Presentation
This 72-year-old patient presented in 2004 with near syncope and chest discomfort. Coronary angiography revealed significant left anterior descending artery stenosis which was stented. She had acute restenosis with acute myocardial infarction, which prompted repeat intervention 3 days later. Her maximum creatine kinase was 4494 and her troponin was greater than 50. Her course was complicated by atrial fibrillation, which was treated with amiodarone. Left ventricular ejection fraction (LVEF) 1 week later was 25%. Nonsustained ventricular tachycardia was seen. Planning for a prophylactic implantable cardioverter defibrillator (ICD) following her recuperation began, but the patient unfortunately suffered an in-hospital cardiac arrest, which prompted implant of a single chamber ICD.

She was again hospitalized 1 month later with congestive heart failure (CHF) and rapid atrial fibrillation that triggered her ICD. She continued to deteriorate with respect to her congestive heart failure symptoms and eventually became New York Heart Association (NYHA) class IV requiring intermittent outpatient dobutamine therapy. She was hospitalized once again earlier this year. At that time electrocardiogram showed sinus rhythm with a QRS duration of 100 ms. Her congestive heart failure was aggressively treated and she was discharged from the hospital. She was referred for an outpatient evaluation for cardiac resynchronization.

Evaluation and Diagnosis
Cardiac resynchronization therapy (CRT) has been shown to be effective in patients with QRS prolongation. Current guidelines suggest a minimal QRS duration of 130 msec, although the COMPANION study enrolled patients with QRS duration of 120 msec or longer. Unfortunately, not all patients with QRS prolongation benefit from CRT. Moreover, some patients with a narrow QRS are demonstrated to have dyssynchrony on echocardiography despite a narrow QRS complex. In the present case, the patient indeed had a narrow QRS. She was therefore referred for echocardiography in order to evaluate for left ventricular (LV) dyssynchrony. She was noted to have an LVEF of 25%. Tissue Doppler images are seen in Figure 1. These measurements are taken at the anterior, posterior, lateral and septal mitral valve annulus. In this case, the time from the onset of the QRS to the peak of the first positive Doppler deflection (S wave) is measured. This measurement is 179 msec at the septal position (panel A) and 275 msec at the lateral position (panel B) which is consistent with a septolateral delay of 96 ms and presence of significant mechanical dyssynchrony. These measurements may now be automated on newer echo machines.

Patient Management
Based upon these measurements, it was concluded that this patient did indeed have left ventricular mechanical dyssynchrony and would derive benefit from cardiac resynchronization treatment. The patient was referred for upgrade of her existing ICD to a biventricular ICD. In this case, the old ICD was removed. A new atrial pacing lead was implanted and a new coronary sinus lead was placed in the mid lateral branch of her coronary sinus. She was discharged later that same day in stable condition.

Outcome
The patient tolerated the procedure well and was next seen in the office 2 weeks later for a postsurgical wound check. At that time she reported a marked improvement in her symptoms. A chest radiograph is shown in Figure 2. This shows appropriate positions of the ICD lead in the right ventricle (RV), the atrial lead in the right atrium (A) and the tranvenous LV lead in the mid-lateral epicardial vein (LV). She has remained on her pre-operative medical regimen including carvedilol, furosemide, lisinopril, and amiodarone. At her last visit she had NYHA class II symptoms of CHF. She has not been readmitted to the hospital in the 6 months since her upgrade.

Discussion
Cardiac resynchronization is a proven therapy for patients with class III and IV congestive heart failure in the setting of severe LV systolic dysfunction and widened QRS duration. Several echocardiographic markers for LV dyssynchrony have been recognized. Patients with LV dyssynchrony and a narrow QRS may benefit from biventricular pacing as well. Randomized trials are currently underway to evaluate this new indication. Patients with narrow QRS and heart failure comprise 2/3rd of all patients with heart failure. Physicians should evaluate such patients for presence of mechanical dyssynchrony, the presence of which should prompt treatment with cardiac resynchronization.