An association between microvascular endothelial dysfunction, transcardiac nitric oxide production and pro-inflammatory cytokines after heart transplantation in humans

Coronary microvascular dysfunction in the clinical setting: from mystery to reality

Far more extensive than the epicardial coronary vasculature that can be visualized angiographically is the coronary microcirculation, which foregoes routine imaging. Probably due to the lack of techniques able to provide tangible evidence of its crucial role, the clinical importance of coronary microvascular dysfunction is not fully appreciated. However, evidence gathered over the last several decades indicates that both functional and structural abnormalities of the coronary microvasculature can lead to myocardial ischaemia, often comparable with that caused by obstructive coronary artery disease. Indeed, a marked increase in coronary microvascular resistance can impair coronary blood flow and trigger angina pectoris, ischaemic ECG shifts, and myocardial perfusion defects, and lead to left ventricular dysfunction in patients who otherwise have patent epicardial coronary arteries. This condition--often referred to as 'chest pain with normal coronary arteries' or 'cardiac syndrome X'--encompasses several pathogenic mechanisms involving the coronary microcirculation. Of importance, coronary microvascular dysfunction can occur in conjunction with several other cardiac disease processes. In this article, we review the pathogenic mechanisms leading to coronary microvascular dysfunction and its diagnostic assessment, as well as the different clinical presentations and prognostic implications of microvascular angina. As such, this review aims to remove at least some of the mystery surrounding the notion of coronary microvascular dysfunction and to show why it represents a true clinical entity.

Correlation of epicardial and systemic flow-mediated vasodilation in patients with atypical angina but no evidence of atherosclerotic disease

BACKGROUND

Atypical angina represents a diagnostic challenge and can be observed in the absence of significant coronary atherosclerosis. Endothelial dysfunction is a relevant marker of prognosis, considering cardiovascular events. The aim of the present study was to compare flow-mediated vasodilation (FMD) in systemic peripheral and epicardial coronary arteries. If noninvasive measurements of FMD in systemic arteries correlated with invasive measurements of coronary FMD, this may facilitate diagnostic approaches and determination of prognosis in patients with atypical angina in the future. Patients with atherosclerosis were excluded, because structural changes of coronary vessels may impair adequate comparison.

METHODS

Endothelial function (ENF) of epicardial and systemic arteries was examined in 61 consecutive patients with atypical angina in whom significant atherosclerosis was excluded by coronary angiography. ENF of the epicardial arteries was examined during heart catheterization, measuring diameter changes of the proximal left anterior descending coronary artery (LAD) in response to reactive hyperemia, induced by locally administered adenosine via infusion catheter to the mid-segment of the LAD (coronary FMD [FMDc]). ENF of the radial artery was examined with high-resolution ultrasound, measuring peripheral FMD (FMDp) in response to reactive hyperemia induced by distal cuff occlusion. Endothelium-independent vasoreactivity to glycerol trinitrate was assessed.

RESULTS

In patients with atypical angina in the absence of atherosclerosis, there was a significant correlation in ENF between coronary and systemic arteries (r=0.437; P=0.001). The underlying disease was myocardial inflammation (Inf) in 48 patients, in whom the mean (+/- SD) ENF of epicardial (FMDc-Inf 3.40+/-5.55%) and systemic (FMDp-Inf 3.69+/-2.93%) arteries was significantly impaired (P<0.001), compared with 13 control (Co) patients who had normal myocardial biopsies (FMDc-Co 14.51+/-8.62%; FMDp-Co 7.69+/-3.42%). FMD of coronary (r=-0.353; P=0.005) and systemic (r=-0.542; P<0.001) arteries correlated significantly with myocardial inflammation and endothelial activation.

CONCLUSIONS

There was a significant correlation in FMD between coronary and systemic arteries in patients with atypical angina but without significant atherosclerosis. Inflammatory processes are associated with endothelial dysfunction of both vascular regions.

Differential Aspects of Endothelial Function of the Coronary Microcirculation Considering Myocardial Virus Persistence, Endothelial Activation, and Myocardial Leukocyte Infiltrates

Background— Viral cardiomyopathy resulting from myocardial virus persistence can be associated with inflammatory immune responses that involve the myocardium and coronary blood vessels. The aim of this study was to investigate the differential impact of myocardial virus persistence and inflammation on endothelial function of the coronary microcirculation.

