Nontransplantation Surgical Treatment for Chronic Heart Failure
Clay A. Cauthen
Gonzalo Gonzalez-Stawinski
Mazen Hanna
I. INTRODUCTION.
Even with optimal medical therapy, the morbidity and mortality associated with chronic heart failure (CHF) is significant. Fortunately, there are multiple possible surgical interventions available for these patients that may help to avoid or postpone the need for advanced salvage therapies and transplantation. Despite the improvement in surgical techniques and an enhanced understanding of the role of reconstructing structural abnormalities of the failing heart, safety and efficacy data are still limited for many of these procedures. Elective and planned procedures for advanced heart failure (e.g., revascularization, valvular surgery, left ventricular [LV] reconstructive surgery, and cardiomyoplasty) and urgent or bridging procedures (e.g., circulatory support devices and total artificial heart [TAH]) are discussed in this chapter. Surgical approaches to the management of heart failure must be accompanied by continued aggressive pharmacologic therapy.
II. SURGICAL REVASCULARIZATION FOR ISCHEMIC CARDIOMYOPATHY
A. Pathophysiology
1. Loss of coronary flow reserve in severe coronary artery disease leads to reduction in myocardial perfusion, tissue hypoxia, and myocardial dysfunction.
2. Myocardial infarction results in necrosis, scarring, and loss of contractile function. Sites distal to infarction undergo increased mechanical stress and adverse remodeling over time. Progressive ventricular dilation and impairment of systolic and diastolic function occur.
3. Chronic ischemia can decrease perfusion, leading to hibernation, repeated episodes of stunning, and recurrent infarction. The cardiomyocytes may shift metabolic states to hibernation. Thus, revascularization may help retain viability and recover function. Stunning and hibernation may be detected by various imaging modalities (see Chapter 50).
a. Stunning is the loss of contractile function caused by a momentary total occlusion of blood flow with subsequent restoration of flow.
b. Hibernation is the downregulation of myocardial function to match the chronic reduced blood flow. Hibernating cardiomyocytes manifest sustained glucose extraction, decreased glycogen content, and decreased contractile proteins and function.
B. Clinical significance
1. Heart failure, rather than angina or an acute coronary syndrome, is a common presentation of myocardial ischemia in patients with underlying cardiac dysfunction.
2. At least two-thirds of patients with cardiac dysfunction have evidence of epicardial coronary artery disease as the primary etiology. Coronary angiography is indicated when the suspicion of an ischemic cause for cardiomyopathy is high.
3. Some patients may have epicardial coronary artery disease superimposed on an underlying dilated cardiomyopathy. In this scenario, the presence of epicardial coronary artery disease may not necessarily explain the “degree” of depressed myocardial contractility. The role of revascularization remains unclear for these patients.
C. Recommendations
1. Most recently, the Surgical Treatment for Ischemic Heart Failure (STICH) trial reported that in patients with coronary artery disease amenable to coronary artery bypass grafting (CABG) and left ventricular ejection fraction (LVEF) < 35%, there was no difference in the trial’s primary end point of all-cause mortality when treated with optimal medical therapy versus CABG. However, benefit was seen in the CABG group with respect to the secondary end point of cardiovascular death at follow-up. There were several limitations to this study: 30-day mortality was high in the CABG group and significant crossover occurred, both of which may have diminished the benefits of CABG in the primary intention to treat analysis.
2. Primary CABG should still be considered for patients with an LVEF > 15%, LV end-diastolic dimensions < 65 mm, distal vessels suitable for grafting, and evidence of a significant amount of ischemic or hibernating myocardium. These guidelines are arbitrary and many centers consider patients with more severe diseases.
3. Patients with hibernating myocardium and severe LV dysfunction who undergo CABG may achieve survival advantage comparable to those receiving cardiac transplantation (about 80% survival in 3 years).
a. The potential for significant improvement in LV function and symptoms is assumed to be great enough to recommend revascularization when there are four or more viable segments of myocardium, representing approximately 31% of the left ventricle.
b. Surgical revascularization of the patient with severe heart failure should generally be considered as part of a multifaceted approach, including evalu ation for valve repair, ventricular reconstructive surgery, cryoablation for ventricular arrhythmias, and maze procedure or pulmonary vein isolation procedures for atrial dysrhythmias. To maximize the therapeutic benefit from this approach, aggressive complementary pharmacologic approaches are indicated postoperatively.
