Intragraft heme oxygenase-1 and coronary artery disease after heart transplantation

Peri-operative tissue injury triggers the development of Transplant Coronary Artery Disease (TCAD). Animal studies have shown that induction of heme oxygenase (HO)-1 protects the donor organ from the development of TCAD. To investigate the role of HO-1 in TCAD after clinical heart transplantation, we measured intragraft mRNA expression of HO-1, HIF-1alpha, TGF-beta, FLIP, and the Bcl-2/Bax balance. Immunohistochemical staining of HO-1 was performed to determine its origin. Myocardial biopsies taken at the end of the transplantation procedure (time 0), at 1 week and at 10 months after transplantation were studied from recipients with or without angiographic signs of accelerated TCAD, diagnosed after 1 year. At time 0, no differences in mRNA expression for any of the measured parameters were found between TCAD positive and negative patients. At 1 week, mRNA expression of HO-1 and TGF-beta was higher in grafts that developed accelerated TCAD (p=0.001 and p=0.0002). These higher mRNA levels were accompanied by a pro-apoptotic shift in Bcl-2/Bax (p=0.02), suggesting proneness for apoptosis via the mitochondrial pathway. Immunohistochemical staining showed that HO-1 was mainly produced by infiltrating macrophages. At 10 months, again HO-1 and TGF-beta levels were high in TCAD positive patients (p=0.02 and p=0.05), but the expression of apoptotic markers was comparable at this time point. Our results suggest that a higher HO-1 by macrophages in our patient population might be an adaptive response to tissue injury and inflammation, reflecting damage due to the transplantation procedure that finally results in TCAD.     

Coronary flow reserve is impaired early after cardiac transplantation

The highest mortality rate after cardiac transplantation, at present, occurs within the first year after cardiac transplantation. The state of the coronary microcirculation soon after cardiac transplantation has not been previously assessed. We investigated the hypothesis that coronary flow reserve (CFR) is impaired in the early postoperative period after cardiac transplantation. A 3F intracoronary Doppler flow probe was inserted into the left anterior descending coronary artery and maximal coronary flow was assessed using the non-endothelial-dependent vasodilator papaverine. We compared two groups of patients: group A — 13 patients studied 3 months after operation; and group B — 25 patients studied at a median of 4 years after operation (range 2–8 years) without coronary occlusive disease (COD). CFR was defined as the quotient of maximum hyperaemic to resting velocity (vel). CFR was markedly impaired in group A patients compared with group B (3.3 SEM 0.3 versus 4.2 SEM 0.2, P < 0.01). No significant differences between mean resting or peak velocities, original diagnosis, age, active rejection, blood pressure, lipid levels, ischaemic time, cyclosporin levels or cytomegalovirus (CMV) status were noted. Responses to papaverine in resistance coronary vessels are impaired in the early postoperative period after cardiac transplantation. This is caused by a combination of higher resting flow and lower peak flow in the early group. This impairment of function in the coronary microcirculation may contribute to early graft dysfunction and reflect changes in vascular smooth muscle function leading to the development of COD.     

Injury of the coronary endothelium at implantation increases endothelial dysfunction and intimal hyperplasia after heart transplantation.

BACKGROUND: Coronary endothelial dysfunction occurs early after heart transplantation and predicts the development of intimal thickening characteristic of cardiac allograft vasculopathy. OBJECTIVES: To assess the effects of removal of the endothelium by balloon injury of coronary arteries of allografts without rupture of the internal elastic lamina at the time of implantation and on coronary endothelial dysfunction, and to assess the development of accelerated atherosclerosis after heart transplantation. METHODS: A porcine model of heterotopic heart transplantation with preoperative immunologic typing, enabling progressive rejection without immunosuppression, was used to study the effect of endothelial removal on these 2 end points. Endothelium-dependent relaxations of epicardial coronary arteries from allografts submitted to endothelial denudation after harvest, arteries from allografts not undergoing denudation, and native coronary arteries were compared 30 days after graft implantation by using standard organ chamber experiments. Intimal thickening was measured by light microscopy with a semiquantitative scale (0 to 4+ grading). RESULTS: Relaxations to serotonin and to bradykinin were significantly decreased in denuded arteries compared with nondenuded allograft arteries. There was a significant increase in the incidence of severe intimal hyperplasia in denuded arteries compared with nondenuded arteries, which were both significantly increased compared to native coronary arteries. CONCLUSIONS: Endothelial injury at implantation worsens the endothelial dysfunction as a result of rejection after heart transplantation and compounds the intimal thickening leading to cardic allograft vasculopathy. All efforts should be deployed to maintain a morphologically intact and functional endothelium at the time of graft implantation.     

