Vascular smooth muscle cell phenotypic modulation in culture is associated with reorganisation of contractile and cytoskeletal proteins

Smooth muscle cells (SMC) exhibit a functional plasticity, modulating from the mature phenotype in which the primary function is contraction, to a less differentiated state with increased capacities for motility, protein synthesis, and proliferation. The present study determined, using Western analysis, double-label immunofluorescence and confocal microscopy, whether changes in phenotypic expression of rabbit aortic SMC in culture could be correlated with alterations in expression and distribution of structural proteins. Contractile state SMC (days 1 and 3 of primary culture) showed distinct sorting of proteins into subcellular domains, consistent with the theory that the SMC structural machinery is compartmentalised within the cell. Proteins specialised for contraction (alpha -SM actin, SM-MHC, and calponin) were highly expressed in these cells and concentrated in the upper central region of the cell. Vimentin was confined to the body of the cell, providing support for the contractile apparatus but not co-localising with it. In line with its role in cell attachment and motility, beta -NM actin was localised to the cell periphery and basal cortex. The dense body protein alpha -actinin was concentrated at the cell periphery, possibly stabilising both contractile and motile apparatus. Vinculin-containing focal adhesions were well developed, indicating the cells' strong adhesion to substrate. In synthetic state SMC (passages 2-3 of culture), there was decreased expression of contractile and adhesion (vinculin) proteins with a concomitant increase in cytoskeletal proteins (beta -non-muscle [NM] actin and vimentin). These quantitative changes in structural proteins were associated with dramatic chan-es in their distribution. The distinct compartmentalisation of structural proteins observed in contractile state SMC was no longer obvious, with proteins more evenly distributed throughout die cytoplasm to accommodate altered cell function. Thus, SMC phenotypic modulation involves not only quantitative changes in contractile and cytoskeletal proteins, but also reorganisation of these proteins. Since the cytoskeleton acts as a spatial regulator of intracellular signalling, reorganisation of the cytoskeleton may lead to realignment of signalling molecules, which, in turn, may mediate the changes in function associated with SMC phenotypic modulation. (C) 2001 Wiley-Liss, Inc.

Lipid-lowering therapy following major cardiac events: progress and deficits

Objective: To assess hospital prescribing of lipid-lowering agents in a tertiary hospital, and examine continuation of, or changes to, such therapy in the 6-18 months following discharge. Design: Retrospective data extraction from the hospital records of patients admitted from October 1998 to April 1999. These patients and their general practitioners were then contacted to obtain information about ongoing management after discharge. Setting: Tertiary public hospital and community. Participants: 352 patients admitted to hospital with acute myocardial infarction or unstable angina, and their GPs. Main outcome measures: Percentage of eligible patients discharged on lipid-lowering therapy and percentage of patients continuing or starting such therapy 6-18 months after discharge. Results: 10% of inpatients with acute coronary syndromes did not have lipid-level estimations performed or arranged during admission. Documentation of lipid levels in discharge summaries was poor. Eighteen per cent of patients with a total serum cholesterol level greater than 5.5 mmol/L did not receive a discharge prescription for a cholesterol-lowering agent. Compliance with treatment on follow-up was 88% in the group discharged on treatment. However, at follow-up, 70% of patients discharged without therapy had not been commenced on lipid-lowering treatment by their GPs. Conclusions: Prescribing of lipid-lowering therapy for secondary prevention following acute coronary syndromes remains suboptimal. Commencing treatment in hospital is likely to result in continuing therapy in the community. Better communication of lipid-level results, treatment and treatment aims between hospitals and GPs might encourage optimal treatment practices.

