Biomedical subjects

Alberto Righetti

Publications and source records attributed to Alberto Righetti.

9 recordsLinked to original sources

PubMed2006

Ventricular mechanical dyssynchrony and resynchronization therapy in heart failure: a new indication for Fourier analysis of gated blood-pool radionuclide ventriculography.

In patients with decreased left ventricular ejection fraction and conduction disease, ventricular mechanical dyssynchrony has been demonstrated. To date, resynchronization by biventricular pacing is increasingly used since it improves ventricular function and exercise capacity in patients with heart failure. To optimize and evaluate the effect of resynchronization therapy and to identify patients who may benefit from biventricular pacing the assessment of left ventricular synchronicity is essential. Therefore, a non-invasive and reproducible technique to obtain information on ventricular synchrony is clinically valuable. In this review, the technical background and the role of phase analysis of gated blood-pool nuclear ventriculography in the assessment of ventricular mechanical synchrony, especially in heart failure patients subjected to biventricular pacing, will be discussed.

Cardiac Pacing, Artificial↗

PubMed2005

Optimizing sequential biventricular pacing using radionuclide ventriculography.

BACKGROUND: Biventricular pacemakers are usually programmed with the default setting of synchronous biventricular pacing, although the ventricles may be paced sequentially. Whether this parameter is important for optimizing resynchronization therapy is not clear. OBJECTIVES: The purpose of this study was to investigate whether sequential pacing acutely improves left ventricular ejection fraction (LVEF) and dyssynchrony and to assess the feasibility of nuclear ventriculography for device optimization. METHODS: Twenty-seven patients implanted with a biventricular pacemaker or implantable cardioverter-defibrillator for heart failure were studied. LVEF was measured using planar radionuclide ventriculography during simultaneous biventricular pacing and during sequential pacing at four different interventricular intervals ranging from LV-40 (preexciting the left ventricle by 40 ms) to LV+40 (preexciting the right ventricle). Interventricular and intraventricular dyssynchrony were analyzed by phase analysis at each setting. RESULTS: There was great heterogeneity in individual response to VV interval programming. Twenty-four of 27 patients (89%) had significant changes (both favorable and unfavorable) in LVEF at different interventricular delays, with variations of up to 10% in absolute terms. Simultaneous biventricular pacing yielded maximal LVEF in 9 of 27 patients (33%), with a relative increase in LVEF of 18 +/- 14% by optimized sequential pacing in the remaining patients. Interventricular dyssynchrony varied significantly, with least dyssynchrony at the LV-20 setting (P = .024). There were no significant differences in intraventricular dyssynchrony at the different settings. CONCLUSION: Programming VV intervals has considerable impact on LVEF. However, there is a great degree of variation between patients in response to these settings, requiring individual assessment for device optimization.

Aged↗

PubMed2004

Comparison between tagged MRI and standard cine MRI for evaluation of left ventricular ejection fraction.

Global left ventricular function is a prognostic indicator and is used to evaluate therapeutical interventions in patients with heart failure. Regional left ventricular function can be determined with tagged MRI. Assessment of global left ventricular function using the tagging data may have additional clinical value without incurring extra scanning time, which is currently a limiting factor in cardiac imaging. Direct determination of end-diastolic volume is not possible with conventional tagged MRI. However, end-systolic volume can be directly measured because myocardium-blood contrast improves through a tagged image series. We investigated the potential of tagged MRI using frequency-domain analysis software to retrospectively track end-diastolic contour from end-systolic contour and subsequently calculate the ejection fraction. Tagged MRI was compared with the standard bright-blood cine MRI in healthy volunteers ( n=20) and patients with previous myocardial infarction ( n=8). Left ventricular ejection fraction derived from tagged MRI is linearly correlated to left ventricular ejection fraction obtained by standard cardiac cine MRI ( y=1.0 x+1.31, r>0.98, p=0.014). In addition, the inter-observer and intra-observer coefficient of variation for left ventricular ejection fraction measurements was low (CV(intra)=0.4%, CV(inter)=1.3%). With tagged MRI, only end-systolic volume needs to be manually determined, and accurate estimation of left ventricular ejection fraction is obtained because end-diastolic and end-systolic volumes are determined using identical anatomical points. Our data indicate that tagged MRI can be used to quantitatively assess both regional and global left ventricular function. Therefore, tagged MRI may be a valuable clinical tool for determining the prognosis and evaluating the effect of therapeutical intervention using a single imaging session in patients with left ventricular dysfunction.

Humans↗

PubMed2004

Vulnerability of myocardial collateral perfusion: the impact of episodic hypertension.

In patients with coronary artery disease, the presence of left ventricular hypertrophy secondary to hypertension is associated with an increased collateral development. A patient is described who was admitted for myocardial ischemia and severe hypertension. One day after admission, coronary angiography revealed a proximal chronic occlusion of the left anterior descending artery with an extensive collateral vascularization originating from the right and circumflex coronary arteries. In addition, left ventriculography showed antero-apical akinesia that was resolved 5 days later, indicating myocardial stunning. This case illustrates the vulnerability of collateral coronary blood flow to an episode of hypertension, giving rise to myocardial ischemia and even myocardial stunning. This finding advocates aggressive antihypertensive therapy in patients with coronary artery disease and regional myocardial perfusion, which exclusively depends on collateral blood flow.

Journal Article↗

PubMed2004

Site-specific intracoronary delivery of octreotide in humans: a pharmacokinetic study to determine dose-efficacy in restenosis prevention.

