Cardiac Surgery: Techniques, Indications, and Outcomes

Posted on Sep 11, 2024 in Biology

Cardiac Pulmonary Bypass (CPB)

Definition

Diversion of blood away from the heart and lungs, an integral component of cardiac surgery.

Indications

  • Period of asystole
  • Inadequate cardiac output (e.g., requiring ventricular assist device – VAD)
  • Lungs cannot maintain appropriate physiological gas exchange

Types

  1. Total CPB: Routine for cardiac surgery.
  2. Partial CPB: Blood flow maintained in the right atrium, right ventricle, and pulmonary circulation. The heart is still beating, and the patient is ventilated.

Myocardial Protection

Principle

  • Decrease metabolic rate by hypothermia.
  • Heart muscle arrest by cardioplegia.

Cardioplegia Solution

  • Potassium-induced arrest and asystole.
  • Hypothermia achieved by cold solution.
  • Contains K+, HCO3-, Ca2+, glucose.
  • Crystalloid and blood cardioplegia types.

Goals:

  • Creation of a quiescent operative field.
  • Provide reliable protection against ischemia/reperfusion injury.
  • Arrest times of more than 4-5 hours can be tolerated without irreversible damage.

Methods

  • Infusion types: Antegrade, retrograde, combined.
  • Infusion temperature: Tepid, warm, cold.
  • Infusion intervals: Continuous, intermittent.

Complications of CPB

GeneralCardiovascularRenalRespiratory
  • Ischemia
  • Embolism
  • Infection
  • Neuropsychiatric
  • Exacerbation of pre-existing conditions
  • Myocardial ischemia
  • Vascular dissection caused by cannulation
  • Acute kidney failure
  • Acute respiratory distress syndrome (ARDS) due to neutrophil activation
  • Left lung collapse
Hematological
  • Consumption of coagulation components
  • Platelet aggregation
  • Anemia due to blood loss

Surgical Treatment of Ischemic Heart Disease

ClinicalAnatomical
  • Stable angina pectoris with maximal medical therapy
  • Unstable angina
  • Post-myocardial infarction (MI) angina
  • Unsuccessful percutaneous transluminal coronary angioplasty (PTCA)
  • Mechanical complications of MI
  • Left main stenosis > 50%
  • Triple vessel disease with impaired left ventricular (LV) function
  • Triple vessel disease with normal LV function but inducible ischemia
  • Two vessel disease (proximal left anterior descending artery stenosis)
  • Severe LV impairment with reversible ischemia
  • Coronary artery disease (CAD) prior to other surgeries

Methods for Surgical Coronary Revascularization

Coronary Artery Bypass Grafting (CABG) (On-Pump)CABG (Off-Pump)
  • Performed with cardiac arrest
  • CPB machine used to maintain circulation
  • Safe procedure with low complication rate
  • Complications include stroke, kidney failure, cognitive dysfunction, and bleeding
  • Performed on a beating heart
  • No CPB machine used
  • Special devices stabilize the relevant part of the heart
  • Complications similar to on-pump CABG
  • No superior benefit to on-pump CABG

Complex Heart Surgery

Definition

Involves either multiple procedures on the heart or procedures on the heart and other parts of the body.

Considerations

  • Type and location of machinery to be utilized for different procedures.
  • Order of progression of procedures (e.g., valvular repair before CABG).
  • Calculating the surgical risk for patients during complex surgery.

Aortic Valve Surgery

Methods and Results

Valve ReplacementValve Repair
  • Replacement with prosthesis (mechanical or bioprosthetic)
  • Composite graft of aortic valve (Bentall’s operation)
  • 1-year survival 70% in healthy patients
  • Percutaneous Interventions:
  • Aortic balloon valvuloplasty
  • Transcatheter aortic valve implantation (TAVI)
  • Patch repair or closure of perforation
  • Central or free margin plication
  • Leaflet repair (shortening or elongation)
  • Triangular resection
  • Aortic valve annulus remodeling
  • Aortic valve sparing surgery in aortic aneurysm correction of sinotubular junction

