Residual Stress Impairs Pump Function After Surgical Ventricular Remodeling: A Finite Element Analysis.
BACKGROUND
Surgical ventricular restoration (Dor procedure) is generally thought to reduce left ventricular (LV) myofiber stress (FS) but to adversely affect pump function. However, the underlying mechanism is unclear. The goal of this study was to determine the effect of residual stress (RS) on LV FS and pump function after the Dor procedure.


METHODS
Previously described finite element models of the LV based on magnetic resonance imaging data obtained in 5 sheep 16 weeks after anteroapical myocardial infarction were used. Simulated polyethylene terephthalate fiber (Dacron) patches that were elliptical and 25% of the infarct opening area were implanted using a virtual suture technique (VIRTUAL-DOR). In each case, diastole and systole were simulated, and RS, FS, LV volumes, systolic and diastolic function, and pump (Starling) function were calculated.


RESULTS
VIRTUAL-DOR was associated with significant RS that was tensile (2.89 ± 1.31 kPa) in the remote myocardium and compressive (234.15 ± 65.53 kPa) in the border zone. VIRTUAL-DOR+RS (compared with VIRTUAL-DOR-NO-RS) was associated with further reduction in regional diastolic and systolic FS, with the greatest change in the border zone (43.5-fold and 7.1-fold, respectively; p < 0.0001). VIRTUAL-DOR+RS was also associated with further reduction in systolic and diastolic volumes (7.9%; p = 0.0606, and 10.6%; p = 0.0630, respectively). The resultant effect was a further reduction in pump function after VIRTUAL-DOR+RS.


CONCLUSIONS
Residual stress that occurs after the Dor procedure is positive (tensile) in the remote myocardium and negative (compressive) in the border zone and associated with reductions in FS and LV volumes. The resultant effect is a further reduction in LV pump (Starling) function.
University of California, San Francisco, California.
Joe Luis
JL
Pantoja
Veterans Affairs Medical Center, San Francisco, California.
Zhihong
Z
Zhang
Veterans Affairs Medical Center, San Francisco, California.
Mehrzad
M
Tartibi
Veterans Affairs Medical Center, San Francisco, California.
Kay
K
Sun
Veterans Affairs Medical Center, San Francisco, California.
Warrick
W
Macmillan
Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California.
Julius M
JM
Guccione
Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California.
Liang
L
Ge
Department of Surgery, University of California, San Francisco, California; Department of Bioengineering, University of California, San Francisco, California; Veterans Affairs Medical Center, San Francisco, California. Electronic address: mark.ratcliffe@va.gov.
Mark B
MB
Ratcliffe
D000818:Animals; D006348:Cardiac Surgical Procedures / Q000379:methods*; D004195:Disease Models, Animal; D020342:Finite Element Analysis; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D019028:Magnetic Resonance Imaging, Cine; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D012756:Sheep; D016277:Ventricular Function, Left / Q000502:physiology*; D020257:Ventricular Remodeling / Q000502:physiology*