The procedure of heart surgery
After general anesthesia, the patient will be completely unconscious. The chest cavity is opened to reveal the heart, the tube connecting the heart to the artificial heart-lung machine, and blood is introduced into the artificial heart-lung machine to temporarily replace the human heart and lungs to sustain life with the help of the artificial heart-lung machine, and the patient’s heart and lungs can rest completely. The doctor injects a 4°C cardioplegic fluid into the heart vessels to stop the heart, lower its temperature and supply a certain amount of energy. The intracardiac surgery officially begins. The patient’s heartbeat and breathing are restored after the cardiac surgery operation is completed. After the situation is stabilized, the artificial heart-lung machine is stopped and the tube connecting the patient to the artificial heart-lung machine is removed. The procedure is completed. Take the patient safely to the post-operative cardiac care unit. I. Preface
The American College of Cardiology Foundation (ACCF), American Heart Association (AHA) Task Force on Clinical Guidelines has released the new 2011 edition of the CABG guidelines.
The guidelines were developed by the ACCF and the AHA in collaboration with the American Association for Thoracic Surgery (AATS), the American College of Thoracic Surgeons (STS), and the Society for Cardiovascular Anesthesia.
This new edition of the guidelines addresses the everyday issues and debates about PCI versus CABG that have been frequently addressed since the publication of the 2004 edition of the guidelines. As PCI techniques mature and operators gain experience, PCI is being used more and more.
For patients with left main or multibranch disease, the new edition emphasizes a “heart team” approach and gives Category I recommendations. For these patients, the interventional cardiologist is encouraged to discuss the patient’s condition and coronary anatomy with the cardiothoracic surgeon, evaluate the advantages and disadvantages of each treatment modality, and then provide the information to the patient along with the heart team’s recommendations. The new version of the guidelines also recommends the use of Syntax scores. Although calculating angiographic indications is complex, the Syntax score is used to assess the classification of coronary lesion severity and provides a more objective aid in selecting a treatment strategy.
The new CABG guidelines address the appropriate selection of bridge vessels, stopping and non-stopping CABG, the use of CABG in special patients with diabetes, and preoperative and postoperative antiplatelet therapy regimens.
Aspirin is applied preoperatively for CABG; clopidogrel is discontinued for at least 5 days before elective surgery is selected; in those requiring emergency surgery, it is discontinued for at least 24 hours if possible; and if aspirin is not used preoperatively, when it is used for at least 6 hours postoperatively and for a long time.
II. Top 10 points of the new CABG guidelines.
1. IMA should be used when possible when CABG is indicated in the anterior descending branch.
2. Transesophageal ultrasound should be used intraoperatively to evaluate acute, persistent, and life-threatening hemodynamic disturbances that are unresponsive to therapy, and concurrently for patients undergoing valve surgery.
3 Optimize factors that determine coronary perfusion (e.g., heart rate, arterial diastolic or mean pressure, and right or left ventricular end-diastolic pressure) to reduce the risk of perioperative myocardial ischemia and infarction.
4 Indications for performing emergency CABG in patients with acute myocardial infarction include: failure or inability to perform direct PCI; coronary artery anatomy suitable for CABG; and large areas of persistent myocardial ischemia and/or hemodynamic disturbances at rest that are ineffective for nonoperative treatment.
5 For patients with unprotected left main lesions or complex coronary artery disease, it is recommended that the “heart team” discuss revascularization treatment modalities.
6 Indications for CABG to improve survival include: severe stenosis of the left main stem; severe stenosis of three large coronary arteries with or without involvement of the proximal anterior descending segment; and lesions of the proximal anterior descending segment plus another large coronary artery lesion.
7 CABG or PCI should not be performed to improve symptoms in patients who do not meet the anatomy or physiology of revascularization therapy (i.e., abnormal flow fraction reserve).
8 If aspirin is not used preoperatively, it should be initiated 6 h after the procedure and used long-term to reduce the incidence of venous bridge vessel occlusion and adverse cardiovascular events.
9 If not contraindicated, all patients undergoing CABG should receive statin therapy to lower LDL cholesterol to <100 mg/dl).
