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Biomedical subjects

J Benhorin

Publications and source records attributed to J Benhorin.

At least 55 records · Page 3Linked to original sources
PubMed1990

Long QT syndrome. New electrocardiographic characteristics.

The long QT syndrome is electrocardiographically characterized by a prolonged QT interval and by several other, more subtle, ST-T-U wave abnormalities, most of which have not been quantified. To determine the possible usefulness of several new electrocardiographic characteristics in identifying patients with known long QT syndrome, logistic regression models were applied to a data base of seven new, relatively independent, electrocardiographic repolarization variables. These were measured on digitized 12-lead electrocardiograms of 315 normal subjects and 37 patients with the long QT syndrome (members of well-identified long QT syndrome families, QTc greater than 0.44 second, 27% symptomatic), who ranged in age from 17 to 60 years. Electrocardiographic variables that independently differentiated (p less than 0.001) patients with long QT syndrome from normal subjects included quantitative measures of repolarization: early duration, rate, T wave symmetry, late phenomena, and heterogeneity. All selected repolarization variables except the early duration variable were essentially independent of the QTc (r2 less than 0.15), and all contributed significantly to the identification of patients with long QT syndrome. A classification model of five electrocardiographic predictor variables resulted in an estimated sensitivity (95% confidence interval) of 92.6% (81.6-100%) and an estimated specificity (95% confidence interval) of 95.8% (93.6-98.1%). This model performed significantly better than an alternative classification model that was based on the early duration variable as a single predictor variable. The symptomatic status of patients with long QT syndrome could not be predicted by any combination of the electrocardiographic variables in the investigated model.

Adolescent↗
PubMed1989

Residual left ventricular function and prognosis of patients with asymmetric septal hypertrophy recovering from acute myocardial infarction.

The prognosis of patients recovering from acute myocardial infarction (MI) depends mainly on their residual left ventricular (LV) function. In patients with asymmetric septal hypertrophy (ASH) who are recovering from MI, a larger functioning myocardial mass may remain. However, the frequency of ASH in these patients has not yet been described. Predischarge echocardiography, radionuclide ventriculography, and treadmill stress tests were performed in 403 consecutive patients who had recovered from acute MI. Eighty-eight patients (22%) had ASH with septal thickness greater than or equal to 1.3, and 32 (8%) had septal thickness greater than or equal to 1.5 cm. One hundred thirty-six patients who had recovered from a first MI and had no ASH served as control subjects. Left ventricular ejection fraction (LVEF) in the group with ASH was significantly higher than in control subjects (61% vs 50%; p = 0.0001). LV end-diastolic diameter (LVD(d] and E point septal separation (EPSS) were smaller in the group with ASH (4.9 cm and 5.4 mm) than in the control group (5.5 cm and 10.5 mm). The frequency of positive treadmill test results, angina pectoris, recurrent MI, heart failure, and death during a 22-month follow-up period was similar in both groups. Fifty subjects in the control group were matched with 50 patients from the group with ASH on the basis of maximal level of creatine phosphokinase, location of infarct, and presence or absence of hypertension, and the difference between the two groups was even more marked (LVEF 48% vs 61%, respectively; p = 0.0004).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Electrocardiographic quantitation of ventricular repolarization.

Quantification of the electrocardiographic ventricular repolarization involving the T-U wave complex is usually performed with reference to the axis of the T wave and the QT interval duration. A novel quantitative approach to improve the description of ventricular repolarization was applied to the digitized electrocardiograms of 423 normal subjects. Six electrocardiographic repolarization characteristics were identified: duration, rate, area, symmetry, late phenomena, and interlead heterogeneity. A computer algorithm was designed to automatically interpret the electrocardiographic repolarization segment and measure 11 variables that quantified these repolarization characteristics. The application of redundancy-reduction techniques selected a final set of seven variables that were used in the statistical analysis. The QT interval, which was included in the initial group of variables, was replaced by the time interval between S wave offset and T wave maximum. All selected electrocardiographic variables were independent of age (r2 less than 0.11) and body surface area (r2 less than 0.03); all except the early duration variable were heart rate- and QT interval-independent (r2 less than 0.2, r2 less than 0.13, respectively; and most were uncorrelated to each other. A comparison of repolarization characteristics by gender revealed that repolarization duration was significantly more prolonged (p less than 0.0001) in women than in men. This multidimensional quantitative approach conveys a new and more complete description of the repolarization process and provides an electrocardiographic repolarization database in normal subjects as a reference standard for identifying patients with disordered repolarization.

