Abstract 14752: A Blunted Heart Rate Response During Dobutamine Stress Echocardiography is Associated with Impaired Myocardial Contractile Reserve in Dilated Cardiomyopathy

Abstract

Background. Heart failure patients may have desensitization of myocardial β-adrenergic responsiveness. Pressure-volume relationship (PVR) is a robust method to evaluate intrinsic myocardial contractility during dobutamine stress echocardiography (DSE). In this study we sought to assess the relationship between heart rate change (ΔHR) and the presence of myocardial contractile reserve during DSE in patients with dilated cardiomyopathy.

Methods. The study sample was formed by 132 patients with dilated cardiomyopathy (age 68±9 years; ejection fraction 30±7%; ischemic etiology 59%) having high-dose DSE (up to 40 mcg/Kg/min) negative for inducible ischemia. PVR was defined as systolic cuff pressure/end-systolic volume index difference between rest and peak DSE. All patients were on optimal and maximally tolerated β-blockers therapy.

Results. Resting HR was comparable in patients with and without contractile reserve (66±12 vs 69±12 bpm; p=NS). However, HR at peak stress (109±19 vs 98±19 bpm; p=0.004) and ΔHR (+71±35% vs +41±30%; p<0.001) (Figure) were significantly higher in the former. Using C statistics, a ΔHR of +57% was the best cut-off for predicting myocardial contractile reserve (sensitivity 60%, speci[[Unable to Display Character: fi]]city 77%). Patients with higher ΔHR showed lower LV end-diastolic (146±44 vs 176±77 ml; p=0.01) and end-systolic volume (102±38 vs 129±65 ml; p=0.01), higher resting (31±7 vs 27±7% p=0.01) and peak-stress LV ejection fraction (52±14 vs 38±12% p<.001), and lower E/e’ (12±7 vs 15±5; p=0.02).

Conclusion. In patients with dilated cardiomyopahty a blunted heart rate change during DSE is associated with impaired contractile reserve as well as echocardiographic indicators of more advanced disease.