Pneumonia causes heart failure in three ways: 1. The toxins produced by the pathogens that cause pneumonia directly invade the heart, causing secondary myocarditis and heart failure. 2. Pneumonia is particularly severe when it damages the interstitial lung, causing ventilation and air exchange dysfunction, further causing right heart insufficiency. 3. Pre-existing cardiac insufficiency such as coronary heart disease, cardiomyopathy, on top of pre-existing heart failure or hidden heart failure, in After the lung infection, it causes increased oxygen consumption and poor oxygen supply, which further causes and induces the aggravation of heart failure.