Left Ventricular Aneurysm Resection and Remodeling (Dor Procedure)

What the Anesthesiologist Should Know before the Operative Procedure

Left ventricular (LV) aneurysm resection and LV repair were introduced by Cooley and colleagues in 1958, who described a linear repair of the left ventricle after aneurysm resection. This was the most common procedure for this indication until the late 1980s, when Vincent Dor and his colleagues introduced endoventricular patch plasty (EVPP). The Dor procedure considered a more physiologic repair than Cooley’s linear closure technique and was particularly favored when the aneurysm extended into the septum.

The anesthetic management of patients with ischemic congestive heart failure who present for LV aneurysm resection and remodeling is among the most challenging for the cardiac anesthesiologist.

These patients have little cardiac reserve, and the surgical procedure is associated with high morbidity and mortality. The surgeon’s purpose in remodeling the left ventricle is to relieve the excess demand placed on viable functional myocardium by akinetic infarcted myocardium. Surgical techniques for LV remodeling continue to evolve, but the EVPP described by Dor remains the most popular. Although this technique addresses the volume issue associated with dilated LV cardiomyopathy, it does not create the more physiologic conical shape that is associated with improved LV performance. Septal reshaping is another technique of LV remodeling that attempts to recover the more conical shape to the left ventricle, in contrast to the Dor procedure, which merely reduces volume.

In a recent article, Raja et al. compared the impact of linear repair and EVPP on early and late postoperative clinical outcome by evaluating the current best available evidence and found that both techniques have their own advantages and disadvantages. Current best available evidence (Grade B, Level 2c) from nonrandomized comparative studies failed to establish the superiority of one technique over the other.

Concept

LV systolic and diastolic function is optimal when the ventricle’s geometric shape is smaller and more elliptical than spherical. Optimal LV remodeling should restore the normal anatomic elliptical or conical shape to a dilated left ventricle and orient the stretched transverse myocardial fibers into a more oblique helical course. A typical example is a patient with an extensive anteroseptal MI involving the apex, or ischemic cardiomyopathy, whereby the dysfunctional myocardium leads to a more spherical LV geometric shape. The adjacent viable inferior wall is unable to contribute to effective contractile function and is thus rendered akinetic or dyskinetic due to tethering.

Technique

LV aneurysm resection and remodeling may employ a variety of surgical techniques. These include the Dor procedure, septal remodeling, Cooley’s linear, and Jatene’s circular external suture. LV reconstruction with endoventricular circular suturing and patching excludes the scarred LV wall. Circular patches are used for anteroseptoapical aneurysms, while triangular patches are used for posterior aneurysms. Although long-term results after LV remodeling surgery appear to be satisfactory, outcome appears to be better if the surgical technique results in a more conical LV shape, as opposed to volume reduction alone.

Indication

LV aneurysm surgery is indicated for the treatment of congestive heart failure, angina, ventricular dysrhythmias, and recurrent systemic embolization. The Dor procedure was originally intended to repair anteroseptal and apical LV aneurysms and scarring that develop after MI. Better acute-phase infarction management has drastically reduced the number of patients with post-MI LV aneurysms. Simultaneously, effective acute intervention after acute MI has increased the prevalence of patients with chronic ischemic heart failure. The more recent indication for the Dor procedure, therefore, is nonaneurysmal akinetic/dyskinetic dilated heart failure, particularly when the global ejection fraction (GEF) is less than 40% and contractile portion ejection fraction (CEF) is also less than 50% to prevent unfavorable evolution.

Contraindication

The Dor procedure is generally contraindicated in patients with right ventricular dysfunction, pulmonary hypertension, systolic pulmonary hypertension greater than 60 mm Hg (in the absence of concomitant MR), and LV dysfunction at the base of the heart. Cardiac transplantation is usually preferred over ventricular remodeling for patients with end-stage ischemic cardiomyopathy whose GEF is less than 20%, CEF less than 30%, cardiac output less than 1.5 L/min, and mean pulmonary artery pressure greater than 25 mm Hg.

Goal

The goal of the LV aneurysm resection and remodeling is to reduce LV end-systolic volume index (LVESVI), restore the ellipsoid shape of the LV, and increase EF. The elliptical geometry is achieved by exclusion of nonviable anteroseptal and apical areas, allowing the viable but tethered adjacent walls to more effectively contribute to functional contraction.

