Background: Cardiac resynchronization fails to improve symptoms in up to one third of patients meeting criteria for this treatment, for reasons which are unclear. Indeed, the very mechanism of benefit from resynchronization is controversial. Resynchronization may work by improving ventricular filling: we tested the hypothesis that benefit from resynchronization depends on filling pattern.
Methods and results: We assessed symptoms (NYHA class) and LV filling of 40 patients with chronic heart failure and prolonged QRS who underwent resynchronization. Fifteen had restrictive filling pattern (E velocity>or=1.0 m/s, E/A ratio>1 and E wave deceleration time<or=140 ms) and 25 had late filling pattern (single isolated A wave or summation wave filling in late diastole). At 6 months, the patients with restrictive filling failed to show the improvements observed in those with late filling. They failed to reduce NYHA class (DeltaNYHA: 27% improved one class, 66% unchanged, 7% worsened one class, P=NS; vs. 8% improved two classes, 72% improved one class and 20% unchanged, P<0.001; difference between groups, P<0.001). They failed to reduce LV end-diastolic dimension (DeltaLVEDD -0.04 cm, P=NS; vs. -0.6, P<0.001; difference between groups, P<0.05) or end-systolic dimension (DeltaLVESD -0.01 cm, P=NS; vs. -0.6, P<0.001; difference between groups, P<0.05). They failed to improve cardiac cycle efficiency (Deltatotal isovolumic [wasted] time 2.1 s/min, P=NS; vs. -5.4 s/min; difference between groups, P<0.001).
Conclusion: Among patients routinely eligible for resynchronization, those with restrictive filling may show significantly less (and possibly no) improvement in symptom class and ventricular dimensions after resynchronization. Their failure to improve cardiac cycle efficiency may account for their attenuated clinical benefit.