Mitral Stenosis Surgery

Valve ReplacementPercutaneous Intervention
  • With or without sparing of the subvalvular apparatus
  • Results: 15-year survival 80% (tissue valve) and 98% (mechanical valve)
  • Balloon mitral valvuloplasty
  • Results: Similar to commissurotomy but less invasive
Valve Repair
  • Commissurotomy (10-year survival 90%)
  • Annular decalcification

Mitral Regurgitation Surgery

Valve ReplacementValve Repair
  • Anterior leaflet resection with posterior leaflet and chordal preservation
  • Valve implant (15-year survival 80% tissue, 98% mechanical)
  • Posterior leaflet repair (quadrangular excision)
  • Anterior leaflet repair
  • Leaflet perforation repair (primary closure or with patch)
  • Annuloplasty
  • Repair of papillary muscle or chordae tendineae
  • Results: 10-year survival 70-90%

Aortic Aneurysm Surgery

Indications, Methods, and Results

IndicationSurgical Method
Ascending Aorta:
  • Symptomatic expanding aneurysm > 5.5 cm
  • Aneurysm > 4.5 cm if aortic regurgitation is present
  • Acute Type A dissection
  • Mycotic aneurysm
Transverse Arch:
  • Ascending aorta aneurysm extending into the arch
  • Acute arch dissection
  • Size > 6 cm
Descending Aorta:
  • Symptomatic aneurysm
  • Size > 6 cm
  • Complicated Type B dissection
Ascending Aorta:
  • Supracoronary interposition graft if sinuses of Valsalva are not involved
  • Bentall’s operation in patients with Marfan syndrome or annuloaortic ectasia
Transverse Arch:
  • Hemiarch repair if ascending aorta and proximal arch are involved
  • Extended arch repair with placement of interposition graft and reimplantation of brachiocephalic vessels
Descending Aorta:
  • Interposition graft placement
  • Consider femoral-femoral bypass to ensure spinal cord and kidney perfusion

Aortic Dissection

Indications for Surgery

  • Type A dissection
  • Type B: Complicated dissection with aortic rupture, intractable chest pain, or visceral ischemia

Surgical Treatment and Results

Type AResults (Type A)
  • Excision of intimal tear
  • Obliteration of entry into the false lumen
  • Aortic valve replacement if aortic valve disease is present
  • Bentall procedure when sinuses of Valsalva are dilated
  • 5-year survival 70%
  • 10-year survival 50%
Type BResults (Type B)
  • Interposition graft
  • Stenting
  • 5-year survival 60-80%
  • 10-year survival 40-80%

Heart Surgery Complications (CABG & Valves)

EarlyLate
Arrhythmias:
  • Causes: Damage to cardiac anatomy, extracardiac nerves, electrolyte imbalance, hypovolemia
  • Diagnosis: Electrocardiogram (ECG), electrolyte panel
  • Treatment: Electrolyte repletion, cardioversion, cardiac pacing
Bleeding:
  • Causes: Prolonged operation, deep hypothermia, renal impairment, anticoagulants
  • Treatment: Depends on cause (e.g., vitamin K, frozen plasma, protamine sulfate)
Neurological:
  • Stroke: Due to microemboli
  • Neurocognitive dysfunction: Transient
  • Diagnosis: Computed tomography (CT) scan, clinical examination
  • Treatment: Optimize cerebral blood flow
Cardiac Tamponade:
  • Causes: Fluid or blood accumulation in the pericardium
  • Diagnosis: Echocardiogram, chest X-ray
  • Treatment: Pericardiocentesis
Infection:
  • Causes: CPB, prosthetic material, respiratory equipment
  • Diagnosis: Complete blood count (CBC), culture
  • Treatment: Empirical antibiotics followed by specific antibiotics
Postoperative Fever:
  • Cause: Infection, inflammation
  • Treatment: Antibiotics for infection, nonsteroidal anti-inflammatory drugs (NSAIDs) for inflammation
Hypertension:
  • Cause: Occurs in 40-50% of patients following CPB
  • Diagnosis: Blood pressure measurement
  • Treatment: Antihypertensive medications
Renal Failure:
  • Treatment: Discontinue nephrotoxic medications, maintain urine output, dialysis
Respiratory Failure:
  • Causes: Mucous plugging, respiratory tube obstruction, pulmonary edema, atelectasis
  • Diagnosis: Arterial blood gas analysis
  • Treatment: Oxygen therapy, bronchodilators
Low Cardiac Output:
  • Cardiac index < 2.0 L/min
  • Signs: Decreased urine output, acidosis, hypothermia
  • Diagnosis: Heart rate, cardiac output monitoring
  • Treatment: Stabilize heart rate and rhythm, optimize volume status, correct acidosis
Other Late Complications:
  • Thrombosis
  • Embolism
  • Arteriovenous fistula

