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Maria Teresa La Rovere

Publications and source records attributed to Maria Teresa La Rovere.

At least 19 recordsLinked to original sources
PubMed2006

Clinical correlates of non-linear indices of heart rate variability in chronic heart failure patients.

We assessed the clinical correlates of a comprehensive set of non-linear heart rate variability (HRV) indices computed from 24-h Holter recordings for 200 stable chronic heart failure (CHF) patients [median age (lower quartile, upper quartile) 54 (47, 58) years, LVEF 23% (19%, 28%)]. A total of 19 non-linear indices belonging to six major families, namely symbolic dynamics, entropy, empirical mode decomposition, fractality-multifractality, unpredictability and Poincaré plots, were considered. Most indices showed a significant association with ejection fraction and with the severity of symptoms, while only two (one each from the fractality and Poincaré plot families) showed an association with aetiology. Only one symbolic dynamics variable was associated with the presence of non-sustained ventricular tachycardia and two symbolic dynamics variables were associated with the rate of ventricular ectopic events. Our results demonstrate the existence of selective links between non-linear indexes of HRV and the clinical status and functional impairment of CHF patients. This indicates that further studies should be designed to investigate the physiopathological mechanisms involved in such links.

Arrhythmias, Cardiac↗
PubMed2005

Cardiac resynchronization therapy improves heart rate profile and heart rate variability of patients with moderate to severe heart failure.

OBJECTIVES: This study sought to report long-term changes of cardiac autonomic control by continuous, device-based monitoring of the standard deviation of the averages of intrinsic intervals in the 288 five-min segments of a day (SDANN) and of heart rate (HR) profile in heart failure (HF) patients treated with cardiac resynchronization therapy (CRT). BACKGROUND: Data on long-term changes of time-domain parameters of heart rate variability (HRV) and of HR in highly symptomatic HF patients treated with CRT are lacking. METHODS: Stored data were retrieved for 113 HF patients (New York Heart Association functional class III to IV, left ventricular ejection fraction < or =35%, QRS >120 ms) receiving a CRT device capable of continuous assessment of HRV and HR profile. RESULTS: The CRT induced a reduction of minimum HR (from 63 +/- 9 beats/min to 58 +/- 7 beats/min, p < 0.001) and mean HR (from 76 +/- 10 beats/min to 72 +/- 8 beats/min, p < 0.01) and an increase of SDANN (from 69 +/- 23 ms to 93 +/- 27 ms, p < 0.001) at three-month follow-up, which were consistent with improvement of functional capacity and structural changes. Different kinetics were observed among these parameters. The SDANN reached the plateau before minimum HR, and mean HR was the slowest parameter to change. Suboptimal left ventricular lead position was associated with no significant functional and structural improvement as well as no change or even worsening of HRV. The two-year event-free survival rate was significantly lower (62% vs. 94%, p < 0.005) in patients without any SDANN change (Delta change < or =0%) compared with patients who showed an increase in SDANN (Delta change >0%) four weeks after CRT initiation. CONCLUSIONS: Cardiac resynchronization therapy is able to significantly modify the sympathetic-parasympathetic interaction to the heart, as defined by HR profile and HRV. Lack of HRV improvement four weeks after CRT identifies patients at higher risk for major cardiovascular events.

Female↗
PubMed2005

Applicability and clinical relevance of the transfer function method in the assessment of baroreflex sensitivity in heart failure patients.

