PubMed · 10602931
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J M Rubin. 1999. Flow quantification.. https://doi.org/10.1007/pl00014076
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BACKGROUND: Coronary blood flow occurs mainly during the diastolic phase of each cardiac cycle and is mainly dependent on diastolic driving pressure, especially in the left anterior descending coronary artery (LAD). We hypothesized that calculation of the ratio of the diastolic driving pressure of a stenotic LAD to its normal value, namely diastolic FFR (d-FFR), might provide precise insight into the mechanism of FFR for assessment of the functional severity of the stenosis. We compared d-FFR with FFR, coronary flow reserve (CFR), and exercise myocardial thallium scintigraphy in an lesion of intermediate severity. METHODS AND RESULTS: The study population consisted of 46 consecutive patients with a moderate stenosis in the LAD in whom simultaneous measurements of aortic pressure, left ventricular pressure, and coronary pressure distal to the stenosis were obtained. Coronary flow velocity was successfully measured with a Doppler guidewire in 37 of the 46 patients. Values for FFR, d-FFR, and CFR in the noninvasive test-positive group were significantly lower than those in the negative group. With cutoff values of 0.75, 0.76, and 2.0 for FFR, d-FFR, and CFR, sensitivities were 83.3%, 95.8%, and 88.2% and specificities were 100%, 100%, and 95.0%, respectively. CONCLUSIONS: The close similarity of the sensitivity and specificity of FFR and d-FFR, around almost identical cutoff values (0.75 versus 0.76), confirms the physiological validity of FFR as a clinical standard. In clinical practice, FFR remains the index of choice for assessment of the functional severity of moderate coronary artery stenoses.
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To assess gestational age- and growth-related changes in left ventricular (LV) size, LV wall, and LV transmitral flow velocity patterns, 2-dimensional (2-D) and Doppler echocardiographic studies were performed in 89 normal fetuses aged 16 to 38 weeks. Serial studies were designed in 7 fetuses. Variables measured from 4-chamber views were chamber areas and myocardial wall areas. From these measurements, area shortening fraction and ratio of myocardial wall area to end-diastolic chamber area were calculated. LV end-diastolic chamber area and myocardial wall area increased exponentially with advancing gestational age (r = 0.88 and 0.90, respectively, p < 0.001). Area shortening fraction showed no significant changes with gestational age. Ratio of myocardial wall area to LV end-diastolic chamber area decreased gradually with increasing gestational age (r = -0.77, p < 0.001). With increasing gestational age, mitral peak velocities of early diastole increased (r = 0.82, p < 0.01) with little change in peak velocity during atrial contraction. Multiple regression analysis showed that age-related increases in peak velocity of early diastole were related to advancing gestational age and also to decreases in ratio of myocardial wall area to LV end-diastolic chamber area. Low peak filling velocities during early diastole in younger fetuses may be related partly to relative increase in LV wall mass. The gestational age-related decreases in LV wall mass may be one of the important mechanisms of gestational age-related alterations in diastolic properties, especially relaxation processes.