I. Concept.
Coronary artery atherosclerotic heart disease (CAD) is referred to as coronary heart disease, mostly develops in middle age or above, and the morbidity and mortality rate is significantly higher in men than in women. Coronary atherosclerosis is a manifestation of systemic atherosclerosis involving the coronary arteries, mainly affecting the main trunk of the coronary artery and its proximal branches, with a higher incidence in the anterior descending and ileal branches of the left coronary artery than in the right coronary artery. The result is a narrowing of the coronary artery lumen, which leads to acute myocardial ischemia and myocardial necrosis due to the combination of coronary artery spasm and thrombosis. The procedure is called coronary artery bypass graft (CABG), in which an autologous vessel is used as bypass graft material to bypass the narrowed or occluded coronary artery and restore myocardial blood supply to the ischemic area.
II. Clinical manifestations.
1. The typical clinical symptom of coronary artery disease is episodic angina, which is pain in the precordial region, suffocating, squeezing sensation, and radiating to the left shoulder and left upper limb or even the neck or upper abdomen. The duration of the pain can last for minutes or hours; it is accompanied by cold sweats. The symptoms of chest pain can be relieved after using crown-dilating drugs such as nitroglycerin. Some patients show epigastric pain, tightness in the throat, or even toothache.
2, clinical typing of angina pectoris for exertional angina and spontaneous angina pectoris two categories. The chest pain of exertional angina is related to the amount of exercise and the increase in myocardial oxygen consumption, and can be divided into stable exertional angina, incipient exertional angina, worsening exertional angina, and prone angina. Spontaneous angina is defined as an attack of angina without a fixed relationship with increased myocardial oxygen consumption. In mild spontaneous angina, the electrocardiogram shows a decrease in the ST segment during the attack. There are also variant angina pectoris.
3. Sometimes patients may also present with acute myocardial infarction as the first manifestation, and patients have severe pain in the precordial region and a sense of near death. The clinical manifestation of local myocardial ischemia is angina pectoris, and with the aggravation of coronary artery disease, the local myocardial blood supply can be completely stopped. If no good collateral circulation is established, local myocardium can develop ischemic necrosis. The clinical presentation is acute myocardial infarction or acute ventricular septal perforation. Acute left heart or total heart failure occurs, and then the blood pressure drops to present cardiogenic shock.
4. Very few patients can present with invisible chronic myocardial infarction, leading to cardiac enlargement and chronic heart failure. Another clinical manifestation of coronary artery disease can be sudden death. Some patients may also present with arrhythmias.
5. There are no specific signs. It is possible that some patients may present with low heart sounds. If myocardial infarction is present and causes hemodynamic changes in the heart, there can be corresponding clinical features. This includes the presence of systolic murmur of septal perforation; pericardial friction sounds of pericardial exudation after myocardial infarction, etc.
III. Diagnosis.
1. A preliminary diagnosis can be made by taking a medical history, understanding the symptoms and physical examination.
2. For patients suspected of having coronary artery disease, all relevant ancillary examinations should be performed: including chest radiograph (CXR), electrocardiogram (ECG, myocardial ischemic changes or myocardial infarction changes), cardiac ultrasound (UCG, ventricular wall motion incoordination) and lipid glucose, cardiac enzymology, troponin and ambulatory blood pressure test, etc.
3.If the above test results suggest, further proposed nuclear myocardial perfusion scan (myocardial perfusion mismatch), coronary angiography (CAG) and other tests are needed.
4. The diagnosis of coronary artery disease must be confirmed by all the above auxiliary examinations, in addition to the differential diagnosis with aortic valvular heart disease, primary hypertrophic obstructive cardiomyopathy, coronary artery origin anomaly or coronary artery fistula, arteritis Kawasaki disease and other diseases involving coronary artery and coronary artery myocardial bridge.
IV. CABG surgery
At present, the treatment of coronary artery disease can be divided into three categories: medical drug treatment (nitrates, blockers, calcium antagonists), interventional treatment (such as PTCA, endovascular stenting, laser angioplasty, plaque spinotomy) and surgical treatment. Among them, surgical treatment is mainly the application of coronary artery bypass grafting (CABG, referred to as “bypass”) to reconstruct blood transport channels for ischemic myocardium, improve blood and oxygen supply to myocardium, relieve and eliminate angina symptoms, improve myocardial function and prolong life span. In recent years, interventional treatment for coronary artery disease is advancing rapidly, and PTCA or more advanced interventions are preferred for most patients with mild disease, single or double-branch lesions. Patients screened for CABG will be predominantly those with severe, multibranch lesions or reoperation, thus increasing the difficulty and risk of surgical procedures. In recent years, the clinical trial of laser myocardial perforation and blood flow reconstruction and stem cell transplantation for necrotic myocardium have been effective in improving myocardial blood supply, relieving and alleviating symptoms, and now we continue to observe and study them.
