Biomedical subjects

P Rizzon

Publications and source records attributed to P Rizzon.

At least 73 records · Page 4Linked to original sources

PubMed1996

Syncopal sustained ventricular tachycardia in a patient with right ventricular dysplasia.

A 41-year-old man was hospitalized for syncopal sustained ventricular tachycardia with left bundle branch morphology. Diagnostic screening confirmed a right ventricular dysplasia: fibrofatty replacement of myocardium on endomyocardial biopsy and severe dilation of right ventricle with no left ventricular impairment was documented. His bundle recording showed an abnormally long HV interval, and programmed ventricular stimulation induced high-rate sustained ventricular tachycardia with left bundle branch block morphology associated with reduced systolic blood pressure and dizziness. Right ventricular burst pacing proved to be effective in restoring sinus rhythm. A single lead pectoral cardioverter-defibrillator was implanted and programmed for VVI and antitachycardia pacing, as first ventricular tachycardia therapeutic intervention. During 6-month follow-up, 1 asymptomatic ventricular tachycardia recurrence terminated by antitachycardia pacing was reported by the device. The possible role of the other therapeutic options such as drugs, ablation, and surgery for this specific case is also discussed.

Adult↗

PubMed1996

Analysis of microvascular integrity, contractile reserve, and myocardial viability after acute myocardial infarction by dobutamine echocardiography and myocardial contrast echocardiography.

The purpose of this study was to evaluate, in postinfarction dysfunctioning myocardium, the relative potential of myocardial contrast and low-dose dobutamine echocardiography in detecting myocardial viability, and the relation between microvascular integrity, contractile reserve, and functional recovery at follow-up. Twenty-four patients with recent myocardial infarction were studied before hospital discharge with low-dose dobutamine and myocardial contrast echocardiography. In the dysfunctioning infarct area, wall motion score index was calculated at baseline, during low-dose dobutamine, and at 3-month follow-up. Revascularization of the infarct-related artery was performed if clinically indicated. Eighteen patients (group A) had myocardial enhancement of the dysfunctioning infarct area at myocardial contrast echocardiography of >50%, whereas the remaining patients (group B) had an increase of < or = 50%. Wall motion score index was similar at baseline in groups A and B (2.6 +/- 0.4 and 2.8 +/- 0.2; p = NS), but it improved during low-dose dobutamine and at follow-up only in group A (1.9 +/- 0.9 and 1.9 +/- 0.7, respectively; p <0.001 vs baseline). In group B, wall motion score index was 2.7 +/- 0.4 with low-dose dobutamine and 2.8 +/- 0.2 at follow-up (p = NS vs rest). In identifying viable myocardial segments, myocardial contrast echo had 100% sensitivity and 46% specificity, whereas low-dose dobutamine echo had 71% sensitivity and 88% specificity. Thus, microvascular integrity after acute myocardial infarction is a fundamental prerequisite for ensuring myocardial contractile reserve and regional functional recovery. Myocardial contrast and low-dose dobutamine echocardiography have different, but complementary, diagnostic characteristics in detecting myocardial viability.

Aged↗

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

Improved Doppler detection of proximal left anterior descending coronary artery stenosis after intravenous injection of a lung-crossing contrast agent: a transesophageal Doppler echocardiographic study.

