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Biomedical subjects

L De Ambroggi

Publications and source records attributed to L De Ambroggi.

At least 19 recordsLinked to original sources
PubMed1991

Dispersion of ventricular repolarization in the long QT syndrome.

To identify markers of dispersion of the ventricular repolarization in the idiopathic long QT syndrome, body surface potential maps were analyzed in 40 such patients (mean age +/- standard deviation 21 +/- 11 years) and in 30 healthy control subjects (mean age 24 +/- 7 years). In each subject, 117 chest leads were recorded and maps of the integral values of the QRST interval were calculated. A multipolar distribution of the values, a marker of gross electrical inequalities of repolarization, was found only in 4 patients. To detect minor regional disparities of ventricular recovery, all the ST-T waveforms were analyzed in each subject. The ST-T waves were represented by a discrete series of potential values. The "similarity index" was computed by applying a principal component analysis, which represents (in percent) to what extent 1 fundamental pattern of ST-T reproduces all the recorded waveforms. The mean value of the similarity index was significantly lower in patients with long QT syndrome than in control subjects (49 +/- 10 vs 77 +/- 8%, p less than 0.0001). A value less than 61% (corresponding to 2 standard deviations below the mean value for controls) was found in 35 of 40 patients and in only 1 control subject (sensitivity 87%, specificity 96%). Thus, the similarity index is a more sensitive marker than the multipolar distribution of QRST integral maps in revealing electrical disparities of the ventricular recovery times.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1990

Early 24-hour blood pressure elevation in normotensive subjects with parental hypertension.

Subjects with a family history of parental hypertension are reported to have a slightly higher office blood pressure in the prehypertensive stage. Whether this reflects a hyperreactivity to blood pressure measurement or a more permanent blood pressure elevation, however, is not known. In the present study, blood pressure was measured in 15 normotensive subjects whose parents are both hypertensive (FH++), 15 normotensive subjects with one hypertensive parent (FH(+)-), and 15 normotensive subjects whose parents are not hypertensive (FH--); among the three groups, subjects were matched for age, sex, and body mass index. The measurements were made in the office during a variety of laboratory stressors and during a prolonged resting period, and for a 24-hour period (ambulatory blood pressure monitoring). Office blood pressure was higher in the FH++ group than in the FH-- group (p less than 0.05). The pressor responses to laboratory stressors were similar in the two groups, but the FH++ group had higher prolonged resting and 24-hour blood pressure than the FH-- group; the difference was always significant (p less than 0.05) for systolic blood pressure. The FH++ group also had a greater left ventricular mass index (on echocardiographic examination) than the FH-- group (p less than 0.01). The blood pressure values and echocardiographic values of the FH(+)- group tended to be between those of the other two groups. Thus, the higher blood pressure shown by individuals in the prehypertensive stage with a family history of parental hypertension does not reflect a hyperreactivity to stress but an early permanent blood pressure elevation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1988

Diagnostic value of body surface potential mapping in old anterior non-Q myocardial infarction.

Body surface potential maps (BSM) were recorded from 140 chest leads in 30 healthy control subjects (C) and in 20 patients who had had an acute non-Q wave myocardial infarction (MI) 1-82 months before the study, to identify reliable indices of necrosis. In 12 MI patients the QRS complex was within normal limits on standard 12-lead ECG (group A), and in 8 patients no pathologic Q waves were present but the R waves were small and did not normally increase from V1 to V4 (group B). In each subject instantaneous potential distributions throughout the QRS interval were examined. Moreover, the potential--time integrals relating to three intervals (first 40 msec, mid-third, and last third of QRS) were calculated at each lead point and displayed as integral (I) maps. For each time interval, deviation index maps (DI), indicating the standardized differences from normal values, were calculated. An area where the integral values differed at least 2 SD from normal mean was considered abnormal. In most group A patients the inspection of instantaneous potential maps did not reveal definitively abnormal patterns. In group B patients a greater variety of patterns was found and in four cases the characteristic features of the anterior Q wave MI were observed. The DI maps of the first 40 msec of QRS provided the best diagnostic accuracy: areas of negative values 2 SD lower than normal were present in all group B patients (100%), in 8 group A patients (67%), and in 4 group C subjects (13%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Effects of chronic administration of the fixed combination slow-release oxprenolol-chlorthalidone on left ventricular hypertrophy in hypertensive patients. Echocardiographic study.

