Acetylcholine-induced constriction of angiographically normal coronary arteries is not time dependent in transplant recipients. Effects of stepwise infusion at 1, 6, 12 and more than 24 months after transplantation

Epicardial coronary artery constriction to cold pressor test is predictive of cardiovascular events in hypertensive patients with angiographically normal coronary arteries and without other major coronary risk factor

Epicardial coronary endothelial dysfunction independently predicts cardiovascular events in patients with coronary risk factors. This study was designed to evaluate outcome of hypertensive patients on the basis of their epicardial coronary function assessed by cold pressor test (CPT). Control subjects (n = 68, 48.8 +/- 7.6 years) and hypertensive patients (n = 83, 51.3 +/- 7.9 years) with angiographically normal coronary arteries and without other major coronary risk factor underwent epicardial coronary reactivity assessment to CPT using quantitative angiography. Cardiovascular events were recorded with a mean follow-up of 115 months (range 84-132). In control subjects, dilation occurred in 88.2%, no change in 11.8% (mean diameter change: +14.6 +/- 9.3%). In hypertensive patients, dilation occurred in 13.3%, no change in 25.3% (mean diameter change for both: +10.9 +/- 11.2%), and constriction in 61.4% (mean diameter change: -12.7 +/- 3.4%). Endothelium-independent dilation was normal in control subjects and hypertensive patients. In control subjects, there were three cardiovascular events in two subjects (2.9%). In hypertensive patients, there were 17 cardiovascular events in 12 patients (14.5%, P < 0.01 versus control subjects), with 15 cardiovascular events in the 10/51 patients (19.6%) with coronary artery constriction, and two cardiovascular events in the 2/32 patients (6.3%) with no change or dilation (P < 0.05). In conclusion, in hypertensive patients with angiographically normal coronary arteries and without other major coronary risk factors, epicardial coronary artery dysfunction assessed by the cold pressor test is predictive of long-term cardiovascular events.

Prognostic value of epicardial coronary artery constriction to the cold pressor test in type 2 diabetic patients with angiographically normal coronary arteries and no other major coronary risk factors

OBJECTIVE

Endothelium-dependent coronary dilation is impaired in diabetic patients and has been found to independently predict cardiovascular events (CVEs) in patients with multiple coronary risk factors. The aim of this study was to evaluate the outcome of type 2 diabetic patients on the basis of epicardial coronary dysfunction.

RESEARCH DESIGN AND METHODS

We examined 56 control subjects (aged 51.7 +/- 6.4 years) using coronary artery response to the cold pressor test (quantitative coronary angiography) and compared them with 72 type 2 diabetic patients (aged 50.3 +/- 8.5 years) without other major coronary risk factors.

RESULTS

Average diameter change was 17.2 +/- 10.4% in the control subjects, dilation occurred in 91.1% of subjects, no change occurred in 8.9%, and there was no constriction. Average diameter change was -14.4 +/- 12.1% in diabetic patients (P < 0.001 vs. control subjects), constriction occurred in 73.6%, no change occurred in 26.4%, and there was no dilation. CVEs were recorded with a mean follow-up of 45 +/- 19 months. There was 1 CVE in the control group and 26 CVEs in 18 of 72 diabetic patients (P < 0.001 vs. control subjects), with 23 events in 16 of 53 diabetic patients with coronary artery constriction (P < 0.001 vs. control subjects), and 3 events in 2 of 19 diabetic patients with no diameter change (NS vs. control subjects).

CONCLUSIONS

In type 2 diabetic patients without other major coronary risk factors, constriction of angiographically normal coronary arteries to the cold pressor test is predictive of long-term CVEs.

Predictive factors and long-term evolution of early endothelial dysfunction after cardiac transplantation

BACKGROUND

Abnormal coronary vasomotion appears to be a common finding after heart transplantation (HTx). However, the pathophysiology and outcome of this functional disturbance remains poorly understood. Aims of the study were to determine the prevalence, predictive factors and long-term evolution of endothelial dysfunction after cardiac transplantation.

METHODS

The endothelium-dependent coronary vasomotion of 50 patients, who showed angiographically normal coronary arteries, were studied early (at 3 +/- 1 months) and at follow-up (16 +/- 5 months) after HTx. Endothelial function was studied by selective infusion of serial doses of acetylcholine (ACh) (10(-8), 10(-7)and 10(-6) mol/l) in the left anterior descending coronary artery. Changes in mean luminal diameter after the infusion of each dose were evaluated by quantitative coronary angiography (QCA).

