بسم هللا الرحمن الرحيم•

Principles of cardiac surgery

Dr . Nadir Mehmood

Asstt Prof of Surgery

RMC

LEARNING OBJECTIVESAt the end of this discussion, a student will be able to;

• Tell why cardiac surgery is more difficult

• Enlist the historical technical milestones necessary for cardiac surgery

• Enumerate the pre op preparation and assessment parameters

• Enlist the Conduits used for bypass and type of incisions for cardiac surgery

• Describe the steps of Conventional CABG procedure

• Summarize indications for cardiac surgery

• Enlist important factors in postoperative management of cardiac surgery patients

• Prior to 1930’s, heart surgery seen as impossible, with high morbidity and mortality– “Surgery of the heart has probably reached the limits set by nature to all surgery”

–Stephen Paget, 1896, Surgery of the Chest

• 1937: Dr. John Gibbon designs heart-lung machine, which enables cardiopulmonary bypass (CPB)

• 1955: Vineburg and Buller implant internal mammary artery into myocardium to treat cardiac ischemia and angina

• 1958: Longmire, Cannon and Kattus at UCLA perform first open coronary artery endarterectomy without CPB

• During 1960’s and 1970’s, CPB and cardioplegic arrest are adopted, allowing Coronary Artery Bypass Graft (CABG) to emerge as a viable surgical treatment

RG Cohen, et al; Minimally Invasive Cardiac Surgery

INDICATIONS FOR

SURGERYERY

●CABG (coronary artery bypass grafting)●Valve repair / replacement●Thoracic aneaurysm repair●Surgical management of arrhythmia●Ventricular reconstruction●Removal of myxoma●Surgical correction for congenital heart diseases●Insertion of ventricular assist device●Chronic angina●Unstable angina●Acute myocardial infarction●Acute failure of percutaneous transluminal coronary angioplasty (PTCA)●Cardiac transplantation

Why cardiac surgery is more difficult ?

• Moving organ

• Contains blood

• Vital, and no place for mistakes.

• Shared with anesthetist

• Very sensitive to electrolyte derangements

RATIONALE FOR CARDIAC SURGERY

SURGICAL MANAGEMENT OF HEART DISEASES REQUIRES INFORMATION :

• OUTLOOK IF CONDITION IS UN-OPERATED

• THE RISK OF OPERATION ITSELF INCLUDING FAILURE TO DEAL WITH THE DISEASE

• OUTLOOK FOLLOWING SUCCESSFUL SURGERY

Approaches for cardiac surgery:

The main and the commonest incision for the cardiac surgery is median sternotomy.

But others could be used like:

• Right anterolateral thoracotomy

• Left posterolateral thoracotomy

• Minimally invasives.

• Endoscopic approaches.

Preoperative Preparation of the Patient

• Systems Approach to Preoperative Evaluation

• Additional Preoperative Considerations

• Preoperative Checklist

Determining the Need for Surgery

• Patients are often referred to surgeons with a suspected surgical diagnosis and the results of supporting investigations in hand. In this context, the surgeon's initial encounter with the patient may be largely directed toward confirmation of relevant physical findings and review of the clinical history and laboratory and investigative tests that support the diagnosis.

Perioperative Decision Making

• Once the decision has been made to proceed with operative management, a number of considerations must be addressed regarding the timing and site of surgery, the type of anesthesia, and the preoperative preparation necessary to understand the patient's risk and optimize the outcome.

SYSTEMS APPROACH TO PREOPERATIVE EVALUATION

One of the first anesthesia risk categorization systems was the ASA classification. It has five stratifications:

I—Normal healthy patient II—Patient with mild systemic disease

III—Patient with severe systemic disease that limits activity but is not incapacitating

IV—Patient who has incapacitating disease that is a constant threat to life

V—Moribund patient not expected to survive 24 hours with or without an operation

POTENTIAL RISKS

• Pulmonary

• Renal

• Endocrine

• Nutritional Status

• Obesity

• Antibiotic Prophylaxis

• Identification of coexisting cardiovascular, circulatory, hematologic, and metabolic derangements secondary to renal dysfunction are the goals of preoperative evaluation in these patients

Adverse outcome indicators

70 years or older

self-reported alcohol abuse

poor cognitive status

poor functional status

markedly abnormal preoperative serum sodium, potassium, albumin or glucose level

Cardio pulmonary bypass (CPB)

Basic principle of CPB is:

• Bypass the right and left side of heart

• Thermal regulation

• Oxygenation

• Filtration

Rationale for the use of CPB

During open heart surgery, CPB provides the surgeon with a clear field for cardiac manipulation and maintenance of pulmonary and hemodynamic stability. The objective of heart-lung pump is to provide enough flow to maintain a sufficient cardiac index for tissue perfusion.

The addition of cardioplegia allows the surgeon to work in a motionless and bloodless field.

The addition of hypothermia to CPB has been standard practice since Bigelow demonstrated improved tolerance of the entire organism to ischemia accompanied by hypothermia.

The CPB Circuit

Venous conduit Drains blood from venous systemic circulation. Usually a cannula for blood drainage inserted into the right atrium with openings for IVC and SVC.

Arterial blood return Returns oxygenated blood back to the body via arterial cannula most often placed in the ascending aorta.

In the middle Pump/Oxygenator is run by the perfusionist. Provides oxygenation and means of delivering various elements to patient during CPB. Then pumps blood back to the arterial circulation.