Using postoperative cardiac troponin-I (cTi) levels to detect myocardial ischaemia in patients undergoing vascular surgery

Background, Cardiac complications occur commonly in vascular surgery patients. Diagnosis of cardiac complications is difficult because of the inaccuracies associated with traditional cardiac enzyme measurements. CTi, a highly sensitive and specific marker of myocardial injury, may be able to detect cardiac complications with greater ease and accuracy. Methods. The study prospectively examined 100 consecutive patients who underwent major vascular surgery between 6/7/98 and 31/12/98 at the Royal Brisbane Hospital. Daily measurements of cTi, creatine kinase (CK), creatine kinase MB (CKMB), CKMB index, renal function and haemoglobin were taken for three postoperative days. One postoperative electrocardiograph (ECC) was taken. An extensive cardiac history was taken. Intraoperative and postoperative events were recorded. Findings. There were 100 patients, 18 patients (18%) had a cTi elevation. On the basis of classical diagnostic criteria, 15 patients (15%) suffered one or more cardiac complication (either myocardial infarction, congestive cardiac failure, unstable angina or atrial fibrillation), One patient (1%) who had a cTi elevation died. CTI elevation occurred in five patients (5%) who were not diagnosed with cardiac complications based on traditional criteria. Despite not meeting specific diagnostic criteria for cardiac complications, all patients showed signs and symptoms that could be attributed to myocardial ischaemia, Every patient who developed congestive cardiac failure or atrial fibrillation had a cTi elevation. A Chi-square analysis revealed a significant association between cTi elevation and postoperative cardiac complications. Four variables contributed small but significant amounts of unique variance to the prediction of peak cTi on linear regression analysis. These were peak CKMB index, postoperative congestive cardiac failure, postoperative chest pain and postoperative cardiac complications. Conclusions. Routine cTi monitoring of postoperative vascular patients would be an effective and inexpensive way to detect patients with cardiac complications. The relationship between postoperative cTi elevation and significant coronary artery disease remains to be shown, (C) 2001 The international Society for Cardiovascular Surgery. Published by Elsevier Science Ltd. All rights reserved.

Vascular endothelial growth factor-B-deficient mice show impaired development of hypoxic pulmonary hypertension

To test the hypothesis that Vegf-B contributes to the pulmonary vascular remodelling, and the associated pulmonary hypertension, induced by exposure of mice to chronic hypoxia. Methods: Right ventricular systolic pressure, the ratio of right ventricle/[left ventricle+septum] (RV/[LV+S]) and the thickness of the media (relative to vessel diameter) of intralobar pulmonary arteries (o.d. 50-150 and 151-420 mum) were determined in Vegfb knockout mice (Vegfb(-/-); n=17) and corresponding wild-type mice (Vegfb(+/+); n=17) exposed to chronic hypoxia (10% oxygen) or housed in room air (normoxia) for 4 weeks. Results: In Vegfb(+/+) mice hypoxia caused (i) pulmonary hypertension (a 70% increase in right ventricular systolic pressure compared with normoxic Vegfb(+/+) mice; P

The role of Doppler left ventricular filling indexes and Doppler tissue echocardiography in the assessment of cardiac involvement in hereditary hemochromatosis

Although cardiac dysfunction in hereditary hemochromatosis (HHC) can be evaluated by conventional echocardiography, findings are often not specific. To test the hypothesis that the assessment of (1) conventional Doppler left ventricular filling indexes and (2) intrinsic elastic properties of the myocardium by Doppler tissue echocardiography can both enhance the accuracy of echocardiographic diagnosis of cardiac involvement in HHC, a group of 18 patients with HHC (mean age 50+/-7 years) and 22 age-matched healthy subjects were studied. The following indexes were characteristic for HHC: (1) the duration of atrial reversal measured from pulmonary venous flow (ms) was longer(118+/-20 vs 90+/-16; P

Skeletal muscle mitochondrial ATP production rate and walking performance in peripheral arterial disease

This study tested the hypotheses that skeletal muscle mitochondrial ATP production rate (MAPR) is impaired in patients with peripheral arterial disease (PAD) and that it relates positively to their walking performances. Seven untrained patients, eight exercise-trained patients and 11 healthy controls completed a maximal walking test and had muscle sampled from the gastrocnemius medialis muscle. Muscle was analysed for its MAPR in the presence of pyruvate, palmitoyl-L-carnitine or both, as well as citrate synthase (CS) activity. MAPRs were not different between untrained PAD and controls. In contrast, MAPRs (pyruvate) were significantly higher in trained PAD vs. controls. MAPR (pyruvate combinations) was also significantly higher in trained than untrained PAD muscle. MAPR and CS activity were highly correlated with walking performance in patients, but not in controls. These data do not support the hypothesis that isolated mitochondria are functionally impaired in PAD and demonstrate that the muscle mitochondrial capacity to oxidize carbohydrate is positively related to walking performance in these patients.