10 For all patients after CABG, a cardiac rehabilitation program is recommended whenever possible.
III. CABG results during hospitalization
Knowledge of the possible early postoperative consequences is a top priority in the doctor-patient decision to perform CABG. It is especially important for the prediction of postoperative morbidity and mortality, as well as complications including cerebrovascular accidents, incisional infections, and renal insufficiency.
1. Hospital morbidity and mortality
It is reasonable to apply statistical hazard models to objectively assess the morbidity and mortality rate of CABG.
One study showed that 7 core preoperative variables could be used to predict postoperative morbidity and mortality-urgency of surgery, age, history of previous cardiac surgery, sex, EF, degree of left main stenosis, and number of branches of diseased vessels with stenosis greater than 70％.
There were also 13 primary variables: height, weight, PCI, MI, history of angina, ventricular rhythm, CHF/MR, diabetes mellitus, cerebrovascular disease, PVD, and creatinine level.
2. Post-CABG complications: neurological complications.
Type 1: generally more severe focal neurological damage, which may present with sensory loss or coma (stroke).
Type 2: characterized mainly by mental and memory loss (encephalopathy).
One study reported that type 1 and type 2 are almost equal, with a 2-fold longer average postoperative hospital stay and an even greater 6-fold increase in the likelihood of continued rehabilitation after hospital discharge.
Independent risk factors have been identified for its association: advanced age, especially over 70 or 70 years; history of hypertension.
Proximal aortic atherosclerosis is the strongest predictor of stroke after CABG. Intraoperative manipulation of the aorta dislodges atherosclerotic tissue and is the main cause of stroke.
[Prevention] Intraoperative palpation, selection of soft site for cannulation and block. uCG, CT or plain film evaluation. Non-ascending aorta cannulation. Surgery without aortic block and under ventricular fibrillation. Single-clamp technique. Ascending aortic replacement under stoppage of circulation.
Pre-existing neurological disease or comorbid diabetes mellitus.
3. Postoperative complications: mediastinitis.
Obesity and secondary surgery are associated with it; and the “Paris group” found the greatest association with obesity, probably as a result of a combination of factors such as skin folds, low distribution of antibiotics, bacterial media and deep trauma masking the disease.
The presence of diabetes is another factor, and in addition to microangiopathy, elevated blood glucose levels can also affect wound healing. Continuous intravenous insulin administration to control blood glucose below 200 mg/dL significantly reduces the incidence.
Secondary surgery requires additional tissue separation and prolonged operative time, thus promoting infection formation, especially in combination with factors such as diabetes and/or obesity.
In conclusion, post-CABG sternal infection is a costly to treat and potentially fatal complication.
[Prevention] Strict aseptic measures, shorten the duration of surgery, and do not overuse electrocautery. Use antibiotics appropriately. Control blood sugar level.
4. Postoperative complications: renal insufficiency
Postoperative renal insufficiency (PRD): postoperative serum creatinine level ≥2.0mg/dL or more than 0.7mg/dL higher than preoperative level.
Preoperative risk factors: advanced age, moderate to severe CHF, past CABG, type I diabetes mellitus, and pre-existing renal disease.
5. Post-discharge outcomes.
CABG surgery in patients who met the criteria provided relief of symptoms such as angina pectoris while extending life expectancy.
An analysis of one study identified advanced age, EF, current diabetes, number of diseased vessel branches, and gender as predictors that significantly affected postoperative survival; whereas angina classification, hypertensive disease, history of prior infarction, renal insufficiency, and congestive heart failure were other significant factors obtained from univariate analysis.
Adverse events after CABG tend to increase progressively between 5 and 10 years after surgery and are clearly associated with chronic occlusion of the venous bypass. Occlusion of the venous bypass occurs 10 years after surgery. This may contribute to late postoperative angina recurrence and is also the cause of death in approximately half of the patients who die from cardiac-related causes after surgery.
IV. Comparison of CABG with drug therapy.
Overall, the 10-year follow-up showed that patients who received CABG lived 43 months longer than those who received drug therapy; those with left main stem problems lived 193 months longer. Additional benefit was seen in patients with three-branch lesions and single or double-branch lesions involving the left anterior descending branch.
