The effect of pacing-induced heart rate variation on longitudinal and circumferential regional myocardial function after acute beta-blockade--a cardiac ultrasound study.
OBJECTIVE
To evaluate the effect of acute beta-blockade in combination with differing heart rates on longitudinal and circumferential regional myocardial function using Doppler myocardial imaging and two-dimensional-echocardiography.


RESULTS
In seven pigs the following echocardiographic indices were measured at baseline, after beta-blockade both without and with atrial pacing: wall thickening fraction, fractional shortening, myocardial peak systolic velocity, transmyocardial velocity gradient and systolic velocity time integral of the posterolateral wall in short-axis view; mitral valve plane excursion, myocardial peak systolic velocity and systolic velocity time integral of the posterolateral wall in an apical five-chamber view. Peak systolic velocities and velocity gradients decreased significantly following acute beta-blockade but no further decay occurred at high heart rate due to pacing. The velocity time integrals and mitral valve plane excursion showed a tendency to decrease following beta-blockade but only after pacing were they significantly reduced. The wall thickening fraction and fractional shortening showed a significant reduction after beta-blockade but no further decay after pacing.


CONCLUSIONS
Changes in systolic velocities and velocity gradients were independent of heart rate reduction under high dosage beta-blockade, whereas wall thickening fraction, mitral valve plane excursion and velocity time integrals changed due to pacing.
Strotmann
J M
JM
Linköping Heart Center, University Hospital, Linköping, Sweden.
Janerot-Sjöberg
B
B
Kimme
P
P
Fröhlich
B
B
Voigt
J U
JU
Schreckenberger
A B
AB
Hatle
L
L
Sutherland
G R
GR
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D001783:Blood Flow Velocity; D004452:Echocardiography / Q000379:methods*; D006321:Heart / Q000033:anatomy & histology / Q000187:drug effects; D006439:Hemodynamics; D023421:Models, Animal; D009200:Myocardial Contraction / Q000187:drug effects*; D013552:Swine; D016277:Ventricular Function, Left / Q000187:drug effects* / Q000502:physiology*
D000319:Adrenergic beta-Antagonists