RESULTS

At early study, 17 patients (34%) showed a vasoconstriction after maximal dose of ACh (-13.3 +/- 13%) indicative of endothelial dysfunction. Logistic regression analysis identified the following variables as independent predictors of early endothelial dysfunction: donor inotropic support (p = 0.004), female donor (p = 0.04) and rejection at the time of the study (p = 0.01). Forty-one patients were re-studied at follow-up. Nine of them (22%) presented endothelial dysfunction. Early endothelial dysfunction was restored in 6 patients (43%) at follow-up. The number of episodes of rejection was the only variable associated to late endothelial dysfunction.

CONCLUSIONS

Endothelial dysfunction is a common finding after cardiac transplantation. The pathogenesis of this functional disturbance appears to be donor-related and immune-mediated. The reversibility of this phenomenon observed at follow-up suggests the episodic nature of the immunologic injury.

Effects of bradykinin on coronary blood flow and vasomotion in transplant patients

OBJECTIVES

To evaluate the effects of exogenous bradykinin on coronary epicardial and microcirculatory tone in transplant patients (HTXs), and to compare them with the effects of acetylcholine.

BACKGROUND

Coronary endothelial dysfunction has been reported to occur early after heart transplantation, most notably when acetylcholine was the endothelium-function marker used. The effects of bradykinin on coronary vasomotion are unknown in HTXs.

METHODS

Sixteen HTXs were compared 3.6 +/- 1.7 months after transplantation to seven control subjects. Coronary flow velocity was measured using guide-wire Doppler. Diameters (D) of three segments of the left coronary artery and coronary blood flow (CBF) were assessed at baseline, after 3-min infusions of increasing bradykinin doses (50, 150 and 250 ng/min) then of increasing acetylcholine doses (estimated blood concentrations of 10(-8), 10(-7) and 10(-6) M).

RESULTS

Bradykinin induced similar dose-dependent increases in D and CBF in both groups: D was 11 +/- 12%, 19 +/- 14% and 22 +/- 16% (all p < 0.0001), and CBF was 50 +/- 40%, 130 +/- 68% and 186 +/- 77% (all p < 0.0001). Acetylcholine induced significant epicardial vasodilation in control subjects and vasoconstriction in HTX, as well as a marked increase in CBF in both groups. Acute allograft rejection, present in 8 of the 16 HTXs, did not modify responses to bradykinin, but was associated with a smaller CBF increase in response to acetylcholine (p < 0.05).

CONCLUSIONS

The coronary vasodilating effects of bradykinin are preserved early after heart transplantation, even in the presence of acute allograft rejection. Although there is an abnormal vasoconstricting response to acetylcholine reflecting endothelium dysfunction, the endothelium remains a functionally active organ in heart transplant recipients.

Immunohistochemical characterization of coronary thrombi in allograft vascular disease

BACKGROUND

Coronary thrombosis is a frequent complication of allograft vascular disease (AVD) in cardiac transplant recipients. No data are available on thrombus composition in these hearts.

METHODS

The present study aimed at characterizing thrombus components in coronary arteries from transplanted hearts with AVD, using single and double immunostain with anti-gpIIb-IIIa, anti-fibrin, and anti-endothelial antibodies. The pathologic series consists of 55 grafts survived longer than 2 months, and obtained from 55 patients deceased (n=44) or undergone repeat transplantation (n=11).

RESULTS

Mural thrombi were found in multiple segments of 75 of 440 total coronary vessels (17%) (recent in 33, organizing in 28, and organized in 14), whereas occlusive thrombi were found in 19 vessels (8 recent and 11 with multichannel pattern of organization). Recent and thin mural thrombi were mostly constituted of CD41a- and CD61-positive platelets; the amount of fibrin progressively increased with the increase of thrombus size. In organizing mural thrombi, gpIIb-IIIa immunostain was still present. Fibrin was the only identifiable thrombus component in old mural thrombi embedded within the intimal lesions. Recent occlusive thrombi immunoreacted both with anti-CD41a and anti-CD61 and with anti-fibrin antibodies, whereas organized occlusive thrombi with multichannel pattern exclusively immunoreacted with anti-fibrin antibodies. Double immunostain showed that mural thrombi were stratified on de-endothelized arterial segments.

CONCLUSIONS

Thrombus composition is related to both type and "age" of thrombus, with platelets as the early and major components of mural microthrombi at one end of the spectrum, and fibrin as the dominant component of occlusive thrombi at the other end.

