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Figure 1 Depicts the time periods of the entire cardiac cycle (electrocardiogram [ECG] and Doppler flow) in DDD pacing mode (A) compared to the VDD pacing mode (B). Note the prolongation of the mitral inflow time (E + A dur) secondary to the shorter isovolumic contraction time (IVT), isovolumic relaxation time (IVRT), and aortic ejection time (ET) in the VDD as compared to the DDD pacing mode. Data of time intervals are presented as the mean value (ms) ± SD. *p < 0.01 VDD versus DDD. ECG labeling: P = P-wave; R = R-wave; T = T-wave. Doppler inflow labeling: A = A-wave (late transmitral inflow during left atrial contraction); E = E-wave (early transmitral flow).