OBJECTIVES: We sought to assess applicability, clinical correlates, and prognostic value of the transfer function method for measuring baroreflex sensitivity (TF-BRS). BACKGROUND: Abnormalities in autonomic reflexes play an important role in the development and progression of chronic heart failure (CHF). Simple and non-invasive techniques for clinical measurement of such reflexes are desirable. METHODS: In 317 stable CHF patients in sinus rhythm (median age [interquartile range]: 54 years [48 to 59 years], New York Heart Association [NYHA] functional class II to III: 88%, left ventricular ejection fraction [LVEF]: 27% [22% to 33%]) we recorded electrocardiograms and non-invasive arterial pressure during paced breathing to measure TF-BRS. RESULTS: Owing to a high number of ectopic beats, TF-BRS could be computed in 72% of the patients; TF-BRS was lower in NYHA functional class III to IV and mitral regurgitation 2 to 3 (p < 0.0005 for both). Correlation with LVEF and standard deviation of all normal-to-normal intervals was 0.18 and 0.31 (p < 0.001 for both). During a mean follow-up of 26 months, 23% of the patients experienced a cardiac event. A depressed TF-BRS (< or =3.1 ms/mm Hg) was significantly associated with the outcome (hazard ratio 3.2, 95% confidence interval [CI] 1.7 to 6.0, p = 0.0003). Patients with a missing TF-BRS had a high event rate (36%). Combining this information with available TF-BRS measurements, a new prognostic index could be computed in 97% of the patients that significantly predicted the outcome after adjustment for clinical and functional variables (hazard ratio 2.5, 95% CI 1.3 to 4.6 p = 0.004). CONCLUSIONS: In CHF patients in sinus rhythm, TF-BRS conveys relevant clinical and prognostic information, but its measurability is markedly affected by ectopic activity. Nevertheless, a TF-BRS-based risk index carrying significant and independent prognostic information can be computed in almost all patients.

Baroreflex↗
PubMed2005

Echo-Doppler and clinical evaluations to define hemodynamic profile in patients with chronic heart failure: accuracy and influence on therapeutic management.

BACKGROUND: Correct classification of chronic heart failure (CHF) patients by dual evidence of congestion and adequate perfusion is the primary clinical focus for management. OBJECTIVES: To evaluate the accuracy of echo-Doppler compared with clinical evaluation in determining the hemodynamic profile of patients with CHF; and to compare therapeutic changes based on hemodynamic or echo-Doppler findings. METHODS: Three hundred and sixty-six consecutive CHF patients (ejection fraction 25+/-7%) in sinus rhythm, undergoing evaluation for cardiac transplantation, underwent physical examination prior to right heart catheterization and echo-Doppler studies. Subsequently, patients were randomized to therapeutic optimization using either right heart catheterization or echo-Doppler data. The end-points were: identification of low cardiac output (cardiac index <2.2 l/min/m(2)); high pulmonary wedge pressure (PWP >18 mm Hg); high right atrial pressure (RAP >5 mm Hg) and analysis of therapeutic changes made in response to the right heart catheterization and echo-Doppler studies. RESULTS: Echo-Doppler showed better accuracy in estimating abnormal hemodynamic indices than clinical variables (cardiac index <2.2 l/min/m(2): echo positive predictive accuracy (PPA) 98% vs. clinical PPA 52% p<0.00001; PWP >18 mm Hg: echo PPA 85% vs. clinical PPA 76% p=0.0011; RAP >5 mm Hg: echo PPA 82% vs. clinical PPA 57% p<0.00001). When applied to individual patients, the echo-Doppler assessment was more accurate than clinical evaluation in defining the different hemodynamic profiles: wet/cold (89% vs. 13%, p<0.0001); wet/warm (73% vs. 30%, p<0.0001); dry/cold (68% vs. 12%, p<0.0001); dry/warm (88% vs. 51%, p<0.0001). Therapeutic decision-making based on echo-Doppler findings was similar to that based on hemodynamics. CONCLUSION: Echo-Doppler hemodynamic monitoring proved accurate in estimating hemodynamic profiles and influenced therapeutic management.

Adrenergic beta-Antagonists↗
PubMed2005

Cardiovagal response to acute mild exercise in young healthy subjects.

