PubMed Health⌕ Search

Biomedical subjects

F Massari

Publications and source records attributed to F Massari.

At least 19 recordsLinked to original sources
PubMed1999

Diastolic dysfunction and baroreflex sensitivity in hypertension.

The determinants of diastolic dysfunction in patients with systemic hypertension are not completely known. To evaluate the possible role of age, arterial blood pressure, and baroreflex heart rate response impairment in causing diastolic dysfunction, we studied 61 patients (42 male; mean+/-SD age, 43.9+/-12 years) with newly recognized and therefore previously untreated systemic hypertension. Diastolic dysfunction was evaluated by means of Doppler echocardiography (and diagnosed as such when the early to atrial peak velocity ratio corrected to heart rate was <1), arterial blood pressure by 24-hour ambulatory monitoring, and baroreflex heart rate response by means of the spectral technique (alpha index) during paced (0.27 Hz) and spontaneous breathing (in a supine position and during tilt). Nineteen patients had diastolic dysfunction, the most powerful predictor of which was age (r=-0.63, P<0.001). The patients with diastolic dysfunction had significantly lower values for spectral baroreflex gain in the high-frequency band than those without (5.2+/-3 versus 8.4+/-5 ms/mm Hg during paced breathing, P<0.05; 7. 4+/-4 versus 13.3+/-7 ms/mm Hg in a supine position, P<0.05; 4.3+/-4 versus 5+/-2 ms/mm Hg during tilt, P<NS). Ambulatory blood pressure values were not significantly different in the patients with (137+/-14 and 89+/-9 mm Hg) and without (144+/-11 and 82+/-24 mm Hg) diastolic dysfunction. In conclusion, age and impaired baroreflex heart rate response (but not pressure overload) are determinants of left ventricular diastolic dysfunction in patients with newly recognized and untreated systemic hypertension.

Adult↗
PubMed1999

Respiratory systolic pressure variability during atrial fibrillation and sinus rhythm.

Previous studies have found that respiratory variations of ventricular response in atrial fibrillation are infrequent and inconsistent. This asynchrony between heart rate and respiration may characterize the physiological mechanisms coupling heart rate and systolic blood pressure oscillations in the respiratory band. The aim of this study was to evaluate whether synchronous variations in systolic blood pressure and respiration depend on a simultaneous change in heart rate. Univariate and bivariate spectral analyses were made of the R-R interval, systolic blood pressure, and respiratory signals during controlled respiration (16 breaths/min) in 24 patients with atrial fibrillation before and after efficacious electrical cardioversion and in 24 age- and sex-matched control subjects. During atrial fibrillation, the spectral coherence between respiration and heart rate was low (0.18+/-0.03), but there was a high level of coherence between respiration and systolic blood pressure (0.67+/-0.05). After cardioversion, the coherence between respiration and heart rate increased to 0.86+/-0.04, whereas the geometric mean values of the concomitant respiratory systolic blood pressure oscillations decreased by 72% (from 21.1 to 5.9 mm Hg(2), P<0.001), which was similar to that observed in the control group (5. 7 mm Hg(2)). These results confirm the inconsistent effect of respiration on heart rate response during atrial fibrillation and demonstrate that respiratory sinus arrhythmia is not a prerequisite for systolic blood pressure oscillations but may play an antioscillatory role in respiratory systolic blood pressure variability, which is probably mediated by arterial baroreflex mechanisms.

Adult↗
PubMed1998

Comparison between noninvasive indices of baroreceptor sensitivity and the phenylephrine method in post-myocardial infarction patients.

BACKGROUND: Depressed baroreflex sensitivity obtained by means of a phenylephrine test plays a prognostic role in patients with a previous myocardial infarction. Our purpose was to evaluate the correlation and agreement between the baroreflex sensitivity obtained with phenylephrine and that obtained by two noninvasive methods: the alpha-index and sequence analysis. METHODS AND RESULTS: The alpha-index was measured by means of the spectral analysis of RR and systolic blood pressure variabilities in both the high- and low-frequency bands; sequences were identified from simultaneously recorded time series in which the RR and systolic blood pressure concurrently increased or decreased. Noninvasive baroreflex sensitivity tests were performed during both spontaneous and controlled respiration. Fifty-two consecutive patients with recent myocardial infarction underwent the analyses. Although the correlations between phenylephrine and either of the noninvasive methods were always significant, those found during controlled respiration had the highest r values (r=.70). However, the limits of agreement calculated by means of the Bland and Altman method were wide for both noninvasive methods. CONCLUSIONS: The results obtained by means of noninvasive baroreflex sensitivity assessments should not be used in clinical practice as an alternative to those obtained by the phenylephrine method.

