Which cardiac condition might Verapamil NOT be indicated for?

Verapamil is a calcium channel blocker that is commonly used to treat various cardiac conditions, primarily due to its ability to decrease heart rate and reduce myocardial oxygen demand. In cases of stable angina, atrial flutter, and supraventricular tachycardia, Verapamil is typically indicated because it helps to manage these conditions by slowing down the heart rate and facilitating better blood flow.

However, in the case of heart block, the use of Verapamil is not appropriate. Heart block refers to a disruption in the conduction pathways of the heart, which can lead to delays or complete interruptions between the atria and ventricles. Using a medication like Verapamil, which further slows down the conduction through the atrioventricular (AV) node, can exacerbate the existing block. This can lead to serious complications such as complete heart block or even cardiac arrest. Thus, due to its mechanism that reduces conduction velocity, Verapamil is contraindicated in patients with heart block, making it the correct answer in this scenario.