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Biomedical subjects

P Rizzon

Publications and source records attributed to P Rizzon.

At least 127 records · Page 7Linked to original sources
PubMed1991

Transesophageal versus intracardiac atrial stimulation in assessing anterograde conduction properties of the accessory pathway in Wolff-Parkinson-White syndrome.

Electrophysiologic intracardiac and noninvasive transesophageal testing, used to evaluate parameters of anterograde conduction across the accessory pathway, the refractory period and shortest atrial cycle length with 1:1 conduction over the pathway, were compared to assess the reliability of the noninvasive technique in identifying patients with Wolff-Parkinson-White syndrome, at risk of rapid ventricular response during atrial fibrillation when this arrhythmia is not inducible. Sixteen patients with Wolff-Parkinson-White syndrome were submitted both to invasive and transesophageal atrial stimulation. We evaluated both the functional and effective refractory periods of the accessory pathway, using the same drive cycle length, and the shortest cycle length with 1:1 atrioventricular conduction over the accessory pathway. There were no differences between the parameters obtained by intracardiac atrial stimulation and by transesophageal atrial stimulation. The two approaches correlated well: mean functional refractory periods of the accessory pathway were 285 +/- 42 msec and 289 +/- 32 msec, respectively (NS, r = 0.88); mean effective refractory periods of the accessory pathway were 267 +/- 41 msec and 271 +/- 32 msec, respectively (NS, r = 0.89); mean shortest cycle lengths with 1:1 conduction over the accessory pathway were 255 +/- 48 msec and 255 +/- 44 msec, respectively (NS, r = 0.94). These data demonstrate the reliability of transesophageal atrial stimulation in estimating the parameters for anterograde conduction across an accessory pathway. These results, and the already documented ability of transesophageal atrial stimulation to induce atrial fibrillation, suggest this noninvasive technique should be taken as a first approach in screening patients with Wolff-Parkinson-White syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Echo-Doppler evaluation of the effects of heart rate increments on left atrial pump function in normal human subjects.

It is commonly believed that the atrial contribution to left ventricular filling increases during heart rate increments. However, the relative contribution of the pump function (atrial systole) and of the passive role (diastasis and reservoir) of the atrium to end-diastolic left ventricular filling is not well known. In order to investigate this problem, we performed a two-dimensional echo-Doppler study during right atrial pacing. Transmitral flow velocity curves were obtained by means of pulsed Doppler. Pacing was performed (1) at the lowest heart rate at which it was possible to obtain a stable capture of the atria, (2) at the heart rate at which the early and late Doppler filling waves almost completely overlapped. In both stages pacing was interrupted for a few seconds to obtain some post-pacing beats. Doppler tracing recorded at rest, during pacing and in the immediate post-pacing beats were analysed to obtain well-known parameters of atrial contribution; atrial peak flow velocity, early to atrial peak flow velocity ratio, and time-velocity integral of the atrial wave. Furthermore, in order to distinguish end-diastolic passive flow from the active contribution of atrial systole to filling, we superimposed the envelope of the last Doppler curve obtained during atrial pacing over the envelope of the first post-pacing curve. In this way the area of the atrial wave of the paced beat was divided by the mid-diastolic part of the post-pacing one into two areas, the integrals of which correspond to the active and passive atrial contribution respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Electrocardiographic patterns during Holter monitoring in patients with first and second degree A-V block due to 'dual A-V nodal pathways'.

The electrocardiographic patterns, observed during 24-h Holter monitoring, of 10 patients (mean age 35 +/- 22 years) with first and second degree A-V block due to dual A-V nodal pathways are reported. Recordings were selected according to the presence of: sudden and persistent prolongation of the PR interval: sudden normalization of the PR interval: 'atypical' Wenckebach sequences showing sudden and pronounced prolongation of any PR interval prior to the blocked P wave. Besides the already recognized pattern, new aspects were identified: (1) Wenckebach sequences in the slow and fast pathways characterized by a progressive increase in the PR interval until a blocked P wave occurred during long and short PR interval periods, respectively; (2) Wenckebach periods first in the slow and then in the fast pathway; (3) 2:1 A-V block with a normal PR interval in the conducted beat after a Wenckebach sequence in the slow pathway; (4) Wenckebach in the fast pathway and, subsequently, in the slow one characterized by a slight prolongation of the PR interval for some beats followed by a sudden and pronounced increase in the PR interval of one beat and a subsequent progressive slight PR prolongation until a blocked P wave occurred; (5) Wenckebach sequence in the fast pathway with subsequent conduction over the slow pathway without a blocked P wave; (6) blocked P waves during both long and short PR interval periods with slight prolongation of the preceding PR interval. The electrophysiological mechanisms involved in these electrocardiographic patterns together with the nature (anatomical or functional) of the intranodal pathways and the clinical significance of this type of block are discussed.