To evaluate the effects of the chronic administration of the fixed combination slow-release, oxprenolol 160 mg and chlorthalidone 20 mg on left ventricular hypertrophy, ten hypertensive out-patients, with left ventricular hypertrophy documented by left ventricular mass index (LVMI) greater than 130 g/m2, were studied. After a two-week placebo period, patients were given the study medication, once daily for six months. Blood pressure and heart rate were measured, 24 h after-dosing, at the end of placebo and thereafter every month. A m-mode echocardiographic examination was performed at the end of the placebo period, after 1 month of active treatment and at the end of the study. In comparison with placebo, the study medication induced a significant reduction (p less than 0.01) of systolic and diastolic blood pressure, 24 h after dosing, after 1 month of treatment (from 181.0 +/- 18.5/108.5 +/- 12.0 to 146.5 +/- 10.8/94.0 +/- 7.7 mmHg), and this reduction was maintained until the end of the study (142.0 +/- 14.0/90.0 +/- 8.2 mmHg). At the 6th month and in comparison with placebo, a significant (p less than 0.01) reduction of left ventricular mass (LVM) and of LVMI was observed (LVM: from 295.9 +/- 113.8 to 221.5 +/- 66.1 g; LVMI: from 158.1 +/- 39.0 to 126.2 +/- 35.8 g/m2. In conclusion, our results confirm the good antihypertensive efficacy of the fixed combination slow-release oxprenolol and chlorthalidone and show that the study medication is able to induce a regression of left ventricular hypertrophy, in hypertensive patients.

Adult↗
PubMed1987

[The Italian Group for the Study of Streptokinase in Myocardial Infarct: Changes in surface cardiac potentials. Study with chest electromaps].

The electrocardiographic changes during and after the thrombolytic treatment with streptokinase (SK) were assessed by means of body surface potential mapping. The aim of the study was to identify potential patterns suggesting reperfusion and revealing possible short-term effects on the infarct size of the recanalization. We studied 23 patients enrolled in the G.I.S.S.I. trial; 11 had an anterior and 12 had an inferior myocardial infarction; 14 were treated with SK and 9 were controls. Body surface maps were recorded from 105 lead points located on the anterior thoracic surface using an automated instrument. The maps were obtained immediately before the SK infusion (or at the time of randomization in the control patients), 30, 60, 120 minutes thereafter and then 24 hours and 7 days after the onset of the infarct symptoms. In each patient the surface potential distribution at 100 msec after the end of QRS was considered and the sum of all the positive potential values was calculated (sigma ST). In addition, the potential time integrals relating to two intervals of the cardiac cycle (first 100 msec of ST and first 40 msec of QRS) were calculated at each lead point and transferred to diagrams representing the chest surface explored (isointegral map). With respect to Q-40 maps, deviation index maps were calculated as follows: the mean Q-40 map (obtained from 30 normal subjects) was subtracted from the map of each patient; the value obtained at each lead point was then divided by the standard deviation of the normal values for that point. An area where the integral values were at least 2 SD lower than normal was considered a reliable index of infarct. By considering as index of reperfusion an early peak of CPK (less than 12 hours from the onset of infarct symptoms), we divided the patients into 2 subsets: reperfused (R) and not reperfused (NR). The mean values of sigma ST at 100 msec progressively decreased in all patients from the baseline to the subsequent recordings in both control and SK groups, without significant differences; nevertheless, the highest percent reductions of sigma ST were observed only in some R patients. The maximum on the ST-100 isointegral maps also showed a similar behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials as Topic↗
PubMed1986

Body surface potential maps in old inferior myocardial infarction. Assessment of diagnostic criteria.

