Ultra-selective carbon nanotubes for photoacoustic imaging of inflamed atherosclerotic plaques

Disruption of vulnerable atherosclerotic plaques often leads to myocardial infarction and stroke, the leading causes of morbidity and mortality in the United States. A diagnostic method that detects high-risk atherosclerotic plaques at early stages could prevent these sequelae. The abundance of immune cells in the arterial wall, especially inflammatory Ly-6Chi monocytes and foamy macrophages, is indicative of plaque‎ inflammation, and may be associated with plaque vulnerability. Hence, we sought to develop a new method that specifically targets these immune cells to offer clinically-relevant diagnostic information about cardiovascular disease. We combine ultra-selective nanoparticle targeting of Ly-6Chi monocytes and foamy macrophages with clinically-viable photoacoustic imaging (PAI) in order to precisely and specifically image inflamed plaques ex vivo in a mouse model that mimics human vulnerable plaques histopathologically. Within the plaques, high-dimensional single-cell flow cytometry (13-parameter) showed that our nanoparticles were almost-exclusively taken up by the Ly-6Chi monocytes and foamy macrophages that heavily infiltrate plaques. PAI identified inflamed atherosclerotic plaques that display ~6-fold greater signal compared to controls (P<0.001) six hours after intravenous injection of ultra-selective carbon nanotubes, with in vivo corroboration via optical imaging. Our highly selective strategy may provide a targeted, non-invasive imaging strategy to accurately identify and diagnose inflamed atherosclerotic lesions.

High birth weight was associated with increased radial artery intima thickness but not with other investigated cardiovascular risk factors in adulthood

AIM

This study investigated whether a high birth weight was associated with increased risk factors for cardiovascular disease when Swedish adults reached 34-40.

METHODS

We studied 27 subjects born at Uppsala University Hospital in 1975-1979, weighing at least 4500 g, and compared them with 27 controls selected by the Swedish National Board of Welfare with birth weights within ±1 standard deviations scores and similar ages and gender. The study included body mass index (BMI), blood pressure, lipid profile, haemoglobin A1c (HbA1c), C-reactive protein (CRP) and high-frequency ultrasound measurements of intima-media thickness, intima thickness (IT) and intima:media ratio of the carotid and radial arteries.

RESULTS

Subjects with a high birth weight did not differ from controls with regard to BMI, blood pressure, lipid profile, high-sensitivity CRP, HbA1c or carotid artery wall dimensions. However, their radial artery intima thickness was 37% greater than the control group and their intima:media ratio was 44% higher.

CONCLUSION

Our findings indicate that a high birth weight was associated with increased radial artery intima thickness, but not with other investigated cardiovascular risk factors, at 34-40 years of age. The clinical implications of these findings should be investigated further, especially in subjects born with a very high birth weight.

Thicknesses of individual layers of artery wall indicate increased cardiovascular risk in severe pre-eclampsia

OBJECTIVE

To assess whether thicknesses of the intima and media in the common carotid artery (CCA) and the intima/media ratio (I/M) indicate an increased cardiovascular risk in non-pregnant women with a history of previous severe pre-eclampsia.

METHODS

Thicknesses of the CCA intima and media layers were measured using non-invasive high-frequency (22 MHz) ultrasound in 42 women with a history of severe pre-eclampsia and 44 women with previous normal pregnancy.

RESULTS

Women with a history of severe pre-eclampsia had a thicker CCA intima and a higher I/M than had women with previous normal pregnancy, also after adjustment for mean arterial pressure, body mass index and CCA intima-media thickness (IMT) (all P < 0.0001). CCA-IMT did not differ significantly between groups. In receiver-operating characteristics curve analysis, intima thickness and I/M clearly discriminated between women with and those without previous pre-eclampsia (area under the receiver-operating characteristics curve (AUC), 0.98 and 0.93), whereas CCA-IMT did not (AUC, 0.52).

