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Biomedical subjects

A Nava

Publications and source records attributed to A Nava.

At least 145 records · Page 8Linked to original sources
PubMed1982

Programmed chest-wall stimulation to evaluate the progress of A-V block after pacemaker insertion in patients with trifascicular disease.

Twenty six patients (aged 46-80, mean age 64) with bifascicular block in the presence of prolonged H-V interval (trifascicular block), were followed for an average of 31 months after inserting an R-wave inhibited pacemaker (PM) because of syncope and/or dizzy attacks. The underlying rhythm was evaluated at 4-6-month intervals by three different techniques: 1) 12-lead ECG when intrinsic patient rate was faster than PM rate; 2) abrupt PM inhibition (APMI) by the rapid chest-wall stimulation technique, and 3) progressive PM inhibition (PPMI) using a programmed chest-wall stimulation technique capable of decreasing the PM rate gradually to 30 beats/min before complete PM inhibition. In addition, the PPMI allowed the underlying rhythm to be induced and sustained and properly evaluated without any discomfort to the patient. Following PM insertion, 4 patients (15%) developed complete heart block after a mean follow-up of 43 months, and one patient (4%) developed 2nd degree 2:1 A-V block (VX) after 83 months. The P-R interval increased in 5 patients (19%) and decreased in 2 (8%). No change of A-V conduction was found in 9 patients (34%). Three patients developed low atrial rhythm, atrial flutter and atrial fibrillation, respectively (12%). After PM insertion 2 patients still complained of dizziness. None reported syncope. Two patients died during follow-up, both of congestive heart failure (8%). By detection of intrinsic rhythm it was recognized that a long symptomatic paroxysmal phase may precede the development of chronic complete A-V block. Therefore, the insertion of a permanent PM is recommended in patients with unexplained neurologic symptoms and trifascicular disease, without waiting for documented episodes of complete A-V block.

Aged↗
PubMed1982

Pregnancy termination in dogs with novel non-hormonal compounds. Studies of 2-(3-ethoxy-phenyl)-5,6-dihydro-s-triazole [5,1-a] isoquinoline (DL 204-IT).

Pregnancy termination was obtained in both Beagle and mongrel bitches after a single s.c. or i.m. injection of 2-(3-ethoxy-phenyl)-5,6-dihydro-s-triazole[5,1-a]isoquinoline (DL 204-IT) dissolved or suspended in an oily vehicle. The activity of the compound was dependent on the dose and time of pregnancy. The optimal time of treatment was found to be day 20 of gestation, at which time the smallest effective dose was 6.25 ng/kg. Pregnancy arrest normally occurs during the first stage of embryonic development (between day 25 and 30) due to the degeneration and subsequent resorption of the products of fertilization. Pregnancy termination is never accompanied by intrauterine or placental hemorrhage. After pregnancy arrest the animals return to estrus within a normal interval of time; they exhibit normal mating behaviour and their ability to conceive is not impaired. Later, pregnancies can be interrupted again by the same treatment. After subeffective doses normal parturition occurs at the expected time and the pups do not have any external malformations. High doses given every 15 days for more than one year are well tolerated and do not inhabit either the return of estrous cycle or fertility. Studies of the mechanism of action suggest that the primary site of action is the uteroplacental complex.

Abortifacient Agents↗
PubMed1981

Clinicopathologic assessment of arrhythmias in a case of scleroderma heart disease with sudden death.

Electrophysiologic and histopathologic correlation has been carried out in a patient with scleroderma heart disease, affected by syncopal seizures, who died of recorded ventricular fibrillation. The electrophysiological investigation disclosed dysfunction of sinoatrial conduction, revealed by sinoatrial blocks and by an abnormal return cycle pattern after premature atrial beats. Atrial effective and functional refractory periods were increased and an unusual 'pseudo-Wenckebach' phenomenon between artificial stimulus and atrium was observed during atrial pacing. Intra-AV nodal conduction time was at normal upper limits and Wenckebach-type AV block was obtained on pacing the atrium at 100 beats/min. HV conduction was moderately prolonged in the presence of left anterior hemiblock. The histopathologic substrates of these electrophysiologic disturbances were fibrosis of the sinus node, disrupted internodal pathways and atrio-AV nodal connections, and left bundle branch atrophy. As far as fatal tachyarrhythmia is concerned, myofibrillar degeneration may have contributed to its pathogenesis. It is suggested that both lesions of the ordinary myocardium and specialized conduction system account for the electrical instability of sclerodermic patients.

