The adrenal medulla develops from neural tissue and secretes two hormones, epinephrine and norepinephrine. These two hormones are secreted in response to stimulation by sympathetic nerve, particularly during stressful situations. A lack of hormones from the adrenal medulla produces no significant effects.
While the sinoatrial node typically regulates the heartbeat during normal sinus rhythm, PACs occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat.
Some cases of trigeminy PVCs are just ânormal variantsâ which may occur in normal healthy persons. 1  Other causes of trigeminy PVC are listed below: 2  Abnormal quantities of minerals or electrolytes in the bloodstream. Low levels of magnesium and/or potassium are the usual anomalies associated with electrolytes.