Elisabetta Bianchini

Real-time Measurement System for Evaluation of the Carotid Intima-Media Thickness With a Robust Edge Operator

Objective. The purpose of this report is to describe an automatic real‐time system for evaluation of the carotid intima‐media thickness (CIMT) characterized by 3 main features: minimal interobserver and intraobserver variability, real‐time capabilities, and great robustness against noise. Methods. One hundred fifty carotid B‐mode ultrasound images were used to validate the system. Two skilled operators were involved in the analysis. Agreement with the gold standard, defined as the mean of 2 manual measurements of a skilled operator, and the interobserver and intraobserver variability were quantitatively evaluated by regression analysis and Bland‐Altman statistics. Results. The automatic measure of the CIMT showed a mean bias ± SD of 0.001 ± 0.035 mm toward the manual measurement. The intraobserver variability, evaluated with Bland‐Altman plots, showed a bias that was not significantly different from 0, whereas the SD of the differences was greater in the manual analysis (0.038 mm) than in the automatic analysis (0.006 mm). For interobserver variability, the automatic measurement had a bias that was not significantly different from 0, with a satisfactory SD of the differences (0.01 mm), whereas in the manual measurement, a little bias was present (0.012 mm), and the SD of the differences was noticeably greater (0.044 mm). Conclusions. The CIMT has been accepted as a noninvasive marker of early vascular alteration. At present, the manual approach is largely used to estimate CIMT values. However, that method is highly operator dependent and time‐consuming. For these reasons, we developed a new system for the CIMT measurement that conjugates precision with real‐time analysis, thus providing considerable advantages in clinical practice.

Assessment of Carotid Stiffness and Intima-Media Thickness From Ultrasound Data Comparison Between Two Methods

Objective. Increased arterial stiffness and carotid intima‐media thickness (IMT) are considered independent predictors of cardiovascular events. The aim of this study was to compare a system recently developed in our laboratory for automatic assessment of these parameters from ultrasound image sequences to a reference radio frequency (RF) echo‐tracking system. Methods. Common carotid artery scans of 21 patients with cardiovascular risk factors and 12 healthy volunteers were analyzed by both devices for the assessment of diameter (D), IMT, and distension (ΔD). In the healthy volunteers, analyses were repeated twice to evaluate intraobserver variability. Agreement was evaluated by Bland‐Altman analysis, whereas reproducibility was expressed as a coefficient of variation (CV). Results. Regarding the agreement between the two systems, bias values ± SD were 0.060 ± 0.110 mm for D, –0.006 ± 0.039 mm for IMT, and –0.016 ± 0.039 mm for ΔD. Intraobserver CVs were 2% ± 2% for D, 5% ± 5% for IMT, and 6% ± 6% for ΔD with the RF echo‐tracking system and 2% ± 1% for D, 6% ± 6% for IMT, and 8% ± 6% for ΔD with our automated system. Conclusions. Although B‐mode‐based devices are less precise than RF‐based ones, our automated system has good agreement with the reference method and comparable reproducibility, at least when high‐quality images are analyzed. Hence, this study suggests that the presented system based on image processing from standard ultrasound scans is a suitable device for measuring IMT and local arterial stiffness parameters in clinical studies.

Intima media thickness, pulse wave velocity, and flow mediated dilation

The identification of vascular alterations at the sub-clinical, asymptomatic stages are potentially useful for screening, prevention and improvement of cardiovascular risk stratification beyond classical risk factors.Increased intima-media thickness of the common carotid artery is a well-known marker of early atherosclerosis, which significantly correlates with the development of cardiovascular diseases. More recently, other vascular parameters evaluating both structural and functional arterial proprieties of peripheral arteries have been introduced, for cardiovascular risk stratification and as surrogate endpoints in clinical trials. Increased arterial stiffness, which can be detected by applanation tonometry as carotid-femoral pulse wave velocity, has been shown to predict future cardiovascular events and to significantly improve risk stratification.Finally, earlier vascular abnormalities such as endothelial dysfunction in the peripheral arteries, detected as reduced flow-mediated dilation of the brachial artery, are useful in the research setting and as surrogate endpoints in clinical trials and have also been suggested for their possible clinical use in the future.This manuscript will briefly review clinical evidence supporting the use of these different vascular markers for cardiovascular risk stratification, focusing on the correct methodology, which is a crucial issue to address in order to promote their use in future for routine clinical practice.

Comparison of two automatic methods for the assessment of brachial artery flow-mediated dilation.

