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Biomedical subjects

C Guimond

Publications and source records attributed to C Guimond.

5 recordsLinked to original sources
PubMed1979

Computer processing of intracardiac electrograms for conduction studies.

Computer techniques developed to process intracardiac signals recorded in dogs are presented. The signals under measurement are the auricular and ventricular monophasic action potentials and the His bundle electrogram. Computerized measurement of significant timing parameters on simultaneous recordings of these signals can assess quite precisely changes in the normal conduction scheme of the heart provoked by different experimental protocols. Increased accuracy is mainly due to the objective way of defining wave onsets and the processing power of the system used. Signal recording, signal acquisition, automatic waveform measurements, interactive process and production of end result graphs by computer are all described.

Action Potentials↗
PubMed1978

[The supernormal phase of cardiac conduction. An experimental study in the dog].

The existence of a cardiac phase of supernormal excitability is not fully proved at the cellular level. As far as the whole heart is concerned, the phenomenon of supernormal conduction is still under discussion. Intracardiac conduction has been studied both in the right atrium (13 dogs) and in the right ventricle (14 dogs) by programmed stimulation (extrastimulus technique), while monophasic action potential (MAP) was recorded. The phenomenon of supernormal conduction was noted in 67.7% of cases, starting at 59.0% and ending at 78.0% of the basic cycle, hence occuring shortly after phase 3 of the MAP. In the ventricle, a phase of supernormal conduction was present in 52.4% of cases, starting at 66.1% and ending at 77.9% of the basic cycle. After ajmaline, the supernormal conduction was moved towards the end of the cycle. The mechanism of supernormal conduction, and its implications in the study of arrhythmias are discussed.

Action Potentials↗
PubMed1976

Intra-His bundle blocks (102 cases).

Some intra-His bundle (intra-HB) blocks escape the routine exploration of the His bundle and are confused with supra- or infrahisian blocks. We believe that a more accurate exploration (recording of His bundle activity successively at the proximal end and the distal end of the His bundle, dynamic tests and drug injection) is needed to detect some concealed cases, mostly paroxysmal intra-HB blocks. In this series of 102 cases of intra-HB blocks, 20% had no criteria of AV block on the surface electrocardiogram, and only 4% had an intact conduction pattern (normal PR interval and normal QRS complexes.) A first degree intra-HB block was found in 35% (15 cases with a normal PR interval), a second degree intra-HB block in 23% and a thired degree intra-HB block in 42% of the cases (unidirectional in 4 cases). Of the 43% having an isolated intra-HB block, most were elderly women with a chronic third degree AV block.

Adolescent↗
PubMed1976

[Analysis of the electrophysiological effects of amiodarone using simultaneous recordings of monophasic and bundle-of-his action potentials].

The effects of amiodarone given by rapid intravenous injection at a dosage of 10 mg/kg have been studied in the dog. The peak activity is found between the fifth and the tenth minute. The rate of discharge of the sinus is lowered by 36%. At the atrial level, the duration of the monophasic action potential (MAP) is increased by 9% and its dv/dt is lowered slightly, the total refractory period is increased by 22%, the effective refractory period is increased by 27%, the functional refractory period is increased by 19%, the ratio of the length of the effective period/duration of the MAP becomes slightly greater than unity, conduction facilitation disappears, and the period of slow conduction increases. In the A/V node the AH interval increases by 44% under normal rhythm, while atrial stimulation at 200/min. results in conversion to total AV block in more than half of the cases. The potential of the bundle of His and the HV interval are not altered. At ventricular level the duration of the monophasic action potential increases by 25%, its dv/dt decreases slightly, the total refractory period is increased by 8%, and the effective refractory period is increased by 14%.

Action Potentials↗