We assessed the accuracy of criteria for diagnosing an inferior myocardial infarction from body potential maps. Body surface potential maps were recorded from 140 lead points on the entire chest surface in three groups of subjects: group A consisted of 15 patients with an old inferior myocardial infarction and typical electrocardiographic signs of necrosis; group B consisted of 15 patients with an old inferior myocardial infarction, but without electrocardiographic signs of necrosis (inferior myocardial infarction was documented during the acute phase); group C consisted of 30 healthy controls. In each subject body surface potential distributions were examined every 2 msec of the QRS complex. Moreover, the potential-time integrals relating to three intervals (QRS, the first 20 and the first 40 msec of the QRS complex) were calculated at each lead point and transferred to diagrams representing the thoracic surface explored (isointegral maps). For each time interval, the mean isointegral map obtained from group C subjects was subtracted from the isointegral map of each patient. The value obtained at each lead point was then divided by the standard deviation of the normal values for that point; the resulting values indicating the standardized differences from normal values were transferred to another map (deviation index isointegral map, DI map). We considered a reliable index of inferior myocardial infarction an area where the time-integral values were at least 2 SD lower than normal, in the inferior half of the thorax. A number of variables relative to instantaneous potential distribution and to isointegral maps were considered. The DI maps of the first 40 msec of QRS gave the most accurate criteria; in fact, an area of negative values 2 SD lower than normal was found in all group A patients and in 11 out of 15 group B patients (sensitivity 100% in group A, 73% in group B and specificity, 83%). Thus our results indicate that body surface potential maps have greater diagnostic information content than the 12 standard electrocardiographic leads and demonstrate the usefulness of the time integral analysis of body surface potentials for diagnostic interpretation.

Adult↗
PubMed1986

Mapping of body surface potentials in patients with the idiopathic long QT syndrome.

Body surface potential maps were recorded from 140 chest leads in 25 patients affected by the idiopathic long QT syndrome (LQTS) and in 25 healthy control subjects matched for age and sex. Potential time integrals of the QRST and ST-T intervals were calculated at each lead point and displayed as isointegral (ISOI) maps. The main abnormalities noted on the QRST and ST-T ISOI maps were one area of negative values larger than normal in the right anterior and inferior thorax and a complex multipeak distribution of the integral values. At least one abnormality was present in 19 (76%) of the patients with LQTS and four (16%) of the control subjects (p less than .001). Each ISOI map was also represented as a weighted sum of nine fundamental components (eigenvectors) to detect and quantitate the nondipolar content. The percent contribution of the nondipolar eigenvectors (all eigenvectors beyond the third) was significantly higher in the LQTS group than in the control group (p less than .005). Specifically, an abnormally high nondipolar content on the QRST ISOI maps was observed much more frequently for patients with LQTS than for control subjects (nine or 36% vs one or 4%), and this was also true on the ST-T ISOI maps (14 or 56% vs one or 4%). No correlation was found between the major abnormalities on body surface maps and syncopal episodes. However, the high prevalence (76%) of these alterations among the patients with LQTS and their infrequent occurrence in the control population strongly suggests that they may be useful markers for the diagnosis of atypical cases. The prominent electronegative area on the anterior thorax can be related to delayed repolarization of a portion of the anterior wall of the heart. This finding is in agreement with the hypothesis that lower than normal right cardiac sympathetic activity is the main pathogenetic mechanism of LQTS. Multipeak distribution and high nondipolar content suggest regional electrical disparities in the ventricular recovery process. This may in part account for the high susceptibility of patients with LQTS to malignant arrhythmias.

Adolescent↗
PubMed1982

Limits of precordial electrocardiographic mapping in assessing anterior myocardial infarction size.

Purpose of our investigation was to ascertain whether the electrocardiographic mapping of the anterior thoracic wall can provide more precise information on the extent of an anterior myocardial infarction (MI) than the 12 conventional leads do. Thirty-seven patients were studied 1 to 72 months after an acute MI of the anterior wall. All patients underwent left heart catheterization which included selective coronary arteriography and left ventriculography, to evaluate the indication for surgery. Electromaps were obtained by means of 71 Ag-AgCl electrodes located at regular intervals on the thoracic wall (between the right midclavicular line and the left posterior axillary line). The following parameters were considered: total number of Q waves, R waves and ST elevations greater than or equal to 0.05 mV (NQ, NR, NST); the sum of Q, R and ST voltages (sigma Q, sigma R, sigma ST); the sum of Q-wave and R-wave areas (sigma aQ, sigma aR). The electrocardiographic data were correlated with the percentage of left ventricular dyssynergy (corresponding to the ratio between the length of the akinetic and/or dyskinetic portion of the left ventricular silhouette and the total enddiastolic perimeter) and with the ejection fraction obtained from the left ventricular angiograms in right anterior oblique projection. A significant but weak correlation was found only between sigma R, sigma aR and percentage of dyssynergy and between NST, sigma ST and ejection fraction. Thus the amplitude and duration values of positive activation potentials (sigma aR, sigma R) were better predictors of dyssynergy extent than the classical direct signs of necrosis (NQ, sigma Q). The poor correlation observed in our patients between ECG and angiographic data can mainly be due: a) to a lack of concordance between the dyssynergic area and the truly infarcted region; b) to the well-known limits of surface electrocardiography in defining the cardiac generator characteristics. In particular, as far as the adequacy of various ECG recording systems in determining infarct size is concerned, our study suggests that exploring a large thoracic area is not definitely more advantageous than using 12 - lead ECG, when only traditional analysis of electrocardiographic tracings is performed.

