Sudden cardiac failure is a syndrome that occurs when the heart function decreases beyond its compensatory function due to the aggravation of heart disease (heart failure is a group of syndromes caused by various structural or functional heart diseases that lead to impaired ventricular filling and/or ejection capacity. The clinical manifestations are mainly dyspnea, weakness and limited physical activity and edema. (Treatment of the disease should include prevention and delay of the onset of heart failure, relief of the symptoms of clinical heart failure, improvement of its long-term prognosis and reduction of mortality). The diagnosis of sudden loss of cardiac function is based on the following: 1. Symptoms (1) accelerated heart rate and reduced cardiac output, early cardiac insufficiency, compensatory acceleration of heart rate, although it helps to increase cardiac output to normal or near normal levels, however, the accelerated heart rate also increases myocardial oxygen consumption, and coronary artery blood supply and ventricular filling time is shortened, and the volume of blood per beat decreases cardiac output instead. (2) Water and sodium retention and reduced cardiac output cause redistribution of blood and reduced renal blood flow. The decrease in renal blood flow can cause a decrease in glomerular filtration rate or an increase in renin secretion, which in turn acts on angiotensinogen produced by the liver to form angiotensin Ⅰ. Angiotensin I passes through the pulmonary and renal circulation and, under the action of converting enzymes, forms tubotensin II, which, in addition to causing systemic and small renal artery spasm and aggravating renal ischemia, also induces the adrenal cortex to secrete more aldosterone, increasing sodium retention and plasma osmolality, stimulating the osmotic pressure receptors near the supraoptic nucleus of the hypothalamus and reflexively increasing the secretion of antidiuretic hormone in the posterior pituitary gland, thus causing sodium, water This causes sodium and water retention, increased blood volume, venous and capillary congestion, and increased pressure. (3) Increased end-diastolic pressure of the ventricle. In heart failure, myocardial contraction is weakened, heart beat output is reduced, residual blood volume in the ventricular cavity is increased, end-diastolic pressure of the ventricle is elevated, venous return is obstructed, causing venous stasis and increased venous pressure. When the increase in intracapillary hydrostatic pressure exceeds plasma osmotic pressure and tissue pressure, intracapillary fluid extravasates and tissue edema occurs. 2.An ambulatory ECG is a method that can continuously record and compile and analyze changes in the ECG of the heart in the active and quiet states for a long time. It is also called Holter monitoring. Dynamic electrocardiogram (DCG) can record all abnormal waves and detect all kinds of arrhythmias and asymptomatic myocardial ischemia in various states within 24h, providing an accurate and reliable basis for the diagnosis of various heart diseases. In clinical application, it has a high detection rate especially for early coronary artery disease. 3.Electrocardiogram The heart is excited by the pacing point, atria and ventricles successively in each cardiac cycle, accompanied by bioelectrical changes, and the graph of various forms of potential changes induced from the body surface by electrocardiographic tracers is called electrocardiogram (abbreviated as ECG). ECG is an objective indicator of the process of occurrence, propagation and recovery of cardiac excitation. ECG is an important tool to help determine whether the electrical activity of the heart is normal, and it is the earliest, most commonly used and basic diagnostic method in the diagnosis of coronary heart disease.