Cardiac function in rats with acute renal failure

Cardiac effects of renal ischemia

Mortality in acute kidney injury (AKI) remains very high, yet the cause of death is often failure of extrarenal organs. We and others have demonstrated remote organ dysfunction after renal ischemia. The term "cardiorenal syndrome" was first applied to the "cross talk" between the organs by the National Heart, Lung, and Blood Institute of the National Institutes of Health, and the clinical importance is being increasingly appreciated. Nevertheless, more information is needed to effectively address the consequences of renal injury on the heart. Since AKI often occurs in patients with comorbidities, we investigated the effect of renal ischemia in the setting of existing cardiac failure. We hypothesized that the cardiac effects of renal ischemia would be significantly amplified in experimental cardiomyopathy. Male Sprague-Dawley rats with preexisting cardiac and renal injury due to low-dose doxorubicin were subjected to bilateral renal artery occlusion. Cardiac structure and function were examined 2 days after reperfusion. Loss of functional myocardial tissue with decreases in left ventricular pressure, increases in apoptotic cell death, inflammation, and collagen, and greater disruption in ultrastructure with mitochondrial fragmentation were seen in the doxorubicin/ischemia group compared with animals in the groups treated with doxorubicin alone or following ischemia alone. Systemic inflammation and cardiac abnormalities persisted for at least 21 wk. These results suggest that preexisting comorbidities can result in much more severe distant organ effects of acute renal injury. The results of this study are relevant to human AKI.NEW & NOTEWORTHY Acute kidney injury is common, expensive, and deadly, yet morbidity and mortality are often secondary to remote organ dysfunction. We hypothesized that the effects of renal ischemia would be amplified in the setting of comorbidities. Sustained systemic inflammation and loss of functional myocardium with significantly decreased systolic and diastolic function, apoptotic cell death, and increased collagen and inflammatory cells were found in the heart after renal ischemia in the doxorubicin cardiomyopathy model (vs. renal ischemia alone). Understanding the remote effects of renal ischemia has the potential to improve outcomes in acute kidney injury.

Acute Kidney Injury Increase Risk of Left Ventricular Remodeling: A Cohort of 1,573 Patients

Background: Acute kidney injury (AKI) is a common complication after coronary angiography (CAG) and associated with heart failure (HF). Left ventricular (LV) remodeling is a vital process in the progression of HF. However, few studies investigate the relationship between AKI and LV remodeling.

Methods: We included consecutive patients undergoing CAG from January 2007 to December 2018 at Guangdong Provincial People’s Hospital (NCT04407936). AKI was defined as an absolute increase in serum creatinine (Scr) of ≥ 0.3mg/dl or a ≥ 50% increase in Scr from baseline within the first 48–72 h after the procedure. LV remodeling was defined as: (1) an absolute decrease in left ventricular ejection fraction (LVEF) of ≥ 10% compared to baseline, or (2) a follow-up LVEF < 40%. Univariate and multivariate logistical regressions were used to assess the association between AKI and LV remodeling.

Results: Of the 1,573 patients (62.2 ± 9.7 years, female 36.7%) included in the study, 231 (14.7%) had AKI. The incidence of LV remodeling was higher in patients with AKI than in those without AKI (24.7% vs. 14.5%). After adjusting for confounding, multivariate logistic regression showed that AKI was associated with a significantly higher risk of LV remodeling [adjusted odds ratio (aOR) 1.87; 95% CI, 1.30–2.66; p < 0.001]. In addition, LV remodeling patients had higher all-cause mortality compared to non-LV remodeling patients (9.7% vs. 19.1%).

Conclusion: Our data suggested that AKI is present in up to 15% of patients after CAG and that nearly a quarter of AKI patients suffered LV remodeling and AKI patients have a two-fold risk of developing LV remodeling than non-AKI patients. Our findings suggest that more active measures be taken not only to prevent AKI patient developing into LV remodeling, but to prevent patients undergoing CAG from developing AKI.

