Impact of Frequent Nocturnal Hemodialysis on Myocardial Mechanics and Cardiomyocyte Gene Expression

Left atrial strain: A novel "biomarker" for chronic kidney disease patients?

Cardiovascular disease and chronic kidney disease are frequently inter-connected and this association leads to an exponential growth of cardiovascular risk. This risk is currently underestimated by the existing algorithms and there is a constant need for new markers to predict adverse outcomes in this special population. In general population left atrial strain has emerged as an important tool for both the diagnosis and prognostic stratification, but data regarding its role in chronic kidney disease patients is scarce. The purpose of this review is to summarize the current evidence regarding this matter. Left atrial size and function mirror the duration and severity of increased left ventricular filling pressures. Increased left atrial volume index and impaired left atrial strain parameters are independent predictors for adverse cardiovascular events. Left atrial strain is impaired before changes in volume appear, thus being able to predict both diastolic and systolic function in chronic kidney disease patients. Finally, left atrial strain can identify renal patients with impaired exercise capacity and this could have clinical applications in the rehabilitation of this patients.

Cardiovascular Benefits of Extended-Time Nocturnal Hemodialysis

Hemodialysis (HD) remains the most utilized treatment for End-Stage Kidney Disease (ESKD) globally, mainly as conventional HD administered in 4 h sessions thrice weekly. Despite advances in HD delivery, patients with ESKD carry a heavy cardiovascular morbidity and mortality burden. This is associated with cardiac remodeling, left ventricular hypertrophy (LVH), myocardial stunning, hypertension, decreased heart rate variability, sleep apnea, coronary calcification and endothelial dysfunction. Therefore, intensive HD regimens closer to renal physiology were developed. They include longer, more frequent dialysis or both. Among them, Nocturnal Hemodialysis (NHD), carried out at night while asleep, provides efficient dialysis without excessive interference with daily activities. This regimen is closer to the physiology of the native kidneys. By providing increased clearance of small and middle molecular weight molecules, NHD can ameliorate uremic symptoms, control hyperphosphatemia and improve quality of life by allowing a liberal diet and free time during the day. Lastly, it improves reproductive biology leading to successful pregnancies. Conversion from conventional to NHD is followed by improved blood pressure control with fewer medications, regression of LVH, improved LV function, improved sleep apnea, and stabilization of coronary calcifications. These beneficial effects have been associated, among others, with better extracellular fluid volume control, improved endothelial- dependent vasodilation, decreased total peripheral resistance, decreased plasma norepinephrine levels and restoration of heart rate variability. Some of these effects represent improvements in outcomes used as surrogates of hard outcomes related to cardiovascular morbidity and mortality. In this review, we consider the cardiovascular effects of NHD.

Evaluation of one year of frequent dialysis on fluid load and body composition using calf bioimpedance technique

OBJECTIVE

The primary aim of this study was to evaluate the effect of increased frequency of dialysis (FHD) on change in fluid status and body composition using segmental bioimpedance.

APPROACH

Twelve stable HD patients were switched from 3 times/week to 6 times/week HD (FHD). Systolic blood pressure (SBP), body mass and body mass index (BMI) were measured pre- and post-HD. Calf resistance (R ₅) at 5 kHz was measured using a multifrequency bioimpedance device (Hydra 4200). Calf resistivity (ρ  =  R ₅ * area/length), normalized resistivity (CNR  =  ρ/BMI) and calf extracellular volume (cECV) were calculated. Fat mass was measured by Futrex body composition analyzers (Futrex 6100, Futrex Tech, Inc.). All measurements were performed at baseline (BL) and monthly for up to one year.

