Biomedical subjects
Publications and source records attributed to A Lagi.
The time-domain analysis of 24-hour electrocardiographic recordings showed that vagal modulation of heart rate is reduced within 48 hours from vasovagal syncope. However, patients with recent vasovagal syncope can be differentiated from healthy subjects only up to the age of 40 years with this analysis, because this parasympathetic modulation physiologically decreases with increasing age.
The autonomic nervous system has an important role in the pathophysiology of vasovagal syncope. The purpose of this investigation was to evaluate to what extent the autonomic system is involved in the mechanism of fainting and to characterize the profile of heart rate variability of individuals who are prone to undergo a critical event. Thirty patients (mean age 41 years) with vasovagal syncope and 15 comparable controls were monitored by 24-h electrocardiography. Heart rate variability was analysed over the whole 24 h and during the daytime and night-time using time domain parameters (average of heart periods, RR; standard deviation of heart periods, SDNN; standard deviation of the average of RR intervals over all the 5-min segments of the entire recording, SDANN; percentage of the total number of all RR intervals of pairs of adjacent RR intervals differing more than 50 ms over the entire recording, pNN50; the square root of the sum of the square of differences between adjacent RR intervals, rMSSD), as indicated by the Task Force for Clinical Use of Standard Measurements of Heart Rate Variability. These parameters explore the influence of the autonomic nervous system on sinus node function and provide information about the vagal control to the heart. Among these parameters, pNN50 and rMSSD were significantly reduced in individuals with vasovagal syncope when compared with controls, over each time period considered. The two parameters are related to high-frequency oscillations in the frequency domain and to the vagal influence of the heart. These results indicate that the vagal tone to the heart is altered in subjects who suffer from vasovagal syncope. The results of this study provide an insight into the pathophysiological mechanism of fainting and may offer another means of evaluating patients with syncope.
BACKGROUND/AIMS: Patients with cirrhosis and ascites usually show alterations of systemic hemodynamics and are thus prone to develop arterial hypotension, which might result in cerebral hypoperfusion if cerebral autoregulation is impaired. METHODS: We evaluated cerebral autoregulation in 15 patients with cirrhosis and ascites and 15 healthy subjects by monitoring mean blood flow velocity in the middle cerebral artery and arterial pressure during supine rest and passive tilting. RESULTS: Tilt provoked a drop of arterial pressure in both groups. Control subjects had a prompt recovery of mean flow velocity and a progressive recovery of arterial pressure, so that, after 120 s, both parameters had returned to baseline: at 20 s the recovery of flow velocity was faster (p<0.01) than that of blood pressure. By contrast, patients with cirrhosis had a delayed and incomplete recovery of both parameters (p<0.01 vs healthy subjects). In eight patients, the recovery of mean flow velocity paralleled that of arterial pressure, indicating an impaired cerebral autoregulation. These patients had a worse liver function, a higher cardiac index and lower peripheral resistance. CONCLUSIONS: Cerebral autoregulation is often impaired in patients with cirrhosis and ascites. These patients can develop cerebral hypoperfusion if arterial pressure falls abruptly.
BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) monitoring of mean blood flow velocity (mV) during head-upright tilt can allow testing of cerebral autoregulation. Nonetheless, head-upright tilt can induce changes in the ventilation-perfusion relationship and/or respiratory activity that might influence TCD data. METHODS: Forty-eight healthy volunteers underwent monitoring of mV and end-tidal CO2 in the horizontal position and during head-upright tilt. RESULTS: Both mV and end-tidal CO2 significantly decreased in orthostasis (P < .01). Linear regression analysis showed a significant linkage between end-tidal CO2 and mV changes (r = .83, P < .01). CONCLUSIONS: Changes in ventilation-perfusion ratio and in the respiratory pattern induced by head-upright tilt can significantly influence TCD data by determining a PCO2 decrease.