Objectives Brachial artery flow-mediated dilation (FMD) is associated with risk factors providing information on cardiovascular prognosis. Despite the large effort to standardize the methodology, the FMD examination is still characterized by problems of reproducibility and reliability that can be partially overcome with the use of automatic systems. We developed real-time software for the assessment of brachial FMD (FMD Studio, Institute of Clinical Physiology, Pisa, Italy) from ultrasound images. The aim of this study is to compare our system with another automatic method (Brachial Analyzer, MIA LLC, IA, USA) which is currently considered as a reference method in FMD assessment. Methods The agreement between systems was assessed as follows. Protocol 1: Mean baseline (Basal), maximal (Max) brachial artery diameter after forearm ischemia and FMD, calculated as maximal percentage diameter increase, have been evaluated in 60 recorded FMD sequences. Protocol 2: Values of diameter and FMD have been evaluated in 618 frames extracted from 12 sequences. Results All biases are negligible and standard deviations of the differences are satisfactory (protocol 1: −0.27 ± 0.59%; protocol 2: −0.26 ± 0.61%) for FMD measurements. Analysis times were reduced (−33%) when FMD Studio is used. Rejected examinations due to the poor quality were 2% with the FMD Studio and 5% with the Brachial Analyzer. Conclusions In conclusion, the compared systems show a optimal grade of agreement and they can be used interchangeably. Thus, the use of a system characterized by real-time functionalities could represent a referral method for assessing endothelial function in clinical trials.

Cardiac reflections and natural vibrations: force-frequency relation recording system in the stress echo lab.

BackgroundThe inherent ability of ventricular myocardium to increase its force of contraction in response to an increase in contraction frequency is known as the cardiac force-frequency relation (FFR). This relation can be easily obtained in the stress echo lab, where the force is computed as the systolic pressure/end-systolic volume index ratio, and measured for increasing heart rates during stress. Ideally, the noninvasive, imaging independent, objective assessment of FFR would greatly enhance its practical appeal.Objectives1 – To evaluate the feasibility of the cardiac force measurement by a precordial cutaneous sensor. 2 – To build the curve of force variation as a function of the heart rate. 3 – To compare the standard stress echo results vs. this sensor operator-independent built FFR.MethodsThe transcutaneous force sensor was positioned in the precordial region in 88 consecutive patients referred for exercise, dipyridamole, or pacing stress. The force was measured as the myocardial vibrations amplitude in the isovolumic contraction period. FFR was computed as the curve of force variation as a function of heart rate. Standard echocardiographic FFR measurements were performed.ResultsA consistent FFR was obtained in all patients. Both the sensor built and the echo built FFR identifiy pts with normal or abnormal contractile reserve. The best cut-off value of the sensor built FFR was 15.5 g * 10-3 (Sensitivity = 0.85, Specificity = 0.77). Sensor built FFR slope and shape mirror pressure/volume relation during stress. This approach is extendable to daily physiological exercise and could be potentially attractive in home monitoring systems.

Transthoracic Sensor for Noninvasive Assessment of Left Ventricular Contractility: Validation in A Minipig Model of Chronic Heart Failure

Background:  Invasively measured left ventricular (LV) dP/dt is the accepted standard for measuring acute and chronic directional changes in LV contractility. Recently, we developed a noninvasive force sensor based on an accelerometer positioned on the chest, which measures the vibrations generated by isovolumic myocardial contraction. The aim of this paper was to compare noninvasive (accelerometer) versus invasive (LV dP/dt) indices of myocardial contractility in a chronic minipig model of pacing‐induced heart failure (HF). Comparative assessment was performed both at rest and following dobutamine infusion.

Arterial pressure changes monitoring with a new precordial noninvasive sensor

BackgroundRecently, a cutaneous force-frequency relation recording system based on first heart sound amplitude vibrations has been validated. A further application is the assessment of Second Heart Sound (S2) amplitude variations at increasing heart rates. The aim of this study was to assess the relationship between second heart sound amplitude variations at increasing heart rates and hemodynamic changes.MethodsThe transcutaneous force sensor was positioned in the precordial region in 146 consecutive patients referred for exercise (n = 99), dipyridamole (n = 41), or pacing stress (n = 6). The curve of S2 peak amplitude variation as a function of heart rate was computed as the increment with respect to the resting value.ResultsA consistent S2 signal was obtained in all patients. Baseline S2 was 7.2 ± 3.3 mg, increasing to 12.7 ± 7.7 mg at peak stress. S2 percentage increase was + 133 ± 104% in the 99 exercise, + 2 ± 22% in the 41 dipyridamole, and + 31 ± 27% in the 6 pacing patients (p < 0.05). Significant determinants of S2 amplitude were blood pressure, heart rate, and cardiac index with best correlation (R = .57) for mean pressure.ConclusionS2 recording quantitatively documents systemic pressure changes.