Hemodynamic effects of endothelin-1 and big endothelin-1 in chronic hemodialysis patients

Increased plasma concentrations of endothelin-1 (ET-1) and big endothelin-1 (big ET-1) have been reported in patients with end-stage renal failure (ESRD). In the present study, which included hemodialysis (HD) patients with (n = 21) and without (n = 32) ischemic heart disease, the putative association between plasma levels of ET-1 and big ET-1 and ischemic heart disease and the influence of the dialysis procedure on ET concentrations was investigated. This study also examined in an additional five HD patients without cardiac disease whether intravenously infused ET-1 and big ET-1 (0.2, 1, and 4 pmol/kg per min, each dose for 20 min) preserve their vasoactive potency and whether exogenous big ET-1, which in healthy humans is converted in the kidney, is still converted to ET-1 in ESRD. HD patients with ischemic heart disease demonstrated higher plasma levels of ET-1 and big ET-1 than HD patients without this disorder, and HD reduced plasma ET-1 and big ET-1 concentrations. In HD patients, the big ET-1 infusion, resulting in a 1.5-fold increase in plasma ET-1, caused a more marked and prolonged rise in mean arterial BP than ET-1 (20% versus 13%, P = 0.0001) and a slightly smaller but more prolonged decrease in estimated splanchnic blood flow than ET-1 (37% versus 44%, P = 0.02). Furthermore, big ET-1 lowered heart rate by 9% (P = 0.01) but ET-1 did not. Plasma half-lives of ET-1 and big ET-1 were longer in HD patients than in healthy humans. Thus, ET-1 and big ET-1 preserve their vasoactive potency, and circulating big ET-1 is still converted to active ET-1 in ESRD. Consequently, the increased plasma levels of ET-1 and big ET-1 noted in HD patients, especially in patients with ischemic heart disease, might play a role in the development of uremic cardiovascular complications.     

Coronary flow reserve and nitric oxide synthases after cardiac transplantation in humans

Objective: Coronary endothelial dysfunction may precede morphological changes in both the epicardial conduit and microvascular resistance vessels in heart transplant recipients. Since the development of transplant atherosclerosis is the major limiting factor for long-term survival, the identification of early mediators of vasomotor dysfunction may be of therapeutic interest. We therefore investigated the potential relationship between the expression of nitric oxide synthases (NOS) and coronary endothelial function in human cardiac transplant recipients over time. Methods: Forty-two human cardiac transplant recipients were studied at 1 and 12 months after heart transplantation (HTx). The microvascular coronary flow velocity reserve (CFVR) was tested for endothelium-dependent (acetylcholine) and -independent (adenosine) stimuli by intravascular Doppler flow-wire. Epicardial diameter changes were evaluated by quantitative coronary angiography. Endomyocardial inducible (iNOS) and endothelial constitutive nitric oxide synthase were determined by RT-PCR. Nitric oxide production (nitrite and nitrate (NOx)) and TNF- were measured in plasma samples from the aorta and coronary sinus. Results: CFVR was impaired in 26.1% (n=11) of patients at 1 month and in 31% (n=13) 12 months after HTx. iNOS-mRNA levels were significantly higher in patients with impaired endothelium-dependent CFVR. In addition, only in these patients were TNF- levels higher and these correlated with plasma NOx levels at 1 and 12 months post-HTx (1 month: r=0.81, P=0.001; 12 months: r=0.62, P=0.04). Conclusions: Coronary microcirculatory dysfunction in response to acetylcholine is present in nearly 30% of patients during the first year following transplantation. These patients present with higher iNOS-mRNA expression and TNF- plasma levels. Selective modulation of the TNF-/iNOS-pathway may be of therapeutic value to improve coronary endothelial dysfunction in cardiac transplant recipients.     