Somatostatin analogues have been shown to inhibit smooth muscle cell proliferation after local administration in vivo in animal models and in vitro using human coronary smooth muscle cell cultures. However, the optimal dosage for attaining effective site-specific administration remains undefined. This study was performed to determine the required theoretical dose of the somatostatin analogue, octreotide, to be delivered site specifically, for prevention of restenosis after coronary angioplasty in humans using a previously described methodology to determine regional pharmacokinetics of site-specific intracoronary administrated compounds. In 7 patients, 111In-octreotide, a gamma-labeled somatostatin analogue, was infused post angioplasty at the site of dilatation via a coil-balloon and quantified using a radio-isotopic technique. Efficiency of delivery ranged from 0.1% to 2.7% of the total infused dose of 0.18 microg, corresponding to a mean peak delivered amount of 1.8 +/- 1.9 ng. Total locally bioavailable 111In-octreotide reached 2.28 +/- 2.15 ng h. Based on current in vitro bioavailability and peak concentration data to inhibit proliferation and thymidine incorporation in human coronary smooth muscle cells, a 4000x higher averaged dose (approximately 700 microg) should be infused site specifically to obtain a biologic efficacy in 50% of the treated patients (ED50). Quantification of regional pharmacokinetics enables the determination of a theoretical site-specific dose for achieving appropriate bioavailability above the therapeutic threshold concentration for smooth muscle cell inhibition. This approach is proposed for the determination of the appropriate site-specific coronary infusion dose for the inhibition of restenosis after balloon angioplasty.

Angina, Unstable↗

PubMed2003

Inflow effect in first-pass cardiac and renal MRI.

PURPOSE: To estimate the effect of the inflow effect on the arterial input function in vivo in cardiac and renal MR perfusion imaging using fast gradient echo (GRE) sequences and contrast media. MATERIALS AND METHODS: The MR exam protocol was designed to acquire images at different phases of the cardiac cycle. The arterial input was thus influenced by various blood flow velocities. RESULTS: It was found that the inflow effect was negligible in the left ventricle of the heart, while it was significantly higher in the aorta for the kidney perfusion measurement. This was principally due to the higher through-the-plane component of the blood flow velocity in the aorta than in the left ventricle. CONCLUSION: The inflow effect can be neglected in the heart cavity, but should be taken into account in renal perfusion.

Aorta↗

PubMed2002

Use of high flip angle in T1-prepared FAST sequences for myocardial perfusion quantification.

This study reports on the first use of high flip angle and radio-frequency (RF) spoiling in T1-prepared fast acquisition in steady state (FAST) sequence for myocardial perfusion in patients. T1 dynamic range was measured in vitro with a FAST, an RF FAST and a snapshot fast low-angle shot (FLASH) sequences with a 90 degrees flip angle. Myocardial perfusion was then measured twice in 6 patients during the same MR session. The RF FAST and FLASH, but not the FAST sequence, demonstrated an extended T1 dynamic range; however, the FLASH images were degraded by artifacts not present on the RF FAST images. The myocardial perfusion indices K1 (first-order transfer constant from the blood to the myocardium for the Gd-DTPA) and Vd (distribution volume of Gd-DTPA in myocardium) did not differ significantly between the two injections. K1 was 0.48+/-0.12 ml/min g(-1) and Vd was 12.5+/-2.9%. With an extended T1 dynamic range and the sensitivity required for myocardial perfusion quantification, the RF FAST sequence with a 90 degrees flip angle outperformed the snapshot FLASH sequence in terms of image quality and the FAST sequence in terms of contrast dynamic range.

Adult↗

PubMedDate not supplied

Normal values and within-subject variability of cardiac I-123 MIBG scintigraphy in healthy individuals: implications for clinical studies.

BACKGROUND: Although several myocardial iodine 123 metaiodobenzylguanidine (MIBG) indices are increasingly used to detect alterations in myocardial sympathetic activity in various forms of cardiac pathology, published measurements of normal values and within-subject variability are lacking. METHODS AND RESULTS: Twenty-five healthy volunteers underwent planar and single photon emission computed tomography (SPECT) imaging. Heart-mediastinum ratio (H/M) and myocardial washout were calculated from planar images comparing three different methods for the assessment of myocardial activity: (1) global region over the myocardium (cavity included), (2) global region over the myocardium (cavity excluded), and (3) fixed small myocardial region. Segmental (relative) uptake and washout were assessed by SPECT. For all MIBG indices, the interindividual variation was the lowest for methods 1 and 2. In SPECT this variation was low for relative segmental uptake compared with washout. In 9 subjects a second MIBG scintigraphy was performed after 3 months. The within-subject variability of H/M and washout assessed by planar methods 1 and 2 was 5%, whereas it was approximately 9% for planar method 3. For relative segmental uptake from SPECT, this variability was 5%. CONCLUSION: MIBG H/M (planar) and relative segmental uptake (SPECT) show a low interindividual and within-subject variability. This enables the detection of small (regional) variations in myocardial sympathetic nervous function, especially to monitor the effect of therapeutic interventions in patients with various cardiac diseases.

3-Iodobenzylguanidine↗

PubMedDate not supplied

Inorganic species in water and sediments of the Lamone and Marzeno rivers ecosystem.

Analytical results are reported for the determination of inorganic species in water and sediments sampled in the Lamone and Marzeno rivers ecosystem. The species determined are Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn, Hg, F-, Cl- Br-, NO3-, SO4--, Na+, K+, Mg++, Ca++, NH4+ in superficial water, and Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn, Hg in sediments. For all the elements, in addition to detection limits, precision and accuracy are given: the former, expressed as relative standard deviation (s(r)), and the latter, expressed as relative error (e), were good, being in all cases lower than 6%.

Ecosystem↗