BACKGROUND: The aim of the present study was to investigate the effect of a single bout of mild exercise on autonomic nervous system activity in healthy subjects. METHODS AND RESULTS: The study group comprised 18 healthy males, aged between 20 and 24 years, who had not been training regularly for the last 3 months. A supine recording of systolic arterial pressure (SAP) and RR interval and the administration of the phenylephrine test were performed at baseline and repeated after a 60-min recovery period following treadmill exercise training for 30 min at 65% of maximal heart rate. Mean SAP and RR interval, heart rate variability (HRV) indices (the standard deviation of normal-to-normal RR intervals (SDNN), the square root of the mean of squared differences between successive intervals and the percentage of adjacent RR intervals differing more than 50 ms), noninvasive spectral baroreflex sensitivity (Spe-BRS) and phenylephrine baroreflex sensitivity (Phe-BRS) were assessed before and after training. Mean SAP measured after exercise was lower than baseline (120+/-12 mmHg vs 128+/-12 mmHg, p = 0.05). Spe-BRS and Phe-BRS increased significantly after exercise, from 11.8+/-6.1 ms/mmHg to 16.0+/-7.8 ms/mmHg (p = 0.034), and from 16.0+/-8.8 ms/mmHg to 21.9+/-9.3 ms/mmHg (p = 0.022), respectively. A parallel increase was also observed in SDNN (from 81+/-44 ms to 96+/-53 ms, p = 0.02), but the other HRV indices showed no significant differences between pre- and post-exercise. CONCLUSIONS: A single session of mild exercise performed by sedentary young men leads to significant autonomic nervous system improvement, which suggests that even mild physical activity is beneficial for neural cardiac regulation and should be recommended to sedentary healthy subjects.

Adolescent↗
PubMed2005

Anemia in chronic heart failure patients: comparison between invasive and non-invasive prognostic markers.

BACKGROUND: The prognosis of chronic heart failure (CHF) remains poor despite advances in medical management. Several different variables determine prognosis. Recently anemia has emerged as an independent prognostic variable in the evaluation of CHF. It is therefore important to analyze the role of anemia in patients with mild to severe CHF already well characterized by hemodynamic, echo-Doppler, and cardiopulmonary exercise testing. OBJECTIVE: We performed this study to evaluate, in a large general cohort of CHF patients, the frequency of anemia and its correlation with their clinical profile. We assessed the prognostic value of anemia in relation to other known prognostic variables. METHODS: Two-dimensional echocardiography, right heart catheterization, cardiopulmonary tests and laboratory examinations were performed in a population of 980 consecutive patients with CHF (53 +/- 9.4 years, 85% male, LVEF 25 +/- 8%; 45% with NYHA class III-IV). A hemoglobin (Hb) concentration less than 12 g/dl was used to define anemic patients. The primary end point was cardiac death or urgent heart transplantation. RESULTS: Nineteen percent of patients were anemic. These patients had a lower body mass index (24 +/- 3 vs. 25 +/- 4 Kg/m2 p < 0.0004), a worse functional class (64% were in NYHA class III-IV vs 41% in the non-anemic group, p < 0.0001), poorer exercise capacity (12.4 vs. 14.8 ml/kg/min peak VO2, p < 0.0001) and increased right (7 +/- 5 vs. 5 +/- 4 mmHg, p < .0004) and left (21 +/- 9 vs. 19 +/- 10 p < 0.007) ventricular filling pressures. During a 3-year follow-up cardiac deaths occurred in 236 (24%) and 52 (5%) of patients received an urgent heart transplant. On univariate regression analysis anemia was significantly correlated with these "hard" cardiac events (39% of anemic patients vs 27% of non-anemic patients). By multivariate logistic regression analysis different prognostic models were identified using non-invasive, with or without peak VO2, or invasive parameters. The prognostic model including anemia (AUC(ROC): 0.720) showed similar accuracy in predicting cardiac events to other prognostic models with peak VO2 (AUC(ROC): 0.719) or invasive variables (AUC(ROC): 0.719). CONCLUSIONS: The present study demonstrates that anemia in CHF patients is associated with prognosis, worse NYHA functional class, exercise capacity and hemodynamic profiles. The relationship between anemia and mortality is independent of other simple non-invasive prognostic factors. Prognostic models with more complex or invasive independent predictors did not increase the accuracy to predict cardiac mortality or the need for urgent transplantation.

Anemia↗
PubMed2004

Different spectral components of 24 h heart rate variability are related to different modes of death in chronic heart failure.