The pathogenetic role of autonomic nervous system in the neurally mediated orthostatic vasodepressive syncope is unclear. upright tilt was used to assess the characteristics of autonomic tone during orthostatic stress. We studied 18 patients (mean age 26 +/- 5 years) suffering from vasodepressive orthostatic syncope and with positive response to a 30-minute 60 degrees upright tilt and a comparable control group with a negative response to the upright tilt test. Blood pressure and heart rate (RR Interval) were measured beat-by-beat; ECG, systolic (SAP) and diastolic arterial pressure (DAP) and respiration trace were recorded for spectral analysis. The most important result of the work is a different pattern of the parameters evaluated, between fainters and controls, in the last period of tilt test, just before the syncope, and in the fainters group between the first (at the beginning) and the last period (just before syncope) of tilting. Baseline heart rate, arterial pressure and spectral indices were similar and increased with tilting in both groups (Low Frequency: LF; High Frequency: HF; LF/HF ratio). Just before the syncope, we observed in fainters group a decrease of heart rate, blood pressure, LF-RR, LF-DAP, LF-SAP, LF/HF -RR, and an increase of HF-RR and of total power where compared to in the same subjects in the first period of tilt and in front of controls in the same period of tilt. The novel aspect of the work, regarding the autonomic control of heart rate and arterial pressure, expressed by spectral fluctuations and by haemodinamic parameters, is consistent with a reduced sympathetic reserve in the immediate pre-syncopal period.
The autonomic regulation of cardiovascular function was evaluated in 15 cirrhotic patients with ascites and in 13 healthy subjects by the autoregressive power spectral analysis (PSA) of the intervals between adjacent R waves of the electrocardiogram (RR) interval and arterial pressure variability. Total power, low frequency (LF; index of the sympathetic activity of the heart and circulation), and high frequency (HF; index of vagal tone to the heart) components of the RR interval, systolic, and diastolic arterial pressure were evaluated in the supine position and during passive tilting, together with plasma norepinephrine levels. In the supine position, no significant differences in the PSA data were observed between the control subjects and cirrhotic patients, who had higher plasma norepinephrine levels. In healthy subjects, tilting was associated with an increase in the LF of the RR interval and arterial pressure and a decrease in the HF of the RR interval. In contrast, patients with cirrhosis showed a decrease of both LF and HF. Consequently, the LF/HF ratio significantly increased in healthy subjects, whereas it was unchanged in cirrhotic patients. The LF component of the diastolic pressure also decreased during tilting in cirrhotic patients. Plasma norepinephrine increased after tilting in both groups. These results indicate that the autonomic response to passive tilting is impaired in cirrhotic patients with ascites at both the cardiac and vascular levels, as a result of an altered sympatho-vagal balance, with reduced sympathetic predominance. These alterations occurred despite an appropriate response to the tilting of plasma norepinephrine, pointing to a receptorial or postreceptorial site of the autonomic impairment.
The arterial baroreflex was studied in subjects who had recently had an episode of vasodepressor syncope. This was determined using 2-3 mcg/kg intravenous boluses of phenylephrine and assessing the bradycardic response. The values were measured in ms/mmHg and expressed as the angular coefficient of the regression line between the increase in R-R interval on the electrocardiograph and the systolic arterial pressure. In subjects examined immediately after the vasodepressor syncope episode the bradycardic response was much more marked than in controls (p < 0.01) and in the subjects themselves 6 months after the episode, provided that they were symptom-free (p < 0.01). It is concluded that in vasodepressor syncope there is a phase in which the baroreflex is highly sensitive and that this is due not to a lowering of the stimulation threshold but to a gain in the efferent arc, which explains a 'vagotonic' response.
Power spectrum analysis of the R-R interval was used in 20 controls and in two groups of type I (insulin dependent) diabetics (27 patients) to detect changes in total power or in its components (low frequency and high frequency) that might be considered an early evidence of impairment of cardiac autonomic nervous system control. A significant difference between controls and severe diabetics (with autonomic involvement) was found in all components. In the early stage of diabetes without evidence of autonomic involvement, an absolute reduction of the low frequency component in the standing position and a significant reduction of the percentage increase compared with the lying position, was found to discriminate diabetics from controls. The occurrence of somatic neuropathy was unrelated to changes in autonomic function. These data indicate that: (1) power spectrum analysis is sensitive enough to detect cardiac autonomic neuropathy in diabetics, where standard methods fail; (2) power spectrum analysis is the method of choice in the early stages; (3) in severe type I dependent diabetes there is a reduction of power spectrum analysis total power and a defective response to standing up; (4) cardiac autonomic neuropathy develops independently from somatic neuropathy.