MAIN RESULTS

Nine patients completed one year of FHD. Compared to BL, body weight and cECV decreased, and CNR increased significantly by the first month but did not change thereafter. SBP pre-HD decreased significantly by the end of the first month with further reduction until month 12. Additionally, antihypertensive medication decreased significantly from baseline by month 4 and remained stable from month 6 throughout the rest of the study. The post-HD CNR in five of nine patients reached the range of normal (>18.5 10^-2 * Ohm * m³ kg^-1 for males and  >19.1 10^-2 * Ohm * m³ kg^-1 for females) after 1 year FHD. In patients who returned to 3 times/week dialysis, CNR decreased significantly in the first week, and this was associated with increases in body weight and SBP.

SIGNIFICANCE

Reduction of fluid overload with no alteration of body composition was observed in this study. Accordingly, improving fluid status was confirmed by reducing BP and use of antihypertensive drugs together with increase in CNR. Measurement of fluid status by CNR in hemodialysis patients is a new method to quantitatively assess hydration potentially creating a target for volume of fluid removal.

Extended-hours hemodialysis is associated with lower mortality risk in patients with end-stage renal disease

Extended-hours hemodialysis offers substantially longer treatment time compared to conventional hemodialysis schedules and is associated with improved fluid and electrolyte control and favorable cardiac remodeling. However, whether extended-hours hemodialysis improves survival remains unclear. Therefore, we determined the association between extended-hours compared to conventional hemodialysis and the risk of all-cause mortality in a nationally representative cohort of patients initiating maintenance dialysis in the United States from 2007 to 2011. Survival analyses using causal inference modeling with marginal structural models were performed to compare mortality risk among 1206 individuals undergoing thrice weekly extended-hours hemodialysis or 111,707 patients receiving conventional hemodialysis treatments. The average treatment time per session for extended-hours hemodialysis was 399 minutes compared to 211 minutes for conventional therapy. The crude mortality rate with extended-hours hemodialysis was 6.4 deaths per 100 patient-years compared with 14.7 deaths per 100 patient-years for conventional hemodialysis. In the primary analysis, patients treated with extended-hours hemodialysis had a 33% lower adjusted risk of death compared to those who were treated with a conventional regimen (95% confidence interval: 7% to 51%). Additional analyses accounting for analytical assumptions regarding exposure and outcome, facility-level confounders, and prior modality history were similar. Thus, in this large nationally representative cohort, treatment with extended-hours hemodialysis was associated with a lower risk for mortality compared to treatment with conventional in-center therapy. Adequately powered randomized clinical trials comparing extended-hours to conventional hemodialysis are required to confirm these findings.

Intensive Hemodialysis Preserved Cardiac injury

Cardiac injury triggers cellular responses involving both cardiomyocytes and nonmuscle cells to process cardiac structural remodeling. End-stage renal disease (ESRD), despite conventional dialysis, is associated with adverse cardiac remodeling and increased cardiovascular events. Intensification of hemodialysis with nocturnal home hemodialysis (NHD; five sessions per week; 6-8 hours per treatment) was associated with regression of left ventricular hypertrophy and downregulation of genes in apoptosis and fibrosis. In this pilot study, we hypothesize that NHD achieves its cardiac effects in part through attenuation of innate immune activation resulting in amelioration of cardiomyocytes apoptosis and fibrosis. Eight patients (4M:4F; age, 59 ± 9 years) with ESRD were studied. Half of the cohort was converted to NHD, whereas the rest of the patients were maintained on conventional hemodialysis (CHD). At baseline, CHD was associated with an increase in cardiomyocyte apoptosis detected by flow cytometry using Annexin V (mean fluorescence index in CHD and in normal control is 1.00 ± 0.05 vs. 0.66 ± 0.01, p < 0.05). After conversion to NHD, cardiomyocyte apoptosis was reduced compared with baseline CHD situation (p < 0.05) and approached that of normal control (0.59 ± 0.09 vs. 0.66 ± 0.01, p > 0.05). The CHD serum was associated with a coordinated augmentation innate immunity pathway, significantly increasing myeloid differentiation factor-88 and interleukin-1 receptor-associated kinase-4; NHD was able to reduce their levels. Heat shock protein 60 was augmented during CHD condition and fell after NHD. In addition, CHD increased fibroblast proliferation and myofibroblast transformation. Uremia is associated with activation of common innate immune signaling pathways leading to fibrosis and apoptosis. Amelioration of uremic clearance by NHD may attenuate this pathological signaling cascade.

