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Biomedical subjects

P Rizzon

Publications and source records attributed to P Rizzon.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1998

Radiofrequency catheter ablation of atrio-ventricular accessory pathways.

Radiofrequency catheter ablation of accessory pathways may represent the treatment of choice for patients with symptomatic atrio-ventricular reentrant tachycardia or atrial fibrillation and a high ventricular response through the accessory pathways with short antegrade refractory period. Moreover, catheter ablation has contributed towards understanding anatomical and electrophysiological characteristics of accessory pathways. As far as anatomical characteristics accessory pathways may be classified into fibers with proximal insertion in right or left atrium and fibers with proximal insertion in the atrio-ventricular nodal junction. As far as electrophysiological properties are concerned, accessory pathways may be differentiated into non-decremental and decremental. In non-decremental by-pass tracts (the so-called Kent bundles) the impulse can be conducted antegradely, retrogradely and in both directions. Decremental accessory pathways generally show only antegrade conduction properties (the so-called Mahaim fibers) and can be classified in long and short pathways; in particular, catheter ablation has given considerable evidence that the vast majority (but not all) of them has a proximal insertion on the tricuspid anulus (atrio-ventricular pathways) or on the atrio-ventricular node (nodo-ventricular pathways). Decremental accessory pathways with only retrograde conduction properties are involved in the so called "Permanent Junctional Reciprocating Reentrant Tachycardia".

Atrial Fibrillation↗
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

Multiplane transesophageal echocardiography to detect effectiveness of selective pulmonary recombinant tissue-type plasminogen activator thrombolysis in pulmonary embolism and patent foramen ovale.

A functionally patent foramen ovale can create a relevant right-to-left shunt during massive pulmonary embolism. This associated feature, although maintaining adequate cardiac output, may explain both the paradoxic embolism and the uneffectiveness of peripherally administered drugs. This case demonstrates the potential of transesophageal echocardiography in monitoring the hemodynamic findings of such patients and, consequently, the effectiveness of thrombolytic treatment.

Echocardiography, Transesophageal↗
PubMed1997

Lisinopril in the treatment of congestive heart failure in elderly patients: comparison versus captopril.

The present study was performed in order to compare the efficacy, safety, and tolerability of lisinopril, a long-acting angiotensin-converting enzyme (ACE) inhibitor, with captopril, the shorter acting ACE inhibitor available, in the treatment of elderly patients (mean age 70 +/- 0.5 years) with congestive heart failure (mean left ventricular ejection fraction 33.5 +/- 1%). The study was organized according to a double-blind, parallel-group, randomized multicenter protocol. After a 14-day placebo run-in period, patients were randomized to receive either lisinopril 5 mg orally once per day or captopril 12.5 mg orally once per day. The dose of the study drug could be doubled at 2-week intervals for 6 weeks. The maximal dose was lisinopril 20 mg once per day or captopril 25 mg twice per day. The addition of either captopril or lisinopril to a regimen of diuretics caused a significant increase in exercise tolerance assessed by bicycle ergometry after 12 weeks of treatment (530 +/- 21 seconds vs. 431 +/- 13 seconds, p < 0.01; 555 +/- 19 seconds vs. 463 +/- 12 seconds, p < 0.01, respectively). Both drugs significantly increased left ventricular ejection fraction and stroke volume, were equally effective in improving NYHA class, and were well tolerated, with no differences detectable between treatments. The results of this study indicate that lisinopril 5-20 mg once daily is at least as effective and well tolerated as captopril 12.5-50 mg daily in the treatment of elderly patients with congestive heart failure.

Aged↗
PubMed1997

Effects of atrial pacing stress test on ultrasonic integrated backscatter cyclic variations in normal subjects and in patients with coronary artery disease.

AIMS: To evaluate the effects of acute, atrial pacing-induced, reversible myocardial ischaemia on myocardial thickening and integrated backscatter cyclic variations in patients with or without coronary artery disease. METHODS AND RESULTS: Thirty-six patients with suspected coronary artery disease underwent transoesophageal echocardiography with simultaneous atrial pacing, and coronary angiography. In myocardial segments not related to a significantly narrowed coronary artery, both from patients with and without coronary artery disease, thickening and integrated backscatter cyclic variations were not reduced at peak pacing. In segments related to a significantly narrowed coronary artery, thickening decreased at peak pacing, was still reduced at pacing interruption and recovered at 2 min, while backscatter cyclic variations, blunted at peak pacing, immediately recovered after pacing interruption. CONCLUSION: During stress-induced myocardial ischaemia, backscatter cyclic variations are blunted and thickening reduced. Returning to baseline, pre-atrial pacing values occur more rapidly in backscatter cyclic variations than when thickening takes place. Evaluation of stress-induced alterations in backscatter cyclic variations may aid in the identification of ischaemia-induced regional left ventricular functional impairment and, hence, in coronary artery disease diagnosis.

