Prediction of ventricular tachyarrhythmias by intracardiac repolarization variability analysis.

Background: Arrhythmic sudden cardiac death (SCD) is generally mediated by ventricular fibrillation (VF) or fast ventricular tachycardia (FVT). We studied the predictive value of temporal QT variability detected from various sources of cardiac electric signal: surface ECG, far-field (FF), and near-field (NF) intracardiac electrograms (EGMs) in patients with implantable cardioverter-defibrillators (ICDs).

Methods And Results: Surface ECG and FF and NF intracardiac EGMs were simultaneously recorded at rest (mean heart rate, 74+/-15 bpm) for 4.

Heart rate variability and its changes over 5 years in older adults.

Purpose: to characterise the association between age, ageing and heart rate variability (HRV) in older individuals, 585 adults age >65 years with two 24-h Holter recordings in the Cardiovascular Health Study were studied.

Methods: heart rate (HR), ventricular premature contractions (VPCs), atrial premature contractions (APCs), frequency-domain, ratio-based and non-linear HRV and heart rate turbulence (HRT) were examined cross-sectionally by 5-year age groups and prospectively over 5 years. Analyses adjusted for gender, lower versus elevated cardiovascular (CV) risk and for the change in CV risk.

Increased ventricular premature contraction frequency during rem sleep in patients with coronary artery disease and obstructive sleep apnea.

Background: Patients with obstructive sleep apnea are reported to have a peak of sudden cardiac death at night, in contrast to patients without apnea whose peak is in the morning. We hypothesized that ventricular premature contraction (VPC) frequency would correlate with measures of apnea and sympathetic activity.

Methods: Electrocardiograms from a sleep study of 125 patients with coronary artery disease were evaluated.

Nighttime heart rate and survival in depressed patients post acute myocardial infarction.

Objectives: To determine if: 1) depressed patients with a recent acute myocardial infarction (AMI) have higher nighttime heart rate (HR) than nondepressed patients, and 2) elevated nighttime HR is associated with decreased survival post AMI. Depression is a risk factor for mortality post AMI. It is also associated with sleep disturbances and with elevated HR, which may be more pronounced at night.

Novel measures of heart rate variability predict cardiovascular mortality in older adults independent of traditional cardiovascular risk factors: the Cardiovascular Health Study (CHS).

Unlabelled: Novel HRV Predicts CV Mortality in the Elderly.

Background: It is unknown whether abnormal heart rate turbulence (HRT) and abnormal fractal properties of heart rate variability identify older adults at increased risk of cardiovascular death (CVdth).

Methods: Data from 1,172 community-dwelling adults, ages 72 +/- 5 (65-93) years, who participated in the Cardiovascular Health Study (CHS), a study of risk factors for CV disease in people >or=65 years.

Ambulatory ECG-based T-wave alternans predicts sudden cardiac death in high-risk post-MI patients with left ventricular dysfunction in the EPHESUS study.

Background: Exercise microvolt T-wave alternans (TWA) identifies sudden cardiac death (SCD) risk. TWA can be measured from ambulatory ECGs (AECGs) using modified moving average (MMA) method. Whether MMA TWA from AECGs predicts SCD in post-MI patients with left ventricular dysfunction (LVD) is unknown.

Autonomic information flow improves prognostic value of heart rate patterns after abdominal aortic surgery.

Purpose: Complex autonomic communication can be assessed by autonomic information flow (AIF) functions. The objective was to evaluate new complexity measures involving physiologically relevant time scales to predict the length of stay (LOS) in the hospital after abdominal aortic surgery (AAS). Our hypothesis was that AAS disrupts AIF, that restoration of AIF is necessary for recovery from major surgery, and that measures of AIF are superior to conventional heart rate variability (HRV) measures and equivalent to APACHE IV score in predicting LOS.

Development of more erratic heart rate patterns is associated with mortality post-myocardial infarction.

Cardiac patients often have sinus arrhythmia of nonrespiratory origin (erratic sinus rhythm [ESR]). ESR was quantified using hourly Poincaré and power spectral heart rate variability plots from normal-to-normal interbeat intervals and hourly values of the short-term fractal scaling exponent and correlations of normal-to-normal intervals in n = 60 nonsurvivors and n = 66 randomly selected survivors in the Cardiac Arrhythmia Suppression Trial. Hours were coded (ABN) as normal (0), borderline (0.

Higher levels of inflammation factors and greater insulin resistance are independently associated with higher heart rate and lower heart rate variability in normoglycemic older individuals: the Cardiovascular Health Study.

Objectives: To explore the relationship between (1) insulin resistance and inflammation factors with (2) higher heart rate (HR) and lower heart rate variability (HRV) in normoglycemic older adults.

Design: Cross-sectional population-based study.

Participants: Five hundred forty-five adults aged 65 and older with normoglycemia (fasting glucose <100 mg/dL) who participated in the Cardiovascular Health Study.

Circadian and ultradian rhythms in cardiac autonomic modulation.

Unlabelled: Heart rate variability (HRV) patterns reflect the changing sympathetic and parasympathetic modulation of the autonomic nervous system. While overall and circadian heart rate (HR) and HRV are well characterized by traditional measures, ultradian cycles of HR and HRV are not. We have developed a method for capturing these rhythms during sleep and have now applied it to 24-hour recordings.