III. MITRAL VALVE SURGERY
A. Pathophysiology
1. As the ventricle fails, progressive dilation leads to abnormal geometry of the left ventricle, giving rise to mitral regurgitation (MR). MR results in progressive increase in volume overload of the left ventricle, progressive LV dilation, and further worsening of MR.
2. Other alterations of the annular—ventricular apparatus and ventricular geometry contribute to the pathogenesis of MR: papillary muscle ischemia or infarction, myocardial thinning and dilation, blunting of the aortomitral angle, widening of the interpapillary distance, and increased leaflet tethering leading to loss of the zone of coaptation.
B. Clinical significance and recommendations
1. Restoration of zone of coaptation by inserting an “undersized” annuloplasty ring may correct the MR and improve the LV geometry and cardiac output. However, mitral valve repair in ischemic cardiomyopathy (“ischemic MR”) is less successful than in degenerative MR.
2. Subvalvular apparatus should be kept intact when possible.
3. In some patients, mitral valve surgery results in improved symptoms and measures of LV function and remodeling but not necessarily in improved survival.
4. In some patients, mitral valve repair with a figure-of-eight stitch (i.e., Alfieri approach) or the “edge-to-edge” technique may be used in addition to annuloplasty to secure the repair.
5. Mitral valve replacement is required in a minority of patients and may be associated with a significantly worse outcome.
IV. LV RECONSTRUCTIVE PROCEDURES
A. Pathophysiology
1. Laplace’s law dictates that as the failing heart dilates, the intracavity radius increases and thus wall stress increases. The result is increased myocardial oxygen consumption and stimulation of adverse remodeling.
2. Surgical remodeling helps to decrease ventricular size and wall stress. Endoventricular circular patch plasty (EVCPP, also called the Dor procedure) is performed in patients with ischemic cardiomyopathy and significant areas of LV akinesis or dyskinesis. Partial LV resection, also called the Batista procedure, was performed in the past on patients with dilated, nonischemic cardiomyopathy. This was abandoned because of poor intermediate results and increased mortality, despite promising short-term outcomes.
B. Endoventricular circular patch plasty
1. Acute myocardial infarction leads to tissue necrosis, scar formation, followed by LV remodeling, leading to dilation and heart failure. The Dor procedure is suit able for patients with a left anterior descending artery territory scar or aneurysm with relatively preserved lateral and posterior LV wall function.
a. It involves opening of the akinetic or dyskinetic scar and placement of a purse-string suture at the neck of the aneurysm. The residual opening may be closed with a Dacron patch, after which the ventriculotomy is closed by running sutures.
b. This procedure is accompanied by CABG in >90% of cases. Additional valve and ablative surgical procedures are commonly performed.
2. Good candidates for EVCPP include patients with LV aneurysm (or large akinetic area), an increased LV end-systolic index, absence of scar in the circumflex territory, as well as good target tissue and viability for concomitant CABG. Assessment of the severity of MR is needed at the time of surgery, and mitral valve repair is performed in 30% to 50% of patients undergoing EVCPP.
3. EVCPP results in improved LVEF, end-diastolic and end-systolic volume indices for LV volumes, and improvement in New York Heart Association (NYHA) functional class.
a. In a series of patients with advanced heart failure, the event-free survival rate was 98% at 1 year, 95.8% at 2 years, and 82.1% at 5 years.
b. Independent predictors of mortality include higher preoperative NYHA class, lower LVEF (< 30%), higher end-systolic volume index, and remote asynergy.
c. Interestingly, the STICH trial demonstrated that despite the reduced LV volume, there was no difference in symptoms, exercise tolerance, hospitaliza tion, and death in patients who received CABG with surgical ventricular reconstruction versus CABG alone. On the basis of this trial, surgical ven tricular reconstruction may not add any benefit to HF patients with docu mented ischemia who are on optimal medical management.
C. Partial LV resection (i.e., Batista procedure) involves the resection of myocardium at the posterolateral wall between the anterolateral and the posteromedial papillary
muscles in nonischemic cardiomyopathy, with or without mitral annuloplasty or mitral valve replacement. For the reasons previously stated, this procedure is no longer performed.
muscles in nonischemic cardiomyopathy, with or without mitral annuloplasty or mitral valve replacement. For the reasons previously stated, this procedure is no longer performed.