CONCLUSIONS

CCA individual intima and media thicknesses as well as I/M, but not CCA-IMT, reflect the known increased long-term cardiovascular risk of pre-eclampsia. Estimation of individual CCA layers using high-frequency ultrasound appears preferable to measuring CCA-IMT for investigating arterial effects and the increased cardiovascular risk in women with a history of severe pre-eclampsia.

Artery wall layer dimensions during normal pregnancy: a longitudinal study using noninvasive high-frequency ultrasound

The vascular effects of normal pregnancy were investigated by estimating the intima and media thicknesses of the common carotid artery separately using 22-MHz ultrasound (Collagenoson, Meudt, Germany) in 57 healthy women with normal pregnancies and pregnancy outcomes, in all three trimesters and at 1 yr postpartum. A thick intima, thin media, and high intima-to-media (I/M) ratio are signs of a less healthy artery wall. Mean artery wall layer dimensions remained fairly constant during pregnancy, but the intima thickness and I/M thickness ratio appeared to improve (decrease) postpartum (P < 0.001 for both). The cardiovascular risk parameters of age, body mass index, and blood pressure in the first trimester were associated with higher I/M ratios, especially in the second trimester, whereas higher serum estradiol levels were significantly associated with a lower I/M ratio. Changes from the first to second trimesters in I/M ratio, taking into account differential changes in intima and media thickness, were significantly (P < 0.05-0.001) associated with all risk parameters tested except age, which was associated with increased intima thickness (P = 0.02). Associations with third trimester values and changes from first to third trimesters were similar but less apparent. Thus, fairly constant mean artery wall layer dimensions during pregnancy appeared to improve postpartum. However, higher age, body mass index, or blood pressure and lower serum estradiol levels in the first trimester appeared to negatively affect the artery wall, strongly suggesting that pregnancy has negative vascular effects in some women. A less likely explanation involves possible adaptation to physiological changes during and after pregnancy.

Assessing individual cardiac risk using extra-cardiac arterial imaging

Cardiovascular disease is the leading cause of death globally. Cardiovascular risk factors predict the risk of cardiovascular events in populations but have limitations in predicting individual risk. Emerging technologies that non-invasively measure carotid intima media thickness, aortic pressure and brachial artery reactivity may be useful in identifying the vulnerable patient who may benefit from more aggressive preventive therapy. These tests vary between each other in their reproducibility, cost, required operator skill, availability and patient preparation. However, all require further validation for clinical use as screening tests for cardiovascular disease.

Combining carotid intima-media thickness with carotid plaque on screening for coronary heart disease

BACKGROUND

Ultrasound-detected carotid artery intima-media thickness (IMT) and carotid plaque are possible screening tests for coronary heart disease (CHD) among asymptomatic individuals.

OBJECTIVE

To assess the increase in screening performance of combining carotid IMT and plaque compared with each measurement alone in the identification of individuals with CHD.

METHODS

Ultrasound examination of left and right carotid arteries was performed on 100 individuals (median age 57), 55 with a history of CHD (unstable angina or myocardial infarction) and 45 without. IMT measurements were taken from the common carotid artery and plaque was identified above, at and below the carotid bifurcation. Associations between IMT and plaque were determined using logistic regression, and screening performance was assessed from the distributions of IMT and plaque among cases and controls.

RESULTS

At a false-positive rate of 5%, IMT (cut-off >0.75 mm) identified 30% (95% CI 14-58) of affected individuals. There was an increase in the detection rate of 8 percentage points (1-33%) using IMT and plaque combined compared with IMT alone. As the false-positive increased, the difference in the detection rate increased, up to a maximum of 20 percentage points (5-38%) at a false-positive rate of 20%. The comparison of IMT and plaque combined with plaque alone could only be estimated for the false-positive rate observed using plaque alone (18%); at this point the detection rate was 72% for plaque and 75% for plaque and IMT combined, an increase of 3 percentage points (0-4%).

CONCLUSION

In screening for CHD, combining carotid IMT measurement with plaque assessment is better than using either measurement alone, but the improvement in discrimination is not sufficient to make carotid ultrasound screening for CHD worthwhile.