Flashcards in CV surgery Deck (44)
How big must a block be for intervention to be needed?
When block reaches 70% of coronary diameter or 50% of left main artery
What are indications for CABG?
-Chronic disabling angina or unstable angina unresponsive to medical therapy
-Triple vessel disease esp with Left main coronary artery
-Continuing chest pain after MI
-Symptoms after prior CABG
-Coronary artery aneurysm
What are the types of conduits for CABG and pros/cons?
Venous: Saphenous vein graft (SVG)
Pros: Long vein, easy to access, straight.
Cons: Long term patency rate / graft occlusion not as good (risk decreased with early ASA)
Arterial: LIMA / RIMA, radial, gastroepiploic arteries
Pros: Tougher, muscular layer more durable and patency better. Rarely affected by atherosclerosis
Cons: Slower to harvest, may cause bleeding, arterial spasm (treated with ca ch blockers)
How is LIMA / RIMA CABG done?
Left / Right Internal Mammary Artery originates from the subclavian artery and is dissected from the chest wall but origin left intact. Other end attached post blockage, so only one anastomosis is necessary.
Principles of cardiac surgery
-Heart is stopped and cooled by administration of cardioplegia (mix of blood and electrolyte solution high in potassium)
-Blood diverted from right heart to heart/lung machine and then returned to arterial circulation
-Temporary epicardial pacing wires on right ventricle and may be placed on right atrium
-Mediastinal and possibly pleural chest tubes placed to prevent blood accumulation post-op
-Sternal bone closed with stainless steel wires
-Insulin shift may be required if serum K remains high
What are negative effects of using Cardio Pulmonary Bypass?
1) Induction of SIRS with possible multi organ failure
2) Risk of stroke and embolism
3) Risk of bleeding (high dose heparin administered to prevent circuit clot)
How does the heart get restarted after cardio-pulmonary bypass?
Oxygenated blood infused via cardioplegia circuit to wash high potassium solution out. Heart usually beats spontaneously but may fibrillate requiring defib and use of anti-arrythmic meds. Pt may be bradycardic requiring temporary pacing.
Pts that have difficulty weaning due to hemodynamic instability may require inotropic support and IABP
What is the post-op care for CABG?
-Continuous ECG monitoring 48-72 hrs with ST segment analysis
-ASA 100-325mg daily starting 6hrs post op (Improve SVG patency rate, decrease mortality)
-Afib prophylaxis (MgSo4, amio)
-Statins (aggressive LDL cholesterol lowering reduces rate of graft atherosclerosis)
-ACE inhibitors (stated when pt is stable and if taken pre-op and EF < 40%, HTN, DM, CKD)
What are 2 categories of valvular heart disease?
1) Stenosis --> Narrowing of valve orifice, valve unable to open normally causing blood accumulation (and higher pressures) in the proximal chamber. Chamber has to work harder to generate higher pressures to eject blood
2) Insufficiency --> Regurgitation results in leakage of blood backward through a valve which does not close properly.
What are causes of valvular heart disease?
-Infection and inflammation, endocarditis
-Ischemic damage --> Papillary muscle rupture
-Abnormal heart wall movement secondary to infarction can impair valve function
Valve repair vs valve replacement?
Valve repair preferred because it maintains normal geometry and function of ventricle and avoids risk associated with chronic anticoagulation and prosthetic valve failure
What are the main procedures for valve repair?
VALVULOPLASTY performed to open a stenotic valve.
-COMMISSUROTOMY --> Split/incision is made through the commissures (fused valve leaflets). Can be done in cath lab percutaneously by balloon valvuloplasty or in OR. Leaflets must be pliable with no calcification or insufficiency
-ANNULOPLASTY --> Done for valvular regurg, provides support for annulus which allows the leaflets to close properly. Esp for mitral or tricuspid insufficiency associated with a dilated valve annulus leading to failure of leaflets to close
What are other procedures for valve repair?
Repair of structural supports (chordal reimplantation, addition of new chords)
Resection / reconstruction of leaflets (removal of access tissues from leaflets, covering holes or tears with a tissue patch)
Compare tissue vs mechanical valve replacements
-Porcine or bovine
-Anticoagulants not required after 3 months
-Indicated for children, young females, pts with bleeding disorders, peptic ulcer
-Metal and synthetic
-Indicated for adults < 50yrs
-Life long anticoagulant required
-Good durability, more common
What is the biggest risk during aortic valve replacement?