Pericarditis: Indications for Pericardiocentesis, Biopsy, and Drainage

Indications for Pericardiocentesis

  1. Emergent: Life-threatening hemodynamic changes or cardiac tamponade.
  2. Non-emergent: Diagnostic purposes, palliative care, prophylaxis.

Pericardial Biopsy

  • Indicated in cases of recurrent tamponade, suspected neoplasm, or suspected granulomatous disease.

Drainage of Pericardial Effusion

  • Immediate drainage is mandatory for cardiac tamponade to prevent hemodynamic collapse. Surgical or percutaneous drainage may be used.
  • Elective drainage should be performed for pericardial effusions that persist unchanged or increase in size during medical treatment.

Surgical Treatment of Pericarditis

Acute Pericarditis

  • Treatment depends on the underlying cause.
  • Purulent pyogenic pericarditis requires drainage, intravenous antibiotics, and supportive therapy.
  • Post-pericardiotomy syndrome and post-MI syndrome may require anti-inflammatory medications.
  • Viral pericarditis is usually self-limiting.
  • If pericardial effusion is present, surgical drainage is indicated.
  • If tamponade is suspected, pericardiocentesis and anti-inflammatory medications are indicated.

Chronic Constrictive Pericarditis

  • Once the diagnosis is made, pericardiectomy should be performed promptly.
  • The operation is done through a median sternotomy incision or a left anterolateral thoracotomy.
  • The constricting pericardium should be removed from all surfaces of the heart.
  • CPB is not usually necessary except in cases of significant bleeding.
  • The pericardium is removed from the pulmonary veins on the left side.
  • Phrenic nerves are carefully protected during the procedure.

Cardiac Tumors

Indications for Surgery

  • Cardiac myxoma should be resected on an urgent basis once diagnosed.

Surgical Methods

  • Atrial myxoma: Sufficient excision of the atrial septum, if possible, including uninvolved tissue 5 mm beyond the tumor margins. Other types of myxoma may require different approaches.
  • Ventricular myxoma: Does not require excision of the full-thickness ventricular wall.

Myxoma

  • Most common primary cardiac tumor in adults, benign (50-70%).
  • Most common in the left atrium, rare in the ventricles.
Surgery:
  1. Resection
  2. CPB and cardioplegia
  3. Right atriotomy, interatrial septum incision, left atriotomy, resection of the tumor
  4. Septal suture closure, right atriotomy closure

Sarcoma

  • Malignant (75%).
  • Can occur in any chamber of the heart.
Surgery:
  • Complete resection (may involve valve reconstruction or assist device implantation).
  • Heart transplantation may be considered in selected cases.

Congenital Heart Disease

Classification

No Atrioventricular (AV) ShuntLeft-to-Right ShuntRight-to-Left Shunt
  • Dextrocardia
  • Aortic coarctation
  • Pulmonary stenosis
  • Aortic branches abnormalities
  • Valve deformation
  • Coronary artery abnormalities
  • Atrial septal defect (ASD)
  • Ventricular septal defect (VSD)
  • Patent ductus arteriosus (PDA)
  • Abnormal pulmonary venous return
  • Lutembacher syndrome
  • Tetralogy of Fallot
  • Transposition of the great arteries
  • Truncus arteriosus
  • Tricuspid atresia
  • Two or three-chambered heart
  • Left ventricular hypoplasia
  • Pulmonary atresia
  • Tausig-Bing malformation
  • Eisenmenger syndrome

Palliative Heart Surgeries

  • Type I: Increase pulmonary blood flow (e.g., Blalock-Taussig shunt).
  • Type II: Decrease pulmonary blood flow and treat pulmonary hypertension (e.g., pulmonary artery banding).
  • Type III: Improve the mixture of arterial and venous blood (e.g., atrial septostomy).
  • Type IV: Decrease the load of the right ventricle (e.g., systemic-to-pulmonary artery shunt).

