Endothelial dysfunction of internal thoracic artery graft in patients with chronic kidney disease

Prognostic value of pulmonary hypertension in pre-dialysis chronic kidney disease patients

BACKGROUND

Pulmonary hypertension is common in chronic kidney disease (CKD) patients. However, the prognostic value of pulmonary hypertension in Chinese predialytic CKD patients is rarely reported. We evaluated the relevant factors and prognostic value of pulmonary hypertension in CKD patients.

METHODS

This retrospective cohort study enrolled 1092 predialytic patients from The Third Affiliated Hospital of Sun Yat-Sen University from May 1st, 2011, to December 31st, 2016. Data of interest were retrieved from electronic medical records. Pulmonary hypertension was defined as pulmonary arterial systolic pressure (PASP) ≥ 35 mmHg by echocardiology. All participants were followed from the date of the first echocardiography examination. The primary endpoints were all-cause mortality and cardiovascular mortality. The secondary endpoint was end-stage renal disease (ESRD) defined as starting renal replacement therapy.

RESULTS

The prevalence of pulmonary hypertension was 15.9% in the study population. For CKD stage 1, 2, 3a, 3b, 4 and 5, the prevalence was 6.0%, 9.6%, 17.2%, 13.3%, 20.7% and 26.6%, respectively. Older age, lower left ventricular ejection fraction, anemia and higher pulse pressure were independently associated with pulmonary hypertension in CKD patients. In multivariate Cox regression analysis, pulmonary hypertension was the independent risk factor for cardiovascular mortality, but not of all-cause mortality and ESRD.

CONCLUSIONS

Pulmonary hypertension is not rare in early CKD patients. Patients with older age, anemia, higher pulse pressure and compromised heart function were more likely to comorbid pulmonary hypertension. Pulmonary hypertension maybe a sign of worse cardiovascular outcome in CKD patients.

Histomorphometric analysis of the human internal thoracic artery and relationship with cardiovascular risk factors

In this study, we aimed at performing a histomorphometric analysis of human left internal thoracic artery (ITA) samples as well as at correlating the histomorphometric findings with the clinical profile, including risk factors and medication. Distal segments of ITA were obtained from 54 patients undergoing coronary artery bypass grafting. Histological observation was performed in paraffin-embedded transverse sections of ITA through four staining protocols: hematoxylin-eosin, van Gieson, Masson’s trichrome and von Kossa. Morphometric analysis included the intimal width (IW), medial width (MW) and intima/media ratio (IMR). No overt atherosclerotic lesions were observed. Mild calcifications were observed across the vascular wall layers in almost all samples. Multivariable linear regression analysis showed associations between IW and IMR and the following clinical variables: age, gender, kidney function expressed as eGFR and myocardial infarction history. Age (odds ratio = 1.16, P = 0.004), female gender (odds ratio = 11.34, P = 0.011), eGFR (odds ratio = 1.03, P = 0.059) and myocardial infarction history (odds ratio = 4.81, P = 0.040) were identified as the main clinical predictors for intimal hyperplasia. Preatherosclerotic lesions in ITA samples from patients undergoing coronary revascularization were associated not only with classical cardiovascular risk factors such as age and gender, but also with other clinical variables, namely kidney function and myocardial infarction history.

Vasomotion as an oscillatory sign of functional impairment in the human internal thoracic artery: A study based on risk factors and vessel reactivity

NEW FINDINGS

What is the central question of this study? Vasomotion has been viewed as a rhythmic oscillation of the vascular tone that is physiologically important for optimal tissue perfusion. Also, it has been studied primarily in the microcirculation. However, the precise underlying mechanisms and the physiological significance remain unknown. What is the main finding and its importance? Vasomotion is not specific to the microcirculation, as shown by our findings. In human arteries from patients undergoing cardiac surgery, an increased incidence was associated with endothelial dysfunction settings. Therefore, this oscillatory behaviour might be a signal of functional impairment and not of integrity.

ABSTRACT

Vasomotion has been defined as the rhythmic oscillation of the vascular tone, involved in the control of the blood flow and subsequent tissue perfusion. Our aims were to study the incidence of vasomotion in the human internal thoracic artery and the correlation of this phenomenon with the clinical profile and parameters of vascular reactivity. In our study, vasomotion was elicited with a single-dose contractile stimulation of noradrenaline (10 μm) in internal thoracic artery segments, from patients undergoing coronary artery bypass grafting, mounted in tissue organ bath chambers. The incidence was 29.1%. Vessel samples with vasomotion presented significantly higher contractility in response to both potassium chloride (maximal response or E_max of 7.65 ± 5.81 mN versus 4.52 ± 3.73 mN in control vessels, P = 0.024) and noradrenaline (E_max of 7.60 ± 5.93 mN versus 2.96 ± 4.41 mN in control vessels, P < 0.001). Predictive modelling through multivariable logistic regression analysis showed that female sex (odds ratio = 9.82) and increasing maximal response to noradrenaline (odds ratio = 1.19, per 1 mN increase) were associated with a higher probability of the occurrence of vasomotion, whereas increasing kidney function (expressed as estimated glomerular filtration rate) was associated with a lower probability (odds ratio = 0.97, per 1 ml min^-1  (1.73 m)^-2 ]. Our results provide a characterization of the phenomenon of vasomotion in the internal thoracic artery and suggest that vasomotion might be associated with endothelial dysfunction settings, as determined by a multivariable analysis approach. Considering the associations observed in our results, vasomotion might be a signal of functional impairment and not of integrity.

