History
A 65-year-old man, affected by permanent atrial fibrillation for more than 10 years experienced worsening mitral valve regurgitation and maladaptive left ventricle remodeling. These conditions led to hypokinetic dilated cardiomyopathy with severe reduction of left ventricular systolic function and repeated hospitalizations for acute heart failure (American College of Cardiology [ACC] and American Heart Association [AHA] stage C heart failure).
The patient was initially treated with drugs for heart failure, associated with a rate control strategy for atrial fibrillation with a combination of beta blockers and digoxin (carvedilol 6.25 mg twice daily; no further titration was possible because of low ventricular rate at rest and low blood pressure). A baseline electrocardiogram (ECG) showed atrial fibrillation with incomplete left bundle branch block (LBBB) and mean heart rate of 78 bpm.
He was subsequently evaluated for surgical treatment of mitral valve incompetence, which was graded as severe (angiographic grade 4+/4+, vena contracta of 0.76 cm, and regurgitant orifice area of 0.44 cm2). The surgeon did not think surgery was the appropriate first-step therapy in this patient, with an unacceptable level of risk because of severe left ventricular dysfunction and dilation (end-diastolic diameter 70 mm, end-diastolic volume 240 mL, ejection fraction 27%).
Coronary angiography documented the absence of significant coronary stenoses.
Considering left ventricular dysfunction, LBBB, and the persistence of heart failure symptoms, notwithstanding optimized medical therapy (New York Heart Association [NYHA] class III), cardiac resynchronization therapy (CRT) was initiated. On November 2008 a biventricular CRT defibrillator (CRT-D) was implanted and beta blocker dosages were increased.
Six months after discharge the patient reported substantial improvement of symptoms (NYHA II), but experienced two inappropriate implantable cardioverter-defibrillator (ICD) shocks because of a high ventricular rate during atrial fibrillation. ICD control documented suboptimal biventricular pacing percentage during atrial fibrillation (<85%, including fusion and pseudofusion beats). Echocardiography documented a favorable remodeling of the left ventricle (LVEF 27% to 38%, end-diastolic diameter 70 to 64 mm, end-diastolic volume 240 to >200 mL, and severe to mild-moderate mitral regurgitation).
The patient underwent atrioventricular node ablation in March 2009.1,2 Six months after atrioventricular node ablation (and 1 year after CRT implantation) complete left ventricular reverse remodeling was observed (i.e., LV end diastolic volume 140 mL, LVEF 60%, mild mitral regurgitation); the patient became completely asymptomatic.
However, during subsequent follow-up, the patient showed an extremely difficult control of the international normalized ratio (INR) therapeutic range, with frequent evidence of values above and below the therapeutic range, and had two episodes of corneal hemorrhage. For these reasons, he underwent left atrial appendage occlusion in November 2010.
In March 2011 optimal left atrial appendage occluder positioning was confirmed by cardiac computed tomography and transesophageal echocardiography and oral anticoagulation was safely discontinued.
Comments
Before CRT, titration of beta-blocker therapy was not possible because of a low ventricular rate at rest and low blood pressure. After CRT-D implantation, beta-blocker therapy was optimized, but it was insufficient to warrant complete biventricular pacing (<85%), and two inappropriate ICD shocks on fast atrial fibrillation were observed. Clinical and instrumental benefit was consistent but incomplete.
FIGURE 28-1
After successful atrioventricular nodal ablation, 100% effective biventricular pacing was acheived3 and extremely favorable left ventricular remodeling was then obtained (normal diameters, normal LVEF, and mild mitral valve regurgitation). The patient became asymptomatic.
Current Medications
The patient was taking carvedilol 25 mg twice daily, ramipril 5 mg twice daily, furosemide 12.5 mg daily, spironolactone 25 mg daily, warfarin to maintain INR of 2-3 but subsequently discontinued, and aspirin.
Comments
Optimized medical therapy for heart failure was not discontinued even after complete reverse remodeling of the left ventricle. Oral anticoagulant therapy with warfarin was managed with difficulty by the patient and provoked complications such as corneal hemorrhage. The patient then underwent successful left atrial appendage occlusion.
Current Symptoms
The patient was substantially asymptomatic, with dyspnea only with strenuous exertion (NYHA I).
Physical Examination
Comments
After extremely favorable reverse remodeling, the patient was asymptomatic with good tolerance to physical activity and dyspnea only after strenuous exertion.
Laboratory Data
Electrocardiogram
Findings
The electrocardiogram showed atrial fibrillation, heart rate of 75 bpm, and incomplete LBBB (Figure 28-1). Figure 28-2 shows atrial fibrillation, biventricular pacing, fusion, and pseudofusion beats, and Figure 28-3 shows atrial fibrillation, biventricular pacing, and heart rate of 70 bpm.
Comments
After CRT-D implantation and before atrioventricular node ablation, biventricular pacing was suboptimal (see Figure 28-2). ICD counters always overestimate pacing percentage because of fusion and pseudofusion beats.
FIGURE 28-2
FIGURE 28-3
Chest Radiograph
Comments
The chest radiograph before CRT shows an enlarged cardiac silhouette (Figure 28-4). After CRT and left ventricular reverse remodeling (Figure 28-5), the radiographic cardiac silhouette appears normal and was confirmed to be normal at 2 and 3 years from implantation.
