In which patient population should myocarditis be suspected?

Myocarditis should be suspected primarily in patients who exhibit a rise in cardiac biomarkers combined with new or unexplained clinical findings. This is because myocarditis often presents with nonspecific symptoms such as chest pain, dyspnea, fatigue, or palpitations that may suggest cardiac involvement. The elevation of cardiac biomarkers, such as troponins, indicates myocardial injury, which, when paired with new or unexplained symptoms, strongly points towards the diagnosis of myocarditis.

In patients with a prior history of heart disease, while they may indeed present with myocarditis, this condition can affect individuals without a previously recognized cardiac issue as well. Similarly, having known infectious diseases does not necessarily correlate with myocarditis unless there are specific symptoms or biomarkers indicative of cardiac inflammation. Chronic lung disease can overlap with cardiac symptoms but is not a definitive indicator for myocarditis without presenting cardiac-specific signs or symptoms. Hence, option B provides a more comprehensive basis for suspecting myocarditis among patient populations, focusing on clinical evidence and diagnostic markers.