Minimally Invasive ASD/VSD

What the Anesthesiologist Should Know before the Operative Procedure

Adult patients presenting for minimally invasive ASD (atrial septal defect) or VSD (ventricular septal defect)repair may have a wide range of pathologies. The location, size, and type of the shunt lesion can have major implications on the planned intervention, surgical approach, and, by extension, conduct of anesthesia. Consequently, anesthesiologists caring for these patients should have a grasp of the basic variations of both atrial and ventricular septal defects.

Atrial septal defects

1. Primum ASD: “Partial endocardial cushion defect” may be associated with mitral or tricuspid valve abnormalities (most commonly, cleft anterior leaflet of the mitral valve).

2. Secundum ASD: Most common shunt lesion in the adult population. Defect in septum secundum/fossa ovalis anatomic location. More common in female patients (2:1 female-male ratio).

3. Sinus venosus ASD:

i. SVC type: By far the most common sinus venosus defect. Generally located at or near the superior vena cava (SVA) and right atrium (RA) junction, and associated with partial anomalous pulmonary venous return in which some of the right sided pulmonary veins drain into the SVC and/or the right atrium.

ii. IVC type: Extremely uncommon. Located at or near the inferior vena and (IVC) and RA junction.

4. Unroofed coronary sinus: Characterized by a coronary sinus defect that results in an abnormal comunication between the coronary sinus and the left atrium.

Ventricular septal defects

1. Subarterial or conal defect: Lies beneath the aortic/pulmonic valve on the outlet septum. May be associated with aortic regurgitation secondary to leaflet prolapse.

2. Perimembranous VSD: Involves the membranous septum adjacent to the mitral or tricuspid valve. Represents the vast majority of VSDs (>80%).

3. Inlet VSD: Located at the RV (right ventricular) inlet and inferior to the subvalvular apparatus of the tricuspid valve.

4. Muscular VSD: A VSD completely surrounded by myocardial muscle. Often, multiple defects of the ventricular septum present, leading to a “Swiss cheese” appearance of the muscular septum.

In general, patients with a patent foramen ovale or small secundum ASD may be candidates for percutaneous closure with Amplatzer occluder devices in the cardiac catheterization laboratory. Some centers have also utilized percutaneous closure techniques for perimembranous VSDs in adults with acceptable intermediate term results. We focus the remainder of this chapter on adult patients presenting for surgical (nonpercutaneous) repair of atrial or ventricular septal defects, utilizing minimally invasive techniques.

“Minimally invasive heart surgery” is a catch-all phrase that can refer to surgery through a right thoracotomy incision with conventional central cannulation for cardiopulmonary bypass, robotic surgery through multiple small incisions on the chest wall with total percutaneous peripheral cannulation, or any permutation in between. In general, the more ‘”minimally invasive” the approach, the more intimately involved the anesthesiologist is in the preparation for and conduct of cardiopulmonary bypass. Obviously, it is of utmost importance to communicate with the surgical, perfusion, and nursing teams prior to commencing to determine the planned surgical approach and cannulation scheme.

1. What is the urgency of the surgery?

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

The most common presenting symptoms of adults with atrial or ventricular septal defect are cryptogenic stroke, new onset arrhythmias, and/or increasing shortness of breath on exertion. As such, these cases are typically scheduled electively and can be delayed if necessary to obtain pertinent preoperative information or to optimize the patient medically.

• Emergent: Ischemic or post-infarction VSDs are a surgical emergency. These patients are critically ill, often hemodynamically unstable, and are not typically considered candidates for minimally invasive techniques.

• Urgent: Most of these patients require significant preoperative evaluation to elucidate the nature of the specific lesion and, therefore, surgery is performed on an elective basis.

• Elective: The overwhelming majority of minimally invasive cases are scheduled electively for surgery.

2. Preoperative evaluation

Sequelae of shunt lesions

1. Right ventricular dysfunction: Both atrial and ventricular shunt lesions lead to volume overload of the RV as it is forced to adapt to both normal venous return as well as the abnormal shunt flow from the left heart. This chronic volume overload predisposes patients to RV dilatation and systolic dysfunction. Preoperative echocardiographic assessment of RV size and function should be available for review.