BACKGROUND AND PURPOSE: Transcranial Doppler measurements of blood flow velocity permit an assessment of variations in intracranial hemodynamics in response to acute arterial pressure variations. The purpose of this study was to scan healthy volunteers and patients with autonomic failure for differences in cerebral hemodynamic patterns under an acute hypotensive stimulus. METHODS: We used transcranial Doppler monitoring of blood flow velocity in the middle cerebral artery and noninvasive monitoring of arterial blood pressure and heart rate before, during, and after acute arterial hypotension induced by reactive hyperemia of the lower limbs. RESULTS: After maximum hypotension, the mean blood flow velocity was higher in the healthy volunteers than in the patients. In the healthy subjects mean velocity rose significantly (P < .01) higher than arterial blood pressure after 30 seconds and 60 seconds; in the patients mean velocity and arterial pressure moved in parallel fashion. The diastolic blood flow velocity increased more in the control group than in the patients during the early stages of the test; furthermore, only in the healthy volunteers did it increase significantly more than arterial pressure after 30 seconds and 60 seconds. Regarding the pulsatility index, the differences between the two groups were similar to the diastolic velocity results. CONCLUSIONS: (1) Monitoring of mean blood flow velocity showed the ability to maintain an adequate cerebral blood flow in healthy subjects; this mechanism was not efficient in the patients with autonomic failure. (2) Diastolic velocity and pulsatility index values clearly showed that only in healthy subjects were cerebral hemodynamics relatively independent of pressure values.
The proliferative activity was evaluated in colorectal biopsies of 39 healthy subjects living in two distinct geographical areas, Trieste in northern and Florence in central Italy. Subjects living in Trieste had a significantly higher mitotic activity compared with subjects living in Florence (mitoses/cells counted x 100 were 0.17 +/- 0.04 in Trieste and 0.089 +/- 0.02 in Florence). The results of a dietary questionnaire also showed that subjects in Trieste consumed significantly fewer starches, fibers, nitrites, and proteins. However, no correlation was evident between the consumption of these nutrients and intestinal proliferation.
A twenty-four-hour blood pressure (BP) monitoring was performed in 20 normotensive and 20 hypertensive subjects, matched by sex and age. Blood pressure and heart rate (HR) variability were evaluated both as absolute and percent standard deviation. In agreement with the literature no significant difference in HR and BP variability was observed between the two groups. The linear regression between HR and BP values was evaluated in both groups. The authors observed a significant difference in the relationship between these two cardiovascular variables between the two groups. In the hypertensive group the cardiovascular control of HR and BP showed a different relationship than in normotensive subjects, suggesting a different neurovegetative modulation.
159 patients with a previous discharge diagnosis of recurrent vasodepressor syncope associated with prolonged standing or other circumstance known to trigger the condition were examined in order to isolate the orthostatic form. 72 patients with a history of at least two episodes of loss of consciousness after standing still for at least 10' were selected for testing by head-up tilt. Those who showed signs or symptoms during the test were tested a further twice, the third time after atropine administration. This process resulted in the diagnosis of orthostatic vasodepressor syncope in 28 patients who presented both 1) a positive test associated with hypotension and bradycardia and 2) bradycardia-free hypotention on repetition of the test with atropine.
The variation of SBP, DBP and HR is evaluated on tilting in a group of 34 patients affected by orthostatic hypotension versus a group of 54 healthy subjects, age and sex cross-matched. The patients affected by cardiovascular autonomic failure showed: 1) a fall of SBP greater than -19 mmHg in the 1st min; 2) a fall of the SBP average value (for 10 minutes) greater than -22 mmHg. Contrarily, the healthy subjects showed: 1) no variations of SBP values during the 1st minute and 2) a growing of SBP between the 2nd and the 10th minute; 3) a SBP average value (for 10 minutes) with a positive trend. The DBP and HR showed not differences between the groups. We suggest that the measure of SBP on standing may be considered an easy and fast method to perform a diagnosis of autonomic cardiovascular failure.