Heart rate turbulence, depression, and survival after acute myocardial infarction.

Objective: Depression is a risk factor for mortality after acute myocardial infarction (AMI), possibly as a result of altered autonomic nervous system (ANS) modulation of heart rate (HR) and rhythm. The purposes of this study were to determine: a) whether depressed patients are more likely to have an abnormal HR response (i.e.

Diastolic dysfunction and autonomic abnormalities in patients with systolic heart failure.

Background: Patients with systolic heart failure (SHF) often have concomitant diastolic dysfunction (DD). SHF is associated with decreased heart rate variability (HRV), but the impact of degree of DD on HRV in SHF is unclear.

Methods And Results: HRV was measured in 139 patients, aged 64+/-12 years, 74% male, LVEF 30+/-8%.

Circadian and ultradian rhythms in heart rate variability.

Aim: Heart rate variability (HRV) patterns reflect the changing effect of sympathetic and parasympathetic modulation of the autonomic nervous system. While overall and circadian heart rate (HR) and HRV are well characterized by traditional measures, there is currently no method to measure ultradian cycles of HR and HRV.

Materials And Methods: HR/HRV for each 2-min interval was calculated using normal-to-normal interbeat intervals from overnight polysomnographic ECGs in 113 subjects, aged 58+/-10 years (65 male, 48 female).

Sometimes higher heart rate variability is not better heart rate variability: results of graphical and nonlinear analyses.

Objective: To determine the prevalence and effect on traditional heart rate variability (HRV) indices of abnormal HRV patterns in the elderly.

Methods: Hourly Poincaré plots and plots of spectral HRV from normal-to-normal interbeat intervals and hourly nonlinear HRV values were examined in a subset of 290 consecutive participants in the Cardiovascular Health Study. Only subjects in normal sinus rhythm with > or = 18 hours of usable data were included.

Low heart rate variability and the effect of depression on post-myocardial infarction mortality.

Background: Depression is associated with an increased risk for mortality after acute myocardial infarction (MI). The purpose of this study was to determine whether low heart rate variability (HRV) mediates the effect of depression on mortality.

Methods: Twenty-four-hour ambulatory electrocardiograms were obtained from 311 depressed patients with a recent acute MI who were enrolled in the Enhancing Recovery in Coronary Heart Disease (ENRICHD) clinical trial and from 367 nondepressed patients who met the ENRICHD medical inclusion criteria.

Traditional and nonlinear heart rate variability are each independently associated with mortality after myocardial infarction.

Introduction: Decreased heart rate variability (HRV) and abnormal nonlinear HRV shortly after myocardial infarction (MI) are risk factors for mortality. Traditional HRV predicts mortality in patients with a range of times post-MI, but the association of nonlinear HRV and outcome in this population is unknown.

Methods And Results: HRV was determined from 740 tapes recorded before antiarrhythmic therapy in Cardiac Arrhythmia Suppression Trial patients with ventricular premature contractions (VPCs) suppressed on the first randomized treatment.

Sex effects on heart rate variability in fibromyalgia and Gulf War illness.

Objective: To investigate autonomic abnormalities in male and female fibromyalgia (FM) and Gulf War illness (GWI) patients by comparing heart rate variability (HRV) with that of age- and sex-matched healthy controls.

Methods: Subjects included 26 (19 women, 7 men) with FM, 11 (6 men, 5 women) with GWI, and 36 (18 men,18 women) healthy controls. HRV was determined from Holter recordings obtained in the Clinical Research Center.

Including patients with diabetes mellitus or coronary artery bypass grafting decreases the association between heart rate variability and mortality after myocardial infarction.

Background: Decreased heart rate variability (HRV) is often assumed to be associated with mortality in all patients after myocardial infarction (MI), independent of clinical factors or time after MI.

Method: HRV was determined from Holter tapes in the Cardiac Arrhythmia Suppression Trial (CAST). Patients were 71 +/- 120 days after MI.

Effect of cognitive behavioral therapy on heart rate variability during REM sleep in female rape victims with PTSD.

Six female rape victims with posttraumatic stress disorder (PTSD) were assessed for sleep disturbances. Five responded to cognitive-behavioral therapy (CBT) and one did not complete treatment. Sympatho-vagal balance was measured using heart rate variability (HRV) during rapid eye movement (REM) sleep.

A simple method to identify sleep apnea using Holter recordings.

Introduction: Despite its severe cardiovascular and other consequences, sleep apnea syndrome frequently is undiagnosed. Because apneas result in repeated autonomic arousals associated with cyclic variations in heart rate (CVHR), we hypothesized that sleep apnea syndrome could be identified from simple HR tachograms (graphs of HR vs time) derived from ECG monitoring.

Methods And Results: HR tachograms were generated from 57 digitized ECGs (46 clinical patients undergoing diagnostic studies and 11 research subjects) obtained during overnight polysomnography.

Autonomic nervous system responses during sedative infusions of dexmedetomidine.

Background: The purpose of this study was to determine the effects of dexmedetomidine on systemic and cardiac autonomic reflex responses during rest and during thermal stress.

Methods: Volunteers received either placebo or low- or high-dose dexmedetomidine (target plasma concentrations 0.3 or 0.