OBJECTIVE: This study was designed to verify the usefulness of transesophageal Doppler recording of blood flow velocity in the proximal left anterior descending coronary artery, after a peripheral injection of a lung-crossing contrast agent (SHU 508A), in detecting and locating a hemodynamically significant stenosis (vessel narrowing > or = 50%) affecting this portion of the vessel. BACKGROUND: Transesophageal Doppler echocardiography has a limited diagnostic impact on the evaluation of proximal left anterior descending coronary artery stenoses. Peripheral injection of SHU 508A, a lung-crossing contrast agent enhancing Doppler signal to noise ratio in coronary arteries, may allow recording of localized disturbed blood flow velocity at the stenosis site even in the absence of a clear B-mode visualization of the vessel. METHODS: Transesophageal Doppler echocardiography, before and after echo contrast injection, was performed in 31 patients who underwent coronary angiography. Using color Doppler as a guide, pulsed wave Doppler recording of blood flow velocity in the left anterior descending coronary artery was attempted to detect a localized increase in blood flow velocity. B-mode evaluation of the vessel was also performed. RESULTS: Angiography showed a significant proximal left anterior descending coronary artery stenosis in 16 patients (group 1) and no stenosis in 15 patients (group 2). In 15 of 16 group 1 patients, Doppler after contrast injection revealed a localized velocity increase of at least 50% of the reference value; mean (+/-SD) percent increase in velocity was 150 +/- 89% (range 367% to 0%). In group 2 Doppler after contrast injection revealed a mild localized increase in velocity in four patients and no increase in velocity in the remaining 11 patients; mean (+/-SD) percent increase in velocity was 5 +/- 7% (range 21% to 0%, p < 0.001 vs. percent increase in group 1). When a percent velocity increase > or = 50% of the reference value was considered a positive criterion for detecting significant stenosis, the sensitivity and specificity were 92% and 100% respectively. The sensitivity of the evaluation before contrast injection or considering B-mode imaging alone was much lower (25% and 19%, respectively, p < 0.001 vs. evaluation after contrast injection). In addition, color Doppler after contrast injection correctly located the stenosis along the vessel, as compared with angiography. CONCLUSIONS: Blood flow evaluation of the proximal left anterior descending coronary artery by transesophageal Doppler echocardiography after contrast injection is a feasible and reliable method for detecting and locating significant stenoses affecting this part of the vessel and is an improvement over the traditional ultrasound approach.

Aged↗

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

Myocardial contrast echocardiography in acute myocardial infarction. Pathophysiological background and clinical applications.

Myocardial contrast echocardiography is a technique used in experimental and clinical settings in order to visualize the pattern of intramyocardial perfusion. In the acute phase of myocardial infarction, regional absence of flow during myocardial contrast echocardiography delineates the area at risk of necrosis, while the definitive non-perfused area expresses infarct size. Reopening the infarct-related artery, which may be achieved spontaneously by thrombolysis or percutaneous transluminal coronary angioplasty, is not a reliable indicator of intramyocardial reperfusion. If myocardial ischaemia due to coronary occlusion has been sufficiently prolonged and severe, not only myocyte viability, but also microvascular integrity is lost. Myocardial contrast echocardiography, using intracoronary injection of sonicated contrast medium, gives information about microvascular integrity and the effective presence of intramyocardial reflow. Anatomical integrity of microvasculature does not necessarily imply preserved function, and thus the microvessel vasodilating reserve may also be impaired. Myocardial contrast echocardiography has the potential to assess alterations in microvascular function, showing, in the myocardial area with reduced coronary reserve, a relatively reduced increase in echocontrast signal intensity when an intravenous vasodilator agent is administered.

Animals↗

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↗

PubMed1996

Geometry of the carotid arteries and tilt-up hypotension in subjects with essential arterial hypertension.

Dysfunction of the baroreceptor structures located in the carotid bulb is considered responsible for hypotensive responses to orthostatic posture in hypertensive subjects. Because of a recurrent vascular impairment in essential hypertensives, the authors hypothesized that in these cases the baroreceptive dysfunction could be related to some peculiar vascular disarrangement of the carotid arteries, at the level of the bulb. To test this, they compared two groups of mild essential hypertensives, divided into group A--15 subjects considered hyporeacting because of a decrease in mean blood pressure > or = 10 mmHg at the first minute of a passive orthostatic stress--and group B--15 subjects considered normoreacting because of an increase in mean blood pressure > or = 5 mmHg. They evaluated by high definition echo Doppler ultrasonography: (1) an arterial compliance index, (2) the volume of the carotid bulb, and (3) a score expressing the degree of arteriopathy at the level of the carotid arteries. In group A, results demonstrated a significant impairment of the carotid artery structure, expressed by an increase in volume of the carotid bulb (389.4 +/- 134.7 vs 233.2 +/- 116.5 mm3, P < 0.05) and a higher vascular score (2.7 vs 1, P < 0.001), while the index of arterial compliance was similar in the two groups. In conclusion, in mild essential hypertension a baroreceptor dysfunction could be strictly linked to a derangement of the carotid artery structure, while arterial compliance does not seem to involve the baroreceptor function.

Adult↗

PubMed1996

[Medium-term clinical experience with automatic transvenous defibrillators implanted in the chest area without subcutaneous electrodes].