Atrial Function↗
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

Functional role of microvascular integrity in patients with infarct-related artery patency after acute myocardial infarction.

AIMS: The study was set up to evaluate the functional role of post-infarct preserved microvascular integrity. Low dose dobutamine echocardiography and myocardial contrast echocardiography were used to study patients before hospital discharge who had suffered a recent myocardial infarction and had a patent infarct-related artery (TIMI flow grade 3). METHOD: In the dysfunctioning infarct area, the wall motion score index was calculated at baseline, during the dobutamine infusion and at the 3 month follow-up echocardiogram; contrast echocardiography was performed at the time of coronary angiography, before hospital discharge. RESULTS: In patients with more than 50% of the dysfunctioning infarct area opacified at contrast echocardiography (group A), regional wall motion score index decreased, compared to baseline, during the dobutamine infusion (1.97 +/- 0.78 vs 2.5 +/- 0.35 at baseline; P < 0.001) and at follow-up echocardiography (1.83 +/- 0.63 vs 2.5 +/- 0.35 at baseline; P < 0.001). In patients with less extensive microvascular integrity as revealed by contrast echocardiography (group B), regional wall motion score index did not decrease from baseline during either the dobutamine infusion (2.73 +/- 0.21 vs 2.81 +/- 0.20 at baseline; P = ns), or at follow-up (2.81 +/- 0.20 vs 2.81 +/- 0.20 at baseline; P = ns). CONCLUSION: In patients with post-infarct dysfunctioning myocardium but a patent infarct-related artery, microvascular integrity, as assessed by myocardial contrast echocardiography, is an indicator of myocardial viability in terms of preserved contractile reserve, as demonstrated by dobutamine infusion and functional recovery at follow-up.

Cardiotonic Agents↗
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↗
PubMed1997

[Diagnosis of coronary disease using multiplane transesophageal echocardiography and atrial pacing].

The diagnostic value of echo-pacing has been previously report. Recently, monoplanar transesophageal echocardiography (TEE) has been used to improve the reliability of this stress procedure. Therefore, in 40 consecutive patients undergoing coronary angiography for suspected coronary artery disease (CAD) we tested the accuracy of atrial pacing (TAP) during multiplane TEE as a stress procedure. TAP was performed during TEE using a circular, adhesive electrode installed at the tip of the echoscope and connected to the pulse generator. In all patients TAP was firstly attempted by positioning the TEE probe in the esophagus and, if not successful, in the stomach. Left ventricular wall motion was monitored by means of 4, 2 chamber and long axis views from the esophagus and short axis scan from the stomach, in baseline conditions, at peak pacing and immediately after maximal heart rate. The test was considered positive if wall motion abnormalities developed during TAP. Stable capture of the atrium was obtained in 28 patients from the esophagus and in 6 patients from the stomach. Thus, TEE-TAP was performed in 34/40 patients (feasibility 85%). Wall motion abnormalities were detected during TAP in 20/24 with and in 2/10 patients without CAD. Thus, sensitivity and specificity of TEE-TAP were 83% and 80% respectively. The sensitivity of the test in single and multivessel disease resulted 72% and 92%. The 12 lead electrocardiogram during TAP showed a sensitivity of 66% and a specificity of 40% (p < 0.01 vs TEE-TAP). In conclusion, TEE-TAP is a new approach for CAD evaluation providing a complete and accurate imaging of left ventricular wall motion.

Cardiac Pacing, Artificial↗
PubMed1997

[Value of peak oxygen consumption during exercise for the prognostic stratification of patients with severe systolic dysfunction of the left ventricle].

We sought to assess the prognostic value of peak exercise oxygen consumption (peak VO2) in patients with severe left ventricular systolic dysfunction and mild to moderate symptoms of chronic heart failure. We focused on 1-year mortality. We prospectively studied 77 patients with left ventricular ejection fraction (EF) < or = 25% and NYHA functional class I/II (61%) or III (39%). All patients underwent cardiopulmonary exercise test, two-dimensional echocardiography and 24-hour Holter monitoring. Examined variables were age, etiology, NYHA functional class, EF, peak VO2, and presence of nonsustained ventricular tachycardia. Overall 1-year mortality rate was 23%. At univariate analysis, age > or = 60 years, ischemic etiology, and peak VO2 < 14 ml/kg/min were significantly associated with mortality. At multivariate analysis, peak VO2 was the most powerful predictor of death (p = 0.0001). In the subgroup of patients with a peak VO2 < 14 ml/kg/min, the actuarial 1-year mortality rate was 56%. One additional patient underwent heart transplantation because of severe hemodynamic deterioration. By contrast, in the subgroup of patient with a peak VO2 > 14 ml/kg/min, 1-year mortality rate was 11%. This study provides evidence that patients with severe left ventricular dysfunction and mild to moderate symptoms of chronic heart failure can be accurately stratified into subgroups with strikingly divergent prognosis by an objective criteria such as peak VO2.

Analysis of Variance↗
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↗