Beating heart coronary artery bypass surgery after orthotopic heart transplantation

Beating-heart coronary artery bypass surgery was performed in a 52-year-old man with accelerated transplant coronary artery disease 10 years after orthotopic heart transplantation. Transplant coronary artery disease was first detected in the left circumflex coronary artery 9 years after transplantation. Rapid progression to triple vessel disease occurred within 1 year, and the patient developed worsening symptoms of shortness of breath and chest pain. He underwent off-pump "beating heart" left internal mammary artery to left anterior descending coronary artery bypass surgery. The circumflex coronary artery was not graftable due to diffuse and truncated small vessel disease. His postoperative course was uneventful and he was discharged on the fifth postoperative day. Coronary angiography 3 months after the surgery revealed a widely patent left internal mammary artery to left anterior descending artery bypass. He is alive and symptom free more than 1 year after his surgery.     

Inhibition of graft coronary arteriosclerosis after heart transplantation

Graft coronary arteriosclerosis (GCA) is the leading cause of long-term mortality after heart transplantation (HTx). The goal of this study was to demonstrate that inhibition of immunemediated injury by cyclosporine (CsA) protects the allograft from GCA. ACI-to-Lewis rat allografts were disparate in major and nonmajor histocompatibility loci. Isografts (Lewis-Lewis) were controls. Treatment groups received either olive oil or CsA at 2.5, 5, 10, or 20 mg/kg/day for 3 months. Histology (elastin) and immunohistochemistry using monoclonal antibodies to CD4, CD8, CD45R, RT1B, CD11b/c, CD25, and alpha-actin was performed to examine the epicardial and intramyocardial coronary arteries. Computerized image morphometry was utilized to measure intimal and medial thickness and area. Rats receiving olive oil or CsA at 2.5 mg/kg/day had severe rejection and no graft survival. CsA at 5 mg/kg/day resulted in less severe rejection with significant intimal and medial proliferation (P < 0.001). CsA at 10-20 mg/kg/day paralleled Lewis-Lewis isograft outcomes and inhibited arteriosclerotic vascular changes in the allograft (P < 0.001). Perivascular T-helper cells and macrophages were a characteristic finding with low-dose CsA but rare with higher CsA doses. In this new model of accelerated GCA in rats, immune-mediated antigen-dependent vasculopathy as a result of inadequate immunosuppresion is fundamental in the development of GCA, which appeared equally in epicardial arteries and intramyocardial arterioles. CsA prevents GCA in a dose-dependent fashion in the rat allograft.     

Coronary flow reserve and coronary occlusive disease

The functional effects of coronary occlusive disease (COD) in cardiac transplant patients on small-resistance coronary vessels are unclear. We investigated the changes in coronary flow reserve (CFR) in response to the non-specific smooth muscle vasodilator papaverine. A 3F Doppler probe was inserted into the left anterior descending (LAD) coronary artery in 61 patients following orthotopic heart transplantation. Studies were performed in 57 males and 4 females with a mean age of 46 years (range 20–61 years). The median time from operation was 4 years (range 3 months to 10 years). Coronary blood velocity was measured at rest (RFV) and maximum hyperaemia (PFV) produced by intracoronary papaverine. Coronary flow reserve (CFR) was defined as the ratio of PFV to RFV. Minor lesions in epicardial vessels were found in 23 transplant patients. The mean percentage diameter of the most severe lesion in the coronary tree was 23% SD 3% including 12 lesions in the LAD coronary artery itself (mean 24% SD 4%). Patients with COD had an impaired CFR (2.6 SEM 0.2) compared with normals (3.9 SEM 0.2, P = 0.0003), adjusting for year after operation. Mean resting flow velocity was similar in both groups (minor COD, 6.8 cm/s SEM 1.2; normals, 7.1 cm/s SEM 0.6), but mean peak flow velocity response to papverine was reduced (16.5 cm/s SEM 2.5 versus 27.3 cm/s SEM 2.6; P = 0.007). In the presence of minor epicardial disease, coronary flow reserve in resistance vessels was reduced due to impairment of peak flow. This demonstrates that non-endothelial-dependent coronary resistance vessel vasodilatation is abnormal and may be caused by a defect in vascular smooth muscle function.     

