Right and left atrial diameters during incremental atrial pacing in pigs.
The relationship between right and left atrial diameters and heart rate was examined in 14 open-chest barbiturate-anesthetized pigs by an ultrasonic technique. The maximal atrial diameter was read at the top of the v wave, which decreased in both atria when heart rate was increased from 124 (118-130) to 159 (156-160) (median and 95% confidence interval) beats/min. Right and left atrial maximal diameter fell significantly from 25.7 (23.6-32.6) to 24.9 (22.9-29.5) mm and from 30.8 (25.1-37.2) to 29.8 (23.4-36.3) mm, respectively, when heart rate was increased from 124 to 180 (177-182) beats/min. At higher pacing frequencies, both right and left atrial maximal diameter progressively increased, and at 220 (216-221) beats/min the maximal diameter regained the values obtained at 124 beats/min. The minimal atrial diameter, which was read at the end of the a wave, remained unchanged at heart rates below 180 beats/min but rose significantly at higher rates. Our findings indicate progressively reduced atrial filling with increasing heart rate and hampered atrial emptying and atrial distension at the highest heart rates.
Leistad
E
E
Institute for Experimental Medical Research, University of Oslo, Ullevaal Hospital, Norway.
Christensen
G
G
Ilebekk
A
A
D000818:Animals; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation; D003971:Diastole; D005260:Female; D006321:Heart / Q000033:anatomy & histology / Q000502:physiology*; D006325:Heart Atria; D006339:Heart Rate; D006439:Hemodynamics; D008297:Male; D011312:Pressure; D013552:Swine; D013997:Time Factors