History
The patient was a nonsmoker. He had experienced a myocardial infarction in 2003. A coronary angiogram performed in 2003 showed severe left main artery disease and triple vessel disease. He underwent coronary artery bypass grafting (CABG) the same year. Echocardiography was done 6 months after CABG showed left ventricular ejection fraction (LVEF) of 25%. He was diagnosed with New York Heart Association (NYHA) class III disease, and electrocardiography showed sinus rhythm with a left bundle branch block pattern. QRS duration was 150 msec, and no history of ventricular arrhythmia was reported. In view of persistent left ventricular systolic dysfunction and underlying wide QRS duration, cardiac resynchronization therapy with defibrillator (CRT-D) backup was performed. The procedure was uneventful, and the left ventricular lead was inserted in the posterolateral branch of the coronary sinus. He was subsequently followed regularly by the combined heart failure and device clinic.
The patient returned 6 months after CRT-D implantation and was found to be clinically still in NYHA class III. Device interrogation showed that he received 85% biventricular pacing. Other parameters were unremarkable. Follow-up echocardiographic examination showed an LVEF of 25%.
Comments
The patient was both clinically and echocardiographically a CRT nonresponder. It was necessary to explore the potential cause of lack of CRT response.
Current Medications
The patient’s medications are aspirin 80 mg daily, metoprolol controlled-release 12.5 mg daily, ramipril 1.25 mg daily, furosemide 20 mg daily, and simvastatin 20 mg daily.
Comments
The patient received most of the guideline-recommended medications. However, the dosage was not optimal.
Current Symptoms
The patient experienced persistent heart failure symptoms after CRT-D implantation.
Comments
The cause of the patient’s nonresponse to CRT needs to be identified. It is likely due to suboptimal biventricular pacing and suboptimal medical therapy.
Physical Examination
Comments
The patient was clinically in NYHA class III heart failure.
Laboratory Data
Electrocardiogram
Findings
The electrocardiogram revealed sinus rhythm with inadequate biventricular pacing (Figure 6-1) and adequate biventricular pacing after medical therapy (Figure 6-2).
Comments
It is necessary to confirm this is biventricular capturing.
Chest Radiograph
Findings
The chest radiograph revealed cardiomegaly with no evidence of congestion. All leads were in situ.
Echocardiogram
Findings
The echocardiogram in apical four chamber view revealed dyschronous contraction resulting from lack of biventricular pacing (Figure 6-3).
FIGURE 6-1
FIGURE 6-2
Findings
The apical four chamber view showed improved LVEF and significantly less left ventricular cavity dilation after optimal medical therapy (Figure 6-4).
Focused Clinical Questions and Discussion Points
Question
What are the potential causes of CRT nonresponder in this patient?
Discussion
Two obvious factors contributed to the patient’s illness—inadequate biventricular pacing and suboptimal medical therapy with an inadequate dosage of medication.
Question
What should be done to maximize CRT response?
Discussion
The dosage of metoprolol (Betaloc), a beta blocker, should be increased for two reasons. First we should try to titrate up the dosage of medication to guideline-recommended dosage and the current prescribed dose was too low. Second, the increase of beta blocker can slow intrinsic heart rate while increasing the percentage of biventricular pacing. Higher percentage of biventricular pacing has been shown to correspond to increased CRT treatment efficacy.
Question
Is any other medical therapy appropriate to be added for this patient?
Final Diagnosis
The patient’s final diagnosis is suboptimal medical therapy leading to CRT nonresponse.
Plan of Action
The plan of action in this patient was escalation of medical therapy.
Intervention
The dosages of the beta blocker and ramipril were increased, and digoxin and aldactone were added.
Outcome
Further device interrogation showed that biventricular pacing percentage approached 100%, and the latest echocardiography showed the LVEF to be approximately 40%. Clinically the patient was in NYHA class II.
Findings
This case illustrates the importance of optimal medical therapy in patients with CRT. Current device guidelines suggest it is mandatory to give optimal medical therapy before CRT implantation.1 Also, study has led to the suggestion that patients receiving CRT without optimal medical therapy were associated with less echocardiographic and clinical improvement.3
Selected References
1. Digitalis Investigation Group. The effect of digoxin on mortality and morbidity in patients with heart failure. N Engl J Med. 1997;336:525–533.
2. Epstein A.E., DiMarco J.P. et al. American College of Cardiology/American Heart Association task force on practice guidelines (Writing committee to revise the ACC/AHA/NASPE 2002 guideline update for implantation of cardiac pacemakers and antiarrhythmia devices); American association for thoracic surgery; Society of thoracic surgeons. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities. J Am Coll Cardiol. 2008;51:e1–e62.
3. Fung J.W., Chan J.Y., Kum L.C. et al. Suboptimal medical therapy in patients with systolic heart failure is associated with less improvement by cardiac resynchronization therapy. Int J Cardiol. 2007;115:214–219.
4. Pitt B., Remme W., Zannad F. et al. Eplerenone, a selective aldosterone blocker, in patients with left ventricular dysfunction after myocardial infarction. Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study Investigators. N Engl J Med. 2003;348:1309–1321.