Additional Details

The Dor procedure is seldom performed alone, and usually requires 20-30 minutes of additional surgical time. It is usually performed concomitantly with coronary artery bypass grafting (CABG). Mitral valve annuloplasty/repair or replacement is also a commonly combined procedure because of the high prevalence of mitral regurgitation with LV dilation. Patients with ischemic cardiomyopathy, chronic congestive heart failure, and marked LV dilation are prone to ventricular arrhythmias that require cryoablation or LV endocardial resection, further extending surgical time with these additional procedures and interventions. These patients commonly require considerable inotropic support, attention, and occasionally mechanical ventricular assistance to separate from cardiopulmonary bypass.

Advantages

The main advantage to LV aneurysmectomy is the reduction in LV cavity size, which reduces wall tension and alteration of the geometrical shape to a more elliptical shape with a more oblique contractile pattern, rather than spherical. In a recent study, Dor et al. showed that the ejection fraction improved from 26% ± 4% preoperatively to 40% ± 8% at 1 month and 44% ± 11% at 1 year postoperatively. At these same time points, the end-diastolic volume index was reduced from 130 ± 43 mL/m2 to 81 ± 27 and 82 ± 25 mL/m2, respectively, while the end-systolic volume index was reduced from 96 ± 45 mL/m2 to 50 ± 21 and 47 ± 20 mL/m2, respectively. Kaza et al. demonstrated an improvement in LV function and a reduction in MR without concomitant mitral valve surgery for a majority patients. The results were obtained from a reduction in LV size and improved orientation of the papillary muscles. Older studies and a 2008 investigation by Sartipy and colleagues demonstrated improved survival and a marked improvement in symptoms.

Disadvantages

A study of over 1,000 patients comparing CABG alone to CABG with surgical ventricular reconstruction in ischemic heart failure (STICH trial) did not demonstrate an improved quality of life with surgical remodeling but significantly increased health care costs.

Alternatives

Medical therapy, heart transplantation, ventricular assist device implantation, total artificial heart, cardiac resynchronization devices, and mesh sleeves around the heart are possible alternative therapies. Recent studies have shown that shape procedures have achieved better long-term results when outcomes were compared with Dor.

SURGICAL TECHNIQUE

LV aneurysm resection and remodeling may employ a variety of surgical techniques. These include the Dor procedure, septal remodeling, Cooley’s linear, and Jatene’s circular external suture. LV reconstruction with endoventricular circular suturing and patching excludes the scarred LV wall. Circular patches are used for anteroseptoapical aneurysms, while triangular patches are used for posterior aneurysms. Although long-term results after LV remodeling surgery appear to be satisfactory, most studies including one published recently by Calafiore et al. show that outcome appears to be better if the surgical technique results in a more conical LV shape, as opposed to volume reduction alone.

The margin of viable myocardium is determined directly by the surgeon after review of myocardial viability studies. Echocardiography provides a more global sense of the aneurysm location. Intracavitary suction applied with an LV catheter can usually demarcate thin, infarcted, nonviable myocardium. An incision is made parallel to the interventricular septum on the left ventricle. An ovoid ring of Dacron or pericardium is placed with purse-string sutures encircling the ventriculotomy. A sizing device can be used to optimize the LV size and shape.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

LV aneurysm resection is usually an elective procedure but there are indications for urgent surgery. Patients presenting for emergency surgery have a ruptured LV aneurysm after acute MI and are severely hemodynamically compromised or supported by maximal mechanical and pharmacologic support. Elective cases generally involve patients who have failed medical management for treatment of congestive heart failure, angina, ventricular dysrhythmias, or systemic embolization from their LV cavity.

Unless emergent, these cases usually include exhaustive preoperative evaluation and rarely need further evaluation before proceeding.

Emergent: Patients presenting for emergency surgery have a ruptured LV aneurysm after acute MI and are severely hemodynamically compromised or supported by maximal mechanical and pharmacologic support.

Urgent: Patients presenting for urgent surgery have impending or contained LV aneurysm leakage necessitating urgent surgery before severe hemodynamic compromise.

Elective: Elective cases generally involve patients who have failed medical management for treatment of congestive heart failure, angina, ventricular dysrhythmias, or systemic embolization from their LV cavity.

