Volume Status Impacts CMR-Extracellular Volume Measurements and Outcome in AS Undergoing TAVR

Histopathological myocardial changes in patients with severe aortic stenosis referred for surgical valve replacement: a cardiac magnetic resonance correlation study

AIMS

Myocardial fibrosis (MF) takes part in left ventricular (LV) remodelling in patients with aortic stenosis (AS), driving the transition from hypertrophy to heart failure. The structural changes that occur in this transition are not fully enlightened. The aim of this study was to describe histopathological changes at endomyocardial biopsy (EMB) in patients with severe AS referred to surgical aortic valve replacement (AVR) and to correlate them with LV tissue characterization from pre-operative cardiac magnetic resonance (CMR).

METHODS AND RESULTS

One-hundred fifty-eight patients [73 (68-77) years, 50% women] were referred for surgical AVR because of severe symptomatic AS, with pre-operative CMR (n = 143) with late gadolinium enhancement (LGE), T1, T2 mapping, and extracellular volume fraction (ECV) quantification. Intra-operative septal EMB was obtained in 129 patients. MF was assessed through Masson's Trichrome histochemistry. Immunohistochemistry was performed for both inflammatory cells and extracellular matrix (ECM) characterization (Type I Collagen, Fibronectin, Tenascin C). Non-ischaemic LGE was present in 106 patients (67.1%) [median fraction: 5.0% (2.0-9.7)]. Native T1 was above normal [1053 ms (1024-1071)] and T2 within the normal range [39.3 ms (37.3-42.0)]. Median MF was 11.9% (6.54-19.97), with predominant type I collagen perivascular distribution (95.3%). Sub-endocardial cardiomyocyte ischaemic-like changes were identified in 45% of EMB. There was no inflammation, despite ECM remodelling expression. MF quantification at EMB was correlated with LGE mass (P = 0.008) but not with global ECV (P = 0.125).

CONCLUSION

Patients with severe symptomatic AS referred for surgical AVR have unspecific histological myocardial changes, including signs of cardiomyocyte ischaemic insult. ECM remodelling is ongoing, with MF heterogeneity. These features may be recognized by comprehensive CMR protocols. However, no single CMR parameter captures the burden of MF and histological myocardial changes in this setting.

Quantitative fluid overload in severe aortic stenosis refines cardiac damage and associates with worse outcomes

AIMS

Cardiac decompensation in aortic stenosis (AS) involves extra-valvular cardiac damage and progressive fluid overload (FO). FO can be objectively quantified using bioimpedance spectroscopy. We aimed to assess the prognostic value of FO beyond established damage markers to guide risk stratification.

METHODS AND RESULTS

Consecutive patients with severe AS scheduled for transcatheter aortic valve implantation (TAVI) underwent prospective risk assessment with bioimpedance spectroscopy (BIS) and echocardiography. FO by BIS was defined as ≥1.0 L (0.0 L = euvolaemia). The extent of cardiac damage was assessed by echocardiography according to an established staging classification. Right-sided cardiac damage (rCD) was defined as pulmonary vasculature/tricuspid/right ventricular damage. Hospitalization for heart failure (HHF) and/or death served as primary endpoint. In total, 880 patients (81 ± 7 years, 47% female) undergoing TAVI were included and 360 (41%) had FO. Clinical examination in patients with FO was unremarkable for congestion signs in >50%. A quarter had FO but no rCD (FO+/rCD-). FO+/rCD+ had the highest damage markers, including N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels. After 2.4 ± 1.0 years of follow-up, 236 patients (27%) had reached the primary endpoint (29 HHF, 194 deaths, 13 both). Quantitatively, every 1.0 L increase in bioimpedance was associated with a 13% increase in event hazard (adjusted hazard ratio 1.13, 95% confidence interval 1.06-1.22, p < 0.001). FO provided incremental prognostic value to traditional risk markers (NT-proBNP, EuroSCORE II, damage on echocardiography). Stratification according to FO and rCD yielded worse outcomes for FO+/rCD+ and FO+/rCD-, but not FO-/rCD+, compared to FO-/rCD-.

CONCLUSION

Quantitative FO in patients with severe AS improves risk prediction of worse post-interventional outcomes compared to traditional risk assessment.

Heart failure and excess mortality after aortic valve replacement in aortic stenosis

INTRODUCTION

In aortic stenosis (AS), the heart transitions from adaptive compensation to an AS cardiomyopathy and eventually leads to decompensation with heart failure. Better understanding of the underpinning pathophysiological mechanisms is required in order to inform strategies to prevent decompensation.

AREAS COVERED

In this review, we therefore aim to appraise the current pathophysiological understanding of adaptive and maladaptive processes in AS, appraise potential avenues of adjunctive therapy before or after AVR and highlight areas of further research in the management of heart failure post AVR.

