myocardial blood flow (MBF), and CFR in patients with end-stage renal disease (ESRD).

METHODS AND RESULTS

39 patients (mean age 53 ± 12 years) with ESRD prior to kidney transplantation were enrolled. MBF and CFR were quantified at baseline and under hyperemia by 13N-NH3-PET/CT. CACS was calculated from low-dose CT scans acquired for PET attenuation correction. cPB was assessed by 3D ultrasound. Uni- and multivariate regression analyses between these and clinical parameters were performed. Median follow-up time for clinical events was 4.4 years. Kaplan-Meier survival estimates with log-rank test were performed with regards to cardiovascular (CV) events and death of any cause. CACS and cPB were associated in ESRD patients (r = 0.48; p ≤ 0.01). While cPB correlated with age (r = 0.43; p < 0.01), CACS did not. MBFstress was negatively associated with age (r = 0.44; p < 0.01) and time on dialysis (r = 0.42; p < 0.01). There were negative correlations between MBFstress and CACS (r = - 0.62; p < 0.001) and between MBFstress and cPB (r = - 0.43; p < 0.01). Age and CACS were the strongest predictors for MBFstress. CFR was impaired (< 2.0) in eight patients who also presented with higher cPB and higher CACS compared to those with a CFR > 2.0 (p = 0.06 and p = 0.4). In contrast to MBFstress, there was neither a significant correlation between CFR and CACS (r = - 0.2; p = 0.91) nor between CFR and cPB (r = - 0.1; p = 0.55). CV event-free survival was associated with reduced CFR and MBFstress (p = 0.001 and p < 0.001) but not with cPB or CACS.

CONCLUSIONS

CACS, cPB, and MBFstress are associated in patients with ESRD. Atherosclerosis is earlier detected by MBFstress than by CFR. CV event-free survival is associated with impaired CFR and MBFstress.

End-stage renal failure is associated with impaired coronary microvascular function

BACKGROUND

Cardiovascular disease is the leading cause of death in patients with chronic kidney disease. Studies investigating the disproportionate burden of cardiovascular disease have occurred predominantly in the peripheral vasculature, often used noninvasive imaging modalities, and infrequently recruited patients receiving dialysis. This study sought to evaluate invasive coronary dynamic vascular function in patients with end-stage renal failure (ESRF).

PATIENTS AND METHODS

Patients referred for invasive coronary angiography prior to renal transplantation were invited to participate. Control patients were recruited in parallel. Baseline characteristics were obtained. Coronary diameter (via quantitative coronary angiography) and coronary blood flow (via Doppler Flowire) were measured; macrovascular endothelial-dependent and independent effects were evaluated in response to intracoronary acetylcholine infusion (10 and 10 mol/l) and intracoronary glyceryl trinitrate, respectively. Microvascular function was evaluated by response to adenosine and expressed as coronary flow velocity reserve. Mean values were compared.

RESULTS

Thirty patients were evaluated: 15 patients with ESRF (mean age 52.1 ± 9, male 73%) and 15 control patients (mean age 53.3 ± 13, male 60%). Comorbidity profile, aside from ESRF, was well matched. Baseline coronary blood flow was similar between groups (101.6 ± 10.3 vs. 103.4 ± 9.1 ml/min, P = 0.71), as was endothelial-dependent response to acetylcholine (159.1 ± 16.9 vs. 171.1 ± 16.8 ml/min, P = 0.41). Endothelial-independent response to glyceryl trinitrate was no different between groups (14.3 ± 3.1 vs. 13.1 ± 2.3%, P = 0.73. A significantly reduced coronary flow velocity reserve was observed in the ESRF cohort compared to controls (2.34 ± 0.4 vs. 3.05 ± 0.3, P = 0.003).

CONCLUSION

Patients with ESRF had preserved endothelial-dependent function however compared to controls, demonstrated significantly attenuated microvascular reserve. An impaired response to adenosine may not only represent a component of the pathophysiological milieu in patients with ESRF but may also provide a basis for the suboptimal diagnostic performance of vasodilatory stress in this population.

