Altered myocardial vasodilatation in patients with hypertriglyceridemia in anatomically normal coronary arteries

Contribution of Plasma Lipid Disturbances to Vascular Endothelial Function in Patients With Slow Coronary Flow

Previous studies have suggested that microcirculatory abnormalities cause slow coronary flow (SCF). However, the underlying mechanism of this phenomenon has not yet been well documented. Therefore, the aim of this study was to determine the role of plasma lipid disturbances in pathogenesis of slow coronary flow (SCF). Forty patients with SCF (group I) and 37 subjects with normal coronary arteries (group II) were included in the study. In each subject plasma lipid concentrations (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], and triglyceride [TG]) and brachial artery flow-mediated dilatation (FMD) and nitroglycerin (NTG)-induced dilatation were measured. Total cholesterol level was found to be similar in the 2 groups. In group I, HDL-C level was lower than in group II (34 ±3 vs 40 ±4 mg/dL, p=0.0001). In group I, TG level was higher than in group II (213 ±29 vs 198 ±24 mg/dL p=0.002). In group I, FMD was smaller than that of group II (3.48 ±3.1% vs 10.4 ±5.6%, p=0.0001). The percent NTG-induced dilatation was not different between the groups (15.5 ±5.3% vs 17.3 ±6.9%, p=0.27). On regression analysis; there was a significant relationship between percent of FMD and HDL-C ( r =0.65, p=0.0001). When the 2 groups were analyzed separately, HDL-C was still related to percent of FMD in both groups ( r =0.47 p=0.002 and r =0.45 p=0.005, respectively). Multivariate regression analysis showed that only plasma HDL-C was independently related to FMD (F=7.5 p=0.0001). In patients with SCF, reduced flow-mediated dilatation was detected and was found to be associated with plasma lipid disturbances, principally low HDL and high TG levels.

Postprandial effect of dietary fat quantity and quality on arterial stiffness and wave reflection: a randomised controlled trial

Background

Arterial stiffness is a component of vascular function and an established risk factor for cardiovascular disease. There is a lack of conclusive evidence on the effect of a meal rich in monounsaturated fat (MUFA) compared with an isoenergetic meal rich in saturated fat (SFA) on postprandial vascular function and specifically on arterial stiffness.

Methods

Twenty healthy, non-smoking males (BMI 24 ± 2 kg/m²; age 37.7 ± 14.4 y) participated in this single-blind, randomised, cross-over dietary intervention study. Each subject was randomised to receive a high-fat test-meal (3 MJ; 56 ± 2 g fat) at breakfast on 2 separate occasions, one rich in oleic acid (MUFA-meal) and one rich in palmitic acid (SFA-meal), and the meals were isoenergetic. Blood pressure (BP), arterial stiffness (PWV) and arterial wave reflection (augmentation index, AIx) were measured using applanation tonometry at baseline and every 30 minutes up to 4 hours after the ingestion of the test-meals.

Results

All subjects completed both arms of the dietary intervention. There was no significant difference in BP parameters, PWV or AIx at baseline between the two treatments (P > 0.05). There was a significant increase in brachial and aortic BP, mean arterial pressure (MAP), heart rate and PVW (time, P < 0.05) over the four hours after consumption of the fat-rich test-meal although the increase in PWV was no longer significant when adjusted for the increase in MAP. There was no difference in PWV between the two treatments (treatment*time, P > 0.05). There was a significant reduction in AIx (time, P < 0.05) over the four hour postprandial period although this was no longer significant when adjusted for the increase in heart rate and MAP (time, P > 0.05). There was no difference in AIx between the two treatments (treatment*time, P > 0.05). However, the reduction in heart rate corrected augmentation index (AIx₇₅) was significant when corrected for the increase in MAP (time, P < 0.01) with no differential effect of the treatments (treatment*time, P > 0.05).

Conclusions

This study has demonstrated a BP dependent increase in PWV and a decrease in arterial wave reflection in the four hour period in response to a high-fat meal. There was no evidence however that replacement of some of the SFA with MUFA had a differential effect on these parameters. The study highlights the need for further research to understand the effects of the substitution of SFA with MUFA on non-serum, new and emerging risk factors for CVD such as arterial stiffness.

Quantification of myocardial blood flow: what is the clinical role?