Absence of L-arginine effect on coronary hypersensitivity to serotonin in cardiac transplant recipients

Coronary hypersensitivity to serotonin promotes platelet aggregation and, therefore, the progression of the atherosclerotic process. This abnormality occurs in the early stages of coronary atherosclerosis when the responses to bradykinin are still preserved. To determine whether such changes also occur early after cardiac transplantation, intracoronary injections of bradykinin and serotonin were performed in 7 control patients, in 19 patients with dyslipidemia, and in 15 cardiac transplant recipients (1 year after operation). Coronary angiography was normal in the 3 groups. In the segments where serotonin effects were the most pronounced, the diameter changes were measured by quantitative angiography. Bradykinin (60, 200, and 600 ng) increased in the same way as the coronary diameters in the 3 groups; in contrast, serotonin elicited vasodilation only in the control group (7+/-3%, percentage of baseline) and vasoconstriction in the hyperlipidemic group (-9+/-2%) and in transplant recipients (-15+/-3%). After intracoronary infusion of L-arginine (40 mg/min for 14 minutes), serotonin-induced constriction was attenuated in the hyperlipidemic group but not in transplant recipients. Thus, the response to bradykinin is preserved in the early stages of graft vasculopathy. However, in contrast to patients with hyperlipidemia, the absence of an L-arginine effect on the responses to serotonin suggests the involvement of mechanisms other than a decrease in endothelium-derived nitric oxide availability. Immune processes promoting the release of endothelium-derived contracting factors such as endothelin and/or superoxide anion may play a role.

Current concepts of coronary flow reserve for clinical decision making during cardiac catheterization

Measurements of coronary flow reserve, once used only for research, have gained wide acceptance as an additional diagnostic approach in the decision-making process of diagnostic cardiac catheterization and coronary interventions. Apart from the noninvasive determination of coronary flow reserve, intracoronary Doppler flow wires have facilitated decision making in the catheterization laboratory. Different techniques, unstandardized procedures, and data from uncomparable patient populations have remained a confounding factor. This review examines current concepts of coronary flow reserve as well as methodologic considerations and pitfalls. Applications of coronary flow reserve for periinterventional assessment are evaluated on the background of practical guidance. According to a detailed examination of arterial structure and function, a normal coronary flow reserve exceeds a value of 3.0. Values below 3.0 suggest involvement of microvascular disease caused by functional or structural alterations. The influences of various factors such as age, hemodynamics, hypercholesterolemia, hypertrophy, hypertension, syndrome X, and coronary artery disease are discussed in relation to the effect on coronary flow reserve. From available information, measurements of coronary flow reserve are an adjunct to current interventional technology to optimize individual patient care. Further efforts should be undertaken to incorporate these new methods into our routine clinical decision making.

Role of nitric oxide in coronary vasomotion during handgrip exercise

BACKGROUND

Endothelium-dependent modulation of coronary vasomotion during increased sympathetic tone remains unclear in normal and atherosclerotic human coronory arteries.

METHODS AND RESULTS

We evaluated the role of endothelium-derived nitric oxide in vasomotion during isometric exercise in normal subjects (n = 7) and in patients with coronary artery disease (CAD) (n = 10). Coronary blood flow and epicardial coronary artery diameter to the handgrip test were measured before and after intracoronary administration of 100 micromol/min of N(G)-monomethyl L-arginine (L-NMMA). Heart rate and aortic blood pressure increased during handgrip test. Handgrip test caused a significant dilation in the diameter of the epicardial coronary artery in normal subjects (9.9% +/- 3.9%, mean +/- SD) and in the diameter of smooth segments of patients with CAD (5% +/- 3.7%, p < 0.05 vs normal subjects). In contrast, the diameter of irregular segments in patients with CAD decreased during handgrip test (-9.8 +/- 3.9%). After L-NMMA, the epicardial coronary artery significantly increased during handgrip test compared with before L-NMMA in normal subjects. L-NMMA did not have any effect on handgrip test induced vasodilation in the smooth segments and vasoconstriction in the irregular segments in the patients with CAD. Handgrip test-induced increases in coronary blood flow did not change after L-NMMA in both groups.

CONCLUSIONS

Nitric oxide does not play a major role in HNG-induced vasodilation in epicardial and microcirculatory vessels in normal human coronary circulation. Although the decreased release in nitric oxide may modulate the abnormal response of the epicardial coronary artery to handgrip test, this does not explain the paradoxic constrictive response from the depressed but still dilatory response in the patients with CAD.

