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P Pascotto

Publications and source records attributed to P Pascotto.

At least 37 records · Page 2Linked to original sources
PubMed1984

Mid-diastolic intraventricular functional block. A new mechanism for intermittent intraventricular blocks?

Experimental and clinical studies have demonstrated the existence of phase 3 and phase 4 functional blocks. In this report six cases are presented in which the electrophysiological study demonstrated the existence of a functional intraventricular block different from phase 3 and phase 4 blocks. In these cases the occurrence of the block was related to the presence in mid-diastole of a zone of block preceded and followed by intervals of unimpaired conduction. In two of 6 cases the functional block (infrahisian block) was not present in the basal tracing; it occurred during programmed atrial stimulation in a range of critical H1H2 coupling intervals delivered late in diastole, and did not appear after earlier stimuli. In the remaining four cases the conduction disturbance (2 RBBB, 2 infrahisian blocks) was present in the basal tracing, but disappeared both during early and late supraventricular extrastimuli, the first having short H1H2 intervals, the latter having H1H2 intervals longer than H1H1 basal cycle length. The width of the mid-diastolic zone of block varied from a few msec to hundreds of sec, and increased as heart rate increased. Two hypotheses are put forward in order to explain the electrophysiological mechanism responsible for the phenomenon: 1) a longitudinal dissociation in the conducting system, generating two different ways, one having a long refractory period, the other having a phase 4 spontaneous depolarization; they would be responsible of phase 3 and phase 4 blocks respectively. The early and late zones of conduction could be explained by an alternate conduction in one of the two ways, while the mid-diastolic zone of block could be due to a simultaneous block in both ways; 2) the existence of a diastolic oscillatory potential (late after-depolarization). In the latter case we can suppose that the mid-diastolic block was due to the stimulation of the cells of the conducting system before the restoration of the normal diastolic potential. Our electrophysiological data offer a new contribution to the understanding of intermittent intraventricular blocks. However further experimental and clinical studies are needed to confirm our electrophysiological hypotheses.

Adult↗
PubMed1983

Possible role of a ventricular conduction disturbance in the electrogenesis of the ECG-VCG signs of myocardial infarction.

The typical QRS patterns of myocardial infarction (MI-QRS) are commonly attributed to myocardial cellular death. However, observation of a transient appearance of MI-QRS during coronary insufficiency, the disappearance of MI-QRS after coronary by-pass surgery and the appearance of MI-QRS after intracranial hemorrhage suggest that a different electrophysiological mechanism may be at work. There is a single convincing explanation for all these observations. It seems possible, at least theoretically, that a localized conduction disturbance can generate or contribute to the generation of the MI-QRS. The results obtained in nine out of 194 cases studied by means of premature right atrial stimulation (PRAS) in our laboratory seem to confirm this hypothesis. In five of them we observed typical MI-QRS in the aberrant beats which were absent in the basal tracings. In the other four cases, MI-QRS which were present in basal tracings disappeared in the aberrant beats. In three of these a reduction in the duration of QRS was also observed, while in the fourth the duration of QRS did not change. In no case could the alterations of QRS (induction or disappearance of MI-QRS) be explained by a classical conduction disturbance, preexcitation or by a premature ventricular beat. While the induction of MI-QRS was clearly due to an aberrant conduction in the supraventricular beats, the disappearance of basal MI-QRS changes in premature supraventricular beats is more difficult to explain. One possible electrophysiological mechanism could be a supernormal phase conduction. If this is the case, the basal MI-QRS could be due to a ventricular conduction disturbance. In conclusion, our results suggest that MI-QRS can be generated, at least in our cases, by a localized conduction disturbance.

Adult↗
PubMed1982

Effects of oral calcium-antagonists in spontaneous angina. Verapamil and nifedipine in a double-blind cross-over trial.