Methods and Results— In 71 patients with nonischemic cardiomyopathy, myocardial biopsies were examined for virus persistence (by polymerase chain reaction) and inflammation (by immunohistology). Endothelial function of the coronary microcirculation was examined during heart catheterization by measuring diameter (by quantitative coronary angiography) and velocity changes (by intracoronary Doppler) of the left anterior descending artery in response to acetylcholine. Coronary blood flow (CBF) was calculated. Endothelium-independent vasoreactivity to adenosine was assessed. Mean age of the patients (37 men, 34 women) was 43±13 years; mean ejection fraction was 64±11%. In 43 patients, adenovirus, enterovirus, parvovirus, or HHV-6 was detected; 28 had no virus. Endothelial function of the coronary microcirculation was significantly impaired in patients with myocardial virus persistence (V) compared with patients without virus (Co) (ΔCBF-V, 22±86%; ΔCBF-Co, 110±113%; P =0.001), which was confirmed in 51 patients with myocardial inflammation (MC) (32 with virus, 19 with no virus) (ΔCBF-MC-V, 12±89%; ΔCBF-MC-Co, 81±109%; P =0.034) and in 20 patients with normal immunohistology of the myocardial biopsies (Co) (11 with virus, 9 with no virus) (ΔCBF-Co-V, 51±72%; ΔCBF-Co-Co, 175±97%; P =0.006). Endothelial function of the coronary microcirculation was also significantly impaired in patients with myocardial inflammation/endothelial activation compared with patients without inflammatory immune response. Endothelium-independent vasodilation was not influenced significantly.

Conclusions— Myocardial virus persistence and myocardial inflammation/endothelial activation are associated with endothelial dysfunction of the coronary microcirculation. Endothelial dysfunction in patients with myocardial virus persistence can occur independently of myocardial inflammation/endothelial activation but is more pronounced in patients with concurrent inflammation.

Soluble inflammatory markers in coronary sinus and peripheral blood of heart transplant recipients

Cardiac allograft rejection is a focal inflammation and soluble markers are released into coronary sinus (CS). We investigated whether plasma-soluble markers in CS is better to predict the clinical status of transplant recipients than in peripheral blood (PB). Between February 1998 and January 2001, 51 patients admitted for endomyocardial biopsy were included. The clinical events of the transplant recipient were recorded as: early post-transplant, long-term uneventful status, infection, acute rejection and transplant coronary artery disease. The plasma levels of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), ICAM-1, P-selectin, high-sensitive C-reactive protein (CRP) and troponin-I of CS and PB were determined. There were 71 blood samples. In patients within 1 month after heart transplant, there was a higher level of P-selectin, ICAM-1, CRP and troponin-I in CS and PB. In patients with infection, there was a higher level of all soluble markers except IL-2 in CS and PB. Patients with a long-term uneventful status had a lower level of CRP in PB but not in CS. Patients with acute rejection had a higher level of IL-2 in PB but not in CS. Patients with transplant coronary artery disease had a higher level of TNF-alpha in PB but not in CS. Soluble markers in CS failed to predict the occurrence of acute or chronic rejections.

The endothelium in clinical cardiac transplantation

Cardiac transplantation is the most successful therapy for refractory heart failure, but clinical transplantation is still confronted with the problems of acute rejection and acute pump failure. The limiting factor in achieving prolonged survival remains cardiac allograft vasculopathy. In recent years it has become apparent that from brain death onward, the cardiac endothelium plays a key role in these acute and chronic events. Brain death is associated with an inflammatory response that primes the endothelium for cumulative injury during the subsequent stages of ischemic cold storage, reperfusion and allorecognition. As a structural and functional interface, the endothelium is the site at which inflammatory cells move from the bloodstream through the vessel wall into the parenchyma. The endothelium interacts with the complement system, the coagulation and inflammatory cascades, circulating leukocytes, the immune system, the smooth muscle in the vessel wall, and the surrounding matrix and cardiomyocytes. A better understanding of its many roles may lead to expansion of our therapeutic possibilities and better outcomes overall. This article reviews the possible roles of the endothelium in relation to cardiac transplantation, and discusses the diagnostic and therapeutic modalities that are available to date.