1 Introduction

Under normal circumstances, the sinus node of the right atrium of the human heart can automatically and rhythmically emit electrical impulses, and the cardiac nerve conduction system sends instructions to various parts of the heart, causing the heart muscle to contract, the heart beats, and pumping blood to the whole body. If the myocardial nerve conduction system is impaired or the sinus node and the sinus node can not regularly emit electrical impulses or lower electrical impulses, the heart will have arrhythmia or even stop, which will endanger the patient's life. The artificial cardiac pacemaker can give direct electrical stimulation to the diseased heart as needed, artificially making the heartbeat normal. The artificial cardiac pacemaker can be divided into two types: external temporary pacing type and implantable type (or permanent or buried type). The former is for first-aid temporary pacing, and the latter is for long-term pacing treatment. This article focuses on implantable artificial cardiac pacemakers, which are general pacemakers.

2. Principle and construction of artificial cardiac pacemaker

An artificial cardiac pacemaker is a very sophisticated and highly reliable electrical impulse stimulator that is fitted with a pacing pulse generator of a certain type, connected to a special wire (ie, a pacing catheter electrode), and pacing. electrode sends electrical pulses to stimulate the heart, can not be excited or poor conduction and pacing cardiac stress medical electronic equipment.

The artificial cardiac pacemaker is mainly composed of the following two parts:

(1) pacing catheter electrode: on the one hand, the output signal of the pacemaker is directed to the myocardium for pacing, and on the other hand, the signal that senses the heart's own pulsation (intraluminal electrocardiogram ICG) is fed back to the pacemaker to control The release of the beat pulse. It is an endocardial electrode that has evolved from an early unipolar to bipolar or even multipolar. The catheter electrode used as a long-term pacing must be made of a material that is biocompatible, tough, resistant to aging, and corrosion. The electrode lead is usually wound with a coil of Elgin or with a nickel-chromium-cobalt-molybdenum alloy wire. The outer insulating material of the wire is made of high-purity silicone rubber or medical polyurethane. The material of the electrode tip is preferably surface-activated isotropic low-temperature pyrolysis of carbon or platinum.

(2) Pace pulse generator: It consists of a pacing circuit, a battery, and a metal casing. The energy of the pacemaker needs to be a small volume, large capacity, slow release energy, good sealing performance and reliable performance. Currently, implantable pacemakers at home and abroad generally use lithium-iodine batteries to make the pacemaker's continuous service life. It has been more than 10 years. Since the titanium metal has good biocompatibility and no rust, the current pacemaker casing is stretched by titanium material, and the various parts of the body are connected by a large arc, and are packaged by laser welding. Since the 1980s, pacing circuits have generally used integrated circuits to manufacture the main circuit of pacemakers; and CMOS ASIC pacing chips are mounted on ceramic substrates together with electronic components such as resistors, capacitors, and reed switches to form a hybrid type. (Hybrid) thick film integrated circuits are standard components of pacing circuits.

3. Indications for artificial cardiac pacemakers

(1) High or complete atrioventricular block with Ac A syndrome or syncope. Asymptomatic, heart rate <50 beats / min or QRS wide deformity and ventricular arrest > 2 seconds for relative indications.

(2) Complete or incomplete three bundles and double bundle branch block with intermittent or paroxysmal complete atrioventricular block, or ventricular rate <4O beats / min; double bundle branch block with A-Syst Syndrome or syncope author; alternating left and right bundle branch block, His bundle diagram confirmed HV prolongation.

(3) Second degree type II atrioventricular block with A. syndrome or syncope. Continuous second-degree type II atrioventricular block, ventricular rate <50 times / min and asymptomatic relative indications.

(4) Sick sinus syndrome has the following manifestations: severe sinus bradycardia, ventricular rate <45 beats / min, severely affect organ blood supply, heart failure, angina pectoris, dizziness, black; bradycardia, sinus Static or sinus block, RR interval > 2 seconds with syncope or A-S syndrome; bradycardia - tachycardia syndrome with syncope or A-S syndrome.

(5) with anti-tachycardia pacemaker or automatic cardioverter defibrillator, ectopic tachyarrhythmia drug treatment is invalid.

(6) Recurrent carotid sinus syncope and ventricular arrest.

4. History and current status of artificial cardiac pacemakers

The widespread clinical application of artificial cardiac pacemakers has resulted in the treatment of severe arrhythmia patients who have failed medical treatment in the past, which has greatly reduced the mortality of cardiovascular diseases. It is a major contribution of modern biomedical engineering to human beings.

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