1. Indications for surgery: CABG is mainly indicated for angina pectoris that cannot be relieved by medical treatment and affects work and life, with significant stenosis of the main trunk or major branches of the coronary artery (narrowing of the vessel diameter by more than 50%, i.e., reduction of the lumen area by more than 75%) found by CAG, with unobstructed blood flow at the distal end of the stenosis (the diameter of the coronary branch at the donor anastomosis is above 1.5mm), and with left heart catheterization and Left ventriculography showed good left ventricular function (EF > 30%). The site and degree of coronary stenosis, the condition of the vessels distal to the stenosis, the systolic function of the left ventricle and the presence of ventricular wall aneurysm must be clarified by CAG before the proposed CABG procedure.
(1) Left main or left main-like lesions with stenosis greater than 50%.
(2) Three branch coronary artery lesions with stenosis greater than 75%.
(3) Coronary artery lesions combined with impaired left ventricular function, where myocardial revascularization can improve symptoms and cardiac function.
(4) Myocardial infarction complicated by ventricular wall tumor, septal perforation, mitral regurgitation, etc. requiring simultaneous surgical correction.
(5) Those with restenosis or complications after interventional therapy.
(6) Those with unstable angina pectoris with frequent episodes and the possibility of myocardial infarction
(7) Severe left main lesion with angina pectoris and risk of sudden death.
(8)Acute myocardial infarction with severe complications with hemodynamic instability such as septal perforation, etc., where medical treatment is ineffective or frequent angina attacks after myocardial infarction.
(9) Acute myocardial ischemia, drop in blood pressure or intractable rhythm disturbances during PTCA, who have failed medical interventions such as IABP support.
(10) Acute myocardial ischemia in the perioperative period of CABG and complications of interventional therapy, which include coronary artery dissection and coronary artery rupture bleeding caused during CAG or PTCA.
2. Preoperative preparation: Preoperative comprehensive assessment of the patient’s cardiac function, systemic condition and lesion characteristics of each coronary artery branch, adequate improvement of cardiac function, correction of arrhythmias and various infection prevention measures should be taken. For patients with coronary artery disease, we should emphasize the psychological treatment and mental preparation before surgery to reduce the occurrence of myocardial infarction.
(1) Improve the preoperative examination of extracorporeal circulation, including the patient’s liver, kidney and respiratory function, carotid artery vascular condition, and saphenous vein condition of the lower limbs. If the radial artery needs to be selected as the bypass vessel material, Allen’s test should be performed preoperatively.
(2) Preoperative treatment includes controlling myocardial oxygen consumption (controlling blood pressure and heart rate) and increasing myocardial perfusion. For this purpose, many patients take preoperative beta-blockers, calcium channel blockers, ACEIs and nitrates, which can be used until the day of surgery.
(3) Preoperative patients taking platelet-acting anticoagulants such as aspirin and Bolivar should be discontinued for more than 5 to 7 days in those undergoing elective surgery. During the discontinuation period, if anticoagulation is required for unstable angina, subcutaneous injection of low-molecular heparin can be used.
(4) Pulmonary function tests are routinely performed in patients. This test should be avoided in patients with severe left mainstem lesions and angina pectoris that is difficult to control with medications.
(5) Sleeping medication is given the night before surgery if there is no contraindication (e.g. respiratory sleep apnea syndrome); a small amount of sedative medication can also be given on the day of surgery to reduce the increase in myocardial oxygen consumption due to mental stress.
3, surgical methods: good surgical magnification, cold light source headlamp, microsurgical instruments and a complete re-vascularization surgical plan are the most basic conditions for successful surgery.
(1) Ascending aortic block using extracorporeal circulation technique, CABG under cardiac arrest: currently chosen by most cardiac surgeons worldwide.
(2) Normothermic, CABG under non-stop cardiac arrest (Off-Pump CABG, OPCAB): suitable for certain combined respiratory insufficiency, renal insufficiency, carotid stenosis, severe atherosclerotic plaque in ascending aorta and other high risk factors of extracorporeal circulation.
(3) The classic surgical route for CABG is via median sternotomy, in addition to parasternal incision and small incision of the lower sternal segment.
(4) The bypass vessels used as CABG include the left internal mammary artery, right internal mammary artery, great saphenous vein, small saphenous vein, radial artery and the less frequently used gastroretinal artery, inferior abdominal wall artery, cephalic vein and splenic artery.
(5) In cases of multiple or/and multiple coronary artery stenoses, a single saphenous vein or internal thoracic artery can be used for sequential or serpentine end-lateral and lateral anastomosis with several adjacent stenotic vessels.
(6) Complications caused by myocardial infarction such as ventricular wall tumor, ventricular septal perforation, and mitral valve insufficiency due to papillary muscle or tendon rupture can also be treated surgically, such as ventricular wall tumor resection, septal perforation repair and mitral valve replacement, etc., and coronary artery bypass grafting can be performed at the same time according to the situation.
(7) Coronary artery restenosis after surgery can also be treated with another or three surgeries.
