摘要:

To determine the effect of atherosclerotic coronary lesions on myocardial blood flow in patients at rest, regional myocardial blood flow was measured distal to stenotic lesions in 29 patients with isolated proximal lesions of the left anterior descending artery. Severity of coronary stenosis was measured by computer-assisted cinevideodensitometric analysis of digitized coronary arteriograms. Regional myocardial blood flow was measured from the clearance rate of intracoronary133Xe injected into the left main coronary artery and recorded with a multicrystal scintillation camera. In 21 patients with stenotic lesions ranging from 19% to 84% area reduction, distal regional myocardial blood flow was normal. In all eight patients with reduced regional myocardial blood flow distal to left anterior descending lesions, the minimum area of each stenotic lesion was less than 0.80 mm2(mean 0.34 ± 0.2 mm2). minimum calculated diameter was less than 1 mm (mean 0.59 ± 0.3 mm), and percent stenosis, based on the reduction in cross-sectional area, was greater than 85% (mean 94 ± 4%). For all patients, distal flow, expressed as a fraction of normal flow, correlated with the lesion cross-sectional area (r = .84), minimum luminal diameter (r = .84), and percent area stenosis (r = -.70). Thus, resting myocardial blood flow distal to stenotic lesions of the proximal coronary arteries remains normal until the degree of narrowing is severe. The dimensions observed for critical coronary stenotic lesions correlate well with theoretical predictions based on fluid mechanics and with experimental preparations in laboratory animals.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

In a study of 307 white patients who underwent coronary angiography, the relationship of coronary artery disease (CAD) to plasma levels of lipoprotein Lp(a) and other lipid-lipoprotein variables was examined. Lp(a) resembles low-density lipoprotein (LDL) in several ways, but can be distinguished and quantified by electroimmunoassay. CAD was rated as present or absent and was also represented by a quantitative lesion score derived from estimates of stenosis in four major coronary vessels. Coronary lesion scores significantly correlated with Lp(a), total cholesterol, triglycerides, LDL cholesterol, and high-density lipoprotein (HDL) cholesterol levels by univariate statistical analysis. By multivariate analysis levels of Lp(a) were associated significantly and independently with the presence of CAD (p < .02), and tended to correlate with lesion scores (p .06). Among subgroups Lp(a) level was associated with CAD in women of all ages and in men 55 years old or younger. An apparent threshold for coronary risk occurred at Lp(a) lipoprotein mass concentrations of 30 to 40 mg/dl, corresponding to Lp(a) cholesterol concentrations of approximately 10 to 13 mg/dl. Plasma Lp(a) in white patients appears to be a major coronary risk factor with an importance approaching that of the level of LDL or HDL cholesterol.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

When renal perfusion pressure is reduced in experimentally induced low-output states, glomerular filtration rate is preserved by angiotensin II-mediated efferent arteriolar vasoconstriction, but available evidence in man suggests that angiotensin II supports renal function only to the extent that it preserves systemic blood pressure. We performed simultaneous assessments of cardiac and renal function in 56 patients with severe chronic heart failure before and after 1 to 3 months of convertingenzyme inhibition. Among the 29 patients with a pretreatment renal perfusion pressure under 70 mm Hg, patients with preserved renal function (creatinine clearance > 50 ml/min/1.73 M2) had markedly elevated values for plasma renin activity (11.8 ± 3.8 ng/ml/hr) and showed a significant decline in creatinine clearance after converting-enzyme inhibition (61.1 ± 3.0 to 45.9 ± 5.3 ml/min/1.73 M2; p < .05). In contrast, although similar with respect to all pretreatment demographic, hemodynamic, and clinical variables, patients with a creatinine clearance under 50 ml/min/1.73 m2had low values for plasma renin activity (3.4 ± 0.8 ng/ml/hr) and, despite similar drug-induced decreases in systemic blood pressure, showed no change in creatinine clearance after therapy with captopril or enalapril (32.6 ± 2.5 to 41.4 ± 3.8 ml/min/1.73 M2). Changes in creatinine clearance varied linearly and inversely with pretreatment values for plasma renin activity (r = - .64, p < .001); converting-enzyme inhibition effectively abolished the pretreatment difference in renal function seen in the high- and low-renin subgroups. In the 27 patients with a renal perfusion pressure of 70 mm Hg or greater, creatinine clearance did not vary significantly with plasma renin activity and was not altered by therapy. These data indicate that the renin-angiotensin system plays an important role in preserving glomerular filtration rate in patients with congestive heart failure in whom renal perfusion pressure is severely compromised and that this effect is achieved independently of the ability of this hormonal system to support systemic blood pressure.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

