Temporal dynamics of the circadian heart rate following low and high volume exercise training in sedentary male subjects.

PURPOSE: Increased risk of arrhythmic events occurs at certain times during the circadian cycle with the highest risk being in the second and fourth quarter of the day. Exercise improves treatment outcome in individuals with cardiovascular disease. How different exercise protocols affect the circadian rhythm and the associated decrease in adverse cardiovascular risk over the circadian cycle has not been shown. METHODS: Fifty sedentary male participants were randomized into an 8-week high volume and moderate volume training and a control group. Heart rate was recorded using Polar Electronics and investigated with Cosinor analysis and by Poincaré plot derived features of SD1, SD2 and the complex correlation measure (CCM) at 1-h intervals over the 24-h period. RESULTS: Moderate exercise significantly increased vagal modulation and the temporal dynamics of the heart rate in the second quarter of the circadian cycle (p = 0.004 and p = 0.007 respectively). High volume exercise had a similar effect on vagal output (p = 0.003) and temporal dynamics (p = 0.003). Cosinor analysis confirms that the circadian heart rate displays a shift in the acrophage following moderate and high volume exercise from before waking (1st quarter) to after waking (2nd quarter of day). CONCLUSIONS: Our results suggest that exercise shifts vagal influence and increases temporal dynamics of the heart rate to the 2nd quarter of the day and suggest that this may be the underlying physiological change leading to a decrease in adverse arrhythmic events during this otherwise high-risk period.

Low ß-carotene concentrations increase the risk of cardiovascular disease mortality among Finnish men with risk factors.

BACKGROUND & AIMS: Healthy diet rich in fruits and vegetables is an important factor in prevention of cardiovascular diseases (CVD). Some previous epidemiological studies have suggested that dietary and serum carotenoids are associated with decreased CVD mortality, but the results have been inconsistent. We assessed relations between the concentrations of serum carotenoids and CVD mortality among Eastern Finnish men. METHODS & RESULTS: The study population consisted of 1031 Eastern Finnish men aged 46-65 years in the Kuopio Ischaemic Heart Disease Risk Factor (KIHD) cohort. Subjects were classified quartiles according to concentrations of carotenoids and subgroups according to risk factors. Hazard ratios of serum lycopene, α-carotene and ß-carotene were estimated by the Cox proportional hazard model after adjusting for potential confounding factors. During the median 15.9-year follow-up, 122 deaths from CVDs, were identified among the cohort subjects. Low serum concentrations of ß-carotene were strongly related to an increased CVD mortality risk after adjustment for confounders. For ß-carotene, the hazard ratio (95% confidence interval) for the lowest versus highest quartile was 2.23 (1.26-3.93; P=0.006). However, the strongest risk of CVD mortality was observed among smokers with lowest levels of ß-carotene (HR=3.15, 95%, CI: 1.19-8.33; P=0.020). Other carotenoids and the sum of carotenoids were not significantly related to increased risk of CVD mortality. CONCLUSIONS: Low concentrations of serum ß-carotene concentrations may increase the risk for CVD mortality among Eastern Finnish men; thus elevated serum concentrations of ß-carotene may have clinical and public health relevance.

Intensity of leisure-time physical activity and cancer mortality in men.

OBJECTIVE: there is a lack of evidence to show the role of exercise intensity in the prevention of cancer mortality because no previous studies have shown this relation. The relationship of leisure-time physical activity with cancer mortality was therefore assessed. METHODS: participants were from a population-based sample of 2560 men from eastern Finland with no history of cancer at baseline. Physical activity was assessed using the 12-month leisure-time physical activity questionnaire. During an average follow-up of 16.7 years, a total of 181 cancer related deaths occurred. RESULTS: an increase of 1.2 metabolic units (MET or metabolic equivalents of oxygen consumption; 1 SD in metabolic equivalents) in the mean intensity of leisure-time physical activity was related to a decrease (relative risk (RR) 0.85, 95% CI 0.72 to 0.99) in cancer mortality mainly due to lung and gastrointestinal cancers, after adjustment for age, examination year, alcohol consumption, smoking, body mass index and energy, fibre and fat intake. Men with leisure-time physical activity of more than 5.2 MET (highest quartile) had a lower (RR 0.63, 95% CI 0.40 to 0.99) cancer mortality compared with men whose mean intensity of physical activity was less than 3.7 MET (lowest quartile). The mean intensity of physical activity was related to the risk of cancer death among men who exercised at least 30 minutes per day on average. CONCLUSIONS: this prospective study indicates that the mean intensity of leisure-time physical activity is inversely associated with the risk of premature death from cancer in men.

