Doppler-based renal resistance index for the detection of acute kidney injury and the non-invasive evaluation of paravalvular aortic regurgitation after transcatheter aortic valve implantation

Intraoperative renal resistive index threshold as an acute kidney injury biomarker

STUDY OBJECTIVE

The lag in creatinine-mediated diagnosis of cardiac surgery-associated acute kidney injury (AKI) may be impeding the development of renoprotection therapies. Postoperative renal resistive index (RRI) measured by transabdominal Doppler ultrasound is a promising early AKI biomarker. RRI measured intraoperatively by transesophageal echocardiography (TEE) is available even earlier but is less evaluated. Therefore, we conducted an assessment of intraoperative RRI as an AKI biomarker using previously reported post-renal insult thresholds.

DESIGN

Retrospective convenience sample.

SETTING

Intraoperative.

PATIENTS

180 adult cardiac surgical patients between July 2013 and July 2014.

INTERVENTION

None.

MEASUREMENTS

Pre- and post-cardiopulmonary bypass (CPB) RRI thresholds, measured using intraoperative TEE, exceeding 0.74 or 0.79 were used to evaluate for an association with KDIGO AKI risk using the Chi-square test. Other consensus AKI criteria (AKIN, RIFLE) were similarly evaluated. Additional t-test analyses examined the relationship of pre- and pre-to-post (delta) CPB RRI with AKI.

MAIN RESULTS

Post-CPB RRI for 99 patients included 36 and 23 with values exceeding 0.74 and 0.79, respectively. Analyses confirmed associations of both RRI thresholds with all consensus AKI definitions (0.74; KDIGO: p = 0.05, AKIN: p = 0.03, RIFLE: p = 0.03, 0.79; KDIGO: p = 0.002, AKIN: p = 0.001, RIFLE: p = 0.004). In contrast, pre-CPB and pre-to post-CPB RRI were not associated with AKI.

CONCLUSIONS

RRI obtained intraoperatively in cardiac surgery patients, assessed using previously reported thresholds, is highly associated with AKI and warrants further evaluation as a promising "earliest" AKI biomarker. These significant findings suggest that RRI assessment should be included in the standard intraoperative TEE exam.

Acute kidney injury after transcatheter aortic valve replacement in the elderly: outcomes and risk management

Aortic stenosis is the most common cause of valve replacement in Europe and North America with prevalence increasing with age. Transcatheter valve replacement (TAVR) represents an alternative for surgical valve replacement of severely stenotic valves. Despite lower risk of acute kidney injury compared to that associated with surgery, this complication remains prevalent in patients undergoing TAVR. There is a paucity of data confirming the relation of acute kidney injury with high morbidity and mortality, especially when superimposed on chronic kidney disease, which is a frequent comorbidity in the elderly with severe aortic stenosis. As there is no consensus on the prevention of acute kidney injury in patients undergoing TAVR, identification and limitation of risk factors are crucial. In this review, we aim to discuss the key aspects of acute kidney injury diagnosis, risk assessment, and outcomes in TAVR patients, and to point out gaps in current knowledge.

Clinical effects of acute kidney injury after transcatheter aortic valve implantation: a systematic review and meta-analysis

Several observational studies have shown that postoperative acute kidney injury (AKI) may significantly worsen the prognosis of a transcatheter aortic valve implantation (TAVI). The purpose of this systematic review and meta-analysis is to evaluate the recent evidence on the impact of AKI on clinical outcomes following TAVI. A comprehensive search in PubMed, Embase and the Cochrane Library was performed for relevant studies by two independent investigators. We pooled the odds ratio (OR) from individual studies, and performed heterogeneity, quality assessment and publication bias analysis. Forty-three eligible studies comprising 544,112 patients were included. Postoperative AKI not only significantly increased the risk for short-term and long-term all-cause mortality (OR 6.25, 95% CI 5.72-6.83, P < 0.00001; OR 3.49, 95% CI 2.78-4.40, P < 0.00001, respectively), but also increased the risk for early myocardial infarction (OR 3.98, 95% CI 1.90-8.31, P = 0.0002), major and life-threatening bleeding (OR 1.51, 95% CI 1.12-2.03, P = 0.007; OR 2.35, 95% CI 1.80-3.06, P < 0.00001, respectively), major vascular complications (OR 1.69, 95% CI 1.30-2.18, P < 0.0001), need for blood transfusion (OR 2.15, 95% CI 1.89-2.46, P < 0.00001) renal replacement therapy (OR 22.36, 95% CI 11.88-42.12, P = 0.0002) and cerebrovascular accidents (OR 1.92, 95% CI 1.23-2.98, P = 0.004). Acute kidney injury following TAVI is associated with increased postoperative mortality and morbidity. Future efforts are required to determine whether early prevention of post-procedural AKI after TAVI impacts upon clinical outcomes.

