P 20: Coronary microvascular response to a coldpressor test and cardiac autonomic neuropathy in asymptomatic type 2 diabetic patients free of coronary stenoses

Abstract

The cold-pressor test (CPT) by inducing sympathetic stimulation and a subsequent rise in myocardial oxygen demand is expected to induce an increase in coronary blood flow and a dilation of normal epicardial coronary arteries. The aim of this study was in type 2 diabetic patients (T2Ds) free of coronary stenoses to analyse the influence of cardiac autonomic neuropathy (CAN) on the coronary response to CPT measured with a non invasive method based on trans-thoracic echography-doppler (NCT00685984). We prospectively screened 118 T2Ds, without any cardiac history and fulfilling the criteria of the French guidelines, for silent myocardial ischemia (SMI: abnormal stress myocardial scintigraphy and/or echocardiography). A coronary angiography was performed in those with SMI. The distal inter-ventricular anterior coronary velocity (CV) was measured by trans-thoracic echo-doppler before and after CPT (one hand immersed in crushed ice for 120 s) in these patients and also in 16 control subjects. CAN was assessed using three standard tests (deep-breathing, lying-to-standing and Valsalva) and considered to be present if ≥2 tests were abnormal. CV before and after CPT could be measured reliably in 35 T2Ds free of coronary stenoses and with CAN function tests being performed and in all control subjects. CAN was found in 17 T2Ds. At baseline, T2Ds had higher heart rate, rate-pressure product (DP) and CV than controls (p<0.05 to <0.0001) with slightly higher levels in those with CAN. Changes after CPT/baseline in DP were lower in T2Ds with CAN than in those without CAN (26±7 vs 52±6% increase, p=0.02; 32±5% in controls) whereas changes in CV did not differ significantly in T2Ds with or without CAN and in control subjects. CV changes during CPT, i.e. related to microcirculation, correlated with DP changes in controls (r=0.45, p<0.06) and in T2Ds without CAN (r=0.65, p<0.01) but did not in those with CAN. T2Ds without evidence of coronary artery disease but with impaired vagal cardiac tests exhibit at baseline some signs of relative increase in sympathetic activity. They have a lower increase in DP after CPT which is consistent with a lower sympathetic reactivity but this increase in myocardial oxygen demand resulting from sympathetic stimulation is sufficient to increase coronary blood flow.