Cardiac Imaging for Coronary Heart Disease Risk Stratification in Chronic Kidney Disease

Chronic kidney disease (CKD), defined as dysfunction of the glomerular filtration apparatus, is an independent risk factor for the development of coronary artery disease (CAD). Patients with CKD are at a substantially higher risk of cardiovascular mortality compared with the age- and sex-adjusted general population with normal kidney function. The risk of CAD and mortality in patients with CKD is correlated with the degree of renal dysfunction including presence of microalbuminuria. A greater cardiovascular risk, albeit lower than for patients receiving dialysis, persists even after kidney transplantation. Congestive heart failure, commonly caused by CAD, also accounts for a significant portion of the cardiovascular-related events observed in CKD. The optimal strategy for the evaluation of CAD in patients with CKD, particularly before renal transplantation, remains a topic of contention spanning over several decades. Although the evaluation of coexisting cardiac disease in patients with CKD is desirable, severe renal dysfunction limits the use of radiographic and magnetic resonance contrast agents due to concerns regarding contrast-induced nephropathy and nephrogenic systemic sclerosis, respectively. In addition, many patients with CKD have extensive and premature (often medial) calcification disproportionate to the severity of obstructive CAD, thereby limiting the diagnostic value of computed tomography angiography. As such, echocardiography, non-contrast-enhanced magnetic resonance, nuclear myocardial perfusion, and metabolic imaging offer a variety of approaches to assess obstructive CAD and cardiomyopathy of advanced CKD without the need for nephrotoxic contrast agents.

Reduced myocardial blood flow reserve in kidney transplant candidates may hamper risk stratification

BACKGROUND

Vasodilator nuclear stress testing is frequently ordered for risk stratification prior to kidney transplantation. Since ⁸²Rb-positron emission tomography-computed tomography can measure myocardial blood flow (MBF), the response to vasodilator stress can be verified rendering the results of the scan more reliable.

METHODS

We reviewed the MBF response to dipyridamole infusion in 328 patients with end-stage kidney disease (ESKD) prior to transplant (188 hemodialysis-HD, 120 peritoneal dialysis-PD, and 20 pre-dialysis patients-CKD5) and in 100 controls with normal kidney function. A stress/rest MBF ratio ≥ 2 was considered an adequate response to dipyridamole. Coronary artery calcium (CAC) was measured on CT.

RESULTS

Inadequate MBF response was seen in 36%-HD, 21%-PD, 45%-CKD5 vs. 23%-controls (p = 0.006). Univariable predictors of poor MBF response in ESKD patients were age, diabetes mellitus, and CAC (all p < 0.03) while serum hemoglobin was borderline significant (p = 0.052). Multivariable predictors of a poor MBF response were age (p = 0.002) and lower serum hemoglobin (p = 0.014). Ischemia was identified in 8% of ESKD patients and 24% of controls (p < 0.001).

CONCLUSIONS

ESKD patients are less likely to respond appropriately to vasodilator stress compared to patients with normal renal function and had a lower incidence of ischemia despite a high pre-test probability of disease. Physicians performing vasodilator stress without MBF measurement should be aware of the high probability of a false negative response.

Myocardial perfusion reserve of kidney transplant patients is well preserved

Background

Chronic kidney disease (CKD) is associated with endothelial dysfunction and increased cardiovascular mortality. Endothelial dysfunction can be studied measuring myocardial perfusion reserve (MPR). MPR is the ratio of stress and rest myocardial perfusion (MP) and reflects the capacity of vascular bed to increase perfusion and microvascular responsiveness. In this pilot study, our aim was to assess MPR of 19 patients with kidney transplant (CKD stages 2–3) and of ten healthy controls with quantitative [¹⁵O]H₂O positron emission tomography (PET) method.

Results

Basal MP was statistically significantly higher at rest in the kidney transplant patients than in the healthy controls [1.3 (0.4) ml/min/g and 1.0 (0.2) ml/min/g, respectively, p = 0.0015]. After correction of basal MP by cardiac workload [MP_corr = basal MP/individual rate pressure product (RPP) × average RPP of the healthy controls], the difference between the groups disappeared [0.9 (0.2)  ml/min/g and 1.0 (0.3) ml/min/g, respectively, p = 0.55)]. There was no difference in stress MP between the kidney transplant patients and the healthy subjects [3.8 (1.0) ml/min/g and 4.0 (0.9) ml/min/g, respectively, p = 0.53]. Although MPR was reduced, MPR_corr (stress MP/basal MP_corr) did not differ between the kidney transplant patients and the healthy controls [4.1 (1.1) and 4.3 (1.6), respectively, p = 0.8].

