🫀 Cardiac Surgery Exam Guide

1. Introduction to Cardiac Surgery

Historical Overview & Anatomy
  • History: The first successful heart surgery was performed by Dr. Ludwig Rehn in 1896 (repair of a cardiac stab wound). In 1953, Dr. John Gibbon developed the first heart-lung machine. The 1960s-70s saw the rise of Coronary Artery Bypass Grafting (CABG).
  • Anatomy & Physiology: Essential for surgical planning. The conduction system includes the SA node, AV node, and bundle branches. Coronary arteries include the RCA, LAD, and LCx. Hemodynamics depend on stroke volume, cardiac output, preload, and afterload.
  • Common Procedures:
    • CABG: Indicated in multivessel disease. Uses saphenous vein or internal mammary artery.
    • Valve Repair/Replacement: Mitral or Aortic. Uses mechanical or bioprosthetic valves.
    • Congenital Heart Defect Repair: ASD, VSD, TOF.
    • Aortic Surgery: Aneurysm repair, dissection management.
Cardiopulmonary Bypass (CPB) & Surgical Team
  • Cardiopulmonary Bypass (CPB): Allows surgeons to operate on a still, bloodless heart.
    • Components: Pump, oxygenator, heat exchanger, reservoir.
    • Cannulation sites: Aorta and right atrium.
    • Physiological effects: Hemodilution, hypothermia, systemic inflammation.
    • Complications: Coagulopathy, air embolism, organ dysfunction.
  • The Surgical Team: Successful surgery requires a multidisciplinary team including the Cardiac surgeon, Anesthesiologist (manages hemodynamics), Perfusionist (operates the heart-lung machine), Scrub nurse, and ICU team.
  • Minimally Invasive & Robotic Surgery: Advances allow for less invasive approaches (e.g., small thoracotomy, endoscopic ports) and robotic-assisted precision.
    • Benefits: Improved cosmesis, reduced operative trauma, decreased pain, shorter hospital stay, and lower incidence of deep sternal wound infection.
    • Limitations (vs Sternotomy): Sternotomy offers excellent surgical exposure, allows combined procedures (e.g. Aortic + CABG), has shorter procedure times, and is not limited by specific patient contraindications.
💡 Golden Hints

1. Historical Milestone: The first successful heart surgery was performed in 1896 by Dr. Ludwig Rehn to repair a cardiac stab wound, long before the heart-lung machine was invented in 1953.

2. CPB Cannulation: To initiate Cardiopulmonary Bypass (CPB), the standard cannulation sites are the Aorta (for returning oxygenated blood) and the Right Atrium (for draining venous blood).

3. The Perfusionist: This is a critical member of the cardiac surgical team whose primary role is to exclusively operate the heart-lung machine (CPB) during the procedure.

2. Congenital Heart Diseases & ASD

Classification of Congenital Heart Diseases
  • Physiological Classification: Focuses on the presence or absence of cyanosis.
    • Acyanotic CHDs: Divided into Volume overload / left-to-right shunts (ASD, VSD, PDA, AVSD) and Pressure overload / obstructive lesions (Pulmonary stenosis, Aortic stenosis, Coarctation of the aorta).
    • Cyanotic CHDs: Right-to-left shunting (Tetralogy of Fallot, TGA, Tricuspid atresia, TAPVR, Pulmonary atresia, HLHS).
  • Anatomical Classification: Groups by structural abnormalities.
    • Septal defects: ASD, VSD, AVSD.
    • Outflow tract obstructions: Aortic stenosis, pulmonary stenosis.
    • Abnormal connections: TGA, TAPVR.
    • Complex malformations: TOF, HLHS, DORV.
Atrial Septal Defects (ASD)
  • Overview: Defects at the atrial level leading to left-to-right shunting, causing volume overload of the right heart and increased pulmonary blood flow. They constitute 10-15% of congenital cardiac defects, and up to 40% of those presenting in adulthood.
  • Types of ASD:
    1. Ostium secundum defects (70–80%): The commonest type, involving the fossa ovalis. Distinct from patent foramen ovale (probe patency).
    2. Ostium primum defects (20%): A form of AV defect, associated with a cleft mitral valve.
    3. Sinus venosus defects (10%): Usually superior, at the mouth of the SVC, associated in 90% with partial anomalous pulmonary venous drainage (PAPVD).
    4. Coronary sinus defects (<1%): Unroofed coronary sinus, almost always associated with persistent left SVC.
  • Pathophysiology & Natural History: Permits left-to-right shunting. If operated on before age 25, long-term survival is normal. In adults over 60 with untreated ASD, about 50% have atrial flutter, fibrillation, or sinus node dysfunction.
  • Presentation & Investigations: Rarely cause symptoms in children. Present mostly in the 3rd/4th decade with fatiguability. Physical exam shows a systolic ejection pulmonary flow murmur. Echo is diagnostic. Catheterization is indicated if pulmonary hypertension is suspected.
  • Treatment:
    • Percutaneous: Defects up to 40mm within the fossa ovalis with a 5mm rim can be closed via catheter.
    • Surgical: Up to 40% of small/moderate ASDs close spontaneously by age 4. Indicated for persistent secundum ASDs, large shunts with failure to thrive, paradoxical embolus, and to prevent pulmonary hypertension. Note: If Pulmonary Vascular Resistance (PVR) is ≥15U/m2, surgical mortality is high.
💡 Golden Hints

