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G D Pinna

Publications and source records attributed to G D Pinna.

At least 19 recordsLinked to original sources
PubMed2005

Noninvasive measurement of blood pressure variability: accuracy of the Finometer monitor and comparison with the Finapres device.

To assess the accuracy of spectral indices of arterial pressure variability and baroreflex sensitivity obtained from beat-by-beat noninvasive blood pressure recordings by the Finometer device, we compared these measures with those obtained from intra-arterial recordings. The performance of the Finometer was also compared to the traditional Finapres device. In 19 cardiac disease patients, including myocardial infarction, heart failure and cardiac transplant, we estimated the power of systolic and diastolic pressures in the VLF (0.01-0.04 Hz), LF (0.04-0.15 Hz) and HF (0.15-0.45 Hz) bands and computed absolute and percentage errors relative to intra-arterial brachial pressure. We also computed the characteristic frequency of each band (i.e. the barycentric frequency of spectral components identified in the band). The variability of systolic pressure in the VLF and LF bands was markedly overestimated by both the Finometer and Finapres (p < 0.01), with percentage median errors of respectively 130% and 103% (Finometer), and 134% and 78% (Finapres). The HF power was substantially unchanged using the Finometer and reduced using the Finapres (-28%, p < 0.05). The limits of agreement between noninvasive and invasive spectral measurements were wide. Linear system analysis showed that most (>80%) of the power of noninvasive signals was linearly related to the power of the invasive signal. The characteristic frequency of each band was substantially preserved in both noninvasive signals. The results for diastolic pressure were similar, but the Finapres errors in the VLF and LF bands were lower. Baroreflex sensitivity was significantly underestimated by both devices (Finometer: -31%, Finapres: -24%). Despite previous studies having shown that brachial artery waveform reconstruction performed by the Finometer has improved the accuracy of blood pressure measurement compared to the Finapres device, measurement of blood pressure variability in cardiac disease patients provides worse results in most spectral parameters and a better accuracy only in the HF band of systolic pressure.

Adult↗
PubMed2005

Effect of paced breathing on ventilatory and cardiovascular variability parameters during short-term investigations of autonomic function.

Paced breathing (PB) around 0.25 Hz has been advocated as a means to avoid confounding and to standardize measurements in short-term investigations of autonomic cardiovascular regulation. Controversy remains, however, as to whether it causes any alteration in autonomic control. We addressed this issue in 40 supine, middle-aged, healthy volunteers by assessing the changes induced by PB (0.25 Hz for 8 min) on 1) ventilatory parameters, 2) the indexes of autonomic control of cardiovascular function, and 3) the spectral indexes of cardiovascular variability. Subjects were grouped into group 1 (n = 31), if spontaneous breathing was regular and within the high-frequency (HF) band (0.15-0.45 Hz), or group 2 (n = 9), if it was irregular or slow (< 0.15 Hz). In both groups, PB was accompanied by an increase in minute ventilation (both groups, P < 0.01), whereas tidal volume increased only in group 1 (P = 0.0003). End-tidal CO2 decreased by [median (lower quartile, upper quartile)] -0.2 (-0.5, -0.1)% (group 1, P < 0.0001) and -0.6 (-0.8, -0.5)% (group 2, P = 0.008). Mean R-R interval and systolic and diastolic pressure remained remarkably stable (all P > or = 0.13, both groups). No significant changes were observed in spectral indexes of R-R and pressure variability (all P > or = 0.12, measured only in group 1 to avoid confounding), except in the HF power of pressure signals, which significantly increased (all P < 0.05) in association with increased tidal volume. In conclusion, PB at 0.25 Hz causes a slight hyperventilation and does not affect traditional indexes of autonomic control or, in subjects with spontaneous breathing in the HF band, most relevant spectral indexes of cardiovascular variability. These findings support the notion that PB does not alter cardiovascular autonomic regulation compared with spontaneous breathing.

Autonomic Nervous System↗
PubMed2005

Leave-one-out prediction error of systolic arterial pressure time series under paced breathing.

In this paper, we consider systolic arterial pressure time series from healthy subjects and chronic heart failure patients, undergoing paced respiration, and show that different physiological states and pathological conditions may be characterized in terms of predictability of time series signals from the underlying biological system. We model time series by the regularized least-squares approach and quantify predictability by the leave-one-out error. We find that the entrainment mechanism connected to paced breath, that renders the arterial blood pressure signal more regular and thus more predictable, is less effective in patients, and this effect correlates with the seriousness of the heart failure. Using a Gaussian kernel, so that all orders of nonlinearity are taken into account, the leave-one-out error separates controls from patients (probability less than 10(-7)), and alive patients from patients for whom cardiac death occurred (probability less than 0.01).