EXPERT OPINION

Tailored strategies for the timing of intervention accounting for individual patient's response to the afterload insult are underway, and promise to guide better management in the future. Further clinical trials of adjunctive pharmacological and device therapy to either cardioprotect prior to intervention or promote reverse remodeling and recovery after intervention are needed to mitigate the risk of heart failure and excess mortality.

Bioimpedance Spectroscopy Reveals Important Association of Fluid Status and T1 -Mapping by Cardiovascular Magnetic Resonance

BACKGROUND

Extracellular matrix expansion is a key pathophysiologic feature in heart failure and can be quantified noninvasively by cardiac magnetic resonance T₁ -mapping. Free water within the interstitial space of the myocardium, however, may also alter T₁ -mapping results.

PURPOSE

To investigate the association between systemic fluid status and T₁ -mapping by cardiac magnetic resonance.

STUDY TYPE

Prospective, observational single-center study.

POPULATION

Two-hundred eighty-five consecutive patients (44.4% female, 70.0 ± 14.9 years old) scheduled for cardiac MR due to various cardiac diseases.

SEQUENCE AND FIELD STRENGTH

1.5-T scanner (Avanto Fit, Siemens Healthineers, Erlangen, Germany). For T₁ -mapping, electrocardiographically triggered modified-Look-Locker inversion (MOLLI) recovery sequence using a 5(3)3 prototype on a short-axis mid-cavity slice and with a four-chamber view was performed.

ASSESSMENTS

MR parameters including native myocardial T₁ -times using MOLLI and extracellular volume (MR-ECV) were assessed, and additionally, we performed bioimpedance analysis (BIA). Furthermore, demographic data and comorbidities were assessed.

STATISTICS

Wilcoxon's rank-sum test, chi-square tests, and for correlation analysis, Pearson's correlation coefficients were used. Regression analyses were performed to investigate the association between patients' fluid status and T₁ -mapping results. A P-value <0.05 was considered statistically significant.

RESULTS

The mixed cohort presented with a mean overhydration (OH) of +0.2 ± 2.4 liters, as determined by BIA. By MR, native T₁ -times were 1038 ± 51 msec and MR-ECV was 31 ± 9%. In the multivariable regression analysis, only OH was significantly associated with MR-ECV (adj. beta: 0.711; 95% CI: 0.28 to 1.14) along with male sex (adj. beta: 2.529; 95% CI: 0.51 to 4.55). In linear as well as multivariable analysis, only OH was significantly associated with native T₁ times (adj. beta: 3.750; 95% CI: 1.27 to 6.23).

CONCLUSION

T₁ -times and MR-ECV were significantly associated with the degree of OH on BIA measurement. These effects were independent from age, sex, body mass index, and hematocrit. Patients' volume status may thus be an important factor when T₁ -time and MR-ECV values are interpreted.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 3.

Fluid overload in patients undergoing TAVR: what we can learn from the nephrologists

Aims

Fluid overload (FO) puts aortic stenosis (AS) patients at risk for heart failure (HF) and death. However, conventional FO assessment, including rapid weight gain, peripheral oedema, or chest radiography, is inaccurate. Bioelectrical impedance spectroscopy (BIS) allows objective and reproducible FO quantification, particularly if clinically unapparent. It is used in dialysis patients to establish dry weight goals. BIS has not been tested for prognostication in AS. This study aimed to evaluate whether BIS adds prognostic information in stable patients undergoing transcatheter aortic valve replacement (TAVR).

Methods and results

Consecutive patients scheduled for TAVR underwent BIS in addition to echocardiographic, clinical, and laboratory assessment. On BIS, mild FO was defined as >1.0 L and severe as >3.0 L. Combined HF hospitalization and/or all‐cause death was defined as primary endpoint. Three hundred forty‐four patients (81.5 ± 7.2 years old, 47.4% female) were prospectively included. FO by BIS was associated with clinical congestion signs, higher serum markers of cardiac injury, poorer left ventricular function, higher pulmonary pressures, and more severe tricuspid regurgitation (all P < 0.05). Yet, clinical examination was unremarkable in >30% in mild FO, only detected by BIS. During 12.1 ± 5.5 months, 67 (19.5%) events were recorded (40 deaths, 15 HF hospitalizations, and 12 both). Quantitatively, every 1 L increase in FO was associated with a 24% (HR 1.24, 95% CI 1.13–1.35, P < 0.001) increase in event hazard. This association persisted after adjustment for STS/EuroSCORE‐II, NT‐proBNP, left ventricular ejection fraction, and renal function.

Conclusions

In patients undergoing TAVR, FO by BIS is strongly associated with adverse outcomes. BIS measurement conveys prognostic information not represented in any currently used AS/TAVR risk assessments.