From March 1992 to April 1996 a pectoral biphasic transvenous implantable cardioverter defibrillator without subcutaneous leads was implanted in 35 patients with life threatening ventricular tachyarrhythmias. Mean age was 58 +/- 9 years; 23 patients had coronary artery disease, 10 non ischemic dilated cardiomyopathy and 2 arrhythmogenic right ventricular dysplasia. All were in NYHA functional class I and II and 4 in class III: mean ejection fraction was 35 +/- 12%. The mean duration of the implantation procedure was 85 +/- 35 min. The mean defibrillation threshold, measured in 23 active-CAN devices was 8.8 +/- 5 J. There were no operative complications except in one case of transient ischemic electromechanical dissociation. The mean hospital stay from the time of implant to predischarge evaluation was 6.2 +/- 2 days. The average follow-up period was 18.5 +/- 11 months. Two patients had non sudden and non arrhythmic cardiac death in the third and sixth month, respectively. In 19 patients 171 implantable cardioverter defibrillator interventions were reported: in 5 patients five inappropriate interventions were reported and in the remaining 14 were reported: 35 ventricular fibrillation and 131 ventricular tachycardia. The short duration of the procedure, brief hospitalization with very low perioperative morbidity, high efficacy and low mid-term complications give a new image to this therapeutic option.

Adult↗

PubMed1995

Efficacy and safety of d-sotalol, a pure class III antiarrhythmic compound, in patients with symptomatic complex ventricular ectopy. Results of a multicenter, randomized, double-blind, placebo-controlled dose-finding study. The d-Sotalol PVC Study Group.

BACKGROUND: There is increasing interest in pure class III antiarrhythmic compounds, ie, drugs in which the electrophysiological effect is confined to the propensity for producing an isolated lengthening of action potential duration. d-Sotalol represents the prototype of such pure class III agents. This double-blind, placebo-controlled, randomized dose-finding study evaluated the antiarrhythmic efficacy and safety of d-sotalol in patients with symptomatic chronic ventricular ectopy. METHODS AND RESULTS: A total of 233 patients presenting with > or = 30 premature ventricular contractions (PVCs) per hour during drug-free Holter monitoring randomly received placebo or d-sotalol at dosages of 50, 100, or 200 mg BID. Drug efficacy was assessed by repeat Holter monitoring at the end of double-blind therapy. There was a dose-dependent increase in QT and QTc duration, indicating class III activity. A dose-related decrease in hourly PVC counts was observed, reaching statistical significance for patients receiving 200 mg d-sotalol BID (311 PVCs/h during baseline compared with 135 PVCs/h during active treatment, P < .05). Analysis of the primary efficacy criterion (ie, > or = 75% reduction in total PVCs/h) revealed a significant treatment effect only for the highest d-sotalol dose, with 8 patients (14%) meeting this criterion. Eighteen patients reported side effects, which led to drug discontinuation in 5. One sudden death and one nonfatal cardiac arrest occurred in patients with dilative cardiomyopathy receiving 200 mg d-sotalol BID. No incidence of torsade de pointes was reported. CONCLUSIONS: d-Sotalol exerts dose-dependent class III activity in patients with symptomatic ventricular ectopy. Its PVC-suppressing activity is modest and becomes evident predominantly at dosages of 200 mg administered BID. The observation of drug-associated serious adverse arrhythmic events emphasizes the need for individualized careful dose titration, particularly in patients with advanced organic heart disease.

Adolescent↗

PubMed1995

Transient myocardial ischemia in patients with chronic angina: relation to heart rate changes and variability in exercise threshold. BAY r 1999 in Chronic Angina Study Group.

This study was undertaken to assess the relation of ambulatory myocardial ischemia to heart rate changes and variability in exercise threshold in patients with chronic angina. The study involved 118 patients with chronic angina and proven coronary artery disease who had a 'positive' exercise test result. All patients underwent a first exercise test followed by a 48-h period of ambulatory electrocardiographic monitoring. A second exercise test was performed 4 days later. A total of 101 ischemic episodes were recorded in 35 patients. The heart rate at the appearance of 1-mm ST segment depression during ambulatory electrocardiographic monitoring was > or = 20 beats/min lower than that during exercise testing in 58 ischemic episodes (57%, Group A), 10-19 beats/min lower in 26 (26%, Group B), and < or = 9 beats/min lower or higher in 17 (17%, Group C). Thirty-five percent of the Group A ischemic episodes, 69% of Group B, and 71% of Group C were preceded by an increase in heart rate of > or = 10 beats/min. Thirty patients showed a variable exercise threshold. The prevalence of Group A and B ischemic episodes was not significantly different in patients with fixed or variable exercise threshold, whereas that of Group C episodes was 22% in the former and 0% in the latter (P = 0.036). These results suggest that increased coronary tone may be one of the mechanisms contributing to modulate the occurrence of transient myocardial ischemia in most patients with chronic angina and transient myocardial ischemia at ambulatory electrocardiographic monitoring. This occurs regardless of whether the patients have a variable or fixed exercise threshold.