D. Dynamic cardiomyoplasty
1. The procedure involves the mobilization of the entire latissimus dorsi muscle to be used as a pedicle graft. The muscle is passed into the thoracic cavity through a window created by removing the left second rib. The muscle is wrapped around the heart and anchored posteriorly, adjacent to the right atrium and pulmonary artery, and anteriorly around the right ventricle.
a. Sensing electrodes are placed epicardially on the right ventricle, and intra muscular stimulator electrodes are placed in the latissimus muscle.
b. The muscle conditioning process takes place 2 weeks after surgery and involves the delivery of a single pulse with every other cardiac cycle for 2 weeks. The signal is then incrementally increased every 1 to 2 weeks for 12 weeks.
2. Cardiomyoplasty is believed to work by systolic augmentation of the failing left ventricle and the girdling effect of the muscle acting as an elastic constraint. This prevents LV dilation and improves symptoms, but has no proven survival advantages. Indeed, early mortality is high, especially in those with NYHA class IV status. This procedure is rarely performed now, and data are lacking on its long-term efficacy.
3. Approximately 80% to 85% of surviving patients show NYHA class improvement (mean 1.4 classes). A phase II multicenter FDA study demonstrated significant improvement in LVEF, LV stroke work, and stroke index.
4. Mortality of surgery for class III patients has been < 10%.
5. Hypertrophic obstructive cardiomyopathy is considered to be a relative contraindication.
V. CIRCULATORY SUPPORT DEVICES (I.E., MECHANICAL ASSIST DEVICES)
A. Background
1. Mechanical circulatory assistance is necessary for patients with hemodynamic compromise that are unlikely to survive without a transplant or advanced salvage therapies. Mechanical circulatory support devices may help bridge the patients to recovery or transplantation.
2. The types of devices include the following: intra-aortic balloon counterpulsation pump (IABP), extracorporeal membrane oxygenation (ECMO), univentricular and biventricular nonpulsatile and pulsatile ventricular assist devices (VADs), and the TAH.
3. The decision about which device to use is based on the predicted duration of use, the reversibility of the underlying condition that caused cardiogenic shock, need for single-chamber versus dual-chamber support, and the patient’s size.
B. Patient selection
1. Mechanical support is generally indicated in patients who have an inability to maintain hemodynamic stability despite maximal pharmacologic support and who usually must meet criteria as candidates for cardiac transplantation:
a. Systolic blood pressure < 75 to 80 mm Hg
b. Cardiac index of <1.5 to 1.8 L/min/m2
c. Pulmonary venous saturation < 50%
2. Indications for short-term circulatory support devices include the following:
a. Cardiogenic shock after cardiac surgery
b. Acute myocardial infarction with cardiogenic shock
c. Acute (fulminant) myocarditis
d. Cardiac arrest as a complication of interventional cardiac procedures (associ ated with high mortality and poor survival rates)
3. The 2006 International Society for Heart and Lung Transplantation (ISHLT) guidelines for cardiac transplant candidates:
a. The most recent ISHLT recommendations give a class I recommendation to thoroughly evaluate other clinical risk factors prior to device implanta tion. For instance, an inverse relationship between outcome and age > 60 to 65 years has been reported. However, age by itself should not be a contrain dication to implantation.
b. Patients with serum creatinine > 3.0 mg/dL are at higher risk but may be considered candidates for implantation if renal failure is acute and recovery is likely (class I).
c. Pulsatile intracorporeal devices should only be implanted in patients with body surface area (BSA) > 1.5 m2.
d. In patients with abnormal liver function tests secondary to right ventricular (RV) failure, biventricular support should be considered. In addition, biven tricular support should be considered in those with irreversible pulmonary hypertension, RV failure, or multiorgan dysfunction.
e. Active infection should be identified and treated before implantation.
4. If recovery is anticipated, the best option is to use the least traumatic, least com plicated device for the individual patient. If recovery of ventricular function is not expected, patients should be considered for the use of a long-term implant able device.
C. Short-term devices
1. Intra-aortic balloon counterpulsation pump
a. IABP should be placed percutaneously under fluoroscopy so that the tip is about 2 cm below the left subclavian. Height of the patient will determine the size of the IABP (40 cc balloon for the average-sized male). Swan-Ganz catheter and arterial line are encouraged and typically required for hemody namic monitoring.