Adult↗
PubMed1981

Effect of nitroglycerin on ST potentials in the post-acute phase of myocardial infarction.

Thoracic electromaps were recorded before and after sublingual nitroglycerin (NG) in 26 subjects 15 and 30 days after acute myocardial infarction (MI), in order to evaluate the effect of the drug on injury potentials. Ten patients with documented left ventricular aneurysm were also studied 5 to 46 months after acute MI. Fifteen min after NG there was a significant decrease, compared with basal values, of ST segment elevations, blood pressure and rate-pressure product on both the 15th and 30th days. The degree of ST potentials reduction was not strictly related to the decrease of myocardial oxygen consumption, as indicated by the rate-pressure product. The response to NG on the 15th day did not predict accurately the evolution of injury potentials. In fact there was no significant correlation between percentages reduction of ST after NG on the 15th day and amplitudes of ST segment elevations present on the 30th day. In the patients with ventricular aneurysm, ST potential decrease and hemodynamic changes after NG were similar to those observed in the other groups studied. Our data suggest that it is not possible to differentiate between ST segment elevations associated with a dyssynergic area and those merely due to ischemic injury on the basis of NG sensitivity, and that ST segment elevations in the acute and subacute phase and long after MI have, at least in part, a similar electrophysiological significance.

Adult↗
PubMed1979

[Alterations of ventricular repolarization at rest, in young asymptomatic subjects. Diagnostic and predictive value of non-invasive methods].

In 34 asymptomatic subjects, aged 16 to 39 years, with clearcut abnormalities of ventricular repolarization on resting electrocardiogram, a forced hyperventilation and maximal exercise test were performed. The stress test was repeated, using the same protocol, after sublingual administration of nitroglycerin (0.3 mg) and of i.v. injection of propranolol (0.1 mg/Kg). In 24 subjects an echocardiogram was recorded: a mitral valve prolapse was present in 6 cases, while in 11 cases minor abnormalities were found. The response to exercise test was positive in 50% of cases. After nitroglycerin the ischemic threshold increased in 7 subjects while it remained unchanged or even lowered in 10 cases. In subjects with a negative stress test nitroglycerin did not produce any important electrocardiographic variations both at rest and during exercise. After propranolol injection the repolarization abnormalities on resting electrocardiogram disappeared or decreased in 23 subjects. The drug increased the exercise tolerance in 4 cases; in other 12 subjects the electrocardiographic response to stress testing became normal. During the follow-up period coronary events occurred in 3 cases; in all of them nitroglycerin had induced an increase of ischemic threshold. Our study suggests that the evaluation of the exercise ischemic threshold after nitroglycerin can be useful in order to identify subjects at high coronary risk.

Adolescent↗
PubMed1979

[The diagnostic value of bloodless methods and follow-up in young asymptomatic subjects with positive exercise test (author's transl)].

Fifty asymptomatic subjects, aged 22 to 40, with normal resting ECG and "ischemic" ST depressions during exercise were followed for 44 +/- 18 months. Coronary events occurred only in two cases. Unexpectedly in 12 subjects the response to maximal exercise became normal. In 25 subjects forced hyperventilation, exercise test after nitroglycerin (TNG), and after propranolol (P) were performed. Hyperventilation determined abnormalities of ventricular recovery in all cases. TNG did not improve the response to exercise, as it does in coronary patients, and even significantly decreased the "ischemic threshold"; after P the exercise test became normal in 20 subjects, while in 5 the electrocardiographic ST depressions were markedly reduced. The responses to pharmacological tests after the follow-up period were similar to the first observation. In 8 subjects, in which exercise ST depressions were particularly impressive, Tallium 201 myocardial scanning at rest and during exercise was performed. Myocardial perfusion imaging did not reveal any defect, thus confirming the non-ischemic nature of the ECG abnormalities. Our results confirm the low predictive accuracy (4%) of a positive stress test in a young asymptomatic population and suggest that, among non-invasive methods, exercise response after TNG is usefull in recognizing the "false positive" tests.

Adult↗