Guideline-discordant care in acute myocardial infarction: predictors and outcomes

Objectives: To determine (i) factors which predict whether patients hospitalised with acute myocardial infarction (AMI) receive care discordant with recommendations of clinical practice guidelines; and (ii) whether such discordant care results in worse outcomes compared with receiving guideline-concordant care. Design: Retrospective cohort study. Setting: Two community general hospitals. Participants: 607 consecutive patients admitted with AMI between July 1997 and December 2000. Main outcome measures: Clinical predictors of discordant care; crude and risk-adjusted rates of inhospital mortality and reinfarction, and mean length of hospital stay. Results: At least one treatment recommendation for AMI was applicable for 602 of the 607 patients. Of these patients, 411(68%) received concordant care, and 191 (32%) discordant care. Positive predictors at presentation of discordant care were age > 65 years (odds ratio [OR], 2.5; 95% Cl, 1.7-3.6), silent infarction (OR, 2.7; 95% Cl, 1.6-4.6), anterior infarction (OR, 2.5; 95% Cl, 1.7-3.8), a history of heart failure (OR, 6.3; 95% Cl, 3.7-10.7), chronic atrial fibrillation (OR, 3.2; 95% Cl, 1.5-6.4); and heart rate greater than or equal to 100 beats/min (OR, 2.1; 95% Cl, 1.4-3.1). Death occurred in 12.0% (23/191) of discordant-care patients versus 4.6% (19/411) of concordant-care patients (adjusted OR, 2.42; 95% Cl, 1.22-4.82). Mortality was inversely related to the level of guideline concordance (P = 0.03). Reinfarction rates also tended to be higher in the discordant-care group (4.2% v 1.7%; adjusted OR, 2.5; 95% Cl, 0.90-7.1). Conclusions: Certain clinical features at presentation predict a higher likelihood of guideline-discordant care in patients presenting with AMI Such care appears to increase the risk of inhospital death.

Influence of wall stress and left ventricular geometry on the accuracy of Dobutamine stress Echocardiography

OBJECTIVES The goal of this study was to determine whether wall stress at rest and during stress could explain the influence of left ventricular (LV) morphology on the accuracy of dobutamine stress echocardiography (DSE). BACKGROUND The sensitivity of DSE appears to be reduced in patients with concentric remodeling, but the cause of this finding is unclear. METHODS We studied 161 patients without resting wall motion abnormalities who underwent DSE and coronary angiography. Patients were classified into four groups according to relative wan thickness (normal

Determinants of tissue Doppler measures of regional diastolic function during dobutamine stress echocardiography

Background Diastolic dysfunction induced by ischemia may alter transmitral blood flow, but this reflects global ventricular function, and pseudonormalization may occur with increased preload. Tissue Doppler may assess regional diastolic function and is relatively load-independent, but limited data exist regarding its application to stress testing. We sought to examine the stress response of regional diastolic parameters to dobutomine echocardiography (DbE). Methods Sixty-three patients underwent study with DbE: 20 with low probability of coronary artery disease (CAD) and 43 with CAD who underwent angiography. A standard DbE protocol was used, and segments were categorized as ischemic, scar, or normal. Color tissue Doppler was acquired at baseline and peak stress, and waveforms in the basal and mid segments were used to measure early filling (Em), late filling (Am), and E deceleration time. Significant CAD was defined by stenoses >50% vessel diameter. Results Diastolic parameters had limited feasibility because of merging of Em and Am waves at high heart rates and limited reproducibility. Nonetheless, compared with normal segments, segments subtended with significant stenoses showed a lower Em velocity at rest (6.2 +/- 2.6 cm/s vs 4.8 +/- 2.2 cm/s, P < .0001) and peak (7.5 +/- 4.2 cm/s vs 5.1 +/- 3.6 cm/s, P < .0001), Abnormal segments also showed a shorter E deceleration time (51 +/- 27 ms vs 41 +/- 27 ms, P = .0001) at base and peak. No changes were documented in Am. The same pattern was seen with segments identified as ischemic with wall motion score. However, in the absence of ischemia, segments of patients with left ventricular hypertrophy showed a lower Em velocity, with blunted Em responses to stress. Conclusion Regional diastolic function is sensitive to ischemia. However, a number of practical limitations limit the applicability of diastolic parameters for the quantification of stress echocardiography.