During maximal upright exercise, blood flow to working skeletal muscle is frequently reduced in patients with nonedematous chronic heart failure. It has been speculated that this reduced muscle flow may be caused in part by an intrinsic impairment of skeletal muscle vasodilatory capacity. To test this hypothesis, forearm blood flow and resistance were comparead during forearm exercise and in response to transient forearm ischemia (10 min) in 22 patients with heart failure and in 1 1 normal subjects. During forearm exercise, both groups exhibited comparable forearm blood flows (ml/min/100 ml) (0.2 W: normal 5.9 ± 3.1, heart failure 6.5 ± 2.8; 0.4 W: normal 8.2 ± 5.5, heart failture 8.2 ± 3.6; 0.6 W: normal 11.5 ± 6.8, heart failure 11.8 + 4.8 [all p = NS]) and forearm vascular resistances (mm Hg/ml/min/100 ml) (0.2 W: normal 23.1 ± 12.4, heart failure 18.5 ± 7.8; 0.4 W: normal 16.9 ± 7.7, heart failure 14.7 ± 6.4; 0.6 W: normal 13.1 ± 7.7, heart failure 10.3 ± 4. 1 Lall p = NS]). Ten minutes of forearm ischemia, an intervention that produces maximal forearm vasodilation, also resulted in comparable forearm vascular resistances in both groups (normal 4.1 ± 2.4, heart failure 3.8 ± 1.3 mm Hg/ml/min/100 ml/ p = NS). These data suggest that skeletal muscle vasodilatory capacity is not intrinsically impaired in patients with nonedematous chronic heart failure.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

A recently developed apparatus provides on-line continuous monitoring of systemic vascular resistance (SVR) by means of simple computer analysis of the peripheral arterial waveform. The fundamental equation of this method is Ri = P'/(dP/dt), where dP/dt is the peak dP/dt of the peripheral arterial waveform, P' is the pressure at time of peak dP/dt, and Ri is a resistance index that bears a direct relation to SVR. Eleven patients undergoing percutaneous transluminal coronary angioplasty (PTCA) were studied to evaluate the changes in SVR associated with myocardial ischemia (angina detection). There were 49 balloon inflations, all of which were associated with an increase in Ri (from 38.4 ± 12 to 81.2 ± 36 × 103 sec; p < .01) and a decrease in dP/dt (from 2076 ± 257 to 1327 ± 326 mm Hg/sec; p < .01). In 42 of the balloon inflations these changes were associated with electrocardiographic ST-T changes and in 23 it was also associated with anginal pain. When angina was present, a further increase in Ri (to 97.5 ± 43 × 10−3sec; p < .01) and a decrease in dP/dt (to 1218 ± 338 mm Hg/sec; p < .01) was observed. It was found that myocardial ischemia is associated with an increase in the resistance index and a decrease in dP/dt and can be detected by the resistometer.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

For patients with stenotic native valves, the modified Bernoulli equation (ΔP = 4v2) may be applied to Doppler-measured transvalvular velocities to yield an accurate estimate of transvalvular gradients. Although it would be useful if the same approach could be used for those with stenotic prosthetic valves, no previous study has validated the Doppler technique in this setting. We therefore recorded simultaneous continuous-wave Doppler flow profiles and transvalvular manometric gradients in 12 catheterized patients in whom all atrial and ventricular pressures were directly measured (transseptal left atrial catheterization and transthoracic ventricular puncture were performed where necessary). A total of 13 prostheses were studied: 11 mitral (seven porcine, three Starr-Edwards, and one Bjiork-Shiley) and two tricuspid (one porcine and one Bjork-Shiley). The Doppler-determined mean gradient was calculated as the mean of the instantaneous gradients (ΔP = 4v2) at 10 msec intervals throughout diastole. The correlation of simultaneous Doppler (DMG) and manometric mean gradients (MG) for the whole group (n 13) demonstrated a highly significant relationship (MG = 1.07DMG ± 0.28; r = .96, p = .0001). The correlation was equally good for porcine valves alone (n = 8) (MG - 0.O6DMG ± 0.55; r = .96, p = .001) and for mechanical valves alone (n = 5) (MG = 1.06DMG -0.04; r = .93, p = .02). In a subset of patients without regurgitation (n = 8), prosthetic valve areas were estimated by two Doppler methods originally described by Holen and Hatle, as well as by the invasive Gorlin method. As expected from theoretical considerations, a close correlation was not demonstrated between results of the Gorlin method and those of either Hatle's Doppler method (r = .65, fp = NS) or Holen's method (r = .14, p - NS). Comparison of the results of the two Doppler methods yielded a somewhat closer correlation (r = .73, p .05). These results suggest that in patients with disk-occluder, ball-occluder, and porcine prosthetic valves, Doppler estimates of transvalvular gradients are virtually identical to those obtained invasively.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The value of performing biplane vs single plane analysis of regional wall motion from contrast ventriculograms was determined in 102 patients who received thrombolytic therapy and who underwent biplane ventriculography during acute myocardial infarction (n = 67), at follow-up more than 2 weeks later (n - 80), or both (n = 45). Hypokinesis in the infarct region and hyperkinesis in the noninfarct region were measured by the centerline method in the respective artery territories, which were defined from the data of 62 patients with single-vessel disease and were expressed in units of standard deviations from the mean of 32 normal subjects. Hypokinesis was more severe and extended over a longer segment of the left ventricular contour when measured in the right anterior oblique (RAO) projection in thrombosis of the left anterior descending coronary artery (LAD) but more severe and extensive in the left anterior oblique (LAO) projection in circumflex stenosis. Hyperkinesis opposite the LAD or the circumflex was greater in the LAO projection. In patients with thrombosis of the right coronary artery, wall motion abnormalities were similar in the two projections. Thus the evaluation of hypokinesis caused by acute coronary thrombosis and of the effect of therapeutic interventions in salvaging function can be adequately evaluated from single-plane 30 degree RAO ventriculograms, except in the small minority of patients with circumflex thrombosis.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

