Interactive Tutorial: Surgery Treatment Of Coronary Artery Disease And Heart Transplant

Question 1

CAD

Answer 1

Types:

1. Stable angina
2. ACS
   - Unstable angina
   - Non-STEMI
   - STEMI
3. Sudden death

5-year survival of CAD:
- Left main: 50%
- 3 vessel: 70%
- 2 vessel: 88%
- 1 vessel: 90-95%
—> Other interfering risk factors: LV function, extent of Ischaemia, anatomy of lesion, arrhythmia, DM, recent MI etc.

Diagnosis:
- History, P/E —> Determine Low, Intermediate, High risk patient of having CAD
- Low / Intermediate risk:
—> Able to exercise —> **Stress test / Exercise ECG (aka treadmill)
—> Not able to exercise —> **CT coronary (Iodine contrast), **MRI (Gadolinium contrast) / **Stress Echo, **Perfusion study (Thallium contrast)
- High risk:
—> **Catheter coronary angiogram (still Gold standard) —> Vessels narrowed >50% diameter considered significant

Other classification:

1. Perfusion study and Viability study
   - SPECT scan (aka Thallium scan —> Perfusion study)
   - PET scan
   - MRI
   - Stress Echo
2. Anatomical study
   - CT coronary angiogram
   - Catheter coronary angiogram with functional flow reserve

Question 2

Treatment options of Stable angina

Answer 2

1. Medical treatment
   - ABCDE
   —> Aspirin + Anti-anginal
   —> Beta blocker + BP control
   —> Cholesterol + Cigarette control
   —> Diet + DM
   —> Exercise + Education
2. PCI
3. CABG

Choice: Balance between risks + benefits
Benefits: Relieve symptoms + Improve survival
Risks: Morbidity + Mortality

Question 3

Indications for Revascularisation

Answer 3

2 Determining factors:

1. Symptom
   - Not controlled by optimum medical therapy
2. Prognosis
   - Anatomy (Left main / 3 vessel)
   - Ischaemic region

Question 4

PCI vs CABG

Answer 4

CABG:
- **Left main
- **3 vessel disease with LV dysfunction
(- In reality: CABG > PCI if more risk factors)

Risk factors:

1. Impaired ventricular function (EF <50%)
2. DM
3. Difficult coronary anatomy (e.g. proximal lesions, total occlusion, diffuse disease, calcified vessel)

Efficacy:
- CABG > PCI in 10 years
—> PCI has higher rate of recurrence angina, reoperation rate (∵ in stent re-stenosis)
—> PCI has slightly higher risk of MI / death in 10 years

Question 5

***CABG

Answer 5

Area of Grafts:

1. Aorta —> Posterior descending artery from RCA
2. Aorta —> LAD
3. Aorta —> Obtuse marginal branch from LCx

Conduit:

1. ***Left internal mammary artery (LIMA)
   - “best” conduit
   - underneath left side of sternum
   - patency >90% in 10 years
   - usually anastomosed to LAD (∵ cover most area of myocardium)
2. ***Radial artery
   - arterial graft theoretically more patent than venous graft
   - patency ~70% in 10 years
   - can be harvested by minimally invasive method
3. ***Long saphenous vein
   - most commonly used
   - patency ~50% in 10 years
   - can be harvested by minimally invasive method
4. Other less commonly used conduits
   - Right internal mammary artery (RIMA)
   - Gastroepiploic artery
   - Inferior epigastric artery
   - Short saphenous vein
   - Homograft (very poor patency rate)

Approach:

1. Open: Median sternotomy (still most frequently used)
2. Minimally invasive surgery (MIS)
   - MIDCAB (Minimally invasive direct CA bypass) —> harvest LIMA and directly graft onto LAD
   - Robotic

Anastomosis:

1. Distal anastomosis
   - End to side
   - Sequential graft (一條graft配給兩條CA —> end to side + side to side)
2. Proximal anastomosis (LIMA graft no need proximal anastomosis, branch from left subclavian artery)
   - Aorta
   - Y-graft

Question 6

Cardiopulmonary bypass

Answer 6

• Stop heart from beating —> But have to do Myocardial protection
• Aim: Bloodless + Motionless surgical field

Off pump CABG (without Cardiopulmonary bypass) —> Use in high risk patients (e.g. atherosclerotic aorta —> cannot find site to cannulate for cardiopulmonary bypass):
Pros:
- Less bleeding
- Less renal failure
- Less stroke in atherosclerotic aorta

Cons:

• Less no. of grafts
• Less long term patency
• Technical demanding

Question 7

Post-op medications

Answer 7

1. GTN infusion
   - Prevent spasm of ***IMA
   - No specific duration, usually stop next day
2. Diltiazem infusion
   - Prevent spasm of ***RA
   - Usually stop when oral Diltiazem started
   - Last for 3-6 months
3. Aspirin
   - Early aspirin improve early vein graft patency —> best to take within 6 hours post-op, no benefit if >48 hours
   - Life long for post-CABG
4. Beta blocker
   - Early resume beta blocker reduce post-op AF + decrease cardiac workload
5. Lipid lowering drugs
   - Improve vein graft long term patency