Analysis of Variance↗

PubMed1995

Effects of L-carnitine administration on left ventricular remodeling after acute anterior myocardial infarction: the L-Carnitine Ecocardiografia Digitalizzata Infarto Miocardico (CEDIM) Trial.

OBJECTIVES: This study was performed to evaluate the effects of L-carnitine administration on long-term left ventricular dilation in patients with acute anterior myocardial infarction. BACKGROUND: Carnitine is a physiologic compound that performs an essential role in myocardial energy production at the mitochondrial level. Myocardial carnitine deprivation occurs during ischemia, acute myocardial infarction and cardiac failure. Experimental studies have suggested that exogenous carnitine administration during these events has a beneficial effect on function. METHODS: The L-Carnitine Ecocardiografia Digitalizzata Infarto Miocardico (CEDIM) trial was a randomized, double-blind, placebo-controlled, multicenter trial in which 472 patients with a first acute myocardial infarction and high quality two-dimensional echocardiograms received either placebo (239 patients) or L-carnitine (233 patients) within 24 h of onset of chest pain. Placebo or L-carnitine was given at a dose of 9 g/day intravenously for the first 5 days and then 6 g/day orally for the next 12 months. Left ventricular volumes and ejection fraction were evaluated on admission, at discharge from hospital and at 3, 6 and 12 months after acute myocardial infarction. RESULTS: A significant attenuation of left ventricular dilation in the first year after acute myocardial infarction was observed in patients treated with L-carnitine compared with those receiving placebo. The percent increase in both end-diastolic and end-systolic volumes from admission to 3-, 6- and 12-month evaluation was significantly reduced in the L-carnitine group. No significant differences were observed in left ventricular ejection fraction changes over time in the two groups. Although not designed to demonstrate differences in clinical end points, the combined incidence of death and congestive heart failure after discharge was 14 (6%) in the L-carnitine treatment group versus 23 (9.6%) in the placebo group (p = NS). Incidence of ischemic events during follow-up was similar in the two groups of patients. CONCLUSIONS: L-Carnitine treatment initiated early after acute myocardial infarction and continued for 12 months can attenuate left ventricular dilation during the first year after an acute myocardial infarction, resulting in smaller left ventricular volumes at 3, 6 and 12 months after the emergent event.

Adult↗

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↗

PubMed1995

Transvenous defibrillator implantation in patients with persistent left superior vena cava and right superior vena cava atresia.

In this report a transvenous cardioverter defibrillator implantation is described in two patients with a persistent left-sided superior vena cava and right SVC atresia. In the first case, manoeuvring of the guide wire inserted through the left subclavian vein into the SVC proved impossible, revealing a left SVC originating from the left brachiocephalic vein with an acute corner. Changing the side of implantation and inserting a CPI Endotak catheter through the right subclavian vein, the lead was easily advanced through the left SVC into the coronary sinus and then into the right atrium with the tip abutting the lateral atrial wall. Subsequent manoeuvres allowed passage of the tip of the catheter into the right ventricular apex with the proximal defibrillation coil of the Endotak lead in the low left SVC, with its distal limit at the junction with the coronary sinus. A biphasic waveform single pathway RV - > left SVC successfully defibrillated with a stored energy of 5 J. In the second patient, implantation of a transvenous Medtronic system was possible from a left infraclavicular approach. A tripolar RV coil was inserted into the right ventricle via the persistent left SVC and contiguous coronary sinus. Because of the acute angle required to enter the RV in this second case, the RV lead was looped in the right atrium in order to enter the RV in a satisfactory, albeit atypical RV location. This patient was successfully defibrillated with a 5 J monophasic waveform delivered between the RV coil, a CS/left SVC coil, and a subcutaneous patch. In conclusion, both of these patients illustrate the ability to use transvenous ICDs successfully in patients with persistent left superior vena cava although the implantation technique deviates substantially from traditional methods.

Adolescent↗

PubMed1995