Algorithms↗
PubMed2005

Nutritional status and airflow obstruction: two independent contributors to CO diffusing capacity impairment in COPD.

BACKGROUND: The association between weight loss and Chronic Obstructive Pulmonary Disease (COPD) has been recognised from many years. Based on the evidence that nutritional status reflects metabolic disturbances in COPD, the relationship between body mass index (BMI), severity of airflow obstruction and CO diffusing capacity (DL(CO)), that is the functional hallmark of emphysema, is relevant to the management of COPD phenotypes. METHODS: We reviewed 104 patients with COPD (82 males), aged 66 +/- 9 years (mean +/- SD). Height averaged 165 +/- 8 cm, weight 71 +/- 16 Kg, FEV1 50 +/- 18 (% of predicted), RV 169 +/- 49%, and DL(CO) 56 +/- 26%. Multiple linear regression was performed using BMI, FEV1 and RV, as explanatory variables for DL(CO). Patients were also classified into four groups according to BMI < or = 18.5 (low), > 18.5 and < or = 25 (ideal), > 25 and < or = 30 (overweight), > 30 (obese), and post-bronchodilator FEV1 < 50%. Using this categorisation, a two-factor analysis of variance, testing for interaction and main effects (BMI and FEV1) was performed as confirmatory analysis for the association between BMI (kg/m2), FEV1% and DL(CO)%. RESULTS: FEV1 and BMI were significantly and independently associated to DL(CO) according to the equation: DL(CO) = -18.32 + 0.65 x FEV1 + 1.59 x BMI (R2 = 0.40, p < 0.0001). The contribution of RV % to DL(CO) % was largely non-significant (p = 0.16). A close relationship was found between BMI (kg/m2) and DL(CO) %, for all of the four BMI groups segregated by post-bronchodilator FEV1 %, (p < .0001). No interaction was found between these two factors (p = 0.30). CONCLUSION: Nutritional status as assessed by BMI contributes substantially to impairment of DL(CO) independently of the severity of airflow obstruction. This data confirms the association between emphysematous process and weight loss in advanced COPD, independent of the airflow obstruction severity.

Adult↗
PubMed2004

Phase shifts of synchronized oscillators and the systolic-diastolic blood pressure relation.

We study the phase-synchronization properties of systolic and diastolic arterial pressure in healthy subjects. We find that delays in the oscillatory components of the time series depend on the frequency bands that are considered, in particular we find a change of sign in the phase shift going from the very low frequency band to the high frequency band. This behavior should reflect a collective behavior of a system of nonlinear interacting elementary oscillators. We prove that some models describing such systems, e.g., the Winfree and the Kuramoto models, offer a clue to this phenomenon. For these theoretical models there is a linear relationship between phase shifts and the difference of natural frequencies of oscillators and a change of sign in the phase shift naturally emerges.

Biological Clocks↗
PubMed2002

New criteria for estimating baroreflex sensitivity using the transfer function method.

Computer simulations were carried out to appraise three new criteria for the estimation of baroreflex sensitivity (BRS) using the transfer function method. The major goal was to identify a computation procedure able to overcome the intrinsic limitations of the classical coherence criterion. Four representative shapes of the gain function and three different average gains (2, 5 and 8 ms(mmHg)(-1) in the low-frequency (LF) band (0.04-0.15Hz) were considered. The signal-to-noise ratio was made to vary so that the peak coherence in the LF band changed from 0.15 to 0.9. All simulation parameters were derived from previous observations in healthy subjects and heart disease patients. The error of the estimated gain function was obtained from its confidence interval. BRS was computed as average gain in the LF band: (a) including in the average only those points having error < or = threshold (criterion 1, C1); (b) calculating the mean error in the band and accepting BRS measurements only when this error was < or = threshold (criterion 2, C2); (c) including in the average all points, regardless of the error (criterion 3, C3). The three criteria were compared in terms of measurability (percentage of measured BRS) and accuracy (bias and SD of BRS). Using C1 and C2, measurability dropped to 10% when the peak coherence in the LF band decreased, respectively, to 0.18-0.41 and to 0.26-0.53, depending on the shape and strength of the gain. In this condition (lower bound of measurability), worst bias and SD (average gain: 8 ms(mmHg)(-1)) were, respectively, 0.8 ms(mmHg)(-1) and 3.3ms(mmHg)(-1) (C1), and 0.1 ms(mmHg)(-1) and 1.0 ms(mmHg)(-1) (C2). C3, by definition, always ensured 100% measurability and showed bias and SD comparable with, or even lower than, C1 and C2, within the common range of measurable BRS. In the extreme condition of 0.15 coherence, bias and SD were, respectively, 1.7 ms(mmHg)(-1) and 2.3ms(mmHg)(-1) (average gain: 8ms(mmHg)(-1)). Hence, error checking (C1 and C2) dramatically reduced measurability and did not improve accuracy of BRS measurements compared with performing no error check (C3). In conditions of low signal-to-noise ratio and/or impaired baroreflex gain, leading to markedly reduced coherence, the simple average of the gain function in the LF band allows BRS to be estimated with accuracy adequate for clinical purposes.

