Biomedical subjects

Heikki V Huikuri

Publications and source records attributed to Heikki V Huikuri.

At least 19 recordsLinked to original sources

PubMed2006

Family history and the risk of sudden cardiac death as a manifestation of an acute coronary event.

BACKGROUND: Observational studies have suggested that a parental history of sudden death increases one's risk of dying suddenly. This study tested the hypothesis that a family history of sudden cardiac death (SCD) is a risk factor for SCD caused by an acute coronary event. METHODS AND RESULTS: A retrospective case-control study included (1) consecutive victims of SCD (n=138) whose deaths were verified to be due to an acute coronary event without a history of prior myocardial infarction at medicolegal autopsy, (2) consecutive patients surviving an acute myocardial infarction (AMI; n=254), and (3) healthy control subjects (n=470). Family history of AMI and SCD among the first-degree relatives was ascertained in each study group. The incidence of SCD in the 1223 first-degree relatives of SCD victims was higher (5.2%) than that in the 2326 relatives of AMI survivors (3.3%; odds ration [OR] 1.6, 95% confidence interval [CI] 1.2 to 2.2, P<0.01) or the 3748 relatives of controls (OR 2.2; 95% CI 1.6 to 3.0, P<0.001). The history of SCD in 2 or more first-degree relatives was also higher (10.9%) among SCD victims than among AMI survivors (3.5%; OR 3.3, 95% CI 1.4 to 7.8, P<0.01) or controls (1.1%; OR 11.3, 95% CI 4.0 to 31.8, P<0.001). The family history of AMI did not differ between the SCD and AMI groups. Male gender and current smoking were the only coronary risk factors that were more prevalent among SCD victims than among AMI survivors (P<0.001 for both). CONCLUSIONS: Subjects with a family history of SCD have an increased risk of dying suddenly during an acute coronary event.

Aged↗

PubMed2006

Association between usage of beta-blocking medication and benefit from implantable cardioverter therapy.

The mortality benefit of implantable cardioverter defibrillator (ICD) therapy in primary and secondary prevention has been shown in various studies in patients with depressed left ventricular systolic function. This study determined the association between the mortality benefit of ICD therapy and the use of beta-blocking medication in randomized ICD trials. Eligible studies were randomized controlled trials of ICD therapy compared with conventional medical treatment reporting mortality as an outcome (Medline from May 1995 to May 2005). Ten randomized trials were included. Included studies were reviewed to determine the number of patients, follow-up, and the mortality of ICD and control groups. The analysis of these trials showed a strong negative association between the use of beta-blocking medication and the 2-year mortality benefit of ICD therapy (r = -0.81, p <0.01). In conclusion, the use of beta-blocking medication is associated with a reduced absolute mortality benefit of ICD therapy in reported randomized trials.

Adrenergic beta-Antagonists↗

PubMed2006

Heart rate recovery after maximal exercise is associated with acetylcholine receptor M2 (CHRM2) gene polymorphism.

The determinants of heart rate (HR) recovery after exercise are not well known, although attenuated HR recovery is associated with an increased risk of cardiovascular mortality. Because acetylcholine receptor subtype M2 (CHRM2) plays a key role in the cardiac chronotropic response, we tested the hypothesis that, in healthy individuals, the CHRM2 gene polymorphisms might be associated with HR recovery 1 min after the termination of a maximal exercise test, both before and after endurance training. The study population consisted of sedentary men and women (n = 95, 42 +/- 5 yr) assigned to a training (n = 80) or control group (n = 15). The study subjects underwent a 2-wk laboratory-controlled endurance training program, which included five 40-min sessions/wk at 70-80% of maximal HR. HR recovery differed between the intron 5 rs324640 genotypes at baseline (C/C, -33 +/- 10; C/T, -33 +/- 7; and T/T, -40 +/- 11 beats/min, P = 0.008). Endurance training further strengthened the association: the less common C/C homozygotes showed 6 and 12 beats/min lower HR recovery than the C/T heterozygotes or the T/T homozygotes (P = 0.001), respectively. A similar association was found between A/T transversion at the 3'-untranslated region of the CHRM2 gene and HR recovery at baseline (P = 0.025) and after endurance training (P = 0.005). These data suggest that DNA sequence variation at the CHRM2 locus is a potential modifier of HR recovery in the sedentary state and after short-term endurance training in healthy individuals.

Adaptation, Physiological↗

PubMed2006

Usefulness of T-wave loop and QRS complex loop to predict mortality after acute myocardial infarction.

The aim of the study was to assess whether parameters based on the T-wave loop and QRS loop predict mortality, and cardiac mortality in particular, during follow-up of consecutive survivors of acute myocardial infarction (AMI). Patients with AMI (n = 437), treated according to contemporary guidelines, underwent digital high-resolution electrocardiography in orthogonal Frank leads (X, Y, Z) 5 to 14 days after AMI. Several T-wave and QRS loop parameters, such as the width and height of the loops and their ratio, T-wave loop dispersion (TWLD), QRS loop dispersion, and co-sine of the angle between the main vectors of the T-wave and QRS loops (TCRT), were calculated using a custom-made software package. During an average follow-up period of 43 +/- 14 months, 53 patients (12%) died. Of these 53 deaths, 35 were cardiac. TWLD and TCRT were the T-wave loop/QRS loop parameters that best predicted for cardiac mortality on univariate comparison (35.4 +/- 5.62 vs 32.8 +/- 2.87 for TWLD, p < 0.001 and -0.135 +/- 0.665 vs -0.657 +/- 0.518 for TCRT, p < 0.001, alive vs cardiac death, respectively). After adjustment for clinical risk markers in the Cox regression analysis, TWLD still significantly predicted for cardiac mortality (p < 0.05); however, TCRT had lost its predictive power. TWLD did not have significant univariate or multivariate association with noncardiac mortality. In conclusion, TWLD that describes the shape of the T-wave loop is a specific predictor of cardiac death and independent of the clinical risk markers in the current treatment era of patients with AMI.

Aged↗

PubMed2006

Cardiac vagal outflow after aerobic training by analysis of high-frequency oscillation of the R-R interval.

This study was designed to assess the effect of aerobic training on the dynamics between the R-R interval length and the high-frequency (HF) oscillation of the R-R interval. Seventeen healthy males (26+/-2 years) participated in an 8-week aerobic training intervention. The mean HF spectral power (0.15-0.4 Hz) of the R-R interval and the mean R-R interval length were analyzed from 24-h recordings. HF power was also analyzed in 5-min sequences and plotted as a function of the corresponding mean R-R interval length. The relationship between the R-R interval length and the HF power was analyzed by a quadratic regression model. The relationship was defined as saturated if the distinct deflection point of the model occurred before the maximum R-R interval. Otherwise, the relationship was defined as linear. Additionally, the mean HF power was calculated from the linear portion of the R-R interval versus the HF power regression curve (HF index). Before the training intervention, seven subjects had a saturated HF power. After the intervention, five new cases of saturated HF power were observed. The mean HF power of the 24-h recording did not change in the group with a saturated HF power before training (7.4+/-0.8 vs. 7.6+/-0.8 ms(2)), but the HF index increased (6.7+/-0.7 vs. 7.1+/-0.7 ms(2), P<0.05). We conclude that enhanced vagal activity due to aerobic training increases the prevalence of the saturation of the HF oscillation of the R-R interval variability in healthy subjects. HF power calculated from unsaturated area detects more accurately subtle changes in the vagally mediated beat-to-beat variability of the R-R interval after aerobic training than the mean 24-h HF power.

Adult↗

PubMed2006

Cardiac autonomic control in patients with refractory epilepsy before and during vagus nerve stimulation treatment: a one-year follow-up study.

PURPOSE: To elucidate possible effect of vagus nerve stimulation (VNS) therapy on interictal heart rate (HR) variability in patients with refractory epilepsy before and after 1-year VNS treatment. METHODS: A 24-hour electrocardiogram (ECG) was recorded at the baseline and after 12 months of VNS treatment in 14 patients with refractory epilepsy, and once in 28 healthy age- and sex-matched control subjects. Time and frequency domain measures, along with fractal and complexity measures of HR variability, were analyzed from the ECG recordings. RESULTS: The mean value of the RR interval (p=0.008), standard deviation of N-N intervals (SDNN) (p<0.001), very-low frequency (VLF) (p<0.001), low-frequency (LF) (p=0.001), and high-frequency (HF) (p=0.002) spectral components of HR variability, and the Poincaré components SD(1) (p=0.005) and SD(2) (p<0.001) of the patients with refractory epilepsy were significantly lower than those of the control subjects before VNS implantation. The nocturnal increase in HR variability usually seen in the normal population was absent in patients with refractory epilepsy. VNS had no significant effects on any of the HR-variability indexes despite a significant reduction in the frequency of seizures. CONCLUSIONS: HR variability was reduced, and the nocturnal increase in HR variability was not present in patients with refractory epilepsy. One-year treatment with VNS did not have a marked effect on HR variability, suggesting that impaired cardiovascular autonomic regulation is associated with the epileptic process itself rather than with recurrent seizures.

Adult↗

PubMed2006

Functional significance of KCNH2 (HERG) K897T polymorphism for cardiac repolarization assessed by analysis of T-wave morphology.

BACKGROUND: Although KCNH2 (HERG) K897T polymorphism has been shown to be associated with the QT interval measured from 12-lead electrocardiogram (ECG), the functional significance of K897T polymorphism has been debated. The aim of this study was to test whether the K897T polymorphism of the KCNH2 (HERG) gene coding for the rapidly activating delayed rectifier K+ channel influences cardiac repolarization assessed by principal component analysis (PCA) of T-wave morphology. METHODS: Twelve-lead ECGs were digitized and T-wave morphology was analyzed with a PCA method in a population consisting of 228 healthy middle-aged subjects (121 women and 107 men). DNA samples were genotyped for the nucleotide 2690 A>C variation of the KCNH2 gene, corresponding to the KCNH2 K(lysine)897T(threonine) amino acid polymorphism. RESULTS: The allele frequencies were 0.86 (K) and 0.14 (T). The KCNH2 K897T polymorphism was associated with the total cosine R-to-T (TCRT), which reflects the wave front direction between depolarization and repolarization. TCRT was 0.421 in the genotype KK and 0.300 in the genotypes KT and TT (P = 0.04). The difference of TCRT was more marked between the KCNH2 K897T genotypes in women (P = 0.03) than in men (P = 0.52). CONCLUSIONS: The common K897T polymorphism of the cardiac potassium channel KCNH2 has functional significance for cardiac electrical properties. Subjects with a less common genotype, KT or TT, have smaller TCRT, which reflects dyssynchrony between depolarization and repolarization and is associated with an increased risk of cardiac mortality.

Adult↗

PubMed2006

Abnormalities in fractal heart rate dynamics in Chagas disease.

BACKGROUND AND METHODS: In order to study fractal HR dynamics in Chagas disease, we performed detrended fluctuation analysis (DFA)-along with analysis of power-law beta slope (beta index) and standard deviation of N-N intervals (SDNN)-in edited and unedited (with ventricular premature beats - VPBs, only in DFA analysis) series of R-R intervals from Holter monitoring of healthy controls (Group 0, n = 27) and Chagas disease patients with left ventricular (LV) ejection fraction >50% (Group 1, n = 137) and with LV ejection fraction <50% (Group 2, n = 23). RESULTS: When analyzed from the edited R-R interval data, the long-term scaling exponent alpha(2) is altered both among the Chagas patients with and without LV dysfunction. The short-term scaling exponent alpha(1) was higher in Group 1 Chagas patients as compared to controls (P < 0.01) and did not differ between Group 2 and controls. In unedited R-R interval series, alpha(1) was significantly reduced in Group 2 Chagas patients (0.55 +/- 0.002) as compared to controls (0.90 +/- 0.002) and Group 1 (0.91 +/- 0.003) (P < 0.001), but did not differ between Group 1 and controls. Similarly alpha(2) was lower in Group 2 compared to other groups (P < 0.001). SDNN did not differ between the groups, but the beta index derived from 1/f model was reduced both in Group 1 and 2 Chagas patients as compared to controls (P < 0.01). There was strong correlation (rs = 0.82; P < 0.001) between the beta and alpha(2) index from edited series. There was an inverse correlation (rs =-0.63, P < 0.01) between the number of VPBs and alpha(1) index of unedited series. CONCLUSIONS: The long-term fractal HR dynamics altered in chagasic patients with and without LV dysfunction could be an early sign of autonomic dysfunction. Patients with impaired LV function show marked alterations in short-term fractal HR dynamics toward more random behavior, mainly due to frequent ectopy. Prospective studies are necessary to define the value of these indices as predictors of death in Chagas disease.

Adult↗

PubMed2006

Long-term alterations of heart rate dynamics after coronary artery bypass graft surgery.

We tested the hypothesis that there may be long-term alterations in overall heart rate (HR) variability and in fractal HR behavior after coronary artery bypass graft (CABG) surgery. Reduced HR variability predicts morbidity in various patient populations. Continuous 24-h electrocardiograph recordings were performed in 25 elective CABG surgery patients 1 wk before the operation and 6 wk and 6 mo after. Seventeen of the patients also had recordings 12 mo after CABG. Time and frequency domain measures of HR variability were assessed, along with measurement of short-term fractal scaling exponent (alpha1), approximate entropy, and power-law relationship of relative risk interval variability (beta-slope). The high, low, very low, and ultra low frequency powers decreased significantly after the operation and remained at a significantly decreased level 6 wk and 6 and 12 mo after the operation than before (P = 0.01, P < 0.001, P < 0.001, and P < 0.001 for overall difference between the time points, respectively). The fractal scaling exponent alpha1 was at significantly more decreased 6 wk after (P < 0.05) CABG than before surgery but recovered to the preoperative level 6 mo after the operation. Long-term fractal organization (beta-slope) remained stable, but the overall complexity (approximate entropy) decreased toward more predictable HR dynamics during the study period (P < 0.01 after 1 yr). The predictive value of temporary and persistent long-term changes of the HR dynamics after CABG surgery for long-term outcome is not clear.

Aged↗

PubMed2005

Frequency of sudden cardiac death among acute myocardial infarction survivors with optimized medical and revascularization therapy.

The epidemiologic pattern of sudden cardiac death (SCD) may have changed in the modern treatment era of patients after an acute myocardial infarction (AMI). We evaluated the effect of optimized medical and revascularization therapy on the incidence of SCD after an AMI. A total of 2,130 consecutive patients (mean age 59 +/- 10 years) with an AMI from 2 European centers (Germany and Finland) was included in the study. In this population, 1,004 patients (47%) were treated with an optimized medical and revascularization strategy (defined as treatment with revascularization, beta blockers, aspirin, statins, and angiotensin-converting enzyme inhibitors). Nonoptimized treatment, defined as a lack of any optimized treatment, was received by 1,126 patients (53%). During the mean follow-up of 2.9 +/- 1.3 years, the incidence of SCD was very low among patients who received optimized treatment (1.2%, annual incidence 0.4%) compared with those who did not (3.6%, annual incidence 1.4%, p <0.01). The treatment strategy that had the greatest effect on differences in the SCD rate was revascularization therapy, with the hazard ratio of SCD being 2.1 (95% confidence interval 1.2 to 3.7, p <0.01) for SCD among nonrevascularized patients. Nonoptimized treatment was more often received by older patients, women, diabetic patients, and those with depressed left ventricular function. In conclusion, the incidence of SCD is low in the modern treatment era of patients after an AMI. Coronary revascularization seems to have a great effect on altered the epidemiologic pattern of SCD.

Adrenergic beta-Antagonists↗

PubMed2005

Individual differences in the responses to endurance and resistance training.