[Heart transplantation--state of the art today]

In spite of pharmacological progress, end stage congestive heart failure is still associated with a decrease in quality and expectation of life. Heart transplantation remains the last therapeutic option for these patients. While the one year survival rate has increased over the last few years up to 84%, a major problem remains the significant lack of donors. Therefore, the criteria for the selection of candidates for cardiac transplantation have to be kept quite tight: Evidence of poor outcome without transplantation is associated with ejection fractions below 20 to 25%, cardiac indices less than 2.01/min/m2, left ventricular filling pressure above 20 mm Hg and a enddiastolic diameter of > 80 mm. There are, however, also quite important functional parameters indicating the need for heart transplantation, e.g. the maximal oxygene uptake being less than 10 ml/kg/min or below 50% of the age-appropriate value. Elevated pulmonary vascular resistance above 4 to 5 Wood units without a significant decrease during application of prostaglandin derivatives or inhalation of NO represents a contraindication for orthotopic heart transplantation; alternatively, a heterotopic transplantation can be considered. Since there is a significant shortage of suitable donor organs, the donor criteria have been broadened, e. g. the accepted donor age was increased to 60 years. Based on these extended criteria, a careful donor evaluation including cardiac history, cardiac examination, ECG and echocardiogram has to be performed. Coronary angiography in older donors is suggested, but in many cases not possible due to circumstances. Further precondition for a good graft function is a sophisticated donor management until the time of explantation. Hypovolemia and hypocalemia, hypothermia, hypoxia and rapid lost of circulating triiodothyronine (T3) have to be detected and balanced. The cardioplegic solution used might not only have an impact on the immediate postoperative performance of the graft, but also on the long term outcome, particularly with regard to graft vessel disease. There are generally two types of solutions: Those with intracellular and those with extracellular electrolyte concentrations. In addition, the potassium concentration might be of some importance. Potassium seems to damage endothelial cells and trigger subsequent immunological reactions. Therefore, high potassium concentrations in the cardioplegic solution might correlate with the incidence of graft vessel disease during the long term follow-up. The surgical technique for orthotopic heart transplantation developed at the beginning of the sixties by Lower and Shumway has been used unchanged for the last 30 years. The only alteration recently introduced is the separate direct anastomosis of the pulmonary and systemic veins in order to improve the atrial function. Until recently the commonly employed immunosuppressive strategy after heart transplantation consisted of the standard drugs cyclosporin, azathioprin and prednisolon. Some transplant-units use additionally induction therapy with antibody preparations. Many centers, however, abolished this regimen due to significant short and long term side effects. Promising new, more specific antibodies (which are chimerized or humanised) could revive the induction concept. The most thoroughly tested novel immunosuppressive agent is tacrolimus (FK506). It has been demonstrated to be 10 to 100 times more potent than cyclosporin A in in vitro and in vivo models. It binds to a different binding protein (FK-binding-protein) than cyclosporin (cyclophilin), but has a similar mechanism of action inhibiting the expression of T-cell-activator genes for certain cytokines. First non-randomised studies after heart transplantation performed at the University of Pittsburgh revealed that significantly more tacrolimus than cyclosporin patients were free of rejection. In order to confirm these observations, we performed a prospective randomised controlled clin

Variations of segmental endothelium-dependent and endothelium-independent vasomotor tone after cardiac transplantation (qualitative changes in endothelial function)

Endothelial dysfunction is a common phenomenon after cardiac transplantation. However, qualitative differences in endothelial vasoregulation at different coronary segments and at different postoperative times have rarely been explored. To uncover the functional variations of endothelium responses we infused the endothelium-dependent vasodilator acetyl-choline (50 micrograms) followed by the endothelium-independent vasodilator 3-morpholinosydnonimine (SIN-1) (1 mg; 16 patients) or nitroglycerin (0.3 mg; 14 patients) sequentially into the left coronary artery. We investigated the responses of 120 nonstenotic coronary segments (proximal and distal left anterior descending and right circumflex coronary arteries) in 30 patients with quantitative angiography (group 1: 13 patients, 12 +/- 1 months after cardiac transplantation; group 2: 17 patients, 55 +/- 3 months after cardiac transplantation). Continuous-flow measurement was performed to exclude significant reduction of microvascular response influencing epicardial dilation. Five responses to acetylcholine administration followed by nitrates were observed. On the one end of the spectrum, segments dilate to acetylcholine administration with no further dilation to exogenous nitric oxide, indicating completely preserved endothelial function. On the other end, segments constrict to acetylcholine with no change after endogenous nitric oxide, reflecting a defective endothelial and defective smooth muscle function. The different patterns of coronary vasomotor lone responses to endogenous nitric oxide followed by exogenous nitric oxide represent different degrees of endothelial function after cardiac transplantation. In addition, the functional assessment of endothelial integrity shows qualitative time-dependent differences between proximal and distal coronary parts. The existence of coronary segments with functioning endothelium indicates that the latter is not diffusely disturbed in all cardiac transplant recipients and that the endothelial damage is perhaps not irreversibly lost.