Adult↗
PubMed1998

Assessment of cardiac vagal activity in patients with hyperthyroidism.

Previous studies suggested that in patients with hyperthyroidism an autonomic imbalance and in particular a lower than normal vagal activity might be present. To verify this hypothesis we have evaluated the respiratory sinus arrhythmia (RSA, a measure of cardiac vagal activity) in ten hyperthyroid patients and in ten normal subjects. RSA was calculated from the power of the spectral component of the heart rate variability in high frequency band (HF-RR) during both spontaneous (supine and passive head-up tilt) and controlled breathing (supine). During controlled breathing the phase relation between heart rate and respiratory has been computed. The hyperthyroid patients showed a higher heart rate in all three conditions (P<0.001) and higher spontaneous respiratory rate in supine position (centered frequency of HF-RR: 0.342+/-0.015 vs 0.262+/-0.016 Hz; P<0.001). No difference was found in hyperthyroid patients compared to controls in terms of the HF-RR power in normalized units both during spontaneous breathing (supine, 43+/-8.3 vs 39.7+/-6.7%; tilt 18.8+/-5.9 vs 19.3 vs 4.1%; mean+/-SE) and controlled breathing (45.4+/-7.1 vs 48.9+/-6.9%). No difference was found also in terms of the phase relationship between the heart rate and the respiratory signals (77.5+/-32.3 vs 77.5+/-28.1, degrees). Hyperthyroid patients seem not to have an impaired cardiac vagal activity.

Adult↗
PubMed1998

Effect of respiratory rate on the relationships between RR interval and systolic blood pressure fluctuations: a frequency-dependent phenomenon.

OBJECTIVE: The aims of this study were to determine the relationships between oscillations in systolic blood pressure and heart period at different breathing frequencies and to investigate the role of sympathetic contribution to this relationship. METHODS: Fourteen healthy volunteers underwent three randomized periods of controlled breathing at 6, 10 and 16 breaths/min. ECG (RR), respiratory signal (RESP) and systolic blood pressure (SBP) were continuously recorded. The component of RR and SBP oscillations related to respiration (RRResp and SBPResp) was defined by means of uni- and bivariate spectral analysis. The squared coherence (K2) and phase between RR and RESP, and RR and SBP (RR-SBP) were also assessed. When the K2 of RR-SBP in the respiratory band was > 0.5, we considered the phase and calculated the closed-loop gain between the two signals. Seven subjects were also studied after chronic metoprolol treatment. RESULTS: Although the mean values of RR and SBP did not differ between the three periods of breathing, the higher the respiratory rate, the smaller the RRResp and SBPResp. The phase was always negative (SBPResp changes preceded RRResp changes), thus suggesting a baroreflex link. The higher the respiratory rate, the lower the gain and phase. Pharmacological beta-adrenoceptor blockade increased the gain and shifted the phase, but the relationships found at baseline between the respiratory rate and both the gain and phase remained unchanged. CONCLUSIONS: The effect of breath rate on the relationship between heart rate and systolic pressure variabilities is a frequency-dependent phenomenon that is also independent of the sympathetic drive.

Adrenergic beta-Antagonists↗
PubMed1998

Effects of hydrophilic and lipophilic beta-blockers on heart rate variability and baroreflex sensitivity in normal subjects.

To evaluate the effect of a hydrophilic and a lipophilic beta-blocker on the autonomic nervous system, 20 normal subjects were studied under baseline conditions and 7 days after being randomly assigned to metoprolol (200 mg/day), nadolol (80 mg/day), and placebo. Under each condition, the time-domain parameters were analyzed by means of 24-hour ECG monitoring and the frequency-domain parameters by means of the autoregressive method using 10-minute ECGs during rest, controlled respiration, and after a head-up tilt test. The alpha index (the gain in the relationship between the RR period and systolic arterial pressure variability) was also calculated. Both nadolol and metoprolol significantly increased all of the time-domain parameters except the standard deviation of the RH intervals; they also modified the frequency-domain parameters. Both blunted the significant reduction in the high frequency (HF) component and alpha index during tilt. In normal subjects, hydrophilic and lipophilic beta-blockers similarly modify the time- and frequency-domain parameters that are particularly evident when high sympathetic tone is present (during daytime and tilt). The value of the alpha index was increased by both beta-blockers in the HF, but not in the low frequency band; this difference might be due to the fact that the former is a measure of the vagal component of the baroreflex control and the latter a measure of the sympathetic component. The effects of hydrophilic and lipophilic beta-blockers on the time- and frequency-domain parameters of heart rate variability are similar.

