Mark Roeser, MD, and Ravi Ghanta, MD
Concept
- Indications for combined valve/coronary artery bypass grafting
- Preoperative considerations
- Critical steps in valve/coronary artery bypass grafting
Chief complaint
“A 64-year-old man with chronic exertional chest pain is referred to you with moderate aortic stenosis on a TTE obtained by his primary care physician. On follow up catheterization he is found to have 60% RCA stenosis, 80% LAD stenosis, and a 70% circumflex lesion.”
Differential
Either the CAD or the aortic stenosis could be contributing to his symptoms.
History and physical
Ask and evaluate for evidence of syncope, angina, CHF, pulmonary edema, dyspnea, and other comorbidities which may factor into your decision regarding the aortic valve.
Tests
Careful review of the cath, echo, CXR, EKG and baseline labs. Catheterization and exercise testing can be used to clarify aortic valve stenosis.
Index scenario (additional information)
“Exercise testing shows a mean gradient of 45 mmHg with exercise. Review of the echo suggests a highly calcified aortic valve. He denies history of dyspnea or syncope.”
Treatment/management
Indications for concomitant AVR in patients who require a CABG
- All patients with moderate to severe aortic stenosis
- All patients with moderately severe to severe aortic regurgitation
- Consider in patients with mild AS and moderate to severe calcification or rapidly progressing disease (decrease in AVA 0.3 cm2 per year or increase in gradient 15-20 mmHg per year)
- Consider in patients with moderate AI
Indications for concomitant CABG in patients who require an AVR
- Any lesion > 70%
- LM lesion > 50%
- “reasonable” to consider bypassing lesions > 50% (LIMA for LAD)
In the above clinical scenario, the patient’s symptoms are most likely due to the coronary disease, but he should also have the aortic valve replaced at the time of surgery. The data suggests that he will have a lower freedom from reintervention rate with this approach but not necessarily improved survival. Thus, you need to exercise judgement and balance the risks and benefits of an AVR with moderate AS in the setting of CABG. Frail, older patients with multiple comorbidities may benefit from an expeditious operation that addresses the CAD and leaves the moderate AS behind. On the other hand, a younger patient with few comorbidities will benefit from the decreased reintervention rate. You should also factor in the rate of progression of the aortic valve disease (see chapter on Aortic stenosis). Also, patients with moderate AS and low cardiac output should have the aortic valve replaced at the time of CABG to reduce afterload.
Potential questions/alternative scenarios
“A 58 year-old woman with history of moderate mitral stenosis secondary to rheumatic fever undergoes a cardiac catheterization for exertional chest pain. She is found to have an 80% lesion in the proximal LAD, 70% RCA and 60% OM2 not amenable to PCI.”
Indications for concomitant mitral valve surgery in patients who require a CABG:
- Mitral stenosis: there are no uniform guidelines regarding mitral stenosis in the setting of a CABG but in general patients who require CABG should have the diseased mitral valve replaced if they meet criteria for an isolated MVR (refer to Mitral stenosis chapter) – i.e., moderate to severe MS with NYHA III-IV, asymptomatic with PAP > 60 mmHg, recurrent embolic events, new onset afib, or evidence of RV dysfunction. If a patient does not meet criteria for mitral replacement but has severe MS it is reasonable to replace. For moderate MS not meeting indications for MVR this is more controversial. The decision should factor in whether the patients coronary induced symptoms are potentially due to MS. You might also consider checking the catheterization to clarify the degree of mitral stenosis according to the Gorlin formula if there is a discordance between the echo and clinical presentation.
- Gorlin formula: valve area (cm2) = CO / (HR x systolic ejection period (sec) x 44.3 x sq root mean gradient)
- Structural mitral regurgitation: severe or moderately severe mitral valve regurgitation secondary to structural valve degeneration (i.e., ruptured cord, leaflet prolapse, etc..) should undergo repair or replacement at the time of CABG. This would be an unusual presentation since most patients with dominant CAD and concomitant mitral regurgitation have ischemic MR. In the absence of a structural lesion assume ischemic MR (below).
- In patients with ischemic (or “functional”) mitral regurgitation. Severe MR can get a ring annuloplasty repair or mitral valve replacement. Repair when feasible but replacement is acceptable with similar survival, especially for complex jets or sicker patients. Moderate MR is controversial. Patients may get either a ring annuloplasty, replacement or nothing (NIH trial ongoing). Addressing the MR may improve symptoms and decrease the chance of worsening MR. The decision depends on degree of symptoms attributable to the MR as well as comorbidites that make extra cross clamp time more hazardous.
Indications for concomitant CABG in patients who require mitral valve surgery:
- Any lesion > 70%
- LM lesion > 50%
- “reasonable” to consider bypassing lesions > 50% (LIMA for LAD)
In the above scenario, the patient needs to have her right sided heart pressures clarified. If she has moderate-severe pulmonary hypertension (PAP > 50 mmHg at rest or > 60 mmHg with exercise) then the mitral valve should be replaced. If she does not have pulmonary hypertension, new onset afib, right ventricular dysfunction, or embolic events then you should go back to the history and decide whether the moderate MS is more or less than likely to be contributing to her symptoms. Also factor in her comorbidities to see how well she will tolerate the extended cross clamp. In this scenario, exertional chest pain, as reported by the patient, is most consistent with coronary disease and is less likely to be from mitral disease. If she were older, frail with multiple comorbidities it would be reasonable to leave the mitral valve alone. On the other hand, if she could tolerate the extra operative time then MVR would remove the mitral disease as a potential source of her symptoms and source of postoperative problems. Thus, moderate stenosis should be left alone if unlikely to be involved in the patient’s clinical presentation especially in the absence of an isolated indication for MVR. It can be considered if MS is borderline severe or likely to cause problems in the future in a good surgical candidate.