Surgery for ASD and VSD

ASD

  • Closure of left-to-right shunt, two types: Secundum and Primum.
  • Traditional Surgery: Midline sternotomy, CPB, cardioplegia, oblique atriotomy, direct suture closure of the defect.
  • Minimally Invasive Surgery: Submammary skin incision, mini-sternotomy, limited thoracotomy.
  • Percutaneous Transcatheter Closure: Catheter-implanted occlusion devices, femoral venous access, umbrella device deployed across the septal defect.

VSD

  • Closure of left-to-right shunt.
  • Repair of isolated VSD using CPB and hypothermia/cardioplegia.
  • Right atriotomy, closure of the defect with a patch.
  • Transesophageal echocardiography (TEE) used to assess for residual defects.

Tetralogy of Fallot

Surgical Repair

  • Widen the narrowed pulmonary valve and outflow tract.
  • Enlarge the passage from the right ventricle to the pulmonary artery.
  • Close the VSD with a patch.

Components of Tetralogy of Fallot

  1. VSD
  2. Overriding aorta
  3. Right ventricular hypertrophy
  4. Pulmonary infundibular stenosis

Transposition of the Great Vessels

Surgical Treatment

  • Temporary: Atrial septostomy to allow mixing of blood between the two sides of the heart.
  • Permanent: Arterial switch operation to switch the arteries to their proper positions.

Aortic Coarctation and Patent Ductus Arteriosus Surgery

Traditional Surgery

  • Used for larger defects.
  • Left thoracotomy.
  • Ligation of superior intercostal arteries.
  • Division and oversewing of the coarctation or PDA.
  • Clip application may be used for PDA closure.

Catheter Surgery

  • Used for smaller defects.
  • Closure with coils or occluder devices.

Artificial Heart Valves

Types

  • Mechanical: Made of inert synthetic material, durable, require lifelong anticoagulation.
  • Bioprosthetic: Made of animal tissue, less durable than mechanical valves, do not require lifelong anticoagulation.

Choice of Valve

Depends on the anticipated longevity of the patient, risk of anticoagulation, and patient preference.

Mechanical ValvesBioprosthetic Valves
  • Bileaflet, tilting disc, caged ball valves
  • High durability
  • Continuous anticoagulation needed
  • Lifespan is high, but reoperation rate is also high due to thromboembolic complications
  • Stented or stentless (xenograft or homograft)
  • Lower durability than mechanical valves
  • Reoperation may be needed due to structural degeneration
  • Lifespan is shorter than mechanical valves
  • Better hemodynamics than mechanical valves
  • Lower risk of thromboembolism

Indications for Mechanical Valves

  • Patients younger than 65 years
  • Patients with hyperparathyroidism
  • Patients at increased risk of reoperation
  • Patients who can tolerate lifelong anticoagulation

Indications for Bioprosthetic Valves

  • Patients older than 65-70 years
  • Patients with contraindications to anticoagulation
  • Patients unable to adhere to anticoagulation therapy
  • Reoperation for a failed mechanical valve
  • Women planning future pregnancy

Advantages and Disadvantages of Valve Replacement vs. Repair

Valve ReplacementValve Repair
Advantages:
  • High durability
  • More straightforward operation
  • Unlimited availability
Disadvantages:
  • Requires anticoagulation (for mechanical valves)
  • Lower hemodynamics compared to repair
  • Risk of thromboembolism, hemorrhage, postoperative MI, bleeding, and infection
Advantages:
  • May not require CPB
  • Better hemodynamics
  • High durability (in selected cases)
  • Lower mortality rate compared to replacement
  • Lower risk of infection
Disadvantages:
  • Requires CPB in many cases
  • Lower durability compared to mechanical valve replacement
  • Technically more challenging
  • Not all valves are repairable