1. ASD Types & Associations: Ostium secundum is the most common ASD (70-80%). However, Ostium primum is uniquely associated with a cleft mitral valve, and Sinus venosus is highly associated (90%) with PAPVD.

2. Age of Intervention: Closing an ASD before the age of 25 results in normal long-term survival. Delaying closure significantly increases the risk of long-term arrhythmias (50% of 60-year-olds develop flutter/fibrillation).

3. Contraindication for Surgery: Severe pulmonary hypertension is a red flag. If the Pulmonary Vascular Resistance (PVR) is 15U/m2 or higher, the mortality rate for surgical closure becomes exceptionally high.

3. VSD, PDA, AVSD & Coarctation

Ventricular Septal Defects (VSD)
  • Overview: The commonest congenital heart defect (25%). Abnormal defect in the ventricular septum allowing blood communication.
  • Classification:
    • Perimembranous (70–80%): Most common. Margin consists of fibrous continuity between tricuspid and aortic valves. Conduction bundles run along the inferior rim.
    • Muscular (5–10%): Rim is entirely muscular (includes multiple "Swiss cheese" VSDs). Conduction bundles are remote from the defect.
    • Juxta-arterial (5–10%): Also called conal septal or supracristal. The conjoined leaflets of aortic and pulmonary valves form the rim. Associated with aortic-valve prolapse in up to 50% of cases.
  • Pathophysiology: Causes LV volume overload, increased pulmonary blood flow, and reduced systemic cardiac output. Large untreated defects may lead to Eisenmenger syndrome (reversal of shunt).
  • Natural History & Treatment: 30–40% close spontaneously (especially small PM VSDs). Inlet and juxta-arterial VSDs do not close spontaneously. Treatment is surgical closure for:
    • Moderate/large VSDs after age 1.
    • CHF resistant to medical therapy in infants.
    • Elevated PVR after 6 months.
    • Evolving aortic regurgitation in outlet VSDs.
Patent Ductus Arteriosus (PDA)
  • Overview: Persistence of the fetal duct connecting the pulmonary artery with the descending aorta. Extremely common in premature infants (<1200g - 80%).
  • Pathophysiology & Presentation: Left-to-right shunt increases as PVR falls leading to CHF. Presents with a wide pulse pressure (bounding pulses) and a classic harsh, continuous machinery murmur extending into diastole.
  • Management: Medical therapy with Indomethacin and ibuprofen is highly effective in closing the duct in pre-term infants. If medical therapy fails or the infant is symptomatic/older than 3 months, surgical ligation is indicated.
AVSD & Coarctation of the Aorta
  • Atrioventricular Septal Defects (AVSD): Spectrum of defects (endocardial cushion defects). Very common in Down’s syndrome (45% of CHD in Down's are AVSDs).
    • Partial AVSD: Primum ASD with separate left/right AV valves.
    • Complete AVSD: Single AV valve common to both right and left junctions.
  • Coarctation of the Aorta: Congenital narrowing of the upper descending aorta, opposite the ductus arteriosus. Associated with bicuspid aortic valve and is the most common cardiac defect in Turner syndrome (15-20%).
  • Coarctation Pathophysiology & Presentation: Causes high LV afterload, leading to LV hypertrophy and upper extremity hypertension. Neonates present with collapse and absent femoral pulses. Older patients show discrepancies of >20mmHg between upper and lower extremities.
  • Coarctation Management: In shocked neonates, initial management is supportive by reopening the duct. In older children, balloon angioplasty is the first-line treatment. Isolated coarctation is an indication for surgical repair.
💡 Golden Hints

1. VSD Associations: The Juxta-arterial (supracristal) VSD is unique because it is located right under the aortic and pulmonary valves, leading to aortic-valve prolapse in up to 50% of cases.

