Determinants of Arterial Wall Remodeling During Lipid-Lowering Therapy

Role of endothelial shear stress in the natural history of coronary atherosclerosis and vascular remodeling: molecular, cellular, and vascular behavior

Although the entire coronary tree is exposed to the atherogenic effect of the systemic risk factors, atherosclerotic lesions form at specific arterial regions, where low and oscillatory endothelial shear stress (ESS) occur. Low ESS modulates endothelial gene expression through complex mechanoreception and mechanotransduction processes, inducing an atherogenic endothelial phenotype and formation of an early atherosclerotic plaque. Each early plaque exhibits an individual natural history of progression, regression, or stabilization, which is dependent not only on the formation and progression of atherosclerosis but also on the vascular remodeling response. Although the pathophysiologic mechanisms involved in the remodeling of the atherosclerotic wall are incompletely understood, the dynamic interplay between local hemodynamic milieu, low ESS in particular, and the biology of the wall is likely to be important. In this review, we explore the molecular, cellular, and vascular processes supporting the role of low ESS in the natural history of coronary atherosclerosis and vascular remodeling and indicate likely mechanisms concerning the different natural history trajectories of individual coronary lesions. Atherosclerotic plaques associated with excessive expansive remodeling evolve to high-risk plaques, because low ESS conditions persist, thereby promoting continued local lipid accumulation, inflammation, oxidative stress, matrix breakdown, and eventually further plaque progression and excessive expansive remodeling. An enhanced understanding of the pathobiologic processes responsible for atherosclerosis and vascular remodeling might allow for early identification of a high-risk coronary plaque and thereby provide a rationale for innovative diagnostic and/or therapeutic strategies for the management of coronary patients and prevention of acute coronary syndromes.

Correlation between morphologic characteristics and local temperature differences in culprit lesions of patients with symptomatic coronary artery disease

OBJECTIVES

The purpose of this study was to investigate the possible correlation between morphologic and functional characteristics of culprit lesions (CL) in patients with acute coronary syndromes (ACS) and chronic stable angina (CSA).

BACKGROUND

Intravascular ultrasound (IVUS) provides morphologic assessment and intracoronary thermography (ICT) evaluates the local inflammatory activation of CL.

METHODS

Eighty-one consecutive patients, 48 with ACS and 33 with CSA, were enrolled. Ratio of lesion to reference external elastic membrane area, indicated by IVUS, was defined as positive remodeling index (pRi) (> or =1) or negative remodeling index (nRi) (<1). We also investigated the existence of ruptured plaque (rp) in the CL. By ICT temperature difference (DeltaT) between the CL and the proximal vessel wall was measured.

RESULTS

Patients with ACS had greater remodeling index than patients with CSA (1.15 +/- 0.18 vs. 0.90 +/- 0.12; p < 0.01), as well as increased DeltaT (0.08 +/- 0.03 degrees C vs. 0.04 +/- 0.02 degrees C; p < 0.01). Patients with pRi had higher DeltaT than patients with nRi (0.07 +/- 0.03 degrees C vs. 0.04 +/- 0.02 degrees C; p < 0.001). In patients with nRi there was no difference in DeltaT between ACS and CSA (p = 0.22). Patients with rp had increased DeltaT compared with patients without rp (0.09 +/- 0.03 degrees C vs. 0.05 +/- 0.02 degrees C; p < 0.01). Multivariate analysis showed that DeltaT was independently correlated with the presence of rp, pRi, and ACS.

CONCLUSIONS

The present study showed that culprit lesions with plaque rupture and positive arterial remodeling have increased thermal heterogeneity, although in certain patients a discrepancy between morphogic and functional characteristics was observed. A combination of morphologic and functional examination may offer additional diagnostic and prognostic information.

Two-week treatment with pravastatin improves ventriculo-vascular haemodynamic interactions in young men with type 1 diabetes

Young patients with diabetes but without established vascular disease have altered conduit and resistance artery reactivity. Early endothelial dysfunction is an initial step in atherogenesis: reductions in nitric oxide (NO) production in these vascular beds are implicated. The study aim was two-fold: first, to detect baseline abnormalities in cardiac function, conduit vessels and the microcirculation using applanation tonometry, brachial artery ultrasound and laser Doppler fluximetry, respectively; and second, to investigate any modification in these parameters with the use of pravastatin. Nine young men with diabetes and normoalbuminuria were randomised in a double-blind cross-over fashion to placebo or pravastatin (40 mg) treatment for two weeks. They underwent scans on three separate occasions. Control patients (n=12) underwent a baseline scan but were not given any drug treatment. It was found that patients with diabetes had significantly higher systolic and diastolic blood pressures, heart rate and Buckberg index (propensity to myocardial ischaemia). Brachial artery reactivity and microcirculatory dilation were both reduced. Levels of von Willebrand Factor, a marker of endothelial damage, were also elevated. Pravastatin treatment restored these sub-clinical abnormalities towards normal levels. In conclusion, pravastatin improves vascular abnormalities in young male patients with diabetes through alterations in microcirculation and conduit vessel function, with secondary myocardial effects. This may be of benefit in preventing end-organ injury.

Coronary Plaque Vulnerability in Metabolic Syndrome Assessment of Carotid Artery Morphology in Acute Coronary Syndrome

BACKGROUND

The aim of the present study was to investigate the clinical implication of metabolic syndrome and carotid artery morphologies on coronary plaque vulnerability in Japanese men with acute coronary syndrome (ACS).

METHODS AND RESULTS

Consecutive ACS Japanese men (n=225) underwent emergent coronary angiography and B-mode ultrasonography within 1 week of the acute coronary event. With a 11.3-MHz linear array transducer, the morphologies of common carotid artery were examined. Common carotid arteries with an intima-media thickness>1.1 mm and interadventitial diameter>8.0 mm were considered to be undergoing carotid artery remodeling. Patients were divided into 2 groups based on the number of complex plaques identified by coronary angiography. Abdominal obesity, low level of high-density lipoprotein and carotid artery remodeling were more often observed in patients with multiple, complex coronary plaques than in patients with a single, complex plaque (p<0.03, p<0.03 and p=0.0001, respectively). Metabolic syndrome and carotid artery remodeling were independent predictors of multiple, complex coronary plaques (odds ratio 1.86, p<0.05; odds ratio 5.96, p<0.0001).

CONCLUSION

Metabolic syndrome and carotid artery remodeling might be useful indicators to assess the efficacy of aggressive treatments for secondary prevention of cardiovascular events in ACS Japanese men.