Baroreflex↗
PubMed2002

RESP-24: a computer program for the investigation of 24-h breathing abnormalities in heart failure patients.

In this paper, we describe a computer program (RESP-24) specifically devised to assess the prevalence and characteristics of breathing disorders in ambulant chronic heart failure patients during the overall 24 h period. The system works on a single channel respiratory signal (RS) recorded through a Holter-like portable device. In the pre-processing stage RESP-24 removes noise, baseline drift and motion artefacts from the RS using a non-linear filter, enhances respiratory frequency components through high-pass filtering and derives an instantaneous tidal volume (ITV) signal. The core processing is devoted to the identification and classification of the breathing pattern into periodic breathing (PB), normal breathing or non-classifiable breathing using a 60 s segmentation, and to the identification and estimation of apnea and hypopnea events. Sustained episodes of PB are detected by cross analysis of both the spectral content and time behavior of the ITV signal. User-friendly interactive facilities allow all the results of the automatic analysis procedure to be edited. The final report provides a set of standard and non-standard parameters quantifying breathing abnormalities during the 24 h period, the night-time and the day-time, including the apnea/hypopnea index, the apnea index, the total time spent in apnea or in hypopnea and the prevalence of non-apneic and apneic PB. The accuracy of these measurements was appraised on a data set of 14 recordings, by comparing them with those provided by a trained analyst. The mean and standard deviation of the error of the automatic procedure were below respectively 6 and 8% of the reference value for all parameters considered and the mean total classification accuracy was 92%. In most cases, the individual error was <12%. We conclude that measurements provided automatically by the RESP-24 software are suitable for screening purposes and clinical trials, although a preventive check of signal quality should be recommended.

Apnea↗
PubMed2002

Left atrial function: bridge to central and hormonal determinants of exercise capacity in patients with chronic heart failure.

UNLABELLED: The stroke volume response to exercise is a critical determinant in meeting peripheral metabolic demands in patients with chronic hear failure. The Left atrium, by its position, is important in coupling right and left ventricles, to left preload reserve and to modulate sympathetic activity. We performed this study to investigate the relationship between exercise capacity and diastolic and systolic left atrium function in patients with chronic heart failure. METHODS: We considered 128 consecutive patients with severe chronic heart failure (EF < 35%) due to ischemic or idiopathic dilated cardiomyopathy. Cardiac output, right atrial pressure, pulmonary artery pressures and mean pulmonary wedge pressure (A, X, V, Y wedge pressures) were determined during right cardiac catheterization. By Echocardiography evaluation, we measured atrial pressures and volume during early and late left atrial systolic filling and we calculated left atrial chamber stiffness by this equation P = A*eKV1. (P = left atrial pressure; A = elastic constant (mmHg*ml); e = the base of the natural logarithm; V1 = left atrial volume (ml); K = left atrial chamber stiffness constant (ml-1) = ln (V/X)/(maximal--minimal left atrial volumes)). All patients performed cardiopulmonary exercise test with modified Noughton protocol. Plasma norepinephrine and Atrial natriuretic factor levels were determined. RESULTS: Maximal and minimal left atrial volumes were inversely related to oxygen consumption (r = -.44, p < .001; r = -.61, p < .001). At rest, no differences were found in plasma norepinephrine concentrations (309 +/- 152 pg/ml vs 309 +/- 394 pg/ml; p = ns) and systemic vascular resistance (1706 +/- 435 vs 1771 +/- 524 dynes/cm sec-5; p = ns) in patients with large or normal left atrial volumes. During exercise the chronotropic response increased less in patients with large atrial volumes (56 +/- 13 vs 45 +/- 14; p = .001). The left atrial chamber stiffness constant was inversely related to peak oxygen consumption and exercise time. Patients with different chamber stiffness showed statistical difference in peak VO2 (16 +/- 4 vs 11 +/- 3 ml/kg/min; p = .0001). Left atrial ejection fraction was directly related to peak oxygen consumption (r = 0.55), but the most strongly correlation was with atrial filling fraction (r = .67). CONCLUSIONS: This study demonstrates a strong relationship between left atrial function and exercise capacity in patients with chronic heart failure.