Exercise workload, cardiovascular risk factor evaluation and the risk of stroke in middle-aged men.

OBJECTIVE: We investigated the prognostic significance of risk scores and exercise workload with respect to stroke. Background. There are no data on exercise workload combined with European Systematic Coronary Risk Evaluation (SCORE) in the prediction of stroke. METHODS: Exercise workload was measured by exercise test with an electrically braked cycle ergometer performed at baseline. The study is based on a random population-based sample of 1639 men (42-60 years) without history of type 2 diabetes or atherosclerotic cardiovascular disease including coronary heart disease, stroke or claudication. RESULTS: During an average follow-up of 16 years, a total of 97 strokes occurred, of which 71 were ischaemic strokes. Independent predictors for all strokes were European SCORE [for 1% increment, relative risk (RR): 1.12, 95% CI: 1.02 to 1.22, P=0.017), maximal workload (for 20 W increment, RR: 0.87, 95% CI: 0.80 to 0.95, P=0.003) and body mass index (for 5 kg m(-2) increment, RR: 1.08, 95% CI: 1.03 to 1.14, P=0.004), when adjusted for serum HDL, alcohol consumption, C-reactive protein, family history of coronary heart disease, exercise-induced ST changes and the use of medications for hypertension, dyslipidaemia or aspirin. The risk was 2.54-fold (95% CI: 1.27-5.09, P=0.008) for any strokes and 4.43-fold (95% CI 1.69-11.78, P=0.003) for ischaemic strokes amongst men with exercise capacity less than 162 W when compared with those with high exercise capacity over 230 W, after adjustment for risk factors. CONCLUSIONS: Low exercise workload predicts an especially high risk for stroke in the presence of high risk SCORE.

Cardiac interbeat interval dynamics from childhood to senescence : comparison of conventional and new measures based on fractals and chaos theory.

BACKGROUND: New methods of R-R interval variability based on fractal scaling and nonlinear dynamics ("chaos theory") may give new insights into heart rate dynamics. The aims of this study were to (1) systematically characterize and quantify the effects of aging from early childhood to advanced age on 24-hour heart rate dynamics in healthy subjects; (2) compare age-related changes in conventional time- and frequency-domain measures with changes in newly derived measures based on fractal scaling and complexity (chaos) theory; and (3) further test the hypothesis that there is loss of complexity and altered fractal scaling of heart rate dynamics with advanced age. METHODS AND RESULTS: The relationship between age and cardiac interbeat (R-R) interval dynamics from childhood to senescence was studied in 114 healthy subjects (age range, 1 to 82 years) by measurement of the slope, beta, of the power-law regression line (log power-log frequency) of R-R interval variability (10(-4) to 10(-2) Hz), approximate entropy (ApEn), short-term (alpha(1)) and intermediate-term (alpha(2)) fractal scaling exponents obtained by detrended fluctuation analysis, and traditional time- and frequency-domain measures from 24-hour ECG recordings. Compared with young adults (<40 years old, n=29), children (<15 years old, n=27) showed similar complexity (ApEn) and fractal correlation properties (alpha(1), alpha(2), beta) of R-R interval dynamics despite lower spectral and time-domain measures. Progressive loss of complexity (decreased ApEn, r=-0.69, P<0.001) and alterations of long-term fractal-like heart rate behavior (increased alpha(2), r=0.63, decreased beta, r=-0.60, P<0.001 for both) were observed thereafter from middle age (40 to 60 years, n=29) to old age (>60 years, n=29). CONCLUSIONS: Cardiac interbeat interval dynamics change markedly from childhood to old age in healthy subjects. Children show complexity and fractal correlation properties of R-R interval time series comparable to those of young adults, despite lower overall heart rate variability. Healthy aging is associated with R-R interval dynamics showing higher regularity and altered fractal scaling consistent with a loss of complex variability.

Dynamic behavior and autonomic regulation of ectopic atrial pacemakers.

