Degenerative changes of the aortic valve during left ventricular assist device support

Abstract

Aims: Donor heart shortage leads to increasing use of left ventricular assist device (LVAD) as bridge-to-transplant or destination therapy. Prolonged LVAD support is associated with aortic valve insufficiency, representing a relevant clinical problem in LVAD patients. Nevertheless, the impact of LVAD support on inflammation, remodelling, and chondro-osteogenic differentiation of the aortic valve is still not clearly understood. The aim of the study is to evaluate the impact of LVAD support on structural and molecular alterations of the aortic valve.

Methods and results: During heart transplantation, aortic valves of 63 heart failure patients without (n = 22) and with LVAD support (n = 41) were collected and used for analysis. Data on clinical course as well as echocardiographic data were analysed. Calcification and markers of remodelling, chondro-osteogenic differentiation, and inflammation were evaluated by computed tomography, by mRNA analysis and by histology and immunohistochemistry. Expression of inflammation markers of the LVAD group was analysed with regard to levels of C-reactive protein and driveline infections. Calcium accumulation and mRNA expression of determined markers were correlated with duration of LVAD support. Data were also analysed relating to aortic valve opening and aortic valve insufficiency. There was no difference in the frequency of cardiovascular risk factors or comorbidities between the patient groups. Expression of matrix metalloproteinase-9 (P = 0.007), alpha-smooth muscle actin (P = 0.045), and osteopontin (P = 0.003) were up-regulated in aortic valves of LVAD patients. Histological appearance of the aortic valve was similar in patients with or without LVAD, and computed tomography-based analysis not yet revealed significant difference in tissue calcification. Expression of interferon gamma (P = 0.004), interleukin-1 beta (P < 0.0001), and tumour necrosis factor alpha (P = 0.04) was up-regulated in aortic valves of LVAD patients without concomitant inflammatory cell infiltration and independent from unspecific inflammation. Expression of matrix metalloproteinase-2 (P = 0.038) and transforming growth factor beta (P = 0.0504) correlated negatively with duration of LVAD support. Presence of aortic valve insufficiency led to a significantly higher expression of interferon gamma (P = 0.007) in LVAD patients. There was no alteration in the determined markers in relation to aortic valve opening in LVAD patients.

Conclusions: Left ventricular assist device support leads to signs of early aortic valve degeneration independent of support duration. Thus, the aortic valve of patients with LVAD support should be closely monitored, particularly in patients receiving destination therapy as well as in the prospect of using aortic valves of LVAD patients as homografts in case of bridge-to-transplant therapy.

Keywords: Aortic valve; Degeneration; Inflammation; Left ventricular assist device; Remodelling.

Figure 1

Flow chart of patient enrolment and experimental setting. Patient enrolment depicting initially screened patients, exclusion criteria, and included patients with subsequent experimental setting. AV, aortic valve; CT, computed tomography scan; HTx, heart transplantation; LVAD, left ventricular assist device; PCR, polymerase chain reaction; w, with; w/o, without.

Figure 2

LVAD induces expression of inflammatory markers in aortic valve tissue. Aortic valves of LVAD patients showed a significantly higher IFNγ (A), IL1β (B), and TNFα (C) mRNA expression compared with aortic valves of HF patients without LVAD support. mRNA expression of IFNγ (D), IL1β (E), and TNFα (F) in aortic valves of LVAD patients showed no difference between patients with and without driveline infection. Each data point reflects an individual biological replicate. Drivel. inf., driveline infection; HF, heart failure; LVAD, left ventricular assist device; ns, not significant.*P value < 0.05; **P value < 0.01; ****P value < 0.0001.

Figure 3

LVAD does not influence gross morphology of aortic valves. Representative images of a subset of aortic valves of three different patients with or without LVAD show haematoxylin/eosin (H&E) and Movat's pentachrome staining. Morphology in representative valves is heterogeneous, and compactness of tissue as well as distribution of extracellular matrix components shows no differences between aortic valves of patients without or with LVAD. LVAD, left ventricular assist device; w/o, without; bars = 400 μm.

Figure 4

LVAD induces remodelling of aortic valve cusp tissue. Aortic valves of LVAD patients show no difference in MMP2 mRNA expression (A), but a significantly higher MMP9 mRNA expression compared with those of HF patients without LVAD. Representative images of immunohistology staining show vimentin‐positive valvular interstitial cells with higher amounts of α‐SMA‐positive cells in aortic valves of patients with LVAD compared with those of HF patients without LVAD (C and D). Each data point reflects an individual biological replicate. HF, heart failure; LVAD, left ventricular assist device; ns: not significant; w/o, without. **P value < 0.01; bars = 50 μm.

Figure 5

LVAD leads to early chondro‐osteogenic differentiation. LVAD support led to a significantly higher mRNA expression of OPN (A) in aortic valves, whereas TGFβ1 (B), ALP (C), and OCN (D) mRNA expression remains unaltered. Quantification of von Kossa staining revealed a heterogeneous distribution and severity of calcification (E). LVAD support did not alter calcium mass in aortic valves (F) as determined by standardized evaluation of computer tomography scans. Each data point reflects an individual biological replicate. HF, heart failure; LVAD, left ventricular assist device; ns, not significant; w/o, without. **P value < 0.01.

Figure 6

Negative correlation of MMP2 and TGFβ mRNA expression with the duration of LVAD support. Spearman correlations were run to determine the relationship between investigated markers and the duration of LVAD support. MMP2 (A) and TGFβ (B) mRNA expression showed a negative correlation with LVAD support duration. Each data point reflects an individual biological replicate. LVAD, left ventricular assist device.

Figure 7

Impact of LVAD support on the aortic valve. Hearts of heart failure patients (A) experience a pulsatile flow through the aortic valve with frequent opening and closure of the valve during systole and diastole (B). The pulsatile blood sustains homeostasis of the aortic valve characterized by quiescent VIC (qVIC; C). Left ventricular unloading as treatment for heart failure bypasses the aortic valve (A') leading to non‐pulsatile blood flow and partial or permanent closure of the valve (B'). Pathological decrease of the shear stress along the valve cusp leads to a change of the VIC phenotype towards activated VIC (aVIC) up‐regulating inflammatory markers, α‐SMA and MMP9 as well as towards osteogenic VIC (oVIC) up‐regulating osteopontin (C′). α‐SMA: alpha‐smooth muscle actin; HF, heart failure; IFNγ, interferon gamma; IL1β, interleukin‐1 beta; LVAD, left ventricular assist device; MMP9, matrix metalloproteinase 9; OPN, osteopontin; TNFα, tumour necrosis factor alpha; VIC, valvular interstitial cells.