2. Pulmonary hypertension: A minority of adult patients (5%-10%) with shunt lesions develop pulmonary hypertension. If uncorrected, the right-sided pressures will exceed that of the left heart; reversal of the pressure gradient across the ASD will reverse the shunt flow direction, resulting in right-to-left flow. This phenomenon is known as Eisenmonger’s syndrome. Patients in whom the preoperative echocardiogram is suggestive of elevated PA systolic pressure warrant right heart catheterization for further evaluation of pulmonary hypertension. Severe pulmonary hypertension (>2/3 systemic pressures) with near equalization of systemic and pulmonic flows is considered a sign of irreversible remodeling of the pulmonary vasculature and a contraindication to surgical repair. A subset of these patients may respond to long-term therapy with intravenous pulmonary vasodilators (epoprostenol) and become surgical candidates.

3. Cryptogenic stroke: The presence of intracardiac shunt places patients with ASD and VSD at risk for paradoxical emboli and stroke. Patients should be evaluated carefully for new onset signs or symptoms of stroke, as the consequences of full heparinization in the setting of a hemorrhagic stroke are potentially devastating. If there is evidence of a fresh cerebrovascular event, in most cases, surgery should be delayed to allow for a full neurologic evaluation.

4. Arrhythmia: Perhaps secondary to RA dilatation, these patients are at increased risk for the development of supraventricular tachyarrhythmias, most often atrial fibrillation or flutter. Patients with atrial arrhythmias who require a formal Maze procedure may not be considered candidates for minimally invasive procedures, as access to the LA (left atrium) is limited.

Associated conditions

1. Mitral regurgitation: A high percentage of patients with primum ASDs have associated mitral anterior leaflet cleft and regurgitation. The severity of the regurgitation and need for surgical repair should be reviewed prior to commencing and re-evaluated during the pre-bypass transesophageal ecocardiography (TEE) examination.

2. Down syndrome: Primum ASD (and other endocardial cushion defects) and VSDs are associated with Down syndrome.

3. Persistent left superior vena cava: While this variant is present in 0.5% of the general population, it is found in 5% to 10% of patients with other congenital cardiac anomalies.

• Medically unstable conditions warranting further evaluation and optimization include COPD, HTN, DM, CRI, CAD, and recent CVA as in any other surgical procedure. In addition, any evidence of active bacterial infection (dental, urinary tract, cellulitis) should be noted, as the risk of seeding the neoseptum in this setting is significant.

• Delaying surgery may be indicated if (1) the additional preoperative testing changes anesthetic management or (2) pre-operative medical optimization will improve the postoperative course and ultimate outcome.

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

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b. Cardiovascular system

Perioperative evaluation

Comorbid cardiovascular ischemia: Beyond the standard cardiac evaluation for patients undergoing open heart surgery, noninvasive or invasive testing may be indicated for patients having major (unstable ischemia, recent infarction, severe valvular disease, significant arrhythmia) or intermediate (stable angina, remote infarction, previous congestive failure, or diabetes) clinical predictors of myocardial risk. As with most patients presenting for cardiac surgery, these patients should have a full cardiac workup prior to surgery. Patients age 40 years or more or those with major risk factors for CAD (coronary artery disease) should undergo coronary angiography. The presence of significant coronary disease and the need for CABG (coronary artery bypass graft) may preclude minimally invasive ASD/VSD repair.

Ventricular dysfunction: All adult patients with ASD or VSD are at increased risk of ventricular dysfunction. A preoperative echocardiogram to assess right and left ventricular functions and to delineate the anatomy of the septal defect is mandatory.

Pulmonary hypertension: Patients with elevated PA (pulmonary artery) systolic pressure on echocardiography should undergo right heart catheterization. Patients with severe PA hypertension may not be candidates for surgical repair or may require medical intervention (continuous IV epoprostenol) to lower PA pressures prior to surgery.

Comorbid arrhythmia: Patients with persistent SVT should be evaluated for possible Maze procedure or ablation in an EP lab and rate or rhythm controlled medically.

Anesthetic precautions and risk reduction strategies: The use of beta-blockers reduces the risk of perioperative arrhythmias and ischemia in surgical patients with known or suspected coronary artery disease. Patients on these medications chronically should continue to receive them through the perioperative period.

