[Current perspectives in screening for cardiac diseases which most frequently cause sudden death during the practice of a sports activity]

Sudden death during sports activities is extremely rare in athletes and sportsmen. Its occurrence was calculated at 0.77 to 13 deaths per 100,000 sportsmen/year. The most frequent causes were coronary heart disease, coronary muscular bridges, congenital coronary artery anomalies, subarachnoid hemorrhage, hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, Marfan syndrome, aortic coarctation, myocarditis, pulmonary embolism, aortic stenosis, mitral valve prolapse and WPW syndrome. Clinical examination nearly identifies all cases of aortic stenosis, mitral valve prolapse with regurgitation, and aortic coarctation but misses the majority of cases of hypertrophic cardiomyopathy and coronary artery diseases. The use of Chest x-rays, ECG, Stress Test and Echocardiogram will provide the identification of most cases with increased risk of death. Although costs are not limited for professional athletes, this strategy does not totally overcome the problem because diagnostic errors are frequent (false positives and false negatives). Therefore it is important to admit the failure of these screening procedures and the necessity to adapt the strategy to cost-efficiency and time-efficiency in this population.

[Is autonomic control of the heart rate at rest altered by detraining? A study of heart rate variability in professional soccer players after the pretraining period and after the preparatory period for competitions]

The aim of this study was to assess the influence of detraining and training on the autonomic control of heart rate (HR), using time and frequency (spectral analysis) domain components of heart rate variability. Sixteen professional football players (26.7 +/- 3.8 years; 74.9 +/- 4.1 kg; 177 +/- 6.3 cm) were analysed at the end of a 1 month holiday (detraining) and after a 6 week training period (training). HR was recorded over 15 minutes with Holter equipment. The athletes rested in a supine position, in a quiet place and all test were performed between 8 and 10 AM. The subjects were requested to refrain from meals or caffeine for 12 hours before testing. In spite of the high intensity of the training period, there was no significant change in results from detraining condition to training condition. These results can have two possible explanations: (i) the high level of cardiovascular capacity in the detraining trial originated by the recreative physical activity that the players underwent during their holidays, and/or (ii) the training period was not long enough to promote any relevant effect on the autonomic control of HR.

Improved orthostatic tolerance in familial amyloidotic polyneuropathy with unnatural noradrenaline precursor L-threo-3,4-dihydroxyphenylserine

Disabling orthostatic hypotension, due to insufficiency of the autonomic nervous system, is a common complication of type I familial amyloidotic polyneuropathy (FAP). We investigated whether oral treatment with L-threo-3,4-dihydroxyphenylserine (L-threo-Dops), a noradrenaline precursor, might be of therapeutical benefit. In twenty untreated FAP patients, aged 33 to 44 years, who, because of severe orthostatic hypotension, were bedridden or constrained to a sitting life, supine and erect blood pressure (BP), plasma noradrenaline and tilting time, defined as the interval (s) between the beginning of a 60 degrees head-up tilt and the occurrence of orthostatic symptoms (dizziness, blurred vision or near syncope) were determined before and at repeated intervals during oral treatment with L-threo-Dops, 100 mg bid, for 6 months. Before treatment supine mean BP was 80 (76-85) mmHg (mean and 95% CI), supine plasma noradrenaline was low, 59 (41-77) pg/ml and tilting time ranged from 38 to 118 s. In response to tilt, mean BP immediately fell by 36 (31-41) mmHg, whereas plasma noradrenaline increased by only 11 (0-21) pg/ml (p = 0.05). After 3 to 5 days of treatment with L-threo-Dops all patients experienced marked improvement of their orthostatic tolerance as reflected by their ability to walk freely around. This effect sustained throughout the six months of treatment. Plasma noradrenaline increased moderately by 37 (11-63) pg/ml (p = 0.02) and supine mean BP increased by 8.6 (5.8-12.4) mmHg (p < 0.001) during chronic treatment. Supine or nocturnal hypertension did not develop, the fall in mean BP in response to tilt diminished by 12.5 (6.5-17.3) mmHg (p < 0.001) and tilting time became longer than 600 s in all patients. Because of its efficacy, its sustained duration of action and the lack of side effects, L-threo-Dops is advocated to improve orthostatic tolerance in patients with autonomic insufficiency due to FAP.