AIMS: To assess whether analysis of heart rate variability (HRV) from 24 h Holter recordings provides information about the mode of death (pump failure vs. sudden death) in chronic heart failure (CHF). METHODS AND RESULTS: We analysed 24 h HRV in 330 consecutive CHF patients in sinus rhythm. Indices derived from time domain, spectral domain, and fractal analyses of 24 h automatic HRV were evaluated. Data from clinical assessment, echocardiography, right heart catheterization, exercise test, blood biochemical examination, and arrhythmia pattern were analysed. Patients were followed up for 3 years. Two simple multivariable models, both including 24 h spectral indices, were able to identify patients at higher risk of progressive pump failure and sudden death, respectively. Depressed power of night-time HRV (< or = 509 ms(2)) below 0.04 Hz [very low frequency (VLF)], high pulmonary wedge pressure (PWP > or = 18 mm Hg) and low left ventricular ejection fraction (LVEF < or = 24%) were independently related to death for progressive pump failure, while the reduction of power between 0.04 and 0.15 Hz at night (LF < or = 20 ms(2)) and increased left ventricular end-systolic diameter (LVESD > or = 61 mm) were linked to sudden mortality. CONCLUSION: Automatic spectral analysis of 24 h HRV provides independent risk indices related to mode of death in sinus rhythm CHF patients.

Circadian Rhythm↗
PubMed2004

Prevalent low-frequency oscillation of heart rate: novel predictor of mortality after myocardial infarction.

BACKGROUND: This study evaluates a novel method for postinfarction risk stratification based on frequency-domain characteristics of heart rate variability (HRV) in 24-hour Holter recordings. METHODS AND RESULTS: A new risk predictor, prevalent low-frequency oscillation (PLF), was determined in the placebo population of the European Myocardial Infarction Amiodarone Trial (EMIAT). Frequencies of peaks detected in 5-minute low-frequency HRV spectra were averaged to obtain the PLF index. PLF >or=0.1 Hz was the strongest univariate predictor of all-cause mortality associated with relative risk of 6.4 (95% CI, 3.9 to 10.6; P<10(-12)). In a multivariate Cox's regression model including clinical risk factors, mean RR interval, HRV index, low- and high-frequency HRV spectral power, and heart rate turbulence, PLF was the most powerful mortality predictor, with a relative risk of 4.6 (95% CI, 2.2 to 9.3; P=0.00003). Predictive power of PLF was blindly validated in the population of the Autonomic Tone and Reflexes After Myocardial Infarction (ATRAMI) trial. PLF >or=0.1 Hz was associated with univariate relative risk of 6.1 (95% CI, 2.9 to 12.9; P<10(-5)) for cardiac mortality or resuscitated cardiac arrest. In multivariate Cox's regression model including age, left ventricular ejection fraction, baroreflex sensitivity, mean RR interval, standard deviation of normal RR intervals, low- and high-frequency HRV spectral power, and heart rate turbulence, only left ventricular ejection fraction and PLF were significant predictors, with relative risks of 4.2 (95% CI, 1.5 to 11.7; P=0.007) and 3.6 (95% CI, 1.3 to 10.5; P=0.02), respectively. CONCLUSIONS: An innovative analysis of frequency-domain HRV, which characterizes the distribution of spectral power within the low-frequency band, is a potent and independent risk stratifier in postinfarction patients.

Adrenergic beta-Antagonists↗
PubMed2004

Different predictive values of electrophysiological testing and autonomic assessment in patients surviving a sustained arrhythmic episode.