This case report describes a 40-years-old man affected by fracture of leg and pulmonary embolism. Two-dimensional echocardiography showed a large right atrial migrant thromboembolus prolapsing into tricuspid valve during diastole. The patient was treated with rt-PA through right atrial venous catheter and underwent to serial echocardiographic examinations. The rt-PA determined the dissolution of the thrombo-embolus at the 2nd hour of infusion. It is concluded that early two-dimensional echocardiography might be a very helpful technique to diagnose and follow-up therapy of pulmonary embolism.
Our aim was to assess the incidence and clinical characteristics of carotid sinus hypersensitivity in a group of subjects suffering from syncope. The total number of patients was 118. Twenty-four of them (20%) were diagnosed as epileptics (first attack) and 38 (32%) as vasodepressors. 56 patients with unexplained syncope underwent carotid sinus massage during electrocardiographic registration and pressure monitoring. 41 patients were found to have carotid sinus hypersensitivity. 34 of these 41 patients received implantation of a pacemaker. Abnormal sinus node function was noted in 30, abnormal atrioventricular node function in 3 and combined abnormal sinus node and AV node function in 1. Furthermore three other patients who were negative to massage were implanted with a pacemaker because they had an organic heart disease and recurrent syncope. Different tests as 24-hour monitoring ecg and electrophysiologic study showed no better results in the diagnosis of syncope. Our data demonstrates the diagnostic importance of carotid sinus massage in the diagnosis of syncope. The validity of this method is confirmed by the 24 month follow-up.
The 24-hour blood pressure (BP) average value in normotensive and hypertensive subjects is not defined. In 329 subjects three occasional blood pressure data were measured. The same day a non invasive 24-hour blood pressure monitoring was performed. The average of the occasional blood pressure and the average of the 24-hour blood pressure data were compared. In many cases the occasional blood pressure average was not strictly linked with the 24-hour blood pressure average. A statistical procedure (K-Means Cluster Analysis) was performed separately on occasional blood pressure values and on the hourly blood pressure average of the whole day. By this method three clusters of subjects were selected to evaluate the occasional and the 24-hour blood pressure cluster's cutoffs. The cluster's blood pressure cutoffs evaluated on occasional blood pressure values were not dissimilar from the blood pressure values suggested by literature for normotensive, borderline and hypertensive groups. The K-Means Clusters Analysis seems an interesting statistical method to research the subsets in a population evaluated by 24-hour blood pressure monitoring. We suggest that the 24-hour BP cutoffs evaluated in the three cluster groups may be considered as indicative for a clinical diagnosis of normotensive, borderline and hypertensive state.
Exercise hypertension is the blood pressure response to dynamic exercise stress which is considered excessive as compared to what is normally observed in a healthy population. It is a useful indicator to assist in detecting those persons who may develop sustained hypertension. Research has been conducted on a large number of patients, carefully selected using as criteria: arterial pressure, presence of other diseases and age. The examination has been conducted by observing the stressor test on the cycloergometer and annotating the Pa with the traditional method. The data was then analyzed using statistical methods. We conclude that at the moment of maximum effort the patients can be divided into two groups based upon PaD values superior or inferior to 20% of base values or to 95 mmHg. Those who exceed these values (43% of all patients studied) are considered as effort hypertensive subjects. The work's originality derives from the statistically proven consideration that the evaluation of PaD at the 8th minute of the test with cardiac rate between 70 and 90% of the maximum theoretical cardiac rate is predictive of effort hypertension. Hence continuation of the test can be avoided with advantages in terms of time and reduction of the generic risks inherent in carrying out a maximal test. Follow up on the patients is in progress.
In this work the authors propose the Valsalva maneuver as a diagnostic test in a group of patients shown, by anamnestic, physical, and instrumental criteria, to be affected by vasodepressor syncope. They studied the response of heart rate and baseline arterial pressure to the maneuver performed in passive orthostasis in 7 healthy volunteers and 24 patients. These patients showed a hypotensive response and a time of recovery to the initial values that was significantly longer than in the control group (p less than 0.01). The authors conclude that studying the response to the Valsalva maneuver can be useful in the diagnosis of vasodepressor syncope.