Biomedical subjects

R Maestri

Publications and source records attributed to R Maestri.

At least 55 records · Page 3Linked to original sources

PubMed1997

Dobutamine and nitroprusside infusion in patients with severe congestive heart failure: hemodynamic improvement by discordant effects on mitral regurgitation, left atrial function, and ventricular function.

OBJECTIVES: In patients with severe heart failure additional therapeutic support with intravenous inotropic or vasodilator drugs is frequently used in the attempt to obtain hemodynamic control. The nature and extent to which diastolic filling, atrial function, and mitral regurgitation are modified by these drugs have not been fully explored. The aim of this study was to compare the acute adaptations of the left ventricular performance, left atrial function, and mitral regurgitation that accompanied hemodynamic improvement during intravenous dobutamine and nitroprusside infusions in patients with severe chronic heart failure. METHODS: Forty consecutive patients with severe heart failure were evaluated by simultaneous echo-Doppler and hemodynamic investigations at baseline and during nitroprusside and dobutamine administration. Mitral flow velocity variables, left atrial and ventricular volumes, left atrial reservoir, conduit and pump volumes, and mitral regurgitation jet area were compared by analysis of variance for repeated measurements. RESULTS: Nitroprusside increased cardiac output (2.1 +/- .5 vs 2.6 +/- .5 L/min/m2, p < 0.004), reduced left ventricular filling pressure (25 +/- 6 vs 14 +/- 4 mm Hg, p < 0.0001), and improved left atrial pump volume (19 +/- 3 vs 26 +/- 12 ml, p < 0.02) without variations in left atrial reservoir and conduit volume. The restoration of preload reserve and improvement of the atrial contribution to left ventricular diastolic filling were demonstrated by the Doppler mitral flow pattern, which moved from a restrictive to a normal pattern. Furthermore mitral regurgitation decreased in all patients (9 +/- 4.6 vs 4.6 +/- 3.4 cm2, p < 0.0001). Dobutamine increased cardiac output (2.1 +/- .5 vs 2.8 +/- .6 L/min/m2), but the effects on pulmonary wedge pressure and mitral regurgitation were variable and unpredictable. Left atrial reservoir and conduit volumes increased, whereas left atrial pump volume did not change (19 +/- 13 vs 22 +/- 14 ml, p = NS). Furthermore Doppler mitral flow showed a persistent restrictive pattern. CONCLUSIONS: In patients with advanced congestive heart failure both nitroprusside and dobutamine improve cardiac output, with different adaptations of left ventricular performance and left atrial function. Nitroprusside seems to restore both atrial and ventricular pump function better. Careful echo-Doppler monitoring during drug infusion provides information relevant to the clinical treatment of individual patients.

Atrial Function, Left↗

PubMed1997

Depressed arterial baroreflex sensitivity and not reduced heart rate variability identifies patients with chronic heart failure and nonsustained ventricular tachycardia: the effect of high ventricular filling pressure.

In chronic heart failure (CHF) the contributing role of increased sympathetic activity and hemodynamic dysfunction in the genesis of ventricular arrhythmias has not been well established. To assess the relation between severe ventricular arrhythmias, hemodynamic impairment, and autonomic nervous system derangement, 142 patients with CHF in sinus rhythm underwent 24-hour electrocardiographic recording, right-sided heart catheterization, and evaluation of sympathovagal balance by heart rate variability (HRV) and baroreflex sensitivity (BRS). Patients were grouped according to the absence (without nonsustained ventricular tachycardia [NSVT]; n = 87) or presence (with NSVT; n = 55) of NSVT. Patients with NSVT had higher pulmonary artery and capillary pressures and more pronounced signs of sympathetic activation and parasympathetic withdrawal compared with those without NSVT. However, logistic regression analysis revealed that depressed BRS but not reduced HRV was significantly associated with the presence of NSVT, at both univariate analysis and after adjustment for clinical and hemodynamic variables. Moreover, it was found that when depressed BRS was associated with high pulmonary capillary pressure, the odds ratio for having NSVT rose markedly from 3.8 to 6.5. In conclusion, this study indicates that in stable CHF the assessment of arterial baroreflex function, but not HRV analysis, allows identification of patients at high risk of NSVT. It is suggested that the effect of depressed BRS is strengthened by the simultaneous presence of increased myocardial wall stress. These data support the hypothesis of a contributory role of autonomic nervous system dysfunction as expressed by the inability to activate effective vagal reflexes and an indirect index of ventricular stretch in the genesis of life-threatening arrhythmias.