In-Hospital Outcomes of Acute Kidney Injury After Pediatric Cardiac Surgery: A Meta-Analysis

Background: Cardiac surgery-associated acute kidney injury (CS-AKI) is associated with increased morbidity and mortality in both adults and children. This study aimed to investigate the in-hospital outcomes of CS-AKI in the pediatric population. Methods: PubMed/MEDLINE, Embase, Scopus, and reference lists of relevant articles were searched for studies published by August 2020. Random-effects meta-analysis was performed, comparing in-hospital outcomes between patients who developed CS-AKI and those who did not. Results: Fifty-eight publications between 2008 and 2020 consisting of 18,334 participants (AKI: 5,780; no AKI: 12,554) were included. Higher rates of in-hospital mortality (odds ratio [OR] 7.22, 95% confidence interval [CI] 5.27-9.88), need for renal replacement therapy (RRT) (OR 18.8, 95% CI 11.7-30.5), and cardiac arrhythmias (OR 2.67, 95% 1.86-4.80) were observed in patients with CS-AKI. Furthermore, patients with AKI had longer ventilation times (mean difference [MD] 1.76 days, 95% CI 1.05-2.47), pediatric intensive care unit (PICU) length of stay (MD 3.31, 95% CI 2.52-4.10), and hospital length of stay (MD 5.00, 95% CI 3.34-6.67). Conclusions: CS-AKI in the pediatric population is associated with a higher risk of mortality, cardiac arrhythmias and need for RRT, as well as greater mechanical ventilation time, PICU and hospital length of stay. These results might help improve the clinical care protocols prior to cardiac surgery to minimize the disease burden of CS-AKI in children. Furthermore, etiology-specific approaches to AKI are warranted, as outcomes are likely impacted by the underlying cause.

Exaggerated Interventricular Dependence among Trauma and Burn Patients: A Relationship with Kidney Function—An Exploratory Study

Acute kidney injury (AKI) is a serious condition that affects critically ill patients admitted to the ICU. In this study, we report the association between right ventricle shape and AKI in a cohort of burn and trauma patients. This study is a retrospective review of trauma and burn patients who were admitted to our ICU between 2013 and 2016 who underwent hemodynamic transesophageal echocardiography. Left ventricular eccentricity index (LVEI) measurements were performed on still images obtained from transgastric short-axis view clips at end diastole. LVEI was used as a surrogate of right ventricular volume loading. There were 132 patients, the mean age was 50.8 years, and they were predominantly white and males. Using logistic regression and adjusting for age, race, gender, injury mechanism, and injury severity, higher LVEI was independently significantly associated with lower incidence of AKI (odds ratio 0.03, confidence interval 0.00–0.69). Higher LVEI is associated with a lower incidence of AKI in critically injured trauma and burn patients.

Acute kidney injury and disease: Long-term consequences and management

With increasing longevity and the presence of multiple comorbidities, a significant proportion of hospitalized patients, and an even larger population in the community, is at increased risk of developing an episode of acute kidney injury (AKI). Because of improvements in short-term outcomes following an episode of AKI, survivors of an episode of AKI are now predisposed to develop its long-term sequel. The identification of risk for progression to chronic kidney disease (CKD) is complicated by the absence of good biomarkers that identify this risk and the variability of risk associated with clinical factors including, but not limited to, the number of AKI episodes, severity, duration of previous AKI and pre-existing CKD that has made the prediction for long-term outcomes in survivors of AKI more difficult. Being a significant contributor to the growing incidence of CKD, there is a need to implement measures to prevent AKI in both the community and hospital settings, target interventions to treat AKI that are also associated with better long-term outcomes, accurately identify patients at risk of adverse consequences following an episode of AKI and institute therapeutic strategies to improve these long-term outcomes. We discuss the lasting renal and non-renal consequences following an episode of AKI, available biomarkers and non-invasive testing to identify ongoing intra-renal pathology and review the currently available and future treatment strategies to help reduce these adverse long-term outcomes.