Adolescent↗
PubMed1991

Patterns of atrioventricular conduction during postexercise recovery in patients with atrial fibrillation and Wolff-Parkinson-White syndrome.

The effects of the postexercise recovery phase on the functional anterograde conduction properties of the accessory pathway (AP) were evaluated. Twenty-nine patients with Wolff-Parkinson-White (WPW) syndrome were submitted to supine maximal bicycle exercise testing. In seven patients (group I), in whom sustained atrial fibrillation (AF) could be induced by transesophageal pacing (TP), mean ventricular rate (MVR), the shortest R-R interval (SRR) between preexcited beats, and the observed percentage of preexcited beats were evaluated at rest, after each step of exercise and 2 minutes after the end of exercise. In 22 patients (group II), in whom sustained AF could not be induced, decremental TP was performed to evaluate the shortest atrial cycle length (SCL) with 1:1 conduction over AP at rest, after each step of exercise, and 2 minutes after the end of exercise. In four patients in group I, the protocol was repeated with atropine injected during the last minute of exercise. In 12 patients (three from group I and nine from group II), catecholamine plasma levels were measured at rest, at peak exercise, and during recovery. MVR was 144 +/- 20 beats/min at rest, 186 +/- 21 beats/min at peak exercise (P less than 0.001 vs rest), and 179 +/- 21 beats/min during recovery (P less than 0.001 vs rest; P less than 0.05 vs peak exercise). SRR was 289 +/- 73 msec at rest, 223 +/- 25 msec at peak exercise (P less than 0.05 vs rest), and 227 +/- 29 msec during recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Transesophageal Doppler echocardiography evaluation of coronary blood flow velocity in baseline conditions and during dipyridamole-induced coronary vasodilation.

Transesophageal echocardiography allows the evaluation of proximal coronary artery anatomy and coronary blood flow velocity (CBFV). To assess the potential of transesophageal echocardiography in evaluating CBFV and its variations induced by coronary-active drugs, we studied 15 patients by high-quality pulsed wave Doppler recordings of CBFV. In these patients, transesophageal Doppler evaluation of CBFV was performed before, 2 minutes after cessation of dipyridamole infusion (0.56 mg/kg in 4 minutes), and 2 minutes after aminophylline infusion (240 mg injected 4 minutes after cessation of dipyridamole infusion). The following CBFV parameters were evaluated at each of the three steps of the study protocol: maximal and mean diastolic velocities and maximal and mean systolic velocities. Furthermore, the following indexes of coronary flow reserve were evaluated: the ratio between maximal diastolic velocity recorded after and before dipyridamole administration and the ratio between mean diastolic velocity recorded after and before dipyridamole administration. Nine of the 15 patients had a normal left anterior descending coronary artery (group A), whereas the remaining six had significant (less than or equal to 75%) stenosis (group B). In group A patients, all CBFV parameters increased significantly during dipyridamole infusion and returned to near baseline values after aminophylline infusion. In group B patients, on the other hand, none of the CBFV parameters increased after dipyridamole infusion. Dipyridamole/baseline maximal diastolic velocity and mean diastolic velocity ratios were, respectively, 3.22 +/- 0.96 and 3.04 +/- 0.88 in group A and 1.46 +/- 0.45 (p less than 0.01 versus group A) and 1.48 +/- 0.49 (p less than 0.01 versus group A) in group B patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1991

Evaluation of pentisomide on stable ventricular premature beats. Comparison with placebo.

