Acute heart failure is due to the sudden onset of abnormalities in the structure and function of the heart, resulting in a significant, sharp decrease in short-term internal blood output, inadequate perfusion of tissues and organs and acute venous stasis in the backward direction of the affected ventricle. Acute left-sided heart failure examination methods Arterial blood gas analysis: there can be obvious oxygen saturation reduction, carbon dioxide content is normal or decreased, pH>7.0. 1, X-ray chest X-ray can be seen in the lung door with butterfly-shaped flaky shadows and expanding around the lung edema signs, the heart boundary is enlarged, the apical beat is weakened, and so on. 2.Electrocardiogram Sinus tachycardia or various arrhythmias, myocardial damage, left atrial and left ventricular hypertrophy.