Quantification of regional myocardial blood flow and of its responses to targeted physiologic and pharmacologic interventions, which is now available with positron emitting tracers of blood flow and positron emission tomography (PET), extends the diagnostic potential of standard myocardial perfusion imaging. These noninvasive flow measurements serve as tools for quantifying functional consequences of epicardial coronary artery disease, as well as of impairments in microcirculatory reactivity that escape detection by standard perfusion imaging. Flow measurements are clinically useful for more comprehensively assessing the extent and severity of coronary vascular disease or impairments in microcirculatory function in noncoronary cardiac disease. Flow estimates in these disorders contain independent or unique prognostic information about future major cardiac events. Flow measurements are also useful for assessing the coronary risk, for predicting long-term cardiovascular events, and for monitoring the effectiveness of risk reduction strategies.

Identifying cardiovascular risk factors in a patient population with coronary artery ectasia

Coronary artery ectasia (CAE) is frequently considered as a form of coronary artery disease. Cardiovascular risk factors were determined in a patient population with CAE. The 51 patients with isolated CAE (group 1), 61 patients with CAE coexisting with significant coronary stenosis (group 2), and 62 subjects with significant coronary stenosis (group 3) were included in the study, and the distribution of cardiovascular risk factors was compared. Thirty of 51 patients with isolated CAE had presented with typical angina pectoris, 8 patients with unstable angina pectoris, and 13 patients had atypical chest pain or palpitation. The 21 of 51 patients with isolated CAE had definitive positive treadmill exercise test results. Positive family history was similar in each group. The history of smoking was similar in group 1 and group 2 but higher than group 3. Frequency of hypertension was similar in group 1 and group 2 but higher than that in group 3. Frequency of diabetes mellitus was similar in group 1 and group 2 but lower than group 3. Plasma lipid levels and the number of patients with lipid disturbances were also similar in each group. In addition, C-reactive protein (CRP) levels were above the normal limits and there was no difference among groups with respect to plasma CRP levels. CAE appears to be associated with traditional cardiovascular risk factors such as hypertension, smoking, and hyperlipidemia. In addition, elevated CRP level in patients with CAE may suggest the role of inflammatory process in development of CAE.

Difference in myocardial flow reserve between patients with dilated cardiomyopathy and those with dilated phase of hypertrophic cardiomyopathy: evaluation by 15O-water PET

BACKGROUND

The clinical features of patients with the dilated phase of hypertrophic cardiomyopathy (DHCM) may resemble those of patients with dilated cardiomyopathy (DCM); that is, systolic dysfunction and left ventricular dilatation. Myocardial flow reserve (MFR) is impaired in patients with nonischemic cardiomyopathy, and the reduced MFR may be related to poor prognosis. Several studies report that the mortality rate for patients with DHCM is higher than for DCM, but the difference between these 2 cardiomyopathies is still unclear. The purpose of this study was to assess the MFR of these 2 cardiomyopathies, using (15)O-water positron emission tomography (PET) to elucidate their differences.

METHODS AND RESULTS

In total 30 patients were investigated: 23 with DCM (Group A) and 7 with DHCM (Group B). All those who were in a stable condition underwent cardiac catheterization. Myocardial blood flow (MBF) at rest and under ATP infusion was measured by (15)O-water PET, and the MFR was calculated. There were no significant differences in the hemodynamics of the 2 groups. The mean MFR in DHCM was significantly lower than that in DCM (1.49+/-0.31 vs 2.62+/-1.08; p=0.042), whereas MBF at rest did not differ (DCM vs DHCM: 0.66+/-0.20 vs 0.49+/-0.05 ml . min(-1) . g(-1); NS). The MFR in both Group A and B was significantly decreased compared with the normal controls (MFR in normal controls: 5.15+/-1.64, p=0.00015, 0.00013, respectively).

CONCLUSIONS

These results suggest that impaired vasodilatation (ie, dysfunction of the microcirculation) is more severe in patients with DHCM than in patients with DCM, even though patients' characteristics and hemodynamics do not differ.

Elevated Plasma Plasminogen Activator Inhibitor Type-1 is an Independent Predictor of Coronary Microvascular Dysfunction in Hypertension

BACKGROUND

Elevated plasma plasminogen activator inhibitor-1 (PAI-1) is related to cardiovascular events, but its role in subclinical coronary microvascular dysfunction remains unknown. Thus, in the present study it was investigated whether elevated plasma PAI-1 activity is associated with coronary microvascular dysfunction in hypertensive patients.

