G.D. Pinna

Concomitant factors of decompensation in chronic heart failure.

The concomitant factors implicated in 328 nonfatal decompensations of 304 patients with congestive heart failure were: arrhythmias in 24%, infections in 23%, poor compliance in 15%, angina in 14%, iatrogenic factors in 10%, and other causes in 5% of cases. New York Heart Association class and right atrial pressure significantly related to the occurrence of decompensation. Poor compliance and angina were unpredictable, infection was related to pulmonary wedge pressure, iatrogenic factors were predicted by the more advanced functional classes, whereas arrhythmias were more frequent in patients with renal failure.

Doppler echocardiography reliably predicts pulmonary artery wedge pressure in patients with chronic heart failure with and without mitral regurgitation

OBJECTIVES This study was performed to assess whether the combination of multiple echocardiographic and Doppler variables can provide a reliable estimation of pulmonary artery wedge pressure in patients with chronic heart failure. BACKGROUND In patients with chronic heart failure a high pulmonary artery wedge pressure is associated with poor prognosis, more severe symptoms and low exercise tolerance. Several Doppler echocardiographic indexes have been shown to be related to pulmonary artery wedge pressure, but the dispersion of data has generally not allowed a quantitative assessment of this important variable. METHODS Simultaneous Doppler echocardiographic examinations and right heart catheterizations were performed in 231 patients with chronic heart failure due to dilated cardiomyopathy. Mitral and pulmonary venous flow velocity variables, left atrial volumes, mitral regurgitation jet area and left ventricular ejection fraction were correlated with pulmonary artery wedge pressure by both single and multilinear regression analysis. The reliability of the obtained multilinear equations was then tested in a separate group of 60 patients. RESULTS By univariate analysis, the deceleration rate of early diastolic mitral flow and the systolic fraction of pulmonary venous flow showed the strongest correlations (r=0.78 and =-0.76, respectively). Stepwise regression analysis led to two multilinear equations for predicting pulmonary artery wedge pressure in the whole population: the first included only two-dimensional echocardiographic and mitral flow velocity variables (r=0.84) and the second also included pulmonary venous flow variables (r=0.87). The highest correlation was obtained (r=0.89) by a third equation in the 73 patients without significant mitral regurgitation. Correlation coefficients between estimated and measured pulmonary artery wedge pressure were 0.91 (SEE=2.7 mm Hg) and 0.97 (SEE=1.8 mm Hg) when the first and the second equation, respectively, were applied to the testing group. CONCLUSIONS These results indicate that, in patients with chronic heart failure due to dilated cardiomyopathy, pulmonary artery wedge pressure can be reliably estimated even when mitral regurgitation is present by combining Doppler echocardiographic variables of mitral and pulmonary venous flow.

Can power spectral analysis of heart rate variability identify a high risk subgroup of congestive heart failure patients with excessive sympathetic activation? A pilot study before and after heart transplantation.

BACKGROUND AND OBJECTIVES--Autonomic dysfunction seems to be involved in the progression and prognosis of severe congestive heart failure. Parasympathetic activity can still be abnormal 4-8 weeks after haemodynamic improvement by heart transplantation. To identify patients in heart failure with a more pronounced neural derangement and to analyse the changes in sympathetic and parasympathetic activity soon after heart transplantation, spectral indices of heart rate variability were assessed in 30 patients in severe heart failure and in 13 patients after heart transplantation; a group of 15 age-matched subjects served as controls. METHODS AND RESULTS--Heart rate variability was assessed by standard electrocardiography (ECG) in patients in heart failure and by oesophageal ECG in patients after heart transplantation. Compared with controls, the mean RR interval and total power were reduced in heart failure. The 30 patients showed two different patterns of heart rate variability: in 14 no power was detected in the low frequency band (0.03-0.15 Hz) (LF) and total power was mainly concentrated in the high frequency band (0.15-0.45 Hz) (HF), whereas in the remaining 16 patients power in the LF band was increased and power in HF band was reduced compared with the controls. Patients with undetectable LF had a lower mean RR interval and total power (745(25) v 864(36) ms, p < 0.05; 118(16) v 902(202) ms2, p < 0.001), higher concentration of plasma noradrenaline (635(75) v 329(54) pg/ml, p < 0.05), and worse clinical status and prognosis (4 deaths v no deaths at 6 month follow up) than patients with a dominant LF band. In the post-transplant patients both the mean PP interval of the remnant atrium and total power resembled results in the patients with heart failure; in 7 of the 13 post-transplant patients no power was detectable in the LF band: when both HF and LF power were present the results resembled those in the 16 patients in heart failure. CONCLUSIONS--These data suggest that in more advanced stages of congestive heart failure, power spectral analysis of heart rate variability allows identification of a subgroup of patients with higher sympathetic activation and poorer clinical status who are at major risk of adverse events. In the short term after cardiac transplantation the spectral profile of the rhythm variability of the remnant atrium was not improved, suggesting that parasympathetic withdrawal and sympathetic hyperactivity persist, despite the restoration of ventricular function.