Heart Assist Devices

Ventricular Assist Devices (VADs)

  • Provide mechanical circulatory support for the cardiovascular system.
  • Bridge to recovery: Temporary use until the heart recovers.
  • Bridge to transplantation: Long-term use until a heart transplant becomes available.
  • Destination therapy: Permanent substitute for a failing heart.
  • Can support the right ventricle, left ventricle, or both (biventricular support).
  • Left Ventricular Assist Device (LVAD): Inflow cannula into the apex of the left ventricle, outflow cannula into the ascending aorta.
  • Right Ventricular Assist Device (RVAD): Inflow cannula into the right atrium or tricuspid valve, outflow cannula into the pulmonary artery.
  • Pumping chamber can be extracorporeal or intracorporeal.

Possible Indications for VADs

  • Cardiogenic shock
  • Acute MI
  • Post-cardiotomy shock
  • Chronic heart failure
  • Myocarditis
  • Ventricular arrhythmias

Intra-Aortic Balloon Pump (IABP)

Mechanism of Action

  • Mechanical device that increases myocardial oxygen supply and cardiac output.
  • Cylindrical polyethylene balloon filled with helium, positioned in the aorta 2 cm distal to the left subclavian artery.
  • Systole: Active deflation creates a vacuum, increasing forward blood flow and decreasing afterload.
  • Diastole: Active inflation increases retrograde blood flow and coronary artery blood flow.

Indications for IABP

  • Cardiogenic shock in MI
  • Intracardiac mechanical defects (irreversible)
  • Unstable angina pectoris
  • Perioperative injury in MI
  • Preoperative high-risk patients
  • High-risk CABG surgery
  • Failed thrombolytic therapy in acute MI

Veno-Arterial Extracorporeal Membrane Oxygenation (VA ECMO)

Definition

  • Partial heart-lung bypass used for severe but potentially reversible respiratory or cardiac disease when conventional therapies fail.
  • Goal: Allow time for intrinsic recovery of the lungs and/or heart.
  • Venovenous (VV) ECMO: Provides support for the lungs only.
  • Veno-arterial (VA) ECMO: Provides support for both the heart and lungs.

ECMO Circuit

  • Drainage and return cannulae.
  • Oxygenator/heat exchanger (microporous or macroporous).
  • Blood pump (roller or centrifugal).
  • Tubing.

Duration of ECMO

  • Typically lasts for several days to weeks post-surgery.
  • The blood system is usually entered through cervical cannulae under local anesthesia.

Blood Pumps

Centrifugal Blood Pumps

  • Indications: Surgeries requiring extracorporeal circulation assistance.
  • Working Principle: Convert mechanical energy into moving fluid, generating kinetic energy (moving fluid) and potential energy (fluid pressure).

Axial Blood Pumps

  • Utilize a rotating impeller to provide continuous, non-pulsatile blood flow.
  • Quiet operation with less power consumption than pulsatile LVADs.
  • Fewer moving parts, providing theoretical advantages in terms of durability and reliability.
  • Smaller size, facilitating easier implantation.

Heart Transplantation

Indications

  • Deteriorating cardiac function with a life expectancy of less than 1 year.
  • End-stage heart disease with NYHA Class III-IV symptoms.
  • Cardiomyopathy, CHD with no conventional therapy options, ejection fraction < 20%, intractable angina, or malignant cardiac arrhythmias.
  • Pulmonary vascular resistance < 2 Wood units.
  • Age < 65 years (generally).
  • Emotionally stable patient.

Contraindications

  • Age > 65 years (generally).
  • Systemic infection.
  • Active malignancy.
  • Major systemic illness.
  • Irreversible major organ dysfunction.
  • Emotional instability.
  • Obesity.
  • Irreversible pulmonary hypertension.
  • Severe chronic obstructive pulmonary disease (COPD) (FEV1 < 1 L).