Reduced coronary flow reserve during exercise in cardiac transplant recipients

BACKGROUND

Coronary flow reserve (CFR) is reduced in a majority of patients after heart transplantation (HTx). Pharmacological interventions, however, provide only limited information on CFR under physiological conditions. Thus, CFR during exercise was evaluated in the present study.

METHODS AND RESULTS

Coronary angiography was performed at rest and during supine bicycle exercise in 35 patients early (2 to 3 months; n = 10) or late (1 to 6 years; mean, 2.5 years; n = 25) after HTx and in 8 controls (C). CFR was determined by parametric imaging after administration of 10 mg intracoronary papaverine, during exercise, and after 1.6 mg sublingual nitroglycerin. Epicardial coronary artery size was measured by quantitative coronary angiography. CFR after papaverine was normal early (3.6 +/- 0.5 versus C, 3.6 +/- 0.7; P = NS) and late (3.8 +/- 1.3 P = NS) after HTx. During exercise, CFR was normal early (3.1 +/- 0.6 versus C, 3.9 +/- 0.9; P = NS) but decreased late (2.3 +/- 0.6; P < .01) after HTx. The increase in coronary cross-sectional area during exercise was also diminished late after HTx (14 +/- 10% versus C, 22 +/- 10%; P < .05). Both exercise-induced CFR (r = -.39, P < .05) and coronary vasodilation (r = -.44, P < .01) were inversely correlated with time after HTx.

CONCLUSIONS

CFR during exercise is normal early but reduced late after HTx, whereas CFR after papaverine administration is maintained. This difference between physiological and pharmacological vasodilation suggests progressive endothelial dysfunction after HTx.

Sympathetic stimulation overrides flow-mediated endothelium-dependent epicardial coronary vasodilation in transplant patients

BACKGROUND

Abnormal coronary vasomotor responses have been described in transplant patients. The aim of this study was to evaluate the graft epicardial vasomotor responses to different stimuli that increase coronary blood flow.

METHODS AND RESULTS

Twelve heart transplant recipients with angiographically normal epicardial coronary arteries were compared 2.7 +/- 1.2 months after surgery with 6 control subjects. Coronary flow velocity was measured with a guidewire Doppler. Coronary diameter changes of the proximal and midportion of the left anterior descending coronary artery were assessed by quantitative coronary angiography during rapid atrial pacing, cold pressor test, supine exercise, and subselective infusion of papaverine and after intracoronary injection of linsidomine (SIN-1). Catecholamine plasmatic levels were determined at the different stages of the protocol. In 6 other transplant patients, a cold pressor test was performed before and after intracoronary infusion of phentolamine (10 micrograms.kg-1.min-1). Coronary flow velocity increased significantly in both groups during each phase of the protocol. In control subjects, dilation was observed in response to atrial pacing (8.7 +/- 7.6%; P < .05), CPT (8.8 +/- 2.3%; P < .01), exercise (14.5 +/- 9.4%; P < .001), and papaverine infusion (14.2 +/- 6.1%; P < .001) and after injection of SIN-1 (26.8 +/- 11.9%; P < .001). In transplant patients, similar dilation was observed during atrial pacing (8.2 +/- 8.3%; P < .05) and papaverine infusion (14.6 +/- 7.8%; P < .001) and after SIN-1 (25.8 +/- 10.8%; P < .001). CPT and exercise caused slight constriction (-3.5 +/- 4.5% and -2.7 +/- 10.5%, respectively; both P < .001 versus control subjects). Norepinephrine plasmatic levels increased in both groups during CPT and exercise. Slight constriction during the cold pressor test (-4.5 +/- 9.6%) changed to dilation (6.8 +/- 7.0%) after alpha-blockade with phentolamine (P < .001).

CONCLUSIONS

These results show that flow-mediated, endothelium-dependent vasodilation is preserved early after trans-plantation. Sympathetic stimulation, which overrides the endothelium-dependent mechanism, can be related to hypersensitivity to catecholamines due to denervation.

Time course of endothelial function in epicardial conduit coronary arteries and in the microcirculation in the long-term follow-up after cardiac transplantation

BACKGROUND

Endothelial dysfunction has been reported in epicardial conduit coronary arteries and in the microcirculation after cardiac transplantation. It has been assumed that endothelial dysfunction may precede hemodynamically relevant transplant vasculopathy. In this study the long-term course of endothelial function was investigated in conduit coronary arteries and in the microcirculation after cardiac transplantation.