Adrenergic beta-Antagonists↗
PubMed1998

Different trends of changes in heart rate variability in patients with anterior and inferior acute myocardial infarction.

Modifications in heart rate variability (HRV) parameters occur after acute myocardial infarction. The aim of this study was to evaluate the trend of HRV change during the acute phase and the first month after myocardial infarction, and establish whether they were affected by the anterior or inferior location of the infarction. The time-domain HRV measures of 59 patients with a first uncomplicated acute myocardial infarction were computed from 24-hour ECG recordings made on days 1, 2, 10, and 28 after hospital admission. At day 1, the mean RR cycle length (NN), the standard deviation of the NN intervals (SDNN), and the root mean square successive difference of NN intervals (RMSSD) were lower in the patients with anterior myocardial infarction. Although the parameters were similar in all of the patients at day 28, their behavior over time was different (P = 0.01): the SDNN in the patients with inferior myocardial infarction had decreased to the values found in anterior myocardial infarction patients by day 2 but, at day 10, both NN and SDNN tended to recover in both groups; RMSSD had diminished in both groups by day 2, but at day 10, had increased in the patients with anterior, but not in those with inferior myocardial infarction. These findings suggest that (1) in the very early phase of myocardial infarction, HRV is different in the two locations, (2) during the first hours of myocardial infarction patients with inferior location showed a greater vagal activity than patients with anterior location that became lower at day 10, and (3) the recovery of HRV is an early phenomenon in both groups, being already evident by the second week after myocardial infarction.

Case-Control Studies↗
PubMed1998

Beta-blocker effects on respiratory sinus arrhythmia and baroreflex gain in normal subjects.

STUDY OBJECTIVE: The results of studies on the effect of beta-adrenergic blockade on respiratory sinus arrhythmia (RSA) are discordant. The aim of this study was to verify whether chronic beta-adrenergic blockade is capable of increasing RSA, and therefore vagal outflow, and to analyze whether the mechanism of action is central or peripheral. PARTICIPANTS AND DESIGN: Twenty normal subjects (28+/-2 years old) were randomized to receive a hydrophilic (nadolol) beta-blocker, a lipophilic (metoprolol) beta-blocker, and placebo. MEASUREMENTS: After 1 week of therapy, a spectral analysis was made of the variability in heart rate and systolic BP during controlled breathing at 16 breaths/min. The high-frequency component was calculated for the RR interval (measure of RSA) and systolic pressure, and the squared coherence and phase functions were assessed between RR and systolic pressure fluctuations in the respiratory band; a negative phase means that RR changes follow systolic pressure changes. The gain in the relationship between the two signal fluctuations was also calculated. RESULTS: Both beta-blockers increased the mean (+/-SD) RR interval (placebo=808+/-21, nadolol=1,054+/-30, metoprolol=1,031+/-27 ms; p<0.0001), RSA (placebo=542, nadolol=1,177, metoprolol=1,316 ms2; p=0.002), and the gain (placebo=13.6+/-1.5, nadolol=21.9+/-2.8, metoprolol=24.5+/-3.6 ms/mm Hg; p<0.002), and both modified the phase function (placebo=-21.1+/-5.3, nadolol=-1.8+/-4.9, metoprolol=-2.9+/-4.2 degree; p<0.0001). No difference was found between nadolol and metoprolol. CONCLUSIONS: Chronic beta-adrenergic blockade enhanced both RSA and baroreflex gain and reduced the phase between the RR interval and systolic pressure oscillations. Since no difference was found between the hydrophilic and the lipophilic beta-blockers, these changes seem to be due to a peripheral effect.

Adrenergic beta-Antagonists↗
PubMed1998

[Double-blind randomized placebo-controlled study of the effects of slow release and immediate release forms of propafenone in patients ventricular extrasystole symptoms].