Verapamil and nifedipine, two calcium-antagonist drugs, were evaluated in a double-blind cross-over trial. The study was performed in 15 patients admitted to our Coronary Care Unit for spontaneous angina. Before and after a 24 hours placebo period, oral verapamil 480 mg daily and oral nifedipine 60 mg daily were administered alternatively. Symptomatic as well as asymptomatic ischemic episodes with ST segment elevation or depression and ventricular and supraventricular ectopic beats were documented by continuous electrocardiographic Holter monitoring. The average number of attacks during the placebo periods was 243; the number of attacks decreased to 129 during verapamil treatment (P less than 0.05) and to 57 during nifedipine treatment (P less than 0.01). Ventricular ectopic beats decreased with both drugs while supraventricular ectopic beats decreased only during verapamil treatment. The difference was not statistically significant because of a small number of observations. In conclusion the two drugs appear to be effective in the management of patients with unstable angina at rest, especially in the variant form.

Angina Pectoris↗
PubMed1982

[Clinical significance of corrected sinus node recovery time and natural and unnatural history of sinus node dysfunctions. A four-year prospective follow-up of 101 cases].

The clinical significance of corrected sinus node recovery time (CSNRT) and the natural and unnatural history of sinus node dysfunctions are not completely known. To gain some insight into this problem, 101 patients (pts) (54M, 47F, mean age +/- SD = 62.02 yrs +/- 14.42) with clinical and ECG signs of definite or suspected sick sinus syndrome (SSS) underwent an electrophysiologic study and then were prospectively followed for a mean period of 44.36 months +/- 18.96 (range: 2-78 months). The pts were divided into two groups: 1) Group A: 68 pts with prolonged CSNRT (greater than 500 msec); 2) Group B: 33 pts with normal CSNRT. Thirty-three pts of Group A (48.5%) and 2 pts of Group B (6.1%) received VVI pacemaker implantation (PM) immediately after the electrophysiologic study. The following results were obtained: 1) Pts of Group A showed a higher prevalence of organic heart disease and of ECG signs of definite SSS than pts of Group B. (p less than 0.05). Moreover, the higher the CSNRT in Group A pts, the more severe the ECG abnormalities of SSS. 2) Pts without PM, both of Group A and Group B, noted during the follow-up period a disappearance of neurological symptoms (syncopes and/or dizziness) and of ECG abnormalities of SSS in more than 50% of the cases. However, this was less evident in Group A pts compared with Group B pts (53.8% vs 78.6% regarding neurological symptoms and 54.3% vs 74.1% regarding ECG abnormalities of SSS) as well as in pts with organic heart disease in comparison with those with primitive SSS. Moreover, the number of pts who needed PM implantation during the follow-up period due to the worsening of clinical and ECG signs of SSS were higher in Group A than in Group B (20% vs 6.5%). The occurrence of cardiac death among the pts without PM was similar in pts of Group A (8.5%) and in those of Group B (9.7%). One pt of Group A without PM died suddenly (less than 1 hour). 3) Pts who required PM implantation were older (p less than 0.01) and showed a prevalence of organic heart disease higher (p less than 0.05) than those who did not require PM implantation. Pts with PM, both of Group A and Group B, showed a complete disappearance of syncopes and a clear-cut reduction of dizziness after implantation of it. On the contrary, dyspnea nearly always persisted and sometimes appeared when initially absent. Sudden and non-sudden cardiac death in PM pts (13.6%) was somewhat more frequent than in those without PM. 4) The incidence of stable atrial fibrillation was 12.1% in pts without PM and 27.2% in pts with PM. The occurrence of stable atrial fibrillation in pts without PM was generally not followed by clinical improvement. 5) The incidence of cerebrovascular accidents was approximately 8%. The accidents always occurred in pts with organic heart disease and often in the older pts (mean age: 75.1 yrs +/- 5.7) particularly in those with PM. A bradycardia-tachycardia syndrome was observed only in 3 pts who had a stroke...

Cardiac Pacing, Artificial↗
PubMed1979

The role of left ventricular conduction in the electrogenesis of left ventricular hypertrophy. An electrophysiologic study in man.

