Answer:
The correct option is : e. Positive inotropic agents
Step-by-step explanation:
The heart muscles or the cardiac muscles have a natural ability to contract. This is known as myocardial contractility.
The myocardial contractility can be increased by increasing the influx or maintaining high levels of the calcium ions, during an action potential, in the cytosol of the cardiac myocytes. One of the mechanisms to increase the contractility of cardiac muscles is by the administration of the drugs having positive inotropic effect.
Therefore, the Positive inotropic agents increase the contractility of cardiac muscle.