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Figure 2 Analog recordings in a conscious animal before (normal) and after producing progressive heart failure (HF) with four weeks of rapid pacing. Shown are left atrial (LA) and left ventricular (LV) pressures (P_LA/P_LV), LV volume (V_LV), and three LV internal dimensions: anteroposterior (D_AP), septolateral (D_SL), and long axis (D_LA). Under normal conditions, the increase in LV volume during early diastolic filling occurs as all three dimensions expand symmetrically. Most of the increase in LV volume and expansion occurs before the crossover of P_LV and P_LA (dotted line). In contrast, after HF, the expansion of the long axis is delayed (arrows), occurring after P_LA is greater than or equal to P_LV, and most of the early diastolic increase in LV volume and expansion of the short-axis dimensions (D_SL and D_AP) is complete.