Faculty Bibliography

PURPOSE OF REVIEW:This review article focuses on the most significant cardiovascular complications in dialysis patients [sudden cardiac death (SCD), acute coronary syndromes, heart failure, and atrial fibrillation]. RECENT FINDINGS:Current and ongoing research aims to quantify the rate and pattern of significant arrhythmia in dialysis patients and to determine the predominant mechanism of SCD. Preliminary findings from these studies suggest a high rate of atrial fibrillation and that bradycardia and asystole may be more frequent than ventricular arrhythmia as a cause of sudden death. A recently published matched cohort study in dialysis patients who received a defibrillator for primary prevention showed that there was no significant difference in mortality rates between defibrillator-treated patients and propensity-matched controls. Two randomized controlled trials are currently recruiting participants and will hopefully answer the question of whether implantable or wearable cardioverter defibrillators can prevent SCD. An observational study using United States Renal Data System data demonstrated how difficult it is to keep hemodialysis patients on warfarin, as more than two-thirds discontinued the drug during the first year. The ISCHEMIA-CKD trial may provide answers about the optimal strategy for the treatment of atherosclerotic coronary disease in patients with advanced chronic kidney disease. SUMMARY:The article reviews the diagnosis of acute coronary syndromes in dialysis patients, current literature on myocardial revascularization, and data on fatal and nonfatal cardiac arrhythmia. The new classification of heart failure in end-stage renal disease is reviewed. Finally, available cohort studies on warfarin for stroke prevention in dialysis patients with atrial fibrillation are reviewed.

Coronary atherosclerotic disease is highly prevalent in chronic kidney disease (CKD). Although revascularization improves outcomes, procedural risks are increased in CKD, and unbiased data comparing coronary artery bypass grafting (CABG) and percutaneous intervention (PCI) in CKD are sparse. To compare outcomes of CABG and PCI in stage 3 to 5 CKD, we identified randomized trials comparing these procedures. Investigators were contacted to obtain individual, patient-level data. Ten of 27 trials meeting inclusion criteria provided data. These trials enrolled 3993 patients encompassing 526 patients with stage 3 to 5 CKD of whom 137 were stage 3b-5 CKD. Among individuals with stage 3 to 5 CKD, mortality through 5 years was not different after CABG compared with PCI (hazard ratio [HR] 0.99, 95% confidence interval [CI] 0.67-1.46) or stage 3b-5 CKD (HR 1.29, CI 0.68-2.46). However, CKD modified the impact on survival free of myocardial infarction: it was not different between CABG and PCI for individuals with preserved kidney function (HR 0.97, CI 0.80-1.17), but was significantly lower after CABG in stage 3-5 CKD (HR 0.49, CI 0.29-0.82) and stage 3b-5 CKD (HR 0.23, CI 0.09-0.58). Repeat revascularization was reduced after CABG compared with PCI regardless, of baseline kidney function. Results were limited by unavailability of data from several trials and paucity of enrolled patients with stage 4-5 CKD. Thus, our patient-level meta-analysis of individuals with CKD randomized to CABG versus PCI suggests that CABG significantly reduces the risk of subsequent myocardial infarction and revascularization without affecting survival in these patients.

Capillary rarefaction of the coronary microcirculation is a consistent phenotype in patients with dialysis-dependent ESRD (dd-ESRD) and may help explain their excess mortality. Global coronary flow reserve (CFR) assessed by positron emission tomography (PET) is a noninvasive, quantitative marker of myocardial perfusion and ischemia that integrates the hemodynamic effects of epicardial stenosis, diffuse atherosclerosis, and microvascular dysfunction. We tested whether global CFR provides risk stratification in patients with dd-ESRD. Consecutive patients with dd-ESRD clinically referred for myocardial perfusion PET imaging were retrospectively included, excluding patients with prior renal transplantation. Per-patient CFR was calculated as the ratio of stress to rest absolute myocardial blood flow. Multivariable Cox proportional hazards models, including age, overt cardiovascular disease, and myocardial scar/ischemia burden, were used to assess the independent association of global CFR with all-cause and cardiovascular mortality. The incremental value of global CFR was assessed with relative integrated discrimination index and net reclassification improvement. In 168 patients included, median global CFR was 1.4 (interquartile range, 1.2-1.8). During follow-up (median of 3 years), 36 patients died, including 21 cardiovascular deaths. Log-transformed global CFR independently associated with all-cause mortality (hazard ratio, 0.01 per 0.5-unit increase; 95% confidence interval, <0.01 to 0.14; P<0.001) and cardiovascular mortality (hazard ratio, 0.01 per 0.5-unit increase; 95% confidence interval, <0.01 to 0.15; P=0.002). For all-cause mortality, addition of global CFR resulted in risk reclassification in 27% of patients. Thus, global CFR may provide independent and incremental risk stratification for all-cause and cardiovascular mortality in patients with dd-ESRD.

