Final answer:
A first-degree AV block is indicated by a prolonged PR interval on an ECG and often requires no treatment if asymptomatic. Electrolyte levels and an echocardiogram should be checked to rule out underlying conditions. A third-degree AV block necessitates the use of an artificial pacemaker to maintain heart rate.
Step-by-step explanation:
AV blocks are a type of heart arrhythmia characterized by a delay in the conduction of electrical impulses through the heart's atrioventricular (AV) node. In a first-degree AV block, there is an abnormally long PR interval on an electrocardiogram (ECG), indicating slowed conduction through the AV node, but no missed beats. It's commonly an incidental finding and usually requires no treatment if the patient is asymptomatic. However, it's important to check electrolytes and perform an echocardiogram to rule out any underlying issues.
A more severe third-degree AV block presents a complete dissociation between atrial and ventricular activity, with the heart relying on a slower junctional or ventricular rhythm maintained by the AV node or ventricular pacemakers. In such cases, an artificial pacemaker might be necessary to maintain effective cardiac output and prevent symptoms such as dizziness or syncope associated with a significantly reduced heart rate.