(8) In addition, small incision coronary artery bypass grafting (MIDCAB), thoracoscopy-assisted coronary artery bypass grafting (video-assisted CABG), closed extracorporeal circulation coronary artery bypass grafting (port-acces CABG), etc. are also available.
4.Surgical complications: the same as general direct cardiac surgery, postoperative maintenance of blood volume and electrolyte balance, adequate artificial assisted ventilation and prevention of infection. Special emphasis is placed on adequate postoperative sedation and control of blood pressure not to be too high; intravenous nitroglycerin to improve coronary artery blood supply; timely management of arrhythmias, especially ventricular rhythm disturbances; early anticoagulation in patients with coronary artery endarterectomy or diffuse lesions in coronary arteries.
(1) Myocardial ischemia during surgery (perioperative myocardial infarction) is mainly related to the patency of the bypass vessels. Active observation of ECG and, if necessary, myocardial enzymology and ultrasound assessment of left ventricular systolic changes are measures to detect perioperative myocardial ischemia as early as possible.
(2) Perioperative arrhythmias, the most common of which is postoperative atrial fibrillation, occur in approximately 22% to 30% of patients, especially in advanced age. Ventricular arrhythmias.
(3) Neurological complications, with up to 5% to 6% reported.
(4) Bleeding and cardiac tamponade.
(5) Other still pulmonary complications and deep vein embolism, mediastinal infection, renal failure, poor healing of lower limb incisions, hypertension, diabetes mellitus, etc.
5, surgical results: the clinical efficacy of CABG has been very positive, of course, and the condition and surgical techniques and other factors related to the general 30%-35% of patients after CABG symptoms completely disappeared, 75%-90% of patients angina pectoris significantly reduced, 4%-6% deterioration. The operative mortality rate is also influenced by a variety of factors, with large groups in many medical centers currently reporting operative mortality rates in the range of 1%-3%. Mortality is significantly higher in those with preoperative left ventricular insufficiency and ejection fraction below 30%. Survival after surgery is related to the degree of recanalization, number of branches, patient age, and other factors. The usual survival rates at 5 and 10 years after CABG alone are 79% to 88% and 52% to 66% or even higher.
(1) Risk factors for CABG include advanced age greater than 70 years, female, repeat CABG, emergency CABG, low left heart function especially left ventricular ejection fraction (EF) less than 25% with congestive heart failure, left main stem lesions, and diffuse coronary artery three-branch lesions.
(2) Risk factors that may increase early postoperative mortality include pathological Q-wave myocardial infarction less than 30 days old, combined with other organ dysfunction (diabetes, end-stage renal insufficiency, chronic obstructive pulmonary disease, peripheral vascular obstructive disease, etc.), and failure to use the internal mammary artery (internal thoracic artery).
(3) The long-term patency of the bypass vessels is currently considered to be best matched for bypass of the internal mammary artery-left anterior descending branch. 90% of internal mammary artery to anterior descending branch bypasses remain patent at 10 and 20 years postoperatively. Radial artery patency at 4 to 7 years was 83%, but this was related to whether the target coronary artery stenosis was greater than 70%. The 5-year and 10-year patency rates for saphenous vein bypass are 74% and 41%, respectively; however, if the saphenous vein is anastomosed with an anterior descending branch, the 5-year patency rate can be as high as 81%.
6.Postoperative precautions.
(1) Postoperative anticoagulation therapy should be paid attention to. For patients with poor conditions of distal coronary vessels or poor conditions of bypass vessels found intraoperatively and with little chest drainage fluid 3 hours after surgery, subcutaneous injection of low-molecular heparin (such as Speedy Bilin, Faanming) can be given as early as possible for anticoagulation. Postoperatively, enteric aspirin 50 mg/d to 100 mg/d is routinely given to patients without severe peptic ulcer (intravenous bridges are better with aspirin than without it). Pansentine can also be given orally at the same time in the early postoperative period (within 3 months).
(2) When atrial fibrillation occurs after surgery, it can be eliminated by removing the triggers of atrial fibrillation such as hypovolemia and low arterial perfusion pressure for those who are hemodynamically stable. Since a rapid ventricular rate leads to increased myocardial oxygen consumption, the ventricular rate can be reduced by intravenous administration of (cortolone) amiodarone injection, beta-blockers, etc.
(3) Due to the possibility of perioperative myocardial ischemia, early attention is paid to controlling blood pressure and heart rate. Use β-blockers, (Pell) nicardipine hydrochloride injection, and Heshinshang. Early intravenous pumping of nitroglycerin. If the selected bypass vessel includes the radial artery, calcium blockers (e.g., Hepcentrate, nicardipine, etc.) should also be added.
(4) In case of reactive hypertension and stressful hyperglycemia after surgery, they should be controlled aggressively with antihypertensive drugs and insulin.
(5) It is recommended to have a comprehensive checkup 3 months to 6 months after surgery, and timely review and adjustment of drug treatment plan.
(6) The long-term patency rate of postoperative bridge vessels is related to the patient’s lipid level, and a low-fat diet and anti-lipid therapy if necessary are recommended after surgical recovery.