Predictors of reduced coronary flow reserve in heart transplant recipients without angiographically significant coronary artery disease

BACKGROUND: Determination of coronary flow reserve (CFR) is increasingly used to assess the functional significance of cardiac allograft vasculopathy. Although the relation between CFR and angiographically defined vasculopathy has been studied extensively, little is known about other factors determining CFR in heart transplant recipients without significant lesions by coronary angiography. METHODS: Sixty consecutive patients were studied 0.5 to 148 months after heart transplantation with intracoronary Doppler and intravascular ultrasound. An endothelium-independent CFR< or =2.5 was defined as abnormal. Stepwise logistic regression analysis was used to identify factors (demographic data of donor and recipient, lipid profile, epicardial vessel morphology by intravascular ultrasound, left ventricular hypertrophy, acute rejection episodes, and hemodynamics) potentially associated with a reduced CFR. RESULTS: Only the presence of left ventricular hypertrophy (48% vs. 14%, P=0.007 and P=0.023, bivariate and multivariate analysis, respectively) and higher donor ages (41+/-12 vs. 29+/-11 years, P=0.002 and P=0.013, bivariate and multivariate analysis, respectively) showed an independent association with an abnormal flow reserve. CFR in patients with left ventricular hypertrophy was reduced due to higher baseline flow velocities (27+/-11 vs. 20+/-6 cm/sec, P=0.004). Furthermore, resting flow velocity increased as a function of donor age (r=0.264, P=0.047), while hyperemic flow velocity was not different. Other patient characteristics and hemodynamics did not affect CFR. CONCLUSION: The presence of left ventricular hypertrophy and higher donor ages independently contribute to a reduced CFR in patients after heart transplantation. This reduction in CFR is due to elevated baseline flow velocities rather than to a change in hyperemic flow velocities. These findings should be taken into account for the interpretation of reduced CFR values obtained by intracoronary Doppler in heart transplant recipients without angiographically overt coronary lesions.     

Impairment of coronary flow reserve and left ventricular function in the brain-dead canine heart.

OBJECTIVE: The mechanisms of cardiac dysfunction after brain death, which are thought to be mainly associated with massive catecholamine release, have not been fully elucidated, especially with respect to the coronary circulation. The aim of this study was to investigate the changes in function of the coronary artery and its contribution to hemodynamic deterioration in a canine brain death model. METHODS: Brain death was induced by rapid inflation of a subdurally placed balloon catheter. Hemodynamic measurements including assessment of left ventricular contractility using pressure-volume relations and biochemical analyses of blood samples were performed in seven dogs. Coronary flow reserve in the same brain death model was assessed by changes in coronary flow and resistance induced by administering a vasodilator directly into the coronary artery in another eight dogs. RESULTS: A hyperdynamic response was transiently observed after induction of brain death, followed by decreases in arterial pressure, cardiac output, and coronary blood flow. Parameters of left ventricular contractility as measured by pressure-volume relations had significantly deteriorated by 60 min after brain death. Percent changes in coronary flow by administration of acetylcholine and sodium nitroprusside were 272 and 209%, respectively, before brain death; these were decreased to 178 and 145% at 30 min after brain death, and to 192 and 153% at 60 min. Coronary resistance ratios were also significantly increased at 30 and 60 min after brain death. CONCLUSIONS: Impairment of coronary flow reserve was found in the brain-dead canine heart. This impaired coronary circulation may constitute a disadvantage of prevention and recovery of cardiac dysfunction after induction of brain death.     

Early alterations of myocardial blood flow reserve in heart transplant recipients with angiographically normal coronary arteries.