At the present time the most useful technique with which to examine the kinetics of lowdensity lipoprotein (LDL) cholesterol in vivo is the labeled LDL turnover study. However, a major limitation of this method is that, despite its ability to accurately measure both the plasma LDL concentration and LDL production rate, it cannot directly quantify LDL receptor activity. The present study defines the equations that describe the relationship between LDL cholesterol production rate, LDL receptor number, and plasma LDL cholesterol concentration. These equations provide a method that allows calculation of total LDL receptor activity based on the results of an LDL turnover study. With the use of this technique and data from previously published series, the effects of the genetic absence of receptors, aging, and the treatment of hypercholesterolemia with mevinolin on LDL cholesterol kinetics were analyzed.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Symptoms of congestive heart failure frequently reflect abnormalities in both systolic and diastolic performance. While much work has been reported regarding the mechanisms by which positive inotropic and vasodilator therapy affect systolic performance, little is known about their effect on diastolic function. In 12 patients with diffuse congestive cardiomyopathy micromanometer left ventricular and aortic pressure measurements were recorded simultaneously with two-dimensionally targeted M mode echocardiograms and thermodilution-determined cardiac output. Each patient received dopamine (2, 4, and 6 μ/kg/min), and dobutamine (2, 6, and 10 μ/kg/min), and 10 received nitroprusside (0.125 to 2.0 μ/kg/min). Baseline hemodynamics were characterized by low cardiac index (2.1 ± 0.7 liter/min/m2, mean ± SD), high left ventricular end-diastolic pressure (24 ± 10 mm Hg), and increased end-diastolic (6.8 ± 1.0 cm) and end-systolic dimensions (6.0 ± 1.0 cm). All patients had abnormal left ventricular pressure decay with a prolonged time constant (67 ± 20 msec) and reduced peak diastolic lengthening rates. Dopamine and dobutamine decreased the time constant of relaxation and increased the peak lengthening rate. Dobutamine also reduced the minimum diastolic pressure from 14 ± 7 to 10 ± 9 mm Hg (p < .01); neither drug reduced end-diastolic pressure. In fact, dopamine elevated end-diastolic pressures in seven patients, despite more rapid pressure decay. Diastolic pressure-dimension relations after dopamine and dobutamine showed a leftward shift with a reduced end-systolic chamber size, but no significant changes in passive chamber stiffness. Nitroprusside decreased left ventricular minimum diastolic pressure by 4 ± 2 mm Hg and end-diastolic pressure by 7 ± 4 mm Hg (p < .0 1). It did not consistently accelerate left ventricular pressure decay at the doses tested. The decreased end-diastolic pressure with nitroprusside was due to a reduced end-diastolic dimension in five patients. In the other patients, all of whom had elevated right atrial pressures, diastolic pressure-dimension relations showed a parallel downward shift after nitroprusside. Thus, positive inotropic therapy with /31-adrenoceptor agonists enhances early diastolic distensibility by accelerating relaxation, augmenting filling, and reducing end-systolic chamber size. Vasodilator therapy is much more effective in lowering diastolic pressures. In some patients this is due to a reduction in extrinsic restraint of the pericardium and/or right ventricular interaction, while in others it simply reflects a decrease in chamber size without alterations in ventricular passive chamber properties.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID