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Biomedical subjects

Mikko P Tulppo

Publications and source records attributed to Mikko P Tulppo.

14 recordsLinked to original sources
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

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↗
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

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↗
PubMed2004

Feedback effects of circulating norepinephrine on sympathetic outflow in healthy subjects.

The amplitude of low-frequency (LF) oscillations of heart rate (HR) usually reflects the magnitude of sympathetic activity, but during some conditions, e.g., physical exercise, high sympathetic activity results in a paradoxical decrease of LF oscillations of HR. We tested the hypothesis that this phenomenon may result from a feedback inhibition of sympathetic outflow caused by circulating norepinephrine (NE). A physiological dose of NE (100 ng.kg(-1).min(-1)) was infused into eight healthy subjects, and infusion was continued after alpha-adrenergic blockade [with phentolamine (Phe)]. Muscle sympathetic nervous activity (MSNA) from the peroneal nerve, LF (0.04-0.15 Hz) and high frequency (HF; 0.15-0.40 Hz) spectral components of HR variability, and systolic blood pressure variability were analyzed at baseline, during NE infusion, and during NE infusion after Phe administration. The NE infusion increased the mean blood pressure and decreased the average HR (P < 0.01 for both). MSNA (10 +/- 2 vs. 2 +/- 1 bursts/min, P < 0.01), LF oscillations of HR (43 +/- 13 vs. 35 +/- 13 normalized units, P < 0.05), and systolic blood pressure (3.1 +/- 2.3 vs. 2.0 +/- 1.1 mmHg2, P < 0.05) decreased significantly during the NE infusion. During the NE infusion after PHE, average HR and mean blood pressure returned to baseline levels. However, MSNA (4 +/- 2 bursts/min), LF power of HR (33 +/- 9 normalized units), and systolic blood pressure variability (1.7 +/- 1.1 mmHg2) remained significantly (P < 0.05 for all) below baseline values. Baroreflex gain did not change significantly during the interventions. Elevated levels of circulating NE cause a feedback inhibition on sympathetic outflow in healthy subjects. These inhibitory effects do not seem to be mediated by pressor effects on the baroreflex loop but perhaps by a presynaptic autoregulatory feedback mechanism or some other mechanism that is not prevented by a nonselective alpha-adrenergic blockade.

Adolescent↗
PubMed2004

Saturation of high-frequency oscillations of R-R intervals in healthy subjects and patients after acute myocardial infarction during ambulatory conditions.

This study was designed to assess the relationship between R-R interval length and heart rate (HR) variability in healthy subjects and patients after an acute myocardial infarction (AMI). Twenty-four-hour ambulatory ECG recordings were obtained for 76 healthy subjects and 82 post-AMI patients. The high-frequency (HF, 0.15-0.4 Hz) spectral power of R-R intervals was analyzed in 5-min sequences over 24 h and plotted as a function of the corresponding mean R-R interval length. Quadratic regression model was used to study the relationship between R-R interval length and HF power. If a distinct deflection point (R-R0) occurred in the quadratic regression (r >0.50) model before maximum R-R interval, indicating the plateau of HF power, the relationship between R-R interval and HF power was defined as saturated. Otherwise, the relationship was defined as linear (r >0.50) or low correlated (r >0.50). The relationship was saturated in 35, linear in 38, and low correlated in 3 healthy subjects. In post-AMI patients, the relationship was saturated in 9 subjects, linear in 44 subjects, and low correlated in 29 patients. The HF power analyzed from the 24-h period did not differ between the saturated and linear groups, but when analyzed from the linear portion only, HF spectral power was smaller in the linear than the saturated group both among healthy subjects (P <0.05) and post-AMI patients (P <0.05). Saturation of the HF oscillations of R-R intervals is a common phenomenon in healthy subjects and also present in post-AMI patients during ambulatory conditions. This saturation effect may bias the quantification of cardiac vagal function when HR variability is analyzed from Holter recordings.

Adult↗
PubMed2004

Heart rate dynamics after controlled training followed by a home-based exercise program.

Daily aerobic training results in autonomic control of the heart toward vagal dominance. The constancy of vagal dominance after controlled training followed by a home-based training program in accordance with contemporary guidelines is not known. We set out here to study whether the vagal dominance induced by 8 weeks of controlled aerobic training is preserved after a 10-month home-based training program. For the controlled study, healthy men were randomized as training (n=18) and control subjects (n=6). The training was started by a supervised 8-week period with six training sessions a week [45 (15) min each] at an intensity of 70-80% of maximum heart rate, followed by a home-based training program for 10 months in accordance with the American College of Sports Medicine recommendations. Cardiovascular autonomic function was assessed by analyzing HR variability over a 24-h period and separately during the night hours (midnight-6 a.m.). Maximal running performance improved during the controlled training 16 (7)% (range 4-31%, P<0.001) and remained 8 (8)% (range -3 to 23%, P<0.001) above the baseline level after the home-based training program. At night, the vagally mediated high-frequency (HF) power of R-R intervals increased during the controlled training from 6.7 (1.3) to 7.3 (1.1) ln ms2 ( P<0.001) and remained higher than the baseline after the home-based training [7.0 (1.3) ln ms2, P<0.05]. The changes in running performance correlated with the changes in HF power at night (r=0.41, P<0.05) and over 24 h (r=0.44, P<0.05) after the home-based training program. Similarly, the changes in body mass index correlated with the changes in HF power over 24 h (r=-0.44, P<0.05) after the home-based training program. The high vagal outflow to the heart after the home-based training is associated with good physical performance and body mass control.

Adaptation, Physiological↗
PubMed2003

Cardiovascular autonomic function correlates with the response to aerobic training in healthy sedentary subjects.

