Evaluation of Dynamic Contrast-Enhanced MRI Measures of Lung Congestion and Endothelial Permeability in Heart Failure: A Prospective Method Validation Study

Background

Methods for accurate quantification of lung fluid in heart failure (HF) are needed. Dynamic contrast‐enhanced (DCE)‐MRI may be an appropriate modality.

Purpose

DCE‐MRI evaluation of fraction of fluid volume in the interstitial lung space (v_e) and vascular permeability (K^trans).

Study Type

Prospective, single‐center method validation.

Population

Seventeen evaluable healthy volunteers (HVs), 12 participants with HF, and 3 with acute decompensated HF (ADHF).

Field Strength/Sequence

T₁ mapping (spoiled gradient echo variable flip angle acquisition) followed by dynamic series (three‐dimensional spoiled gradient‐recalled echo acquisitions [constant echo time, repetition time, and flip angle at 1.5 T]).

Assessment

Three whole‐chest scans were acquired: baseline (Session 1), 1‐week later (Session 2), following exercise (Session 3). Extended Tofts model quantified v_e and K^trans (voxel‐wise basis); total lung median measures were extracted and fitted via repeat measure analysis of variance (ANOVA) model. Patient tolerability of the scanning protocol was assessed.

Statistical Tests

This was constructed as an experimental medicine study. Primary endpoints: K^trans and v_e at baseline (HV vs. HF), change in K^trans and v_e following exercise, and following lung congestion resolution (ADHF). K^trans and v_e were fitted separately using ANOVA. Secondary endpoint: repeatability, that is, within‐participant variability in v_e and K^trans between sessions (coefficient of variation estimated via mixed effects model).

Results

There was no significant difference in mean K^trans between HF and HV (P ≤ 0.17): 0.2216 minutes⁻¹ and 0.2353 minutes⁻¹ (Session 1), 0.2044 minutes⁻¹ and 0.2567 minutes⁻¹ (Session 2), 0.1841 minutes⁻¹ and 0.2108 minutes⁻¹ (Session 3), respectively. v_e was greater in the HF group (all scans, P ≤ 0.02). Results were repeatable between Sessions 1 and 2; mean values for HF and HV were 0.4946 and 0.3346 (Session 1), 0.4353 and 0.3205 (Session 2), respectively. There was minimal difference in K^trans or v_e between scans for participants with ADHF (small population precluded significance testing). Scanning was well tolerated.

Data Conclusion

While no differences were detected in K^trans, v_e was greater in chronic HF patients vs. HV, augmented beyond plasma and intracellular volume. DCE‐MRI is a valuable diagnostic and physiologic tool to evaluate changes in fluid volume in the interstitial lung space associated with symptomatic HF.

Level of Evidence

2

Technical Efficacy Stage

2

A randomized multicenter trial on a lung ultrasound-guided treatment strategy in patients on chronic hemodialysis with high cardiovascular risk

Lung congestion is a risk factor for all-cause and cardiovascular mortality in patients on chronic hemodialysis, and its estimation by ultrasound may be useful to guide ultrafiltration and drug therapy in this population. In an international, multi-center randomized controlled trial (NCT02310061) we investigated whether a lung ultrasound-guided treatment strategy improved a composite end point (all-cause death, non-fatal myocardial infarction, decompensated heart failure) vs usual care in patients receiving chronic hemodialysis with high cardiovascular risk. Patient-Reported Outcomes (Depression and the Standard Form 36 Quality of Life Questionnaire, SF36) were assessed as secondary outcomes. A total of 367 patients were enrolled: 183 in the active arm and 180 in the control arm. In the active arm, the pre-dialysis lung scan was used to titrate ultrafiltration during dialysis and drug treatment. Three hundred and seven patients completed the study: 152 in the active arm and 155 in the control arm. During a mean follow-up of 1.49 years, lung congestion was significantly more frequently relieved in the active (78%) than in the control (56%) arm and the intervention was safe. The primary composite end point did not significantly differ between the two study arms (Hazard Ratio 0.88; 95% Confidence Interval: 0.63-1.24). The risk for all-cause and cardiovascular hospitalization and the changes of left ventricular mass and function did not differ among the two groups. A post hoc analysis for recurrent episodes of decompensated heart failure (0.37; 0.15-0.93) and cardiovascular events (0.63; 0.41-0.97) showed a risk reduction for these outcomes in the active arm. There were no differences in patient-reported outcomes between groups. Thus, in patients on chronic hemodialysis with high cardiovascular risk, a treatment strategy guided by lung ultrasound effectively relieved lung congestion but was not more effective than usual care in improving the primary or secondary end points of the trial.

Can the assessment of ultrasound lung water in haemodialysis patients be simplified?

