Establishing relative release kinetics of faecal indicator organisms from different faecal matrices.

AIMS: A laboratory assay for comparative characterization of various faecal matrices with respect to faecal indicator organism (FIO) release using, artificial rain water. METHODS AND RESULTS: Fresh sheep and beef-cattle faeces, dairy cattle slurry and beef cattle farm yard manure (FYM) were collected from commercial units in south-west England and applied to 20 randomized 1 m(2) plots established on permanent grassland. Representative samples from each faecal matrix (n = 5) were collected on four occasions over 16 days. One gram of each sample was transferred to a sterile vial to which 9 ml of standard local rain was carefully pipetted. The vial was then rotated through 360 degrees, 20 times in 60 s to 'simulate' a standardized interaction of the faecal material with rainfall, providing an assay of comparative release potential. Appropriate decimal dilutions were prepared from the eluent. Following agitation, with a sterile spatula, the remaining faecal material and eluent in the vials were vortex mixed for 60 s before decimal dilutions were prepared from the resulting mixture, providing a quantitative assessment of the total FIO in the sample from which percentage release could be determined. Bacterial concentrations were enumerated in duplicate by membrane filtration following standard methods for FIO. Significant differences in release kinetics of Escherichia coli and enterococci from each of the faecal matrices were determined. CONCLUSIONS: Differences in release from each faecal substrate and between FIO type (E. coli and intestinal enterococci) were observed in this laboratory study. The order of release of E. coli from the faecal matrices (greatest to least, expressed as a percentage of the total present) was dairy cattle slurry > beef cattle FYM > beef-cattle faeces > sheep faeces. For intestinal enterococci the order of percentage release was dairy cattle slurry > beef-cattle faeces > beef cattle FYM > sheep faeces. SIGNIFICANCE AND IMPACT OF THE STUDY: This laboratory-based method provides the first data on the relative release kinetics of FIO from different faecal matrices in rain water. This is fundamental information needed to parameterize laboratory-based microbial models and inform approaches to field and catchment risk assessment.

Reflex increase in blood pressure during the intracoronary administration of adenosine in man.

Infusion of adenosine (0.022-2.2 mg/min) into the left anterior descending (LAD) coronary artery of 26 patients produced a dose-dependent increase in blood pressure without a change in heart rate. At adenosine 2.2 mg/min, systolic pressure rose by 21.0 +/- 2.2 mmHg from 134 +/- 4.3 mmHg (P less than 0.001) and diastolic pressure increased by 10.4 +/- 1.1 mmHg from 76 +/- 1.9 mmHg (P less than 0.001). The rise in arterial pressure was associated with a 22 +/- 3.4% increase in systemic vascular resistance (P less than 0.01) and no change in cardiac output (-2.8 +/- 4.3%, P = NS). Plasma norepinephrine levels rose by 40 +/- 14% from 105 +/- 9 pg/ml (P less than 0.05) and epinephrine levels by 119 +/- 31% from 37 +/- 9 pg/ml (P less than 0.01). Right atrial infusion of adenosine produced insignificant hemodynamic effects, suggesting that systemic spillover of adenosine was not responsible for the observed effects. In 20 cardiac transplant patients with denervated hearts, LAD infusion of adenosine (2.2 mg/min) produced no change in systolic pressure (-0.1 +/- 1.6 mmHg from 139 +/- 3.4 mmHg, P = NS) and a decrement in diastolic pressure (-4.7 +/- 1.2 mmHg from 98 +/- 2.5 mmHg, P less than 0.01). Thus, infusion of adenosine into the LAD coronary artery causes a reflex increase in arterial pressure due to a rise in systemic vascular resistance, probably as a result of increased sympathetic discharge. This reflex pathway may be of importance in disease states such as myocardial ischemia, in which myocardial adenosine levels are elevated.

Atherosclerosis influences the vasomotor response of epicardial coronary arteries to exercise.

