Emperor Hirohito's doctors said Monday the 87-year-old monarch's strong heart helped him survive repeated losses of blood, massive transfusions and a life-threatening drop in blood pressure the previous day.

Hirohito's condition worsened Sunday to its lowest point since the monarch first fell seriously ill six weeks ago, but he endured the crisis and was again listed in stable condition Monday."The doctors say it is clear the emperor can suffer a large blood discharge and endure it well," said Kenji Maeda, the chief palace spokesman.

Early Sunday, court physicians - battling a large overnight loss of blood - gave Hirohito nearly three pints of new blood, nearly half his body's normal blood supply.