Conclusions

MP during stress is preserved in kidney transplant patients with CKD stage 2–3. The reduced MPR appears to be explained by increased resting MP. This is likely linked with increased cardiac workload due to sympathetic overactivation in kidney transplant patients.

Coronary microvascular dysfunction: a key step in the development of uraemic cardiomyopathy?

The syndrome of uraemic cardiomyopathy, characterised by left ventricular hypertrophy, diffuse fibrosis and systolic and diastolic dysfunction, is common in chronic kidney disease and is associated with an increased risk of cardiovascular morbidity and mortality. The pathophysiological mechanisms leading to uraemic cardiomyopathy are not fully understood. We suggest that coronary microvascular dysfunction may be a key mediator in the development of uraemic cardiomyopathy, a phenomenon that is prevalent in other myocardial diseases that share phenotypical similarities with uraemic cardiomyopathy such as hypertrophic cardiomyopathy and heart failure with preserved ejection fraction. Here, we review the current understanding of uraemic cardiomyopathy, highlight different methods of assessing coronary microvascular function and evaluate the current evidence for coronary microvascular dysfunction in chronic kidney disease.

Non-invasive coronary physiology based on computational analysis of intracoronary transluminal attenuation gradient

Invasive procedure is a prerequisite for studying coronary physiology. We established the measurement of non-invasive physiological parameters including coronary blood flow (CBF), flow velocity, and microvascular resistance using coronary computed tomography angiography (CCTA). Vessel-specific CBF was derived from transluminal attenuation flow encoding (TAFE) and then tested using three separate datasets consisted of computational simulation, human perfusion CT, and human CCTA. TAFE-derived CBF correlated well with measured vessel-specific myocardial blood flow and CBF. TAFE-derived CBF per myocardial mass consistently decreased with the progressive severity of stenosis, and it was found to better to detect significant stenosis than transluminal attenuation gradient (TAG). With the addition of vessel anatomy, TAFE-derived CBF could calculate flow velocity and microvascular resistance. The results of non-invasively acquired parameters according to the severity of stenosis were similar to those obtained through invasive physiology studies. Our study demonstrated that non-invasive comprehensive coronary physiology parameters can be derived from CCTA without any pre-specified condition or performing complex heavy computational processes. Our findings are expected to expand the clinical coverage of CCTA and coronary physiology.

Coronary flow reserve is predictive of the risk of cardiovascular death regardless of chronic kidney disease stage

Microvascular rarefaction is found in experimental uremia, but data from patients with chronic kidney disease (CKD) are limited. We therefore quantified absolute myocardial blood flow and coronary flow reserve (the ratio of peak to resting flow) from myocardial perfusion positron emission tomography scans at a single institution. Individuals were classified into standard CKD categories based on the estimated glomerular filtration rate. Associations of coronary flow reserve with CKD stage and cardiovascular mortality were analyzed in models adjusted for cardiovascular risk factors. The coronary flow reserve was significantly associated with CKD stage, declining in early CKD, but it did not differ significantly among individuals with stage 4, 5, and dialysis-dependent CKD. Flow reserve with preserved kidney function was 2.01, 2.06 in stage 1 CKD, 1.91 in stage 2, 1.68 in stage 3, 1.54 in stage 4, 1.66 in stage 5, and 1.55 in dialysis-dependent CKD. Coronary flow reserve was significantly associated with cardiovascular mortality in adjusted models (hazard ratio 0.76, 95% confidence interval: 0.63-0.92 per tertile of coronary flow reserve) without evidence of effect modification by CKD. Thus, coronary flow reserve is strongly associated with cardiovascular risk regardless of CKD severity and is low in early stage CKD without further decrement in stage 5 or dialysis-dependent CKD. This suggests that CKD physiology rather than the effects of dialysis is the primary driver of microvascular disease. Our findings highlight the potential contribution of microvascular dysfunction to cardiovascular risk in CKD and the need to define mechanisms linking low coronary flow reserve to mortality.