2. Preoperative evaluation

The most common medical conditions to evaluate for this procedure are coronary artery disease (with or without angina), congestive heart failure (ejection fraction less than 35% is common), atrial and ventricular dysrhythmias (treated with ablation therapy or implanted cardiac defibrillator, mechanical ventricular assistance (intra-aortic balloon pump or LVAD), mitral regurgitation, diabetes mellitus, peripheral vascular disease, chronic obstructive pulmonary disease (COPD), and renal failure.

Medically unstable conditions warranting further evaluation or treatment include:

• New-onset atrial fibrillation

• Carotid bruit

• Acute mental status changes

Delaying elective surgery may be indicated in the presence of:

• MI within the last 3-7 days

• Acute renal failure

• COPD exacerbation

• Systemic infection

• Any major medical condition that can be improved with medical therapy and expected to reduce associated perioperative morbidity and mortality.

3. What are the implications of co-existing disease on perioperative care?

N/A

b. Cardiovascular system

Cardiac surgery is generally associated with higher mortality after acute MI. If possible, surgery should be delayed for 3-7 days after an acute event. Inferior wall infarction can lead to severe right ventricular (RV) dysfunction, in which case surgery should be delayed for more than 4 weeks to allow the RV sufficient time to recover.

These patients usually present with multivessel CAD requiring coronary revascularization. Acute anginal symptoms should be treated as there may be little coronary reserve and less myocardial functional reserve, with propensity to develop CHF easily with acute ischemia.

Patients may benefit from preoperative beta-blockade and antiarrhythmic therapy to lower the incidence of postoperative atrial fibrillation.

The function of all implanted cardiac electrical devices (AICD, pacemaker) should be evaluated by an electrophysiologist and a plan formulated for their perioperative management.

c. Pulmonary

Respiratory function should be optimized before elective cardiac surgery. Exacerbations of pulmonary disease should be treated appropriately, with management of smoking cessation, and antibiotic therapy initiated for pneumonia or bronchitis.

Patients at high-risk patients for pulmonary complications may benefit from inspiratory muscle training, which is associated with a reduction in postoperative pulmonary complications among CABG patients.

Reactive airway disease: Bronchodilator and or steroid therapy for treatment of exacerbation and to improve respiratory function.

d. Renal-GI:

Renal function can be optimized by maintaining normal mean arterial pressure, normovolemia, and avoidance of nephrotoxic agents during the perioperative period. Cardiac surgery is optimally avoided immediately after cardiac catheterization in renal compromised patients because of the dye load.

e. Neurologic:

Acute issues: Prior history of CVA, TIA, seizures, organic brain syndrome, and cognitive dysfunction should be documented. Any acute neurologic changes should be investigated.

Chronic disease:ACC/AHA guidelines recommend selective carotid screening be considered in the following high-risk patient groups: age greater than 65 years, left main coronary artery stenosis, carotid bruit, peripheral vascular disease, history of smoking, and history of transient ischemic attack or stroke.

f. Endocrine:

Perioperative glucose control usually involves insulin infusion and should be managed according to institutional guidelines.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

N/A

4. What are the patient's medications and how should they be managed in the perioperative period?

Patients scheduled to undergo LV remodeling can easily develop CHF, and must be medically managed before their cardiac surgery to avoid perioperative pulmonary edema. Common medications include digoxin, beta-adrenergic blockers, milrinone, ACE inhibitors, angiotensin inhibitors, dobutamine, and alpha-1 agonists. Patients with recurrent angina may be prescribed various forms of nitrates, aspirin, and morphine.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Patients with coronary stents receiving clopidogrel should discontinue this medication 7-10 days prior to surgery for concerns of postoperative bleeding, and because coronary revascularization is expected to bypass the recurrent coronary stenoses.

ACE inhibitors and angiotensin receptor blockers should be stopped 12-24 hours prior to surgery to avoid hypotension due to these medications.

i. What should be recommended with regard to continuation of medications taken chronically?

Metabolic

Diabetic patients undergoing cardiac surgery should have glycemic control with perioperative insulin infusions. Subcutaneously administered insulin has variable absorption, particularly during hypothermic cardiopulmonary bypass and rewarming.

Psychiatric

Patients receiving monamine oxidase inhibitors should be evaluated by their psychiatrist and anesthesiologist 3 weeks prior to surgery and should be advised to switch or discontinue this type of medication if possible.

