Ventricular pump function under ectopic excitation of the frog heart
Kibler, N.A.; Belogolova, A.S.; Vaĭkshnoraĭte, M.A.; Azarov, I.E.; Shmakov, D.N.
Rossiiskii Fiziologicheskii Zhurnal Imeni I.M. Sechenova 94(2): 176-183
2008
ISSN/ISBN: 0869-8139 PMID: 18516848 Document Number: 616023
The ventricular pump function under ectopic excitation of the heart was studied in decapitated and pithed adult frogs Rana temporaria (n = 21) at 18-19 degrees C. The intraventricular pressure was recorded with a catheter via ventricular wall. During pacing of the ventricular base and apex, the systolic pressure decreased (6.1 +/- 4.5 mm Hg and 8.9 +/- 5.0 mm Hg, respectively) as compared to the supraventricular rhythm (8.9 +/- 5.0 mm Hg, p < 0.05). The end-diastolic pressure decreased insignificantly both under basal and apical pacing. The systolic rate of pressure rise during dP/dtmax decreased under ventricular pacing, especially during pacing of the ventricular apex, as compared to the supraventricular rhythm (14.4 +/- 6/9 mm Hg/s and 22.1 +/- 11.2 mm Hg/s, respectively, p < 0.003). The isovolumetric relaxation (dP/dtmin) slowed during apical pacing as compared to the supraventricular rhythm (-25.1 +/- 13.6 and -35.6 +/- 18.3 mm Hg/s, respectively, p < 0.03). Ectopic excitation of the ventricular base and apex resulted in increase of the QRS duration (93 +/- 33 ms and 81 +/- 30 ms, respectively) as compared to the supraventricular rhythm (63 +/- 13 ms, p < 0.05). Thus, pacing of different ventricular areas ventricular myocardium with the ventricular pump function being reduced more obviously during the apical pacing compared to the pacing of ventricular base.