We studied the vasomotion of epicardial coronary arteries during exercise and tested the hypotheses that abnormal vasoconstriction is related to the presence of atherosclerosis and may be related to endothelial dilator dysfunction. During cardiac catheterization quantitative coronary angiography was performed in 21 patients during supine bicycle exercise. 21 of 28 smooth, angiographically normal vessel segments dilated (14.0 +/- 1.8%) during exercise; four smooth segments did not change whereas only three constricted. In contrast, 15 of 16 vessel segments with irregularities constricted in response to exercise (17.0 +/- 0.1%) with only one segment dilating. All 10 stenotic segments constricted to exercise (23 +/- 4%). Six patients also received intracoronary acetylcholine before exercise to test endothelium-dependent dilator function. In five of six patients all nine vessel segments showed the same directional response to acetylcholine and exercise. Three irregular and two stenotic segments constricted with acetylcholine (51 +/- 21%) and exercise (9.0 +/- 0.6%). In contrast, four smooth segments dilated to acetylcholine (19 +/- 6%) and exercise (9 +/- 1%). Both exercise and acetylcholine generally dilated smooth but constricted irregular and stenosed coronary segments. It appears likely that atherosclerosis plays an important role in the abnormal vasomotion of diseased coronary arteries during exercise and the pattern of abnormality suggests impairment of vasodilator function.

Responses of coronary arteries of cardiac transplant patients to acetylcholine.

Accelerated coronary atherosclerosis is a major cause of graft failure after heart transplantation. Graft atherosclerosis is typically diffuse and difficult to detect even with coronary arteriography. Recently, acetylcholine was shown to dilate blood vessels by releasing a vasorelaxant substance from the endothelium (endothelium-derived relaxing factor). We have demonstrated paradoxical vasoconstriction induced by acetylcholine both early and late in the course of coronary atherosclerosis in patients, suggesting an association of endothelial dysfunction and atherosclerosis. In this report, we tested the hypothesis that coronary arteries of heart transplant patients can show endothelial dysfunction before or in the early stages of angiographically evident coronary atherosclerosis. Acetylcholine was infused into the left anterior descending artery of 13 heart transplant patients at 12 (n = 9) and 24 (n = 4) mo after transplantation. Vascular responses were evaluated by quantitative angiography. Among patients with angiographically smooth coronary arteries, relatively few (6/25) arterial segments had preserved vasodilator responses, while the majority failed to dilate (10/25) or paradoxically constricted (9/25). Angiographically irregular coronary arteries were present in three patients, in whom 8/10 segments showed marked paradoxical constriction and the remaining 2/10 failed to dilate. Only 1 of 13 patients retained appropriate dilation to acetylcholine in all segments. Nitroglycerin, which acts directly on vascular smooth muscle, dilated nearly all segments. No clinical features of the patients, including myocardial rejection appeared to correlate with the impaired functional response of vessels. Thus impaired response to acetylcholine is a common early finding in heart transplant patients and emphasizes the potential importance of endothelial dysfunction in the development of atherosclerosis.

Control of shear stress in the epicardial coronary arteries of humans: impairment by atherosclerosis.

Altered arterial wall shear stress may adversely affect vascular endothelium and contribute to atherogenesis. This study examined the hypothesis that, in humans, dilation of normal coronary arteries with increased flow limits increases in shear stress and that loss of flow-mediated dilation in atherosclerosis results in failure to control shear stress. Coronary blood flow was increased by infusing adenosine (0.022 to 2.2 mg/min) through a 2.5F Doppler flow catheter positioned in the middle segment of the left anterior descending coronary artery in 8 patients with mild atherosclerosis but no flow-limiting stenosis and in 10 patients with entirely smooth coronary arteries. Quantitative angiography and coronary flow velocity were used to estimate shear stress in a proximal segment of the left anterior descending artery exposed to increased flow, but not to adenosine. The peak increase in blood flow was the same in smooth (371 +/- 65%) and irregular (377 +/- 50%) arteries. However, at peak flow, dilation was greater in smooth segments (16.3 +/- 2.7%) than in irregular segments (2.0 +/- 1.5%) (p less than 0.001). In each patient, smooth segments dilated with increasing shear stress (slope 7.4 +/- 0.9%), whereas irregular segments dilated less (slope 0.9 +/- 0.6%) and showed greater increases in shear stress (p less than 0.01). The peak increase in shear stress was less in smooth (189 +/- 23%) than in irregular (365 +/- 52%) segments (p less than 0.01). These results suggest a control mechanism in normal coronary arteries whereby increases in shear stress stimulate vasodilation and thus limit further increases in this force at the endothelial surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous and surgical interventions for in-stent restenosis: long-term outcomes and effect of diabetes mellitus.