Other

Aspirin should not be stopped because of the risk of LV clot formation and subsequent systemic arterial embolization.

Eptifibatide and tirofiban should be discontinued 4-6 hours before cardiac surgery. Abciximab should be discontinued 12-24 hours before surgery.

NSAIDs should be discontinued at least 48 hours before surgery.

Diuretics should be discontinued on the day of surgery, except HCTZ and triamterene, which should be continued (if taken for hypertension).

Autoimmune medications

Continue methotrexate on day of surgery unless risk of acute renal failure.

Discontinue etanercept (Enbral) 2 weeks prior to surgery.

Discontinue infliximab (Remicade) 6 weeks prior to surgery.

Discontinue adalimumab (Humira) 8 weeks prior to surgery.

Herbals and nonvitamin supplements

These should be stopped 7 days prior to surgery.

j. How To modify care for patients with known allergies –

Warkentin and colleagues outlined management guidelines for patients with heparin-induced thrombocytopenia (HIT) undergoing cardiac surgery. An immunoassay for PF4/heparin antibodies is recommended and, if positive, a platelet activation assay is performed. Patients who are PF4/heparin antibody negative or antibody positive by immunoassay but antibody negative by platelet activation assay, may proceed with cardiac surgery using unfractionated heparin (UFH) for CPB. Preoperative and postoperative anticoagulation should be performed with a nonheparin anticoagulant.

Patients with a history of HIT whose platelet counts have recovered but are heparin/PF4 antibody positive should have surgery delayed if possible until a platelet activation assay is negative, and then surgery can be performed using UFH during CPB. If delaying surgery is not an option, use of a nonheparin anticoagulant (e.g., bivalirudin) is recommended over UFH for CPB. In patients with HIT who remain thrombocytopenic and are heparin/PF4 antibody positive, the preferred strategy is to delay surgery until the platelets have normalized and the heparin/PF4 antibodies are negative or weakly positive. However, if delaying surgery is not feasible, alternative anticoagulation regimens during CPB should be considered.

k. Latex allergy- If the patient has sensitivity to latex (e.g. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

In addition to other standard precautions, use a latex-free pulmonary artery catheter.

l. Does the patient have any antibiotic allergies- [Tier 2- Common antibiotic allergies and alternative antibiotics]

In patients for whom cefazolin is the appropriate prophylactic antibiotic for cardiac surgery, administration within 60 minutes before the skin incision is indicated (Class I, Level of Evidence A). The preoperative prophylactic dose of cefazolin for a patient of greater than 80 kg body weight is recommended to be 2 g (Class I, Level of Evidence B).

A second dose of 1 gram of cefazolin is administered to patients with normal renal function when the duration of surgery is greater than 4 hours. If discontinuation of CPB is imminent, the repeat dose is administered on separation from bypass to maximize effective blood levels (Class I, Level of Evidence B).

It is recommended that patients given vancomycin for their prophylactic antibiotic for cardiac surgery, should receive a dose of 1-1.5 g or a weight-adjusted dose of 15 mg/kg administered intravenously slowly over 1 hour, with completion within 2 hours of the skin incision (Class I, Level of Evidence A). A second dose of vancomycin of 7.5 mg/kg may be considered during CPB, although its usefulness is not well established (Class IIb, Level of Evidence C).

For patients who receive an aminoglycoside (usually gentamicin, 4 mg/kg) in addition to vancomycin before cardiac surgery, the initial dose should be administered within 1 hour of the skin incision (Class I, Level of Evidence C). Redosing an aminoglycoside during CPB is not indicated and may be harmful (Class III, Level of Evidence C).

With regard to choice of alternative prophylaxis in the presence of allergy, vancomycin appears to be the best choice, owing to its gram-positive coverage and particular coverage of methicillin-resistant S. aureus. There are concerns over lack of gram-negative coverage with vancomycin relative to cephalosporins. For this reason, an aminoglycoside, usually gentamicin, should be added.

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia

Documented: avoid all triggering agents such as succinylcholine and inhalational agents.

• Proposed general anesthetic plan:

• Ensure MH cart available: [MH protocol]

5. What laboratory tests should be obtained and has everything been reviewed?

Hemoglobin levels (g/dL):

Electrolytes:

Coagulation panel:

Imaging:

Coronary angiography and assessment of LV by ventriculography, right-sided heart catheterization to measure right-sided pressures and cardiac output, carotid Doppler, positron emission topography (PET scan)/dobutamine stress echo (DSE)/cardiac myocardial resonance (CMR) with gadolinium and TEE or TTE.