In patients with right ventricular dysfunction and/or pulmonary hypertension, special care should be taken to avoid or limit periods of hypoxemia and hypercarbia that will increase pulmonary vascular resistance. Consider using selective pulmonary vasodilators intraoperatively and in the immediate postoperative period.

Beta-blockers maybe contraindicated in patients with significant RV dysfunction.

c. Pulmonary

Perioperative evaluation

Patient with chronic pulmonary disease should be evaluated to optimize medical and bronchodilator therapies prior to surgery. Although minimally invasive ASD/VSD repair requires one lung ventilation, split lung PFTs are not necessary.

Postoperative analgesia should be discussed with both the surgeon and the patient.

Anesthetic precautions and risk reduction strategies

A perioperative program of intensive chest physiotherapy for patients with COPD should be instituted to help decrease postoperative pulmonary complications (e.g., cough and deep breathing, incentive spirometry).

Smoking cessation should be encouraged: postoperative carboxyhemoglobin concentrations decrease if smoking is stopped for more than 12 hours; pulmonary complications are decreased if smoking is stopped for more than 4 weeks.

The use of epidural analgesia in this patient population is controversial, and while it has been described, we believe the risks outweigh the benefits in this clinical setting (i.e., full heparinization and epidural hematoma, sympathectomy, and perioperative hypotension). Some have advocated the use of single-shot or continuous paravertebral block to minimize these risks while providing dense analgesia.

d. Renal-GI:

Renal dysfunction

Patients with preexisting renal dysfunction are at increased risk for further deterioration after cardiac surgery.

Perioperative evaluation

i. BUN and creatinine

ii. Electrolyte abnormalities

Anesthetic precautions and risk reduction strategies

i. Maintain renal perfusion throughout the perioperative period

ii. Avoid potentially nephrotoxic drugs (NSAIDS, perhaps gentamycin)

iii. Avoid drugs that are dependent on renal elimination (morphine, pancuronium)

iv. Be aware of the possibility of platelet dysfunction in patients with advanced kidney disease

Hepatic dysfunction

Right ventricular dysfunction, which increases central venous pressures, can lead to clinically significant hepatic congestion and hypoperfusion.

Perioperative evaluation

i. Liver function tests, bilirubin

ii. Evidence of decreased synthetic function (abnormal coagulation)

iii. Physical exam

Anesthetic precautions and risk reduction strategies

i. Consider hemofiltration while on bypass in volume overloaded patients to decrease hepatic congestion.

ii. Prepare for bleeding diathesis.

Gastrointestinal

Perioperative evaluation

i. GERD: History or symptoms of esophageal reflux disease

ii. Hiatal hernia: History of disease or dysphagia

iii. Prior esophagectomy or obstructive lesion of the esophagus

Anesthetic precautions and risk reduction strategies

i. For patients with gastroesophageal reflux disease (GERD), consider prophylaxis and induction with cricoid pressure to reduce the risk of aspiration pneumonitis.

ii. In patients with hiatal hernia, gastric imaging with TEE should be minimized when possible to avoid perforation or injury of the esophagus or GE junction.

iii. Prior esophagectomy or obstructive lesions of the esophagus are considered contraindications to TEE and may preclude minimally invasive cardiac surgery.

e. Neurologic

As mentioned above, patients with intracardiac shunt lesions are at risk for cryptogenic stroke secondary to paradoxical emboli. New onset neurologic signs or symptoms should alert the clinician to the possibility of an acute event and should prompt consultation with a neurologist and further investigation prior to proceeding with elective surgery.

f. Endocrine:

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

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

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

• There are no specific medications that are commonly given to this population of patients.

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

• Cardiac: In general, all chronic cardiac medications should be continued throughout the perioperative period. Patients on anti-arrhythmic medications should continue to take them through the perioperative period. In particular, patients on chronic beta blockers should continue their regimens. Some clinicians recommend cessation of ACE inhibitors prior to surgery (as use of these agents through the perioperative period may be associated with vasoplegia).

• Pulmonary: Patients receiving therapy for pulmonary disease, including COPD or asthma, should continue their regimens. Some clinicians advocate administration of bronchodilators prior to induction of general anesthesia to help reduce the risk of bronchospasm during airway instrumentation.

• Renal: Should be continued through the perioperative period.

• Neurologic: Should be continued through the perioperative period.

