Remodelling of left ventricle after banding of ascending aorta in the rat

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Abstract
Study objective – The aim was to study sequential changes of cardiac performance and structure after banding of ascending aorta. Design – Cardiac performance and structure were examined at days 1 and 3, and weeks 1, 2, and 4 postoperatively (aortic banding or sham). Cardiac function indices were measured before and during volume overload. Passive pressure-volume relationship and cardiac morphology were examined at the end of the experiment. Experimental material — 30 aortic banded and 33 age matched, sham operated rats were used for the studies. The animals were anaesthetised, then instrumented for haemodynamic measurements. Measurements and results – The left ventricular weight and calculated left ventricular wall thickness of banded rats increased significantly as early as one day postoperation, compared with the age matched shams. This increase persisted throughout the follow up period, except at day 3, when the increase in left ventricular weight did not reach statistical significance. Left ventricular wall mass/cavitary volume ratio increased significantly in banded rats at all follow up periods except at day 3. Cardiac index of banded rats at rest was not different from that of shams but showed a transient significant reduction at 3 d postoperative. However, maximum cardiac index produced by acute volume overload was not different between the two groups throughout the follow up period. Simultaneous end diastolic pressure was significantly higher in banded rats on the first postoperative day but not in later follow up. The passive pressure-volume curve at 1 d postoperative revealed that left ventricular volumes were significantly smaller in banded rats than in shams, whereas chamber stiffness constant and volume elasticity (chamber stiffness constant normalised for left ventricular volume) were not different between the two groups throughout the follow up period. Conclusions – Taken together, these findings suggest that structural change of the left ventricle may play a role in maintaining left ventricular function by shifting the pressure-volume curve leftward in the early period of aortic banding.