Question 8

Complications of CABG

Answer 8

• Risk stratification according to EuroScore: Most 1-2%

Major risk:

• Bleeding
• CVA
• MI
• Arrhythmia
• Infection
• Acute renal failure (requiring temporary renal replacement therapy)

Question 9

Complication: Peri-operative MI

Answer 9

Causes:

1. Poor myocardial protection techniques
2. Graft occlusion
3. Emboli to grafts / native coronary arteries

Diagnosis:

1. Chest pain (NOT accurate ∵ concomitant chest wall wound pain)
2. Cardiac enzyme
   - CKMB >5x normal
   - Tnl >10x normal
3. ECG
   - New Q wave, ST changes (compare to previous ECG!!!)
4. Echo
   - New regional wall movement abnormality

Treatment (depend on Haemodynamic status):
Stable / Suspicious:
1. LMWH

Unstable:

1. IABP (intra-aortic balloon pump)
2. Coronary angiogram
3. ?Redo

Question 10

Complication: AF

Answer 10

• Up to 40% of patient will have post-op AF

Risk factors:

• Old age
• COAD
• Withdrawal of Beta blocker

Problems:

• Loss of 20% CO
• Risk of thromboembolism (esp. >48 hours)

Preventive measures:

• Keep K, Mg normal
• Resume Beta-blocker
• Amiodarone, Sotalol, Mg supplement

Treatment
Stable:
1. Pharmacological cardioversion
2. Rate control + Anticoagulation (if AF is chronic / >48 hours, difficult in Pharmacological cardioversion)

Unstable:
1. DC cardioversion

Question 11

Complication: Stroke

Answer 11

• 3% risk in CABG patients
• Prolonged hospital stay, increase morbidity + mortality

Risk factors:

1. History of stroke
2. Old age
3. Carotid artery disease
4. Emergency operation
5. Atherosclerotic aorta

Diagnosis:
1. CT brain (diagnosis + treatment if haemorrhage)

Prevention:

1. Off pump CABG
2. Alternative cannulation sites (avoid dislodging atherosclerotic plaques when cannulating ascending aorta)
3. Special device
4. Circulatory arrest

Question 12

Special situations in Surgical management of IHD

Answer 12

1. Primary CABG for STEMI
2. Shock due to MI (Post-MI shock)
3. Acute post-MI mechanical complications
   - MR
   - VSD
4. Chronic post-MI mechanical complications
   - Aneurysm of LV
   - Heart failure

Question 13

1. Primary CABG for STEMI

Answer 13

• Less common
• Golden period usually passed when arrive OT
• Advance of primary ***PCI

Post-MI CABG:

• Best to delay 3-7 days if stable and pain free
• Possibly due to ***reperfusion injury

Question 14

2. Shock due to MI (Post-MI shock)

Answer 14

• 0.2% of MI
• ***>40% myocardium is loss before developing shock
• High 30-day mortality ~70%
• SHOCK trial: CABG would have better 1 year survival compared to medical treatment
• Surgical mortality ~50%
• Tendency is stabilise —> CABG later

Question 15

3. Acute post-MI mechanical complications: MR

Answer 15

• Papillary muscle dysfunction / rupture ***after 3-5 days (muscle slowly necrosis)
• Usually postero-medial papillary muscle due to sole blood supply by 1 coronary artery

Clinical features:

1. SOB, Shock (~***day 3-5 post-MI)
2. New Pan-systolic murmur
3. Congested lung field on CXR

Diagnosis:
1. Echo

Treatment:

1. Support by Inotropes + IABP
2. Urgent operation
   - MV repair / MVR
   - +/- CABG

Question 16

3. Acute post-MI mechanical complications: VSD

Answer 16

• Mortality >50% in first day
• Most common ***Anterior VSD from LAD infarct

Clinical features (~MR):

1. SOB, Shock (~***day 3-5 post-MI)
2. New Pan-systolic murmur
3. Congested lung field on CXR

Diagnosis:
1. Echo

Treatment:

1. Support by Inotropes + IABP
2. Delayed operation if stable until fibrosis around VSD
   - ∵ myocardium is fragile after MI —> early operation cannot close defect effectively

Question 17

4. Chronic post-MI mechanical complications: Aneurysm of LV

Answer 17

• Success of primary PCI —> reduce incidence of acute mechanical complication post-MI
• Patient survive longer after IHD / MI
• Translate to more chronic problem

Aneurysm of LV:

• Affect LV efficiency
• LV clots (more stagnant blood flow in hypokinetic aneurysm area)
• Patient may have SOB (∵ lower LV efficiency)