METHODS

Patients were stratified according to time after transplantation (group I, up to 2 years after transplantation; group II, 2 to 4 years after transplantation; group III, more than 4 years after transplantation). Changes of the diameter of proximal, mid and distal segments of the left anterior descending coronary artery and the circumflex branch of the left coronary artery were investigated after endothelium-dependent and endothelium-independent stimulation with acetylcholine (ACh, 50 and 100 micrograms i.c.) and nitroglycerin 0.3 mg i.c. Coronary flow changes were assessed endothelium-dependently (ACh 50 and 100 micrograms i.c.) and endothelium-independently (dipyridamole 0.56 mg/kg i.v.) utilizing an 8 F Judkins-style Doppler catheter.

RESULTS

Application of 50 micrograms/100 micrograms ACh resulted in a reduction of coronary artery diameter in proximal, mid and distal vascular segments of the left anterior descending coronary artery and the circumflex branch of the left coronary artery. The vasoconstrictive effect did not differ significantly between groups I,II and III. Nitroglycerin 0.3 mg i.c. increased coronary artery diameters in groups I, II and III. ACh (50 micrograms/100 micrograms) increased coronary flow index by 217 +/- 70%/236 +/- 110% (P < 0.05 vs. baseline) in group I, 113 +/- 26%/77 +/- 22% (P < 0.05 vs. baseline) in group II and 108 +/- 26%/109 +/- 21% (P < 0.05 vs. baseline) in group III. Dipyridamole increased coronary flow index by 296 +/- 78% (P < 0.05 vs. baseline) in group I, by 63 +/- 16% (P < 0.05 vs. baseline and vs. group I) in group II and by 113 +/- 30% (P < 0.05 vs. baseline and vs. group I) in group III.

CONCLUSION

A constant vasosonstrictor response to ACh was observed in epicardial coronary arteries after cardiac transplantation indicating endothelial dysfunction independent of the time course. Endothelial dysfunction in these vessels may not be an early indicator of hemodynamically relevant transplant vasculopathy. Endothelium-dependent and endothelium-independent flow reserves decreased 2 years after transplantation and remained constant thereafter.

Vagal modulation of epicardial coronary artery size in dogs. A two-dimensional intravascular ultrasound study

BACKGROUND

Because the role of tonic vagus nerve activity in regulating conduit coronary artery size remains undefined, we investigated the response of epicardial coronary artery size to changes in resting vagal tone resulting from vagotomy and muscarinic receptor blockade.

METHODS AND RESULTS

Using intravascular ultrasound to measure left circumflex coronary artery cross-sectional area continuously, we examined the effects of vagotomy on left circumflex cross-sectional area in nine dogs. Lumen area decreased 20% from 8.70 +/- 2.81 to 6.92 +/- 1.97 mm2 after right vagotomy, 17% to 7.19 +/- 2.80 mm2 after left vagotomy (both P < .05 versus baseline), and 38% to 5.42 +/- 2.00 mm2 after bilateral vagotomy (P < .05 versus unilateral vagotomy). Vasoconstriction occurred despite increases in heart rate and an unchanged rate-pressure product. In six additional dogs, after acetylcholine (100 micrograms/kg i.v.), lumen area increased by 18%, although heart rate, blood pressure, and rate-pressure product were unchanged. Vasodilation was prevented by prior muscarinic blockade with glycopyrrolate. With glycopyrrolate administration and heart rate control by pacing, lumen area decreased by 26% (P = .011). When stellate stimulation was performed in a third group of eight dogs with heart rate, blood pressure, and rate-pressure product controlled by a combination of pacing and exsanguination, there was no change in coronary area, thus precluding reflex sympathetic activation as a contributor to the vasoconstriction produced by vagal withdrawal.

CONCLUSIONS

Vagus nerve activity maintains tonic dilation of the left circumflex coronary artery by muscarinic receptor activation. Each vagus nerve contributes approximately equally to the tonically dilated state. Vagotomy-induced vasoconstriction occurs independently of local metabolic factors and coronary distending pressure and is a result of cholinergic withdrawal rather than reflex sympathetic activation.

Coronary artery response to cold-pressor test is impaired early after operation in heart transplant recipients

OBJECTIVES

The aim of the present study was to evaluate the coronary vasomotor response to the cold-pressor test within 3 months after heart transplantation.

BACKGROUND

Normal epicardial coronary arteries dilate in response to sympathetic stimulation evoked by the cold-pressor test. In transplant recipients, abnormal coronary vasomotion has been described shortly after operation.

METHODS

Fourteen heart transplant recipients were compared 52 +/- 15 days (mean +/- SD) after operation with 10 control subjects. All had angiographically normal epicardial coronary arteries. Coronary blood flow velocity was measured with a Doppler catheter placed in the proximal left anterior descending coronary artery. Four segments in each patient were analyzed by quantitative coronary angiography to assess the diameter changes during the cold-pressor test and after intracoronary injection of isosorbide dinitrate.

