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PubMed1977

[Disorders of intraventricular conductivity in primary myocardial infarct].

Recent knowledge of the system of intraventricular conductivity permits to diagnose much more often the different variants of blocks of the main branches of the bundle of His that develop in acute primary myocardial infarction (41.42%). Clinical and electrocardiographic examinations of 239 patients with acute primary myocardial infarction revealed unilateral conductivity disorders in the right ventricle in 19.24% of the cases, in the left ventricle -- in 13.39%, and bilateral conductivity disorders -- in 8.79%. The main branches of the bundle of His blocks were combined with atrioventricular conductivity disorders in 19 patients (20.21%), in 12 of them the atrioventricular block being a manifestation of bilateral intraventricular conductivity disorders. Patients with various conductivity disorders developed with significantly higher incidence other rhythm disorders (atrial flutter and fibrillation, paroxysmal tachycardia), which indicates to a close relationship between the functions of conductivity and excitation of the heart.

Acute Disease↗
PubMed1979

[State of the heart conduction system in the sick sinus syndrome (according to the recording of the bundle of His potentials and the atrial stimulation test)].

It was established that the presence of Samoilov-Wenckebach's periods and prolongation of the H--V interval at low frequency of the imposed rhythm as well as periods of asystolia of more than 1,200 msec are most typical for these patients. An attempt was made to determine the type of cardiac stimulation indicated for such patients from the character of the disorders of rhythm observed in them and the initial frequency of their own cardiac contractions.

Action Potentials↗
PubMed1979

[Treatment of severe ventricular arrhythmia by means of repeated cardiac stimulation].

The overdrive pacing method is widely used now in clinical practice for prevention and treatment of severe ventricular disorders of the cardiac rhythm. The mechanisms of arrhythmia suppression by means of this stimulation is analysed. Indications are determined for the choice of the site of stimulation and optimal impulce frequency in ischemic heart disease, and overdosage with digitalis drugs, as well as in myocardiopathy.

Adult↗
PubMed1977

Abnormalities of cardiac conduction in sinus node disease. Correlation with clinical findings.

His bundle recordings, sinus recovery time and the response to atropine were studied in 28 patients with symptomatic sinus node disease. The electrophysiological data were correlated with the clinical picture and the course of the disease. The marked prolongation of sinus recovery time and a decidedly diminished responsiveness to atropine may increase the accuracy of clinical assessment of the disease but negative results of these tests do not exclude even serious dysfunction of the node. The His bundle electrogram provides a more thorough evaluation of AV conduction and should be taken into account when permanent electrotherapy is being considered.

Adolescent↗
PubMed1976

'Supernormal' phase in hemiblock conduction.

A case is described where the basic sinus rhythms is associated with an advanced degree of left anterior hemiblock. The rhythm is complicated by atrial extrasystoles, associated with a lesser degree of left anterior hemiblock. This paradox of 'supernormality' is explained on a critical interplay of differential refractoriness within the divisions of the left bundle-branch.

Adult↗
PubMed1978

Electrophysiological properties of intravenous metoprolol in man.

Electrophysiological changes produced by intravenous (0.1 mg/kg) metoprolol, a new selective beta 1-blocking agent devoid of intrinsic activity, were studied in 16 subjects with estimated normal impulse formation and conduction. The most important effects were sinus bradycardia, mild increase of sinoatrial conduction time, depression of intranodal conduction, and prolongation of AV node refractory periods. Sinus node recovery time and atrial refractory periods were unmodified. Infranodal conduction and the refractory periods of the His-Purkinje system, as well as of the bundle-branches, were unchanged. These effects are compared with those observed after intravenous propranolol, pindolol, and oxprenolol.

Adult↗
PubMed1978

Mahaim conduction producing left axis deviation and normal QRS.

An unusual patient is described in whom electrophysiological studies strongly suggest the occurrence of Mahaim conduction. The patient whose electrocardiogram previously showed a left anterior hemiblock pattern then developed advanced atrioventricular (AV) block (AH block). Beats conducted through the atrioventricular node always had a short HV interval (20 ms) and QRS complexes of left anterior hemiblock pattern. Junctional escape beats always had a normal HV interval (50 ms) with normal intraventricular conduction. His bundle pacing showed the StV interval and QRS contour of escape beats. These findings suggest the existence of an accessory pathway (Mahaim fibres) passing from the area of block, presumably the uppermost portion of the His bundle, to the posteroinferior division of the left bundle-branch. The surface electrocardiogram did not show the characteristic delta wave of the Wolff-Parkinson-White syndrome. Our observations suggest that patients in whom there is conduction along Mahaim fibres may show only the pattern of intraventricular conduction defect without a delta wave.

Cardiac Complexes, Premature↗