Various electrocardiographic and vectorcardiographic (ECG-VCG) patterns of ventricular conduction disturbances are inducible by premature right atrial stimulation (PRAS). These patterns are a consequence of different degrees of refractoriness in the specialized ventricular conduction system. We observed that the intermediate phase of left bundle branch block (LBBB) induced by PRAS in 20 subjects with normal basal QRS (complexes) were similar to those of left ventricular hypertrophy (LVH). In 18 patients with basal ECG-VCG signs of LVH, right bundle branch block (RBBB) induced by PRAS produced a progressive disappearance of these signs and the "normalization" of the tracings. The initial maximum QRS vector decreased, disappeared or remained absent in the patients with LBBB induced by PRAS, and appeared (when absent in the basal VCG) and remained unchanged (when present) in patients with RBBB induced by PRAS. In this paper we discuss the electrogenetic implications of these data. The ECG-VCG sings of LVH are probably dependent on a slowed conduction in the left bundle branch system, while anatomical hypertrophy per se probably plays a less important role.

Adult↗
PubMed1977

[Evolutive study of the vectorcardiogram from the 14th day to the 6th month of life on the normal infant].

With the purpose of a better evaluation of the changes of cardiac potentials during the early hemodynamic arrangement of the normal heart, the authors analyze the VCG of 10 normal children periodically recorded from the 14th day to the 6th month from birth. Rotation of QRS, T and P loops in the three planes, direction and voltage of principal planar and spatial vectors were analyzed. The QRS loop showed a balanced distribution between right and left ventricular forces in the second week and developed a leftward orientation from the 4th week to the 3rd month, as demonstrated both by the loss of clockwise rotation of horizontal QRS loop and by the progressive leftward and backward direction of intermediate vectors. The initial vectors were sketched or absent in the 14th day and increased successively until the typical Q loop. The voltage of terminal vectors did not change in the course of time, but the S loop in the horizontal plane lost its original clockwise rotation and shifted to middle posterior line. The T loop progressively shifted backward so that it was always posterior after the 30th day. The P loop in the frontal plane was similar to the adult's one while in the horizontal plane it often presented a figure-of-eight. The semeiological aspects and the electrogenic considerations of these changes were discussed.

Age Factors↗
PubMed1977

[The mechanism of the chronic supraventricular tachycardia: an intracavitary electrophysiological study (author's transl)].

Chronic Supraventricular Tachycardia (CST) or Chronic Atrial Tachycardia is a relatively rare arrhythmia. Because of very poor number of cases studied with electrophysiologic techniques its mechanism is still debated. Three cases of CST, one of persistent type and two of repetitive type, are reported. His bundle electrogram, high and low right atrial electrograms and atrial stimulation were performed in every case, ventricular stimulation in only one case. The Amiodarone, Pindolol, Verapamil and vagal manoeuvres effects were evaluated in all cases. The site of origin of tachycardia, atrial in cases 1 and 3 and junctional in case 2, was estabished by atrial map. The electrophysiologic findings suggested the presence of an ectopic focus in cases 1 and 3 and of an AV nodal re-entry circuit in case 2. Our results and those of the literature indicate that the site and the mechanism of CST, as in paroxysmal supraventricular tachycardia, is not univocal. Their electrophysiologic evaluation by means of endocavitary techniques can allow a more satisfactory therapeutic approach.

Adolescent↗
PubMed1976

[Morphological aspects and electrophysiological evaluation of the vectorcardiogram in inferior myocardial infarction (author's transl)].

The purpose of the paper is to evaluate the vectorcardiographic characteristics of the QRS in inferior myocardial infarction, now extended and modified in the light of recent advances in electrophysiology. The VCGs (Frank system) of 70 patients with old inferior myocardial infarction were analyzed. The most important parameters previously considered by others and the behaviour of the different vectorial groups were considered. The results of the analysis of these parameters were concordant with those obtained by others. The morphologic evaluation of the QRS on different planes allowed our cases to be divided into five vectorcardiographic groups. The evaluation of the morphological aspects of the QRS for a more sure diagnosis of myocardial infarction, specially considering false positive cases, was considered from the semeiological point of view. Moreover, it was shown that some alterations of VCG cannot be apparent electrocardiographically. The electrogenetic meaning of vectorcardiographic alterations, probably related with depth and width of necrosis and with conduction disturbances in the subdivisions of left bundle branch, were evaluated.

Adult↗