Mitochondrial Dysfunction in Cardiorenal Syndrome

SIGNIFICANCE

Acute kidney injury (AKI) has a significant impact on the outcomes of critically ill patients, although no effective and specific treatment against AKI is currently available in the clinical setting. It is assumed that reactive oxygen species production by the mitochondria plays a crucial role in renal damage especially caused by cellular apoptosis. Mitochondrial injury in the heart is reported as an important determinant of myocardial contractility. Clinical epidemiological data indicate that remote organ effects induced by AKI, especially organ cross talk between the kidney and heart, might contribute to the poor outcome of AKI patients.

RECENT ADVANCES

Cardiorenal syndrome (CRS) has recently been defined based on clinical observations that acute and chronic heart failure causes kidney injury and AKI and that chronic kidney disease worsens heart diseases. Possible pathways that connect these two organs have been suggested; however, the precise mechanisms are still unclarified. Mitochondrial injury in the kidney and heart has been shown as a crucial pathway of AKI and acute heart failure by several animal studies.

CRITICAL ISSUES

Clinical evidence clearly shows cardiorenal interactions in clinically ill patients, but evidence for distant organ effects of AKI on the heart is lacking. We recently found dysregulation of mitochondrial dynamics caused by increased Drp1 expression and cellular apoptosis of the heart in an experimental AKI animal model of renal ischemia-reperfusion.

FUTURE DIRECTIONS

Precise mechanisms that induce cardiac mitochondrial injury in AKI remain unclarified. A recently suggested concept of mitochondrial hormesis may need to be considered in chronic cardiorenal interaction. Identifying the role of mitochondrial injury for CRS will enable the development of novel interventional approaches to reduce mortality associated with AKI. Antioxid. Redox Signal. 25, 200-207.

Kidney-Heart Interactions in Acute Kidney Injury

Acute kidney injury (AKI) is a common complication in critically ill patients treated in intensive care units. Renal replacement therapy (RRT)-requiring AKI occurs in approximately 5-10% patients in intensive care unit and their mortality rate is unacceptably high (50-60%), despite sufficient control of uremia using remarkably advanced modern RRT techniques. This suggests that there are unrecognized organ interactions following AKI that could worsen the outcomes. Cardiorenal syndrome has been defined based on clinical observations that acute and chronic heart failure causes kidney injury and AKI and that chronic kidney disease worsens heart diseases. Possible pathways that connect these 2 organs have been suggested; however, the precise mechanisms are yet to be clarified, particularly in AKI-induced cardiac dysfunction. This review focuses on acute cardiac dysfunction in the setting of AKI. A recent animal study demonstrated the dysregulation of mitochondrial dynamics caused by an increased dynamin-related protein 1 expression and cellular apoptosis of the heart in a renal ischemia reperfusion model. Although the precise mechanisms that induce cardiac mitochondrial injury in AKI remain unclear, cardiac mitochondria injury could be a novel candidate of drug targets against high mortality in severe AKI. © 2016 S. Karger AG, Basel.

Biomarkers of acute kidney injury and associations with short- and long-term outcomes

Acute kidney injury is strongly associated with increased mortality and other adverse outcomes. Medical researchers have intensively investigated novel biomarkers to predict short- and long-term outcomes of acute kidney injury in many patient care settings, such as cardiac surgery, intensive care units, heart failure, and transplant. Future research should focus on leveraging this relationship to improve enrollment for clinical trials of acute kidney injury.