Chronic Disease↗
PubMed2001

Echo-Doppler mitral flow monitoring: an operative tool to evaluate day-to-day tolerance to and effectiveness of beta-adrenergic blocking agent therapy in patients with chronic heart failure.

OBJECTIVES: The goals of this study were: 1) to assess the predictive value of baseline mitral flow pattern (MFP) and its changes after loading manipulations as regards tolerance to and effectiveness of beta-adrenergic blocking agent treatment in patients with chronic heart failure (CHF); and 2) to analyze the prognostic implications of chronic MFP modifications after beta-blocker treatment. BACKGROUND: In patients with CHF, carvedilol therapy induces clinical and hemodynamic improvements. Individual management, clinical effectiveness and prognostic implications, however, remain unclear. The MFP changes induced by loading manipulations provide independent prognostic information. METHODS: Echo-Doppler was performed at baseline and after loading manipulations in 116 consecutive patients with CHF (left ventricular ejection fraction: 25 +/- 7%); 54 patients with a baseline restrictive MFP were given nitroprusside infusion; 62 patients with a baseline nonrestrictive MFP performed passive leg lifting. According to changes in MFP, we identified four groups: 17 with irreversible restrictive MFP (Irr-rMFP), 37 with reversible restrictive MFP (Rev-rMFP), 12 with unstable nonrestrictive MFP (Un-nrMFP) and 50 with stable nonrestrictive MFP (Sta-nrMFP). Carvedilol therapy (44 +/- 27 mg) was administered blind to results of loading maneuvers. After six months, MFP was reassessed and patients reclassified according to chronic MFP changes. During follow-up, tolerance to and effectiveness of treatment and major cardiac events (death, readmission and urgent transplantation) were considered. RESULTS: Changes of MFP after loading manipulations were more accurate than baseline MFP in predicting both tolerance to (p < 0.01) and effectiveness of (p < 0.05) carvedilol. After 26 +/- 14 months of follow-up, cardiac events had occurred in 23/102 patients (23%). The event rate in patients with chronic Irr-rMFP or Un-nrMFP was markedly higher than it was in those with Rev-rMFP or Sta-nrMFP. CONCLUSIONS: In our patients, tolerance to and effectiveness of carvedilol was predicted better by echo-Doppler MFP changes after loading manipulations than by baseline MFP. Chronic changes of MFP after therapy are strong predictors of major cardiac events.

Adrenergic beta-Antagonists↗
PubMed2001

Baroreflex sensitivity and heart rate variability in the identification of patients at risk for life-threatening arrhythmias: implications for clinical trials.

BACKGROUND: The need for accurate risk stratification is heightened by the expanding indications for the implantable cardioverter defibrillator. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) focused interest on patients with both depressed left ventricular ejection fraction (LVEF) and the presence of nonsustained ventricular tachycardia (NSVT). Meanwhile, the prospective study Autonomic Tone and Reflexes After Myocardial Infarctio (ATRAMI) demonstrated that markers of reduced vagal activity, such as depressed baroreflex sensitivity (BRS) an heart rate variability (HRV), are strong predictors of cardiac mortality after myocardial infarction. METHODS AND RESULTS: We analyzed 1071 ATRAMI patients after myocardial infarction who had data on LVEF, 24-hour ECG recording, and BRS. During follow-up (21 +/- 8 months), 43 patients experienced cardiac death, 5 patients had episodes of sustained VT, and 30 patients experienced sudden death and/or sustained VT. NSVT, depressed BRS, or HRV were all significantly and independently associated with increased mortality. The combination of all 3 risk factor increased the risk of death by 22x. Among patients with LVEF<35%, despite the absence of NSVT, depressed BRS predicted higher mortality (18% versus 4.6%, P = 0.01). This is a clinically important finding because this grou constitutes 25% of all patients with depressed LVEF. For both cardiac and arrhythmic mortality, the sensitivity of lo BRS was higher than that of NSVT and HRV CONCLUSIONS: BRS and HRV contribute importantly and additionally to risk stratification. Particularly when LVEF is depressed, the analysis of BRS identifies a large number of patients at high risk for cardiac and arrhythmic mortalit who might benefit from implantable cardioverter defibrillator therapy without disproportionately increasing the number of false-positives.