Abnormal shortened diastolic time length at increasing heart rates in patients with abnormal exercise-induced increase in pulmonary artery pressure

BackgroundThe degree of pulmonary hypertension is not independently related to the severity of left ventricular systolic dysfunction but is frequently associated with diastolic filling abnormalities. The aim of this study was to assess diastolic times at increasing heart rates in normal and in patients with and without abnormal exercise-induced increase in pulmonary artery pressure (PASP). Methods. We enrolled 109 patients (78 males, age 62 ± 13 years) referred for exercise stress echocardiography and 16 controls. The PASP was derived from the tricuspid Doppler tracing. A cut-off value of PASP ≥ 50 mmHg at peak stress was considered as indicative of abnormal increase in PASP. Diastolic times and the diastolic/systolic time ratio were recorded by a precordial cutaneous force sensor based on a linear accelerometer.ResultsAt baseline, PASP was 30 ± 5 mmHg in patients and 25 ± 4 in controls. At peak stress the PASP was normal in 95 patients (Group 1); 14 patients (Group 2) showed an abnormal increase in PASP (from 35 ± 4 to 62 ± 12 mmHg; P < 0.01). At 100 bpm, an abnormal (< 1) diastolic/systolic time ratio was found in 0/16 (0%) controls, in 12/93 (13%) Group 1 and 7/14 (50%) Group 2 patients (p < 0.05 between groups).ConclusionThe first and second heart sound vibrations non-invasively monitored by a force sensor are useful for continuously assessing diastolic time during exercise. Exercise-induced abnormal PASP was associated with reduced diastolic time at heart rates beyond 100 beats per minute.

Assessment of Carotid Elasticity During Exercise: A Reproducibility Study

The study aimed to evaluate the reproducibility of carotid elasticity during exercise. Eighteen healthy volunteers (nine males, age 34 ± 3 years, BMI 22 ± 6 kg/m(2)) underwent maximal exercise testing on a graded semi-supine cycle ergometer in two different sessions 3 days apart. Ultrasound B-mode image sequences of the right common carotid were acquired at different steps and analyzed by an automatic system; pressures were estimated by tonometry. Compliance (CC) and distensibility (DC) were significantly decreased at exercise peak and in the first recovery minute (CC from 1.6 ± 0.8 to 1 ± 0.6 mm^(2)/KPa, DC from 56.2 ± 25.3 to 34.5 ± 20 10^(-3)/KPa, p < 0.05). For the whole examination, intraclass coefficient was 0.780 for CC and 0.694 for DC. Mean coefficient of variation was maximum at peak exercise (CC = 19 ± 6%, DC = 24 ± 15%), but at first minute of recovery it was comparable to resting values (CC = 12 ± 9%, DC = 12 ± 11%). When designing future studies, acquisitions during first recovery minute might be preferred to peak measures.

Carotid and aortic stiffness in essential hypertension and their relation with target organ damage: the CATOD study

Objective: The objective of the study is to investigate in the hypertensive population the possible differential association between increased aortic and/or carotid stiffness and organ damage in multiple districts, such as the kidney, the vessels, and the heart. Methods: In 314 essential hypertensive patients, carotid–femoral pulse wave velocity (cfPWV, by applanation tonometry) and carotid stiffness (from ultrasound images analysis), together with left ventricular hypertrophy, carotid intima–media thickness, urinary albumin–creatinin ratio, and glomerular filtration rate were measured. Increased cfPWV and carotid stiffness were defined according to either international reference values or the 90th percentile of a local control group (110 age and sex-matched healthy individuals). Results: When considering the 90th percentile of a local control group, increased cfPWV was associated with reduced glomerular filtration rate, either when carotid stiffness was increased [odds ratio (OR) 13.27 (confidence limits (CL) 95% 3.86–45.58)] or not [OR 7.39 (CL95% 2.25–24.28)], whereas increased carotid stiffness was associated with left ventricular hypertrophy, either when cfPWV was increased [OR 2.86 (CL95% 1.15–7.09)] or not [OR 2.81 (CL95% 1.13–6.97)]. No association between increased cfPWV or carotid stiffness and target organ damage was found when cutoffs obtained by international reference values were used. The concomitance of both increased cfPWV and carotid stiffness did not have an additive effect on organ damage. Conclusion: Aortic and carotid stiffness are differentially associated with target organ damage in hypertensive patients. Regional arterial stiffness as assessed by cfPWV is associated with renal organ damage and local carotid stiffness with cardiac organ damage.