This is a multicenter, randomized, double-blind, placebo-controlled, cross-over and double-dummy study aimed at testing the efficacy and tolerability of two slow-release propafenone (Pr SR) preparations and compare them with the effect of instant release propafenone (Pr IR). The study was performed in 83 patients with frequent (> 30 premature ventricular contractions/hour) and stable (< 35% variability in two 24-hour ECG monitoring periods) symptomatic premature ventricular contractions. Patients were preliminarily studied in wash-out from antiarrhythmic drugs. After a period of placebo administration, all patients underwent three consecutive periods during which they received Pr IR at the dosage of 150 mg x 3, Pr SR at the dosage of 225 mg x 2, Pr SR at the dosage of 325 mg x 2. The periods lasted 10-14 days each and the sequence was randomly assigned. Twenty-four-hour ECG monitoring periods were obtained at the end of the placebo as well as at the last day of each treatment period. Treatment efficacy was evaluated by intention to treat analysis in 80 patients and by protocol in 61. Treatment was considered efficacious when premature ventricular contraction reduction > or = 75%, couplet reduction > or = 90% and non sustained ventricular tachycardias were completely suppressed. Pr IR 150 mg x 3 was efficacious in 42% of patients, Pr SR 325 mg x 2 in 45.9% and Pr SR 225 mg x 2 in 32%. Tolerability was considered good in the majority of patients. These results show that among the different types studied, Pr SR 325 mg x 2 should be considered the treatment of choice for premature ventricular contractions.

Adolescent↗
PubMed1997

Dependency of premature ventricular contractions on heart rate.

To identify a method for characterizing the dynamic behavior of ventricular arrhythmias at different heart rates, 201 consecutive patients with frequent premature ventricular contractions (PVCs) underwent two 24-hour electrocardiographic monitoring periods. The percentage of PVCs for each cycle length was calculated and then analyzed by linear regression analysis. On the basis of the significance of the p value, and the positive or negative value of the slope, we identified three trends: a tachycardia-enhanced pattern (p < 0.01, slope negative), a bradycardia-enhanced pattern (p < 0.01, slope positive), and an indifferent pattern (p > 0.01). During the first monitoring period, a tachycardia-enhanced pattern was present in 56 patients (28%), a bradycardia-enhanced pattern was present in 49 patients (24%), and an indifferent pattern was present in 96 patients (48%). This relationship was reproducible in 41 of the patients with a tachycardia-enhanced pattern (73%), in 29 of the patients with a bradycardia-enhanced pattern (59%), and in 70 patients with an indifferent pattern (72%). In conclusion, it is possible to identify a spontaneous trend between the incidence of ventricular arrhythmias and the length of the preceding cardiac cycle that seems to remain stable over time.

Adult↗
PubMed1997

Heart rate dependency of premature ventricular contractions. Correlation between electrocardiographic monitoring and exercise-related patterns.

AIMS: The identification of the response of ventricular arrhythmias to exercise testing could provide important information in the clinical setting but is difficult to obtain as no definite criteria are available. The aim of this study was to evaluate whether analysis of spontaneous heart rate dependency of premature ventricular contractions evaluated by means of 24 h electrocardiographic monitoring is capable of predicting their behaviour during exercise. METHODS AND RESULTS: One hundred and twenty-six patients (49 +/- 16 years) with frequent (> 30 h) premature ventricular contractions underwent 24 h electrocardiographic monitoring in order to evaluate the relationship between arrhythmias and heart rate, and an exercise test in order to evaluate the behaviour of the arrhythmias. On the basis of the incidence of premature ventricular contractions at different cardiac cycle lengths found at electrocardiographic monitoring, three groups of patients were identified: 34 with a tachycardia-enhanced pattern (the shorter the cycle length the higher the incidence of arrhythmias); 32 with a bradycardia-enhanced pattern (the longer the cycle length the higher the incidence of arrhythmias); and 60 patients with an indifferent pattern (no relationship). During the exercise test, the number of premature ventricular contractions/min at maximal effort in comparison with baseline increased in patients with a tachycardia-enhanced pattern (couplets or runs appeared in 10), decreased in those with a bradycardia-enhanced pattern and did not change in those with an indifferent pattern. The positive predictive accuracy of the tachycardia-enhanced pattern in predicting an increase in premature ventricular contractions > 100% at maximal effort was 78%. CONCLUSION: Identification of spontaneous behaviour between the incidence of premature ventricular contractions and the length of the preceding cardiac cycle may predict the behaviour of arrhythmias during exercise.