• Antiplatelet: Risk/benefit of cessation of antiplatelet drugs should be made on a case by case basis. When possible, Plavix should be stopped 7 days prior to surgery to minimize the risk of bleeding and need for transfusion.

• Psychiatric: Should be continued through the perioperative period.

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

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

In addition to standard preparations for patients with a history of latex sensitivity or anaphylaxis, a latex-free pulmonary artery catheter should be used for patients with a history of anaphylaxis. Standard balloon of the pulmonary artery catheter is made of rubber containing latex and should, therefore, be avoided.

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

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

Malignant hyperthermia

• Documented: Avoid all trigger agents such as succinylcholine and inhalational agents:

  Proposed general anesthetic plan: consider a total intravenous technique.

• Family history or risk factors for MH: Consider full MH precautions.

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

Common laboratory normal values will be same for all procedures, with a difference by age and gender.

• Hemoglobin levels: A baseline hemoglobin level should be available.

• Electrolytes: A full panel of electrolytes should be reviewed. Special attention should be paid to BUN and creatinine (rough approximation of renal function) and potassium and glucose (which should be controlled closely, intraoperatively).

• Coagulation panel: A full coagulation panel is indicated in all patients as both a measure of hepatic synthetic function and a predictor of perioperative bleeding risk.

• Imaging: At a minimum, preoperative echocardiographic exams should be reviewed for type and size of the lesion, ventricular and valve functions, and other associated abnormalities. In patients with complex lesions, CT exams and/or cardiac MRI may be helpful in delineating the precise anatomy of the lesion. Coronary angiography should be reviewed for both coronary anatomy and the presence of high-grade stenotic lesions.

• Other tests: Pulmonary function tests may be available but do not necessarily correlate well with risk of intraoperative hypoxia/obstruction. Carotid Doppler may alert clinicians to patients at increased risk of perioperative cerebrovascular events.

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

Patients presenting for minimally invasive ASD/VSD closure require a general anesthetic. (The use of epidural and paravertebral blocks have been described as an adjunct for postoperative pain control.)

When a small right anterior thoracotomy approach is used, the patient is placed in a semisupine position. For robotic procedures, the positioning is similar. When a left parasternal approach is used, supine positioning is typically acceptable.

a. Regional anesthesia

Minimally invasive cardiac procedures do not lend themselves to pure regional techniques for several reasons. The procedures can be lengthy and can require unusual positioning. Intraoperative TEE is obligatory in most cases. In addition, lung isolation and one lung ventilation are necessary for surgical exposure. Nonetheless, the use of neuraxial and paravertebral nerve blocks has been described for postoperative pain management.

• Neuraxial

  Benefits: Epidural catheters theoretically offer excellent postoperative pain control and improved postoperative pulmonary function in patients undergoing minimally invasive cardiac surgery through thoracotomy or mini-thoracotomy incisions. Epidural analgesia may facilitate early extubation after minimally invasive heart surgery.

  Drawbacks: Because of the need for full heparinization, the major concern in this setting is risk of neurologic injury secondary to epidural bleeding and risk of hematoma. Another concern is sympathectomy and the associated hemodynamic effects complicating postoperative management in the intensive care unit.

• Issues: If epidural analgesia is selected, it is important to follow American Society of Regional Anesthesia and Pain Medicine (ASRA) guidelines regarding cessation of anticoagulant and antiplatelet drugs and to confirm normal coagulation profiles prior to insertion and removal of the catheter.

• Peripheral nerve block

  Benefits: Use of both continuous and single-shot paravertebral blocks has been described. Paravertebral blocks offer good analgesia without some of the risks associated with epidural analgesia. Paravertebral blocks may improve postoperative lung function and expedite early extubation.

  Drawbacks: Placement can be time-consuming and requires specific expertise. Risks associated with this approach may be increased in the cardiac surgical population (i.e., hematoma formation).

  Issues: As with epidural placement, it is important to follow ASRA guidelines regarding cessation of anticoagulant and antiplatelet drugs and to confirm normal coagulation profiles prior to insertion and removal of the catheter.

b. General anesthesia

• Benefits: General anesthesia is a requirement for minimally invasive heart surgery and offers many benefits, including patient comfort, ease of positioning, lung isolation, and control of respiration and ability to perform continuous TEE monitoring and examinations.