Adult↗
PubMed1989

The interaction between diltiazem and left ventricular function after myocardial infarction. Multicenter Diltiazem Post-Infarction Research Group.

The interactions between diltiazem and three parameters of left ventricular function using cardiac death as the end point were investigated in 2,466 patients, aged 25-75 years, who were involved in the long-term diltiazem postinfarction trial. Indexes of left ventricular function included pulmonary congestion on chest x-ray, acute anterolateral Q wave myocardial infarction on electrocardiogram, and radionuclide ejection fraction. Pulmonary congestion and acute anterolateral infarction had significant (p less than 0.01) interactions with treatment allocation, and the third variable, ejection fraction, showed a similar trend (p less than 0.1). There was a diltiazem-related reduction in cardiac death (Cox hazard ratio, 0.76-0.86) for each of the parameters reflecting good ventricular function, and a significant diltiazem-related increase in cardiac death (Cox hazard ratio, 1.52-1.85) for each of the parameters associated with impaired function. Three-factor interactions highlighted the extremes of the favorable and adverse effects of diltiazem in subsets with unimpaired and impaired left ventricular function. These findings permit more appropriate selection of patients for the safe and effective administration of diltiazem to postinfarction patients.

Adult↗
PubMed1988

Occurrence, characteristics and prognostic significance of early postacute myocardial infarction angina pectoris.

To determine the incidence, clinical characteristics and prognostic significance of early spontaneous angina after acute myocardial infarction (AMI), the database involving the 867 participants of the Multicenter Post-AMI Program, who were followed for 1 to 4 years after AMI, was analyzed. Two hundred eighty-six patients (33%) had in-hospital postinfarction angina. During a mean follow-up of 31 months, patients with postinfarction angina were more frequently (p less than 0.001) hospitalized for cardiac causes and underwent coronary artery bypass graft surgery; however, their cardiac mortality rates at 1 year (8.4%) and at 4 years (14.3%) were not significantly different from those among patients without postinfarction angina (7.1 and 12.9%, respectively). The only anginal characteristic found to be associated with increased subsequent cardiac mortality (17.9% at 1 year, 39.2% at total follow-up) was high frequency angina (greater than or equal to 1 daily episodes). High frequency angina occurred in a small subset of 28 patients (3.2% of the study population, 9.8% of patients with postinfarction angina). Clinical variables representing higher grades of mechanical dysfunction and electrical instability after infarction were significantly more common among patients with high frequency angina than among those with low frequency angina. Cox survivorship analysis revealed that high frequency angina made a significant contribution to the risk of post-AMI cardiac death (hazard ratio 2.5, p = 0.01), which was independent of the effect of predischarge reduced radionuclide ejection fraction and Holter-recorded frequent or repetitive ventricular premature complexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Characteristics of silent and symptomatic myocardial ischemia during daily activities.

In 191 patients with proven coronary artery disease, 24-hour Holter monitoring detected 587 transient episodes of ST depression during daily activities. Of that total, 424 episodes were silent (72.3%) and 163 were symptomatic (27.7%). There were no statistically significant differences between silent and symptomatic episodes as to their mean duration (15.1 vs 14.3 minutes, respectively), heart rate at onset of ST depression (93 vs 96 beats/min, respectively), heart rate at the time of maximal ST depression (114 beats/min, both) and mean maximal ST depression (1.9 vs 2.0 mm, respectively). Of the 191 patients, 104 (55%) had only silent episodes, 33 (17%) only symptomatic episodes and 54 (28%) had both types ("mixed"). All patients, regardless of episode type, were of similar age, received comparable medical therapy, had a similar extent of angiographically documented coronary artery disease and similar episode characteristics. However, mixed-episode patients had significantly more ischemic episodes per day (4.8) than silent-episode (2.6) and symptomatic-episode (1.9) patients (p less than 0.001 for both) and a longer total period of daily ischemia (60 minutes), than the other 2 groups (36 and 28 minutes, respectively, p less than 0.001 for both). Of the 191 patients, 97 (51%) had had a previous myocardial infarction. The characteristics of their silent and symptomatic episodes were similar to the 94 (49%) patients without infarction, except for a longer duration of the silent episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1988

Sinus node and atrioventricular nodal function in 220 patients recovering from acute myocardial infarction.

