Jeanette A. St. Vrain

Analysis of coronary blood flow velocity dynamics in angiographicaily normal and stenosed arteries before and after endolumen enlargement by angioplasty

OBJECTIVES This study was designed to assess whether the spectral waveform of coronary velocity on Doppler study is characteristically altered in the presence of significant stenosis with normalization of the spectral waveform after relief of endolumen obstruction. BACKGROUND Although coronary flow reserve determinations have provided physiologic information complementary to the angiographic percent diameter narrowing, flow velocity measurements have been limited to proximal arteries with inconsistent results after angioplasty. A 12-MHz Doppler guide wire permits flow velocity determination in the proximal and distal coronary artery with fast Fourier spectral analysis. METHODS With the Doppler guide wire, proximal arterial flow velocity and flow reserve measurements in 17 angiographically normal arteries were compared with measurements in 29 significantly stenosed arteries. Proximal and distal flow velocity measurements were also obtained before and after angioplasty of the 29 abnormal arteries. Velocity spectrum was digitized to compute peak diastolic velocity, peak systolic velocity, mean velocity, diastolic/systolic velocity ratio and first third and first half flow fraction. RESULTS Compared with proximal stenosed arteries, proximal normal arteries had significantly higher peak diastolic velocity (64 +/- 26 cm/s vs. 41 +/- 26 cm/s) and higher coronary vasodilator reserve (2.3 +/- 0.8 vs. 1.6 +/- 0.7). Normal arteries had higher flows in the first third and first half of the coronary cycle (46 +/- 3% vs. 39 +/- 7% and 65 +/- 2% vs. 56 +/- 10%, respectively). Before angioplasty, coronary velocity variables were significantly lower distal than proximal to the stenosis. After angioplasty, there was a greater mean increase in distal velocities (200% vs. 90% for the proximal arteries) that resulted in near equalization of proximal and distal mean velocity and a significant reduction in proximal/distal mean velocity ratio (2.4 +/- 1.7 vs. 1.2 +/- 0.4). CONCLUSIONS Before angioplasty, abnormal coronary flow velocity dynamics are more marked distal than proximal to the stenosis. Greater increase in coronary flow velocities in the distal circulation after relief of endolumen obstruction results in a significant reduction in the proximal/distal flow velocity ratio. Thus, normalization of Doppler-derived flow velocity variables with marked reduction of the proximal/distal flow velocity ratios parallels angiographic success and may prove useful as an additional end point measurement in interventional cases with questionable angiographic findings.

Differential characterization of blood flow, velocity, and vascular resistance between proximal and distal normal epicardial human coronary arteries : analysis by intracoronary Doppler spectral flow velocity

To characterize coronary blood flow velocity parameters and to determine the relation among velocity, volumetric flow, and vascular resistance in awake human beings, we performed paired proximal and distal velocity measurements in 28 angiographically normal coronary arteries. Mean velocity, peak velocity, diastolic-to-systolic velocity ratio, and diameter and cross-sectional area of proximal and distal arteries were determined and coronary flow and vascular resistance computed. Mean velocity and coronary vasodilator reserve were similar for all three native arteries and were preserved from proximal to distal segments. Volumetric flow decreased from proximal to distal segments. The demonstrated inverse and curvilinear (polynomial) relation between volumetric flow and vascular resistance agrees with theoretical and animal models of coronary physiologic characteristics and suggests a nadir of coronary vascular resistance below which coronary flow no longer increases.

Quantitation of aortic regurgitation by Doppler echocardiography: A practical approach

Aortic regurgitation is most frequently assessed noninvasively by Doppler echocardiography by use of continuous wave and Doppler color flow mapping. To compare both Doppler methods, 161 patients who had undergone cardiac catheterization and complete echocardiographic studies were studied. The continuous wave parameters analyzed included the slope of the diastolic deceleration and the pressure half-time of the regurgitant jet. From color flow Doppler, conventional parameters such as JH and its ratio to LVOH, JASA and its ratio to LVOA, and the regurgitant JA and its ratio to the LVA were obtained. The JH/LVOH was the color flow parameter that best correlated with angiography (r = 0.91). A ratio of < or = 25% was used to predict mild aortic regurgitation with 96% accuracy. A ratio of > or = 40% was also used to predict severe aortic regurgitation (3 to 4+) with 96% accuracy. Absolute JH at the origin of the regurgitant jet was the second best color flow parameter that correlated with angiography (r = 0.89). When continuous wave-derived slope was used, a significant overlap among different degrees of aortic regurgitation was observed. Predictive accuracy for mild aortic regurgitation was 70% by using a slope < 2 m/sec2 and 86% for severe aortic regurgitation when using a slope > 3 m/sec2. In conclusion, color flow Doppler appears to be superior to continuous wave Doppler in the assessment of aortic regurgitation. The JH/LVOH appears to be the best color parameter for quantifying aortic regurgitation. The measurement of the absolute JH at its origin appears to be the simplest and most practical method for assessing the degree of aortic regurgitation.

Multiskilling and Multicredentialing of the Health Professional: Role of the Cardiac Sonographer

The American Society of Echocardiography (ASE) recognizes that cardiac sonographers are frequently multiskilled and multicredentialed. It is the position of the ASE that, above all, persons who perform cardiac ultrasonography should be fully trained and credentialed in cardiac sonography. If a person is multiskilled (practices another health-related discipline), he or she should be appropriately trained and credentialed in that discipline as well. Possession of multiple credentials provides some evidence that the person has met specific minimum competencies in those areas.This position supports effective, efficient, and high-quality patient care.

Pharmacologic stress-induced regional myocardial blood flow heterogeneity and left ventricular wall thickening abnormality: Comparison of intravenous adenosine with dipyridamole in a model of critical coronary stenosis

Variations in reported sensitivity of myocardial perfusion scans or wall motion abnormalities during pharmacologic stress with intravenous adenosine and dipyridamole may be caused by differences in myocardial oxygen demand or myocardial blood flow redistribution induced by each agent. To investigate the physiologic correlates of functional abnormalities during pharmacologic stress testing, regional myocardial blood flow (radiolabeled microsphere technique) and left ventricular segmental wall thickening (quantitative two-dimensional echocardiography) were measured in 9 dogs with an open chest model of critical stenosis of the left circumflex coronary artery. Data were obtained at baseline and peak drug infusion for intravenous adenosine (0.42 mg/kg over a 3-minute period) and for intravenous dipyridamole (0.56 mg/kg over a 4-minute period). Adenosine and dipyridamole induced regional flow abnormality in 7 (77%) of 9 dogs. Myocardial segments with decreased endocardial/epicardial flow ratio were similar for both agents (2.9 +/- 1.8 vs 2.7 +/- 1.3, p = [NS]). Segments with myocardial flow heterogeneity (ratio of endocardial flow to control left anterior descending/left circumflex endocardial flow) were similar for both agents (2.7 +/- 0.9 vs 2.3 +/- 1.0, p = NS). Adenosine-induced wall thickening abnormality (77% vs 55% with dipyridamole) correlated with regional flow abnormality. Significantly lower mean arterial pressure (53 +/- 1.7 mm Hg vs 64 +/- 1.9 mm Hg, p < 0.01) and more prolonged drug effect (18 +/- 6.4 min vs 3 +/- 1.4 min, p < 0.001) were seen for dipyridamole compared with adenosine. Adenosine induces regional flow abnormality similar to dipyridamole but with less hemodynamic perturbation, and adenosine-induced wall thickening abnormality more closely parallels regional flow abnormality.