Use of left ventricular pacing in heart failure: Evaluation by gated blood pool imaging

Background Left ventricular (LV) pacing has been suggested to complement other forms of therapy in patients with heart failure. Methods and Results. We investigated 17 patients (15 men, 2 women, aged 68 +/- 6 years, 10 ischemic and 7 primary dilated cardiomyopathy) with heart failure (13 were in New York Heart Association class IV and 4 in class III). One month after LV pacer implantation, 12 patients reported clinical improvement (mean class 3.7 before pacing vs 2.6 with LV pacing; P = .001). We report the results of 3 equilibrium-gated blood pool studies performed in each patient, 1 before pacing and 2 after pacer implantation (1 with pacing on, and 1 after turning off the pacer). LV pacing did not modify LV ejection fraction. Phase analysis demonstrated a significant decrease of the interventricular phase shift (Delta pi) with LV pacing (no pacing, Delta pi = 8.99 degrees +/- 19.05 degrees; Delta pi = -0.97 degrees +/- 27.85 degrees with LV pacing). Clinical improvement was observed in patients with an initial positive Delta pi that decreased with pacing and/or an initial LV phase standard deviation >50 degrees that decreased with pacing. Conclusion. LV pacing induces interventricular and intraventricular synchronization. A decrease of the interventricular phase shift seems to be the most important predictor of functional recovery for paced patients with heart failure.