Main Answer:
The practitioner chose diltiazem to treat the patient's atrial tachyarrhythmia because b) diltiazem decreases the calcium influx into the atrioventricular (AV) nodal tissue and decreases the speed of impulse conduction.
Therefore, the correct answer is b).
Explanation:
Diltiazem, a calcium channel blocker, was selected by the practitioner due to its specific mechanism of action. In atrial fibrillation, the heart's electrical signals can become disorganized, leading to a rapid and irregular heartbeat. The AV node is a critical part of the heart's electrical system, responsible for regulating the transmission of signals between the atria and ventricles.
Diltiazem works by inhibiting the influx of calcium into the AV nodal tissue. This is crucial because calcium plays a significant role in the electrical conduction of the heart. By reducing the calcium influx, diltiazem slows down the conduction of impulses through the AV node. This, in turn, helps to control the rapid heart rate associated with atrial fibrillation.
Unlike options b and d, where calcium influx is increased into the AV nodal or myocardial tissue, diltiazem's action is beneficial in restoring a more normal rhythm. Furthermore, option c is incorrect as it describes an effect on myocardial tissue contraction strength, which is not the primary target in this scenario.
In summary, the choice of diltiazem is based on its ability to specifically modulate calcium channels in the AV nodal tissue, effectively slowing down the heart's electrical impulses and restoring a more regular heart rhythm in cases of atrial tachyarrhythmia.
Therefore, the correct answer is b).