METHODS AND RESULTS

Thirty patients with untreated essential hypertension and 10 age-matched healthy controls were studied prospectively. Myocardial blood flow (MBF) was measured by using (15)O-water positron emission tomography. Clinical variables associated with atherosclerosis (low-density lipoprotein-cholesterol, high-density lipoprotein (HDL)-cholesterol, triglyceride, homeostasis model assessment (HOMA-IR), and PAI-1 activity) were assessed to determine their involvement in coronary microvascular dysfunction. Adenosine triphosphate (ATP)-induced hyperemic MBF and coronary flow reserve (CFR) were significantly lower in hypertensive patients than in healthy controls (ATP-induced MBF: 2.77+/-0.82 vs 3.49+/-0.71 ml x g(-1) x min(-1); p<0.02 and CFR: 2.95 +/-1.06 vs 4.25+/-0.69; p<0.001). By univariate analysis, CFR was positively correlated with HDL-cholesterol (r=0.46, p<0.02), and inversely with HOMA-IR (r=-0.39, p<0.05) and PAI-1 activity (r=-0.61, p<0.001). By multivariate analysis, elevated PAI-1 activity remained a significant independent determinant of diminished CFR.

CONCLUSIONS

Elevated plasma PAI-1 activity was independently associated with coronary microvascular dysfunction, which suggests that plasma PAI-1 activity is an important clue linking hypofibrinolysis to the development of atherosclerosis.

Myocardial and peripheral vascular functional adaptation to exercise training

Exercise training seems to restore impaired vascular function in both peripheral and myocardial vessels in patients with coronary artery and peripheral vascular disease or in patients with risk factors for these diseases. However, the results on the effects of exercise training on vascular function in apparently healthy subjects are controversial. We studied the effects of long-term volitionally increased physical activity on peripheral and myocardial vascular function in nine young healthy male monozygotic twin pairs discordant for physical activity and fitness. The brothers were divided into more (MAG) and less active groups according to physical activity and fitness. The difference between groups in VO(2max) was 18+/-10% (P<0.001). Myocardial perfusion at rest, during adenosine-induced vasodilatation and during cold-pressor test and myocardial oxygen consumption were measured with positron emission tomography. In addition, endothelial function was measured using ultrasound in brachial and left anterior descending coronary arteries, and standard echocardiographic measures were taken. No differences were observed in myocardial perfusion measurements between groups. MAG tended to have a lower oxygen extraction fraction (P=0.06), but oxygen consumption was similar between the groups. No differences were found in coronary artery, myocardial resistance vessel or peripheral endothelial function between groups. These results suggest that when the effects of heredity are controlled, myocardial perfusion reserve and endothelial function, both in peripheral arteries and myocardial vessels, are not enhanced by increased physical activity and fitness in young healthy adult men.

High oxidized LDL and elevated plasma homocysteine contribute to the early reduction of myocardial flow reserve in healthy adults

BACKGROUND

Impairment of coronary blood flow reserve has been shown to be an early manifestation of atherosclerosis and coronary artery disease (CAD). We studied more closely the contribution of various risk factors on early deterioration of coronary function.

MATERIALS AND METHODS

Fifty-one young, apparently healthy adults, with normal or mildly elevated serum cholesterol levels but without other major risk factors for CAD, such as diabetes or hypertension, underwent positron emission tomography (PET) studies. Coronary flow reserve (CFR) was measured using O15-water. In addition to the classical risk factors, the role of several new risk indicators, such as low-density lipoprotein (LDL) oxidation, infection (Chlamydia pneumoniae antibodies), and inflammation parameters (adhesion molecules, ICAM, VCAM, selectin, and C-reactive protein), homocysteine and body iron stores were investigated.

RESULTS

Elevated lipid and lipoprotein levels were not associated with reduced coronary reactivity. However, high autoantibody titers against oxidized LDL (oxLDL) were associated with 21% lower CFR than low oxLDL (P < 0.05). Furthermore, high homocysteine levels predicted low CFR (P < 0.05). The other measured parameters, Chlamydia pneumoniae antibody levels, C-reactive protein and adhesion molecule concentrations did not associate with myocardial blood flow. In a stepwise regression model, oxLDL (P = 0.03), homocysteine (P = 0.04) and triglycerides (P = 0.018) were significant predictors of CFR.

CONCLUSIONS

The present study suggests an important role for oxidized LDL and plasma homocysteine on early impairment of coronary reactivity in young adults.

Marked removal of bezafibrate-induced high-density lipoprotein-cholesterol by low-density lipoprotein apheresis

BACKGROUND

A case of marked reduction of the bezafibrate-induced increase of high-density lipoprotein (HDL)-cholesterol by low-density lipoprotein apheresis (LDL-apheresis) has not been previously reported.

METHODS

A 68-year-old Japanese man with arteriosclerosis obliterans (ASO), diabetes mellitus, and hyperlipidemia underwent LDL-apheresis, followed by the concomitant bezafibrate administration. Plasma lipids of pre- and post-LDL-apheresis were measured and apolipoprotein E (apoE) localization of the pre- and post-LDL-apheresis was detected by agarose gel electrophoresis.

