Numbers of previous studies have evaluated the influence of dialysis-induced altered loading condition on Doppler-echocardiographic indices of left ventricle in patients with chronic renal failure. It has been suggested that most of Doppler-derived indices are preload-dependent. On the other hand, there are no studies that have evaluated the influence of hemodialysis on Tei index; a new Doppler-derived index obtained by isovolumetric contraction time plus isovolumetric relaxation time divided by ejection time. The aim of this study is to evaluate whether Tei index is also influenced by dialysis-induced altered loading condition as well as other Doppler-derived indices, and to assess the possibility that Tei index is also preload-dependent.
Thirty-two patients with chronic renal failure (21 men and 11 women, aged 48-93 years) on maintenance hemodialysis were evaluated for Doppler-derived indices before and after hemodialysis. We studied parameters of diastolic function (peak velocities of mitral inflow in early diastole (E) and late diastole from atrial filling (A), ratio of A to E (A/E), deceleration time (DT), and isovolumetric relaxation time (IRT)), parameters of systolic function (ejection time (ET), pre-ejection period (PEP), ratio of PEP to ET (PEP/ET), and isovolumetric contraction time (ICT)) and Tei index.
Hemodialysis resulted in significant decreases in E, increase in A/E, prolongation of IRT, no change in A and DT; significant prolongation of ICT and PEP, shortening of ET, and increase in PEP/ET and a significant increase in Tei index (0.42 +/- 0.16 vs 0.51 +/- 0.16, p < 0.0001). When patients were subdivided into 2 groups based on weight loss after hemodialysis (> or = 1.5 kg and < 1.5 kg), only the group that lost > or = 1.5 kg had significant change in Tei index before and after hemodialysis (0.40 +/- 0.15 vs 0.52 +/- 0.17, p = 0.0002).
This study demonstrates that not only most of Doppler-derived indices but also Tei index is affected by dialysis-induced altered loading condition and suggests that Tei index is possibly preload-dependent.
[Show abstract][Hide abstract] ABSTRACT: The Doppler index of overall left ventricular (LV) myocardial performance--the Tei index--has been shown to be a reliable indicator of all changes in LV systolic dysfunction, retaining an inverse relationship with the ejection fraction. The aim of this study was to examine the corresponding behaviour in relation to LV diastolic dysfunction in patients with acute myocardial infarction (AMI), a relationship that has not been studied previously.
The study included 105 patients (77 men) with first AMI who were classified into four groups according to the severity of LV diastolic dysfunction: a) 25 patients with normal diastolic function (NDF), b) 36 with decreased peak filling rate pattern (DFR), c) 33 with impaired relaxation (IR) and d) 11 with pseudonormal or restrictive physiology (PN/RP). A complete echocardiographic study, including all conventional systolic and diastolic echo/Doppler parameters as well as measurement of the Tei index, was performed on the eighth post-infarction day (mean 8.07 +/- 0.96 days) in all patients.
In the patients with IR (0.77 +/- 0.05) the index was significantly greater than in those of the NDF (0.55 +/- 0.03, p<0.01) or DFR (0.65 +/- 0.02, p<0.01) groups. The index in the DFR group was greater than in the NDF group, though not significantly so. In contrast, the index in the PN/RP patients (0.59 +/- 0.05) was significantly lower than in the patients with IR (p<0.01), whereas it did not differ from that of the patients in the NDF or DFR groups ("pseudonormalisation" of the index).
The Tei index detects with reliability milder types of diastolic dysfunction. However, because of its "pseudonormalisation" in patients with PN/RP, the Tei index cannot be considered a reliable indicator of more severe patterns of LV diastolic dysfunction in AMI patients.
[Show abstract][Hide abstract] ABSTRACT: Left ventricular (LV) diastolic function has been causally deteriorated on hypotensive episodes during hemodialysis (HD). The influence of intravascular volume deterioration and arterial pressure reduction on LV function in patients without hypotensive episodes during HD has not been adequately studied. 23 patients on HD were studied for 48±35 months, whose mean age was 50±12 years, their mean body mass index was 24±4kg/m2 and their mean fluid retention between HD sessions 2.2±1.1 kgr. We used 2D and Doppler echocardiography before and after the same HD session. The following parameters were measured: a) end-diastolic (LVED) and end-systolic LV diameters, left atrial diameter (LA) and fraction shortening (FS) b) isovolumic relaxation (IVRT) and contraction (ICT) time, deceleration time (DT), E and A waves of the mitral inflow and ejection time (ET) of the LV outflow velocity. The following indices were calculated: E/A ratio, myocardial performance index (MPI) using the (IVRT+ICT)/ET formula, mean arterial pressure (MAP), the % reduction in MAP and the reduction in intravascular volume after HD. Stroke volume (SV) and corresponding cardiac output (CO), were calculated from the LV outflow velocity waveform. All patients demonstrated systolic arterial pressure at the level of ≥90mmHg and normal FS before HD, while they had demonstrated restrictive LV diastolic filling before HD. MAP, SV, CO, LVED, LA, E wave and E/A decreased while IVRT increased after HD (p
[Show abstract][Hide abstract] ABSTRACT: For applications where extremely low-noise amplifiers are
demanded, RF SQUID parametric amplifiers offer significant capabilities.
We present results on the first RF SQUID parametric amplifiers (paramp)
fabricated using TRW's YBCO integrated circuit process technology. TRW's
paramps consist of thousands of RF SQUIDs distributed along and coupled
to ~7 cm coplanar transmission lines. We demonstrate two important
paramp functions: adjustable true time delay of RF signals and frequency
upconversion of 0 to 1 GHz base band signals to side bands of the ~10
GHz pump. When the input and output impedances are different the correct
figure of merit is upconversion transimpedance gain, shown to be
proportional to pump frequency and independent of base band frequency,
thereby providing wide band signal amplification. Finally, the spur-free
dynamic range for these first paramps is inferred from measurement and
modeling to be ~82 dB-√Hz
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