Large individual differences in the responsiveness of cardiorespiratory fitness (VO2peak) to endurance training have been observed in healthy subjects. We tested the hypothesis that subjects with a poor responsiveness to endurance training might benefit from resistance training in terms of aerobic fitness. The study population consisted of sedentary healthy male and female subjects (n=91, 42+/-5 year) assigned to either a training (n=73) or a control group (n=18). The randomized cross-over study design included a 2-week laboratory-controlled endurance or resistance training period with a 2-month detraining period between the interventions. Large individual differences were observed in the changes of VO2peak (DeltaVO2peak) after both the endurance (average 8+/-6 %, P<0.001, range -5 to +22%) and resistance training (average 4+/-5%, P<0.001, range -8 to +16%). The average increase in DeltaVO2peak between genders was similar after both the endurance (8+/-6% for both genders, P=ns) and resistance training (3+/-5% for males and 5+/-6% for females, P=ns). There was no linear relationship between the changes in VO2peak after each training intervention (r=-.09, P=ns). On the contrary, when the study group was divided into quartiles according to the endurance training response (1+/-3, 6+/-1, 9+/-1, and 16+/-3% increase in VO2peak), the group with the lowest response to endurance training increased VO2peak after the resistance training intervention (DeltaVO2peak 7+/-5%, P<0.001). The individual responsiveness of VO2peak to exercise training is related to the mode of training. The healthy males and females whose training response is low after endurance training seem to result in a marked improvement in their cardiorespiratory fitness by resistance training.

Adult↗

PubMed2005

Physiological background of the loss of fractal heart rate dynamics.

BACKGROUND: Altered fractal heart rate (HR) dynamics occur during various disease states, but the physiological background of abnormal fractal HR behavior is not well known. We tested the hypothesis that the fractal organization of human HR dynamics is determined by the balance between sympathetic and vagal outflow. METHODS AND RESULTS: A short-term fractal scaling exponent (alpha1) of HR dynamics, analyzed by the detrended fluctuation analysis (DFA) method, and the high-frequency (HF) and low-frequency (LF) spectral components of R-R intervals (0.15 to 0.4 Hz; n=13), along with muscle sympathetic nervous activity (MSNA) from the peroneus nerve (n=11), were assessed at rest and during cold face and cold hand immersion in healthy subjects. During cold face immersion, HF power increased (from 6.9+/-1.3 to 7.6+/-1.2 ln ms2, P<0.01), as did MSNA (from 32+/-17 to 44+/-14 bursts/100 heartbeats, P<0.001), and LF/HF ratio decreased (P<0.01). Cold hand immersion resulted in a similar increase in MSNA (from 34+/-17 to 52+/-19 bursts/100 heartbeats, P<0.001) but a decrease in HF spectral power (from 7.0+/-1.3 to 6.5+/-1.1 ln ms2, P<0.05) and an increase in the LF/HF ratio (P<0.05). The fractal scaling index alpha1 decreased in all subjects (from 0.85+/-0.27 to 0.67+/-0.30, P<0.0001) during cold face immersion but increased during cold hand immersion (from 0.77+/-0.22 to 0.97+/-0.20, P<0.01). CONCLUSIONS: The fractal organization of human HR dynamics is determined by a delicate interplay between sympathetic and vagal outflow, with the breakdown of fractal HR behavior toward more random dynamics occurring during coactivation of sympathetic and vagal outflow.

Adult↗

PubMed2005

Nonlinear heart rate variability in CABG patients and the preconditioning effect.

OBJECTIVE: Heart rate variability (HRV) is the most frequently used noninvasive diagnostic method in the assessment of cardiac autonomic control. The clinical relevance of HRV, especially nonlinear HRV in CPB patients has not been well studied. Short brief myocardial ischemia has been reported to influence HRV. We therefore hypothesis that the protective mechanism of ischemic preconditioning (IP) may involve in cardiac autonomic regulation. METHODS: Eighty-six CABG patients were randomized into a control and an IP group. The IP patients received two periods of 2-min ischemia followed by 3-min reperfusion by aortic cross-clamped. Holter data were collected in 86 CABG patients before and after surgery. Arrhythmias, linear and nonlinear HRV measures were analyzed. RESULTS: All time and frequency domain HRV variables as well as nonlinear indexes of HRV, the short-term (4-11 beats) scaling exponent alpha1, were suppressed significantly after surgery in both study groups. The lower pre- and postoperative exponent alpha1 predict the higher incidence of postoperative AF and worse postoperative outcome. The suppressed exponent alpha1 was attenuated in the IP group as compared to controls (P = 0.008). No other differences were observed in the changes in linear HRV measures between the groups. IP significantly reduced the incidence of postoperative arrhythmias and improved postoperative outcome. CONCLUSIONS: The present findings show that cardiac autonomic regulation is impaired after CABG. Nonlinear HRV exponent alpha1 is a more sensitive measure to predict the postoperative outcome in CABG patients. IP alleviates the extreme autonomic reactions after surgery, suggesting that cardiac autonomic regulation is involved in the IP protective mechanism.

