Biomedical subjects

J M Almendral

Publications and source records attributed to J M Almendral.

45 records · Page 3Linked to original sources

PubMed1985

Entrainment of ventricular tachycardia by atrial depolarizations.

Four patients in whom rapid atrial pacing resulted in transient entrainment of a sustained ventricular tachycardia (VT) are reported. Ventricular fusion was seen in 3 of the 4. The following new observations were made: (1) A single atrial depolarization resulted in ventricular fusion and resetting of a VT, while atrial pacing at a faster rate entrained the same VT but without detectable fusion. This suggests that fusion during entrainment may be a rate-dependent phenomenon. (2) The interval between the last paced beat and the first nonpaced VT beat was different from the pacing cycle length in 3 patients. Two mechanisms accounted for this: the initial forces of each entrained QRS occurring as a result of the pacing wavefront, with fusion taking place only during the terminal forces, and the last entrained cycle exceeding the pacing cycle length by an amount related to the nonfused portion of the QRS, and delay in the presumed reentrant circuit responsible for the tachycardia. One VT was entrained with atrial pacing while ventricular pacing at the same rate resulted in termination, suggesting "site specificity" for termination. It is concluded that entrainment can occur without the criteria previously described as characteristic of it and that additional phenomena may be observed after stimulation that further support reentry as the mechanism of VT.

Adult↗

PubMed1985

Electrophysiologic evaluation and follow-up characteristics of patients with recurrent unexplained syncope and presyncope.

One hundred nineteen patients with unexplained syncope (82%) or presyncope (18%) underwent complete electrophysiologic study (EPS). Symptoms were recurrent in 72% of the patients. Fifty-two percent of the patients had structural heart disease. Forty-one patients had normal EPS results and 78 had electrophysiologic abnormalities (ventricular tachycardia in 31, induced atrial flutter/fibrillation in 17, vasovagal syncope in 8, hypersensitive carotid sinus syndrome in 7, supraventricular tachycardia in 6, heart block in 5 and sick sinus syndrome in 4). The presence of structural heart disease (p = 0.0033) and previous myocardial infarction (p = 0.05) were the only clinical or electrocardiographic predictors of a positive EPS response. Therapy was guided by EPS and patients were followed for 27 +/- 20 months (mean +/- standard deviation). In the patients with negative EPS results, 76 +/- 11% (mean +/- standard error) were symptom-free at follow-up, compared to 68 +/- 10% in the group with positive EPS responses. No clinical variables helped to predict remission in the absence of therapy. One patient in the negative EPS response group and 2 patients in the EPS positive group died suddenly (cumulative survival 94 +/- 4%). Total cardiovascular mortality was 13% in the positive EPS response group, and 4% in the negative EPS response group. Thus, certain clinical characteristics are helpful in selecting patients for study. Electrophysiologically guided therapy is associated with a recurrence and sudden death rate similar to an untreated control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

Use of programmed electrical stimulation to predict sudden death after myocardial infarction.

The use of programmed ventricular stimulation to identify patients at risk for sudden cardiac death following myocardial infarction has not yet been firmly established. The repetitive ventricular response following extrastimuli does not appear to be useful in identifying patients at risk and should not be used to guide antiarrhythmic therapy. Similarly, the response to single and/or double ventricular extrastimuli delivered at twice diastolic threshold from a single right ventricular site during normal sinus rhythm and ventricular pacing also does not appear to be helpful in identifying patients at risk for life-threatening ventricular arrhythmias. A more vigorous stimulation protocol that involves more than one right ventricular site and increased current strength may be necessary to elicit a predictive electrophysiologic response. The need for a more vigorous stimulation is suggested by two preliminary studies. Confirmation of initial reports is necessary. The predictive value of the response to programmed ventricular stimulation must be compared with other noninvasive and invasive measurements of left ventricular dysfunction and the degree of spontaneous ventricular ectopy to determine its superiority or to ascertain multiple variables that can be used together to identify those patients most likely to die suddenly after myocardial infarction. Stimulation protocols used during programmed stimulation must have sufficient sensitivity without sacrificing specificity. A concerted effort using uniform stimulation protocols in large numbers of patients is essential to resolve this important clinical problem.

Cardiac Pacing, Artificial↗

PubMed1984

Timing of the right ventricular apical electrogram during sustained ventricular tachycardia: relation to surface QRS morphology and potential clinical implications.