Sites of arterial canulation

• Ascending aorta

• Arch of aorta.

• Right subclavian.

• Femoral artery.

Steps of cardiac surgery with the use of CPB, (simplified)

Heparinize. Insert canulae Connect to lines already prepared. Go on bypass. Demand for the required temperature Cross clamp the aorta Give cardioplegia Do the procedure No more plegia Re-warm Stop CPB. Remove the cross clamp Remove the canulae

Monitoring during CPB

This will be done by the coordination between perfusionist and anesthetist

Includes monitoring of :

• Perfusion pressure

• Venous return

• Urine output

• Temperature

• Blood gas

• Electrolytes

Monitoring during CPB

• ACT, (Clotting time)

• PCV

• PO2 and PCO2

• ECG activities if any

• Time for the plegia

• TEE and presence of air in the heart.

• EEG in some cases of circulatory arrest.

• Need for medications

• Most common arteries bypassed:

– Right coronary artery

– Left anterior descending coronary artery

– Circumflex coronary artery

Adapted from BJ Harlan, et al; Manual of Cardiac Surgery

• Saphenous vein used for bypassing right coronary artery and circumflex coronary artery

• Internal mammary artery (IMA) used for bypassing left anterior descending coronary artery– Patency rate over 90% after 10 years

• If more veins are needed, alternative sites such as upper extremity veins can be used– Patency rate as low as 47% after 4.6 years

BJ Harlan, et al; Manual of Cardiac Surgery

• Positive:– Relief of angina in 90% of patients

– 80% angina free after 5 years

– Survival about 95% after 1 year

– Low chance of restenosis

• Negative:– 2-3 days in ICU, 7-10 day total hospital stay

– 3-6 month full recovery time

– 5-10% have post-op complications

– High cost ($25,000-$30,000)

– Long time on CPB• Depression of the patient's immune system

• Postoperative bleeding from inactivation of the blood clotting system

• Hypotension

BJ Harlan, et al; Manual of Cardiac Surgery, WebMD.com, American College of Cardiology Foundation

• CABG results in a lower restenosis rate as compared with stenting– Drug-eluting stents will narrow this difference

• Due to repeat treatment, costs for stents and surgery are approximately equal after 2 years

• Minimally invasive surgeries will result in fewer complications from surgery and a shorter hospital stay– This leads to lower costs for surgery, essentially removing the cost

advantage of stenting

• Diabetics have a substantially better response to CABG than to angioplasty and stenting

Current Controlled Trials in Cardiovascular Medicine

CARDIAC SURGERY

VALVULAR HEART DISEASES

a. CONGENITAL

b. AQUIRED

MITRAL VALVE DISEASEETIOLOGY

STENOSIS REGURGITATION

1.RHD

2.CALCIFICATION

3.CONGENITAL

1.RHD

2.MVP

3.DCMP

4.IHD

5.ENDOCARDITIS

CLINICAL FEATURES OF MR

ACUTE MR CHRONIC MR

1. DYSPNEA

2. TACHYCARDIA

3. LOW VOLUME

PULSE

4. PANSYSTOLIC

MURMUR

1.ASYMPTOMATIC

2.FATIGUE

3.DYSPNEA

4.ORTHOPNEA

5.ATRIAL FIB.

6.HEAVING APEX BEAT

7.PANSYSTOLIC

MURMUR

INDICATIONS FOR SURGERY

1.SEVERE SYMPTOMS NYHA III OR IV

2.PROGRESSIVE LV DYSFUNCTION

3.UNCONTROLLED ENDOCARDITIS

4.SEVERE ACUTE MR

SURGICAL OPTIONS

1. OPEN MITRAL VALVE REPAIR

2. MVR WITH PRESERVATION OF ALL OR PART OF MV APPARATUS

3. MVR WITH REPLACEMENT OF MV APPARATUS

MITRAL STENOSIS

1. RHD IS THE MOST COMMON CAUSE

2. NORMAL MITRAL VALVE AREA IS 4-6 cm2

3. SIGNIFICANT SYMPTOMS DEVELOP ONCE THE AREA IS LESS THAN 1 cm2.

CLINICAL FEATURES OF MITRAL STENOSIS

1. ASYMPTOMATIC

2. FATIGUE

3. DYSPNEA

4. COUGH AND HEMOPTTYSIS

5. IRREGULAR PULSE

6. TAPING APEX BEAT

7. LOUD S 1

8. OPENING SNAP, MID-DIASTOLIC MURMUR

9. PATIENTS IN SINUS RHYTHM –PRE SYSTOLIC ACCENTUATION

INDICATIONS FOR SURGERY

1. SEVERE SYMPTOMS NYHA III OR IV

2. MODERATE OR SEVERE STENOSIS MITRAL VALVE AREA 1.5cm2

3. SYSTEMIC EMBOLI

TYPES OF PROSTHETIC VALVES

1.MECHANICALa. BALL AND CAGE VALVEb. TILTING DISC VALVEc. BILEAFLET VALVE

2.BIOLOGICALa. ALLOGRAFTSb. AUTOGRAFTSc. HETEROGRAFTS

I.STENTEDII. STENTLESS

POSTAOP CARE

5 “headaches”

● Hypothermia

● Hypovolemia

● Hypotension

● Hypertension

● Hemorrhage

• Improvements in postoperative care have centered on decreasing the adrenergic surge associated with surgery and halting platelet activation and microvascular thrombosis