• Airway concerns: Most minimally invasive techniques require intermittent cessation of respiration on the operative side. This can be accomplished with a double lumen endotracheal tube, a bronchial blocker, a single lumen tube advanced into the contralateral mainstem bronchus, or by intermittently holding respiration.

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

What prophylactic antibiotics should be administered?

As of 2007, beta lactam antibiotics (most commonly cefazolin) are first-line agents for antibiotic prophylaxis for cardiac surgery. Vancomycin should be added for patients with known staphylococcal colonization, patients at high risk for colonization (inpatients for >72 hours), or for all patients at institutions with a high incidence of MRSA (methicillin-resistant
Staphylococcus aureus). Patients with known allergies to cephalosporins or with a history of anaphylactic or IgE-mediated penicillin allergies should receive vancomycin and either gentamycin or levofloxacin. Patients with a history of mild reaction to penicillin (i.e., rash) may receive cephalosporins at the discretion of the anesthesiologist.

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

Communication with the surgical team prior to commencing is critical. When the surgical approach is via a right thoracotomy or mini-thoracotomy the surgeon may request percutaneous SVC drainage cannula, bilateral arterial lines, and lung isolation. For approaches with central cannulation, many of these invasive lines may be unnecessary. It, therefore, follows that the precise surgical approach, planned method of cannulation (peripheral vs central), and planned conduct of bypass should be clear to all participants in the patient’s care. For the remainder of this discussion, we focus on the role of the anesthesiologist in the management of minimally invasive cardiac surgery with planned peripheral cannulation.

What can I do intraoperatively to assist the surgeon and optimize patient care?

The role of the anesthesiologist in minimally invasive ASD/VSD closure is critical to a successful outcome and begins well before incision.

Airway management: Following induction, we usually place an appropriately sized left-sided double lumen endotracheal tube to allow for lung isolation and good exposure during the pre- and post-bypass periods. Double lumen tubes allow toilet of the nonventilated lung, and oxygen insufflation or CPAP if hypoxemia should occur during one-lung ventilation (a not uncommon occurrence after bypass). We choose a left-sided tube because it is relatively simple to place and reliably maintains its position during the procedure. Alternatively, a bronchial blocker may be selected, as it does not require conversion to a single lumen tube should the patient require ventilatory support after surgery.

De-airing of all intravenous access: All intravenous lines must de-aired to prevent any bubbles from crossing from the venous to arterial circulation via an ASD or VSD. Failure to do so increases the risk of paradoxical embolization and postoperative neurologic deficit.

Arterial line placement: Once the airway is secure, placement of invasive lines commences. When an EndoClamp Aortic Cannula is used as an “aortic cross-clamp,” we place bilateral radial arterial lines to help confirm proper location of the balloon and to diagnose distal migration of the balloon and inadvertent occlusion of the innominate artery.

Placement of an introducer and pulmonary artery catheter: An introducer is placed in the right internal jugular vein. TEE can confirm proper wire location (central venous cannulation) in the SVC/RA prior to dilating and placing the large cannula. In many cases, to avoid crossing the ASD or VSD, the pulmonary artery catheter is advanced at the 20-cm mark and locked in this “CVP” position.

Superior vena cava drainage cannula placement: When right atrial isolation is necessary a 14 or 16 French venous drainage cannula is placed percutaneously via the right internal jugular vein (Figure 1). Correct position should be confirmed with TEE.

Figure 1.

Pre-bypass TEE exam: (See Table I). A complete pre-bypass exam should be performed as early as possible. In addition to confirming the presence of the known ASD/VSD and assessment of biventricular and valvular function, special attention should be placed on a complete exam of the septum, as multiple lesions may be present in a single patient. Severe atherosclerotic disease of the aorta may preclude use of retrograde perfusion and should be brought to the immediate attention of the surgeon. Ascending aortic dilatation may preclude use of the EndoClamp cannula and should also be brought to the immediate attention of the surgeon. When the aortic cannula is placed percutaneously with the Seldinger technique via the femoral artery, TEE should be used for wire confirmation in the descending aorta prior to cannula placement. When the EndoClamp cannula is being used, TEE confirmation of the wire in the aortic root and of the cannula in the proximal ascending aorta are necessary as well. During percutaneous Seldinger technique IVC cannula placement, initial proper wire and then cannula position should be demonstrated by TEE as well.