BACKGROUND:Dialysis patients have high rates of cardiovascular morbidity and mortality, but data on arrhythmia burden, arrhythmia type, arrhythmia triggers, and the identity of terminal arrhythmias have historically been limited by an inability to monitor heart rhythm for prolonged periods. OBJECTIVES/OBJECTIVE:To investigate arrhythmia and its association with sudden death in dialysis-dependent ESRD, describe the potential for implantable devices to advance study of dialysis physiology, review the ethical implications of using implantable devices in clinical studies, and report on the protocol and baseline results of the Monitoring in Dialysis Study (MiD). DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS/METHODS:In this multicenter, interventional-observational, prospective cohort study, we placed implantable loop recorders in patients undergoing long-term hemodialysis. The proportion of patients experiencing clinically significant arrhythmias was the primary endpoint. For 6 months, we captured detailed data on the primary endpoint, symptomatic arrhythmias, other electrocardiographic variables, dialysis prescription, electrolytes, dialysis-related variables, and vital signs. We collected additional electrocardiographic data for up to 1 year. RESULTS:Overall, 66 patients underwent implantation in sites in the United States and India. Diabetes was present in 63.6% of patients, 12.1% were age ≥70 years, 69.7% were men, and 53.0% were black. Primary and secondary endpoint data are expected in 2016. CONCLUSIONS:Cardiac arrhythmia is an important contributor to cardiovascular morbidity and mortality in dialysis patients, but available technology has previously limited the ability to estimate its true burden and triggers and to define terminal rhythms in sudden death. Use of implantable technology in observational studies raises complex issues but may greatly expand understanding of dialysis physiology. The use of implantable loop recorders in MiD is among the first examples of such a trial, and the results are expected to provide novel insights into the nature of arrhythmia in hemodialysis patients.

BACKGROUND:The cause of death in patients with chronic kidney disease (CKD) varies with CKD severity, but variation has not been quantified. STUDY DESIGN/METHODS:Retrospective analysis of prospective randomized clinical trial. SETTING & PARTICIPANTS/METHODS:We analyzed 4,038 individuals with anemia and diabetic CKD from TREAT, a randomized trial comparing darbepoetin alfa and placebo. PREDICTORS/METHODS:Baseline estimated glomerular filtration rate (eGFR) and protein-creatinine ratio (PCR). OUTCOMES/RESULTS:Cause of death as adjudicated by a blinded committee. RESULTS:Median eGFR and PCR ranged from 20.6 mL/min/1.73 m(2) and 4.1 g/g in quartile 1 (Q1) to 47.0 mL/min/1.73 m(2) and 0.1 g/g in Q4 (P<0.01). Of 806 deaths, 441, 298, and 67 were due to cardiovascular (CV), non-CV, and unknown causes, respectively. Cumulative CV mortality at 3 years was higher with lower eGFR (Q1, 15.5%; Q2, 11.1%; Q3, 11.2%; Q4, 10.3%; P<0.001) or higher PCR (Q1, 15.2%; Q2, 12.3%; Q3, 11.7%; Q4, 9.0%; P<0.001). Similarly, non-CV mortality was higher with lower eGFR (Q1, 12.7%; Q2, 8.4%; Q3, 6.7%; Q4, 6.1%; P<0.001) or higher PCR (Q1, 10.3%; Q2, 7.9%; Q3, 9.4%; Q4, 6.4%; P=0.01). Sudden death was 1.7-fold higher with lower eGFR (P=0.04) and 2.1-fold higher with higher PCR (P<0.001). Infection-related mortality was 3.3-fold higher in the lowest eGFR quartile (P<0.001) and 2.8-fold higher in the highest PCR quartile (P<0.02). The overall proportion of CV and non-CV deaths was not significantly different across eGFR or PCR quartiles. LIMITATIONS/CONCLUSIONS:Results may not be generalizable to nondiabetic CKD or diabetic CKD in the absence of anemia. Measured GFR was not available. CONCLUSIONS:In diabetic CKD, both lower baseline GFR and higher PCR are associated with higher CV and non-CV mortality rates, particularly from sudden death and infection. Efforts to improve outcomes should focus on CV disease and early diagnosis and treatment of infection.

The association between chronic kidney disease (CKD) and cardiovascular disease (CVD) is well established, and there is mounting evidence of interorgan cross talk that may accelerate pathologic processes and the progression of organ dysfunction in both systems. This process, termed cardiorenal syndrome (CRS) by the Acute Dialysis Quality Initiative, is considered a major health problem: patients with CKD and CVD are at much higher risk of mortality than patients with either condition alone. To date, the majority of CRS research has focused on neurohormonal mechanisms and hemodynamic alterations. However, mounting evidence suggests that abnormalities in the normal pathophysiology of the bone-mineral axis, iron, and erythropoietin play a role in accelerating CKD and CVD. The goal of this article is to review the role and interrelated effects of the bone-mineral axis and anemia in the pathogenesis of chronic CRS.

Trials raising concerns about erythropoiesis-stimulating agents, revisions to their labeling, and changes to practice guidelines and dialysis payment systems have provided strong stimuli to decrease erythropoiesis-stimulating agent use and increase intravenous iron administration in recent years. These factors have been associated with a rise in iron utilization, particularly among hemodialysis patients, and an unprecedented increase in serum ferritin concentrations. The mean serum ferritin concentration among United States dialysis patients in 2013 exceeded 800 ng/ml, with 18% of patients exceeding 1200 ng/ml. Although these changes are broad based, the wisdom of these practices is uncertain. Herein, we examine influences on and trends in intravenous iron utilization and assess the clinical trial, epidemiologic, and experimental evidence relevant to its safety and efficacy in the setting of maintenance dialysis. These data suggest a potential for harm from increasing use of parenteral iron in dialysis-dependent patients. In the absence of well powered, randomized clinical trials, available evidence will remain inadequate for making reliable conclusions about the effect of a ubiquitous therapy on mortality or other outcomes of importance to dialysis patients. Nephrology stakeholders have an urgent obligation to initiate well designed investigations of intravenous iron in order to ensure the safety of the dialysis population.