Pentisomide, a new class I anti-arrhythmic drug, was compared to placebo in 50 hospitalized patients with frequent (greater than 30 h-1) and stable ventricular premature beats (VPB) (variation less than 50% between two preliminary and one placebo 24-h Holter recordings). All patients underwent a single-dose acute oral testing followed by a short-term testing with 300 mg t.i.d. for 4 days and then by a 4-day placebo period. For the studied population, a 56.4% reduction of simple VPB and a 98.8% decrease of couplets and runs were the minimum required to define the drug efficacy and to exclude spontaneous variability, using the linear regression analysis. Pentisomide was found effective in 27 (54%) of the 50 patients after the acute test and in 23 (46%) after the short-term test. The drug induced a mild increase of PR and QRS intervals, while QTc, heart rate, blood pressure and ejection fraction showed no significant variations. Subjective tolerability was excellent.

Adult↗
PubMed1991

Ticlopidine treatment for patients with unstable angina at rest. A further analysis of the study of ticlopidine in unstable angina. Studio della Ticlopidina nell'Angina Instabile Group.

Data collected to investigate the effects of ticlopidine in a subset of 489 patients with angina at rest accompanied by transient ischaemic electrocardiographic changes have been analysed. Of the 489 patients, 255 received conventional treatment including beta-blockers, nitrates, or calcium antagonists (control group); 234 received conventional treatment plus ticlopidine 250 mg b.i.d. (ticlopidine group). The predefined end-points were vascular death and acute myocardial infarction (AMI). The incidence of end-points was assessed according to the intention-to-treat principle. The post-hoc estimated statistical power was 80%. The rate of death or AMI in the 6-month follow-up period was reduced from 14.9 to 6.8% (-54.4%) (odds ratio: 0.42; confidence intervals: 0.22, 0.80). The incidence of fatal or nonfatal AMI was reduced from 12.2 to 4.3% (-65%) (odds ratio: 0.32; confidence intervals: 0.14, 0.70) and of nonfatal AMI from 10.2 to 3.8% (-63%) (odds ratio: 0.35; confidence intervals: 0.15, 0.80). Nineteen patients died; 12 in the control group (4.7%) and seven in the ticlopidine group (83%) (-36%) (odds ratio: 0.62; confidence intervals: 0.21, 1.74); five patients in the control group and only one in the ticlopidine group died of an AMI. The post-hoc estimated statistical power was 80%. However, we cannot draw definitive conclusions about the clinical effect of ticlopidine treatment in the patients with angina at rest accompanied by transient ischaemic electrocardiographic changes because the subgroup analysis was not planned a priori. Nevertheless, this report strongly suggests that such patients can benefit from antiplatelet treatment with ticlopidine; the benefit mainly depends on the protective effect against myocardial infarction.

Aged↗
PubMed1991

Efficacy and duration of the effect of gallopamil sustained release in patients with chronic stable effort angina.

This double-blind, placebo-controlled, cross-over study was designed to evaluate the effects and duration of action of gallopamil sustained release (SR) in patients with stable effort angina. Exercise tests were performed 3, 8, and 12 hours after the last administration of placebo or gallopamil SR. Blood samples for plasma gallopamil concentration were taken just before each exercise test. Statistical analysis was performed using an analysis of variance for multiple comparisons with evaluation of interaction between sequence and period according to a cross-over design. Compared to placebo, gallopamil SR significantly prolonged exercise time from 412 +/- 100 to 481 +/- 71 s (p less than 0.02; 17%), from 416 +/- 88 to 484 +/- 67 s (p less than 0.01; 16%), and from 364 +/- 88 to 440 +/- 85 s (p less than 0.02; 21%) at 3, 8 and 12 hours respectively after administration. Time to -1 mm ST segment depression was also significantly prolonged from 263 +/- 56 to 336 +/- 76 s (p less than 0.001; 28%), from 262 +/- 81 to 356 +/- 70 s (p less than 0.001; 36%), from 231 +/- 65 to 291 +/- 76 s (p less than 0.001; 26%), respectively. No significant relationship between plasma levels and anti-ischemic activity was observed. In conclusion, our data show that gallopamil slow-release is effective in improving exercise tolerance of patients with chronic angina and that its therapeutic effect persists, substantially unchanged, up to 12 hours after administration.

Aged↗
PubMed1991

[Localization of the accessory pathways using surface ECG in Wolff-Parkinson-White syndrome].

