Biology — Cardiac Cycle

digraph Cardiac {
  rankdir=LR;
  node [shape=box, style=rounded];
  "Atrial systole" -> "Ventricular systole" [label="AV valves close"];
  "Ventricular systole" -> "Ventricular diastole" [label="semilunar valves open"];
  "Ventricular diastole" -> "Atrial systole" [label="filling"];
}