BACKGROUND: Heart rate (HR) variability reflects the neural regulation of normal pacemaker tissue, but the autonomic nervous regulation of abnormal atrial foci originating outside the sinus node has not been well characterized. We compared the HR variability of tachycardias originating from the ectopic foci and the sinus node. METHODS AND RESULTS: R-R-interval variability was analyzed from 24-hour Holter recordings in 12 patients with incessant ectopic atrial tachycardia (average HR 107+/-14 bpm), 12 subjects with sinus tachycardia (average HR 106+/-9 bpm), and 24 age- and sex-matched subjects with normal sinus rhythm (average HR 72+/-8 bpm). Time- and frequency-domain HR variability measures, along with approximate entropy, short- and long-term correlation properties of R-R intervals (exponents alpha(1) and alpha(2)), and power-law scaling (exponent beta), were analyzed. Time- and frequency-domain measures of HR variability did not differ between subjects with ectopic and sinus tachycardia. Fractal scaling exponents and approximate entropy were similar in sinus tachycardia and normal sinus rhythm, but the short-term scaling exponent alpha(1) was significantly lower in ectopic atrial tachycardia (0.71+/-0.16) than in sinus tachycardia (1.16+/-0.13; P<0.001) or normal sinus rhythm (1.19+/-0.11; P<0.001). Abrupt prolongations in R-R intervals due to exit blocks from the ectopic foci or instability in beat-to-beat R-R dynamics were the major reasons for altered short-term HR behavior during ectopic tachycardias. CONCLUSIONS: HR variability obtained by time- and frequency-domain methods does not differ between ectopic and sinus tachycardias, which suggests that abnormal atrial foci are under similar long-term autonomic regulation as normal pacemaker tissue. Short-term R-R-interval dynamics are altered toward more random behavior in ectopic tachycardia, which may result from a specific autonomic disturbance or an intrinsic abnormality of ectopic atrial pacemakers.

Altered complexity and correlation properties of R-R interval dynamics before the spontaneous onset of paroxysmal atrial fibrillation.

BACKGROUND: Trigger mechanisms for the onset of paroxysmal atrial fibrillation (AF) in patients without structural heart disease are not well established. New analysis methods of heart rate (HR) variability based on nonlinear system theory may reveal features and abnormalities in R-R interval behavior that are not detectable by traditional analysis methods. The purpose of this study was to reveal possible alterations in the dynamics of R-R intervals before the spontaneous onset of paroxysmal AF. METHODS AND RESULTS: Traditional time and frequency domain HR variability indices, along with the short-term scaling exponent alpha(1) and approximate entropy (ApEn), were analyzed in 20-minute intervals before 92 episodes of spontaneous, paroxysmal AF in 22 patients without structural heart disease. Traditional HR variability measures showed no significant changes before the onset of AF. A progressive decrease occurred both in ApEn (1.09+/-0.26 120 to 100 minutes before AF; 0.88+/-0.24 20 to 0 minutes before AF; P<0.001) and in alpha(1) (1.01+/-0.28 120 to 100 minutes before AF, 0.89+/-0.28 20 to 0 minutes before AF; P<0.05) before the AF episodes. Both ApEn (0. 89+/-0.27 versus 1.02+/-0.30; P<0.05) and alpha(1) (0.91+/-0.28 versus 1.27+/-0.21; P<0.001) were also lower before the onset of AF compared with values obtained from matched healthy control subjects. CONCLUSIONS: A decrease in the complexity of R-R intervals and altered fractal properties in short-term R-R interval dynamics precede the spontaneous onset of AF in patients with no structural heart disease. Further studies are needed to determine the physiological correlates of these new, nonlinear HR variability measures.

Natriuretic peptides and mortality after stroke.

BACKGROUND AND PURPOSE: Measurement of natriuretic peptides provides prognostic information in various patient populations. The prognostic value of natriuretic peptides among patients with acute stroke is not known, although elevated peptide levels have been observed. METHODS: A series of 51 patients (mean age, 68+/-11 years) with first-ever ischemic stroke underwent a comprehensive clinical examination and measurements of plasma atrial natriuretic peptides (N-ANP) and brain natriuretic peptides (N-BNP) in the acute phase of stroke. The patients were followed-up for 44+/-21 months. Risk factors for all-cause mortality were assessed. Control populations, matched for gender and age, consisted of 51 patients with acute myocardial infarction (AMI) and 25 healthy subjects. RESULTS: Plasma concentrations of N-ANP (mean+/-SD, 988+/-993 pmol/L) and N-BNP (751+/-1608 pmol/L) in the stroke patients were at the same level as those in the AMI patients (NS for both), but significantly higher than those of the healthy subjects (358+/-103 pmol/L, P<0.001 and 54+/-26 pmol/L, P<0.01, respectively). Elevated levels of N-ANP and N-BNP predicted mortality after stroke (risk ratio [RR] 4.3, P<0.01 and RR 3.9, P<0.01, respectively) and after AMI (P<0.05), and remained independent predictors of death after stroke even after adjustment for age, diabetes, coronary artery disease, and medication (RR 3.9, P<0.05 and RR 3.7, P<0.05, respectively). CONCLUSIONS: Plasma levels of natriuretic peptides are elevated in the acute phase of stroke and predict poststroke mortality.

