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 min of reoxygenation, all the investigated parameters recovered their pre-anoxic values.Atrioventricular propagation of contraction during anoxia-reoxygenation transitions: Figure 5 shows typical simultaneous recordings of the mechanical activity at the atrial and ventricular levels as well as the instantaneous atrioventricular delay due to propagation of contraction. This delay increased progressively during anoxia and almost doubled when ventricle activity resumed during reoxygenation. Thus, taking into consideration the actual distance between the two selected regions (ie, 0.82±0.13 mm, n= 3), the value of Pv was 12.0±4.7 mm/s (n=3) under normoxia. Interestingly, propagation was specially slowed down at the resumption of ventricular activity when Pv reached a minimal value of 6.1±2.8 mm/s (n=3). In contrast to the ventricle, the atrial region generally did not cease to contract at reoxygenation.

Response of the embryonic heart to hypoxia and reoxygenation: An in vitro model

Figure 4 Relation between duration of ventricular arrest upon reoxygenation and duration of preceding anoxia. Reoxygenation did not induce ventricular arrest after anoxia shorter than 20 s. Data are means ± SEM; Numbers of hearts investigated are shown in parentheses You can always be sure whenever you cialis professional it is going to be one enjoyable and great experience overall, since you can now choose yourself a perfect pharmacy that will give you best quality medications with no prescription required.

Response of the embryonic heart to hypoxia and reoxygenation: An in vitro model

Figure 5 Atrioventricular propagation of contraction along the heart tube. a Contractions recorded simultaneously at the level of atrium and ventricle during an anoxia (N2) -reoxygenation (AIR) transition. Reoxygenation resulted in an atrioventricular (AV) block lasting 18 s. The instantaneous AV delay, reported on the same time scale, increased during anoxia and reached its greatest value when ventricular activity resumed during reoxygenation. The actual distance between the selected regions in atrium and ventricle was 0.95 mm, and the preanoxic AV propagation was 11 mm/s. Note that atrial shortening recoveredfaster than ventricular shortening. b Selected parts of the recording in panel a at a larger scale showing individual atrial (A) and ventricular (V) contractions. During each cardiac cycle, the strong ventricular contraction was mechanically transmitted to the atrium, which provoked a characteristic peakfollowing that of the atrial contraction. This peak disappeared during AV block