RESULTS

Coronary flow velocity increased similarly during the cold-pressor test in control subjects and in transplant recipients, from 7.5 +/- 2.3 to 11.0 +/- 3.9 cm/s and from 10.3 +/- 3.2 to 13.7 +/- 4.8 cm/s (both p < 0.01). In control subjects, 39 of 40 segments analyzed dilated during the cold-pressor test. In transplant recipients, 48 of 56 segments analyzed did not change or constricted. The mean epicardial coronary diameter increased significantly during the cold-pressor test in control subjects (+13 +/- 6%, p < 0.001), whereas it did not change significantly in transplant recipients (-2 +/- 9%, p = NS). In transplant recipients, isosorbide dinitrate elicited coronary vasodilation similar to that in control subjects.

CONCLUSIONS

These data indicate that in human transplanted denervated hearts, coronary vasodilation in response to sympathetic stimulation by cold exposure is impaired shortly after operation.

Assessment of transplant arteriopathy by intracoronary two-dimensional ultrasound imaging and coronary flow velocity

Transplant coronary arteriopathy is the major impediment to the long-term survival of cardiac allografts. This report highlights two-dimensional imaging and Doppler flow to assess transplant coronary arteriopathy.

Immunosuppressive agents and endothelial repair. Prednisolone delays migration and cytoskeletal rearrangement in wounded porcine aortic monolayers

Endothelial denudation at areas of predilection to atherosclerosis is balanced by an active repair process that may be inhibited under conditions of accelerated atherosclerosis. After cardiac transplantation, the accelerated atherosclerotic process that develops may be enhanced by immunosuppressive agents that have nonspecific effects on cell signaling, proliferation, and response to injury. To study subtle effects of cyclosporine A, azathioprine, and 6 alpha-methylprednisolone on normal endothelial repair processes, confluent porcine endothelial monolayers were denuded in the presence of clinically relevant concentrations of these agents. The rate of endothelial wound repair was compared and the effects on cell spreading, proliferation, and the cytoskeleton assessed. 6 alpha-Methylprednisolone at concentrations of 1.25 to 50 mumol/L was associated with a transient 30% to 60% inhibition of endothelial wound repair. This was associated with increased cell size at the wound edge and a delay in centrosomal reorientation toward the wound, without any effect on cell proliferation. Cyclosporine and azathioprine in clinically relevant concentrations did not affect endothelial repair. Thus, corticosteroids transiently inhibit endothelial cytoskeletal alterations that are important in endothelial repair after a denuding injury.

Plasma endothelin and early coronary endothelial dysfunction in recipients of a cardiac transplant

Serotonin constricts coronary arteries with endothelial dysfunction, possibly through reduced endothelial release of nitric oxide or enhanced production of constricting factors such as endothelin. Because the plasma levels of this peptide are increased in the early months after cardiac transplantation, we assessed whether a coronary hypersensitivity to the vasoconstrictor effect of serotonin is associated with high plasma endothelin levels. One to 3 months after cardiac transplantation, serotonin (1, 10, or 20 micrograms/min for 2.5 min each) was infused into the coronary circulation in 32 patients. Changes in coronary diameters were determined by quantitative angiography. A > or = 40% reduction in coronary diameter for a dose of serotonin < or = 10 micrograms/min was observed in group A (n = 14) whereas in group B (n = 18), this diameter reduction was never reached even for a 20 micrograms/min infusion of serotonin. Plasma endothelin levels were significantly higher (p < 0.01) in the coronary ostium and coronary sinus in group A, at 23.4 +/- 1.3 pg/ml and 24.9 +/- 0.9 pg/ml versus 12.6 +/- 0.9 pg/ml and 13.8 +/- 1.1 pg/ml, respectively, in group B. These endothelin levels did not significantly change after intracoronary infusion of serotonin. A significant correlation was found between plasma endothelin levels in the coronary ostium and peak coronary constriction (percentage diameter reduction) in both groups (r = 0.77 for group A and r = 0.92 for group B). Thus, early after cardiac transplantation, serotonin-induced coronary constriction is a common finding, and the severity of this abnormality seems to be influenced by plasma endothelin levels.

Early impairment of acetylcholine-induced endothelium-dependent coronary vasodilation is not predictive of secondary graft atherosclerosis

STUDY OBJECTIVE

To test the hypothesis that the magnitude of early constriction of coronary arteries to acetylcholine might be a useful predictor of secondary graft atherosclerosis.

