The chick embryo heart as an experimental setup for the assessment of myocardial remodeling induced by pacing.
The mechanisms regulating remodeling of the heart are not well understood and only rarely investigated for pacing. We therefore developed a model based on the well-established chick embryo heart preparation. Hamburger Hamilton 21 stage Leghorn chick embryos were used. Access to the heart was obtained after having dissected the shell membranes. The electrodes (platinum wires) were placed in ovo: the anode on the vitelline membrane and the cathode at different sites of the heart (sinus venosus, base/apex of the ventricle). Sensing and stimulation thresholds were measured. Survival of the paced chick was studied. Among 30 chick embryonic hearts, the stimulation thresholds were 1.4 mV +/- 0.5 SD for the atrium, 2.6 V +/- 1.4 SD at the base, and 3.2 V +/- 1.5 SD at the apex of the ventricle, while the sensing signals were 1.3 mV +/- 0.5 SD at the atrium, 19.6 mV +/- 4.1 SD at the base, and 21.6 mV +/- 3.9 SD at the apex of the ventricle. Continuous pacing (pacing rate = intrinsic rate + 10%) could be maintained for 1.5 hours +/- 0.5 SD at the atrium, 8.9 hours +/- 0.7 SD at the base of the ventricle, and 7.9 hours +/- 1 SD at the apex of the ventricle up to death of the embryos. By using intermittent electrical stimulation, the association of 5 minutes on/5 minutes off pattern during 18 hours and 5 minutes on/15 minutes off, during 30 hours resulted in an effective pacing period of 19 hours in 60% of the experiments, reflecting 15 cell turnover cycles. This experimental setup will allow the study of morphological, metabolic, and molecular bases of ventricular remodeling induced by electrical stimulation.
Grobéty
M
M
Division of Cardiology, University of Lausanne, Switzerland.
Sedmera
D
D
Kappenberger
L
L
D000818:Animals; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D002642:Chick Embryo; D006339:Heart Rate; D006352:Heart Ventricles / Q000196:embryology; D008452:Maximum Allowable Concentration; D009200:Myocardial Contraction; D016276:Ventricular Function; D020257:Ventricular Remodeling / Q000502:physiology*