Echocardiogram
Comments
Figures 28-6 and 28-7 show the reduction of mitral regurgitation severity after reverse remodeling obtained with combined therapy (medical, CRT, and atrioventricular node ablation).
FIGURE 28-4
FIGURE 28-5
FIGURE 28-6
FIGURE 28-7
Physiologic Tracings
Findings
The ICD counter highlighted the achievement of near complete biventricular pacing after atrioventricular node ablation, in contrast to unacceptable pacing percentage on medical therapy alone (Figure 28-8).
Computed Tomography
Comments
Postoperative computed tomography revealed optimal left atrial appendage occluder positioning and a complete left atrial appendage (Figure 28-9).
Catheterization
Findings
Coronary angiography documented the absence of stenotic lesions, excluding a potential ischemic component of the left ventricular dysfunction. Prolonged projections for coronary sinus anatomy visualization were obtained in preparation for left ventricular lead implantation for resynchronization therapy (Figures 28-10 and 28-11).
Comments
Focused Clinical Questions and Discussion Points
Question
How can a patient with permanent atrial fibrillation and severe reduction of left ventricular systolic function associated with severe mitral regurgitation best be treated? Can surgery be considered an effective and safe option?
Discussion
In the presence of severe mitral regurgitation, LVEF usually is overestimated; the actual left ventricular systolic function could be much lower than that measured by echocardiography. In this setting, surgery may be associated with a very high operative risk and the postoperative rise in left ventricular afterload could determine much more severe left ventricular dysfunction.
Question
FIGURE 28-8
FIGURE 28-9
FIGURE 28-10
FIGURE 28-11
Discussion
Current guidelines for CRT do not provide a class I recommendation for CRT in patients with heart failure who are in atrial fibrillation, even though evidence exists of benefits similar to those in patients in sinus rhythm,3,4 particularly if atrioventricular node ablation is performed. In a patient with atrial fibrillation and mitral regurgitation that can be ascribed to left ventricular dyssynchrony resulting from LBBB and adverse left ventricular remodeling, causing a tenting of valve leaflets, CRT is a treatment option that appears to focus on the origin of the problem. Reversal of dyssynchrony and left ventricular reverse remodeling can be associated with a significant reduction of mitral regurgitation.
Question
Is atrioventricular node ablation necessary to maximize CRT benefit in patients with atrial fibrillation and heart failure?
Discussion
The evidence of the need for maximization of biventricular pacing percentage to optimize CRT outcome is now confirmed by several studies5,6 and two meta-analyses.7 Drug therapy alone is rarely able to cause a dromotropic effect on the atrioventricular node sufficient to permit complete or near complete biventricular pacing, especially during effort. Biventricular pacing percentages derived from ICD counters are always overestimated because of fusion and pseudofusion beats.
Atrioventricular node ablation is the only procedure able to block atrioventricular node conduction in every condition and allow complete biventricular pacing.
Final Diagnosis
The patient was diagnosed with ACC and AHA stage B heart failure. He had normal systolic function and normal left ventricle diameters and volumes.
Plan of Action
The patient was to undergo clinical evaluation, echocardiogram, and ICD interrogation every 6 months. He was provided devices for remote transtelephonic transmission of domestic ICD interrogation.
Intervention
The patient underwent left atrial appendage occluder implantation, warfarin discontinuation, introduction of aspirin and clopidogrel, and subsequent clopidogrel discontinuation. Indetermined ASA assumption.
Outcome
The patient experienced maintenance of left ventricular function remodeling through CRT and heart failure medications.
Selected References
1. Gasparini M., Auricchio A., Regoli F. et al. Four-year efficacy of cardiac resynchronization therapy on exercise tolerance and disease progression: the importance of performing atrioventricular junction ablation in patients with atrial fibrillation. J Am Coll Cardiol. 2006;48:734–743.
2. Gasparini M., Auricchio A., Metra M. et al. Long-term survival in patients undergoing cardiac resynchronization therapy: the importance of performing atrio-ventricular junction ablation in patients with permanent atrial fibrillation. Eur Heart J. 2008;29:1644–1652.
3. Kaszala K., Ellenbogen K.A. Role of cardiac resynchronization therapy and atrioventricular junction ablation in patients with permanent atrial fibrillation. Eur Heart J. 2011;32:2344–2346.
4. Brignole M., Botto G., Mont L. et al. Cardiac resynchronization therapy in patients undergoing atrioventricular junction ablation for permanent atrial fibrillation: a randomized trial. Eur Heart J. 2011;32:2420–2429.
5. Koplan B.A., Kaplan A.J., Weiner S. et al. Heart failure decompensation and all-cause mortality in relation to percent biventricular pacing in patients with heart failure: is a goal of 100% biventricular pacing necessary? J Am Coll Cardiol. 2009;53:355–360.
6. Hayes D.L., Boehmer J.P., Day J.D. et al. Cardiac resynchronization therapy and the relationship of percent biventricular pacing to symptoms and survival. Heart Rhythm. 2011;8:1469–1475.
7. Ganesan A.N., Brooks A.G., Roberts-Thomson K.C. et al. Role of AV nodal ablation in cardiac resynchronization in patients with coexistent atrial fibrillation and heart failure: a systematic review. J Am Coll Cardiol. 2012;59:719–726.