Circadian heart rate variability rhythm in shift workers

The objective of this study was to assess the influence of day-night cycle and sleep-awake period on the circadian pattern of heart rate variability (HRV). Twelve male oil refinery security shift workers, aged 39 +/- 7 years, were studied with 24-hour Holter monitor recordings during morning and night work periods. Hourly HRV parameters in the time and frequency domains were evaluated. For both shifts, all HRV parameters during awake or work periods were found not to be statistically different. In both day and night work shifts, the very low frequency and high-frequency components of HRV and the proportion of differences in successive R-R intervals greater than 50 ms increased during the sleep period, while the low frequency/high frequency ratio decreased. The low-frequency component in absolute units and the SD of the R-R interval did not show any variation in either shifts for the different periods. These results suggest that the circadian pattern of HRV seems to be predominantly related to sleep (supine) and wakefulness (standing) and remains independent of night-day cycle.

Heart rate variability in brain death

The sensitivity and specificity of heart rate variability (HRV) in the corroboration of brain death diagnosis in patients with acute traumatic intracranial lesions was evaluated in 20 patients with clinical criteria of brain death, nine patients in deep coma (Glasgow scale < 7) and 18 normal controls, all age matched. The electrocardiogram was sampled at 650 Hz and several parameters of HRV were calculated, in both time and frequency domains. The HRV parameters were significantly lower in the brain death group compared with the deep coma group. Linear discriminant analysis between brain death and deep coma patients was performed on a data set made of nine randomly selected patients with clinical criteria of brain death and nine patients in deep coma. Cross-validation was performed on the remaining 11 patients with clinical criteria of brain death. All patients in the data set were correctly classified (sensitivity and specificity of 100%). All patients in the cross-validation set were correctly classified (sensitivity of 100%). Further studies are necessary to evaluate the specificity of the method in the independent set of deep coma patients and in the follow-up of comatose and vegetative patients to identify irreversibility of HRV. Nevertheless, these results suggest that HRV analysis constitutes a fully sensitive and specific method for assessing brain death in potential organ donors with acute traumatic lesions of the brain. This fast, quantitative and bedside method seems very promising for the early confirmation of brain death, which is an important factor for the success of transplantation procedures and could have a high predictive value of brain death in comatose patients with brain injuries without fully diagnostic criteria.

[Basic concepts on the assessment of arterial baroreceptor sensitivity with non invasive methods. Estimate of the spontaneous gain of the arterial baroreceptor]

Arterial baroreceptors are sensitive to variation in both blood and pulse pressure. When there is an increase in those pressures, the baroreceptors increase the rhythm in which electric impulses are discharged. The impulses are transmitted by the receptors to the nervous centres of the brainstem. Once processed, these signals turn into sympathetic and vagal impulses. The vagal efferents control heart rate and the sympathetic efferents control heart rate, myocardial contractility and peripheral resistance. If there is an increase in blood pressure, then there will be a reflex decrease in the sympathetic activity and an increase in the parasympathetic one. The cardiac cronotropic response to blood pressure variation is very fast-with a delay of one or two beats. The amplitude of the response is a sigmoidal function. The greatest inclination of the response curve, that is to say, the area of greatest variation of the RR interval per unit of pressure, characterises the gain of the baroreceptors. The traditional method for obtaining the gain of the baroreceptor is a pharmacological one. Generally, the patient is given phenilephrine intravenously, in bolus and then the correlation between heart rate and the increase in intra-arterial blood pressure (reflex bradycardia) is calculated. Lately, it has been used the calculation of the spontaneous gain of the baroreceptor starting from a study carried out on the normal fluctuations in blood pressure and in the pulse interval both in time and frequency domain. The first case deals with the calculation of the gain of the function of transfer between the variations both in blood pressure and the RR intervals in the LF and the HF bands. The second case deals with the analysis of the occurrence of sequences of three beats with successive increases or decreases in blood pressure and in the RR interval. The gain is obtained from the linear regression of all the sequences. The application of these techniques to the recordings of blood pressure obtained by non-invasive methods (Finapress) makes possible that this procedure be followed under real conditions since it requires no previous stimulation of the cardiovascular system, which would probably interfere with the mechanisms to be evaluated, and requires no equipment in the condition which is normally required by experimental methodology.

High altitude-related neurocardiogenic syncope

This report presents a well-documented link between vasodepressor syncope, a marked increase of LF/HF ratio response to orthostasis (sympathetic dominance), and the efficacy of beta blockers in preventing orthostatic symptoms and absence of tilt-induced syncope, with normalization of the LF/HF ratio response.