Treatment:

1. LV Aneurysmectomy / Ventriculoplasty
   - improve in EF + symptom of SOB but NOT survival

Question 18

4. Chronic post-MI mechanical complications: Heart failure

Answer 18

• Repeated MI —> progressive deterioration of function

Treatment:

1. Mechanical support (can be bridging therapy to heart transplant)
   - ECMO
   - LVAD
2. Heart transplant

Question 19

***Summary

Answer 19

Indication of CABG

1. Symptom
2. Prognosis

Common conduits and patency rate

1. LIMA (90%)
2. RA (70%)
3. Long saphenous vein (50%)

Major risks of CABG:

1. Peri-operative MI
2. AF
3. Stroke

Complications from AMI:

1. Acute
   - MR
   - VSD
2. Chronic
   - Aneurysm of LV
   - Heart failure

Question 20

Success of Heart transplant

Answer 20

1. Advance in immunosuppressant
   - Cyclosporine
2. Advance in endomyocardial biopsy
   - Transvenous endomyocardial biopsy —> reliable mean for monitoring allograft rejection

Question 21

Indications of Heart transplant

Answer 21

• **End stage cardiac disease
• Mostly end stage heart failure
  1. **Dilated cardiomyopathy
  2. **Ischaemic cardiomyopathy
  3. Valvular cause
  4. Hypertrophic cardiomyopathy

Recipient selection:

1. Relatively healthy patients with end-stage heart disease
2. Refractory to other appropriate medical + surgical therapies
3. Possess potential to resume a normal active life
4. Ability to maintain compliance with a rigorous medical regimen after cardiac transplantation

Question 22

Relative CI for Heart transplant

Answer 22

1. Recent malignancy
2. COPD
3. Recent + Unresolved pulmonary infarction / PE
4. DM with end-organ damage (neuropathy, nephropathy, retinopathy)
5. Peripheral vascular / cerebrovascular disease
6. Active peptic ulcer disease
7. Current / Recent diverticulitis
8. Other systemic illness likely to limit survival / rehabilitation
9. Sever obesity / cachexia
10. Severe osteoporosis
11. Active alcohol / drug abuse
12. History of non-compliance / psychiatric illness likely to interfere with long-term compliance
13. Absence of psychosocial support

Question 23

Recipient prioritisation for Heart transplant

Answer 23

More urgent:

• less life expectancy
• more mechanical support

Question 24

Donor selection

Answer 24

Suggested criteria:
- Age <55
- Absence of following:
—> Prolonged cardiac arrest
—> Septicaemia
—> Extracerebral malignancy
—> Positive serologies for HIV, HBV, HCV
—> Haemodynamic stability without high-dose inotropic support

Workup for Cardiac donor:

1. Past medical history + P/E
2. ECG
3. CXR
4. ABG
5. ABO compatibility, HIV, HBV, HCV
6. **Echo, Pulmonary artery catheter evaluation, **Coronary angiogram

Process:
- Echo
—> Good LVEF >45% —> Proceed
—> Poor LVEF <45% —> Hormonal resuscitation (T3, Vasopressin, Methylprednisolone, Insulin) —> Haemodynamic management (Fluid status, Inotropic support) —> Ok —> Proceed

Question 25

Procedure of Harvest heart

Answer 25

1. Heparin 2. Aortic cross clamp 3. Cardioplegic solution to stop + protect heart (diffuse into myocardium via coronary artery) 4. Left + Right heart decompression (ligate LA + RA) 5. Cardiectomy Organ preservation: - Current graft preservation techniques —> Safe ischaemic period 4-6 hours - Single flush of cardioplegic solution —> Static hypothermic storage at 4-10oC Orthotopic Implantation technique: 1. Biatrial technique (suture donor RA with recipient RA) 2. Bicaval technique (RA is entirely donor’s)

Question 26

Immunosuppressants in Heart transplant

Answer 26

Triple therapy: 1. CNI - Cyclosporine - Tacrolimus 2. Anti-Proliferative agent - AZA - MMF - Cyclophosphamide (rare) 3. Corticosteroid - Prednisone / Prednisolone Recent: - Sirolimus (Rapamycin), Everolimus —> block downstream of IL2 receptor

Question 27

Complications of Heart transplant

Answer 27

Early: 1. Infection 2. Rejection Chronic: 1. Cardiac allograft vasculopathy (~CAD) 2. Renal dysfunction 3. Malignancy (∵ prolonged immunosuppressants)

Question 28

Future of heart transplant

Answer 28

Improvement in: 1. Immunosuppressant strategies (decrease rejection + infection) 2. Organ preservation techniques (prolong safe ischaemic time, prevent ischaemic damage) 3. Mechanical assist devices 4. Ventricular restoration surgeries 5. Possibility of donor pool expansion