Abnormalities in beat to beat complexity of heart rate dynamics in patients with a previous myocardial infarction.

OBJECTIVES: The purpose of this research was to study possible abnormalities in the beat to beat complexity of heart rate dynamics in patients with a previous myocardial infarction. BACKGROUND: Analysis of approximate entropy of time series data provides information on the complexity of both deterministic and random processes. It has been proposed that regularity or loss of complexity of RR interval dynamics may be related to pathologic states, but this hypothesis has not been well tested in cardiovascular disorders. METHODS: Approximate entropy and conventional time and frequency domain measures of RR interval variability were compared between 40 healthy subjects with no evidence of heart disease and 40 patients with coronary artery disease and a previous Q wave myocardial infarction. The groups were matched with respect to age, and cardiac medication was discontinued in the patients with coronary artery disease before the 24-h electrocardiographic recordings. RESULTS: Approximate entropy was significantly higher in the postinfarction patients (1.21 +/- 0.18 [mean +/- SD]) than in the healthy subjects (1.05 +/- 0.11, p < 0.001), whereas the standard deviation of RR intervals (63 +/- 19 vs. 86 +/- 23 ms, p < 0.001) and the very low, low and high frequency spectral components were lower (p < 0.01, p < 0.001, p < 0.05, respectively). Approximate entropy was not related to the time domain or the spectral components of heart rate variability and was more commonly abnormal in postinfarction patients (62.5%) than any linear measure (from 20% to 42.5%) when the 90% percentile of the values obtained for healthy subjects was defined as the normal range for each measure. CONCLUSIONS: Despite reduced linear measures of heart rate variability, the unpredictability or randomness of beat to beat heart rate dynamics is increased in patients with a previous myocardial infarction. Complexity analysis of RR interval dynamics may provide useful information on abnormalities in heart rate behavior that are not easily detected by the commonly used moment statistics.

Prediction of sudden cardiac death by fractal analysis of heart rate variability in elderly subjects.

OBJECTIVES: The aim of this study was to test the hypothesis that abnormal scaling characteristics of heart rate (HR) predict sudden cardiac death in a random population of elderly subjects. BACKGROUND: An abnormality in the short-term fractal scaling properties of HR has been observed to be related to a risk of life-threatening arrhythmias among patients with advanced heart diseases. The predictive power of altered short-term scaling properties of HR in general populations is unknown. METHODS: A random sample of 325 subjects, age 65 years or older, who had a comprehensive risk profiling from clinical evaluation, laboratory tests and 24-h Holter recordings were followed up for 10 years. Heart rate dynamics, including conventional and fractal scaling measures of HR variability, were analyzed. RESULTS: At 10 years of follow-up, 164 subjects had died. Seventy-one subjects had died of a cardiac cause, and 29 deaths were defined as sudden cardiac deaths. By univariate analysis, a reduced short-term fractal scaling exponent predicted the occurrence of cardiac death (relative risk [RR] 2.5, 95% confidence interval [CI], 1.9 to 3.2, p < 0.001) and provided even stronger prediction of sudden cardiac death (RR 4.1, 95% CI, 2.5 to 6.6, p < 0.001). After adjusting for other predictive variables in a multivariate analysis, reduced exponent value remained as an independent predictor of sudden cardiac death (RR 4.3, 95% CI, 2.0 to 9.2, p < 0.001). CONCLUSIONS: Altered short-term fractal scaling properties of HR indicate an increased risk for cardiac mortality, particularly sudden cardiac death, in the random population of elderly subjects.

Dynamic analysis of heart rate may predict subsequent ventricular tachycardia after myocardial infarction.

Dynamics analysis of RR interval behavior and traditional measures of heart rate variability were compared between postinfarction patients with and without vulnerability to ventricular tachyarrhythmias in a case-control study. Short-term fractal correlation of heart rate dynamics was better than traditional measures of heart rate variability in differentiating patients with and without life-threatening arrhythmias.

Heart rate dynamics in patients with stable angina pectoris and utility of fractal and complexity measures.

