Heart 8 around the two ventricles and proceeding toward the apex. This complex swirling pattern allows the heart to pump blood more effectively. There are two types of cells in cardiac muscle: muscle cells which have the ability to contract easily, and pacemaker cells of the conducting system. The muscle cells make up the bulk (99%) of cells in the atria and ventricles. These contractile cells are connected by intercalated discs which allow a rapid response to impulses of action potential from the pacemaker cells. The intercalated discs allow the cells to act as a syncytium and enable the contractions that
Heart failure with preserved ejection fraction atrio-ventricular valves open (mitral valve at left side and tricuspid valve at right side) and the blood passes from the atria into the ventricles. First, ventricles are filled by a pressure gradient but near the end, atria contract (atrial kick) and force more blood to pass into ventricles. Atrial contraction is responsible for around 20% of the total filling blood volume. (In atrial fibrillation, this additional 20% filling volume is lost and the patient may experience systolic heart failure symptoms). Complete left ventricular filling is essential to maintain maximum cardiac output. Left ventricular filling is dependent upon ventricular relaxation and