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Biomedical subjects

M J Kern

Publications and source records attributed to M J Kern.

At least 181 records · Page 10Linked to original sources
PubMed1993

Use of translesional coronary flow velocity for interventional decisions in a patient with multiple intermediately severe coronary stenoses.

Translesional pressure gradients are currently not performed routinely for most angioplasty procedures because of the technical limitations. With the use of an 0.18 inch Doppler flow velocity guidewire, coronary flow velocity, both proximal and distal to a lesion, can be easily assessed. In branching arteries, significant lesions are characterized by a ratio of proximal to distal flow velocity of > 1.7, loss of the normal phasic diastolic predominant flow velocity pattern, and/or loss of distal hyperemia. We describe the use of coronary flow velocity in assisting important decision making in a young patient with a recent myocardial infarction and multiple coronary lesions. The decision for angioplasty of the hemodynamically significant stenosis was confirmed by translesional flow velocity measurements. A rational approach to coronary intervention in patients with multiple stenoses of intermediate severity appears to be facilitated by direct measurement of translesional flow dynamics.

Adenosine↗
PubMed1993

Quantitative demonstration of dipyridamole-induced coronary steal and alteration by angioplasty in man: analysis by simultaneous, continuous dual Doppler spectral flow velocity.

In the course of studying the effects of coronary angioplasty on branch vessel flow using two Doppler flow velocity guidewires, we quantitated simultaneous blood flow responses proximal and distal to a stenosis. The alterations of flow documented a horizontal epicardial steal induced during dipyridamole hyperemia, hyperemic flow reversal by intravenous aminophylline, and subsequent normalization of distal hyperemia after endoluminal enlargement by successful angioplasty. The quantitative physiology of the patient described here confirms one postulated mechanism of abnormal myocardial perfusion stress scintigraphy. Continuous dual flowire spectral coronary flow determinations appear to be a valuable method in verifying postulated mechanisms of various pharmacologic and mechanical stimuli influencing coronary blood flow in patients with atherosclerotic coronary artery disease.

Adenosine↗
PubMed1993

Application of intracoronary flow velocity for detection and management of ostial saphenous vein graft lesions.

Ostial lesions of saphenous vein grafts can be difficult to assess by angiography. A physiologic approach to the selection and recanalization of ostial lesions in saphenous vein grafts may be advantageous to overcome limitations of angiography. To assist in identifying favorable physiology and facilitate procedural decision making, the use of coronary flow velocity measurements with a Doppler-tipped 0.018-inch angioplasty flowire in three particularly difficult patients with varying types of saphenous vein graft aorto-ostial narrowings is reported.

Aged↗
PubMed1993

Validation of volumetric flow measurements by means of a Doppler-tipped coronary angioplasty guide wire.

We used an in vitro model to validate volumetric flow measurements obtained with an 0.018-inch angioplasty guidewire with a 12 MHz transducer mounted on its tip. By using a modified two-head roller pump device, flow was adjusted incrementally from a minimum of 90 ml/min to a maximum of 550 ml/min. Flow was measured with the Doppler guide wire in tubing ranging from 1.9 mm to 6.0 mm internal diameter, as the product of the spectral Doppler velocity integral and the cross-sectional area of the tubing, over a 1-minute period. It was an excellent correlation between the Doppler calculated flow rates and actual flow, regardless of tubing diameter (r = 0.99). These results suggest that the Doppler spectral output of this device might be accurately applied to estimates of volumetric flow in human coronary arteries.

Angioplasty, Balloon, Coronary↗
PubMed1993

Assessing the hemodynamic significance of coronary artery stenoses: analysis of translesional pressure-flow velocity relations in patients.

OBJECTIVES: The purpose of this study was to examine the relation among the angiographic severity of coronary artery lesions, coronary flow velocity and translesional pressure gradients. BACKGROUND: Determination of the clinical and hemodynamic significance of coronary artery stenoses is often difficult and inexact. Angiography has been shown to be an imperfect tool for determining the physiologic significance of eccentric or irregular coronary lumen narrowing. METHODS: Using a 0.018-in. (0.046 cm) intracoronary Doppler-tipped angioplasty guide wire, spectral flow velocity data both proximal and distal to coronary stenoses were compared with translesional pressure gradient measurements and angiographic data obtained during cardiac catheterization in 101 patients. There were 17 patients with normal angiographic findings and 84 with coronary artery disease, with lesions ranging from 28% to 99% diameter narrowing. Patients with coronary disease were assigned to two groups on the basis of translesional gradients at rest. Group A (n = 56) had gradients < 20 mm Hg, and Group B (n = 28) had gradients > or = 20 mm Hg. RESULTS: Proximal average peak velocity, diastolic velocity integral and total velocity integral were slightly but statistically lower in Group A; however, the distal average peak velocity and diastolic and total velocity integrals were all markedly (all p < 0.01) decreased in patients with gradients > or = 20 mm Hg (Group B). In addition, the ratio of proximal to distal total flow velocity integral was higher in Group B (2.4 +/- 1.0) than in group A (1.1 +/- 0.3, p < 0.001). There was a strong correlation between translesional pressure gradients and the ratios of the proximal to distal total flow velocity integrals (r = 0.8, p < 0.001), with a weaker relation between quantitative angiography and pressure gradients (r = 0.6, p < 0.001). In angiographically intermediate stenoses (range 50% to 70%), angiography was a poor predictor of translesional gradients (r = 0.2, p = NS), whereas the flow velocity ratios continued to have a strong correlation (r = 0.8, p < 0.001). Only two patients with a proximal/distal total flow velocity ratio < 1.7 had a translesional gradient > 30 mm Hg. Both patients had a very proximal lesion in a nonbranching right coronary artery. CONCLUSIONS: These data demonstrate that in branching human coronary arteries, a close relation exists between translesional hemodynamics and distal coronary flow velocity. Translesional coronary flow velocity is a new and easily applicable method for determining the hemodynamic significance of coronary artery stenoses that is superior to angiography and can be applied at the time of diagnostic catheterization. These data will provide a rational approach to making decisions on the use of coronary interventional techniques when angiographic findings are questionable.