Adolescent↗
PubMed1997

[The effects of chronic beta-blocker administration on respiratory sinus arrhythmia].

The results of studies on the effect of beta-adrenergic blockade on respiratory sinus arrhythmia (RSA) are discordant. In some studies in which an increased RSA was reported, central vagotonic activity has been proposed. The aim of this study was to verify whether chronic beta-adrenergic blockade is capable of increasing RSA, and therefore vagal outflow, and to analyze whether the mechanism of action is central or peripheral. Twenty normal subjects (mean age 28 +/- 2 years) were randomized to receive a hydrophilic (nadolol, N), a lipophilic (metoprolol, M) beta-blocker and placebo (PL). After 1 week of therapy a spectral analysis was made of the variability in heart rate and systolic blood pressure (SBP) while they controlled their breathing at 16 breaths/min for a period of 5 min. The high frequency component was calculated for the RR interval (HF-RR, RSA measure) and SBP (HF-SBP), and the squared coherence (K2) and phase functions (phi HF) were assessed between RR and SBP fluctuations in the respiratory band (RR-SBP); a negative phi HF means that RR changes follow SBP changes. The alpha HF (an index of the baroreflex gain) was also calculated. Both beta-blockers increased the mean RR interval (PL 808 +/- 21, N 1054 +/- 30, M 1031 +/- 27 ms; p < 0.0001), HF-RR (PL 6.3 +/- 0.3, N 7.1 +/- 0.3, M 7.2 +/- 0.3 ln-ms2; p = 0.002) and alpha HF (PL 13.6 +/- 1.5, N 21.9 +/- 2.8, M 24.5 +/- 3.6 ms/mmHg; p < 0.002), and both modified phi HF (PL -0.23 +/- 0.05, N -0.02 +/- 0.05, M -0.03 +/- 0.04 s; p < 0.0001). No difference was found between N and M. Chronic beta-adrenergic blockade enhanced RSA and baroreflex gain and reduced the phase between the RR interval and SBP oscillations. Since no difference was found between the hydrophilic and the lipophilic beta-blockers, these changes seem to be due to a peripheral effect.

Administration, Oral↗
PubMed1996

Effects of nadolol and its combination with atrial pacing on rate-enhanced ventricular premature complexes.

To explore the role of heart rate in the genesis of ventricular premature complexes whose incidence increases when the length of the preceding cardiac cycle decreases, we analyzed the effect of nadolol alone and together with atrial pacing in 4 patients. Nadolol lengthened the RR cycle and suppressed ventricular premature complexes; atrial pacing, restoring the baseline RR cycle lengths, led to the reappearance of ventricular premature complexes, suggesting the major role of heart rate.

Adult↗
PubMed1996

Short- and long-term reproducibility of time and frequency domain heart rate variability measurements in normal subjects.

OBJECTIVE: To obtain data relating to the reproducibility of the time and frequency domain measurements obtained from 10-min ECG recordings. METHODS: Eighteen normal volunteers underwent evaluations of time and frequency domain heart rate variability 2 weeks and 7 months after baseline analysis. The time domain parameters were mean NN, the standard deviation of NN intervals, the percentage of successive NN intervals > 50 ms and the root mean square successive difference of NN intervals. The frequency domain evaluations (total power, low frequency, and high frequency) were made by means of both the Fast Fourier Transform algorithm (FFT) and the autoregressive method (AR) from 10-min ECG recordings made under three different conditions: rest, controlled respiration, and after a passive head-up tilt test. Reproducibility was evaluated by means of the interclass correlation coefficient (ICC), comparing baseline values with the results obtained at the second week and the seventh month. Time domain evaluation were also made from 10-min ECG. RESULTS: All of the time domain measurements had an ICC > or = 0.75, except for the standard deviation of NN intervals, which had an ICC of 0.57. The frequency domain parameters obtained by means of either FFT or AR showed similar reproducibility. Low frequency was reproducible under all three conditions, total power only at rest, and high frequency only during controlled respiration. CONCLUSION: The reproducibility of frequency domain parameters depends on the analysed condition. These results are of primary importance when the effects of drugs or other interventions on heart rate variability are under investigation.

Adult↗
PubMed1996

Holter-guided identification of premature ventricular contractions susceptible to suppression by beta-blockers.