To evaluate the timing of the right ventricular (RV) apical electrogram in relation to the QRS complex during ventricular tachycardia (VT), 94 episodes of sustained uniform VT were analyzed in 56 patients. The timing of the RV apical electrogram varied and could be recorded from 33 ms before to 180 ms (mean 77 +/- 44 ms) after the onset of the QRS complex. The timing of the RV apical electrogram, expressed both as an absolute value and as a percentage of a QRS width, was significantly different when right bundle branch block (BBB) morphology VT (95 +/- 37 ms) and left BBB morphology VT (40 +/- 341) were compared (p less than 0.001). The timing of the RV apical electrogram, expressed as a percentage of the QRS width, was significantly different when VT with different axes were compared in the right BBB VT group (p less than 0.01). A left BBB VT, as compared to a right BBB VT, predicted an RV apical electrogram occurring in the first 35% of the QRS with a sensitivity of 74%, a specificity of 91%, and a positive predictive value of 84%. Right BBB VT with a right and inferior axis were usually associated with the latest occurring RV apical electrogram. A right BBB VT with a right and inferior axis predicted an RV apical electrogram inscribed in the latter half of the QRS with a sensitivity of 65%, a specificity of 84% and a positive predictive value of 80%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1984

Molecular cloning of African swine fever virus DNA.

African swine fever virus DNA (about 170 kbp) was cleaved with the restriction endonuclease EcoRI and most of the resulting 31 fragments were cloned in either the phage vector lambda WES lambda B or the plasmid pBR325. Three fragments were not cloned in those vectors, the largest fragment EcoRI-A (21.2 kbp) and the two crosslinked terminal fragments, EcoRI-K' and D'. Endonuclease SalI cut fragment EcoRI-A into three pieces which were cloned in plasmid pBR322. The two terminal EcoRI fragments were cloned after removal of the crosslinks with nuclease S1 and addition of EcoRI linkers to the fragment ends. The complete library of the cloned fragments accounted for about 98% of ASF virus genome, the missing sequences being those removed by the nuclease S1 in the process of cloning the terminal fragments.

African Swine Fever Virus↗

PubMed1984

Restriction site map of African swine fever virus DNA.

Treatment of African swine fever virus DNA (about 170 kbp) with the restriction endonucleases SalI, EcoRI, KpnI, PvuI, and SmaI yielded 14, 31, 17, 13, and 11 fragments, respectively. The order of the restriction fragments produced by each nuclease was established by identifying the crosslinked EcoRI and SalI terminal fragments and then finding overlapping fragments. The five restriction fragment maps were integrated into a single map by locating SalI, KpnI, PvuI, and SmaI sites in cloned EcoRI fragments, and orienting each fragment in the overall map.

African Swine Fever Virus↗

PubMed1984

Terminal and internal inverted repetitions in African swine fever virus DNA.

An electron microscopic analysis of the heteroduplexes formed by reannealing denatured terminal restriction fragments of African swine fever (ASF) virus DNA showed Y-shaped molecules with a 2.1-kilobase-pair-long double-stranded tail and two single-stranded arms. This indicated that ASF virus DNA has terminal inverted repetitions with a length of 2.1 kbp. In addition, under less restrictive hybridization conditions, most of the heteroduplexes showed a 0.13 kbp-long internal double-stranded region, separated from the long terminal repeat by a single-stranded asymmetric loop. These internal inverted repetitions did not match well, since the heteroduplexes melted under conditions where those of the terminal repetitions were stable. In the terminal fragments EcoRI-K' and D', the distance between the terminal and the internal inverted repetitions was 2.4 and 0.4 kbp, respectively.

African Swine Fever Virus↗

PubMed1982

Treadmill stress testing in the evaluation of patients with valvular heart disease. Possible role in the assessment of functional capacity and severity of the lesion.

A series of 123 patients with valvular heart disease underwent treadmill stress testing (Bruce's protocol). Neither mortality nor serious complications were observed. The incidence of exercise-induced ventricular ectopy was 35% and that of complex ventricular ectopy 19%. Patients with pure left ventricular volume overload had a significantly higher incidence of exercise-induced ventricular ectopy than did patients with other valvular diseases. A significant relation was found between functional class (NYHA) and either duration of exertion or functional aerobic impairment. The NYHA classification was found to coincide in 62% of the instances with another based on the results obtained from stress testing. In patients with mitral stenosis a significant although slight correlation was found to exist between mitral valve area and duration of exercise. The inability to reach stage III of Bruce's protocol was associated with a critical mitral stenosis. A hypotensive response to exercise was frequent both in mitral stenosis and aortic stenosis. But whereas in aortic stenosis it was characteristic of the most severe lesions, in mitral stenosis it bore no relation whatsoever to severity. Thus, treadmill stress testing in valvular heart disease is safe, can be helpful in quantifying functional disability and may provide a clue as to the severity of the lesion in specific subsets.

Adolescent↗

PubMed1979

Two methods of large-scale extraction of an antibiotic produced by Myxococcus coralloides.

Two methods for the isolation of an antibiotic produced by Myxococcus coralloides have been developed: the chloroform extraction method and the charcoal adsorption method. The recovery of antibiotic in each case was 25% and 30%, respectively, by the two methods. Although the two methods yield a relative low recovery, the charcoal adsorption method seems more attractive and promising due to its simplicity and economic advantages.

Adsorption↗