Sinus node and atriventricular (A-V) nodal functions were evaluated by right atrial pacing in 220 consecutive patients recovering from acute myocardial infarction (AMI), 10-28 days after the infarct (mean = 14 days). In the 188 patients in whom a pacing rate of 120 beats/min could be achieved, sinus node recovery time, corrected sinus node recovery time (CSNRT) and total recovery time were correlated to infarct site and the presence or absence of myocardial ischemia. Sinus node recovery time and total recovery time were significantly longer in patients with inferior (1,153 + 28 and 3,129 + 179 ms, respectively) or non-Q-wave infarct (1,112 + 28 and 3,730 + 266 ms, respectively), than in patients with anterior infarct (1,044 + 20 and 1,153 + 28 ms, respectively). The parameters were within the reported normal range. When corrected for heart rate (CSNRT), these differences were no longer present. The presence or site of residual ischemia during right atrial pacing did not affect the sinus nodes parameters. A-V nodal function, studied in all 220 patients, was assessed by the appearance of second-degree A-V block at pacing rates below 120 beats/min and by measuring the shortest atrially paced cycle length with 1:1 A-V conduction. Second-degree A-V block appeared at a similar frequency in different AMI locations. Thus, sinus and A-V node functional status in patients recovering from AMI are not affected by infarct site or by the presence or absence of residual myocardial ischemia.

Adult↗
PubMed1988

Treatment of torsade de pointes with magnesium sulfate.

Twelve consecutive patients who developed torsade de pointes (polymorphous ventricular tachycardia with marked QT prolongation, TdP) over a 4 year period were treated with intravenous injections of magnesium sulfate. In nine of the patients a single bolus of 2 g completely abolished the TdP within 1 to 5 min, and in three others complete abolition of the TdP was achieved after a second bolus was given 5 to 15 min later. Nine of the patients also received continuous infusion of MgSO4 (3 to 20 mg/min) for 7 to 48 hr until the QT interval was below 0.50 sec. In nine of the 12 patients the TdP was induced by antiarrhythmic agents. The QT interval preceding TdP ranged from 0.54 to 0.72 sec. After the MgSO4 bolus, which prevented the recurrence of TdP, no significant changes were observed in the QT interval. There were no side effects of this treatment. In eight of the 12 patients potassium levels before the TdP were below 3.5 meq/liter; magnesium levels were available in eight patients before TdP, and were normal in all. Five additional patients with polymorphous ventricular tachycardia but normal QT intervals (non-TdP patients) received two to three boluses of MgSO4. This treatment was ineffective in all, but they responded to conventional antiarrhythmic therapy. Thus, MgSO4 is a very effective and safe treatment for TdP, and its application is rapid and simple. Its use is therefore recommended as the first line of therapy for TdP.

Aged↗
PubMed1987

Day-to-day variability of myocardial ischemic episodes in coronary artery disease.

Twenty patients with chronic stable angina pectoris, proved coronary artery disease, positive treadmill stress test response, and at least 2 episodes of ischemia per day underwent 72 hours of Holter monitoring during daily activities. During this period they had 389 ischemic episodes: 104 (27%) symptomatic and 285 (73%) silent. Marked variability was observed between patients in the number of ischemic episodes (range 2 to 15 per day, mean 6.5), duration of ischemia (range 6 to 419 minutes/day, mean 76.5), maximal ST depression (range 1 to 6 mm, mean 3.4) and heart rate at the beginning of ST depression (range 75 to 105 beat/min, mean 91). The day-to-day variability in individual patients between the different days in the number of ischemic episodes was 36%, in duration 51%, and in maximal degree of ST depression 31%. Only 9% variability was noted in heart rate at the beginning of ST depression. Similar day-to-day variability in individual patients was noted in the symptomatic and silent episodes. For clinical purposes of evaluation of ischemia during daily activities, 1 day of monitoring appears to be sufficient because within the first day, 78% of the maximal number of ischemic episodes, 64% of their duration, and 84% of the maximal degree of ST depression were detected. However, for evaluation of anti-ischemic drugs at least 2 monitoring days are required.

