New York Heart Association (NYHA) Class II heart function is not severe. Myocardial infarction is a relatively serious type of coronary heart disease, which occurs due to the blockage of the coronary arteries leading to myocardial necrosis, and it carries certain risks. It can ultimately lead to complications such as sudden death and heart failure. At this stage, with Class II heart function, symptoms of heart failure can appear under conditions of significant exertion, including chest tightness, breathlessness, fatigue, and shortness of breath. These symptoms correspond to a relatively less severe stage of heart failure.