Other tests:

Echo color Doppler saphenous vein mapping.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

The anesthetic management is based on the recognition that patients have poor myocardial reserve and are very preload dependent with an EF<30%. Since a fast track approach is not advisable for these patients, a high dose opioid technique with fentanyl (~20 mcg/kg) is preferable. A minimal amount of inhaled anesthesia is used to supplement the primary opioid anesthetic and to reduce the incidence of awareness.

Anesthetic management considers optimal heart rate, preload, afterload, contractility, myocardial oxygen balance, critical coronary stenosis, pulmonary hypertension, systemic vascular resistance, hemodynamic instability, cardiac rhythm, and mitral regurgitation. Optimal physiologic management may differ among all the existing pathophysiologies, making the anesthetic management challenging.

Intraoperative transesophageal echocardiography (TEE) is essential for several reasons.

Pre CPB

• Ensure proper positioning of the intra-aortic balloon pump

• Assessment of preload and ventricular function

• Assessment of mitral valve function to determine the feasibility of repair or replacement

• Detailed assessment of the LV wall motion to help guide optimal LV resection and remodeling

• Presence of intracavitary LV thrombus

Post CPB

• Assessment of LV preload and contractility

• Assess the previously akinetic/dyskinetic regional LV wall segments for improved contractile function. Integrity of the patch and suture line should also be assessed

• Adequacy of the mitral valve intervention

• Global contractility

The challenges after CPB are similar to those before CPB, but in addition:

Intra-aortic balloon pump:

Placement should be strongly considered as it may be helpful, if not ess ential.

Low SVR :

Norepinephrine, epinephrine, or vasopressin may all be effective; the latter may be more effective in preserving renal perfusion without excessive increase in SVR and PVR.

Low cardiac output :

Milrinone, dobutamine, or epinephrine are all good options. Milrinone also decreases the associated pulmonary hypertension.

Since cardiac output is expected to decrease, atrioventricular synchrony is helpful. Biventricular pacing should be resumed at 90-100 beats per minute (assuming no ischemia) taking into account the smaller LV.

b. General Anesthesia

These procedures are exclusively performed under general anesthesia. Regional anesthesia is not a consideration.

6. What is the author's preferred method of anesthesia technique and why?

What prophylactic antibiotics should be administered?

The Society of Thoracic Surgeons recommends cefazolin as the initial antibiotic of choice. The recommended dose is 1 g for weight <80 kg and 2 g for weight >80 kg. Redosing is recommended every 2-5 hours. For patients with serious allergy to beta-lactam antibiotics, vancomycin is recommended combined with clindamycin.

What do I need to know about the surgical technique to optimize my anesthetic care?

LV remodeling is usually performed with other cardiac surgical procedures, including CABG, mitral valve surgery, or ablation.

Goals of anesthetic management include:

• Maintenance of optimal myocardial oxygen demand and supply ratio

• Monitoring for and prevention of myocardial ischemia by maintaining baseline arterial blood pressure, low heart rate, low filling pressures

• Control of afterload

• Prevention of acidosis

Most common intraoperative complications

Cardiac

• Infarction

• Ischemia

• Myocardial stunning

• Arrhythmias

• If MVR was performed, unintentional suture placement into the circumflex coronary artery and associated regional wall motion abnormalities.

Pulmonary

• Pump lung

• Atelectasis

• Pneumonia

Neurologic

• Stroke

• Encephalopathy

• Cognitive dysfunction

a. Neurologic

The postoperative neurologic complications are the same as for any patient who has undergone CPB support.

b. If the patient is intubated, are there any special criteria for extubation?

Cardiovascular status must be stable before weaning ventilatory support.

c. Postoperative management

Postoperative pain management can be achieved with IV bolus or continuous infusion of fentanyl prior to extubation and PCA narcotics after extubation.

Patients recover in the cardiothoracic ICU and are transferred to a step-down or telemetry unit.

The most common postoperative complications are

• Hemodynamic instability

• Bleeding

• Low cardiac output

• Arrhythmias

• Hypoxia

• Hypothermia

• Renal failure

• Neurologic dysfunction