Which drug is most likely to cause suppression of arrhythmias resulting from a reentry focus?

The most suitable drug for suppressing arrhythmias arising from a reentry focus is one that converts a unidirectional block to a bidirectional block. The mechanism of reentry involves a circuit of electrical impulses that can be established when there is a unidirectional block within a pathway, allowing for the possibility of continuous re-excitation of the myocardial tissue.

When a drug is able to change this unidirectional block into a bidirectional block, it effectively halts the reentry circuit, thus stopping the arrhythmia. This capability is crucial in managing reentrant tachycardias because it directly targets the mechanism that sustains the arrhythmia.

Other options, while potentially beneficial in certain contexts, do not specifically address the mechanics of reentry arrhythmias. For example, medications with vagomimetic effects may reduce heart rate or influence AV node conduction, but they do not directly interrupt the reentry pathway. Similarly, beta-blockers can be helpful in general arrhythmia management but may not specifically convert the block type needed to resolve a reentrant circuit. Drugs that slow conduction through the atria can affect conduction velocity but do not address the underlying issue of reentry effectively.

Therefore, a drug that can convert a un