Slice-by-Slice Pressure-Volume Loop Analysis Demonstrates Native Differences in Regional Cardiac Contractility and Response to Inotropic Agents.
BACKGROUND
Regional changes in diastolic and systolic properties after myocardial infarction contribute to adverse left ventricular (LV) remodeling. Regional function is currently assessed using load-dependent measures such as slice ejection fraction (sEF), wall motion abnormalities, or strain imaging. However, load-independent measures of cardiac function may be useful in the study of the infarction-induced remodeling.


METHODS
In this study, we used a recently validated 2-dimensional (2D) real-time magnetic resonance imaging (MRI) technique to evaluate regional variations in load-independent slice-by-slice measures of systolic and diastolic function and compared the values to a load-dependent measure in 11 sheep at rest and during inotropic agent infusion.


RESULTS
Slice-derived ejection fraction (sEF) was greater in the apex relative to the midventricular and basal regions, and inotropic infusion increased sEF in the base more than in the apex and midventricle. Slice-derived ESPVR (sESPVR) in the apex was significantly lower than in the midventricle and the base, and inotropic infusion increased sESPVR in the apical slices more than in the midventricle. Similarly, slice-derived volume-axis intercept V0 (sV0) was higher in the base relative to the midventricle and apex. sEDPVR did not demonstrate significant regional variations, but inotropic infusion resulted in a small increase in the apex.


CONCLUSIONS
In conclusion, acquisition of slice-derived load-independent measures demonstrated variations that contradict those observed with load-dependent sEF. The approach may provide advanced slice-based measures of function during the LV remodeling process and aid in the development of therapies.
Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania.
Francisco J
FJ
Contijoch
Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania.
Walter R T
WRT
Witschey
Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania.
Jeremy
J
McGarvey
Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania.
Madonna E
ME
Lee
Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania.
Joseph
J
Gorman
Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: robert.gorman@uphs.upenn.edu.
Robert C
RC
Gorman
Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania.
James J
JJ
Pilla
D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D009200:Myocardial Contraction / Q000187:drug effects*; D012756:Sheep; D013318:Stroke Volume
D002316:Cardiotonic Agents