Mechanical unloading during left ventricular assist device support increases left ventricular collagen cross-linking and myocardial stiffness.
BACKGROUND
Left ventricular assist devices (LVADs) induce reverse remodeling of the failing heart except for the extracellular matrix, which exhibits additional pathophysiological changes, although their mechanisms and functional consequences are unknown.


RESULTS
Hearts were obtained at transplant from patients with idiopathic dilated cardiomyopathy (DCM) not requiring LVAD support (n=30), patients requiring LVAD support (n=16; LVAD duration, 145+/-33 days), and 5 nonfailing hearts. Left (LV) and right ventricular (RV) ex vivo pressure-volume relationships were measured, and chamber and myocardial stiffness constants were determined. Myocardial tissue content of total and cross-linked collagen, collagen types I and III, MMP-1, MMP-9, TIMP-1, and angiotensin (Ang) I and II were measured. LV size, mass, and myocyte diameter decreased after LVAD compared with DCM without LVAD (P<0.05). Total and cross-linked collagen and ratio of type I to III collagen increased in DCM compared with nonfailing hearts and increased further after LVAD (P<0.05 versus DCM and nonfailing). Concomitantly, chamber and myocardial stiffness increased with LVAD. The ratio of MMP-1 to TIMP-1 increased in DCM and almost normalized after LVAD, favoring decreased collagen degradation. Tissue Ang I and II also increased during LVAD. There was no significant change in the RV of LVAD-supported heart compared with DCM.


CONCLUSIONS
LVAD support increases LV collagen cross-linking and the ratio of collagen type I to III, which is associated with increased myocardial stiffness. Decreased tissue MMP-1-to-TIMP-1 ratio (decreased degradation) and increased Ang levels (stimulants of synthesis) are likely mechanisms for these changes. Lack of significant effects on the RV suggest that hemodynamic unloading of the LV (not provided to the RV) might be the primary factor that regulates these extracellular matrix changes.
Klotz
Stefan
S
Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
Foronjy
Robert F
RF
Dickstein
Marc L
ML
Gu
Anguo
A
Garrelds
Ingrid M
IM
Danser
A H Jan
AH
Oz
Mehmet C
MC
D'Armiento
Jeanine
J
Burkhoff
Daniel
D
D000328:Adult; D000368:Aged; D000803:Angiotensin I / Q000032:analysis; D000804:Angiotensin II / Q000032:analysis; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology*; D003094:Collagen / Q000032:analysis / Q000378:metabolism*; D005260:Female; D006353:Heart-Assist Devices; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000032:analysis; D020780:Matrix Metalloproteinase 9 / Q000032:analysis; D008875:Middle Aged; D009200:Myocardial Contraction; D009206:Myocardium / Q000737:chemistry; D032383:Myocytes, Cardiac / Q000473:pathology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000032:analysis; D016277:Ventricular Function, Left
D019715:Tissue Inhibitor of Metalloproteinase-1; D000804:Angiotensin II; D003094:Collagen; D000803:Angiotensin I; D020780:Matrix Metalloproteinase 9; D020781:Matrix Metalloproteinase 1