A weak pulse may cause shortness of breath, which may be caused by heart failure or aortic stenosis. 1. Heart failure: Due to heart failure, the contractility of the heart muscle decreases and the heart pumps less blood to the periphery, causing a weaker pulse. A large amount of blood pools in the left atrium and the lungs, causing stagnation of the lungs and impaired gas exchange, which causes shortness of breath. 2. Aortic stenosis: During the systolic phase of the heart, the blood in the left ventricle cannot be pumped to the periphery in time due to the narrowing of the aorta, resulting in a weaker pulse, and similarly, the blood pooling in the lungs causes shortness of breath. If weak pulse and shortness of breath occur, it is recommended to go to the hospital in time to get a clear diagnosis and standardized treatment under the guidance of the doctor.