BACKGROUND: Recent data suggest that the electrophysiological study (EPS) has limited value in the identification of high risk patients, so the aim of the present study was to evaluate if non-invasive measurement of baroreflex sensitivity (BRS), a marker of autonomic balance, provides additional prognostic information in patients surviving a sustained arrhythmic episode. METHODS AND RESULTS: The study group comprised 112 post myocardial infarction patients consecutively referred for EPS following documented ventricular fibrillation (VF) (20), sustained ventricular tachycardia (VT) (74) or a syncopal episode with subsequently documented non-sustained VT at Holter monitoring (18). BRS was assessed according to the transfer function method. A cardioverter - defibrillator (ICD) was implanted in 97 patients. During follow-up (median 315 days), appropriate ICD discharge occurred in 53 patients, and 3 more patients died suddenly. Sustained VT was induced in 84% and 77% of patients who did or did not develop arrhythmia at follow-up (p=0.34). No differences were found in age, sex, infarct site, drug therapy, resting RR interval or cycle of induced VT. Left ventricular ejection fraction (LVEF) < or =35%, New York Heart Association (NYHA) class >2 and BRS < or =3.3 ms/mmHg were found to be univariate predictors of arrhythmia recurrence. Multivariate models were obtained after grouping patients according to a moderately or severely depressed LVEF. Among the patients with LVEF < or =35%, BRS < or =3.3 ms/mmHg emerged as the only significant risk predictor of arrhythmia occurrence (sensitivity, specificity, positive and negative predictive value = 79%, 74%, 83% and 68%, respectively), whereas NYHA class >2 was a significant predictor among patients with LVEF >35%. CONCLUSIONS: Noninvasive BRS, but not EPS, is of value in predicting VT/VF episode recurrence in patients surviving a major arrhythmic event.

Adrenergic beta-Antagonists↗
PubMed2003

Short-term heart rate variability strongly predicts sudden cardiac death in chronic heart failure patients.

BACKGROUND: The predictive value of heart rate variability (HRV) in chronic heart failure (CHF) has never been tested in a comprehensive multivariate model using short-term laboratory recordings designed to avoid the confounding effects of respiration and behavioral factors. METHODS AND RESULTS: A multivariate survival model for the identification of sudden (presumably arrhythmic) death was developed with data from 202 consecutive patients referred between 1991 and 1995 with moderate to severe CHF (age 52+/-9 years, left ventricular ejection fraction 24+/-7%, New York Heart Association class 2.3+/-0.7; the derivation sample). Time- and frequency-domain HRV parameters obtained from an 8' recording of ECG at baseline and during controlled breathing (12 to 15 breaths/min) were challenged against clinical and functional parameters. This model was then validated in 242 consecutive patients referred between 1996 and 2001 (validation sample). In the derivation sample, sudden death was independently predicted by a model that included low-frequency power (LFP) of HRV during controlled breathing < or =13 ms2 and left ventricular end-diastolic diameter > or =77 mm (relative risk [RR] 3.7, 95% CI 1.5 to 9.3, and RR 2.6, 95% CI 1.0 to 6.3, respectively). The derivation model was also a significant predictor in the validation sample (P=0.04). In the validation sample, LFP < or =11 ms2 during controlled breathing and > or =83 ventricular premature contractions per hour on Holter monitoring were both independent predictors of sudden death (RR 3.0, 95% CI 1.2 to 7.6, and RR 3.7, 95% CI 1.5 to 9.0, respectively). CONCLUSIONS: Reduced short-term LFP during controlled breathing is a powerful predictor of sudden death in patients with CHF that is independent of many other variables. These results refine the identification of patients who may benefit from prophylactic implantation of a cardiac defibrillator.

Death, Sudden, Cardiac↗
PubMed2003

Antiarrhythmic effects of omega-3 fatty acids: from epidemiology to bedside.

Omega-3 polyunsaturated fatty acids are emerging as a safe and effective means to reduce sudden death after acute myocardial infarction. This review summarizes the epidemiological background for the use of omega-3 fatty acids with this indication, clinical trials performed so far, and experimental data supporting their antiarrhythmic efficacy.

Animals↗
PubMed2003

Ambulatory electrocardiogram-based tracking of T wave alternans in postmyocardial infarction patients to assess risk of cardiac arrest or arrhythmic death.