Dynamic analysis techniques may uncover abnormalities in heart rate (HR) behavior that are not easily detectable with conventional statistical measures. However, the applicability of these new methods for detecting possible abnormalities in HR behavior in various cardiovascular disorders is not well established. Conventional measures of HR variability were compared with short-term (< or = 11 beats, alpha1) and long-term (> 11 beats, alpha2) fractal correlation properties and with approximate entropy of RR interval data in 38 patients with stable angina pectoris without previous myocardial infarction or cardiac medication at the time of the study and 38 age-matched healthy controls. The short- and long-term fractal scaling exponents (alpha1, alpha2) were significantly higher in the coronary patients than in the healthy controls (1.34 +/- 0.15 vs 1.11 +/- 0.12 [p <0.001] and 1.10 +/- 0.08 vs 1.04 +/- 0.06 [p <0.01], respectively), and they also had lower approximate entropy (p <0.05), standard deviation of all RR intervals (p <0.01), and high-frequency spectral component of HR variability (p <0.05). The short-term fractal scaling exponent performed better than other heart rate variability parameters in differentiating patients with coronary artery disease from healthy subjects, but it was not related to the clinical or angiographic severity of coronary artery disease or any single nonspectral or spectral measure of HR variability in this retrospective study. Patients with stable angina pectoris have altered fractal properties and reduced complexity in their RR interval dynamics relative to age-matched healthy subjects. Dynamic analysis may complement traditional analyses in detecting altered HR behavior in patients with stable angina pectoris.

Fractal analysis of heart rate dynamics as a predictor of mortality in patients with depressed left ventricular function after acute myocardial infarction. TRACE Investigators. TRAndolapril Cardiac Evaluation.

A number of new methods have been recently developed to quantify complex heart rate (HR) dynamics based on nonlinear and fractal analysis, but their value in risk stratification has not been evaluated. This study was designed to determine whether selected new dynamic analysis methods of HR variability predict mortality in patients with depressed left ventricular (LV) function after acute myocardial infarction (AMI). Traditional time- and frequency-domain HR variability indexes along with short-term fractal-like correlation properties of RR intervals (exponent alpha) and power-law scaling (exponent beta) were studied in 159 patients with depressed LV function (ejection fraction <35%) after an AMI. By the end of 4-year follow-up, 72 patients (45%) had died and 87 (55%) were still alive. Short-term scaling exponent alpha (1.07 +/- 0.26 vs 0.90 +/- 0.26, p <0.001) and power-law slope beta (-1.35 +/- 0.23 vs -1.44 +/- 0.25, p <0.05) differed between survivors and those who died, but none of the traditional HR variability measures differed between these groups. Among all analyzed variables, reduced scaling exponent alpha (<0.85) was the best univariable predictor of mortality (relative risk 3.17, 95% confidence interval 1.96 to 5.15, p <0.0001), with positive and negative predictive accuracies of 65% and 86%, respectively. In the multivariable Cox proportional hazards analysis, mortality was independently predicted by the reduced exponent alpha (p <0.001) after adjustment for several clinical variables and LV function. A short-term fractal-like scaling exponent was the most powerful HR variability index in predicting mortality in patients with depressed LV function. Reduction in fractal correlation properties implies more random short-term HR dynamics in patients with increased risk of death after AMI.

Heart rate dynamics before spontaneous onset of ventricular fibrillation in patients with healed myocardial infarcts.

The traditional methods of analyzing heart rate (HR) variability have failed to predict imminent ventricular fibrillation (VF). We sought to determine whether new methods of analyzing RR interval variability based on nonlinear dynamics and fractal analysis may help to detect subtle abnormalities in RR interval behavior before the onset of life-threatening arrhythmias. RR interval dynamics were analyzed from 24-hour Holter recordings of 15 patients who experienced VF during electrocardiographic recording. Thirty patients without spontaneous or inducible arrhythmia events served as a control group in this retrospective case control study. Conventional time- and frequency-domain measurements, the short-term fractal scaling exponent (alpha) obtained by detrended fluctuation analysis, and the slope (beta) of the power-law regression line (log power - log frequency, 10(-4)-10(-2) Hz) of RR interval dynamics were determined. The short-term correlation exponent alpha of RR intervals (0.64 +/- 0.19 vs 1.05 +/- 0.12; p <0.001) and the power-law slope beta (-1.63 +/- 0.28 vs -1.31 +/- 0.20, p <0.001) were lower in the patients before the onset of VF than in the control patients, but the SD and the low-frequency spectral components of RR intervals did not differ between the groups. The short-term scaling exponent performed better than any other measurement of HR variability in differentiating between the patients with VF and controls. Altered fractal correlation properties of HR behavior precede the spontaneous onset of VF. Dynamic analysis methods of analyzing RR intervals may help to identify abnormalities in HR behavior before VF.