Aged↗

PubMed2005

Prediction of sudden cardiac death after acute myocardial infarction: role of Holter monitoring in the modern treatment era.

AIMS: Current treatment may have changed the risk profiles of survivors of acute myocardial infarction (AMI). We evaluated the utility of Holter-based risk variables in the prediction of sudden cardiac death (SCD) among survivors of AMI treated with modern therapy. METHODS AND RESULTS: A total of 2130 AMI patients (mean age 59 +/- 10 years) were included. The patients were treated with modern therapeutic strategies, for example, 94% were on beta-blocking therapy and 70% underwent coronary revascularization. Various risk parameters from Holter monitoring were analysed. During a median follow-up of 1012 days (interquartile range: 750-1416 days), cardiac mortality was 113/2130, including 52 SCDs. All Holter variables predicted the occurrence of SCD (P<0.01), but only reduced post-ectopic turbulence slope (TS) (P<0.001) and non-sustained ventricular tachycardia (P<0.01) remained as marked SCD predictors after adjustment for age, diabetes, and ejection fraction (EF). In a subgroup analysis, none of the Holter variables predicted SCD among those with an EF < or = 0.35, but many variables predicted SCD among those with an EF >0.35, particularly TS (hazard ratio 5.9; 95% CI 2.9-11.7, P<0.001). CONCLUSION: Among the post-AMI patients treated according to the current guidelines, the incidence of SCD is low. Various Holter variables still predict the occurrence of SCD, particularly among the patients with preserved left ventricular function.

Death, Sudden, Cardiac↗

PubMed2005

Results of 24-hour ambulatory electrocardiography in dogs undergoing ovariohysterectomy following premedication with medetomidine or acepromazine.

OBJECTIVE: To investigate heart rate characteristics in dogs undergoing ovariohysterectomy following premedication with medetomidine or acepromazine. DESIGN: Clinical trial. ANIMALS: 43 client-owned dogs. PROCEDURE: 24-hour ambulatory electrocardiography was performed beginning approximately 1 hour prior to administration of premedications. Dogs were premedicated with medetomidine and butorphanol (n = 21) or acepromazine and butorphanol (22) and, approximately 85 minutes later, were anesthetized with propofol and isoflurane. Electrocardiographic recordings were examined to determine heart rate, cardiac conduction disturbances (ventricular premature complexes and atrioventricular block), and indices of heart rate variability (HRV). RESULTS: Minimum heart rate during the 24-hour recording period was significantly lower among dogs given medetomidine than among dogs given acepromazine, but during the postoperative period, heart rate increased in all dogs as they became physically active. Intraoperative time domain HRV indices were lower and the low frequency-to-high frequency ratio was higher among dogs given acepromazine than among dogs given medetomidine; however, significant differences between groups were no longer seen by 6 hours after surgery. There was no significant difference between groups with regard to the number of ventricular premature complexes or to values of scaling exponent alpha2 (a nonlinear measure of HRV). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that there are greater enhancements in vagally related heart rate indices in medetomidine-treated dogs that may persist until 6 hours after surgery. Despite the low heart rates, dogs given medetomidine showed expected responses to surgery and positional stimuli, and the 2 preanesthetic protocols may not result in different prevalences of ventricular premature complexes.

Acepromazine↗

PubMed2005

Heart rate turbulence after atrial premature beats before spontaneous onset of atrial fibrillation.