Decreased renal AT1 receptor binding in rats after subtotal nephrectomy: PET study with [(18)F]FPyKYNE-losartan

Background

Significant renal mass reduction induced by 5/6 subtotal nephrectomy (Nx) is associated with a chain of events that culminates in hypertension and chronic kidney disease (CKD). Numerous studies have provided evidence for the role of angiotensin (Ang) II type 1 receptor (AT₁R) in the promotion and progression of the disease; however, conflicting results were reported on intrarenal AT₁R levels in CKD models.

Methods

Male Sprague-Dawley rats (n = 26) underwent Nx or sham operations. Animals were scanned at 8–10 weeks post-surgery with PET using the novel AT₁R radioligand [¹⁸F]FPyKYNE-losartan. Radioligand binding was quantified by kidney-to-blood ratio (KBR), standard uptake value (SUV), and distribution volume (DV). After sacrifice, plasma and kidney Ang II levels were measured. Western blot and ¹²⁵I-[Sar¹, Ile⁸]Ang II autoradiography were performed to assess AT₁R expression.

Results

At 8–10 weeks post-surgery, Nx rats developed hypertension, elevated plasma creatinine levels, left ventricle hypertrophy, increased myocardial blood flow (MBF), and reduced Ang II levels compared to shams. PET measurements displayed significant decrease in KBR (29 %), SUV (24 %), and DV (22 %) induced by Nx (p < 0.05), and these findings were confirmed by in vitro assays.

Conclusions

Reduced renal AT₁Rs in hypertensive rats measured with [¹⁸F]FPyKYNE-losartan PET at 8–10 weeks following Nx support further use of this non-invasive approach in longitudinal studies to better understand the AT₁R role in CKD progression.

Renal function and coronary microvascular dysfunction in women with symptoms/signs of ischemia

OBJECTIVES

Chronic kidney disease (CKD) is more prevalent among women and is associated with adverse cardiovascular events. Among women with symptoms and signs of ischemia enrolled in the Women's Ischemia Syndrome Evaluation (WISE), a relatively high mortality rate was observed in those with no obstructive coronary artery disease. Coronary microvascular dysfunction or reduced coronary flow reserve (CFR) was a strong and independent predictor of adverse outcomes. The objective of this analysis was to determine if renal function was associated with coronary microvascular dysfunction in women with signs and symptoms of ischemia.

METHODS

The WISE was a multicenter, prospective, cohort study of women undergoing coronary angiography for suspected ischemia. Among 198 women with additional measurements of CFR, we determined the estimated glomerular filtration rate (eGFR) with the CKD-EPI equation. We tested the association between eGFR and CFR with regression analysis.

RESULTS

The median eGFR was 89 ml/min. The eGFR correlated with CFR (r = 0.22; P = 0.002). This association persisted even after covariate adjustment. Each 10-unit decrease in eGFR was associated with a 0.04-unit decrease in CFR (P = 0.04).There was a strong interaction between eGFR and age (P = 0.006): in those ≥60 years old, GFR was strongly correlated with CFR (r = 0.55; P<0.0001). No significant correlation was noted in those <60 years old.

CONCLUSIONS

Reduced renal function was significantly associated with lower CFR in women with symptoms and signs of ischemia. Coronary microvascular dysfunction warrants additional study as a mechanism contributing to increased risk of cardiovascular events in CKD.

Myocardial Ischemia Assessment in Chronic Kidney Disease: Challenges and Pitfalls

Coronary artery disease is the leading cause of mortality and morbidity in the chronic kidney disease (CKD) population and often presents with atypical symptoms. Current diagnostic investigations of myocardial ischemia in CKD lack sensitivity and specificity or may have adverse effects. We present a case vignette and explore the challenges of diagnostic myocardial stress investigation in patients with CKD.

Is left ventricular hypertrophy a modifiable risk factor in end-stage renal disease

PURPOSE OF REVIEW

Left ventricular hypertrophy (LVH) is common in end-stage renal disease (ESRD) and has been advocated as a therapeutic target. We review the considerations for targeting LVH as a modifiable risk factor in ESRD.