Aged↗
PubMed1986

Myocardial ischemia during daily activities and stress.

Twenty-four-hour, 2-channel Holter monitoring during daily activities was performed in 210 patients; during the same day a Bruce protocol treadmill test was also performed and the electrocardiogram was recorded using the same Holter system. Significant ST-segment depression was observed during daily activities in 97 patients, while similar changes were recorded during the treadmill test in 122 patients. Thus, 77% of patients with ST depression during the provocation of the treadmill test had ischemic episodes during their everyday life. On the other hand, 3 patients with proven significant coronary artery disease had spontaneous ischemic episodes during daily activities, but had a negative stress test. The ischemic changes during daily activity developed at a lower heart rate than during stress testing (94 beats/min vs 109 beats/min, respectively, p less than 0.05). A total of 351 ischemic episodes were recorded during daily activities, 241 (69%) of these were asymptomatic. In 46 patients all episodes were asymptomatic, in 15 all were symptomatic, while in 36 both symptomatic and silent episodes were detected. The mean duration of the symptomatic episodes was 13.7 minutes and that of the asymptomatic ones was 14.9 minutes (difference not significant). The degree of ST depression in these 2 groups was also similar. Because of more advanced symptomatology in 143 patients, coronary arteriography was performed; 43 had normal and 100 had pathologic coronary arteries. In this selected group, the sensitivity of Holter monitoring during daily activity was 87% and during stress 97%; the specificity during daily activity was 95% and during stress 88%.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1985

Reciprocal electrocardiographic changes in acute myocardial infarction.

If reciprocal electrocardiographic changes during acute myocardial infarction (AMI) are a result of ischemia of the wall opposite the AMI, a stress test is expected to induce similar changes in the corresponding electrocardiographic leads. Right atrial pacing was used as a myocardial stress method in 137 consecutive patients recovering from a transmural AMI, and the appearance of pacing-provoked ischemia before hospital discharge was correlated to the presence of absence of ST depression in the opposite wall during the initial 48 hours. Of the 137 patients, 83 (61%) had reciprocal changes; they were more common in inferior (87%) than in anterior (37%) AMI (p less than 0.01). Of 54 patients without reciprocal changes, only 5 (9%) had ST depression during predischarge pacing; however, of the 83 patients with reciprocal changes, 41 had pacing-induced ischemia (p less than 0.01) and 42 did not, indicating that in half of this group the reciprocal changes represent ischemia of the opposite wall. In the other half of the group, without ST depression during pacing, these changes may be a "mirror image" phenomenon. Follow-up showed that angina pectoris, positive treadmill test response 6 months later, or recurrent AMI all consequences of impaired myocardial blood supply, were significantly more frequent in patients with reciprocal changes. This group could be further separated according to the results of right atrial pacing, because angina pectoris or recurrent AMI were infrequent among those with reciprocal changes and negative pacing responses, but was frequent among those with reciprocal changes and positive pacing responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Holter recording during treadmill testing in assessing myocardial ischemic changes.

One hundred forty-four patients underwent a Bruce protocol treadmill exercise test during which an electrocardiogram (ECG) was recorded simultaneously with a 2-channel Holter recorder with bipolar V3- and V5-like leads and by a conventional 12-lead system. Sixty-eight patients had no ST depression on either the Holter or on the 12-lead ECG during the exercise test, whereas in 70 patients ischemic changes were recorded by both methods; thus, in 138 of the 144 patients (96%), the results of the 2 tests were concordant. The severity of ST depression, as judged by the heart rate at which ischemic changes were first noted and the maximal ST depression observed, were similar on both recording systems. The Holter system identified 6 of the 7 patients whose ischemic changes were confined to the inferior wall on the 12-lead ECG. The addition of the V3 lead as a second ischemic lead increased the ischemia detection by 10%. Ninety-five patients also underwent coronary arteriography. In these patients the sensitivity of the Holter system during exercise in detecting significant coronary artery disease was 81% and that of 12-lead ECG was 84%, the specificity was 85% and 85%, respectively, and the positive predictive value 91% and 91%, respectively. Thus, the 2-channel Holter recording system with bipolar V3- and V5-like leads was as accurate as the 12-lead system in detecting ischemic changes during exercise and proved that ambulatory monitoring system can reliably reproduce ST segment.

Adult↗