The Association of Aortic Valve Pathology With Renal Resistive Index as a Kidney Injury Biomarker

BACKGROUND

Acute kidney injury (AKI) is a common serious complication after cardiac surgery. Doppler-determined renal resistive index (RRI) is a promising early AKI biomarker in this population. However, the relationship between aortic valve pathology (insufficiency and/or stenosis) and RRI is unknown. This study aimed to investigate RRI variability related to aortic valve pathology.

METHODS

In a retrospective review of cardiac surgery patients, RRI and aortic valve pathology were assessed prior to cardiopulmonary bypass using transesophageal echocardiography. Aortic valve status was categorized into four subgroups: normal (insufficiency and stenosis, none/trace/mild), insufficiency (insufficiency, moderate/severe; stenosis, none/trace/mild), combined insufficiency/stenosis (insufficiency and stenosis, moderate/severe), or stenosis (insufficiency, none/trace/mild; stenosis, moderate/severe). RRI and time-matched hemodynamic and Doppler measurements were compared among subgroups.

RESULTS

Of 175 patients, 60 had aortic valve pathology (16 insufficiency, 18 insufficiency/stenosis, 26 stenosis). Compared with the normal subgroup, patients with aortic insufficiency had lower diastolic blood pressure and trough renal Doppler velocities, and higher RRI (0.77 versus 0.69; p < 0.001); patients with combined insufficiency/stenosis also had higher RRI (0.72 versus 0.69, p = 0.042).

CONCLUSIONS

Patients with aortic insufficiency and combined insufficiency/stenosis had higher median RRI values compared with normal patients. For these individuals, diastolic flow differences related to aortic insufficiency may explain why their presurgery RRI values often exceeded postoperative thresholds typically associated with AKI. Strategies to account for the potentially confounding effects of aortic insufficiency on renal flow patterns, independent of renal injury, may add to the value of RRI as an early AKI biomarker.

New markers for early detection of acute kidney injury after transcatheter aortic valve implantation

BACKGROUND

Acute kidney injury (AKI) is a frequent complication after a transcatheter aortic valve implantation (TAVI). Biomarkers such as urinary G1 cell cycle arrest proteins (TIMP-2 and IGFBP7) and sonographic evaluation (Doppler Renal Resistive Index [RRI]) have been advocated to predict AKI at an early stage after a TAVI-procedure. The primary aim was to determine the predictive value of these markers to detect AKI after a TAVI-procedure at an early phase.

PATIENTS AND METHODS

In a prospective observational study, 62 consecutive patients were scheduled for a TAVI. AKI was assessed based on the KDIGO criteria. Biomarkers and RRI were measured concomitantly before TAVI, at the first micturition post-implantation and the first micturition on the morning after the procedure.

RESULTS

Twenty-two patients (35%) developed AKI. On the first day after the TAVI-procedure, urinary TIMP-2 and IGFBP7 concentrations increased significantly in patients who developed AKI (0.1, [interquartile] [0.1-0.35] to 0.40 [0.10-1.00] vs. 0.2 [0.1-0.5] to 0.10 [0.10-0.20], P=0.012) with an area under the receiver-operating characteristic curve of 0.71 [0.55-0.83]. Sensitivity was 0.57 and specificity was 0.83 for a cut-off value of 0.35. No significant increases in RRI were found in patients who developed AKI.

CONCLUSIONS

Based on the current guidelines for the diagnosis of AKI, the urinary proteins TIMP-2 and IGFBP7 do not detect AKI at an early stage accurately in patients undergoing a TAVI-procedure.

Independent Risk Factors Contributing to Acute Kidney Injury According to Updated Valve Academic Research Consortium-2 Criteria After Transcatheter Aortic Valve Implantation: A Meta-analysis and Meta-regression of 13 Studies

OBJECTIVES

This study aimed to examine the risk factors for transcatheter aortic valve implantation (TAVI)-associated acute kidney injury (AKI) according to the AKI definition from the Valve Academic Research Consortium-2 (VARC-2).

SETTING

A meta-analysis.

PARTICIPANTS

A total of 661 patients with post-TAVI AKI according to the VARC-2 definition and 2,012 controls were included in the meta-analysis.

INTERVENTIONS

Patients undergoing TAVI were included in this meta-analysis.

