What is the most likely diagnosis for a 45-year-old male with an irregular rhythm and pulse rate of 110 bpm?

The most likely diagnosis is atrial fibrillation. This condition is characterized by an irregularly irregular heart rhythm that often leads to a rapid pulse rate, which in this case is 110 bpm. Atrial fibrillation occurs when the electrical signals in the atria become chaotic, causing the atria to quiver instead of contract effectively. As a result, the heartbeat becomes irregular and can be accompanied by palpitations, shortness of breath, or fatigue.

In this scenario, the patient's age also supports the likelihood of atrial fibrillation, as it is more common in individuals over 65 but can occur in younger patients due to various risk factors such as hypertension, heart disease, or lifestyle factors. The irregular rhythm and elevated pulse rate strongly point towards this diagnosis, particularly in the context of a wide range of patients who might present with similar symptoms.

Other options like ventricular fibrillation, while also serious, present with more extreme symptoms, including loss of consciousness and are usually identified in emergency scenarios, not in an outpatient setting. Cardiac arrhythmia is a broad term that encompasses all types of irregular heartbeats and is not specific enough to identify the condition accurately. A first-degree right bundle branch block typically presents with a consistent rhythm but with a