Background: The potential effects of spontaneous respiration on Doppler mitral inflow patterns in patients with abnormal left ventricular diastolic function are poorly understood. Methods and Results: The respiratory changes of Doppler transmitral flow velocity indexes were investigated in 20 healthy subjects and 20 patients with coronary artery disease. All patients had a mitral inflow pattern of abnormal left ventricular relaxation (reversal of early/late diastolic peak flow velocity ratio). The Doppler mitral inflow signals were measured at end-expiration and end-inspiration. In both groups, the early diastolic peak flow velocity and flow velocity integral, the ratio of early/late diastolic peak flow velocity, and the ratio of early/late diastolic flow velocity integral at end-inspiration were significantly lower than those at end-expiration. However, the late diastolic peak flow velocity and flow velocity integral were not significantly different between end- inspiration and end-expiration. During inspiration, the early diastolic peak flow velocity and the ratio of early/late diastolic peak flow velocity were reduced by an average of 23% and 22%, respectively, in normal subjects and were reduced by an average of 19% and 17%, respectively, in the patient group. Conclusions: Left ventricular early diastolic filling can be substantially reduced by inspiration in normal subjects and in patients with abnormal left ventricular diastolic function. The potential effects of respiratory cycle should be taken into account when assessing left ventricular diastolic function by using Doppler echocardiography.
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