DESIGN

The responses of epicardial coronary arteries to stepwise intracoronary infusion of acetylcholine (10(-8)M to 10(-5)M) were compared in 7 control subjects and in 18 patients who had undergone transplants within 2 months after surgery.

MEASUREMENTS AND RESULTS

Vessel dimensions (percent basal diameter) were measured by quantitative angiography. Follow-up at 1 year showed angiographically normal coronary arteries in 12 patients (group 1) and coronary atherosclerosis in 6 patients (group 2). In control subjects, acetylcholine induced a dose-dependent dilation from 10(-8)M to 10(-6)M. No significant variation was observed at 10(-5)M. In patients with transplants early after surgery, diameters did not vary significantly from base at 10(-8)M in either group and constricted significantly at higher concentrations. Vasodilator responses to intracoronary isosorbide dinitrate were similar in both groups with transplants early after surgery, and at 1 year in group 1, but significantly lower than in control subjects.

CONCLUSIONS

In patients who had undergone transplants, acetylcholine-induced endothelium-dependent coronary artery dilation is similarly impaired early after surgery (within 2 months) in patients with and without coronary atherosclerosis at 1-year follow-up. Thus, response to acetylcholine is not a predictor of secondary atherosclerosis in patients with heart transplants.

Loss of flow-dependent coronary artery dilatation in patients with hypertension

BACKGROUND

Abnormal endothelium-dependent coronary response to acetylcholine has been shown in patients with essential hypertension. We tested the hypothesis that flow-dependent dilatation, which has been shown in normal human coronary arteries, is impaired in hypertensive patients.

METHODS AND RESULTS

The coronary vasomotor response to maximal increase of blood flow induced by papaverine was studied in 10 control subjects and in 14 hypertensive patients with no other risk factors and angiographically normal coronary arteries. After the injection of papaverine in the midportion of the left anterior descending coronary artery (LAD), the diameter of the proximal LAD (LAD1) was measured by quantitative angiography, whereas that of the proximal circumflex artery (LCx) served as control segment. Estimates of coronary blood flow in the distal LAD (LAD2) were calculated by intracoronary Doppler flow velocity measurements. An increase in LAD2 blood flow of 521 +/- 41% (P < .001) in control subjects was associated with a 17.0 +/- 3.3% dilatation of the LAD1 (P < .001) and with no significant change in the diameter of the LCx. In hypertensive patients, despite a comparable increase in LAD2 blood flow of 406 +/- 32% (P < .001), the LAD1 failed to dilate (-0.4 +/- 0.6%, NS). The dilative response to isosorbide dinitrate was similar in control subjects and hypertensive patients (30.0 +/- 4.1%, P < .001 and 21.9 +/- 1.9%, P < .001, respectively).

CONCLUSIONS

Thus, the flow-mediated coronary dilatation is lost in hypertensive patients, and this may impair normal dilatation observed in response to an increase in myocardial metabolic demand.

Coronary artery constriction caused by the cold pressor test in human hypertension

Hypertensive patients with angiographically normal coronary arteries may have myocardial ischemia when metabolic demand increases. Abnormal epicardial coronary artery vasomotion in response to sympathetic stimulation may contribute to ischemia in such patients. We studied the vasomotor response of smooth coronary arteries to a cold pressor test in 10 hypertensive patients without other risk factors and in 9 control subjects. Vessel dimensions were measured by quantitative angiography, and blood flow was calculated using an intracoronary Doppler catheter in the left anterior descending coronary artery. In response to cold pressor stimulation, arteries of control subjects dilated 13.0 +/- 5.9% (P < .001), and they constricted 8.2 +/- 8.5% in hypertensive patients (P < .001). Rate-pressure product increased from 9466 +/- 1677 to 12,547 +/- 2367 beats per minute (bpm).mm Hg in control subjects (P < .001) and from 13,720 +/- 1823 to 17,353 +/- 2037 bpm.mm Hg in hypertensive patients (P < .001). Coronary blood flow velocity and blood flow increased 51 +/- 26% (P < .05) and 87 +/- 27% (P < .001), respectively, in control subjects and 68 +/- 52% (P < .05) and 36 +/- 33% (P < .01) in hypertensive patients. At peak cold pressor test, despite a significant higher rate-pressure product in hypertensive patients, blood flow was similar in both groups, suggesting an uncoupling between myocardial metabolic demand and supply. Thus, hypertension impairs the vasodilator response of angiographically normal coronary arteries to a cold pressor test. This abnormal response may be due to enhanced catecholamine reactivity and/or impairment of endothelial flow-mediated vasodilator response.