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Biomedical subjects

M Mäntysaari

Publications and source records attributed to M Mäntysaari.

At least 37 records · Page 2Linked to original sources
PubMed1995

Day-to-day variability of cardiac autonomic regulation parameters in normal subjects.

We examined the reproducibility of day-to-day variability in cardiovascular autonomic nervous function parameters (classical clinical tests and domain analysis of heart rate variability) in four healthy men during a period of 1 working week. The results did not show any significant difference in any of the parameters over the five repeated measurements. The maximum-minimum difference as percentage of the mean was under 15% for expiration to inspiration (E/I) ratio, Valsalva ratio, tachycardia ratio, 30/15 ratio, acceleration index and brake index; about 45% for baroreflex sensitivity for systolic and diastolic blood pressure and for root mean square difference (RMSSD) of successive R-R intervals; about 65-85% for low and high frequency bands, total power and medium to high frequency ratio; and about 125% for medium frequency band. The intraclass correlation coefficient (ICC) values showed that the agreement for classical autonomic parameters (except for brake index) was good. ICC for RMSSD, baroreflex sensitivity for systolic blood pressure and the spectral estimates of heart rate variation were less good. Coefficient of variation (CV) was 4% for E/I ratio, 2% for 30/15 ratio, 6% for Valsalva, 3% for tachycardia ratio, 4% for acceleration index and 5% for brake index. CV for baroreflex sensitivity and for RMSSD was about 20%. It is concluded that the variation in baroreflex sensitivity is clearly larger than in the classical autonomic nervous function parameters. One-minute fixed pace breathing period seems to be too short to allow reproducible measurement of RMSSD and the spectral parameters of heart rate variation. Learning effect could be excluded.

Adult↗
PubMed1995

Myocardial sympathetic nervous dysfunction detected with iodine-123-MIBG is associated with low heart rate variability after myocardial infarction.

UNLABELLED: The association between myocardial sympathetic innervation and heart rate variability after myocardial infarction was studied in a group of 12 men (aged 30-65 yr) 3 mo after their first myocardial infarction. METHODS: Viable myocardium was imaged using 123I-phenylpentadecanoic acid (pPPA). Functioning myocardial sympathetic nervous tissue was imaged using [123I]-metaiodobenzylguanidine (MIBG). Heart rate variability was measured as the ratio of maximum-to-minimum RR intervals in ECG during deep breathing. RESULTS: The patients were divided into normal (n = 6) and low (n = 6) heart rate variability groups. Myocardial infarction size (pPPA defect) was comparable in the normal and low heart rate variability groups. Even the MIBG defect size was not significantly different in the normal and low groups, the portion of viable myocardium with impaired sympathetic innervation (MIBG defect minus pPPA defect) was significantly greater in the low heart rate variability group than in the normal group. CONCLUSION: The extent of viable myocardium with disturbed sympathetic innervation was greater in patients with low heart rate variability as compared to those with normal heart rate variability 3 mo after myocardial infarction.

3-Iodobenzylguanidine↗
PubMed1994

Extent of cardiac autonomic denervation in relation to angina on exercise test in patients with recent acute myocardial infarction.

According to the current concept, anginal pain results from stimulation of sympathetic nerves within the heart. In this study, we evaluated the role of cardiac adrenergic denervation in exercise-induced angina pectoris in 15 men with recent acute myocardial infarction. Before discharge from the hospital, the patients were subjected to a symptom-limited exercise test. Three months after the infarction, cardiac scintigraphic studies using I-123 metaiodobenzylguanidine (MIBG), I-123 paraphenylpentadecanoic acid (pPPA), and Tc-99m sestamibi (MIBI) were performed in order to determine the extent of denervated myocardium, the size of infarction, and myocardium with reduced perfusion, respectively. MIBG defect (17.2 +/- 7.6% of left ventricular mass) (defect defined as an activity distribution < or = 30% of the maximal myocardial activity) was larger than pPPA defect (8.3 +/- 8.8%, p < 0.001) in all patients, which indicates that the area of myocardial necrosis was surrounded by viable myocardium with sympathetic denervation. The extent of viable but denervated myocardium was significantly greater in patients who developed angina pectoris than in patients without angina pectoris during the early exercise test (13.3 +/- 4.4% vs 5.0 +/- 2.4%, p < 0.001). In addition, patients with silent ischemia tended to have smaller areas of viable but denervated myocardium than patients with painful ischemia (5.7 +/- 3.8% vs 13.8 +/- 5.1%, p = 0.07). Thus, contrary to expectations, the extent of viable but denervated myocardium seems to be associated with increased pain sensitivity in patients with recent myocardial infarction.

Adrenergic Fibers↗
PubMed1994

Baroreflex sensitivity in men with recent myocardial infarction; impact of age.

We investigated the effect of age on baroreflex sensitivity (BRS) in 39 male patients, who had survived their first myocardial infarction (MI) and in 15 age-matched controls. BRS was inversely related to age in both MI patients (r = -0.632, P < 0.0001) and controls (r = -0.706, P < 0.0001). The relationship between BRS and age, however, was significantly different in MI patients as compared with healthy controls: BRS was markedly higher and the BRS-age regression slope was significantly steeper in controls than in MI patients. As a consequence, the decrease in BRS caused by MI (delta BRS = age-specific expected BRS--measured BRS) was related inversely to age (r = -0.66, P < 0.05) i.e. delta BRS was greatest among young MI patients. However, the relative BRS (BRS% = measured BRS divided by the age-specific expected BRS) did not correlate with age. The average BRS% of MI patients was 37% lower than that of controls. MI size and left ventricular (LV) systolic function did not correlate with BRS. BRS correlated with variables related to cardiac diastolic function (peak late LV filling rate r = -0.43, P < 0.05), exercise capacity (r = 0.31, P < 0.05) and the extent of ST-depression during exercise (r = -0.40, P < 0.05), but all these correlations lost their significance after the adjustment for age. In conclusion, age is a factor that should be taken into consideration when evaluating the mechanisms of BRS impairment associated with different diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Circadian variation of cardiac autonomic regulation during 24-h bed rest.