MEASUREMENTS AND MAIN RESULTS

Multiple electronic databases were searched using predefined criteria. The diagnosis of AKI was based on the VARC-2 classification. The authors found that preoperative New York Heart Association class IV (odds ratio [OR], 7.77; 95% confidence interval [CI], 3.81-15.85), previous chronic renal disease (CKD) (OR, 2.81; 95% CI, 1.96-4.03), and requirement for transfusion (OR, 2.03; 95% CI, 1.59-2.59) were associated significantly with an increased risk for post-TAVI AKI. Furthermore, previous peripheral vascular disease (PVD), hypertension, atrial fibrillation, congestive heart failure, diabetes mellitus, and stroke were also risk factors for TAVI-associated AKI. Additionally, transfemoral access significantly correlated with a reduced risk for post-TAVI AKI (OR, 0.43; 95% CI, 0.33-0.57). The potential confounders, including Society of Thoracic Surgeons Score, the logistic European System for Cardiac Operative Risk Evaluation, aortic valve area, mean pressure gradient, left ventricular ejection fraction, age, body mass index, contrast volume, and valve type, had no impact on the association between the risk factors and post-TAVI AKI. Subgroup analysis of the eligible studies presenting multivariate logistic regression analysis on the independent risk factors for post-TAVI AKI revealed that previous CKD, previous PVD, and transapical access were independent risk factors for TAVI-associated AKI.

CONCLUSIONS

The current meta-analysis suggested that previous CKD, previous PVD, and transapical access may be independent risk factors for TAVI-associated AKI.

Transcatheter Aortic Valve Replacement: a Kidney's Perspective

Transcatheter aortic valve replacement (TAVR) has now emerged as a viable treatment option for high-risk patients with severe aortic stenosis (AS) who are not suitable candidates for surgical aortic valve replacement (SAVR). Despite encouraging published outcomes, acute kidney injury (AKI) is common and lowers the survival of patients after TAVR. The pathogenesis of AKI after TAVR is multifactorial including TAVR specific factors such as the use of contrast agents, hypotension during rapid pacing, and embolization; preventive measures may include pre-procedural hydration, limitation of contrast dye exposure, and avoidance of intraprocedural hypotension. In recent years, the number of TAVR performed worldwide has been increasing, as well as published data on renal perspectives of TAVR including AKI, chronic kidney disease, end-stage kidney disease, and kidney transplantation. This review aims to present the current literature on the nephrology aspects of TAVR, ultimately to improve the patients' quality of care and outcomes.

Acute kidney injury after transcatheter aortic valve implantation

Even though experience and techniques have constantly improved over the last years, peri- and postprocedural complications in high risk TAVI-collectives remain a major issue affecting outcome and survival. Acute kidney injury (AKI) is a frequent complication after transcatheter aortic valve implantation (TAVI) and effects outcome and survival. However, the definition of AKI in published studies dealing with the phenomenon of AKI after TAVI varies widely and lacks standardization. This Review aims to present an overview over the current literature concerning AKI after TAVI with regard to the definition of AKI, the impact of AKI on mortality and potential risk factors for renal impairment after TAVI.

Optimizing clinical outcomes of transcatheter aortic valve implantation patients with comorbidities

Transcatheter aortic valve implantation (TAVI) has revolutionized the management of high-risk or inoperable patients presenting with symptomatic severe aortic stenosis (AS). There are several factors to consider to optimize patient outcomes from TAVI. Before TAVI, patient selection is key and an understanding the effects of common comorbidities on outcomes after TAVI is critical. Some comorbidities share common risk factors with AS (e.g. coronary artery disease), others are directly or indirectly caused or exacerbated by severe AS (e.g. atrial fibrillation, pulmonary hypertension, mitral regurgitation, tricuspid regurgitation and right ventricular dysfunction), whereas others are not directly related to severe AS (e.g. chronic kidney disease and chronic lung disease). Choice of transcatheter heart valve prosthesis, vascular access route and mode of anesthesia are important considerations during TAVI. New onset conduction disturbances and arrhythmias remain a vexing issue after TAVI. The aim of the present review is to provide an overview of these issues.

Impact of postoperative acute kidney injury on clinical outcomes after transcatheter aortic valve implantation: A meta-analysis of 5,971 patients

BACKGROUND

There is conflicting evidence on the safety and efficacy of transcatheter aortic valve implantation (TAVI) in patients with postoperative acute kidney injury (AKI). Therefore, we conducted a meta-analysis on the impact of AKI on clinical outcomes after TAVI.

METHODS AND RESULTS

Twenty-four studies including 5,971 patients were analyzed. The mean incidence of AKI in this population was 22.1% ± 11.2. Postoperative AKI significantly increased early (odds ratio [OR] 5.09; 95% confidence interval [CI], 4.03-6.43 and OR 6.14; 95% CI, 3.26-11.55) and 1-year (OR 3.27; 95% CI, 2.42-4.42 and OR 1.93; 95% CI, 1.38-2.71) all-cause and cardiovascular mortality respectively, but also early myocardial infarction (OR 3.30; 95% CI, 1.44-7.57), life-threatening bleeding (OR 2.90; 95% CI, 1.67-5.05), need for transfusion (OR 2.42; 95% CI, 1.96-2.99), and dialysis (OR 14.35; 95% CI, 6.21-33.20), with a non-significant increase of stroke (OR 1.66; 95% CI, 0.94-2.95), hospitalization (mean difference [MD] 1.73; 95% CI, -0.31 to 3.77) and contrast medium received (MD 4.74; 95% CI, -2.33 to 11.81).