Development of a fully quantitative approach to the interpretation of stress echocardiography using radial and longitudinal myocardial velocities

Background: Tissue Doppler may be used to quantify regional left ventricular function but is limited by segmental variation of longitudinal velocity from base to apex and free to septal walls. We sought to overcome this by developing a composite of longitudinal and radial velocities. Methods and Results. We examined 82 unselected patients undergoing a standard dobutamine echocardiogram. Longitudinal velocity was obtained in the basal and mid segments of each wall using tissue Doppler in the apical views. Radial velocities were derived in the same segments using an automated border detection system and centerline method with regional chords grouped according to segment location and temporally averaged. In 25 patients at low probability of coronary disease, the pattern of regional variation in longitudinal velocity (higher in the septum) was the opposite of radial velocity (higher in the free wall) and the combination was homogenous. In 57 patients undergoing angiography, velocity in abnormal segments was less than normal segments using longitudinal (6.0 +/- 3.6 vs 9.0 +/- 2.2 cm/s, P = .01) and radial velocity (6.0 +/- 4.0 vs 8.0 +/- 3.9 cm/s, P = .02). However, the composite velocity permitted better separation of abnormal and normal segments (13.3 +/- 5.6 vs 17.5 +/- 4.2 cm/s, P = .001). There was no significant difference between the accuracy of this quantitative approach and expert visual wall motion analysis (81% vs 84%, P = .56). Conclusion: Regional variation of uni-dimensional myocardial velocities necessitates site-specific normal ranges, probably because of different fiber directions. Combined analysis of longitudinal and radial velocities allows the derivation of a composite velocity, which is homogenous in all segments and may allow better separation of normal and abnormal myocardium.

Influence of left ventricular size and hemodynamics on the systolic longitudinal myocardial Doppler velocity response to stress

Background Systolic myocardial Doppler velocity accurately identifies coronary artery disease. However, these velocities may be affected by age, hemodynamic responses to stress, and left ventricular cavity size. We sought to examine the influences of these variables on myocardial velocity during dobutamine stress in patients with normal wall motion. Methods One hundred seventy-nine consecutive patients with normal dobutamine echocardiograms were studied. Color myocardial tissue Doppler data were obtained at rest and peak stress, and peak systolic myocardial velocity (PSV) was measured in all basal and midventricular segments. Velocities at rest and peak stress were compared with left ventricular diastolic and systolic volumes, blood pressure, heart rate, and age by Pearson correlation and interdecile analysis by use of analysis of variance. Results The only clinical variable correlating with velocity was age; PSV showed only mild correlation with age at rest (r(2) = 0.01, P = .001) and peak stress (r(2) = 0.02, P = .001), but the normal peak velocity was significantly different between the extremes of age (&lt;44 years and &gt;74 years). There was very weak correlation of PSV with systolic and diastolic blood pressure (r(2) &lt; 0.01), heart rate (r(2) &lt; 0.01), systemic vascular resistance (r(2) = 0.08), and left ventricular volumes (r(2) &lt; 0.01). Conclusions Peak systolic velocity during dobutamine stress is relatively independent of hemodynamic factors and left ventricular cavity size. The extremes of age may influence peak systolic Doppler velocities. These results suggest that peak systolic velocity may be a robust quantitative measure during dobutamine echocardiography across most patient subgroups.