2. The Machinery Murmur: A classic harsh, continuous murmur heard in the second left intercostal space, accompanied by bounding pulses, is the hallmark clinical sign of a Patent Ductus Arteriosus (PDA).

3. Syndromic Associations: AVSD (Endocardial cushion defect) is highly associated with Down’s syndrome, whereas Coarctation of the Aorta is the most common cardiac defect in Turner syndrome.

4. Cyanotic Defects & Pulmonary Stenosis

Tetralogy of Fallot (ToF)
  • Overview: The commonest cyanotic lesion (10% of CHD). 25% of patients have DiGeorge syndrome (chromosome 22 deletion).
  • The Four Lesions: Caused by anterior deviation of the outlet septum:
    1. Pulmonary stenosis (RVOT obstruction).
    2. Right Ventricular Hypertrophy (RVH).
    3. Overriding aorta.
    4. Ventricular Septal Defect (VSD).
  • Presentation & Natural History: Degree of RVOT obstruction determines outcome. Patients present with cyanosis, and classic tet spells (cyanotic episodes due to muscular spasm causing acute obstruction). Squatting is a characteristic compensatory maneuver.
    • Without surgery, 25% die within 1 year, 40% within 4 years, and 95% within 40 years.
  • Investigations & Surgery: EKG shows right-axis deviation. CXR classically shows a boot-shaped heart (due to RVH and small MPA) and decreased pulmonary vascularity. Surgical management aims to repair all tetralogies between 3–6 months. Early palliation with a systemic–PA (B-T) shunt is an option before complete repair.
Transposition of the Great Arteries (TGA) & Pulmonary Stenosis
  • Transposition of Great Arteries (TGA): The aorta arises from the RV and the pulmonary trunk arises from the LV. The most common cyanotic lesion presenting in the neonatal period (5% of CHD, 90% isolated). Without an ASD/VSD, infants die soon after the ductus arteriosus closes. Treated with a corrective arterial switch procedure with low mortality.
  • Pulmonary Stenosis (PS): Makes up 8-10% of CHD. The pulmonary valve is stenotic, often dome-like with fused commissures. Causes RV hypertrophy and cyanosis.
    • Presentation: Neonates with severe PS present with severe cyanosis, a systolic murmur with an ejection click, and hepatomegaly due to severe TR.
    • Management: Trivial/mild gradients (<50mmHg) do not require intervention. Moderate/severe gradients require Balloon valvuloplasty or surgical valvuloplasty if the annulus is very small.
💡 Golden Hints

1. Cyanotic Lesion Timing: While Tetralogy of Fallot is the most common cyanotic congenital heart defect overall, Transposition of the Great Arteries (TGA) is the most common cyanotic lesion presenting specifically in the neonatal period.

2. Squatting Mechanism: Children with ToF intuitively squat during cyanotic "tet spells". This posture increases systemic vascular resistance, which decreases the right-to-left shunt across the VSD and forces more blood into the lungs.

3. Radiological Sign: A "boot-shaped" heart on a chest X-ray, accompanied by decreased pulmonary vascular markings, is highly characteristic of Tetralogy of Fallot.

5. Ischemic & Valvular Heart Disease

Ischemic Heart Disease (IHD) & ACS
  • Pathophysiology: Stenotic CAD is narrowing due to atherosclerosis. Stable plaques cause stable angina, while unstable plaque rupture causes thrombosis and Myocardial Infarction (MI). (50% of MIs occur distal to angiographically 'normal' vessels).
  • Symptoms: Exertional angina, dyspnea, orthopnea (sudden increase in preload on lying flat), and paroxysmal nocturnal dyspnea. Nausea results from parasympathetic stimulation.
  • Unstable Angina & ACS: Acute coronary syndrome (ACS) covers sudden reduced blood flow, including Unstable Angina, NSTEMI, and STEMI.
    • Unstable angina is distinguished from NSTEMI by the absence of raised cardiac enzymes (CK-MB or troponin).
    • STEMI is differentiated from NSTEMI by specific EKG changes.
Valvular Heart Disease
  • Aortic Stenosis (AS): Commonest cause is calcific degeneration. Other causes include congenital Bicuspid aortic valve (around 50% are stenotic by age 60, associated with aortic root dilatation) and rheumatic disease.
  • Aortic Insufficiency (AI): Causes include myxomatous degeneration, rheumatic disease, infective endocarditis (leaflet perforation), and aortic root dilatation (e.g., Marfan syndrome, syphilis, ankylosing spondylitis).
  • Mitral Valve Disease:
    • Mitral Stenosis: Chronic rheumatic heart disease is the commonest cause.
    • Mitral Regurgitation: Degenerative disease is the most common cause in the West (spectrum from fibroelastic deficiency to Barlow's disease/floppy valve). Also caused by rheumatic disease, endocarditis, Marfan, ischemia, and endomyocardial fibrosis (common in sub-Saharan Africa).
  • Tricuspid & Pulmonary Disease: Tricuspid stenosis is rare (rheumatoid). Tricuspid regurgitation is most commonly functional secondary to mitral valve disease, but can be due to Ebstein’s anomaly or carcinoid syndrome. Acquired pulmonary valve disease is very unusual.
Valve Prostheses
  • Mechanical vs Bioprosthetic (Tissue): Tissue valves can be stented (porcine aortic valves or bovine pericardium mounted on metal) or stentless (supported by pig aorta and cloth).
  • Homografts: Human cadaveric aortic roots, complete with aortic valves in situ.
  • Ross Procedure: The patient's own excised pulmonary valve (pulmonary autograft) is used to replace the diseased aortic valve.
💡 Golden Hints

