冠心病是指冠状动脉供血不足引起的心脏病变，它是一种常见的心血管疾病。冠心病患者在运动或剧烈活动时往往感到呼吸困难，这是由多种因素共同作用导致的。

首先，冠心病引起的心肌供血不足会导致心肌缺氧。冠状动脉狭窄或堵塞使得氧气和营养物质无法充分供应给心肌细胞，从而导致心肌功能下降和心脏泵血能力减弱。当人体进行剧烈活动时，心脏需要更多的氧气来满足身体的需求。而冠心病患者的冠状动脉已经受损，无法提供足够的血液和氧气，造成心肌供氧不足，进而引起呼吸困难。

Secondly, the inadequate blood supply to the heart muscle caused by coronary heart disease can lead to a decrease in cardiac output. The heart plays a vital role in pumping oxygenated blood to different parts of the body. In individuals with coronary heart disease, the narrowed or blocked coronary arteries limit the amount of oxygen-rich blood that the heart can pump. As a result, the body may not receive enough oxygen during physical exertion, leading to shortness of breath.

同时，冠心病也会引起心肌功能下降。患者的心脏在负荷增加时无法有效地收缩和放松。这导致血液在心脏内积聚，进而使心脏扩大，肺静脉压力增加。当肺静脉压力升高时，液体可能从肺部渗出到肺泡中，导致肺水肿。肺水肿是肺部功能异常的病态表现，可以引起呼吸困难和咳嗽。

Moreover, the presence of underlying conditions such as hypertension and heart failure in coronary heart disease patients can further exacerbate breathing difficulties. High blood pressure can lead to increased afterload on the heart, making it harder for the heart to pump blood effectively. This can cause fluid to accumulate in the lungs, leading to congestion and difficulty breathing. Similarly, heart failure is characterized by the heart's inability to pump blood efficiently, resulting in fluid build-up in the lungs and respiratory distress.

另外，在冠心病患者中，通常会合并其他呼吸系统疾病，如支气管哮喘和慢性阻塞性肺疾病（COPD）。这些疾病会导致气道狭窄和肺功能下降，加重冠心病患者的呼吸困难。因此，在诊断和治疗冠心病时，同时应对这些并发症进行管理，以减轻患者的呼吸困难症状。

In addition, coronary heart disease patients often have concurrent respiratory conditions such as bronchial asthma and chronic obstructive pulmonary disease (COPD). These conditions can cause airway constriction and decreased lung function, further exacerbating breathing difficulties in individuals with coronary heart disease. Therefore, in the diagnosis and treatment of coronary heart disease, it is important to manage these comorbidities simultaneously to alleviate respiratory symptoms in patients.

总而言之，冠心病患者在运动或剧烈活动时感到呼吸困难是由多种因素综合作用导致的。心肌供氧不足、心脏功能下降、高血压、心衰以及并发的呼吸系统疾病都可能促使呼吸困难的发生。因此，冠心病患者需要定期接受医学检查和治疗，以便及时缓解症状、减轻负担，并提高生活质量。

In conclusion, the respiratory difficulties experienced by coronary heart disease patients during exercise or strenuous activities result from a combination of factors. Insufficient oxygen supply to the heart muscle, decreased cardiac function, hypertension, heart failure, and concurrent respiratory conditions all contribute to the occurrence of breathing difficulties. Therefore, regular medical examination and treatment are essential for coronary heart disease patients to alleviate symptoms, reduce burden, and improve quality of life.