Application of time series spectral analysis theory: analysis of cardiovascular variability signals

The paper focuses on the most important application problems commonly encountered in spectral analysis of short-term (less than 10 min) recordings of cardiovascular variability signals (CVSs), critically analysing the different approaches to these problems presented in the literature and suggesting practical solutions based on sound theoretical and empirical considerations. The Blackman-Tukey (BT) and Burg methods have been selected as the most representative of classical and AR spectral estimators, respectively. For realistic simulations, ‘synthetic’ CVSs are generated as AR processes whose parameters are estimated on corresponding time series of normal, post-myocardial infarction and congestive heart failure subjects. The problem of resolution of spectral estimates is addressed, and an empirical method is proposed for model order selection in AR estimation. The issue of the understandability and interpretability of spectral shapes is discussed. The problem of non-stationarity and removing trends is dealt with. The important issue of identification and estimation of spectral components is discussed, and the main advantages and drawbacks of spectral decomposition algorithms are critically evaluated.

Doppler evaluations of left ventricular diastolic filling and pulmonary wedge pressure provide similar prognostic information in patients with systolic dysfunction after myocardial infarction.

Previous studies have demonstrated that in patients with various types of cardiac diseases and left ventricular dysfunction, left ventricular filling patterns assessed by Doppler of mitral flow are correlated to ventricular filling pressure, the prognostic value of which is well known. The current study was carried out to determine the prognostic importance of a noninvasive evaluation of left ventricular filling by Doppler of mitral flow in patients with systolic dysfunction after myocardial infarction and to compare its value with that of pulmonary wedge pressure. One hundred seven patients with a left ventricular ejection fraction < 40% were studied 3 to 12 weeks after myocardial infarction. All patients underwent a complete clinical examination, a standard two-dimensional and Doppler echocardiographic examination, and right-sided heart catheterization at rest and during a cardiopulmonary bicycle exercise test. Early and late diastolic peak flow velocities, their ratio, and the deceleration time of early diastolic velocity were measured from pulsed-wave Doppler of mitral flow. Follow-up data were obtained for 101 patients. During a mean period of 25 (median 21, range 12 to 60) months cardiac events (death, heart transplantation, or heart failure requiring hospitalization) occurred in 43 (42%) patients. Patients with cardiac events during follow-up were in a worse functional class and had a more impaired exercise capacity and higher capillary pulmonary wedge pressure at baseline examination. Among Doppler echocardiographic variables, in patients with cardiac events a greater early to late diastolic peak velocity ratio of mitral flow (1.9 +/- 0.9 pl/min vs 1.2 +/- 0.8 pl/min, p < 0.001) and a shorter early diastolic deceleration time (112 +/- 35 vs 145 +/- 42 msec, p < 0.001) were found. Cox analysis revealed that the combination of early to late diastolic peak flow velocity ratio of mitral flow and New York Heart Association functional class were the strongest noninvasive independent predictors of cardiac events. One-year event-free probability of survival was 90% in patients with an early to late diastolic peak velocity ratio < or = 1 (all but 1 in New York Heart Association functional class I or II) but was significantly less in patients with an early to late diastolic peak velocity ratio > 1 (64% in functional class I or II and 36% functional class III). Similar results were obtained when mean pulmonary wedge pressure was considered instead of the ratio between peak flow velocities of mitral flow.(ABSTRACT TRUNCATED AT 400 WORDS)