OBJECTIVE: We examined long-term outcomes of patients with in-stent restenosis (ISR) who underwent different percutaneous interventions at the discretion of individual operators: balloon angioplasty (BA), repeat stent or rotational atherectomy (RA). We also examined long-term outcomes of patients with ISR who underwent coronary artery bypass surgery (CABG). BACKGROUND: In-stent restenosis remains a challenging problem, and its optimal management is still unknown. METHODS: Symptomatic patients (n = 510) with ISR were identified using cardiac catheterization laboratory data. Management for ISR included BA (169 patients), repeat stenting (117 patients), RA (107 patients) or CABG (117 patients). Clinical outcome events of interest included death, myocardial infarction, target vessel revascularization (TVR) and a combined end point of these major adverse cardiovascular events (MACE). Mean follow-up was 19+/-12 months (range = 6 to 61 months). RESULTS: Patients with ISR treated with repeat stent had significantly larger average post-procedure minimal lumen diameter compared with BA or RA (3.3+/-0.4 mm vs. 3.0+/-0.4 vs. 2.9+/-0.5, respectively, p < 0.05). Incidence of TVR and MACE were similar in the BA, stent and RA groups (39%, 40%, 33% for TVR and 43%, 40%, 33% for MACE, p = NS). Patients with diabetes who underwent RA had similar outcomes as patients without diabetes, while patients with diabetes who underwent BA or stent had worse outcomes than patients without diabetes. Patients who underwent CABG for ISR, mainly because of the presence of multivessel disease, had significantly better outcomes than any percutaneous treatment (8% for TVR and 23% for MACE). CONCLUSIONS: In this large cohort of patients with ISR and in the subset of patients without diabetes, long-term outcomes were similar in the BA, repeat stent and RA groups. Tissue debulking with RA yielded better results only in diabetic patients. Bypass surgery for patients with multivessel disease and ISR provided the best outcomes.

Estimation of mitral valve area from regression analysis of the pressure gradient in mitral stenosis.

Estimation of mitral valve area (MVA) in the cardiac catheterization laboratory is prone to pitfalls because of the time required for calculations and inaccuracies in the measurement of cardiac output. Because the rate of decrease in the mitral gradient directly correlates with the severity of mitral stenosis, an on-line estimate of MVA at the time of catheterization may be possible with regression analysis of digitized pressure recordings. A total of 61 comparisons of mitral gradient measurements and MVA were obtained in 37 patients at diagnostic catheterization and in 24 patients after balloon mitral valvotomy. Linear and nonlinear regression parameters yielded pressure half-time values and empiric constants similar to those used in Doppler echocardiography for estimation of MVA. The correlations derived from linear analysis were as good as those obtained from nonlinear analysis: from linear analysis, MVAregression = 0.79.MVAGorlin -0.03; r2 = 0.64, p = 0.0001; and from double exponential analysis, MVAregression = 0.86.MVAGorlin -0.07; r2 = 0.74; p = 0.0001. The correlations were not significantly affected by the presence of mild to moderate mitral regurgitation or whether they were obtained after balloon valvotomy. In summary, linear regression analysis yields accurate estimates of MVA despite the theoretical superiority of nonlinear methods. On-line digital analysis of mitral gradient tracings may thus be useful at the time of diagnostic cardiac catheterization or balloon mitral valvotomy to assess the severity of mitral stenosis and the response to interventions.

Comparison of effects of propranolol versus pindolol on sinus rate and pacing frequency in sick sinus syndrome.

Beta blockers in patients with sick sinus syndrome (SSS) may prevent supraventricular arrhythmias, systemic hypertension and myocardial ischemia, but may cause excessive depression of sinus node function. In 8 patients with SSS and a permanent pacemaker, the effect of chronic oral pindolol on sinus rate and pacing frequency was compared with that of propranolol in a double-blind crossover trial. In all patients the pacemaker was programmed to a rate of < or = 50 beats/min. Holter monitors, obtained at baseline and on each drug, were used to calculate peak ambulatory sinus rate, number of paced beats per day, maximal number of paced beats per hour, and percentage of hours with paced beats. The peak sinus rate with pindolol therapy was 24% higher than with propranolol (p = 0.001). During pindolol therapy, the number of paced beats per day and maximal paced beats per hour were reduced 54% (p = 0.04) and 61% (p = 0.02), respectively, compared with propranolol. Patients with SSS who require beta-blocker therapy for tachycardia, systemic hypertension or angina pectoris may have less bradycardia when treated with pindolol rather than propranolol. Beta blockers like pindolol, which cause less sinus node depression, may obviate the need for prophylactic permanent pacemakers in patients with SSS, and may help to prevent chronotropic incompetence and pacemaker syndrome in patients already treated with a VVI device.