Assessment of Left Ventricular Dissipative Energy Loss by Vector Flow Mapping in Patients With End-Stage Renal Disease

OBJECTIVES

Dissipative energy loss derived from vector flow mapping represents the viscous dissipation of turbulent blood flow. We aimed to determine the left ventricular (LV) energy loss in patients with end-stage renal disease (ESRD).

METHODS

Patients with ESRD and a preserved LV ejection fraction, who consisted of a group receiving peritoneal dialysis, a group receiving hemodialysis, and a group receiving preparation for dialysis initiation, were examined by echocardiography; a group of healthy control participants were examined as well. Vector flow mapping analysis was then performed from the apical 4-chamber view to calculate the energy loss during diastole and systole in the left ventricle.

RESULTS

Conventional transthoracic echocardiography and LV energy loss calculations were successfully performed in 63 cases and 50 controls. The patients with ESRD had significantly higher diastolic energy loss [median (interquartile range), 71.73 (46.08-106.75) versus 23.32 (17.17-29.26) mW/m; P < .001] and higher systolic energy loss [25.28 (19.03-33.93) versus 12.52 (9.35-16.47) mW/m; P < .001]. A significant difference in diastolic energy loss between the peritoneal dialysis and preparation groups was found [54.92 (39.28-89.94) versus 84.82 (62.58-171.4) mW/m; P = .04]. In patients with ESRD, the log-transformed diastolic energy loss had a significant association with the peak early diastolic transmitral flow velocity (P = .011), peak early diastolic transmitral flow velocity-to-peak early diastolic mitral annular flow velocity ratio (P = .001), LV mass index (P = .017), and heart rate (P = .003).

CONCLUSIONS

Impaired blood flow efficiency was detected in patients with ESRD by using dissipative energy loss derived from vector flow mapping. The energy loss value could be a novel parameter for evaluating the ventricular workload of uremic hearts in terms of fluid mechanics.

Therapeutic applications of circadian rhythms for the cardiovascular system

The cardiovascular system exhibits dramatic time-of-day dependent rhythms, for example the diurnal variation of heart rate, blood pressure, and timing of onset of adverse cardiovascular events such as heart attack and sudden cardiac death. Over the past decade, the circadian clock mechanism has emerged as a crucial factor regulating these daily fluctuations. Most recently, these studies have led to a growing clinical appreciation that targeting circadian biology offers a novel therapeutic approach toward cardiovascular (and other) diseases. Here we describe leading-edge therapeutic applications of circadian biology including (1) timing of therapy to maximize efficacy in treating heart disease (chronotherapy); (2) novel biomarkers discovered by testing for genomic, proteomic, metabolomic, or other factors at different times of day and night (chronobiomarkers); and (3) novel pharmacologic compounds that target the circadian mechanism with potential clinical applications (new chronobiology drugs). Cardiovascular disease remains a leading cause of death worldwide and new approaches in the management and treatment of heart disease are clearly warranted and can benefit patients clinically.

Hemodialysis-associated cardiomyopathy: a newly defined disease entity

Cardiovascular disease is the most common cause of the greatly elevated rates of mortality characteristic of patients undergoing maintenance hemodialysis. This article is an attempt to describe the complex and evolving features of cardiac disease routinely encountered in HD patients. Furthermore, by trying to appreciate the pathophysiological drivers, and the crucial interaction with the HD treatment itself, this article seeks to define cardiac disease in this setting (HD-associated cardiomyopathy) as a unique and complex entity. By understanding the phenotype and basis of HD-associated cardiomyopathy, we can develop an evolved understanding of the dominant processes involved in its development and offer up dialysis-based interventions specifically designed to mitigate the cumulative ischemic insults consequent to conventional HD treatment. This article explores the justification of this approach and recent evidence of its efficacy.

The association between renal impairment and cardiac structure and function in patients with acute myocardial infarction

BACKGROUND

Renal dysfunction in patients with acute myocardial infarction (MI) is an important predictor of short- and long-term outcome. Cardiac abnormalities dominated by left ventricular (LV) hypertrophy are common in patients with chronic renal dysfunction. However, limited data exists on the association between LV systolic- and diastolic function assessed by comprehensive echocardiography and renal dysfunction in contemporary unselected patients with acute MI.

METHODS

We prospectively included 1054 patients with acute MI (mean age 63 years, 73% male) and performed echocardiographic assessment of systolic and diastolic function within 48 hours of admission as well as estimated glomerular filtration rate (eGFR).

RESULTS

Reduced eGFR was significantly associated with LV mass, LV ejection fraction, LV global strain (GLS) and E/e' ratio. After multivariable adjustment, E/e' ratio (P = .0096) remained the only echocardiographic measure independently associated with decreasing eGFR. During follow-up a total of 113 patients (10.7%) patients experienced the composite endpoint of all-cause mortality or hospitalization for heart failure. An eGFR <60 mL/min per 1.73 m(2) was significantly associated with outcome (HR, 1.71; 95% CI, 1.12-2.62; P = .0131) after adjustment for age, diabetes, hypertension, Killip class >1, multivessel disease and troponin. The prognostic impact of an eGFR <60 mL/min per 1.73 m(2) was only modestly altered by addition of LV mass or E/e' ratio whereas addition of LV ejection fraction or GLS attenuated its importance considerably.

CONCLUSION

Renal dysfunction in patients with acute MI is independently associated with echocardiographic evidence of increased LV filling pressure. However, the prognostic importance of renal dysfunction is attenuated to a greater degree by LV longitudinal systolic function.

Effects of frequent hemodialysis on ventricular volumes and left ventricular remodeling

BACKGROUND AND OBJECTIVES

Higher left ventricular volume is associated with death in patients with ESRD. This work investigated the effects of frequent hemodialysis on ventricular volumes and left ventricular remodeling.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Frequent Hemodialysis Network daily trial randomized 245 patients to 12 months of six times per week versus three times per week in-center hemodialysis; the Frequent Hemodialysis Network nocturnal trial randomized 87 patients to 12 months of six times per week nocturnal hemodialysis versus three times per week predominantly home-based hemodialysis. Left and right ventricular end systolic and diastolic volumes, left ventricular mass, and ejection fraction at baseline and end of the study were ascertained by cardiac magnetic resonance imaging. The ratio of left ventricular mass/left ventricular end diastolic volume was used as a surrogate marker of left ventricular remodeling. In each trial, the effect of frequent dialysis on left or right ventricular end diastolic volume was tested between predefined subgroups.

RESULTS

In the daily trial, frequent hemodialysis resulted in significant reductions in left ventricular end diastolic volume (-11.0% [95% confidence interval, -16.1% to -5.5%]), left ventricular end systolic volume (-14.8% [-22.7% to -6.2%]), right ventricular end diastolic volume (-11.6% [-19.0% to -3.6%]), and a trend for right ventricular end systolic volume (-11.3% [-21.4% to 0.1%]) compared with conventional therapy. The magnitude of reduction in left and right ventricular end diastolic volumes with frequent hemodialysis was accentuated among patients with residual urine output<100 ml/d (P value [interaction]=0.02). In the nocturnal trial, there were no significant changes in left or right ventricular volumes. The frequent dialysis interventions had no substantial effect on the ratio of left ventricular mass/left ventricular end diastolic volume in either trial.

CONCLUSIONS

Frequent in-center hemodialysis reduces left and right ventricular end systolic and diastolic ventricular volumes as well as left ventricular mass, but it does not affect left ventricular remodeling.