To evaluate whether the identification of the different types of relations between premature ventricular contractions (PVCs) and the preceding sinus cycle length is capable of predicting the effect of beta-blockers on the PVCs themselves, 55 patients (43 men, 12 women, mean age 52.6 +/- 15.6 years) with different cardiac diseases, and >30 PVCs/hr characterized by stability and the same relation at two Holter monitoring periods were studied. The relation was tachycardia enhanced (the shorter the preceding cycle length, the higher the incidence of PVCs) in 23 patients (group 1); indifferent (no correlation between the preceding cycle length and PVC incidence) in 21 (group 2); and bradycardia enhanced (the longer the preceding cycle length, the higher the incidence of PVCs) in 11 (group 3). A third Holter monitoring was performed 6 days after nadolol administration (80 mg/day) to evaluate its effect on the three types of PVCs. Incidence in all patients (-88;p<0.001). In group 2, it caused a reduction in the majority of patients (-60%;p<0.05) but an increase in five. In group 3, it caused a reduction in only half of the patients (-45%) and a 91% increase in the remainder. The difference in the effect of nadolol in the three groups was highly significant (X2=27.5;p<0.0001). The relation between the incidence of PVCs and the preceding cycle length is a useful means of identifying subsets of patients with PVCs who will benefit from beta-blockers.

Adrenergic beta-Antagonists↗
PubMed1996

Sleep suppression of ventricular arrhythmias: a predictor of beta-blocker efficacy.

It has been reported that the frequency of premature ventricular contractions in some patients tend to decrease during the hours of sleep when modifications in autonomic tone and bradycardia occur. The aim of this study was to evaluate whether the phenomenon of sleep suppression may be a sensitive and specific parameter for predicting the antiarrhythmic effect of beta-blockers on premature ventricular contractions. The presence of sleep suppression was evaluated in 45 patients (mean age 50 +/- 17 years) with frequent premature ventricular contractions at two baseline Holter recordings. Sleep suppression was defined as > 50% reduction in the number of nighttime as opposed to day-time premature ventricular contractions. Three groups of patients were identified: those with sleep suppression at both Holter recordings (group 1); those with sleep suppression at only one Holter recording (group 2); and those without sleep suppression at either Holter recording (group 3). A third Holter was performed 5 days after nadolol administration. In group 1, nadolol led to a mean reduction in the number of premature ventricular contractions of 90% (> 70% in 21/23 patients). In group 2, the mean reduction was 76% (> 70% in three out of six patients). In group 3, there was a mean increase in the number of premature ventricular contractions of 33%. The positive predictive accuracy of sleep suppression in relation to the antiarrhythmic efficacy of nadolol is very high (88%) when sleep suppression is present during two baseline Holter recordings. Sleep suppression is a sensitive parameter for identifying the premature ventricular contractions likely to benefit from beta-blocker administration.

Adolescent↗
PubMed1995

The effect of nadolol on heart rate and the standard deviation of the RR intervals.

The aim of this study was to evaluate the effect of nadolol in modifying the standard deviation of RR intervals (SDRR) and the coefficient of variance (CV) in 47 patients characterized by symptomatic, frequent (> 30 h-1) and reproducible premature ventricular contractions (PVCs). Sixteen patients had suffered a previous myocardial infarction (Group 1), 22 had various non-ischaemic cardiac diseases (Group 2) and nine had no heart disease (Group 3). All patients underwent two 24 h Holter recordings during the washout period, and a third Holter recording was taken 5 days after the administration of nadolol (80 mg.day-1). The RR cycle length (RR), SDRR and CV were evaluated for each 24 h period, as well as for six daytime (1000-1600h) and six night-time hours (0000-0600h). In all three groups, nadolol was highly effective in lengthening RR. However, the effect on SDRR was different in the three groups; 24-h SDRR tended to be reduced in all three groups (but the reduction was significant only in Group 1) due to a certain RR homogeneity. On the other hand, daytime SDRR tended to increase (but the increase was significant only in Group 3). CV is concomitantly affected by heart rate and SDRR, therefore it may be more sensitive in evaluating the effect of beta-blockers. The reduction in CV post-nadolol means that the bradycardia-induced effect is associated with an inadequate increase, or even a reduction in SDRR, whereas the absence of any CV changes (found only in Group 3) is the result of a concomitant increase in both RR cycle length and SDRR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