Impact of the "stent-when-feasible" policy on in-hospital and 6-month success and complication rates after coronary angioplasty: single-center experience with 17,956 revascularization procedures (1993-1997).

This retrospective, observational, single-center study analyzed the results of a "stent-when-feasible" policy in a real-world setting. The study began in the "pre-stent" period (1993) and ended after the beginning of the "routine stent" period (1997). When the 1993 and 1997 global data were compared, the early and 6-month results included significant improvements in the rates of angiographic success (89.3% vs 97.1%), emergency surgical revascularization (1.0% vs 0.3%), freedom from in-hospital major events (91.2% vs 95.9%), and freedom from 6-month major events (77.2% vs 85.1%). The 6-month redo revascularization rate was reduced by almost half for "any catheter intervention" (19.6% vs 10.7%) and was lowest after stent use (7.7% in 1997).

Cardiac sarcoidosis. An unusual form of acute congestive cardiomyopathy.

We report the case of a previously healthy 45-year-old white man in whom sustained ventricular tachycardia and severe myocardial dysfunction were the only signs of cardiac sarcoidosis. Diagnosis was confirmed by endomyocardial biopsy, and the patient responded well to treatment with amiodarone and prednisone.

The use of probability trees in genetic counselling.

Calculation of genetic risks of persons who may be carriers of X-linked recessive conditions or autosomal dominant diseases with incomplete or delayed penetrance often requires the use of Bayes' theorem. Available methods of computing such risks are often too difficult or too time-consuming for clinicians to use routinely. Probability trees provide a rapid and simple graphical means of estimating genetic risks even in complex clinical situations. The use of probability trees is easily learned because the logic upon which they are based is inherent in their structure.

Fluoroscopic technique of subclavian venous puncture for permanent pacing: a safer and easier approach.

Infraclavicular subclavian puncture may be performed with fluoroscopic observation of the needle trajectory. In 92 patients so implanted between July 1985 and May 1987 uneventful venous access was achieved in 90, one was unsuccessful and one patient had subcutaneous emphysema, a complication rate of 2.2%.

Phorbol ester increases the dihydropyridine-sensitive calcium conductance in a vascular smooth muscle cell line.

In vascular smooth muscle, phorbol esters cause a slowly developing contraction and an associated transmembrane calcium flux, both of which are inhibited by dihydropyridine calcium channel antagonists. In the A7r5 cultured vascular cell line, we used the whole-cell voltage-clamp technique to identify voltage-dependent calcium conductances and investigate the effect of phorbol esters on that conductance having characteristic dihydropyridine sensitivity (slowly inactivating, high-threshold, "L-type"). With barium as the charge carrier, large-amplitude (100-800 pA) inward currents of two types were characterized by their kinetics and voltage dependence. With holding potential--80 mV, a rapidly inactivating, low-threshold current ("T-type") was activated by depolarizations above-40 mV and was maximal at -10 mV. With holding potential -30 mV, this component was inactivated, and a second slowly inactivating, high-threshold current was activated above -10 mV and was maximal at +10 to +20 mV. These currents are similar to the T-type and L-type currents previously described in vascular smooth muscle cells. When added to the bath, the active phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate (100 nM) increased the slowly inactivating (L-type) current by 32 +/- 20% (n = 8, +/- SD). Phorbol-12,13-dibutyrate (100 nM) caused a similar effect, but the inactive phorbol, 4-alpha-phorbol (100 nM), did not. We conclude that at least two distinct calcium conductances are expressed in A7r5 vascular smooth muscle cells, and that the dihydropyridine-sensitive calcium conductance is acutely modulated by phorbol esters, presumably acting through stimulation of protein kinase C. Such modulation may play a role in increasing transmembrane calcium influx mediated by agonist-receptor interactions that lead to activation of protein kinase C and may help to sustain or amplify calcium-dependent cell responses.

Loss of flow-mediated endothelium-dependent dilation occurs early in the development of atherosclerosis.