Arrhythmias, Cardiac↗
PubMed2001

Reliability of transfer function estimates in cardiovascular variability analysis.

Transfer function (TF) analysis is a widely diffused technique in the assessment of the relationship between short-term cardiovascular variability signals, particularly blood pressure, heart rate and respiration. To guarantee the reliability of the estimates, a conventional threshold of 0.5 on the magnitude squared coherence (MSC) is commonly used, although (i) other analysis parameters play a role and (ii) lower values of MSC are frequently unavoidable in physiological systems. In this study, computer simulations are performed to assess the dependency of the bias and standard deviation (SD) of TF estimates on record length (RL), spectral window bandwidth (Bw) and MSC; to evaluate the accuracy of theoretical expressions for the computation of the confidence interval (CI) of the estimates; and to assess, in some representative situations, how faithfully observed TF shapes reproduce the underlying true functions in conditions of very low MSC. The accuracy of TF estimates increases non-linearly with increasing RL, and the benefit over 7 min is small. Using this RL, the relative bias for the TF modulus is < 10% for MSC > 0.2. Estimates of TF phase are unbiased. The SD of both the modulus and phase increases linearly as the MSC decrease to 0.4 and then, for lower MSC, increases markedly with nonlinear behaviour. Bw= 0.03Hz appears to be most suitable to reduce the error, preserving spectral resolution. CIs for the TF phase are highly reliable, whereas those for the modulus tend to be slightly narrower than the nominal value at high coherence values. Major features of the TF shape appear to be preserved in simulations with very low MSC. The major problem in TF estimation is the sharp increase in the variability of the measurements as the coherence decreases towards the lowest values. The combination of RL > or = 420s and Bw= 0.03Hz should be suggested in short-term cardiovascular variability studies. Although basic features of the true TF can be recovered even when the MSC is < 0.5, much greater values can be necessary when accurate point estimates are needed. Theoretical expressions for the computation of confidence intervals of the TF are adequate for practical purposes.

Blood Pressure↗
PubMed2001

Chronic infusion of dobutamine and nitroprusside in patients with end-stage heart failure awaiting heart transplantation: safety and clinical outcome.

BACKGROUND: in patients with severe heart failure additional therapeutic support with intravenous inotropic or vasodilator drugs is frequently employed in an attempt to obtain hemodynamic and clinical control. No data comparing the use and efficacy of chronic intravenous inotropic and vasodilator therapy in patients with advanced heart failure are available. AIMS: we evaluated, in a group of patients with advanced heart failure undergoing chronic infusion with dobutamine or nitroprusside, in addition to optimized oral therapy, (1) the safety of chronic infusion, (2) the efficacy of both drugs in managing unloading therapy and (3) clinical outcome of the two therapeutic strategies. METHODS: one hundred and thirteen patients receiving optimized oral therapy, in functional class III/IV with symptoms and signs of refractory heart failure and requiring additional pharmacological support with either intravenous dobutamine or nitroprusside were evaluated. Clinical and therapeutic management and clinical outcome of the two groups were considered. RESULTS: dobutamine was administered for 12 h/day for 20+/-23 days at a dosage of 7+/-3 microg/kg/min to 43 patients. The mean dose of nitroprusside was 0.76+/-0.99 microg/kg/min. The mean duration of use of this drug, administered as a 12-h/day infusion was 22+/-38 days. Nitroprusside infusion allowed greater doses of short-term ACE-inhibitors to be used compared to pre-infusion (ACE-inhibitor dose: 55+/-30 mg/day vs. 127+/-30 mg/day P<0.0001) and during dobutamine infusion (ACE-inhibitor dose: 85+/-47 mg/day vs. 127+/-30 mg/day P<0.002). Nitroprusside unlike dobutamine significantly improved the NYHA functional class. Of the 113 patients, 109 (97%) had a cardiac event during a mean follow-up of 337+/-264 days. Forty-four patients required hospitalization for worsening congestive heart failure, 45/113 (39%) patients died during the follow-up and 27/113 (24%) patients had a heart transplant in status one. Hospitalization, because of worsening heart failure was less frequent in the nitroprusside than in the dobutamine subgroup [29/51 (57%) vs. 19/22 (86%) P<0.02]. The overall mortality was 28% (20/70) in the nitroprusside group and 58% (25/43) in the dobutamine group (odds ratio 0.33 CI 0.16 to 0.73 P<0.006). In the group treated with nitroprusside, heart transplantation in status one was performed in 16/33 patients (48%), while in the dobutamine group this was done in 11/14 patients (78%) (odds ratio 0.25 CI 0.06-1.02 P<0.06). There was a significant reduction in the combined end-point of mortality/heart transplantation in status one in patients treated with nitroprusside compared to those treated with dobutamine (36/70 (51%) vs. 36/43 (84%) - (odds ratio 0.34 CI 0.14-0.80 P<0.01). The incidence of adverse events in the patients treated with nitroprusside was similar to that in those treated with dobutamine (20% vs. 17% P=ns). CONCLUSIONS: for patients awaiting heart transplantation chronic intermittent nitroprusside infusions are more effective and safer than dobutamine in relieving symptoms, facilitating unloading therapy management and improving survival. Whether chronic intermittent infusion of nitroprusside could represent a feasible medical strategy in out-patients with severe heart failure remains to be investigated.