Impact of acute kidney injury on distant organ function: recent findings and potential therapeutic targets

Acute kidney injury (AKI) is a common complication in critically ill patients and subsequently worsens outcomes. Although many drugs to prevent and treat AKI have shown benefits in preclinical models, no specific agent has been shown to benefit AKI in humans. Moreover, despite remarkable advances in dialysis techniques that enable management of AKI in hemodynamically unstable patients with shock, dialysis-requiring severe AKI is still associated with an unacceptably high mortality rate. Thus, focusing only on kidney damage and loss of renal function has not been sufficient to improve outcomes of patients with AKI. Recent data from basic and clinical research have begun to elucidate complex organ interactions in AKI between kidney and distant organs, including heart, lung, spleen, brain, liver, and gut. This review serves to update the topic of organ cross talk in AKI and focuses on potential therapeutic targets to improve patient outcomes during AKI-associated multiple organ failure.

Regulation of Mitochondrial Dynamics by Dynamin-Related Protein-1 in Acute Cardiorenal Syndrome

Experimental evidence has clarified distant organ dysfunctions induced by AKI. Crosstalk between the kidney and heart, which has been recognized recently as cardiorenal syndrome, appears to have an important role in clinical settings, but the mechanisms by which AKI causes cardiac injury remain poorly understood. Both the kidney and heart are highly energy-demanding organs that are rich in mitochondria. Therefore, we investigated the role of mitochondrial dynamics in kidney-heart organ crosstalk. Renal ischemia reperfusion (IR) injury was induced by bilateral renal artery clamping for 30 min in 8-week-old male C57BL/6 mice. Electron microscopy showed a significant increase of mitochondrial fragmentation in the heart at 24 h. Cardiomyocyte apoptosis and cardiac dysfunction, evaluated by echocardiography, were observed at 72 h. Among the mitochondrial dynamics regulating molecules, dynamin-related protein 1 (Drp1), which regulates fission, and mitofusin 1, mitofusin 2, and optic atrophy 1, which regulate fusion, only Drp1 was increased in the mitochondrial fraction of the heart. A Drp1 inhibitor, mdivi-1, administered before IR decreased mitochondrial fragmentation and cardiomyocyte apoptosis significantly and improved cardiac dysfunction induced by renal IR. This study showed that renal IR injury induced fragmentation of mitochondria in a fission-dominant manner with Drp1 activation and subsequent cardiomyocyte apoptosis in the heart. Furthermore, cardiac dysfunction induced by renal IR was improved by Drp1 inhibition. These data suggest that mitochondrial fragmentation by fission machinery may be a new therapeutic target in cardiac dysfunction induced by AKI.

Mibefradil is more effective than verapamil for restoring post-ischemic function of isolated hearts of guinea pigs with acute renal failure

The deleterious intracellular Ca(2+) overload in the ischemic-reperfusion injury of the heart can be even more expressed in subjects with acute renal failure in whom maintenance of intracellular Ca(2+) has already been disturbed in normoxia. To study the influence of acute renal failure in ischemic-reperfusion injury on the heart, we used isolated Langendorff's hearts of guinea pigs with gentamicin-induced acute renal failure. We examined arrhythmias, heart contractility and myocardial cell damage during reperfusion. Two specific Ca(2+) channel antagonists, mibefradil (0.1 and 1 microM) and verapamil (0.1 microM), were used to test the possible involvement of T-type and L-type Ca(2+) channels in these processes. We exposed hearts to 50 min of zero-flow global ischemia and 60 min of reperfusion. During reperfusion, unrecoverable ventricular fibrillation appeared more often in hearts of animals with acute renal failure than in control hearts (80% vs. 0%, respectively). Mibefradil, but not verapamil, applied either pre- or post-ischemically, terminated ventricular fibrillation in all hearts of animals with acute renal failure. Mibefradil (0.1 microM only) improved contractility in hearts of animals with acute renal failure during reperfusion by 30%. During reperfusion, lactate dehydrogenase (LDH) release rate increased less in hearts of guinea pigs with acute renal failure than in control hearts and only verapamil decreased it additionally. Thus, our results suggest a more important role of T- than of L-type Ca(2+) channels in ischemic-reperfusion injury in isolated guinea pig hearts with acute renal failure.