INTRODUCTION: This is the first study to assess T wave alternans (TWA) analyzed from routine ambulatory electrocardiograms (AECGs) to identify postmyocardial infarction (post-MI) patients at increased risk for arrhythmic events. METHODS AND RESULTS: The new method of modified moving average (MMA) analysis was used to measure TWA magnitude in 24-hour AECGs from ATRAMI, a prospective study of 1,284 post-MI patients. Using a nested case-control approach, we defined cases as patients who experienced cardiac arrest due to documented ventricular fibrillation or arrhythmic death during the follow-up period of 21 +/- 8 months. We analyzed 15 cases and 29 controls matched for sex, age, site of MI, left ventricular ejection fraction, thrombolysis, and beta-blockade therapy. TWA was reported as the maximum 15-second value at three predetermined times associated with cardiovascular stress: maximum heart rate, 8:00 A.M., and maximum ST segment deviation. TWA increased significantly from baseline in both leads at each time point (P <<0.01) in cases and controls. TWA in V5 increased more in cases than controls during peak heart rate (P = 0.005) and at 8:00 A.M. (P = 0.02). A 4- to 7-fold higher odds of life-threatening arrhythmias was predicted by TWA level above the 75th percentile during maximum heart rate in leads V1 (odds ratio [OR] 4.2, 95% confidence interval [CI]: 1.1-16.3, P = 0.04) and V5 (OR 7.9, 95% CI: 1.9-33.1, P = 0.005). TWA at 8:00 A.M. also predicted risk in leads V1 (OR = 5.0, 95% CI: 1.2-20.5, P = 0.02) and V5 (OR = 4.2, 95% CI: 1.1-16.3, P = 0.04). CONCLUSION: TWA measurement from routine 24-hour AECGs is a promising approach for risk stratification for cardiac arrest and arrhythmic death in relatively low-risk post-MI patients.

Algorithms↗
PubMed2002

Exercise-induced increase in baroreflex sensitivity predicts improved prognosis after myocardial infarction.

BACKGROUND: Despite the rational expectation for a survival benefit produced by exercise training among post-myocardial infarction (MI) patients, direct evidence remains elusive. Clinically, changes in autonomic balance toward lower vagal activity have consistently been associated with increased mortality risk; conversely, among both control and post-MI dogs, exercise training improved vagal reflexes and prevented sudden death. Accordingly, we tested the hypothesis that exercise training, if accompanied by a shift toward increased vagal activity of an autonomic marker such as baroreflex sensitivity (BRS), could reduce mortality in post-MI patients. METHODS AND RESULTS: Ninety-five consecutive male patients surviving a first uncomplicated MI were randomly assigned to a 4-week endurance training period or to no training. Age (51+/-8 versus 52+/-8 years), site of MI (anterior 41% versus 43%), left ventricular ejection fraction (52+/-13 versus 51+/-14%), and BRS (7.9+/-5.4 versus 7.9+/-3.4 ms/mm Hg) did not differ between the two groups. After 4 weeks, BRS improved by 26% (P=0.04) in trained patients, whereas it did not change in nontrained patients. During a 10-year follow-up, cardiac mortality among the 16 trained patients who had an exercise-induced increase in BRS >or = 3 ms/mm Hg (responders) was strikingly lower compared with that of the trained patients without such a BRS increase (nonresponders) and that of the nontrained patients (0 of 16 versus 18 of 79 [23%], P=0.04). Cardiac mortality was also lower among responders irrespective of training (4% versus 24%, P=0.04). CONCLUSIONS: Post-MI exercise training can favorably modify long-term survival, provided that it is associated with a clear shift of the autonomic balance toward an increase in vagal activity.

Baroreflex↗
PubMed2002

Heart rate turbulence-based predictors of fatal and nonfatal cardiac arrest (The Autonomic Tone and Reflexes After Myocardial Infarction substudy).