Autonomic Nervous System↗

PubMed1997

Reliability of a hand gripping endurance test.

The aim of this study was to assess the reproducibility of a new endurance test for hand grip movements. On six occasions separated by at least 3 days, 30 healthy subjects performed six maximal endurance tests in two different positions with a hand grip tool attached to an isokinetic dynamometer. The test consisted of repeated maximal grip movements (1-min bouts for men and 30-s bouts for women subjects) at an angular velocity of 45 degrees/s. A custom-made PC programme was used to collect data on peak torque and mechanical work, and to provide the following parameters: basal torque, basal work, time until basal values fell to 20, 30 and 50% of the initial peak values, slopes of decay of torque and work over time. The intraclass correlation coefficient (ICCC) was then computed to assess the reproducibility of the parameters obtained during the tests. An 'almost perfect' (0.8 < ICCC = 1) reproducibility of the basal torque values in both positions and a 'substantial' (0.6 < ICCC = 0.8) or 'almost perfect' reproducibility of the slope values referred to the torque decay over time was observed. Feasible applications of this new endurance test in ergonomics and vocational rehabilitation are discussed.

Adult↗

PubMed1997

Influence of residual ischaemia on heart rate variability after myocardial infarction.

Despite the growing evidence for the positive predictive value of depressed baroreflex sensitivity and/or reduced heart rate variability after myocardial infarction, the mechanisms involved in these autonomic alterations are not fully understood. Specifically, the possible influence of residual ischaemia has not been assessed. To address this problem we studied the spectral analysis of heart rate variability in 21 patients with a first myocardial infarction in whom the only clinical correlate was the presence of residual ischaemia, as documented by the positive response to both an exercise stress test and an echocardiographic stress test. Data from these patients were compared with those obtained in a group of postmyocardial infarction patients similar for several risk factors, age, site of myocardial infarction, but without residual ischaemia. Patients positive for residual ischaemia had lower power in the whole spectrum (1146 +/- 158 vs 1631 +/- 159 ms2, P = 0.032) as well as in the low and high frequency bands of heart rate variability. A nocturnal increase in high frequency was observed in those without residual ischaemia (from 167 +/- 35 to 242 +/- 51 ms2, +45%, P = 0.034), but not in those with residual ischaemia (from 111 +/- 19 to 141 +/- 29 ms2, +27%, ns). Thus, residual ischaemia reduces heart rate variability after myocardial infarction. The autonomic effects of residual ischaemia probably contribute to its negative prognostic value after myocardial infarction.

Adult↗

PubMed1997

POLYAN: a package for a polyparametric approach to cardio-respiratory variability signals analysis.

POLYAN, a computer program based on a point-and-click graphical user interface for easy and efficient polyparametric analysis of cardio-respiratory variability signals is described. The main tasks performed by the package are: univariate and bivariate spectral analysis on selected portions of the signals with the computation of some clinically relevant indices and baroreflex sensitivity assessment by the analysis of the relationship between systolic pressure and heart period signals. Some tools which help the analyst in the solution of common practical problems have been implemented to make analysis easier and more rigorous. Using Matlab language, POLYAN has the flexibility and expandability necessary for a research tool, which often requires implementation of new algorithms and computation of new parameters.

Computer Graphics↗

PubMed1997

The Failing Heart.

Heart failure is a highly lethal condition which carries a shorter life expectancy than most common malignancies. Despite the large number of efforts dedicated to understand why the heart fails, only limited possibilities are available to improve survival. This because the problem is very complex and is dependent upon multiple changes in the anatomical and functional properties of the heart as well as of other organs, together with modifications in systemic and local hormonal and neuronal interactions. This review has been focused on some results obtained in pathologic hearts explanted from subjects with intractable heart failure or in hearts from animals with spontaneous or induced myocardial damage with different degrees of cardiac dysfunction and failure performed in the last few years in our laboratories. Hearts in failure have different alterations at the anatomical, histological and cellular level that may justify, at least in part, the functional impairment and the progressive evolution of the disease. Recent findings of apoptotic myocyte cell death and myocytic hyperplasia are exciting prospectives to be followed with the expectation that new strategies may be discovered to alter the unfavourable outcome of heart failure. However, the complexity of the problem seems to require a large number of efforts before the results obtained can be applied to human beings. Thus, basic researches must be stimulated to explore the mechanisms which allow the development of heart failure despite the persistence in the damaged myocardium of a large number of contractile cells.