1. Site and severity of stenosis.
Obvious left main stem lesions were defined as angiographically demonstrated stenosis exceeding the lumen diameter; for equivalent left main stem lesions were defined as severe luminal stenosis in the proximal segments of the left anterior descending and gyral branches.
The mean survival for CABG and pharmacotherapy was about 13 years and 6.5 years.
2. Three branch lesions
The more severe the symptoms, the more the lesion tends to be in the proximal segment of the left anterior descending branch, and the worse the left ventricular function, the greater the surgical efficacy.
The relative risk is reduced at 5 years after three-branch surgery.
3. Proximal left anterior descending branch lesion.
Proximal stenosis of the left anterior descending branch has a significant prognostic impact. the relative risk at 5 years after CABG is reduced.
4. Left ventricular function.
Left ventricular systolic function has been an important predictor; the benefit of surgical revascularization is small in those with normal EF; the potential benefit of CABG is greater in patients with poorer left ventricular function and mild to moderate impairment of cardiac function. It is important to note that randomized trials have included patients with EF <0.35.
Over the past few years, noninvasive tests such as positron emission tomography (PET), radionuclide imaging or dobutamine tests have confirmed that systolic insufficiency is often not the result of myocardial infarction but rather the result of chronic hypoperfusion (myocardial hibernation). The more surviving myocardium, the greater the benefit of recanalization.
6. Symptoms/quality of life.
The assessment of symptom improvement and quality of life showed results consistent with those on survival. In addition to its impact on survival, CABG has two symptom-related indications: first, surgical relief of angina is superior to pharmacological treatment; it can also be used to reduce the occurrence of non-fatal outcomes such as infarction, heart failure and hospitalization.
At 5 years after treatment, the surgical group was less likely to take anti-anginal drugs, and at year 10, this difference was not significant, but patients with multiple lesions who underwent revascularization were less symptomatic, especially in patients with left ventricular insufficiency (EF <0.35) and severe angina. Therefore, perhaps because symptom relief is associated with surgical revascularization, surgical revascularization can still be received when medical treatment is ineffective.
V. Comparison of CABG with interventional therapy.
Although PTCA was initially used only for the treatment of single-branch lesions, with the advancement of technology and equipment and the accumulation of experience, its application has been extended to patients with multiple lesions. Generally speaking PTCA is less invasive and has shorter hospitalization and recovery time compared to CABG. However, it has shortcomings if used as the preferred treatment for coronary artery disease, including the management of restenosis at the lesion site and difficulty in achieving complete revascularization in patients with multiple lesions.
1. Review of randomized trials.
There have been many randomized clinical studies, and the BRAI trial (the Bypass and Angioplasty Revascularization Study) came closest to setting the standard. However, there are still important limitations that make it difficult to generalize their findings. This is due to two reasons, namely that the trial results cannot be applied to all patients with multiple vascular lesions. First, only 5％ or so patients with multivessel disease were enrolled in the trial. Second, the judgment of the internist may be a significant determinant of clinical outcome, as PTCA is commonly used in two-vessel lesions, whereas CABG is more commonly used in patients with three-vessel lesions.
2. Randomized outcomes.
(1) Recent outcomes
(1) The incidence of complications such as mortality and Q-wave myocardial infarction was lower in both groups, but slightly higher in CABG. CABG was required during the first hospitalization in patients initially randomized to PTCA, and nearly 20％ of those who received CABG within one year.
(ii) The cost and duration of hospitalization for PTCA was less than in the CABG group, but the two groups gradually approached each other over time.
(③Those who received PTCA were able to return to work earlier.
(iv) The degree of completed revascularization was higher in the CABG than in the PTCA group.
(2) Long-term results
(i) The difference in survival between the two groups was not significant. The latest results from BARI, the largest long-term follow-up trial with a mean follow-up of 7.8 years, confirmed the survival benefit of CABG due to the significant survival benefit of diabetic patients who underwent the procedure in the trial.
(ii) Most trials confirmed a low rate of angina recurrence after CABG.
(3) There was a significant difference between the two groups in terms of the need for follow-up treatment. the rate of follow-up treatment was 4-10 times higher in the PTCA group than in CABG. the early advantage of PTCA in terms of medical expenditure was reduced in the long-term follow-up because of the higher frequency of need for relapse treatment and rehospitalization.
