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Variability in the Measurement of Human Ventricular Refractoriness
Author(s) -
KADISH ALAN H.,
SCHMALTZ STEPHEN,
MORADY FRED
Publication year - 1991
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1991.tb02885.x
Subject(s) - refractory period , medicine , reproducibility , cardiology , anesthesia , statistics , mathematics
The degree of variability in ventricular refractoriness and factors potentially affecting this variability were evaluated in 80 patients undergoing an electrophysiological study. Each of seven variables fstimulation current, coupling interval of the basic drive train to spontaneous rhythm, pause between determinations, bipolar pacing configuration, bipolar vs unipolar pacing, atrioventricular synchrony, and autonomic tone) was evaluated in a group of ten patients to determine its effects on the reproducibility of refractoriness. Measurements were repeated ten times in every patient under each of two conditions. Five variables had significant effects on the reproducibility of measurements. Pacing at 10 mA was associated with less variability in the determination of ventricular refractoriness than pacing at twice threshold (within‐subject variance component 4.5 vs 10.1 msec; P < 0.001). The mean difference between the longest and shortest determinations of refractory periods (range) was 6.2 msec at 10 mA and 8.6 msec at twice threshold. The use of a conditioning period of pacing and continuous trains (eight beats with a 3‐sec pause) rather than a variable pause between serial trials reduced the mean within‐subject variance component from 16.5 to 3.3 (P < 0.001) and the mean range of refractory period determinations from 10.8 to 4.8. The use of the distal rather than the proximal pole as the cathode decreased the mean within‐subject variance component from 9.4 to 3.3 (P < 0.001) and the range of determinations from 6.4 to 5.8 msec. Unipolar pacing was associated with less variability than bipolar pacing (mean within‐subject variance component 4.6 vs 6.4; P < 0.05, mean range 5.0 vs 7.6 msec). In patients with ventriculoatrial dissociation, atrioventricular simultaneous pacing during the basic drive train decreased the within‐subject variance component from 21.2 to 5.7 (P < 0.001) and the mean range of refractory periods from 12.2 to 6.8 msec (P < 0.05). In an eighth group of patients, the significant variables were set to create either the greatest or least variability in refractoriness in order to determine the effects of controlling these factors. Bipolar pacing was used in this group of patients. The within‐subject variance component decreased from 31.7 to 3.5 (P < 0.01) and the mean range of refractory period determinations decreased from 15.8 to 4.4 msec (P < 0.01) when the variables found to affect the reproducibility of refractoriness were set in a fashion to decrease variability. In conclusion: (1) Conventional measurement of ventricular refractoriness often is associated with variability in the range of 10–15 msec (2) Pacing at 10 mA, unipolar rather than bipolar pacing, atrioventricular synchrony during basic drive trains, a large number of trains before refractoriness is reached, and bipolar distal cathodal pacing decrease this variability and provide greater reproducibility in the measurement of ventricular refractoriness.