Journal Article↗

PubMed1996

Aging, cardiac hypertrophy and ischemic cardiomyopathy do not affect the proportion of mononucleated and multinucleated myocytes in the human heart.

The current investigation was designed to evaluate whether the proportion of mononucleated binucleated, trinucleated and tetranucleated myocytes varies in the left ventricle, interventricular septum and right ventricular free wall with aging, cardiac hypertrophy and ischemic cardiomyopathy. In addition, the number and dimensional properties of myocytes were measured to determine whether a relationship existed between myocyte size and number, and organ hypertrophy. For this purpose, 72 normal hearts were obtained from individuals who died from causes other than cardiovascular disease and compared with 81 hypertrophied hearts and 95 with ischemic cardiomyopathy. The age interval examined varied from 26 to 93 years. The analysis of enzymatically dissociated myocytes in control left ventricles demonstrated that mononucleated, binucleated, trinucleated, trinucleated and tetranucleated myocytes comprised 74%, 25.5%, 0.4% and 0.1% of the entire myocyte population. Similarly, mononucleated myocytes constituted the prevailing cell population of the interventricular septum and right ventricular free wall. Aging, myocardial hypertrophy and ischemic cardiomyopathy did not change the percentage of mononucleated and multinucleated myocyte in the ventricular myocardium. Cardiac hypertrophy and ischemic cardiomyopathy were characterized by comparable increase in myocyte size in spite of a significant difference in the magnitude of myocardial hypertrophy. Myocyte number was increased in hypertrophied hearts, whereas myocyte cell loss occurred in ischemic cardiomyopathy. In conclusion, aging, cardiac hypertrophy and ischemic cardiomyopathy do not alter the fractions of mononucleated and multinucleated myocytes in the myocardium.

Adult↗

PubMed1996

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.

Heart Diseases↗

PubMed1996

Accuracy of telemetry signals in the post-implantation monitoring of electrograms sensed by pacemakers.

Monitoring of electrograms (EGMs) sensed by pacemakers (PMs) during their lifetime is the utmost importance, since changes of these signals, due to modifications of the electrode-myocardial interface may occur compromising the proper functioning of the PM. Since after implantation these intracardiac signals are accessible only by means of a telemetry system, it is necessary to ascertain how faithfully the telemetric signals reproduce the direct ones. To this aim we devised an accurate method, based on linear system theory, which allows the estimation of the transfer function of the PM-telemetry system and the comparison of a set of time and frequency domain parameters (wave amplitude, slew rate, frequency at the spectrum peak and bandwidth) computed on both direct and telemetric signals. To overcome the problem that these two signals cannot be recorded simultaneously, an appropriate model of the input and output signals of the PM-telemetry system and of their interrelationship was identified. This model relies on a set of reasonable assumptions about the nature of the direct signal (supposed to have a fixed morphology within a predefined analysis window) and of noise sources corrupting both the direct and telemetric signals. Owing to the involvement of deterministic and stochastic signals, the theory of quasi-stationary signals was employed to obtain the system transfer function. To test our method, direct and telemetric recordings were performed on 12 patients with atrial sensing carrying Medtronic Pacemakers (Mod Elite 7077/7086, programmer Mod 9760) with unipolar steroid eluting leads (Medtronic Capsure 4523). The results we obtained demonstrate that the specific system considered acts as a low-pass filter with a -3 dB frequency at about 90 Hz this ensures that the telemetric signal contains almost all the information of the direct one and can be used to monitor the changes of the signals sensed by the PM.

Aged↗

PubMed1996

Alterations of breathing in chronic heart failure: clinical relevance of arterial oxygen saturation instability.

