The AV node delays the signal before it is passed to the ventricles. viagra generic Because blood isn't pumped out of these chambers fully, it may pool and form clots that could lead to a stroke. viagra generic A major part of the electrical system in the heart that acts as a gateway between the atria and the ventricles. viagra generic An electrical signal generated by the sinoatrial node the heart's natural pacemaker moves through the heart until it reaches the atrioventricular node, a cluster of cells at the bottom of the right atrium. viagra generic There are two of these—the right atrium and the left atrium.