The accuracy of power-spectrum analysis of heart-rate variability from annotated RR lists generated by Holter systems

The accuracy of spectral analysis of heart-rate variability performed on annotated RR interval lists obtained from several commercial Holter systems was appraised. Five tape-recorder-based systems (Del Mar 750, Marquette 8000, Oxford Medilog Excel, Remco Cardioline AD 35 and Reynolds Pathfinder PA3) and four solid-state systems (Hewlett Packard 43420B, Marquette Seer, Oxford 6000FD2, Reynolds E-Ram) were considered. Two ECG signals with fixed real morphology but characterized by a different degree of modulation of the RR interval (reduced and normal variability) were fed into the recorders evaluated. The total power and the power in the very low-, low- and high-frequency bands were then estimated on all Holter-generated RR sequences. Spectral analysis was performed by both the autoregressive and fast-Fourier-transform methods. The estimation error of each parameter was statistically characterized and, for tape-recorder-based systems, inferential analysis was used to test for differences between recorders, tapes and times of recording. The centre and dispersion of the estimation error changed markedly from system to system. Some tape-recording systems showed large inter-recorder differences. The degree of spectral distortion was never uniform among selected bands. Solid-state systems performed better than tape-recording ones but both were limited in the accuracy by the quantization of RR interval measurement. The fast Fourier method yielded spectral estimates more stable than the autoregressive method. Our data clearly show that spectral analysis of very low-variability signals may be seriously affected by Holter recording and preprocessing of ECG signals.

Clinical value of baroreflex sensitivity

The arterial baroreflex is an important determinant of the neural regulation of the cardiovascular system. It has been recognised that baroreflex-mediated sympathoexcitation contributes to the development and progression of many cardiovascular disorders. Accordingly, the quantitative estimation of the arterial baroreceptor-heart rate reflex (baroreflex sensitivity, BRS), has been regarded as a synthetic index of neural regulation at the sinus atrial node. The evaluation of BRS has been shown to provide clinical and prognostic information in a variety of cardiovascular diseases, including myocardial infarction and heart failure that are reviewed in the present article.

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.

Prognostic value of Poincare/spl acute/ plot indexes in chronic heart failure patients

The identification of prognostic indexes in chronic heart failure (CHF) patients represents a challenging task in the analysis of heart rate variability (HRV) We thus assessed the prognostic value of novel computer-generated quantitative descriptors of Poincare/spl acute/ plots (PPlots) of HRV in a case-control study over 13 CHF patients who experienced cardiac death and 13 matched CHF controls. All subjects underwent Holter recording with computation of the standard deviation of normal-to-normal intervals (SDNN) and PPlot analysis. While visual classification of PPlots and SDNN did not significantly differentiate the controls from the deceased patients, a highly significant association with outcome was found for quantitative PPlot indexes. This preliminary study shows that automatic quantification of PPlots allows a better discrimination between patients at risk of cardiac events and controls than does a visual classification of plot features and time-domain HRV.

Non-invasive baroreflex sensitivity assessment using wavelet transfer function-based time–frequency analysis

A novel approach for the estimation of baroreflex sensitivity (BRS) is introduced based on time-frequency analysis of the transfer function (TF). The TF method (TF-BRS) is a well-established non-invasive technique which assumes stationarity. This condition is difficult to meet, especially in cardiac patients. In this study, the classical TF was replaced with a wavelet transfer function (WTF) and the classical coherence was replaced with wavelet transform coherence (WTC), adding the time domain as an additional degree of freedom with dynamic error estimation. Error analysis and comparison between WTF-BRS and TF-BRS were performed using simulated signals with known transfer function and added noise. Similar comparisons were performed for ECG and blood pressure signals, in the supine position, of 19 normal subjects, 44 patients with a history of previous myocardial infarction (MI) and 45 patients with chronic heart failure. This yielded an excellent linear association (R > 0.94, p < 0.001) for time-averaged WTF-BRS, validating the new method as consistent with a known method. The additional advantage of dynamic analysis of coherence and TF estimates was illustrated in two physiological examples of supine rest and change of posture showing the evolution of BRS synchronized with its error estimations and sympathovagal balance.