[Neurocardiogenic syncope: its pathogenesis, diagnosis and treatment]

Neurocardiogenic syncope seems to be the most common cause of syncope. It is believed to be triggered by paradoxical autonomic reflexes, beginning in the ventricular mechanoreceptors of the heart, modulated by the brain stem and terminating in the autonomic efferent pathways (parasympathetic stimulation with bradycardia or asystole and sympathetic inhibition with severe hypotension). Tilt test has been used recently, as a safety and effective tool to identify subjects prone to syncope. Although the pathophysiology of this syndrome is not completely understood, pharmacological therapeutics seems very effective in resolving symptoms.

[The spectral analysis of heart rate variability. A comparative study between nonparametric and parametric spectral analysis in short series]

OBJECTIVE

to compare parametric (AR) and non parametric (FFT) spectral analysis results obtained in 512 beats series.

INTERVENTIONS

104 healthy subjects with normal physical examination and electrocardiogram were studied. The Ecg was recorded at rest, with controlled breathing at 15 cycles/min., and sampled at 300 Hz. The spectral VLF, LF and HF were calculated with FFT algorithm. For the same series, an auto-regressive analysis (AR) with optimized choice of the order of the model (AIC criterion) have been computed, VLF, LF and HF components were identified by AR spectral decomposition.

RESULTS

In both groups, athletes and sedentary, there were no statistically differences between VLF, LF, HF and LF/HF spectral indices computed by the two methods.

CONCLUSION

the results suggest that with controlled breathing it does not seems to exist any advantage in the use of AR spectral analysis to compute spectral components of heart rate variability, which is much more laborious that fixed bands non parametric FFT analysis.

Clear-cell sarcoma of tendons and aponeuroses studied by immunoscintigraphy

Clear-cell sarcoma is a rare tumor that arises in association with tendons and aponeuroses. Although it shares with malignant melanoma several histologic and ultrastructural features, it has a clinical course different from that of conventional melanomas. A case of clear-cell sarcoma studied by immunoscintigraphy with 99mTc-labeled F(ab')2 fragments of the monoclonal antibody 225.28 S is reported.

Neuronal regulation of cochlear blood flow in the guinea-pig

1. Previous studies have shown that electrical stimulation (ES) of the guinea-pig cochlea causes a neurally mediated increase in cochlear blood flow (CBF). It is known that the centrifugal neuronal input to the cochlea comes through the perivascular sympathetic plexus from the cervical sympathetic chain and along the vestibular nerve (VN) from the periolivary area of the brainstem. Both of these neuronal systems are distributed topographically in the cochlea. 2. In order to study the neural origins of ES-evoked CBF increase, laser Doppler flowmetry was used to test the following hypotheses. (a) The response is regional, that is, limited to the area of the cochlea stimulated. To test this we performed differential ES of the cochlear turns. CBF was measured from either the third or the first turn. (b) The response is mediated via autonomic receptors within the cochlea. To study this, we applied atropine, succinylcholine and idazoxan locally to the cochlea. (c) The response is influenced by neuronal input via the sympathetic cervical chain (SC) and components of the VN. We stimulated and sectioned the SC, and sectioned the VN, to test this hypothesis. 3. We observed that the CBF response was topographically restricted to the stimulated region. Locally applied muscarinic or nicotinic antagonists (atropine and succinylcholine respectively) did not affect the response. However, local idazoxan (an alpha 2-blocker) eliminated the response. Locally applied adrenaline and SC stimulation modified the dynamic range of the response. SC sectioning enhanced the responsiveness of the cochlear vasculature to ES. The VN section caused a temporary decrease in CBF and elimination of the ES-evoked CBF response. 4. We conclude that the release of dilating agents is topographical with respect to ES current flow, the ES-evoked CBF increase is peripherally mediated via alpha 2-receptors, and the response is influenced by input via the SC. The elimination of the response by VN sectioning proximal to the brainstem indicated that fibres of the VN mediate the CBF increase during direct cochlear ES. The data suggest that these fibres may be the efferent limb of a neural loop involved with the regulation of CBF. Such a system could provide a mechanism for the rapid increase in CBF with organ stress.

[The ambulatory recording of the long-term electrocardiogram]

In the past 5 years, a new approach was developed to evaluate the patient with sporadic symptoms as is the patient with syncope--the long-term ambulatory loop electrocardiogram monitoring. This method allow to assure the heart rate and rhythm at the moment of the symptoms hardly to be able with the other diagnostic tools disposable. The long-term ambulatory loop electrocardiogram monitoring was not to replace the actual tools, but complement them. Newer devices are smaller and too light, and have the ability of registry some minutes before and after the symptom. In the near future, the devices will be able to detected and store arrhythmias and to possess an easy and accessible management. With continued and profitable work that has been done in this area, a large proportion of patients with the diagnosis of "syncope of unknown etiology" can have a diagnostic and specify therapeutic and we will be able to assert with more strictness if the symptoms related by the patient are or not of cardiovascular origin.