1. In patients with chronic heart failure (CHF) alterations of breathing such as Cheyne-Stokes respiration (CSR) or periodic breathing, (PB) have been frequently described during both day- and night-time. These respiratory rhythm disorders are associated with marked oscillations of arterial oxygen saturation (SaO2) which may expose the patients to prolonged hypoxia. 2. In 40 stable CHF patients and 8 controls during awake day-time, we studied the relationship between alterations of breathing and SaO2, to verify the effect of voluntary control of respiration or oxygen therapy on the instability of SaO2 (analyzed as standard deviation (SD) of the mean value). Simultaneous recordings of ECG, lung volumes and SaO2 were made during 10 min. resting and 4 min. controlled breathing In a subgroup of 5 CHF the effect of oxygen therapy was compared to that of controlled breathing. 3. It was found that 62% of CHF had CSR or PB. Mean SaO2 and SD of SaO2 were significantly different in CHF as compared to controls (respectively 92.4 +/- 2.5 vs 95.4 +/- 0.5%, p < 0.002 and (1.27 +/- 0.9 vs 0.28 +/- 0.13%, p < 0.01), but among CHF pts those with CSR and PB had a lower SaO2 and a more pronounced instability of SaO2. Controlled breathing eliminated apneas and reduced or abolished the variation of tidal volume. In both control and CHF it resulted in an increase of mean SaO2 while a significant reduction of SaO2 instability was observed only in CHF, particularly if CSR or PB were present. Voluntary control of respiration was similar to oxygen therapy in increasing SaO2, but more effective on SaO2 SD. 4. It is concluded that in stable CHF, resting SaO2 is reduced and showed a marked instability particularly when periodic alterations of breathing were present. Continuous beat-to-beat recording of SaO2 may detect patients who have PB or CSR. Training to produce more regular breathing, regardless of the amount of ventilation, may represent a useful intervention.

Adult↗

PubMed1996

An oscillation of the respiratory control system accounts for most of the heart period variability of chronic heart failure patients.

A periodic breathing (PB) pattern is often observed in chronic heart failure (CHF) patients (pts). In order to clarify the role of this abnormal respiratory activity upon heart period variability we investigated, in a group of 20 stable CHF pts (NYHA class II to III, median EF 24%) showing a PB pattern, 1) whether observed data were consistent with the instability hypothesis of PB and 2) the relationship between oscillations of heart period and the contemporary fluctuations of ventilatory and chemoreceptor activity. Univariate and bivariate spectral analysis were performed on short-term resting recordings of instantaneous lung volume (ILV), instantaneous minute ventilation (IMV), heart period (HP) and arterial O2 saturation at the ear (SpO2). A very low frequency (VLF) oscillation around 0.02 Hz, associated with PB, was observed in all signals and contributed to 75% (23 divided by .99) (median (range)) of the HP variability. The coherence between ILV and HP was 0.77 (0.3 divided by 0.95) and between SpO2 and HP 0.8 (0.4 divided by 0.98. A high coherence was also found between IMV and SpO2: 0.9 (0.6 divided by 0.98). The median phase lag between IMB and SpO2 was -211 degrees (-240 divided by -156), between ILV and HP -205 degrees (-260 divided by -180) and between SpO2 and HP 0 degree (-26 divided by 30). The estimated lung-to-ear circulation time was 24.5 s (12.5 divided by 36.5). This study definitely confirms that during PB a common rhythm is shared between the respiratory and cardiovascular regulatory system Taking into account the error introduced by the measuring process, our results, are consistent with the hypothesis that periodic breathing of CHF pts originates from an instability of the feedback control system of ventilation. Hence most of the HP variability of these pts simply reflects abnormal pattern of respiratory activity.

Adult↗

PubMed1996

Estimation of arterial blood pressure variability by spectral analysis: comparison between Finapres and invasive measurements.

In order to assess the accuracy of spectral analysis of beat-by-beat arterial blood pressure fluctuations recorded by the finger technique we analysed simultaneous ipsilateral resting sequences (180 s) of systolic blood pressure (SP) and diastolic blood pressure (DP) obtained by brachial artery cannulation and by the Finapres device in 26 post-myocardial infarction (post-MI) and 24 chronic heart failure (CHF) patients. We estimated: (i) the total variability and the power in the bands 0.01-0.04 Hz (band 1), 0.04-0.07 Hz (band I), 0.07-0.15 Hz (band III) and 0.15-0.45 Hz (band IV); and (ii) the group-average transfer function between the invasive and non-invasive channel. The total variability of intra-arterial SP was greatly enhanced by the Finapres device in both populations (p < 0.01) mainly due to the increase of power in bands I and II (mean percentage errors 157 and 111% in post-MI and 368 and 245% in CHF patients respectively). The power in band IV was significantly reduced in post-MI (p < 0.001) but not in CHF patients. The total DP variability increased in post-MI patients (p < 0.001) due to the increase in bands I and II (mean percentage errors 62 and 43% respectively). No significant difference was found in bands III and IV of the same group and in the overall variability of CHF. Linear system analysis showed that intra-arterial SP oscillations in both groups are amplified by the Finapres device in bands I and II, with a higher gain in CHF patients, whereas they are attenuated in band IV. Band III acts as a transition band. DP oscillations recorded non-invasively are slightly amplified in bands I and II of post-MI patients only and are attenuated in band IV of both groups. A substantial fraction (approximately 30%) of the non-invasive SP variability in band I cannot be explained as a pure linear transformation (amplification) of the invasive signal. A phase delay in the range 7 degrees-10 degrees relates the non-invasive signal to the invasive one in the region 0.025-0.17 Hz and approaches zero elsewhere. Several mechanisms were examined as potential causes of the invasive-non-invasive differences. We argue that these differences are mainly due to the complex rhythmic behaviour of peripheral resistance vessels.

