The importance of contractile reserve in patients with resynchronization therapy

INTRODUCTION: Contractile reserve of the myocardium is a strong prognostic factor in patients with heart failure. The presence of a significant amount of myocardial fibrosis might lead to insufficient response to resynchronization therapy We assumed that pre-implantation examination of global contractile reserve will allow prediction of the response to resynchronization treatment. METHODS: 25 symptomatic patients (NYHA III) with severe systolic dysfunction [ejection fraction (EF) 28.9 ± 6.9%] with signs of electric asynchrony (QRS 120 ms) went through dobutamine echocardiography prior to resynchronization treatment. The global contractile reserve was determined from the change to EF at rest and at the peak of pharmacological burden (40 μg/kg/min). Patients with a rise in EF of more than 5% and/or endsystolic volume reduction of more than 15% after three months of resynchronization treatment were considered responders. RESULTS: Compared to non-responders, responders had higher increase in EF during dobutamine stress echocardiography (Δ 12.8 ± 7.4 % vs. Δ 3.4 ± 7.1 %, p = 0.0042). Three months from the initiation of resynchronization therapy, the global myocardial contractile reserve also significantly correlated with EF increase (r = 0.67, p = 0.007). The 6% increase in EF during dobutamin stress echocardiography predicted responders to resynchronization therapy with 83% sensitivity and 75% specificity. CONCLUSION: The global contractile reserve may play an important role in prediction of a response to resynchronization therapy.