(3) Comparison with stents
(i) ARTS trial: no difference in the rates of death, myocardial infarction, and stroke at 1 year after the two revascularization treatments; savings of nearly $3,000 after stenting, but a higher rate of need for revascularization after stenting; no difference in event-free survival between the two groups in diabetic patients, but a significant difference in the rate of revascularization treatment.
(ii) The SOS trial reported similar clinical results.
(iii) In the SIMA trial, there was no difference in the rate of death, infarction, cardiac function or quality of life changes between the two groups at 2.4 years of follow-up.
(4) Aspects of special subgroups
The BARI trial was preemptively divided into four subgroups for analysis based on angina severity, disease extent, left ventricular function and lesion complexity, and there was no difference in survival primary trial endpoints between the groups.
The overall morbidity and cardiac mortality rates after PTCA treatment were higher in diabetic patients than in CABG.
(5) Results from registry data of non-randomized trials.
A non-randomized observational study comparing the long-term outcomes of CABG and PTCA found that patients with diabetes requiring insulin therapy had decreased long-term survival after multi-vessel PTCA therapy.
Survival benefit from CABG was seen in either single, double, or triple lesions. In patients with three-branch lesions without lesions in the proximal segment of the left anterior descending branch, CABG also provides more benefit than PTCA; for those with a single branch, PTCA is more advantageous.
(6) Conclusion
In randomized trials, CABG provides more effective relief of angina symptoms and requires less follow-up treatment.
CABG has more early complications, is more costly, and has a longer hospital stay.
PCI patients can return to work soon after treatment but then seek medical care frequently, so the total long-term costs are close to those of CABG.
CABG is more beneficial for diabetic patients.
PCI has more benefit in patients with single-branch lesions without severe stenosis in the proximal segment of the left anterior descending branch.
For those with severe, proximal left anterior descending stenosis and/or triple-branch lesions, CABG may prolong their life.
During disease progression, many patients will benefit from the combination of interventional and surgical procedures due to the lower incidence of comorbidities with intervention and the long-term benefits of surgical arterialized bypass.
VI. CABG treatment strategies
1. Reduce perioperative mortality and morbidity
(1) Low cardiac output.
(2) Postoperative stroke: one of the most catastrophic complications in CABG, classified as type I and type II injury. Atherosclerosis plays a dominant role.
2. Reduce the risk of perioperative myocardial insufficiency
A tightly scheduled, technically sound, and clean procedure is a recipe for risk reduction.
(1) Myocardial protection for acute impaired cardiac function, such as cardiogenic shock and acute coronary obstruction.
(2) Myocardial protection in chronic cardiac insufficiency.
(3) Elevated cardiac enzymatic markers and consequences.
(4) Other myocardial protection measures, such as IABP prophylactic application.
(5) Application of IMA.
(6) Timing of surgery for right ventricular and inferior wall myocardial infarction.
3. Reduction of systemic complications of extracorporeal circulation
Glucocorticoids, peptidase inhibition.
4. Reduce the risk of perioperative infection
(1) All patients should be given preoperative antibiotics.
(2) Continuous intravenous insulin infusion and aggressive control of hyperglycemia can reduce the risk of deep sternal infection.
(3) When deep sternal infection is still uncomplicated, active surgical debridement should be performed and muscle flap transfer should be used to cover the wound and restore blood flow early.
5. Prevention of postoperative cardiac arrhythmias
(1) Routine application of β-blockers without contraindications before or early after CABG can reduce the incidence of atrial fibrillation.
(2) Amiodarone may also reduce the incidence of postoperative AF, and digoxin and verapamil are useful for controlling the ventricular rate.
6. Strategies to reduce perioperative bleeding and blood transfusion.
7. Antiplatelet therapy to keep the venous graft bypass open.
Aspirin. Resorcinolide, etc.
8. Pharmacological treatment of hyperlipidemia.
Unless contraindicated, all patients with CABG should be treated with statin drugs.
LDC-C <100mg/dL is the treatment target.
9. Application of hormones
Application is not recommended for female patients.
10. Smoking cessation.
11. Cardiac rehabilitation
For all CABG patients, as long as they are eligible, rehabilitation guidance should be provided. This includes early walking, moderate exercise, family education, etc.