A previous report on heart rate (HR) turbulence showed its value in postinfarction risk stratification. The present study determines the predictive value of HR turbulence in a low-risk population after acute myocardial infarction and provides insight into its pathophysiologic correlates. With use of the database of the The Autonomic Tone and Reflexes After Myocardial Infarction (ATRAMI) study, data were obtained from 1,212 survivors with a mean duration of follow-up of 20.3 months. The a priori end point was defined as the combination of fatal cardiac arrest and nonfatal cardiac arrest. HR turbulence characterized by turbulence onset (TO) and turbulence slope (TS) was calculated and correlated with baroreflex sensitivity (BRS) and the SD of the normal-to-normal RR intervals (SDNN). A composite index of cardiac autonomic function was assessed by combining HR turbulence (TO and TS), BRS, and SDNN. Both TO and TS correlated moderately but significantly with BRS and SDNN (r = 0.26 to 0.44, p <0.001 for all correlations). On Cox's univariate regression analysis, the RRs for abnormal values of TO, TS, and the combination of abnormal TO and TS were 1.86 (95% confidence interval [CI] 0.96 to 3.61, p = 0.065), 4.08 (95% CI 2.11 to 7.89, p <0.0001), and 6.87 (95% CI 3.06 to 15.45, p <0.0001), respectively. The composite autonomic index (combined TO, TS, BRS, and SDNN) was the strongest risk predictor: for all 4 abnormal factors, RR 16.79 (95% CI 6.01 to 46.89, p <0.0001). On multivariate analysis, abnormal TO and TS, and left ventricular ejection fraction remained as independent predictors: RRs 4.07 (95% CI 1.70 to 9.77, p = 0.0017) and 3.53 (95% CI 1.76 to 7.06, p = 0.0004), respectively. In a separate model, the composite autonomic index was the strongest multivariate risk predictor: RR 8.67 (95% CI 2.72 to 7.65, p = 0.0003) for all abnormal factors, and adjusted for left ventricular ejection fraction. Thus, this study confirms the independent value of HR turbulence in predicting fatal cardiac arrest and nonfatal cardiac arrest in a low-risk post-acute myocardial infarction population. By combining HR turbulence, BRS, and SDNN, a comprehensive assessment of cardiac autonomic reflexes and modulation can be obtained.

Autonomic Nervous System↗
PubMed2002

Measuring baroreflex sensitivity from the gain function between arterial pressure and heart period.

We tested an innovative approach for estimating baroreflex sensitivity (BRS) from the gain function between spontaneous oscillations of systolic arterial pressure (SAP) and heart period (HP). The major goal was to assess the practical implications of abandoning the classical coherence criterion (> or =0.5) as regards measurability of BRS, and agreement with values of BRS obtained using the phenylephrine test (Phe-BRS). We studied 19 normal subjects, 44 patients with a history of previous myocardial infarction (MI) and 45 patients with chronic heart failure (CHF). The experimental protocol included recording of SAP and HP for 10 min of supine rest, and evaluation of Phe-BRS. From resting SAP and HP, the gain and coherence functions were computed. The new BRS index was obtained in all subjects by averaging the gain function over the whole low-frequency band (0.04-0.15 Hz) (whole-band average BRS, WBA-BRS). WBA-BRS was 7.4 (5.8-10.8) ms/mmHg [median (25th-75th percentile)] in normal controls, 3.1 (1.4-5.4) ms/mmHg in MI patients (P<0.001 compared with normals) and 5.0 (3.2-6.9) ms/mmHg in CHF patients (P<0.01 compared with normals). Using the coherence criterion, BRS could be measured in only 43% and 49% of MI and CHF patients respectively, and the proportion of the low-frequency band contributing to the measurement was 21% (14-47%) and 29% (16-35%) respectively. The correlation between WBA-BRS and Phe-BRS was 0.47, 0.63 and 0.36 in the normal, MI and CHF groups respectively (all P<0.001). The relative bias of WBA-BRS was -5.2 ms/mmHg (P<0.001) in normals, -1.4 ms/mmHg (P=0.004) in MI patients and -1.0 ms/mmHg (P=0.11) in CHF patients. The limits of agreement were -13 to 2.6, -7.4 to 4.6 and -9.3 to 7.3 ms/mmHg in the normal, MI and CHF groups respectively. Thus the WBA-BRS method standardizes the computation of BRS among subjects, and dramatically increases its measurability in subjects with pathology compared with the classical spectral technique based on the coherence criterion. Compared with Phe-BRS, WBA-BRS tends to give negatively biased results. The correlation and the magnitude of the limits of agreement between the two methods are similar to those observed previously using coherence-based spectral methods.

Adult↗