Risk of dislodging calcification deposits from around the valve causing a systemic emboli
What is a transcatheter aortic valve replacement (TAVR)? How is it done?
When open aortic valve surgery is too risky, TAVR involves placement of new tissue valve within the native valve using catheters that deliver the valve through the aorta (femoral approach) or apex of LV via an incision in the chest wall (if pt has inadequate vascular access).
Catheter passes through the diseased aorta then balloon is inflated crushing the native valve to the side in order to position the new valve at the site.
How is a mitral valve replacement done? What is the biggest risk during mitral valve replacement?
Incision made in left atria to access valve site (OPEN HEART). Risk of entrapping air within the heart, careful "de-airing" required or pt will have a large embolus
What are potential complications of all prosthetic valve replacements?
-Valve thrombosis / emboli (mechanical valves require anticoag for life, tissue valves for 3 months)
-Endocarditis (prophylactic antibiotics)
What is aortic stenosis patho and S&S?
Is the narrowing of the opening of the aortic valve. Heart compensates by hypertrophy, left atria enlargement due to pressure overload. Diastolic dysfunction occurs due to hypertrophy, eventually leads to ventricular dilation and decreased contractility
S&S: Syncope, angina, dyspnea, harsh medium pitched murmur during systolic radiating into carotid arteries
What is aortic stenosis intervention and post op issue?
Therapies if symptomatic: Replacement or TAVR
Post op issues:
-HTN (LVH = strong myocardium) ** Vasodilators can greatly reduce preload and if pts are preload dependent then BP becomes very labile
What is the most likely cause of low CO for hypertrophied heart?
-In Hypertrophied heart, low CO most likely related to hypovolemia despite high filling pressures (high PAD or wedge is the norm for the pt)
What is aortic regurg / insufficiency patho and S&S?
Inability of aortic valve to close completely, blood flows backward during diastole from aorta back to LV.
Initially heart compensates for increased volume by hypertrophy but eventually LV thins and dilates. VOLUME OVERLOAD leads to high filling pressures, dilated LA, potential pulm HTN
S&S: Diastolic murmur, may have S3. Increased pulse pressure (high systolic d/t high stroke volume, low diastolic d/t lower pressure in aorta from regurgitant blood flow), signs of heart failure (pulm. edema, peripheral edema, ascites) or may be asymptomatic
What is aortic insufficiency therapies?
-Good BP control to prevent increases in systemic pressure (would increase regurg)
-HF meds as needed
-Aortic valve replacement
What is mitral stenosis patho and S&S?
Narrowing of the opening of mitral valve leading to reduced filling of the LV
Valves and sometimes chordae tendinae become thickened, LA enlargement, pulm HTN, RV hypertrophy
S&S: Develops over time, insidious, general malaise, fatigue, SOB. Diastolic murmur over apex with opening snap (accentuated S1), left parasternal heave (RV hypertrophy)
What are mitral stenosis therapies and interventions?
-Na restriction and intermittent diuretics of pulmonary edema.
-Anti-arrythmic agents due to risk of atrial arrythmias
-Anticoags if afib, prior embolitic events, LA thrombus
-Percutaneous repair in cath lab (valvuloplasty)
What are post-op issues for valve interventions?
-Heart blocks (mitral, aortic valve near AV node)
-May require higher filling pressures, inotropes
-Higher risk of post op RV dysfunction d/t pre-existing pulm HTN
-Anticoags and afib prophylaxis
What is mitral regurgitation and S&S?
Inability of mitral valve to close completely, blood flows backward during systole from LV back to LA
Left atrial enlargement, pulm. HTN, increased volume in LA returns the LV increasing LV volume which initially hypertrophies then thins and dilates.
S&S: Systolic murmur at the apex, pulm edema, signs of heart failure, may be asymptomatic if chronic
What are mitral regurgitation therapies and interventions?
Meds reducing afterload (ACE inhibitors, ARBs)
MV repair or replacement
Percutaneous repair in cath lab (mitraclip)
How is replacement of the ascending aorta / hemiarch done?
Surgery performed through a median sternostomy, aorta is unable to be cannulated for connection to the bypass machine in the normal manner so aorta is cross-clamped and circulatory arrest is stablished. Surgeon may or may not choose to perfuse the brain during arrest period. Aneurysm is over-sewed or removed and a graft inserted.
If dissection extends down into sinus of valsalva, then aortic valve needs to be replaced and coronary arteries re-inserted into an aortic graft. Procedure called BENTALL procedure.
Post op important to control systolic BP to limit stress on aorta