Heart rate variability in 24-hour Holter recordings. Comparative study between short- and long-term time- and frequency-domain analyses

Mean hourly parameters obtained from all beats (long series) were compared with those obtained from a sample of 512 beats extracted each hour (short series) in nine presumably normal subjects. For both the short and long series, the spectral components, very low frequency, (VLF), low frequency (LF), and high frequency (HF), and time-domain indices (such as the Ewing statistic [PNN50] and RR standard deviation [SD-RR]), have been estimated. The spectral components LF and HF, estimated from the short and long series, were not significantly different, whereas significant differences were found between VLF, SD--RR, and PNN50. In both the short and long series, a strong correlation was found between LF and SD-RR and between HF and PNN50. The results suggest that, over a period of 24 hours, hourly LF and HF spectral components can be obtained using a single series of 512 beats every hour, with a great advantage over the evaluation of the mean hourly parameters. This method would be particularly useful in the study of circadian heart rate spectral analysis in Holter recordings with multiple artifacts or ectopic beats, and in general, when analysis of the entire 24-hour series is not feasible.

[Syncope: how to deal with it?]

Syncope is a frequent symptom, with an expensive protocol of difficult evaluation in face of its diverse causes. The authors describe the proper use of the tests available, particularly the tilt test, and conclude that nowadays only few syncopal episodes would remain unexplained.

[Sudden death in athletes]

Identifying all athletes at risk for exercise-related sudden death is difficult because systematic reliable screening is expensive. Nevertheless, if a perfect screening method existed, an appreciable number of athletes at increase risk for sudden death would not be identified. We think that a careful history designed to identify symptomatic athletes and a rigorous family history of congenital heart disease may be the most practical screening method.

[Malignant vasovagal syncope: a case of prolonged asystole induced by the "tilt" test and aggravated by therapy with a beta blocker (a clinical case and diagnostic, physiopathologic and therapeutic review)]

The authors describe a case of a middle-age male with recurrent syncope, in whom the tilt test was useful in the diagnosis and therapeutic evaluation. Malignant criteria of vasovagal syncope were established and the beta blocking worsening effect was documented, in spite of the general agreement of the first choice drug.

Middle cerebral artery occlusion increases cerebral capillary permeability

One hour after middle cerebral artery occlusion, the regional blood to brain transfer coefficient of alpha-aminoisobutyric acid was determined in eight barbiturate anaesthetized rats. The transfer coefficient (microliter/min-1/g-1) was significantly higher in the ischaemic cortex (10.6 +/- 2.3) than in the contralateral cortex (6.5 +/- 1.0). Cerebral regional capillary surface area was determined in another group of twelve rats using an alkaline phosphatase stain for the total capillary bed and fluorescein isothiocyanate-dextran to visualize the perfused capillaries. Perfused capillary surface area (cm2/cm3) was lower in the ischaemic cortex (141 +/- 31) than in the contralateral cortex (426 +/- 32). Using these values for the transfer coefficient, surface area and our previously published data of regional cerebral blood flow after middle cerebral artery occlusion, we calculated the extraction fraction of alpha-aminoisobutyric acid, the permeability-surface area product and the permeability of cerebral regional capillary beds. Although, there are numerous reports of permeability-surface area product of brain capillaries, to our knowledge, the permeability has never been determined before. The calculated extraction fraction ratio for alpha-aminoisobutyric acid for ischaemic cortex/contralateral cortex was 3.1. Similar ratios for permeability-surface area product and capillary permeability were 1.6 and 4.4, respectively. Thus, there was a more than four fold increase in capillary permeability to small molecules in the ischaemic cortex one hour after middle cerebral artery occlusion.