Adult↗
PubMed1993

Analysis of coronary blood flow velocity dynamics in angiographically 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.

Angioplasty, Balloon, Coronary↗
PubMed1993

Enhanced coronary blood flow velocity during intraaortic balloon counterpulsation in critically ill patients.

OBJECTIVES: The aim of this study was to assess coronary blood flow during intraaortic balloon counterpulsation by direct measurement. BACKGROUND: In a majority of human studies, increased coronary blood flow during intraaortic balloon counterpulsation measured by indirect techniques has not been consistently demonstrated. METHODS: Hemodynamic variables and coronary blood flow velocity (20-MHz Doppler-tipped catheter) data were measured in 19 patients requiring intraaortic balloon pumping for clinical indications (11 patients had acute myocardial infarction [9 with shock], 6 had unstable angina, 1 had acute mitral regurgitation and 1 was at high risk undergoing angioplasty). Hemodynamic data, mean and phasic diastolic flow velocity and velocity-time integrals (computed from digitized waveforms) were analyzed during periods of 1:1 balloon counterpulsation. RESULTS: Intraaortic balloon pumping decreased systolic pressure (6 +/- 10%, p < 0.001) and increased diastolic pressure (80 +/- 30% from baseline, p < 0.001) without changing RR interval. Peak phasic, mean coronary flow velocity and diastolic flow velocity integral were significantly increased (115 +/- 115%, 67 +/- 61%, 103 +/- 81%, respectively, all p < 0.001) during intraaortic balloon pumping. In addition, although a wide splay of data was evident due to operator set variations in balloon inflation and deflation timing, the greater increases in diastolic flow velocity integral (DFVi) occurred in patients with basal systolic pressure < or = 90 mm Hg (% delta DFVi = 102 - 0.1.[unaugmented systolic pressure], SEE = 21.7 mm Hg, r = 0.30, p < 0.001). CONCLUSIONS: Intraaortic balloon pumping unequivocally and significantly augments proximal coronary blood flow velocity, nearly doubling the coronary flow velocity integral in most patients. This mechanism may be a significant means of ischemia relief in hypotensive patients.

Blood Flow Velocity↗
PubMed1993

Augmentation of coronary blood flow by intra-aortic balloon pumping in patients after coronary angioplasty.

BACKGROUND: Controversy exists regarding the ability of intra-aortic balloon pumping to increase coronary blood flow in patients with obstructive coronary artery disease. To assess the effects of intra-aortic balloon pumping on coronary hemodynamics, we measured coronary blood flow velocity with a 0.018-in. Doppler-tipped angioplasty guide wire in 15 patients who received an intra-aortic balloon pump for typical clinical indications. METHODS AND RESULTS: Intra-aortic balloon pumping augmented diastolic pressure 83 +/- 35%. In nine patients before angioplasty, peak diastolic coronary flow velocity beyond the stenosis (mean diameter narrowing, 95 +/- 7%) was 5.3 +/- 9.6 cm/sec and was unaffected by intra-aortic balloon pumping. After angioplasty, the improved coronary luminal diameter narrowing (n = 12; mean narrowing, 18 +/- 12%) was associated with increased distal diastolic flow velocity integral and peak diastolic and mean velocities (13.3 +/- 8.4 units: 36.4 +/- 18.3 and 24.0 +/- 11.4 cm/sec, respectively; all p < 0.01 versus before angioplasty), which were further augmented (36 +/- 37%, 54 +/- 49%, and 26 +/- 17%, respectively; all p < 0.01) with intra-aortic balloon pumping. Intra-aortic balloon pumping did not significantly increase the distal systolic velocity integral (10 +/- 59%) or peak systolic velocity (3 +/- 33%). Similar degrees of balloon pump augmentation of distal coronary flow velocity values were observed in five angiographically normal reference arteries in four patients. CONCLUSIONS: These data demonstrate lack of significant flow improvement beyond most critical stenoses with intra-aortic balloon pumping and the unequivocal restoration and intra-aortic balloon pump-mediated augmentation of both proximal and distal coronary blood flow velocities after amelioration of severe coronary obstructions in patients after successful coronary angioplasty.

Aged↗