Cardiac Output, Low↗
PubMed2001

Six-minute walking performance in patients with moderate-to-severe heart failure; is it a useful indicator in clinical practice?

AIMS: The 6-min walk test has been incorporated into studies on the efficacy of new therapies and into prognostic stratification for chronic heart failure patients. Firm conclusions on the usefulness of the test in clinical practice are still lacking. The aim of this study was to investigate (1) the correlation between walk test performance and standard indices of cardiac function and exercise capacity, and (2) the prognostic value of the walk test with respect to peak VO2 and NYHA class. METHODS AND RESULTS: Three hundred and fifteen chronic heart failure patients (age: 53+/-9 years, NYHA class: II (182), III (133)) underwent a functional evaluation and a 6-min walk test. Of these, 270 were followed-up for a minimum of 6 months (mean 387+/-177 days). Walked distance was 396+/-92 m. There was no significant correlation between distance walked and central haemodynamic data. Functional capacity, as measured by ergometry, correlated moderately with distance walked (duration: r=0.48, peak VO2: r=0.59, anaerobic threshold: r=0.54; all P<0.001). During follow-up, 46 patients died from cardiovascular causes and 12 were urgently transplanted. Either of these events were considered end points of the study. Survival analysis was performed from a continuous walk test and peak VO2 measurements or after categorization of (a) quartile segmentation, (b) cut-off points from the literature and (c) thresholds from receiver operating characteristic curves. At univariate survival analysis (Cox regression), the association of the walk test with survival was of significance (P=0.03, continuous variable), or borderline significance (0.05< or =P< or =0.1, after categorization). Peak VO2 was always significant, independent of the scale used (0.005< or =P< or =0.03). The strongest association was found for NYHA class (P<0.001), which showed the highest sensitivity and specificity for the prediction of the event (0.64 and 0.65, respectively). When walk test performance, continuous or categorized, was entered into a multivariate model with NYHA class or peak VO2, it lost any significant association with survival (P>0.76 in all models with NYHA class and P>0.27 in all models with peak VO2). CONCLUSION: In moderate-to-severe chronic heart failure patients, the 6-min walk test is not related to cardiac function and only moderately related to exercise capacity. Walking performance does not provide prognostic information which can complement or substitute for that provided by peak VO2 or NYHA class. Hence the test is of limited usefulness as a decisional indicator in clinical practice.

Adult↗
PubMed2001

Assessment of baroreflex sensitivity in patients with preserved and impaired left ventricular function by means of the Valsalva manoeuvre and the phenylephrine test.

