Cardiology Category

Such a similarity does not mean that the velocities of the electrical and mechanical propagations are identical. Indeed, in addition to the conduction velocity, the excitation-contraction coupling as well as the rate ofcross-bridge cycling could also vary from one region to another along the heart tube . Nevertheless, our results indicate clearly that it is […]

The embryonic heart was reoxygenated under stop-flow conditions and, consequently, was not accompanied by a washout of metabolites accumulated during anoxia. This makes our experimental protocol different from that generally used in ischemic-reperfused isolated hearts. Indeed, no reflow accompanied reoxygenation; nevertheless the embryonic ventricle stopped contracting, showing that this mechanical failure (oxygen paradox) was due […]

The kinetics of response of the embryonic heart to anoxia and reoxygenation was much slower than the diffusion kinetics of oxygen obtained by computer simulation. This finding shows clearly that the pattern of response observed during deprivation and readmission of oxygen depends essentially on cellular mechanisms rather than diffusional processes. Myocardial function and oxygen availability: […]

The myocardial tissue was sufficiently protected against possible extracellular acidosis resulting from successive anoxia-reoxygenation cycles. Indeed, taking into consideration the buffering capacity of the culture medium and the production of protons resulting from the metabolic activity of the whole heart at stage 20, ie, about 6 nmol O2/h , the external pH would decrease by […]

PO2 within the embryonic myocardium during anoxia-reoxygenation transitions: Two major findings resulted from the mathematical model of oxygen diffusion and consumption. First, under normoxic steady state, myocardial PO2 was 17 and 8 kPa in the most superficial (facing gas compartment) and in the deepest (facing lower glass window) cellular layers, respectively. Second, the deepest layers […]

The Pv determined along the ventricle wall was 62.0±9.2 mm/s (n=3) under normoxia and was not significantly affected by anoxia or reoxygenation. Although the ventricle separated from atrium and conotruncus was able to contract spontaneously and regularly at a rate of 62±7 beats/min (n=5), no ventricular ectopic beats were observed in the isolated intact heart. […]

 Reoxygenation after 40 s of anoxia did not immediately restore the normal myocardial contractility but resulted in significant disturbances of mechanical activity. Indeed, the ventricle stopped contracting (oxygen paradox), relaxed and then progressively recovered contractile activity. The duration of this arrest was related to the duration of the preceding anoxia (Figure 4). Within about 1 […]