Spectral analysis of heart rate variability in athletes

The objectives of the study were to characterize power spectrum pattern of the heart rate variability and assessment of the relative contributions of sympathetic and parasympathetic cardiac nervous system control in athletes. Thirty-three male athletes, swimming (1), canoeing (10), cycling (6), athletics (4), football (3), roller-skating (2) and volleyball (7) aged 23.4 +/- 5.5 years, with a mean athletic level of 18 hours/week (8-45) and 33 sedentary healthy control subjects were included. Ecg signals were recorded after a period of 15 minutes in supine rest with controlled breathing at 15 cycles/min. Signal acquisition was done at 300 samples/sec. From 512 consecutive heart beats, we calculated mean average, standard deviation, maximum and minimum R-R intervals and, after computing the fast Fourier transform, total spectrum power, low frequency (LF), high frequency (HF) components and its ratio (LF/HF). The average R-R interval was 987.7 +/- 168.8 ms and 762.7 +/- 125.3 ms, the variance was 5.44 and 2.51 ms2 and ratio of R-R interval maximum/minimum (E/I ratio) 1.53 +/- 0.16 and 1.41 +/- 0.16, respectively for athletes and control group. Differences between groups were significant (p < 0.01) for all parameters, with higher variability in the athletes. Both spectral bands (LF and HF) had higher power in athletes (LF = 925 +/- 920 and HF = 2258 +/- 2349 ms2) than in the control group (LF = 442 +/- 446 and HF = 1179 +/- 1542 ms2) (p < 0.01). There were no significant differences for LF/HF ratio, or normalized LF (LF%) or normalized HF (HF%) between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of the aerobic capacity of blind people, by direct VO2 maximal measurement]

Physical activity is the basic factor to the human being in order to assume his place in society. Blind persons are often sedentary, which compromises its physical capacity. The present work evaluates the blind person's physical capacity, analysing possible differences related to sex, age and life time blindness. The sample was constituted by 27 blind (congenital and noncongenital), 18 male and 9 female, aged between 17 and 37 years old. To evaluate previous physical activity, a questionnaire, was answered which showed a dominant sedentary population. The maximum oxygen uptake was determined in a treadmill test using standard procedures (Bruce protocol). Medium results for boys were 45.85 +/- 8 ml/kg/min and for girls were 34.46 +/- 3.8 ml/kg/min. The difference between congenital and acquired blindness on the VO2max values was 2.9 ml/kg/min, not statistically significant (p = 0.468). Those findings lead us to consider that aerobic capacity mostly depends on type and intensity of physical exercise which may be temporary related to the onset of blindness and visual impairment degree.

[Study of the autonomous nervous system with heart rate spectral analysis in acute myocardial infarction]

OBJECTIVES

Characterize power spectrum pattern of heart rate variability (HRV) and assessment of relative cardiac nervous system in patients with acute myocardial interaction of sympathetic and parasympathetic infarction. We also compared the spectral power with some known prognostic risk variables.

STUDY DESIGN

Study of patients with acute myocardial infarction (AMI) and sedentary healthy subjects sex matched.

SUBJECT AND METHODS

19 postinfarction patients aged 55.7 +/- 10.5 years and 19 healthy subjects controls aged 53.9 +/- 11.0. ECG signals were recorded after 15 minutes of supine rest with controlled breathing at 15 cycles/min. Signal acquisition was done at 300 samples/sec. From 512 consecutive sinus beats, we calculated the average, standard deviation, maximum and minimum values and rate between the longest and shortest R-R interval (E/I). We also calculated, after computing the fast Fourier transform, the total spectrum power, low frequency component (LF, from 0.01 to 0.15 Hz), high frequency component (HF, from 0.15 to 0.50 Hz) and its ratio (LF/HF). Thereafter, we correlated these results with radionuclide ejection fraction, duration of treadmill test, Holter ventricular premature complex and localization of infarction.

RESULTS

The average R-R interval was 757.9 +/- 116.3 and 850.9 +/- 133.9 msec (p less than 0.05), the R-R corrected standard deviation was 15.3 +/- 6.0 and 38.2 +/- 8.5 msec (p less than 0.001) and ratio E/I was 1.13 +/- 0.06 and 1.32 +/- 0.09 (p less than 0.001) in AMI and control group, respectively. In AMI group, low frequency spectral band was very decreased (LF = 0.03 +/- 0.02 sec2) and high frequency was virtually absent (HF = 0.01 +/- 0.01 sec2) compared with control group (LF = 0.13 +/- 0.06 and HF = 0.14 +/- 0.15 sec2), p less than 0.001; ratio LF/HF was increased in AMI group. There were no significant differences between groups for normalized LF (LF%) and HF (HF%).

CONCLUSIONS

These results showed that spectral pattern in AMI patients had very low LF and HF power density. Decreased HRV in that group was mainly due to diminished parasympathetic influence in cardiac regulation; nevertheless ratio LF/HF was increased which represents an imbalance of sympatho-vagal activity with predominance of sympathetic tone. We found poor correlation between frequency domain indices and other risk variable; best correlation was between total spectral power and radionuclide ejection fraction (r = 0.642, p less than 0.01), which could express independent prognostic value in AMI patients risk stratification.