The purpose of the present study was to assess the agreement between measurements of baroreflex sensitivity (BRS) obtained by the Valsalva manoeuvre and by the phenylephrine test in patients with previous myocardial infarction and different degrees of left ventricular dysfunction. Patients with a previous myocardial infarction were enrolled consecutively into two groups according to their left ventricular ejection fraction (LVEF): 40% (n=52). All patients underwent BRS assessment by the phenylephrine technique (Phe-BRS) and by the Valsalva manoeuvre, with the latter using both the overshoot part of phase IV (Ov-VM-BRS) and the whole of phase IV (IV-VM-BRS). The linear association between methods was assessed by correlation analysis and the agreement was evaluated by computing the bias and the limits of agreement. IV-VM-BRS and Ov-VM-BRS could not be computed in 26% and 39% of patients respectively. For both indices a much higher percentage of non-computable Valsalva manoeuvre slopes was found in the group of patients with LVEF 40% the results were: r=0.91 (P<0.001), bias=0.1 ms/mmHg (P=0.84) and limits of agreement from -4.8 to 5 ms/mmHg. When comparing Phe-BRS and IV-VM-BRS, we found r=0.67 (P=0.001), bias=-1.5 ms/mmHg (P=0.06) and limits of agreement from -8.8 to 5.7 ms/mmHg in the group of patients with LVEF 40%. Dichotomizing Ov-VM-BRS, the best cut-off value to identify patients with a Phe-BRS of <3 ms/mmHg was found to be 7 ms/mmHg, giving 100% sensitivity and 69% specificity. In conclusion, estimation of BRS by the Valsalva manoeuvre in post-myocardial infarction patients is limited by a large number of non-measurable results. When computable, measurements are well correlated with those obtained by Phe-BRS, but, because of large limits of agreement, the two methods cannot be used interchangeably. If used as a screening test for risk stratification, the Valsalva manoeuvre could reduce by about one-third the need for phenylephrine injection.

Adult↗
PubMed2000

Reproducibility of the six-minute walking test in chronic heart failure patients.

The six-minute walking test (WT) is used in trials and clinical practice as an easy tool to evaluate the functional capacity of chronic heart failure (CHF) patients. As WT measurements are highly variable both between and within individuals, this study aims at assessing the contribution of the different sources of variation and estimating the reproducibility of the test. A statistical model describing WT measurements as a function of fixed and random effects is proposed and its parameters estimated. We considered 202 stable CHF patients who performed two baseline WTs separated by a 30 minute rest; 49 of them repeated the two tests 3 months later (follow-up control). They had no changes in therapy or major clinical events. Another 31 subjects performed two baseline tests separated by 24 hours. Collected data were analysed using a mixed model methodology. There was no significant difference between measurements taken 30 minutes and 24 hours apart (p = 0.99). A trend effect of 17 (1.4) m (mean (SE)) was consistently found between duplicate tests (p < 0.001). REML estimates of variance components were: 5189 (674) for subject differences in the error-free value; 1280 (304) for subject differences in spontaneous clinical evolution between baseline and follow-up control, and 266 (23) for the within-subject error. Hence, the standard error of measurement was 16.3 m, namely 4 per cent of the average WT performance (403 m) in this sample. The intraclass correlation coefficient was 0.96. We conclude that WT measurements are characterized by good intrasubject reproducibility and excellent reliability. When follow-up studies > or = 3 months are performed, unpredictable changes in individual walking performance due to spontaneous clinical evolution are to be expected. Their clinical significance, however, is not known.

Adult↗
PubMed2000

Nonselective beta-adrenergic blocking agent, carvedilol, improves arterial baroflex gain and heart rate variability in patients with stable chronic heart failure.

