12 research outputs found
Principal component analysis of the t-wave for mortality Prediction in hemodialysis patients.
No full textPRINCIPAL COMPONENT ANALYSIS OF THE T-WAVE FOR MORTALITY
PREDICTION IN HEMODIALYSIS PATIENTS
Patients undergoing hemodialysis (HD) therapy often experience alterations in cardiac excitability and
have accounting for an estimated 3-year cumulative probability of cardiovascular death of 39.5% of
total deaths [1]. Abnormalities in ventricular repolarization and its dispersion could be a cause of HD-induced
arrhythmogenic effect.
Nowadays, no ECG-derived parameter has been proven to predict the risk of cardiovascular death.
QT dispersion (QTd) has been proposed, however, some concerns have been raised about uncertainty
of the QT dispersion measurement and technical difficulties in measuring the QT interval.
Principal component analysis (PCA) of the T-wave vector applied to 12-lead recordings has been
proposed to obtain an ECG marker of vulnerability to ventricular arrhythmias and of cardiovascular
mortality [2]. Several studies showed that the ratio of the second to first eigenvalues (PCA ratio) more
accurately represents repolarization abnormalities than QTd in a large general population sample [3,4].
The aim of this study was to explore the predictive value of the PCA ratio parameter for all-cause and
cardiac mortality in a retrospective study on HD patients.
METHODS
The selected subjects were 122 patients (46 women and 76 men, mean age 77±10) in whom digital
ECG recordings were available for the analysis from previous clinical studies. Standard holter 12-lead
recordings (H-12 Holter, Mortara Instrument Inc., Milwaukee, Wisconsin, USA) were collected
starting with the dialysis session. ECGs were sampled at 180 Hz or 1kHz and stored to a PC hard disk
for subsequent analysis.
PCA is an established method for representing data and, when applied to T-wave, it describes features
of repolarization in a manner that is less dependent on precise determination of T-wave offset.
Singular value decomposition was applied to the covariance matrix of the raw ECG data
corresponding to T-wave from the eight independent ECG leads. Then, the main eigenvectors of the
spatial T-wave were computed. The first eigenvector accounts for most of the energy in repolarization
when applied to the normal T-wave vector, whereas inhomogeneous repolarization, if present, is
indicated by a relevant contribution of the second and third components. Thus, the ratio of the second
to first eigenvalues of the spatial T-wave vector (PCA ratio) generated from the 12-lead digital ECG
serves as a measure of T-wave complexity or
heterogeneity of repolarization, with
increasing values referring to higher amount
of complexity. As shown in fig. 1 the PCA
ratio provides information that can be
visualized by analogy as the long and short
axes of the three-dimensional T-wave loop
and provides an estimate of the relative
fatness of the T-wave loop relative to its peak
amplitude, in which a fatter loop with a
higher PCA ratio reflects more complex Twave
morphology.
A median value of PCA was computed for
each patient throughout the whole ECG
recording. Following the Strong Heart Study
[3] a threshold for PCA ratio in men and
women, independently of gender, was
defined as 28%. Deaths were identified in an ongoing surveillance in each dialysis center and were
verified through review of medical records. Deaths were classified as cardiac if caused by myocardial
infarction, sudden death from CHD, or congestive heart failure by an independent review panel of
physicians unaware of PCA ratio findings. After a maximum follow-up of 5 years, patients were
censored as dead or alive considering the days from the date of the first ECG recording. Patients were
then divided in two groups depending on the median PCA ratio value. Endpoints were all-cause
mortality and cardiac mortality.
Mortality rates were calculated and plotted according to the Kaplan-Meier analysis. P<0.05 was
considered significant.
RESULTS AND DISCUSSION
During the fo..
Effects of Ca2+ and K+ Changes During Hemodialysis on Ventricular Repolarization Duration: in vivo and in silico Analysis.
No full textMETHOD FOR CLUSTERING HEMODIALYSIS (HD) PATIENTS BASED ON THE ESTIMATED WATER REFILLING INDEX (WRI).
No full textQT interval prolongation during haemodialysis (HD): in vivo and in silico analysis of the role of Ca2+ and K+ changes.
No full textMETODO PER IDENTIFICARE GRUPPI DI PAZIENTI IN EMODIALISI (HD) BASATO SULLA STIMA DEL PARAMETRO WATER REFILLING INDEX (WRI)
No full textInfluenza del calcio (Ca++) nel bagno dialisi AFB sull’emodinamica e sulla risposta elettro-fisiologica intradialitica.
No full textCalcium profiling in hemodiafiltration: a new way to reduce the calcium overload risk without compromising cardiovascular stability.