Adult↗
PubMed1980

A pharmacological approach to the study of AV conduction in man.

Smooth and interrupted curves of AV conduction, generated with an atrial extrastimulus technique, are seen in man, suggesting the involvement of two physiological AV pathways named "alpha" and "beta" and leading to a final common pathway (FCP). In view of this knowledge, the effects of some representative antiarrhytmic agents (Atropine, Verapamil, Ajmaline) were studied in eight patients in order to elucidate the physiological role of the various components of AV junction. Verapamil decreased conduction velocity of both "alpha" and "beta" pathways and increased their refractoriness; Atropine decreased "alpha" and "beta" pathways' refractory periods and increased their conduction velocity; further studies are required to clarify the effects of Ajmaline on AV conduction.

Adolescent↗
PubMed1980

[The left posterior fascicular block: is the diagnosis possible only by ECG? (author's transl)].

The diagnosis of Left Posterior Fascicular Block based on clinical ECG and VCG tracings alone is possible when ECG and VCG allow to recognize asynchronous left ventricular activation. The delayed inscription time of the intrinsecoid deflection in aVF (or V6) in absolute and relative to aVL permits the diagnosis if intrinsecond deflection in aVL exceeds 0,035". Il more premature, a further control is required to distinguish Left Ventricular Hypertrophy from Left Posterior Fascicular Block, both in anatomically vertical heart.

Electrocardiography↗
PubMed1978

[Electrophysiological demonstration of more structures in the atrioventricular node (author's transl)].

Three types of atrioventricular nodal conduction curves, relating A1A2 to H1H2, generated with atrial extrastimulus technique, are known. The first type is smooth, suggesting the homogeneous structure of A-V node. The second type, with abrupt increase in H1H2 response over a critical range of A1A2 coupling intervals, suggests the presence of fast and slow A-V nodal pathways. We have found in five patients the third tipe of A-V conduction curve, giving evidence of an intranodal final common pathway, distal to the fast and slow A-V nodal pathways. The thyrd type of curve enables us to know also some alectrophysiological properties of final common pathway. Indeed we have defined effective and functional refractory periods of fast, slow and final common pathways as far as we can in this type of curve. Paced heart rate variations and atropine medications have led the third type of A-V conduction curve to change into the second type in three cases, into first type in one case. These changes of A-V nodal conduction curves are related to different influence of cardiac cycle lenghts and autonomic nervous system on refractory periods and conduction velocity of the outlined intranodal structures.

Adolescent↗
PubMed1978

[The experience with permanent cardiac pacing at the Surgical Clinic of the University of Padua Medical School (author's transl)].

A computer analysis is reported of the most significant data concerning 1624 pacemaker implantations and 1386 battery replacements. The patients were treated by endocardial stimulation with transvenous electrodes in 91% of the cases; the remainder: 9% received epicardial electrodes. The mode of stimulation was 2189 times "demand", 138 "synchronized" and 683 "asyncronous". Pacers of 13 different brands were used. At the beginning of our experience, the catheter was introduced through the superficial or profunda giugular vein: since 1969 the cephalic vein has been preferred. Epicardial electrodes were implanted via a left thoracotomy but in the most recent years the extrapleural phrenico-pericardial approach has been adopted. In a number of cases external pacemakers have been employed for permanent stimulation. The most common post-operative complications were infection (3.9%), skin erosion (2.2%), catheter rupture (3.5%), electrode dislodgement (1.7%). Such complications are becoming less frequent since 1969, due to technical improvements.

Adolescent↗
PubMed1977

[Reliability of premature atrial stimulation in the study of sinoatrial conduction time (author's transl)].

Premature atrial stimulation was carried out in 32 patients, and for each stimulus the basic cycle (A1A1), test cycle (A1A2), and the return cycle (A2A3) were analyzed. When A2A3 was plotted as the function of A1A2, a biphasic pattern, characterized by a slope phase followed by a "plateau", was observed in 25 subjects. Sinoatrial conduction time (SACT) was calculated using the Strauss method, which assumes that in the plateau A2A3 = A1A1 + SACT. Sinus arrhythmia was also determined in order to evaluate its importance in altering the results of premature atrial stimulation: it should be pointed out that when arrhythmia was marked it was impossible to calculate sinoatrial conduction time. An inverse correlation between A1A1 and the calculated SACT and between A1A1 and A2A3/A1A1 in the plateau was also demonstrated. The reliability of SACT obtained by premature atrial stimulation is discussed in relation to the results obtained and the data found in the literature.

Adolescent↗