We examined the effect of circadian variation on cardiac autonomic regulation in 11 young and middle-aged, healthy men during 24-h bed rest. Cardiac parasympathetic regulation expressed significant circadian variation: sensitivity of baroreceptor reflex, standard deviation of R-R intervals and the power of high frequency component of R-R interval variability (HFP) increased during the evening (2000-2100 h), were highest during the night (0200-0300 h), and gradually decreased again towards afternoon (1400-1500 h). Cardiac sympathetic regulation, the power of medium frequency component of R-R interval variability (MFP), did not show any significant circadian variation. The autonomic response to orthostatic stress changed after the 24-h bed rest; the sympathetic dominance in response to assuming upright position was before bed rest principally attributable to increased sympathetic activity (MFP increase), whereas after bed rest this was due to withdrawal of parasympathetic activity (HFP decrease). We conclude that the effect of circadian variation must be taken into account, while assessing cardiac autonomic regulation in patients with acute cardiovascular disorders.

Adult↗
PubMed1992

Microcomputer-based monitoring of cardiovascular functions in simulated microgravity.

A microcomputer-based system for non-invasive monitoring of cardiovascular system in simulated microgravity is described. The system evaluates automatically, accurately and interactively heart beat intervals, beat-to-beat non-invasive finger arterial blood pressure (systolic, diastolic, mean and pulse pressure) using a Finapres device and beat-to-beat changes of thoracic blood volume using impedance changes. In addition, beat-to-beat evaluation of cardiac mechanical function including left ventricular ejection time, diastolic time, systolic time intervals, left ventricular ejection fraction estimate and several other contractility parameters, left ventricular volume, stroke volume and cardiac output estimates are performed with high degree of automaticity.

Blood Pressure↗
PubMed1992

Heart rate correction based on 'universal' regression equation--erroneous conclusions when studying cardiac mechanical function during stress.

This paper studies the possible errors associated with the use of a 'universal' regression equation in heart rate correction when used on mechanical cardiac function parameters. Systolic time interval rate correction, using Weissler regression equations, is taken as an example. The measurements were made during the isometric handgrip test, the orthostatic test, the Valsalva manoeuvre and the cold pressor test. It was observed that in most measurements rate correction caused a significant correlation between the changes in heart rate and the rate-corrected systolic time interval. It is considered that this new dependence between heart rate and the rate-corrected parameter makes the physiological interpretation of results more difficult. Therefore it is recommended that in stress provocations mechanical cardiac function parameters should not be rate-corrected by methods based on a 'universal' regression equation between heart rate and the mechanical function parameter.

Adolescent↗
PubMed1992

Noninvasive detection of cardiac sympathetic nervous dysfunction in diabetic patients using [123I]metaiodobenzylguanidine.

The association between clinical autonomic dysfunction and myocardial MIBG accumulation was investigated. The study groups comprised 6 male diabetic patients with autonomic neuropathy (ANP+ group), 6 male diabetic patients without autonomic neuropathy (ANP-group), and 6 male nondiabetic control subjects. The mean age was comparable in all groups, and the subjects had no evidence of coronary heart disease. Reduced heart-rate variation in a deep-breathing test was used as a criterion for autonomic neuropathy. Immediately after injection, the peak net influx rate of MIBG to myocardium was significantly (P less than 0.05) reduced in both diabetic groups. At 6 hr after MIBG injection, the MIBG uptake of the myocardium was significantly (P less than 0.05) smaller in the ANP+ group than in the control group. In the ANP- group, the MIBG uptake of the myocardium was between that of the ANP+ group and that of the control group. Our data show that reduced myocardial MIBG accumulation is associated with autonomic dysfunction in diabetic patients, but it can occur to a lesser extent also in diabetic patients without apparent autonomic neuropathy. The measurement of the myocardial MIBG accumulation is a promising new method to detect cardiac sympathetic nervous dysfunction in diabetic patients.

3-Iodobenzylguanidine↗
PubMed1986

Individual relationship between heart rate and electromechanic systole in orthostatic test during autonomic blockade.

The aim of this work was to investigate the usefulness of the individual regression coefficients between the HR and the Q-A2 when studying their relationship during simultaneous changes in afterload and preload in combination with autonomic blockade. Twelve healthy male volunteers were studied in an orthostatic test done four times: without drugs (control test), after atropinization, after beta-blockade, as well as after combined beta-blockade and atropinization. The individual regression coefficients showed great inter-individual variation, and in average they were not significantly different in the four tests. However, it was observed that during the control test four, during the atropinization eight, during the beta-blockade three and during the combined beta-blockade and atropinization five individual regression coefficients were greater than -2.1, which is the regression coefficient used for the rate correction of the Q-A2 in males in the Weissler formula. It seems to use that the individual regression coefficents are useful in the evaluation of the relationship between the HR and the Q-A2 in pharmacological or physiological interventions, in which the intra-individual variation is great, and in which the number of subjects is often so small that group regressions are not very informative.

Adolescent↗