Evolution of Ventricular Hypertrophy and Myocardial Mechanics in Physiologic and Pathologic Hypertrophy.

LEFT VENTRICULAR HYPERTROPHY (LVH) is an adaptive response to physiologic or pathologic stimuli and distinguishing between the two has obvious clinical implications. However, asymmetric septal hypertrophy and preserved cardiac function are noted in early stages in both cases. We characterized the early anatomic and functional changes in a mouse model of physiologic and pathologic stress using serial echocardiography-based morphometry and tissue velocity imaging. Weight-matched CF-1 male mice were separated into CONTROLS (n=10), treadmill EXERCISE 1 hour daily x 5 days/week (n=7) and transverse aortic constriction (TAC, n=7). Hypertrophy was noted first in the LV basal septum compared to other segments in EXERCİSE (0.84±0.02 vs. 0.79±0.03 mm, p=0.03) and TAC (0.86±0.05 vs. 0.77±0.04 mm, p=0.02) at 4 and 3 weeks, respectively. At 8 weeks, eccentric LVH was noted in EXERCISE and concentric LVH in TAC. Septal E/E' ratio increased in TAC (32.6±3.7 vs. 37±6.2, p=0.002) compared with the CONTROLS and EXERCISE (32.3±5.2 vs. 32.8±3.8 and 31.2±4.9 vs. 28.2±5.0, respectively, non-significant for both). Septal s' decreased in TAC (21±3.6 vs. 17±4.2 cm/s, p=0.04) but increased in EXERCISE (19.6±4.1 vs. 29.2±2.3 cm/s, p=0.001) and was unchanged in CONTROLS (20.1±4.2 vs. 20.9±5.1 cm/s, non-significant). Despite similar asymmetric septal hypertrophy and normal global function during the first 2-4 weeks of pathologic and physiologic stress, there is an early reduction in systolic tissue velocity in pathologic but preserved in physiologic hypertrophy. Tissue velocities may help adjudicate between these 2 states when there are no overt anatomic or functional differences.