| Objectives: The aim of this study was to identify the effect of remote ischemic preconditioning (RIPC) on the flow pattern of left anterior descending coronary artery (LAD) and myocardial motion by transthoracic Doppler echocardiography.Materials and Methods:Study 1: 18 normal male volunteers were enrolled to this study. RIPC was induced in the upper part of the non-dominant forearm by a 12-cm-wide blood pressure cuff inflated to 200 mmHg. Recordings were made at baseline and 3 intervals of three ischemia (inflation for 10 minutes) and reperfusion (deflation for 10 minutes) cycles. The Doppler signals of flow velocity were recorded at baseline, the first, third, sixth and ninth minute of reperfusion of each cycle to identify the effect of RIPC on the flow pattern of the left anterior descending coronary artery. Study 2:8 of the normal male volunteers were randomly chosen to take velocity vector imaging for the left ventricular myocardial motion during the reperfusion of RIPC. According to the recommendation of American Society of Echocardiography, which divided the left ventricle into 16 segments, and the demand of Axius Auto EF technology, apical 4chamber views were acquired and recorded the velocity (V, cm/s), strain (ε, %), strain rate (SR, s-1) and time to peak (ms) at the first and third minute of reperfusion of each cycle to identify the effect of RIPC on the myocardial motion.Results:Study 1: The coronary mean velocity, peak diastolic velocity and mean diastolic velocity were increased (all P＜0.05) in the first 3 minutes of reperfusion of each cycle and peak systolic velocity and mean systolic velocity and heart rate did not change compared with the baseline readings throughout RIPC. The maximal coronary flow velocity was observed at the first minute of the second reperfusion with the maximal peak diastolic velocity at 34.8±2.0cm/s, an increase of 21.7±4.2% (P＜0.05) from baseline, the maximal mean diastolic velocity at 25.4±1.4cm/s, an increase of 18.1±3.3% (P＜0.05), the maximal mean velocity was 21.9±1.2cm/s, an increase of 12.3±4.6% (P＜0.05). The increase in coronary blood flow velocity remained throughout all 3 cycles.Study 2: There were no significantly differences in the left ventricular EF, LEV and LDV, which indicated that the integrity of left ventricle didn't change during the RIPC. And V,ε, SR among these segments of the septal and lateral wall during the reperfusion of the RIPC are all with no significant change, showing that there were no significant differences in region myocardium neither. However, the tissue velocities in both systolic phase and diastolic phase were significantly different (P=0.000) among these segments in one wall at the same time, and the values decreased from the base to apical segment. In additional, the values of velocity of the same segment in opposite wall had no significantly differences. The systolic SR time to peak of septal apical segment was the only index that had significantly different during the reperfusion of RIPC (P＜0.05), and the time to peak at the third minute was significantly prolonged 40ms (P＜0.05) than the first minute during the second reperfusion.Conclusion: Remote ischemic preconditioning produces hyperemia via the LAD during early reperfusion, which is characterized by an increase in diastolic flow velocity. The effect of RIPC on coronary flow velocity maintained for three ischemia-reperfusion cycles and the maximal effect seems to be at the second cycle. However, the left ventricle myocardial integrity and local function do not changed significantly during the reperfusion. The increase of coronary flow velocity may play an important role in myocardial protection derived from remote ischemic preconditioning before the ischemic-reperfusion injury.
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