BACKGROUND: Healthy arteries exhibit endothelium-dependent dilation in response to both local acetylcholine and increased blood flow. In humans, clinically overt coronary artery disease is characterized by loss of dilation to both acetylcholine and blood flow. The temporal relation, however, between functional abnormalities of the endothelium and the development of atherosclerosis has not been established. METHODS AND RESULTS: We examined endothelial vasodilator function in vivo at an early stage of the development of atherosclerosis. Two groups of seven Macaca fascicularis monkeys were studied; one group was fed a high cholesterol diet (0.73-1.0 mg cholesterol per calorie) for 11 months. Cholesterol feeding was associated with increased plasma cholesterol levels and with intimal thickening of the iliac arteries but with no reduction in luminal diameter. Endothelium-dependent vasomotor responses of the iliac arteries were then examined in vivo by quantitative contrast angiography. Acetylcholine produced significant dilation in the controls but paradoxical constriction in the group with early atherosclerosis (+9.0 +/- 3.2% versus -5.3 +/- 5.4%, p less than 0.05). In response to a twofold increase in blood flow achieved by administering adenosine distal to the arterial segment under examination, the controls again dilated, whereas the atherosclerotic group failed to dilate (+ 11.6 +/- 2.1% versus + 0.5 +/- 2.4%, p less than 0.05). Both groups, however, were able to dilate, and dilated equally, to the nonendothelium-dependent agent nitroglycerin (+ 13.7 +/- 4.8% versus + 19.1 +/- 4.3%, NS). CONCLUSIONS: Endothelium-dependent vasodilation in response to both acetylcholine and increased blood flow may be lost early in the course of developing atherosclerosis before the appearance of stenosing and occlusive disease.

Atherosclerosis impairs flow-mediated dilation of coronary arteries in humans.

Studies in animals have suggested that increases in blood flow result in dilation of large arteries by an endothelium-dependent mechanism. Atherosclerosis can impair endothelium-dependent vasodilation to vasoactive agents. The purpose of this study was to determine whether or not large coronary arteries in humans exhibit dilation with increases in blood flow and to test the hypothesis that this response is impaired in the presence of atherosclerosis. Graded concentrations of adenosine were infused into the distal left anterior descending (LAD) coronary artery to test the dilator response of the proximal LAD to increases in blood flow. The proximal LAD was thereby exposed to changes in blood flow, but not directly to adenosine. Ten patients with angiographically smooth proximal LAD segments (group 1) and seven patients with irregularities in the proximal LAD consistent with mild atherosclerosis (group 2) were studied. Infusions of adenosine throughout the range of 0.022 to 2.2 mg/min into the LAD produced a dose-dependent increase in estimated coronary blood flow and a mean increase of 305 +/- 27% at 2.2 mg/min adenosine. At 2.2 mg/min adenosine, a striking difference (p less than 0.001) occurred between the significant flow-mediated dilation of the proximal LAD observed in group 1 (+13.2 +/- 1.3% from 2.63 +/- 0.16 mm, p less than 0.001), and the lack of dilation in group 2 (+1.8 +/- 1.5% from 3.20 +/- 0.17 mm, p = NS), despite a greater increase in coronary blood flow in group 2 (+387 +/- 29%) than in group 1 (+230 +/- 36%).(ABSTRACT TRUNCATED AT 250 WORDS)

Nitroglycerine/N-acetylcysteine in the management of unstable angina pectoris.

N-acetylcysteine (NAC) has been shown to potentiate the haemodynamic and antiplatelet effects of nitroglycerine (NTG) in man, and to limit the development of haemodynamic tolerance to NTG. These effects may be mediated. by the formation of S-nitroso-NAC, which induces vasodilation and strongly inhibits platelet aggregation. In a randomized double-blind study in 46 patients with severe unstable angina pectoris unresponsive to standard treatment (including cutaneous nitrates and calcium antagonists in 45 patients) we compared the effects of intravenous (IV) NTG with those of IV NTG combined with IV NAC (5 g 6 hourly). Treatment with NTG/NAC (24 patients) was associated with a similar frequency of episodes of chest pain as treatment with NTG alone (22 patients), but somewhat fewer increments in infusion rate for pain control (10 vs 17; P NS). The NTG/NAC group had a significantly lower incidence of acute myocardial infarction than the NTG/placebo group (3 vs 10 patients; P = 0.013). Symptomatic hypotension occurred frequently in the NTG/NAC group (7 vs 0 patients; P = 0.006). It is concluded that combined administration of NTG and NAC in patients with unstable angina pectoris may augment the clinical efficacy of NTG, largely by reducing the incidence of acute myocardial infarction. However, the high incidence of severe hypotension with NTG/NAC suggests that this regimen should be used with some caution.

Combined use of nitroglycerin and N-acetylcysteine in the management of unstable angina pectoris.