OBJECTIVES: This study was designed to assess the temporal changes in vagal responses to atrial premature beats before spontaneous onset of atrial fibrillation (AF). BACKGROUND: Enhanced vagal activity plays a major role in the onset and perpetuation of experimental AF, but the role of vagal activation in the onset of clinical AF episodes is not so well established. METHODS: We calculated heart rate turbulence after atrial premature impulses occurring 0 to 60 min before the onset of AF ("prior to AF") and compared it with the hourly means of the other hours of the 24-h electrocardiogram recordings ("non-AF hours") in 39 patients with structural heart disease and 29 patients with lone AF. Traditional heart rate variability measurements and approximate entropy (ApEn) were also analyzed. RESULTS: Turbulence onset (TO) was significantly less negative during the 1 h preceding AF than during the non-AF hours (0.71 +/- 1.76 vs. -0.35 +/- 1.46, p < 0.00001). Less negative TO before AF was observed among both the patients with structural heart disease (1.16 +/- 1.73 vs. 0.07 +/- 1.23; p < 0.0001) and those with lone AF (0.17 +/- 1.67 vs. -0.85 +/- 1.56; p < 0.0001). No significant difference was seen in the turbulence slope between the two periods, and none of the traditional frequency and time domain measurements differentiated between the periods; ApEn was significantly lower before AF than during the non-AF hours (p < 0.01). CONCLUSIONS: Altered heart rate dynamics, suggesting transient enhancement of vagal outflow after premature atrial excitation, are temporally related to spontaneous onset of clinical AF.

Adult↗

PubMed2005

Prevalence, characteristics and natural course of inappropriate sinus tachycardia.

AIMS: To study the prevalence, characteristics and natural course of inappropriate sinus tachycardia (IST). METHODS AND RESULTS: The prevalence and characteristics of IST were evaluated in a random sample of 604 middle-aged subjects. Seven of the subjects (1.16%) fulfilled the contemporary diagnostic criteria of IST. The systolic (147+/-11 mmHg vs. 130+/-13 mmHg, P<0.001) and diastolic ambulatory blood pressures (92+/-7 mmHg vs. 81+/-8 mmHg, P<0.001) were higher among the subjects with IST than among the controls. The other laboratory, echocardiographic and personality measurements, with the exception of the hostility score (10+/-2 vs. 8+/-3, P<0.001), revealed no differences between the groups. The natural course and prognosis of the disorder was assessed among the subjects fulfilling the IST criteria and nine previously diagnosed IST patients. During a mean follow-up of 6.0+/-2.4 years, none of the subjects developed any clinical or echocardiographic evidence of structural heart disease despite ongoing palpitations, and there was no significant reduction in the 24-h average HR (9+/-2 bpm vs. 89+/-8 bpm, P=0.204). CONCLUSION: The prevalence of IST in a middle-aged population was higher than previously assumed. Despite the chronic nature of the disorder, the prognosis of IST was benign. The causal relationship between IST and hypertension and/or hostile personality type remains speculative.

Chi-Square Distribution↗

PubMed2005

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. Patients were 70 +/- 121 days post-MI. Follow up was 362 +/- 241 days (70 deaths). The association between traditional time and frequency-domain HRV and mortality and nonlinear HRV and mortality were compared for the entire population (ALL), those without coronary artery bypass graft post-MI (no CABG), and those without CABG or diabetes (no CABG, no DIAB) using univariate and multivariate Cox regression analysis. Strength of association was compared by P values and Wald Chi-square values. Nonlinear HRV included short-term fractal scaling exponent, power law slope, and SD12 (Poincare dimension). For ALL and for no CABG, increased daytime SD12 had the strongest association with mortality (P=0.002 ALL and P <0.001 no CABG). For no CABG, no DIAB increased 24-hour SD12 hours had the strongest association (P <0.001) with mortality. Upon multivariate analysis, increased SD12, decreased ln ULF (ultra low frequency), and history of prior MI and history of congestive heart failure each remained in the model. CONCLUSION: Nonlinear HRV is associated with mortality post-MI. However, as with traditional HRV, this is diluted by CABG surgery post-MI and by diabetes. Results suggest that decreased long-term HRV and increased randomness of heart rate are each independent risk factors for mortality post-MI.

Algorithms↗