Adult↗

PubMed1996

Effects of record length selection on the accuracy of spectral estimates of heart rate variability: a simulation study.

To evaluate the effects of record length selection on the accuracy of spectral estimates of heart rate variability (HRV), a simulation study was carried out using a set of 58 signals obtained by autoregressive (AR) fitting a representative sample of real HRV signals. Four record lengths of 180, 300, 420, and 540 s were considered. Spectral estimation was performed by both the Blackman-Tukey (B-T) and AR methods. Accuracy was assessed for: 1) point spectral estimates, by computing the normalized averaged bias (NAB) and variance (NAV); and 2) the most commonly used spectral parameters [total power (TP) and the powers in the bands: very low frequency (VLF) (0 divided by 0.04 Hz), low frequency (LF) (0.04 divided by 0.15 Hz), and high frequency (HF) (0.15 divided by 0.45 Hz)], by computing the normalized bias (NB) and variance (NV). The results are: whatever the record length considered, the 90th percentiles (90P) of the NAB were < 10%, whereas those of the NB were < 9% for TP, LF, and HF powers, and < 14% for the VLF power, in both methods. The NAV was proportional to the reciprocal of record length, showing high 90P values for the shortest record length (26.4% for B-T and 44.2% for AR). The NV showed the same trend but 90P values were much lower (< 8% for TP, LF, and HF powers and < 19% for VLF power, in both methods). In the final part of the paper a procedure for the computation of approximate upper bounds of the relative absolute error of spectral measures at each record length, based on the knowledge of the NB and NV, is presented.

Algorithms↗

PubMed1996

[Pulmonary venous flow in patients with chronic heart failure: feasibility and additional value compared to transmitral flow for non-invasive estimation of pulmonary wedge pressure].

BACKGROUND: In many cardiac conditions, Doppler of transmitral flow has been showed to be related to left ventricular filling pressure, but several factors may limit its practical value in estimating pulmonary wedge pressure in patients with chronic heart failure. Pulmonary venous velocities directly depend on the oscillations of left atrial pressure. Recent studies suggest that transthoracic Doppler of pulmonary venous flow provides a more accurate estimation of pulmonary wedge pressure. However the relative values of transmitral and pulmonary venous flow for assessing pulmonary wedge pressure in patients with chronic heart failure have not been fully classified until now. Accordingly, we performed this study to assess the feasibility of transthoracic Doppler of pulmonary venous flow in patients with chronic heart failure and to evaluate whether it provides additional information regarding pulmonary wedge pressure when compared with Doppler indices of transmitral flow. METHODS: Simultaneous Doppler echocardiographic examinations and right heart catheterizations were performed prospectively in 300 consecutive patients with chronic heart failure due to dilated cardiomyopathy. The correlations of mitral and pulmonary venous flow velocity variables, left atrial volumes, mitral regurgitation jet area and left ventricular ejection fraction with pulmonary artery wedge pressure were evaluated. RESULTS: A complete recording of transthoracic pulmonary venous flow including all components was obtained in 66% of patients, while only systolic and diastolic forward flow were recorded in 88% of patients. Several indices, derived from pulmonary venous flow, were correlated with pulmonary wedge pressure; the strongest correlation was between systolic fraction of peak velocities and pulmonary wedge pressure (r = -0.76). This value was similar to that obtained between deceleration rate (r = 0.78) and deceleration time (r = -0.67) of transmitral flow and pulmonary wedge pressure. A systolic fraction > 40% showed a greater positive predictive value than restrictive pattern of transmitral flow for identifying patients with pulmonary wedge pressure > 18 mmHg (95% vs 86% p < 0.05). This accuracy is confirmed also in patients who had a single peak of transmitral flow. CONCLUSIONS: Doppler of pulmonary venous flow can be performed in a high percentage of patients with chronic heart failure due to dilated cardiomyopathy. The indices derived from transthoracic pulmonary venous flow are strongly correlated with pulmonary wedge pressure and improve the noninvasive identification of patients with high pulmonary wedge pressure, even when transmitral flow pattern is difficult to be interpreted.

