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Biomedical subjects

G Oreto

Publications and source records attributed to G Oreto.

At least 91 records · Page 5Linked to original sources
PubMed1987

Non-sustained ventricular tachycardia with Wenckebach exit block.

A case of non-sustained, recurrent ventricular tachycardia, manifesting with irregular R-R intervals, is described. Analysis of a long electrocardiographic recording reveals that the arrhythmia is generated by a regularly discharging ectopic ventricular focus, the R-R interval variations being due to a Wenckebach form of exit block.

Adult↗
PubMed1987

Concealed ventricular quadrigeminy linked to atrial quadrigeminy: a manifestation of modulated parasystole.

Analysis of a long electrocardiographic recording including many atrial and ventricular extrasystoles shows that when atrial extrasystoles are in a quadrigeminal distribution, the ventricular extrasystoles also manifest a quadrigeminal distribution or reflect a distributional pattern of concealed quadrigeminy. Conversely, when atrial extrasystoles are other than in a quadrigeminal distribution, the ventricular extrasystoles do not occur in a quadrigeminal or concealed quadrigeminal distribution. This pattern is explained on the basis of modulated parasystole. A biphasic phase-response curve explains the observed phenomena on the basis of variations of the parasystolic cycle length due to the modulating effect of supraventricular beats.

Aged↗
PubMed1987

Changes in morphology of the paced QRS complex related to atrial contraction.

A patient with 2:1 AV block underwent temporary ventricular pacing. All the paced stimuli resulted in ventricular capture, but a marked variability in morphology of the paced QRS complexes occurred. Two different types of paced QRS complex (labeled A and B) were recognized. Type B complexes were manifest only when the pacing stimulus was preceded by a sinus P wave within a time interval ranging from 0.15 to 0.52 sec. The P wave-induced changes in morphology of the paced QRS complexes were interpreted as due to displacement of the pacing ventricular lead caused by atrial systole.

Aged↗
PubMed1987

[Effects of propafenone on arrhythmias induced by exertion in patients with ischemic cardiopathy].

The efficacy of Propafenone to prevent exercise-induced ventricular arrhythmias (EIVA) has been studied in eleven patients affected by ischemic heart disease. None of the patients manifested any arrhythmia at rest, but ventricular arrhythmias occurred in every case during a treadmill test. EIVA disappeared after Propafenone in nine patients, while a reduction by 90% was achieved in the remaining two patients. A further treadmill test carried out five days after withdrawal of the drug induced again the same ventricular arrhythmias in all the patients. Thus, Propafenone appears effective to prevent EIVA in patients with ischemic heart disease.

Aged↗
PubMed1986

Modulated ventricular parasystole as a mechanism for concealed bigeminy.

Concealed extrasystolic ventricular bigeminy reflects a distributional pattern of ventricular extrasystoles where intervening sinus beats are always in odd numbers. This has been explained on bigeminal rhythm associated with exit block. This presentation reflects a modification of this concept in that the distributional pattern may be explained on the basis of complex concealed modulation of ventricular parasystole, the concealment being due to impulses falling within the refractory period rather than suffering true exit block.

Adult↗
PubMed1986

Supernormal modulation of ventricular parasystole: the triphasic phase-response curve.

Modulation of ventricular parasystole by sinus beats has been shown both in vitro and in vivo to result in a classic biphasic phase-response curve. The first clinical presentation of 3 cases of supernormal modulation of ventricular parasystole resulting in a triphasic phase response curve is reported. Supernormal modulation reflects an unexpected early enhancement expedition of the ectopic ventricular impulses. An alternative explantation for the triphasic phase-response curve is the discharge and resetting of the parasystolic focus by critically timed sinus impulses.

Adult↗
PubMed1986

Wedensky facilitation. Electrotonic potentiation during complete A-V block.

The electrocardiogram recorded from a patient with third degree A-V block reflected almost regular A-V junctional escape rhythm. Some of the R-R cycles were slightly shorter than the basic escape cycle. A QRS complex ending such a relatively short R-R interval was always preceded by a sinus P wave, and had a QRS configuration which was minimally different from that of the escape complexes. The His bundle recording demonstrated that these minimally premature complexes were associated with an H-V interval which was shorter than that of the escape complexes. This indicates that the premature QRS complex could not be a capture beat. The relationship between the slightly premature QRS complex and the preceding sinus P-waves is explained on the basis of electrotonic potentiation or modulation to due Wedensky facilitation.

Aged↗
PubMed1986

[The linking phenomenon in tachycardia-dependent intraventricular block].

Seven cases of tachycardia-dependent, or phase-3, intraventricular block have been examined. Analysis revealed a constant overlap between the range of the R-R intervals ending in normal conduction and the range of the R-R intervals where the second beat is associated with intraventricular block. The block, indeed, may occur at the end of relatively long R-R intervals, whereas R-R intervals which are shorter (up to 0.11 sec) can unexpectedly result in normal intraventricular conduction. A relatively late QRS complex, however, can reflect an intraventricular block only when the preceding complex also manifests the block. This phenomenon has been interpreted as due to the so called "linking", namely the retrograde concealed penetration of an anterogradely blocked bundle branch by the impulse traversing the controlateral bundle branch. This delays the activation of the affected bundle branch, whose refractory period is, accordingly, "shifted to the right" within the cardiac cycle. A relatively late sinus impulse, thus, can result in intraventricular block since the refractory period of the affected bundle branch ends later, with respect to the beginning of the QRS complex, than it does after a normally conducted sinus impulse.

Bundle-Branch Block↗
PubMed1985

Asynchronous intraventricular recovery as a basis for apparent 'supernormality'.

Various mechanisms have been postulated for the supernormal phase of intraventricular conduction where relatively early impulses are conducted with normal intraventricular conduction and relatively late impulses with abnormal intraventricular conduction. The cases presented here illustrate how asynchronous recovery of conducting tissue may result in fortuitous momentary synchrony early on in the recovery phase with asynchronous conduction properties in the later phases of recovery. This will facilitate potential synchronous conduction early on in the cycle which would result in a normal QRS complex, and potential asynchronous conduction in the later phases which would manifest with a bundle branch block QRS complex.

Aged↗