Fractal analysis and time- and frequency-domain measures of heart rate variability as predictors of mortality in patients with heart failure.

Time-domain measures of heart rate (HR) variability provide prognostic information among patients with congestive heart failure (CHF). The prognostic power of spectral and fractal analytic methods of HR variability has not been studied in the patients with chronic CHF. The aim of this study was to assess whether traditional and fractal analytic methods of HR variability predict mortality among a population of patients with CHF. The standard deviation of RR intervals, HR variability index, frequency-domain indexes, and the short-term fractal scaling exponent of RR intervals were studied from 24-hour Holter recordings in 499 patients with CHF and left ventricular ejection fraction < or =35%. During a mean follow-up of 665 +/- 374 days, 210 deaths (42%) occurred in this population. Conventional and fractal HR variability indexes predicted mortality by univariate analysis. For example, a short-term fractal scaling exponent <0.90 had a risk ratio (RR) of 1.9 (95% confidence interval [CI] 1.4 to 2.5) and the SD of all RR intervals <80 ms had an RR of 1.7 (95% CI 1.2 to 2.1). After adjusting for age, functional class, medication, and left ventricular ejection fraction in the multivariate proportional-hazards analysis, the reduced short-term fractal exponent remained the independent predictor of mortality, RR 1.4 (95% CI 1.0 to 1.9; p <0.05). All HR variability indexes were more significant univariate predictors of mortality in functional class II than in class III or IV. Among patients with moderate heart failure, HR variability measurements provide prognostic information, but all HR variability indexes fail to provide independent prognostic information in patients with the most severe functional impairment.

Heart rate variability in ischemic heart disease.

Major untoward events, such as life-threatening arrhythmias and acute coronary events, have been suggested to be triggered by the activation of the autonomic nervous system in patients with coronary artery disease. Analysis of heart rate variability by conventional time and frequency domain methods, as well as by newer methods derived from nonlinear system theory, has offered a novel approach for studying the abnormalities in cardiovascular neural regulation in ischemic heart disease. Heart rate variability has been shown to be altered among patients with ischemic heart disease as compared to their age-matched controls without the evidence of ischemic heart disease. There are also obvious differences in various measures of heart rate variability between patients with uncomplicated coronary artery disease and those with coronary artery disease with complicated myocardial infarction. Impaired high-frequency oscillations of heart rate is the most prominent feature in patients with uncomplicated coronary artery disease, suggesting mainly an impairment in vagal autonomic regulation. Patients with prior myocardial infarction have a reduced overall heart rate variability, and a specific spectral pattern with a reduced low-frequency spectral component has been observed in patients with prior myocardial infarction and impaired left ventricular function. Recent studies have shown that the new nonlinear measures, particularly fractal analysis methods of heart rate dynamics, can detect subtle changes in heart rate behavior that are not easily detected by traditional analysis methods from ambulatory recordings. Patients with prior myocardial infarction have steeper power-law slope analyzed from the ultra and very low-frequency spectral bands, and they also have more random short-term heart rate dynamics analyzed by the detrended fluctuation method. A large body of data indicate that reduced overall heart rate variability is associated with an increased risk of mortality and nonfatal cardiac events in patient with ischemic heart disease. Of particular note, recent studies indicate that fractal analysis methods perform even better than the traditional analysis methods of heart rate variability as predictors of death and the onset of life-threatening arrhythmic events in post-infarction populations. These findings support the notion that heart rate variability analysis methods, such as fractal and complexity measures as well as conventional techniques, give valuable clinical information among patients with ischemic heart disease.

[Ischemic sudden death: critical analysis of risk markers. Part VIII]. / Muerte súbita isquémica: análisis crítico de los marcadores de riesgo. Parte VIII.

Coronary artery disease is responsible for approximately 75-80% of sudden cardiac deaths in most industrialized countries. Risk factors can be divided in those which suggest structural heart disease and those reflecting abnormal physiological markers. Therapeutic strategies for primary prevention of sudden cardiac death require careful scrutiny. The systematic use of risk markers to identify and stratify high risk groups may be of help to establish primary prevention measures in daily practice. Different methods to stratify risk factors using ejection fraction, ventricular arrhythmias, heart rate variability, baroreflex sensitivity, and dispersion of repolarization are discussed in this article.