During recent years criteria for localization of bypass tracts in the Wolff-Parkinson-White syndrome from the conventional ECG have been acquired utilizing epicardial and endocardial mapping data. The polarity of delta wave and QRS in the frontal and horizontal plane and the morphology of retrograde P waves during orthodromic reciprocating tachycardia, are the most indicative elements. An accurate analysis of QRS complexes during atrial fibrillation confirms the site of pre-excitation and could suggest the presence of 2 or more accessory pathways with sufficient spatial separation. Some criteria for identifying multiple accessory pathways are discussed.

Atrial Fibrillation↗
PubMed1991

[Transesophageal study in the diagnostic evaluation of pre-excitation].

Electrophysiologic non-invasive transesophageal testing is compared to intracardiac study in the management of patients with Wolff-Parkinson-White (WPW) syndrome. Transesophageal study can be reliably used to identify the participation of the accessory pathway in reciprocating supraventricular tachycardia and to determine the anterograde conduction properties of the accessory pathway. Using the shortest pre-excited interval during induced atrial fibrillation, or programmed and continuous atrial transesophageal stimulation can markedly reduce the need of intracardiac evaluation. The greater safety and economy of transesophageal compared to the intracardiac technique justify its wider use in preliminary screening of all WPW patients, unless ablative treatment has been clinically indicated, and in evaluating long-term drug protection against a potential deleterious ventricular response during atrial tachyarrhythmias.

Cardiac Pacing, Artificial↗
PubMed1991

[The vascular aging process: the potentials of intravascular echography].

Intravascular ultrasonography is a new diagnostic technique, based on the utilization of very small ultrasonic transducers, with high emission frequency (20-30 MHz) that can be introduced in cardiac cavities as well as in arterial vessels. Because of its technological characteristics this technique has a great potential for the evaluation of the morphological and functional alterations usually involving the arterial wall as a consequence of ageing. Intimal thickening, medial intimalization, reduced systolic-diastolic excursion of the vessel walls affected by ageing as well as by arterial diseases can be easily identified.

Aging↗
PubMed1991

[Invasive hemodynamic assessment and interventional therapy].

Cardiovascular diseases are the main reason for hospitalization and usually followed by a conservative therapeutic approach. Due to the improvement over the last few years in the results of surgery in the elderly, the number of hemodynamic studies has increased. Hemodynamic studies are generally performed in elderly patients with symptomatic valvular heart disease and acute myocardial infarction with complications. The incidence of complications in the elderly during catheterization and coronarography is higher than in younger but still low. Cardiovascular hemodynamics in the elderly is determined by a combination of lifestyle, the presence of cardiac diseases that increase in prevalence with advancing age (e.g., coronary artery disease) and age-related changes in cardiovascular hemodynamic per se. With age, the tunica media of major blood vessels stiffens. This produces a elevation of systolic blood pressure (afterload) in many elderly patients which in turn increases left ventricular (LV) wall stress and results in mild compensatory LV hypertrophy. This compensatory hypertrophy normalizes wall stress, but produces pertubations in diastolic function such as: a reduction in the rate of both diastolic and LV peak filling, a diminished diastolic compliance associated with LV hypertrophy and a greater dependence upon left atrial contraction to maintain cardiac output. Recently the proportion of these patients who have percutaneous transluminal coronary angioplasty (PTCA) is growing. PTCA can be performed with a high rate of clinical success. Complete revascularization is low, particularly in patients with trivessel disease. The most common reasons for incomplete revascularization were: vessels with chronic total occlusion and vessels with diffuse disease. The rate of major cardiac complications was high among patients at high-risk in the presence of trivessel disease and low left ejection fraction. Long-term results were encouraging. For 90% of patients who had clinical success after PTCA, the end results continued to be beneficial. In conclusion, PTCA is a valid therapeutic alternative in elderly patients with coronary artery disease. In subsets of patients with single and bivessel disease, the short- and long-term outcome is very favourable. In patients with triple vessel disease, early clinical success rate is low but the long-term success rate is, however, acceptable.

Aged↗
PubMed1991

[The role of metabolic therapy in myocardial infarct].