OBJECTIVES: The purpose of this study was to investigate in a case-controlled study whether carvedilol increased baroreflex sensitivity and heart rate variability (HRV). BACKGROUND: In chronic heart failure (CHF), beta-adrenergic blockade improves symptoms and ventricular function and may favorably affect prognosis. Although beta-blockade therapy is supposed to decrease myocardial adrenergic activity, data on restoration of autonomic balance to the heart and, particularly, on vagal reflexes are limited. METHODS: Nineteen consecutive patients with moderate, stable CHF (age 54 +/- 7 years, New York Heart Association [NYHA] class II to III, left ventricular ejection fraction [LVEF] 24 +/- 6%), treated with optimized conventional medical therapy, received carvedilol treatment. Controls with CHF were selected from our database on the basis of the following matching criteria: age +/- 3 years, same NYHA class, LVEF +/- 3%, pulmonary wedge pressure +/- 3 mm Hg, peak volume of oxygen +/- 3 ml/kg/min, same therapy. All patients underwent analysis of baroreflex sensitivity (phenylephrine method) and of HRV (24-h Holter recording) at baseline and after six months. RESULTS: Beta-blockade therapy was associated with a significant improvement in symptoms (NYHA class 2.1 +/- 0.4 vs. 1.8 +/- 0.5, p < 0.01), systolic and diastolic function (LVEF 23 +/- 7 vs. 28 +/- 9%, p < 0.01; pulmonary wedge pressure 17 +/- 8 vs. 14 +/- 7 mm Hg, p < 0.05) and mitral regurgitation area (7.0 +/- 5.1 vs. 3.6 +/- 3.0 cm2, p < 0.01). No significant differences were observed in either clinical or hemodynamic indexes in control patients. Phenylephrine method increased significantly after carvedilol (from 3.7 +/- 3.4 to 7.1 +/- 4.9 ms/mm Hg, p < 0.01) as well as RR interval (from 791 +/- 113 to 894 +/- 110 ms, p < 0.001), 24-h standard deviation of normal RR interval and root mean square of successive differences (from 56 +/- 17 to 80 +/- 28 ms and from 12 +/- 7 to 18 +/- 9 ms, all p < 0.05), while all parameters remained unmodified in controls. During a mean follow-up of 19 +/- 8 months a reduced number of cardiac events (death plus heart transplantation, 58% vs. 31%) occurred in those patients receiving beta-blockade. CONCLUSIONS: Besides the well-known effects on ventricular function, treatment with carvedilol in CHF restores both autonomic balance and the ability to increase reflex vagal activity. This protective mechanism may contribute to the beneficial effect of beta-blockade treatment on prognosis in CHF.

Adrenergic beta-Antagonists↗
PubMed2000

Beta-blockade therapy in chronic heart failure: diastolic function and mitral regurgitation improvement by carvedilol.

BACKGROUND: In patients with chronic heart failure, the use of carvedilol therapy induces clinical and hemodynamic improvement. However, although the benefits of this beta-blocker have been established in patients with chronic heart failure, the mechanisms underlying them and the changes in left ventricular systolic function, diastolic function, and mitral regurgitation during long-term therapy remain unclear. OBJECTIVE: To identify the clinical and functional effects of carvedilol, focusing on diastolic function and mitral regurgitation variations. METHODS: Forty-five consecutive patients with chronic heart failure (ejection fraction 24% +/- 7%), 17 with dilated ischemic and 28 with nonischemic cardiomyopathy, were treated with carvedilol (mean dose 44 +/- 30 mg) and matched for clinical (New York Heart Association functional class and heart failure duration) and hemodynamic (cardiac index and pulmonary wedge pressure) characteristics to a control group. Clinical and echocardiographic variables were measured in the 2 groups at baseline and after 6 months and the results compared. RESULTS: After 6 months of treatment with carvedilol, left ventricular ejection fraction had increased from 24% +/- 7% to 29% +/- 9% (P <.0001); this change was caused by a reduction in end-systolic volume index (106 +/- 41 vs 93 +/- 37 mL/m(2); P <. 0001). Deceleration time of early diastolic filling increased (134 +/- 74 vs 196 +/- 63 ms; P <.0001). Seventeen of the 27 patients with demonstrated improvement of left ventricular diastolic filling moved from having a restrictive filling pattern to having a normal or pseudonormal left ventricular filling pattern. In the control group, no significant changes in deceleration time of early diastolic filling were found (139 +/- 74 vs 132 +/- 45 ms; P = not significant). The effective regurgitant orifice area decreased significantly in the carvedilol group but not in the control group. These changes were associated with a significant reduction of the mitral regurgitant stroke volume in the carvedilol group (50 +/- 25 vs 16 +/- 13 mL; P <.0001) but not in the control group (57 +/- 29 vs 47 +/- 24 mL; P = not significant). These changes of mitral regurgitation were closely associated with significant improvement of forward aortic stroke volume (r = -.57, P <.0001). These findings were not observed in patients in the control group. CONCLUSIONS: The results of this study show that long-term carvedilol therapy in patients with chronic heart failure was able to prevent or partially reverse progressive left ventricular dilatation. The effects on left ventricular remodeling were associated with a concomitant recovery of diastolic reserve and a decrease of mitral regurgitation, which have been demonstrated to be powerful prognostic predictors in such patients. Overall these findings provide important insights into the pathophysiologic mechanisms by which carvedilol improves the clinical course of patients with chronic heart failure.

Adrenergic beta-Antagonists↗