Responsiveness of internal thoracic arteries to nitroglycerin in patients with renal failure

Nitroglycerin is commonly used as an antispasmodic for treating spasm of coronary artery bypass grafts. This study investigated whether the presence of renal failure affects reactivity to nitroglycerin in internal thoracic arteries obtained from patients undergoing coronary bypass surgery. The patients were divided into three groups according to estimated glomerular filtration rate (eGFR, mL/min/1.73 m²): without renal failure (60 ≤ eGFR, n = 13), with moderate renal failure (30 ≤ eGFR < 60, n = 10), and with severe renal failure (eGFR < 30, n = 10). Organ chamber technique was used to evaluate concentration-related responses of isolated internal thoracic arteries to vasodilators. Nitroglycerin induced a concentration-dependent relaxation, which was significantly augmented in patients with severe but not moderate renal failure than in those without renal failure. In addition, there was a negative correlation between eGFR and the relaxant efficacy of nitroglycerin (P = 0.016). On the other hand, relaxant responses to BAY 60-2770 (which enhances cGMP generation as with nitroglycerin) were similar among three grades of renal function. An inverse relationship of eGFR to the relaxant efficacy of BAY 60-2770 was not observed, either (P = 0.314). These findings suggest that severe renal failure specifically potentiates nitroglycerin-induced relaxation in internal thoracic artery grafts.

Ultrastructural and histomorphologic properties of the internal thoracic artery: implications for coronary revascularization

Coronary artery disease represents a major health problem worldwide for which coronary artery bypass surgery remains a standard of care. Among the several grafts that are available, the internal thoracic artery (ITA) has long been considered the best as several advantages have been described compared with other vessels (e.g. saphenous vein or radial artery), namely, an absent to minor atherosclerotic development. In fact, several studies showed the presence of preatherosclerotic lesions, such as intimal and/or medial thickening, medial fibrosis, among others, in the presence of certain cardiovascular risk factors as well as established atherosclerotic lesions (i.e. type II or more lesions). This paper primarily aimed at reviewing the current knowledge on the histomorphological characteristics of ITA as well as the comparative histomorphology of ITA with other vessel grafts currently in use in coronary surgery. As some of the evidence is not clear or consensual, this paper also aimed at reviewing the main histopathological, histomorphometrical, and ultrastructural findings in ITAs from patients with known cardiovascular risk factors (e.g. aging, obesity, hypertension, diabetes, smoking, and others). As the presence of preatherosclerotic and/or atherosclerotic lesions may compromise the success of the myocardial revascularization and lead to graft failure, contributing toward the associated morbidity and/or mortality, it is essential to improve the scientific knowledge on the structural characterization of ITAs and its correlation with the cardiovascular risk profile.

Impact of type 2 diabetes on vascular reactivity to cGMP generators in human internal thoracic arteries

OBJECTIVE

The balance between nitric oxide (NO)-sensitive and -insensitive forms of soluble guanylate cyclase (sGC) has been demonstrated to be disrupted in certain lifestyle-related diseases. However, it remains unclear whether type 2 diabetes results in a shift of sGC to the NO-insensitive form. This study addressed this issue in the human blood vessel.

METHODS

Internal thoracic arteries were obtained from patients undergoing coronary artery bypass grafting. Helically cut strips of the arteries were suspended in organ chambers, and relaxant responses to nitroglycerin (NO-sensitive sGC stimulant) and BAY 60-2770 (NO-insensitive sGC stimulant) were assessed.

RESULTS

The patients were divided into two groups according to the presence of type 2 diabetes (HbA1c: 7.0±0.3%) or its absence (HbA1c: 5.6±0.1%). Nitroglycerin-induced relaxation was not different in the arteries obtained from type 2 diabetic and non-diabetic patients. In addition, the relaxant response to BAY 60-2770 in type 2 diabetics was comparable to that observed in non-diabetics. Although the patients enrolled often had vascular risk factors other than type 2 diabetes, the relaxant responses were still in the same range in a comparison based on the number of risk factors. However, in separate experiments, the relaxant response to nitroglycerin was attenuated by pre-incubation of the arteries with ODQ (sGC imbalance inducer), whereas the relaxant response to BAY-60-2770 was augmented.

CONCLUSIONS

These findings suggest that type 2 diabetes does not affect the balance between NO-sensitive and -insensitive sGC in human internal thoracic artery grafts.