Individual responses to aerobic training vary from almost none to a 40% increase in aerobic fitness in sedentary subjects. The reasons for these differences in the training response are not well known. We hypothesized that baseline cardiovascular autonomic function may influence the training response. The study population included sedentary male subjects (n = 39, 35 +/- 9 yr). The training period was 8 wk, including 6 sessions/wk at an intensity of 70-80% of the maximum heart rate for 30-60 min/session. Cardiovascular autonomic function was assessed by measuring the power spectral indexes of heart rate variability from 24-h R-R interval recordings before the training period. Mean peak O2 uptake increased by 11 +/- 5% during the training period (range 2-19%). The training response correlated with age (r = -0.39, P = 0.007) and with the values of the high-frequency (HF) spectral component of R-R intervals (HF power) analyzed over the 24-h recording (r = 0.46, P = 0.002) or separately during the daytime hours (r = 0.35, P = 0.028) and most strongly during the nighttime hours (r = 0.52, P = 0.001). After adjustment for age, HF power was still associated with the training response (e.g., P = 0.001 analyzed during nighttime hours). These data show that cardiovascular autonomic function is an important determinant of the response to aerobic training among sedentary men. High vagal activity at baseline is associated with the improvement in aerobic power caused by aerobic exercise training in healthy sedentary subjects.

Adult↗
PubMed2003

Effects of aerobic training on heart rate dynamics in sedentary subjects.

This study was designed to assess the effects of moderate- and high-volume aerobic training on the time domain and on spectral and fractal heart rate (HR) variability indexes. Sedentary subjects were randomized into groups with moderate-volume training (n = 20), high-volume training (n = 20), and controls (n = 15). The training period was 8 wk, including 6 sessions/wk at an intensity of 70-80% of the maximum HR, lasting for 30 min/session in the moderate-volume group and 60 min/session in the high-volume group. Time domain, frequency domain, and short-term fractal scaling measures of HR variability were analyzed over a 24-h period. Mean HR decreased from 70 +/- 7 to 64 +/- 8 beats/min and from 67 +/- 5 to 60 +/- 6 beats/min (P < 0.001 for both) for the moderate- and high-volume training groups, respectively. The normalized high-frequency spectral component increased in both groups (P < 0.05). The normalized low-frequency component decreased significantly (P < 0.05), resulting in a marked decrease in low frequency-to-high frequency ratio in both groups. In addition, short-term scaling exponent decreased in both groups (P < 0.001). There were no significant differences in the changes of HR variability indexes between groups. Aerobic training in sedentary subjects results in altered autonomic regulation of HR toward vagal dominance. A moderate training volume is a sufficient intervention to induce these beneficial effects.

Adult↗
PubMed2003

Short-term correlation properties of R-R interval dynamics at different exercise intensity levels.

Methods based on non-linear heart rate (HR) dynamics have been suggested to probe features in HR behaviour that are not easily detected by the traditional HR variability indices. This study tested the hypothesis that analysis of correlation properties of R-R intervals provides useful information on HR fluctuation during exercise. High- (HF) and low-frequency (LF) spectral components and a short-term scaling exponent (alpha1) of HR variability, were analysed for nine healthy subjects at rest, during incremental and steady-state exercise, during atropine infusion and during incremental exercise after atropine administration. During the incremental exercise test alpha1 increased from rest to an intensity level of approximately 40% of VO2max (from 1.07+/-0.24 to 1.50+/-0.25, P<0.001) and thereafter decreased linearly until the end of exercise (from 1.50+/-0.25 to 0.38 +/- 0.10, P<0.001). Atropine infusion increased the scaling exponent alpha1 value from 0.91+/-0.23 to 1.37+/-0.31 (P<0.001). During exercise after atropine infusion, a linear reduction was observed in the scaling exponent alpha1 from 1.37+/-0.23 to 0.25+/-0.08 (P<0.001). Analogous changes in alpha1 were seen during long-term steady-state exercise compared to incremental exercise. Conventional HR variability indices did not show any significant changes during exercise at high exercise intensity levels. alpha1 correlated with the LF/HF ratio at rest (r=0.90, P<0.001), but the correlation was weaker after atropine (r=0.71, P<0.05) and during exercise (e.g. r=0.33, P=NS at the level of 40% of VO2max). In conclusion, incremental exercise test until exhaustion results in bidirectional changes in correlation properties of R-R interval dynamics. These changes can be explained by the intensity of vagal and sympathetic input to the sinus node during the different intensity levels of exercise. Changes in alpha1 values can be detected also in high intensity levels, when the conventional measures of HR variability can not be applied.

Adult↗
PubMed2002

Clinical applicability of heart rate variability analysis by methods based on nonlinear dynamics.

Analysis of heart rate (HR) variability has become an important widely used method for assessing cardiac autonomic regulation. Conventionally, HR variability has been analyzed with time and frequency domain methods. Analysis of HR dynamics by methods based on nonlinear systems theory has opened a novel approach for studying the abnormalities in HR behavior. Recent studies have shown that these measures, particularly scaling analysis methods of HR dynamics, are altered among various patients populations with cardiovascular diseases, and they provide prognostic information. Altered long-term scaling properties of HR dynamics and more random short-term HR fluctuation has been observed, e.g., among patients with previous myocardial infarction, and these alterations have been shown to be associated with increased mortality rate. A relatively large body of data indicate that altered scaling properties of R-R intervals are physiologically deleterious. These findings support the notion that some nonlinear methods, such as scaling and complexity measures, give clinically valuable information for risk stratification among various patient populations. This article provides a review of our current knowledge of the usefulness of dynamical measures of HR fluctuation.

Autonomic Nervous System↗