BACKGROUND

Lung ultrasound (US) reliably estimates lung water and it is increasingly applied in clinical practice in dialysis patients. A semi-quantitative US score summing up the US-B lines (an equivalent of B lines in the standard chest X-ray) at 28 sites in the intercostal spaces (Jambrik et al. Usefulness of ultrasound lung comets as a non-radiologic sign of extravascular lung water. Am J Cardiol 2004; 93: 1265-1270) is the most used score.

METHODS

We compared the prognostic performance for death, and cardiovascular (CV) events of the 28-sites US score with a score restricted to eight sites in a cohort of 303 haemodialysis (HD) patients.

RESULTS

The 8- and the 28-sites scores were highly inter-related (Spearman's ρ = 0.93, P < 0.001), and their concordance index was fairly good (k = 0.79, 95% confidence interval 0.74-0.84). During a mean follow-up of 3 years, 112 patients died, and 129 experienced a CV event. At univariate and multivariate analysis, both scores were associated with mortality (P ≤ 0.01) and CV events (P ≤ 0.05). The explained variances (R2) for death and CV events of the 28-sites score in multivariate models including major risk factors for these outcomes in the end-stage kidney disease (ESKD) population were 3.9 and 2.2%, and those of the 8-sites score were 3.1 and 2.4%, respectively. The median time needed to perform the examination was 3.05 min [interquartile range (IQR) 2.22-5.00 min] for the 28-sites score and 1.35 min (IQR 1.16-2.00 min) for the 8-sites score.

CONCLUSION

The 8-sites score is tightly related to the classical Jambrik 28-sites score and this score holds an almost identical predictive power to the reference score. Even though the 28-sites score can be completed just in ∼3 min, the 8-sites score requires only ∼1.30 min, and it is, therefore, better suited for application in everyday clinical practice in HD units.

Comparison between lung ultrasonography and current methods for volume assessment in Asian chronic hemodialysis patients

INTRODUCTION

Volume assessment in end-stage kidney disease patients on hemodialysis (HD) remains inadequate by existing methods: clinical examination, bioimpedance spectroscopy, measurement of inferior vena cava diameter by ultrasound (IVCD), and plasma B-type natriuretic peptide (NT-pro BNP). This study aims to compare the performance of lung ultrasound against existing methods for volume assessment in a HD cohort.

METHODS

Two nephrologists independently performed 28-point lung ultrasound immediately before and after midweek HD in 50 patients. Lung congestion was classified into mild, moderate, and severe categories based on lung ultrasound findings. Clinical examination for crepitations and oedema, change in hydration status (∆HS) measured by bioimpedance spectroscopy, NT-pro BNP, IVCD during inspiration (IVCDimin), expiration (IVCDimax), and inferior vena cava collapsibility index were also assessed before and after midweek HD.

FINDINGS

In all, 61% of patients with normohydration status by bioimpedance spectroscopy had moderate or severe lung congestion on lung ultrasound. There were significant correlations between predialysis lung ultrasound, and NT-pro BNP (r = 0.432, P = 0.004), ∆HS (r = 0.447, P < 0.001), and IVCD parameters (P < 0.05). Some correlations weakened postdialysis (∆HS [r = 0.322, P = 0.01] and IVCDimax [r = 0.307, P = 0.03]), whereas NT-pro BNP and ∆HS paradoxically increased in 28% and 30% of the cohort, respectively. On receiver operator curve analysis, most methods of volume assessment had limited discriminatory power to detect mild lung congestion.

DISCUSSION

Lung ultrasound demonstrates some comparability with existing volume assessment methods in Asian dialysis patients. However, it appears more effective at detecting subclinical pulmonary congestion, and tracking fluid changes real-time compared to bioimpedance spectroscopy and NT-pro BNP.

Comparing lung ultrasound with bioimpedance spectroscopy for evaluating hydration in peritoneal dialysis patients

BACKGROUND

Bioimpedance spectroscopy (BIS), ultrasound lung comets (ULC) and serum biomarkers (N-terminal pro-brain natriuretic peptide, NT-proBNP) have all been used to assist clinicians to determine hydration status in dialysis patients.

METHODS

We performed simultaneous BIS, ULC and NT-proBNP measurements in 27 peritoneal dialysis patients to determine the concordance of the three methods.

RESULTS

Patients with evidence of increasing lung congestion (as determined by ultrasound) were more likely to be diabetic, have systolic hypertension and have higher NT-proBNP (r = 0.65, P < 0.0005). Although there was a trend for patients with high ULC to be overhydrated as determined by BIS, this did not reach statistical significance. Moreover, the correlation between BIS and NT-proBNP (though statistically significant at r = 0.47, P < 0.02) appeared to be weaker.

CONCLUSION

BIS and ULC may be complementary, providing different information, whereas BIS may be more specific to hydration. ULC and NT-proBNP may indicate left ventricular failure coexisting with overhydration.