Operative steps
Combined aortic valve replacement/CABG
- Transesophageal echo (TEE).
- Median Sternotomy.
- LIMA + SVG procurement.
- Aortic and right atrial cannulation.
- Antegrade cardioplegia catheter. Retrograde cardioplegia catheter ideal (especially if tight proximal coronary lesions, significant LV hypertrophy, or significant AI).
- LV vent ideal but not required (institution/surgeon dependent).
- Aortic cross-clamp.
- Cardioplegia. It is important to appreciate that a CABG/AVR carries a higher mortality and is longer than any of the component procedures done in isolation. Cardioprotection for this case is critical and you must think through your protection strategy carefully before you start.
- moderate – severe AI – retrograde induction and consider LV vent to avoid ventricular distension. Make sure the retrograde is in perfectly. Can try to give some through the antegrade but stop if distention occurs.
- high grade proximal coronary lesions – antegrade is unlikely to be sufficient. Plan on antegrade, retrograde and direct cardioplegia down the vein grafts.
- Along these same lines, it is helpful to get to the distal anastomosis and particularly the right distal done ASAP. This will allow you to deliver extra cardioplegia directly down the coronary conduit and protect the RV. Do the same for the circumflex lesion.
- For the LAD you can do the LIMA to LAD and leave it clamped or do the LIMA to LAD following the AVR.
- Make sure you are administering a full dose of cardioplegia every 15-20 minutes.
- Size up the proximals with the heart distended.
- Complete the AVR and close the aortotomy.
- Proximal anastomosis.
- Wean from CPB.
- Summary: distals > AVR > proximals.
Operative sequence for mitral valve repair/replacement/CABG
- TEE.
- Median sternotomy.
- LIMA + SVG procurement.
- Aortic and bicaval cannulation.
- Aortic root vent, antegrade and retrograde cardioplegia.
- Distal anastomoses.
- Size up the proximals with the heart engorged.
- Left atrial vs. transseptal approach for mitral valve repair or replacement.
- Consider left atrial ablation +/- LA appendage ligation if concomitant atrial fibrillation prior to the mitral replacement due to the higher risk of AV rupture with manipulation of the heart (see chapter Afib/MVR for further details on management of concomitant AF).
- Mitral repair or replacement.
- Key concept is to perform the distal anastomosis first so that heart manipulation/lifting can be minimized after mitral valve replacement is performed. Additionally, performing distal first could facilitate additional cardioprotection down the grafts.
- Proximal anastomosis.
- Summary: distals > mitral repair/replacement > proximals.
Operative sequence for aortic and mitral valve surgeries plus CABG
- TEE.
- Aortic and bicaval cannulation with mild systemic hypothermia 32-34° C.
- This is definitely a longer operation. Systemic hypothermia and excellent cardioprotection increase the chances of getting through it safely.
- Aortic: root vent, antegrade and retrograde cardioplegia.
- Distal anastomoses and size up the proximals with the heart distended.
- Aortotomy and debride the aortic valve. The concept is to debride the aortic valve before performing mitral valve repair/replacement since debriding after a mitral valve repair/replacement can be problematic.
- Mitral valve replacement/repair via transseptal or left atrial exposure (do any afib procedures first)!
- AVR.
- Close the aortotomy and perform the proximals.
- Wean from CPB.
- Summary: distals > debride aortic valve > mitral > AVR > proximals.
Potential questions/alternative scenarios
“You have performed the CABG AVR but coming off CPB the CI is 1.7 and the heart function is decreased compared to baseline. You are on high doses of inotropes and vasopressors. The echo shows that the valve is well seated with no regurgitation and no significant gradient. The RCA appears to have flow in it by echo. There are no regional wall motion abnormalities. You assess the position of all your grafts which appear satisfactory and use a flow probe which reveals good flow in all the grafts. Your cross-clamp time was 2 hours long, but you had considerable difficulty with the position of the retrograde throughout the case. How should you proceed?”
These procedures are longer than usual. Cardioprotection must be carefully carried out. Note that if you perform the mitral via transeptal approach consider direct retrograde insertion into the coronary sinus. Perform the distals first and deliver cardioplegia directly down the distals. In this case the most likely diagnosis is cardiogenic shock from poor protection. You can rest the heart on full flow for 10-15 minutes (make sure the heart is completely decompressed) and see if you recover but ultimately it may be difficult to leave the OR without the aid of a IABP. If the shock persists or worsens in the ICU over the next 12 hours consider an angiogram to assess the grafts.
Pearls/pitfalls
- In general, combined procedures should be performed when indications for each procedure are met. For example, an AVR plus CABG can be performed if the patient meets the indications for AVR and meets the indications for CABG. When a patient however meets the surgical criteria for one cardiac operation (for example CABG), the threshold criteria for performing an additional procedure (for example AVR for moderate AS) maybe lowered after considering the patients overall state.
- Plan out your cardioprotection strategy carefully – plan on retrograde, antegrade and cardioplegia down the coronary conduits.
- General sequence is distals, aortotomy, MVR, AVR, proximals.
- CABG/AVR: distals > AVR > proximals
- CABG/MVR: distals > MVR > proximals
- CABG/AVR/MVR: distals > debride aortic valve > mitral > AVR > proximals
- Reasonable to bypass coronary lesions greater than 50% at the time of a valve operation; mandatory to bypass LM > 50% or any other reasonable target > 70%.