1. ACS Differentiation: The primary difference between Unstable Angina and NSTEMI is that NSTEMI presents with elevated cardiac enzymes (troponin or CK-MB), indicating myocardial damage, whereas Unstable Angina does not.

2. Bicuspid Aortic Valve: A congenital bicuspid aortic valve is present in 1-2% of the population. By age 60, approximately 50% of these valves become stenotic and they are highly associated with aortic root dilatation.

3. The Ross Procedure: Involves a double valve surgery where the patient's own healthy pulmonary valve (pulmonary autograft) is excised to replace a diseased aortic valve.

6. High-Yield Comparisons (المقارنات الامتحانية)

هذا القسم يجمع أهم المقارنات المستخلصة من ملازم جراحة القلب، والتي تتكرر باستمرار في الامتحانات:

1. Acyanotic vs. Cyanotic Congenital Heart Diseases
Feature Acyanotic CHDs Cyanotic CHDs
Hemodynamic Issue Volume overload (L-to-R shunt) OR Pressure overload (obstruction). Abnormal mixing OR Right-to-Left shunting.
Classic Examples ASD, VSD, PDA, AVSD
(Volume Overload)
PS, AS, Coarctation
(Pressure Overload)		 Tetralogy of Fallot (TOF), TGA, TAPVR, Tricuspid Atresia, HLHS.
Clinical Color Pink (Normal saturation initially). Blue / Cyanosed (Desaturated).
2. Types of Atrial Septal Defects (ASD)
Type of ASD Frequency Key Anatomical Feature / Association
Ostium Secundum 70 – 80% (Most Common) Involves the fossa ovalis. May extend to IVC.
Ostium Primum 20% Form of AV defect; strongly associated with cleft mitral valve.
Sinus Venosus 10% Located at mouth of SVC; 90% associated with PAPVD.
Coronary Sinus Defect < 1% Unroofed coronary sinus; associated with persistent left SVC.
3. Types of Ventricular Septal Defects (VSD)
Type of VSD Frequency Key Anatomical Feature / Association
Perimembranous 70 – 80% (Most Common) Fibrous continuity between tricuspid & aortic valves. Conduction bundles run along inferior rim.
Muscular 5 – 10% Entirely muscular rim (includes "Swiss cheese"). Conduction bundles are remote from defect.
Juxta-arterial (Supracristal) 5 – 10% Under aortic/pulmonary valves. Associated with aortic-valve prolapse (in 50%). Does not close spontaneously.
4. Acute Coronary Syndromes (ACS)
Condition Clinical Symptoms EKG Findings Cardiac Enzymes (Troponin / CK-MB)
Unstable Angina Severe, persistent ischemic chest pain. Usually normal or non-specific. Normal (No elevation).
NSTEMI Severe ischemic chest pain. ST depression, T-wave inversion (No ST-elevation). Elevated.
STEMI Severe ischemic chest pain. ST-elevation. Elevated.
5. Full Sternotomy vs. Minimally Invasive Mitral Surgery
Feature Minimally Invasive Surgery Full-Sternotomy Surgery
Advantages Improved cosmesis, reduced operative trauma, decreased postoperative pain, lower incidence of deep sternal wound infection, shorter hospital stay. Excellent surgical exposure, ability to perform combined surgeries (e.g. aortic + CABG), shorter procedure time.
Limitations Limited to select patients (contraindications exist), longer procedure time. Bigger scar, more pain, higher risk of deep sternal wound infection.