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Regional and Global Strain Changes During Biventricular Pacing in a Porcine Model of Acute Left Ventricular Volume Overload
Author(s) -
Wang Alice,
Cabreriza Santos E.,
Quinn T. Alexander,
Richmond Marc E.,
Cheng Bin,
Spotnitz Henry M.
Publication year - 2013
Publication title -
journal of ultrasound in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 91
eISSN - 1550-9613
pISSN - 0278-4297
DOI - 10.7863/jum.2013.32.4.675
Subject(s) - radial stress , medicine , interventricular septum , cardiology , volume overload , pressure overload , strain (injury) , heart failure , hemodynamics , cardiac output , ascending aorta , ventricle , aorta , materials science , deformation (meteorology) , cardiac hypertrophy , composite material
Objectives Biventricular pacing may ameliorate symptoms of acute heart failure. Speckle‐tracking echocardiography can assess cardiac function to elucidate mechanisms of benefit. Accordingly, radial and circumferential strain and radial and circumferential strain synchrony were measured with speckle‐tracking echocardiography during biventricular pacing in a model of left ventricular (LV) volume overload. Methods Heart block was established in 4 open‐chest anesthetized pigs. Left ventricular volume overload was induced with an ascending aorta‐LV apex conduit. Measurements included cardiac output by an aortic flow probe, the maximum derivative of LV pressure versus time (dP/dt max ), and transseptal pressure synchrony. Biventricular pacing was performed for combinations of 3 interventricular delays and 3 LV pacing sites. Speckle‐tracking echocardiographic analysis was applied to short‐axis images at the midpapillary LV for 9 pacing combinations. Strain and synchrony parameters were correlated with hemodynamics. Results Increased cardiac output correlated with improved global circumferential strain ( P = .002) but not changes in global radial strain or radial strain synchrony. Increased LV dP/dt max was associated with improved circumferential strain in the septum ( P < .001) and radial strain in the lateral wall ( P = .046). Improved transseptal pressure synchrony was associated with improved global circumferential strain, but primarily in the septum ( P < .001). Aortic valve closure occurred before peak radial strain in 62% of beats and before peak circumferential strain in 6%. Conclusions During acute LV volume overload, hemodynamic improvement with biventricular pacing was associated with improved circumferential strain primarily in the septum. Radial strain and radial strain synchrony did not correlate with improvement, possibly due to delayed systolic contraction. An increase in circumferential strain in the septum associated with optimum transseptal pressure synchrony suggested improvement by interventricular assist from the right ventricle.