The vasodilator effects of nitroglycerin (NTG) are mediated via activation of guanylate cyclase; this process is believed to require the availability of free sulfhydryl groups. Previous studies in man have shown that the sulfhydryl donor N-acetylcysteine (NAC) potentiates the systemic and coronary vasodilator effects of NTG. Furthermore, interaction of NTG and NAC may lead to the formation of S-nitroso-NAC, which strongly inhibits platelet aggregation. The effects of intravenous NTG combined with intravenous NAC (5 g 6 hourly) were compared with those of intravenous NTG alone in a double-blind trial in 46 patients with severe unstable angina pectoris unresponsive to conventional treatment, which included calcium antagonists and cutaneous nitrates in all but one patient. Treatment with NTG/NAC (24 patients) and that with NTG alone (22 patients) was associated with a similar frequency of episodes of chest pain and of increments in NTG infusion rate for pain control (10 vs 17; p = NS). The NTG/NAC group had a significantly lower incidence of acute myocardial infarction than the NTG/placebo group (three vs 10 patients; p = .013). Symptomatic hypotension occurred frequently in the NTG/NAC group (seven vs 0 patients; p = .006). Lactate-pyruvate ratios and venous NTG concentrations were not significantly affected by NAC. Subsequently, another 20 consecutive patients were treated with intravenous NTG and continuously infused NAC (10 g/day). Seven remained pain free during the first 24 hr of NTG infusion; 11 required increments in NTG infusion rate for pain control. Acute myocardial infarction occurred in one patient, while none developed symptomatic hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)

Patients with evidence of coronary endothelial dysfunction as assessed by acetylcholine infusion demonstrate marked increase in sensitivity to constrictor effects of catecholamines.

BACKGROUND: Studies in patients undergoing cardiac catheterization have demonstrated that normal coronary arteries dilate and atherosclerotic arteries constrict in response to exercise and the cold pressor test, but the mechanisms are unknown. These vasomotor responses are mirrored by the vasomotor response to the endothelium-dependent agent acetylcholine. Exercise and the cold pressor test are associated with adrenergic stimulation and increased circulating catecholamines. The present study tested the hypothesis that coronary arteries with intact endothelial function are relatively resistant to the constrictor effects of catecholamines, whereas arteries with loss of endothelial function have increased sensitivity to catecholamine-induced constriction. METHODS AND RESULTS: The vasomotor function of the coronary endothelium was assessed by serial acetylcholine infusions (final concentration, 10(-8) to 10(-6) M) in 30 segments in 15 patients with minimal or no evidence of coronary atherosclerosis. The acetylcholine responses were related to the vasomotor response to intracoronary phenylephrine infusion (final concentration, 10(-9) to 10(-6) M) in the same segments. In the group of 18 segments that constricted to acetylcholine, there was a constrictor response to phenylephrine at an approximately 100-fold lower concentration than the group of 12 segments that did not constrict to acetylcholine. CONCLUSIONS: These results suggest that the endothelial dysfunction that characterizes early and late atherosclerosis is associated with a marked increase in sensitivity to the constrictor effects of catecholamines. This finding may explain the constrictor responses of atherosclerotic coronary arteries to exercise and the cold pressor test. In stenotic coronary arteries this mechanism may play a role in the production of myocardial ischemia.

Coronary vasomotor response to acetylcholine relates to risk factors for coronary artery disease.

In animals, acetylcholine dilates normal arteries and produces vasoconstriction in the presence of hypercholesterolemia, hypertension, or atherosclerosis, reflecting endothelial cell dysfunction. In patients with angiographically smooth coronary arteries, acetylcholine has been reported to produce both vasodilation and constriction. To test the hypothesis that the acetylcholine response relates to risk factors for coronary artery disease, acetylcholine 10(-8) to 10(-6) M was infused into the left anterior descending or circumflex coronary artery, and diameter changes were assessed with quantitative angiography in 34 patients with angiographically smooth coronary arteries. The acetylcholine response ranged from +37% (dilation) to -53% (constriction) at the peak acetylcholine dose. All coronary arteries dilated in response to nitroglycerin (26 +/- 17%), suggesting an abnormality of endothelial function in the patients with a constrictor response to acetylcholine. By multiple stepwise regression analysis, serum cholesterol (p less than 0.01), male gender (p less than 0.001), family history (p less than 0.05), age (p less than 0.05), cholesterol level (p less than 0.01), and total number of risk factors (p less than 0.0001) were independently associated with the acetylcholine response. Thus, coronary risk factors are associated with loss of endothelium-dependent vasodilation. The development of vasoconstriction is likely to be an abnormality of endothelial function that precedes atherosclerosis or an early marker of atherosclerosis not detectable by angiography.