RECENT FINDINGS

Pathologic myocardial changes underlying LVH provide an ideal substrate for the spread of arrhythmia and may be key contributors to the occurrence of sudden death in ESRD. LVH is present in 68-89% of incident hemodialysis patients and is frequently progressive, although regression is observed in a minority of patients. Higher degrees of baseline LVH, as well as greater increases in left ventricular mass index over time, are associated with decreased survival, but whether these associations are causal remains uncertain. Several interventions, including angiotensin blockade and frequent dialysis, can reduce the left ventricular mass index, but whether this is associated with improved survival has not been definitively demonstrated.

SUMMARY

LVH is a highly prevalent and reversible risk factor, which holds promise as a novel therapeutic target in ESRD. Interventional trials are needed to provide additional evidence that LVH regression improves survival before prevention and reversal of LVH can be definitively adopted as a therapeutic paradigm in ESRD.

Impact of chronic kidney disease on myocardial blood flow regulation in dogs

BACKGROUND/AIMS

Chronic kidney disease (CKD) increases cardiovascular risk possibly due to coronary microvessel dysfunction and impaired myocardial flow reserve. This study investigated the effects of CKD on the regulation and transmural distribution of myocardial blood flow along with oxygen demand during intravenous dobutamine-induced increases in cardiac work.

METHODS

CKD was produced in dogs by a two-stage subtotal nephrectomy (kidney ablation-infarction model). Serum creatinine and blood urea nitrogen were evaluated during the development of CKD along with systemic blood pressure (tail-cuff plethysmography). After 5 weeks, the CKD dogs were staged according to the International Renal Interest Society staging system; all dogs were anesthetized and surgically prepared for blood flow studies. Data analyses were performed between sham control (CTR) and stage 1 and 2 CKD dogs.

RESULTS

At baseline, myocardial blood flow and diastolic aortic pressure were similar for all groups. During intravenous dobutamine, myocardial blood flow was markedly higher than CTR even though hematocrit levels declined with the severity of CKD. In the CTR dogs, myocardial blood flow increased in direct relation to cardiac work. However, in the CKD dogs (stage 1 and 2), maximum blood flow was achieved with low-dose dobutamine, indicating that coronary autoregulation is more readily exhausted with minimal increases in cardiac work during CKD.

CONCLUSION

We report that CKD markedly impairs coronary vascular reserve and myocardial blood flow regulation which could contribute to greater cardiovascular risk and poor clinical outcomes in CKD patients.

Relation of albuminuria to coronary microvascular function in patients with chronic kidney disease

The relation between albuminuria and coronary microvascular function in patients with chronic kidney disease (CKD) has not been fully investigated. Therefore, we sought to assess whether albuminuria is associated with coronary flow velocity reserve (CFVR) impairment in patients with CKD. Coronary flow study was prospectively performed in 175 patients with CKD. CFVR of the left anterior descending artery was measured to evaluate coronary microvascular function using transthoracic echocardiography. We divided the patients into 5 groups according to the stages of CKD and analyzed the effect of albuminuria. CFVR gradually decreased with an increase in CKD stages. CFVR in patients with albuminuria was lower than those without albuminuria. In groups with CKD stages 2 and 3, the patients with albuminuria showed lower CFVR than those without albuminuria. Multiple logistic regression analysis revealed that albuminuria, age, and gender were independently associated with CFVR impairment. Of these factors, albuminuria was the most powerful predictor with the risk ratio of 12.4 for CFVR impairment. In conclusion, the more the CKD stages progressed, the more severe CFVR was impaired. Albuminuria was associated with CFVR impairment in patients with CKD; even in mild-to-moderate CKD, patients with albuminuria showed further reduced coronary vasodilator capacity.

A reduction of coronary flow reserve is associated with chronic kidney disease and long-term cardio-cerebrovascular events in patients with non-obstructive coronary artery disease and vasospasm

BACKGROUND

Coronary flow reserve (CFR) provides essential information about the coronary microvasculature. Chronic kidney disease (CKD) is a risk factor for cardio-cerebrovascular diseases. We hypothesized that low CFR is associated with CKD and long-term cardio-cerebrovascular events in the patients without obstructive coronary artery diseases and vasospasm.

METHOD AND RESULTS

In this study, 73 patients suspected with coronary artery disease but had no epicardial coronary stenosis and vasospasm were enrolled. There were 13 CKD patients and CFR was measured using the Doppler flow wire methods in the left anterior descending artery. CFR was significantly lower in CKD group than non-CKD group (3.13 ± 0.6 vs. 4.00 ± 1.1, P = 0.007). From multivariate logistic regression analysis, the independent factor associated with the presence of CKD was only CFR (odds ratio 3.85, 95% confidence interval 1.27-11.70, P = 0.017). In the patients with low CFR (≤ 2.8), cardio-cerebrovascular events were more common than those with normal CFR (CFR > 2.8). Besides, in the patients who had both low CFR and CKD, long-term cardio-cerebrovascular events were more likely to occur than those with normal CFR or non-CKD.

CONCLUSIONS

Our data suggest that low CFR is associated with CKD and cardio-cerebrovascular events in the patients without coronary stenosis and vasospasm.

Prognostic value of myocardial perfusion imaging for cardiovascular events among asymptomatic Japanese patients with type 2 diabetes and mild renal dysfunction

BACKGROUND

Diabetes is frequently accompanied by chronic kidney disease, and both diabetes and chronic kidney disease are risk factors for ischemic heart disease; however, cardiac risk among diabetic patients with mild renal dysfunction has not been analyzed in detail. The present study investigates how myocardial perfusion imaging (MPI) contributes to the risk stratification of diabetic patients with mild renal dysfunction who are asymptomatic for cardiac diseases.

PATIENTS AND METHODS

Among 513 asymptomatic patients with type 2 diabetes in the Japanese Assessment of Cardiac Events and Survival Study 2 (J-ACCESS) database, we selected 286 with estimated glomerular filtration rates (eGFR) of at least 45 ml/min/1.73 m and assigned them to groups on the basis of eGFR of at least 60 without (group A, n=66) or with microalbuminuria or eGFR 45 to less than 60 (group B, n=220). The 3-year incidence of cardiac events and the value of MPI were evaluated.

RESULTS

Cardiac events developed in 1.52 and 4.55% of patients in groups A and B, respectively. Event-free survival did not differ according to summed stress scores in group A but was significantly lower among patients with summed stress scores of at least 9 in group B.

CONCLUSION

Routine MPI might be useful for stratifying risk among diabetic patients with mild renal dysfunction but is unnecessary for those with good renal function.

Impaired global myocardial flow dynamics despite normal left ventricular function and regional perfusion in chronic kidney disease: a quantitative analysis of clinical 82Rb PET/CT studies

Impaired global myocardial flow reserve (MFR) may be associated with increased risk for cardiac events and coronary artery disease progression. Chronic kidney disease (CKD) is also considered a risk factor for cardiovascular disease. We sought to investigate the effect of CKD on the myocardial microcirculation in patients referred for clinical (82)Rb PET/CT, who had normal left ventricular (LV) function and no flow-limiting coronary artery disease.

METHODS

Estimated glomerular filtration rate (eGFR) was available for 230 patients who had undergone rest and pharmacologic stress (82)Rb PET/CT for suspected coronary artery disease. CKD was defined as an eGFR less than 60 mL/min/1.73 m(2). After patients with hemodialysis, a renal transplant, abnormal regional perfusion (summed stress score > 4), or reduced LV function (LV ejection fraction < 45%) were excluded, 40 CKD patients remained. Those were compared with a control group without CKD, which was matched for age, sex, coronary risk factors, and systemic hemodynamics (n = 42). List-mode acquisition of PET enabled quantification of myocardial blood flow (MBF) and MFR using a previously validated retention model with correction for (82)Rb extraction. Rest MBF was normalized to rate-pressure product.

RESULTS

Mean eGFR in the CKD group was reduced (44 ± 14 vs. 99 ± 28 mL/min/1.73 m(2); P < 0.0001), and creatinine was significantly elevated, compared with controls (1.9 ± 1.1 vs. 0.8 ± 0.2 mg/dL; P < 0.0001). MFR was significantly reduced in CKD (2.2 ± 1.0 vs. 3.0 ± 1.2 for controls; P = 0.027). This reduction was mainly due to increased rest MBF (1.1 ± 0.4 in CKD vs. 0.8 ± 0.2 mL/min/g in controls; P = 0.007). Stress myocardial flow was comparable between both groups (2.3 ± 0.9 vs. 2.3 ± 0.8 mL/min/g; P = 0.08). Overall, MFR was significantly correlated with eGFR (r = 0.41; P = 0.0005). Stress MBF did not correlate with eGFR (r = 0.002; P = 0.45), but rest MBF showed an inverse correlation (r = -0.49; P < 0.0001). Rest MBF was also inversely correlated with hemoglobin (r = -0.28; P = 0.014), but only eGFR was an independent correlate at multivariate analysis.

CONCLUSION

MFR is impaired in patients with renal insufficiency with normal regional perfusion and LV function, mostly because of elevated rest flow. Absolute quantification of flow may be useful to identify microvascular dysfunction as a precursor of clinically overt coronary disease in this specific risk group.

CKD and coronary collateral supply in individuals undergoing coronary angiography after myocardial infarction

BACKGROUND AND OBJECTIVES

CKD patients have high mortality risk after myocardial infarction (MI). An adequate supply of coronary collaterals to the culprit vessel responsible for MI is associated with reduced risks of death and complications. Whether a diminished supply of collaterals contributes to the high risk in CKD patients is uncertain.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Quantitative coronary angiography was performed in a consecutive series of individuals with (n=58) and without (n=165) CKD (estimated GFR <60 ml/min per 1.73 m(2)) who underwent coronary angiography at the time of MI. Collateral supply was analyzed and candidate predictors were assessed in patient-level and individual artery-level models using logistic regression and ordered categorical regression, respectively.

RESULTS

There were no significant differences in collateral supply among 58 CKD patients and 165 individuals with preserved renal function. Culprit artery collaterals were present in 25.0% of CKD patients compared with 27.2% of individuals with preserved renal function (P=0.76). The odds of having an adequate supply of culprit vessel collaterals were also not significantly different in individuals with and without CKD, respectively. CKD patients were 2.22-fold more likely to have visible collaterals to the nonculprit vessels in unadjusted analyses. The difference was not significant after correction for percent stenosis and comorbid factors.

CONCLUSIONS

Our results do not support an independent association between CKD and diminished collateral supply to either the culprit or nonculprit vessels in MI. Additional studies are warranted to better define associations between myocardial capillary supply, collateral supply, and the full range of human CKD.

Coronary microvascular function in early chronic kidney disease

BACKGROUND

coronary microvascular dysfunction may underlie the high cardiovascular risk associated with chronic kidney disease (CKD), but the effects of CKD on coronary microvasculature function remain uncertain.

METHODS AND RESULTS

we assessed myocardial blood flow changes in mild-to-moderate CKD and analyzed the association between creatinine clearance (CrCl) and peak myocardial blood flow and coronary flow reserve (CFR) measured as the ratio of stress to rest perfusion at baseline and at 1 year in 435 nondiabetic individuals who underwent quantitative rest and pharmacological stress positron emission tomography imaging. At baseline, CFR was significantly associated with CrCl (β per 10 mL/min increase, 0.07; P=0.001). Factors such as age and blood pressure accounted for this association, and it was not significant in adjusted analyses (β=-0.02, P=0.53). Peak flow was not associated with CrCl in either crude or adjusted analyses (β per 10 mL/min=-0.02 mL/min per g, P=0.29). Although change in peak flow at 1 year was similar in patients with and without CKD, CrCl was a strong and independent predictor of a higher rate of change in CFR, with a loss of 0.11 CFR units/y (95% confidence interval, 0.01 to 0.20) for each 10 mL/min drop in CrCl (P=0.03).

CONCLUSIONS

these findings demonstrate that mild-to-moderate CKD is not independently associated with a reduction in peak myocardial flow or CFR and suggests that microvascular changes are unlikely to explain the high cardiovascular mortality in mild to moderate CKD. Loss of CFR, however, may accelerate in mild to moderate CKD. Further studies are needed to determine whether these changes lead to more significant reductions that may reduce peak flows and CFR and contribute to cardiovascular risk in more severe CKD.