BACKGROUND: The evaluation of the coronary reserve provides valuable information on the status of coronary vessels. Therefore, we studied with positron emission tomography (PET) and 13N-ammonia the myocardial blood flow (MBF) reserve in heart transplant recipients free of allograft rejection and with angiographically normal coronary arteries early after heart transplantation (HTx). The MBF reserve was calculated as the ratio between MBF after dipyridamole injection and basal MBF normalized for the rate-pressure product. METHODS: Patients were studied within 3 months (group A, n = 12) or more than 9 months (group B, n = 12) after HTx. Five patients have been studied both during the early and late period after HTx. Results were compared to those obtained in 7 normal volunteers (NL). RESULTS: Group A recipients had a significantly lower dipyridamole MBF (in ml/min/100 gr of tissue) than that of group B recipients (142+/-34 vs 195+/-59, p<0.05). This resulted in a significant decrease in MBF reserve early after HTx (group A: 1.82+/- 0.33) and a restoration to normal values thereafter (group B: 2.52+/- 0.53 vs NL: 2.62+/-0.51, p = ns). Separate analysis of 5 patients studied twice is consistent with these results. CONCLUSION: This study shows that in heart transplant recipients free of allograft rejection and with normal coronary angiography, MBF reserve is impaired early after HTx. Restoration within one year suggests that this abnormality does not represent an early stage of cardiac allograft vasculopathy.     

Intimal hyperplasia and expression of transforming growth factor-beta1 in saphenous veins and internal mammary arteries before coronary artery surgery

Background

The development of fibromuscular intimal hyperplasia and subsequent graft failure remains an urgent problem in cardiac surgery. Transforming growth factor-β1 (TGF-β1) is involved in the pathogenesis of arteriosclerosis through induction of extracellular matrix proteins. We tested the hypothesis that intimal hyperplasia is already present in human saphenous veins and left internal mammary arteries before coronary artery bypass surgery and is associated with an increased expression of TGF-β1.

Methods

Forty-six segments of saphenous veins and 27 of left internal mammary arteries were collected from 50 patients undergoing coronary artery bypass surgery. Morphometric analysis was performed by microscopic computer analysis. Immunohistochemistry was performed with antibodies directed against TGF-β1, its latent binding protein (LTBP-1) and its type 2 receptor (RII).

Results

The incidence of intimal hyperplasia was significantly higher in saphenous veins (67.4%) than in mammary arteries (29.6%; p < 0.05). Saphenous veins and mammary arteries with intimal hyperplasia expressed more TGF-β1 (endothelial and intimal layers) and LTBP-1 (intimal and medial layers) when compared with corresponding vessels without hyperplasia (both groups p < 0.05). Endothelial and intimal RII expression was significantly higher in saphenous veins with intimal hyperplasia as compared with saphenous veins without hyperplasia (p < 0.05). Transforming growth factor-β1 staining in the intima correlated with the presence of an intimal hyperplasia in saphenous veins (ρ = 0.317) and mammary arteries (ρ = 0.428).

Conclusions

Local TGF-β1 expression is associated with the presence of intimal hyperplasia in the examined vessels. Preexisting intimal hyperplasia is more prevalent and serious in saphenous veins than in left internal mammary arteries, giving further explanation to the superior long-term results of left internal mammary grafts.     

缺血对移植心脏冠状血管的影响

目的 探讨缺血对移植心脏远期冠状血管的形态学影响。方法 雄性Wistar大鼠为供者和受者，建立大鼠腹部异位心脏移植模型。实验分为4组，即假手术对照组、立即移植组、供心缺血3h移植组和缺血6h移植组。每组术后均用环孢素A(CsA)灌胃20d，抗排斥反应。20d时，取出供心，观察心脏冠状血管病理改变及超微结构变化。结果 假手术对照组心脏和立即移植组的供心冠状血管内皮超微结构均无明显损害；随着供心缺血时间的延长，移植后冠脉小血管内皮细胞肿胀，冠状动脉的内皮细胞增生，内膜增厚；缺血6h移植组供心冠状血管内膜超微结构改变非常明显。结论 供心缺血可导致移植后冠状血管内皮损伤，是心脏移植术后冠状血管病理改变的重要因素。     

