Natural history of experimental arterial chronic total occlusions.
OBJECTIVE
We sought to perform the first systematic study of the natural history of chronic total arterial occlusions (CTOs) in an experimental model.


BACKGROUND
Angioplasty of CTOs has low success rates. The structural and perfusion changes during CTO maturation, which may adversely affect angioplasty outcome, have not been systematically studied.


METHODS
Occlusions were created in 63 rabbit femoral arteries by thrombin injection. Histology, contrast-enhanced magnetic resonance imaging, relative blood volume (RBV) index, and micro-computed tomography imaging were analyzed at 2, 6, 12, and 18 to 24 weeks.


RESULTS
Early changes were characterized by an acute inflammatory response and negative arterial remodeling, with >70% reduction of arterial cross-sectional area (CSA) from 2 to 6 weeks. Intraluminal neovascularization of the CTO occurred with a 2-fold increase in total (media + intima) microvessel CSA from 2 to 6 weeks (0.014 +/- 0.002 mm2 to 0.023 +/- 0.005 mm2, p = 0.0008) and a 3-fold increase in RBV index (5.1 +/- 1.9% to 16.9 +/- 2.7%, p = 0.0008). However at later time periods, there were significant reductions in both RBV (3.5 +/- 1.1%, p < 0.0001) and total microvessel CSA (0.017 +/- 0.002 mm2, p = 0.011). Micro-computed tomography imaging demonstrated a corkscrew-like recanalization channel at the proximal end at 6 weeks that regressed at later time points. These vascular changes were accompanied by a marked decrease in proteoglycans and accumulation of a collagen-enriched extracellular matrix, particularly at the entrance ("proximal fibrous cap").


CONCLUSIONS
This study is the first to systematically analyze compositional changes occurring during CTO maturation, which may underlie angioplasty failure. Negative remodeling, regression of intraluminal channels, and CTO perfusion, together with the accumulation of dense collagen, may represent important targets for novel therapeutic interventions.
Jaffe
Ronen
R
Schulich Heart Programme, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
Leung
General
G
Munce
Nigel R
NR
Thind
Amandeep S
AS
Leong-Poi
Howard
H
Anderson
Kevan J T
KJ
Qi
Xiuling
X
Trogadis
Judy
J
Nadler
Ariella
A
Shiff
Davida
D
Saperia
Jamie
J
Lockwood
Julia
J
Jacobs
Chaim
C
Qiang
Beiping
B
Teitelbaum
Aaron
A
Dick
Alexander J
AJ
Sparkes
John D
JD
Butany
Jagdish
J
Wright
Graham A
GA
Strauss
Bradley H
BH