RESULTS

Plasma concentrations of the total cholesterol, LDL-cholesterol, triglyceride, and HDL-cholesterol of pre-LDL-apheresis were 4.78 +/- 0.36, 2.74 +/- 0.24, 2.44 +/- 0.52, and 0.92 +/- 0.10 mmol/l, respectively; those of the post-LDL-apheresis were 1.94 +/- 0.31, 0.72 +/- 0.13, 0.81 +/- 0.38, and 0.86 +/- 0.11 mmol/l, respectively. LDL-apheresis reduced HDL-cholesterol by 6.4% (p=0.346). During the bezafibrate administration, plasma concentrations of the above of pre-LDL-apheresis were 5.24 +/- 0.34, 3.28 +/- 0.22, 1.26 +/- 0.25, and 1.39 +/- 0.21 mmol/l, respectively; those of the post-LDL-apheresis were 2.25 +/- 0.44, 0.80 +/- 0.12, 0.58 +/- 0.19, and 1.18 +/- 0.16 mmol/l, respectively. LDL-apheresis reduced HDL-cholesterol by 15.2% (p<0.01). Plasma apolipoprotein E detected between the prebeta- and alpha-mobility was markedly lower after the LDL-apheresis in the agarose gel electrophoresis.

CONCLUSIONS

The removal of the bezafibrate induced an increase of the HDL-cholesterol by LDL-apheresis.

Post-prandial remnant lipids impair arterial compliance

OBJECTIVES

We sought to examine the effects of plasma lipids, especially in remnants after a fat meal, on systemic arterial compliance (SAC), a newly recognized cardiovascular risk factor.

BACKGROUND

Post-prandial remnants correlate with coronary heart disease events through mechanisms that may include vascular dysfunction, although the effect on SAC has not been studied.

METHODS

Systemic arterial compliance was measured non-invasively over 6 h after a fat meal in 16 subjects with varying plasma triglyceride levels. Changes were related to rises in plasma lipids and remnant lipids. Systemic arterial compliance was measured in 20 subjects after a control low-fat meal.

RESULTS

The fat meal induced increments in plasma triglyceride and remnant cholesterol and triglyceride (respectively +54%, 50% and 290% at 3 h, analysis of variance <0.001). Systemic arterial compliance fell at 3 h and 6 h by 25% and 27% (analysis of variance <0.001). Baseline SAC correlated significantly with all lipid concentrations at 0, 3 h and 6 h, but only with triglyceride on stepwise regression analysis. The SAC response to the low-fat meal was very small and not significant.

CONCLUSIONS

This is the first demonstration of SAC becoming impaired after a fat meal. Remnant lipids and plasma total triglyceride appeared to contribute to the fall in SAC.

Flow-mediated vasoactivity and circulating adhesion molecules in hypertriglyceridemia: association with small, dense LDL cholesterol particles

BACKGROUND

Endothelial dysfunction is considered one of the earliest events in the process of atherosclerosis, and an impaired vasodilatory response has been reported in patients with dyslipidemias. However, the independent association between hypertriglyceridemia and endothelial dysfunction is controversial, and the relation between endothelium-dependent vasodilation and circulating cell adhesion molecules as markers of endothelial dysfunction has not been fully determined.

METHODS

Brachial artery flow mediated vasodilation (FMV) and the soluble forms of vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1) were determined after overnight fasting in 16 men with hypertriglyceridemia (age 33 +/- 6 years) and in 16 age-matched healthy men with normal triglycerides and cholesterol. Subjects who smoked and those with known cardiovascular disease, diabetes, hypertension, recent or active infections, or any other disease that could affect leukocyte activation were excluded from the study.

RESULTS

Compared with normal subjects, subjects with hypertriglyceridemia showed a higher level of sVCAM-1 and sICAM-1 (both P <.001), a reduced FMV (P <.01), and a smaller LDL particle size (P <.05). FMV had a significant inverse correlation with sVCAM-1 (r = -0.61, P <.001) and sICAM-1 (r = -0.38, P <.03). LDL particle size had a strong, direct association with FMV (r = 0.75, P <.001) and an inverse association with adhesion molecules. By multiple regression analysis, triglycerides (P <.001) and small LDL particle size (P <.002) predicted a reduced FMV.

CONCLUSIONS

Serum level of cell adhesion molecules is increased and FMV is impaired in young healthy men with hypertriglyceridemia compared with age-matched men with normal lipid levels. Small, dense LDL particles may play a role in determining endothelial dysfunction in these subjects.