血管紧张素转换酶抑制剂对心脏移植后冠状血管增殖病变的影响

目的通过建立大鼠心脏移植后冠状血管增殖病变的模型,观察血管紧张素转换酶抑制剂(ACEI)对心脏移植后冠状血管增殖病变的影响。方法设立对照组、结扎组、ACEI+结扎组,观察2周后各组大鼠血液、心肌AngⅡ含量,心肌AngⅡ受体密度,及血管病理学结果。结果各组血液AngⅡ含量差异无统计学意义,结扎组心肌AngⅡ含量明显增高(17．42±5．49)fmol／mg．蛋白P<0．001比对照组,ACEI+结扎组AngⅡ含量明显下降(5．35±1．95)fmol／mg。蛋白P< 0．01比结扎组,结扎组AngⅡ受体密度增高(48．80±4．32)fmol／mg蛋白P<0．01比对照组,ACEI +结扎组内膜增生比结扎组明显减轻[内膜厚度(21．01±4．55)μm比(60．34±9．32)μm,P< 0．01)。结论心脏局部肾素-血管紧张素系统,AngⅡ及AngⅡ受体参与移植后冠状血管病变,A- CEI明显抑制移植后冠状血管病增殖变。     

Controlled initial hyperkalemic reperfusion after cardiac transplantation: coronary vascular resistance and blood flow

The coronary vascular response to controlled initial hyperkalemic reperfusion after global ischemia during cardiac transplantation was studied in 11 patients. The mean global ischemic time was 206 minutes (range, 143 to 245 minutes). All donor hearts received initial hyperkalemic crystalloid cardioplegia and subsequent oxygenated crystalloid cardioplegia during implantation. Coronary blood flow was highest during the first one to two minutes of controlled reperfusion but remained normal throughout the first ten minutes of reperfusion. Coronary vascular resistance was less than normal throughout the first ten minutes of controlled reperfusion, but there was a gradual increase throughout this period. Systemic vascular resistance remained within normal limits. The time to effective contraction was highly variable, but a greater potassium load during initial reperfusion was generally associated with a longer time to effective contraction.     

Plasma levels of endothelin-1 in patients with the hepatorenal syndrome after successful liver transplantation

The hepatorenal syndrome (HRS) is characterized by renal vasoconstriction leading to deterioration of renal function in patients with liver disease. A possible role of endothelin-1 (ET-1) in the pathogenesis of HRS has been suggested, but a correlation between ET-1 plasma levels and the development of HRS as well as the recovery from HRS following OLT has not been shown yet. We performed longitudinal measurements of ET-1 plasma levels in four groups of patients, 5 patients with HRS before and after orthotopic liver transplantation (OLT), 10 patients without HRS undergoing OLT, 20 patients with chronic renal failure but without liver disease, and 12 healthy controls. Before OLT, plasma levels of ET-1 were higher in patients with HRS (19.5 ± 8.6 ng/l, P < 0.001; n = 5) compared to patients without HRS (4.9 ± 1.1 ng/l; n = 10), normals (1.2 ± 0.18 ng/l; n = 12), and patients with chronic renal failure (2.4 ± 0.4 ng/l; n = 20). Patients with HRS compared to patients without HRS had higher levels for creatinine (2.42 ± 0.6 vs. 0.89 ± 0.05 mg/dl, P < 0.05), creatinine clearance (107 ± 9 ml/min vs. 44.6 ± 5.5 ml/min, P < 0.001), and bilirubin (11.4 ± 3.8 vs. 3.7 ± 1 mg/dl, P < 0.05) before OLT. Within one week after OLT, there was a rapid decrease in ET-1 levels in patients with HRS while creatinine and bilirubin levels decreased slower. Regression analysis revealed a weak correlation between serum creatinine and ET-1 (r = 0.192, P = 0.04) and a significant correlation between serum bilirubin and ET-1 (r = 0.395, P < 0.001). The means of the ET-1 levels decreases rapidly with improvement of liver function after OLT. Levels of ET-1 correlate with excretory liver function assessed by bilirubin. The fall in ET-1 levels preceding improvement of renal function further strengthens the concept of ET-1 being a causative factor in HRS. Received: 22 July 1999/Revised: 28 January 2000/Accepted: 11 May 2000