CONCLUSIONS

Postoperative AKI seems to significantly worsen TAVI prognosis. The results of the present meta-analysis should be considered hypothesis-generating and future studies on risk stratification, prevention, and postoperative management are needed.

Atherosclerosis burden of the aortic valve and aorta and risk of acute kidney injury after transcatheter aortic valve implantation

BACKGROUND

Atheroembolic renal disease, due to dislodgement of cholesterol crystals during maneuvering of a large catheter across the aorta and deployment of the transcatheter prosthesis within a calcified aortic valve, may be one of the pathophysiological mechanisms of acute kidney injury (AKI) complicating transcatheter aortic valve implantation (TAVI).

OBJECTIVE

To investigate the association between the atherosclerotic burden and plaque characteristics of the aortic valve and thoracic aorta, evaluated with multidetector CT (MDCT), and the occurrence of AKI after TAVI.

METHODS

Aortic valve calcification, atherosclerosis burden, and plaque characteristics of the thoracic aorta (including aortic root, ascending aorta, aortic arch, and descending aorta) were analyzed in preprocedural MDCT data of 210 TAVI patients (age, 81 ± 7.1 years; 51.4% men). The thoracic aorta was divided into ascending aorta, aortic arch, and descending thoracic aorta which was further divided into 5 to 8 segments according to the posterior intercostal arteries. Each segment where the maximum wall thickness exceeded ≥ 2 mm was defined as diseased segment with atherosclerotic plaque. Aortic atherosclerosis burden was defined as the proportion of thoracic aortic segments with atherosclerosis. AKI was defined by a creatinine level ≥ 1.5 × baseline or ≥ 26.4 μmol/L above baseline. MDCT data were correlated with the occurrence of postprocedural AKI in a multivariate logistic regression model.

RESULTS

Postprocedural AKI occurred in 51 patients (24.3%). In patients with AKI, the burden of overall (87.5% [75%-90%] vs 71.4% [50%-87.5%]; P < .001) and noncalcified atherosclerosis (42.9% [22.2%-62.5%] vs 12.5% [0%-28.6%]; P < .001) and the maximum plaque thickness (5.7 ± 1.8 mm vs 4.5 ± 1.4 mm; P < .001) were larger compared with patients without AKI. The burden of noncalcified atherosclerosis remained independently associated with AKI (odds ratio, 1.03 [per each 1% of increase in aortic segments with noncalcified atherosclerosis]; 95% confidence interval 1.01-1.05; P = .006) after adjusting for baseline renal function, logistic EuroSCORE, and procedural access. In contrast, aortic valve calcification was not independently associated with AKI.

CONCLUSION

In patients undergoing TAVI, occurrence of postprocedural AKI was associated with the extent of noncalcified atherosclerotic plaque burden of the thoracic aorta.

Impact of kidney function on mortality after transcatheter valve implantation in patients with severe aortic valvular stenosis

AIMS

Transcatheter aortic valve implantation (TAVI) is an accepted alternative for patients with severe aortic valve stenosis who cannot undergo surgery. Acute kidney injury (AKI) is a serious complication in any invasive cardiovascular intervention. The objectives of the study were to determine (i) the influence of kidney function before TAVI and (ii) the impact of changes in kidney function after TAVI, including acute kidney injury (AKI), on mortality.

METHODS AND RESULTS

A total of 540 patients undergoing TAVI were included. Patients were divided into three groups according to glomerular filtration rate (GFR) before TAVI (A: normal renal function i.e. GFR ≥60ml/min; B: impaired renal function i.e. GFR 30-59ml/min; C: severe impaired renal function i.e. GFR <30ml/min). Multivariate analysis showed a significant impact of GFR on mortality (p<0.0008). Subgroup analysis showed significant differences between the groups in 30-day (A: 5.4%, B: 9.0%, C: 25.0%) and 12-month mortality (A: 15.0%, B: 32.0%, C: 49%). Patients who had an increase in GFR after TAVI by more than 22% (p=0.0068) had an improved survival rate, whereas a decrease in GFR by more than 15% was associated with an increased mortality rate (p=0.0051). AKI occurred in 30 patients (5.6%), of which 22 patients (73.3%) died within 12months.

CONCLUSION

Outcome is significantly related to pre-procedural kidney function. In addition, changes in kidney function after TAVI have a significant impact on mortality. Due to a very poor prognosis in patients with AKI, any effort to prevent this serious complication after TAVI needs to be taken.