No full textLow and high dialysate calcium (Ca2+) content may have positive and harmful effects depending on the considered pathological aspect: hemodynamic instability, cardiac arrhythmias, parathormone release, adynamic bone disease, cardio-vascular calcifications. We hypothesized that a time-profiled Ca2+ concentration would keep the cardiovascular advantages of high Ca2+ but would reduce the risk of calcium overload.A prospective, multicenter study using a particular hemodiafiltration technique that allows the profiling of electrolytes was designed. Patients (n = 22) underwent randomly a 3-week dialysis session with low and high constant dialysate Ca2+ (Ld(Ca,), 1.25 mM and Hd(Ca,), 2 mM) and profiled Ca2+ (Pd(Ca)), respectively. Plasma and spent dialysate Ca2+, systolic and diastolic arterial pressure (SAP, DAP) and QT interval corrected for heart rate (QTc) were analyzed.Plasma Ca2+ concentration decreased in Ld(Ca), whereas it increased in Hd(Ca) and to a lesser extent, in Pd(Ca). Total amount of Ca2+ given to the patient in Pd(Ca) (15.5 ± 1.0 mmol) was higher than in Ld(Ca) (4.3 ± 1.6 mmol) but lower than in Hd(Ca) (21.9 ± 3.3 mmol). SAP and DAP decreased in Ld(Ca), whereas it was almost constant in both Hd(Ca) and Pd(Ca·). QTc significantly increased, up to critical values (>460 msec), only during Ld(Ca·).Pd(Ca) seems to retain the advantages of high Ca2+ in terms of hemodynamic stability and modification of QTc while reducing the excessive positive calcium balance typical of dialysis with high Ca2+ content
Influence of plasma potassium changes on the myocardial cell repolarization during hemodialysis
No full textDialysis therapy has a strong impact on cardiac excitability and the frequency of ectopic beats increases in the course of the session. Dispersion of ventricular repolarization could be a cause of the dialysis arrhythmogenic effect. In fact, QT dispersion increases during dialysis and this increase seems to be related to electrolyte, particularly potassium and calcium, concentration changes. However, some concerns have been raised about uncertainty of the QT dispersion measurement. Principal component analysis of the T wave applied to 12-lead ECG recording has been proposed as a novel approach to study the complexity of repolarization without having to determine the end of T-wave. The aim of this study was to assess and quantify the 24-hour changes in the complexity of ventricular repolarization in patients undergoing hemodialysis by means of principal components analysis. The effects of two dialysis protocols leading to different plasma potassium levels were also analyzed. Twelve patients were studied during Acetate Free Biofiltration with K+ profiling (AFBK). AFBK sessions were classified as Klow and Khigh on the basis of the dialyzate K+ concentration set at the start of the treatment. For each patient four sessions (2 Klow and 2 Khigh) were analysed. Holter 24-hour recordings were collected starting with the dialysis session. Principal components analysis was applied to the T wave automatically extracted from each beat and the repolarization complexity was quantified by the ratio of the second to the first eigenvalue (PCA ratio). Hemodialysis caused a significant increase in the PCA ratio (+50% at the end of the sessions). The PCA ratio recovered to the basal value during the first hour post-dialysis and kept stable during the subsequent 19 hours. When comparing Klow and Khigh sessions the PCA ratio increase was similar during the first two hours of dialysis but it was significantly higher in Klow sessions in the last two hours of dialysis, then the PCA ratio recovered to the same basal value. A difference in the occurrence of ventricular ectopic beats was also pointed out, being the number of premature ventricular contractions (PVCs) significantly higher in Klow sessions in the last three hours of treatment (p<0.05).
Results show that hemodialysis significantly increases the T wave complexity. Such an increase is related to the therapy-induced potassium depletion, with greater complexity when lower potassium levels are reached. Moreover, it can be hypothesized that repolarization dispersion changes underlie the observed increase in PVCs occurrence
Correlazione fra la concentrazione plasmatica di sodio e la conducibilità plasmatica in fasi diverse della sessione di emodialisi (HD)
No full textEvaluation of a New Online Hemodiafiltration Mode with Automated Pressure Control of Convection
No full text<i>Background:</i> Postdilution hemodiafiltration (HDF) still remains the gold standard for solute removal, but with high hemoglobin levels transmembrane pressure (TMP) may reach high levels, reducing filter performance. We compared three online postdilution HDF treatments without TMP alarms for convective volume and plasma changes following treatment. <i>Methods:</i> Twelve patients were enrolled in a trial with three online postdilution HDF treatments. In the volume-controlled mode (VOLc), we set the exchanged volume to obtain a filtration fraction close to 25% without TMP alarms. In the pressure-controlled mode (TMPc), we set the TMP at 100 mm Hg. In the ULTRAc mode (TMP scan combined with TMPc), the dialysis machine automatically selects the TMP with a scan. All treatments were performed with an AK200 ULTRA-S system. <i>Results:</i> Even with hemoglobin levels >12 g/dl, we found a 57% rise in ultrafiltration rate in TMPc versus VOLc and a 92% rise in ULTRAc versus VOLc. Phosphates and myoglobin levels were significantly affected by treatment type. <i>Conclusions:</i> ULTRAc may be a useful tool to achieve an excellent purification performance without the constraints associated with the risk of hemoconcentration.</jats:p