During acute myocardial ischemia the metabolism of free fatty acids is impaired. Since the rate of beta-oxidation is reduced, the levels of acil-CoA and long-chain acyl-carnitine increase. The activity of carnitine, which permits the transport of fatty acids into the mitochondria, is reduced both by its transformation in acyl-carnitine and by its release from the cells induced by acute ischemia. The accumulation of fatty acids induces a deterioration of hemodynamic parameters and some impulse formation and conduction disturbances. Since in experimental studies L-carnitine prevents the occurrence of hemodynamic and arrhythmic complications, clinical studies with this compound have been performed during acute ischemia in man. In patients with acute myocardial infarction high doses of L-carnitine induce: a statistically significant increase in urinary concentrations of long- and short-chain carnitine esters; a statistically significant reduction of ventricular arrhythmias during the second day after the onset of symptoms; a reduction of the necrotic area as assessed by electrocardiographic and enzymatic methods.

Adenosine Triphosphate↗
PubMed1991

[Blood acceleration is the principal factor in coronary flow increase during exercise test].

Continuous wave Doppler evaluation of the blood flow velocity in the internal mammary artery anastomosed to the left anterior descending coronary artery is a technique for assessing human coronary flow that shows a good reproducibility and lower change in Doppler angle between resting and supine exercise conditions. In this study the reciprocal changes which occur in coronary blood flow, coronary stroke volume, coronary resistance and blood pressure have been studied. During supine exercise coronary stroke volume remains constant and the increase of blood cells acceleration is necessary to have the shortening of cardiac cycle. This parameter is inversely dependent on the coronary resistances and directly dependent on blood pressure. As a consequence it plays the main role in increasing coronary blood flow during exercise.

Adult↗
PubMed1990

Doppler continuous-wave analysis of grafted mammary artery as a non-invasive technique for static and dynamic assessment of coronary flow in man.

In this paper, Doppler continuous-wave analysis of blood velocity in the internal mammary artery, anastomosed to the left coronary vascular bed in humans who have undergone myocardial revascularization, is proposed as a non-invasive technique to study coronary blood flow during physiological procedures which cause it to change. Blood velocity curves obtained in normal and anastomosed internal mammary arteries were compared during hyperventilation and the Valsalva manoeuvre. During hyperventilation, blood velocity increased in the normal mammary but not in the anastomosed artery. During the expiratory effort of the Valsalva manoeuvre, the mean blood velocity decreased in the normal mammary artery but it did not change significantly in the anastomosed artery. Variations in the mean velocity were largely prevented by simultaneous and well-balanced increases and decreases in the diastolic and systolic velocities, respectively.

Anastomosis, Surgical↗
PubMed1990

Prediction of cardiac events after uncomplicated myocardial infarction by cross-sectional echocardiography during transesophageal atrial pacing.

Atrial pacing can safely be utilized shortly after myocardial infarction. To evaluate the prognostic value of wall motion abnormalities induced by such pacing 83 consecutive patients with recent uncomplicated myocardial infarction underwent transthoracic cross-sectional echocardiography during transesophageal atrial pacing and upright bicycle exercise stress test. Patients were followed-up for 14 +/- 5 months. During the atrial pacing and the echocardiography, patients were defined at high risk if abnormalities of wall motion were detected in left ventricular regions remote from the infarcted area. Then, during the exercise stress test, high risk patients were those with ST segment depression greater than or equal to 1 mm. On the other hand, patients were considered to be at low risk if they had no abnormalities of wall motion during atrial pacing in remote regions or, in the case of the stress test, if they did not develop ST depression greater than or equal to 1 mm. Of the 83 patients, 21 had major cardiac events during the period of follow-up. Cardiac events occurred in 15/23 (65%) and 5/60 (8%, P less than 0.001) patients assigned to the groups adjudged to be at high and low risk, respectively, on the basis of echocardiographic results. Exercise testing was less reliable in identifying patients at risk of future cardiac events. Major events occurred in only 6 of the 19 patients with a positive stress test (32%, P less than 0.05 vs positive stress echocardiography) and in 14 of the 64 patients with a negative exercise stress test (22%, P = NS vs positive exercise stress test, P less than 0.05 vs negative atrial pacing echocardiography).

Cardiac Pacing, Artificial↗