Aged↗

PubMed1995

Physiology and pathophysiology of heart rate and blood pressure variability in humans: is power spectral analysis largely an index of baroreflex gain?

1. It is often assumed that the power in the low- (around 0.10 Hz) and high-frequency (around 0.25 Hz) bands obtained by power spectral analysis of cardiovascular variables reflects sympathetic and vagal tone [corrected] respectively. An alternative model attributes the low-frequency band to a resonance in the control system that is produced by the inefficiently slow time constant of the reflex response to beat-to-beat changes in blood pressure effected by the sympathetic (with or without the parasympathetic) arm(s) of the baroreflex (De Boer model). 2. We have applied the De Boer model of circulatory variability to patients with varying baroreflex sensitivity to patients with varying baroreflex sensitivity and one normal subject, and have shown that the main differences in spectral power (for both low and high frequency) between and within subjects are caused by changes in the arterial baroreflex gain, particularly for vagal control of heart rate (R-R interval) and left ventricular stroke output. We have computed the power spectrum at rest and during neck suction (to stimulate carotid baroreceptors). We stimulated the baroreceptors at two frequencies (0.1 and 0.2 Hz), which were both distinct from the controlled respiration rate (0.25 Hz), in both normal subjects and heart failure patients with either sensitive or poor baroreflex control. 3. The data broadly confirm the De Boer model. The low-frequency (0.1 Hz) peak in either R-R or blood pressure variability) was spontaneously generated only if the baroreflex control of the autonomic outflow was relatively intact.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Cellular basis of ventricular remodeling after myocardial infarction in rats.

The remodeling of the spared non-ischemic left ventricular myocardium after different time intervals from the occlusion of the left coronary artery was examined in rats. In the presence of large infarcts, ventricular failure developed two to three days after surgery, because of chamber dilation and thinning of the wall, resulting in an average 7.5-fold increase in diastolic stress on the surviving myocardium. Mural thinning of the ventricular wall remote from and bordering the infarction occurred through side-to-side slippage of myocytes and capillaries within the wall. Although an average hypertrophic growth of 22% of the spared myocytes has been found, this amount of hypertrophy was insufficient to restore normal myocardial function. Long-term cardiac restructuring after infarction was characterized by the persistence of chamber dilatation and thinning of the ventricular wall. In addition to the side-to-side slippage, lengthening of the myocytes was an important cause of ventricular changes. As the reactive hypertrophy of the unaffected ventricle was insufficient to re-establish the ratio of ventricular mass to chamber volume, the diastolic stress remained elevated and decompensated eccentric ventricular hypertrophy developed. The anatomical remodeling of the spared left ventricular myocardium is an important conditioning factor in the short- and long-term outcome of ischemic cardiomyopathy.

Animals↗

PubMed1994

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.

Electrocardiography↗

PubMed1994

Scopolamine improves autonomic balance in advanced congestive heart failure.

BACKGROUND: Sympathetic hyperactivity and parasympathetic withdrawal in patients with congestive heart failure correlate closely with disease severity and overall survival. The modulating effects of drugs on the autonomic dysfunction may contribute to improve survival. Low-dose scopolamine has a vagomimetic effect in normal subjects and patients after acute myocardial infarction. We assessed whether transdermal scopolamine would increase vagal activity in patients with congestive heart failure. METHODS AND RESULTS: Heart rate variability was assessed at baseline, 24 hours after one patch of transdermal scopolamine, and 48 hours after scopolamine withdrawal in 21 patients with moderate to severe heart failure. Scopolamine increased both time- and frequency-domain parameters of heart rate variability. Specifically, the mean RR interval and its SD increased by 5.5% (P < .001) and 45% (P < .001), respectively. The change remained significant when corrected for mean heart rate with a 39% (P < .01) increase of the coefficient of variation. The absolute power of the high-frequency component was also significantly augmented. All the parameters returned to baseline after scopolamine withdrawal. Individual analysis showed that in the 7 patients in whom scopolamine did not increase mean RR interval, heart rate variability did not change. CONCLUSIONS: Transdermal scopolamine increases vagal activity as assessed by heart rate variability in patients with congestive heart failure. This autonomic modulation does not occur in all patients and can be predicted by RR interval changes. Whether such restoration of the autonomic balance might have beneficial effects in the long-term management of patients with congestive heart failure remains to be determined.

Administration, Cutaneous↗