Heart rate reserve during dipyridamole stress test applied to potential heart donors in brain death.

BACKGROUND: A blunted heart rate reserve (HRR) during dipyridamole stress echocardiography (DSE) is a prognostically unfavorable sign of cardiac autonomic dysfunction. Short-term adjustments of heart rate (HR) are thought to rise from changes in neural input to the heart. DSE is applied in potential heart donors to rule out underlying coronary artery disease and left ventricular dysfunction. AIM: to assess HRR during DSE in brain death. METHODS: We enrolled 2 Groups: Group 1 (n=49, 22 men, 54.6+/-8.8 years) with patients in brain death enrolled in the nationwide marginal donor heart recruiting program; Group 2 (n=49, 18 men, 66.4+/-12.0 years) referred to DSE for suspected or known coronary artery disease. All underwent DSE (0.84 mg/kg in 6') by quality-controlled readers certified via web-based training (1487/CE Lazio-1). We assessed left ventricular contractile reserve (LVCR) as stress/rest ratio of force (systolic blood pressure /end-systolic volume). HRR was calculated as the peak/rest HR ratio from 12-lead EKG. RESULTS: The 2 groups were similar for prevalence of inducible ischemia (4/49 vs 9/49, p=ns). Group 1 showed higher resting HR (Group 1= 88.1+/-15.5 vs Group 2= 66.5+/-11.5 bpm, p<0.01) and similar peak HR (Group 1=94.7+/-15.3 vs Group 2=89.5+/-19.3 bpm, p=0.144), with blunted HRR (Group 1= 1.08+/-0.10 vs Group 2= 1.36+/-0.31 bpm, p<0.01). HRR was unrelated to LVCR. CONCLUSIONS: HRR is almost abolished and unrelated to LVCR in brain-dead patients during DSE. The modulation of neural input to the heart is essential to determine HRR, and plays no significant role in determining the inotropic response during DSE.