P3.05 Deranged Vascular-Ventricular Coupling in Heart Failure Patients with Depressed Left Ventricular Contractility: Importance of Aortic Characteristic Impedance

Deranged vascular-ventricular coupling (VVC) occurs in heart failure (HF) when arterial elastance (Ea) is increased and/or left ventricular (LV) elastance (Elv) is depressed, leading to increased coupling ratio Ea/Elv. While calculation of Ea is simple (below), it represents the ’lumped’ elastance of the arterial tree some of which is attributable to aortic characteristic impedance (Zc) which is more difficult to quantify. We examined the importance of Zc for VVC in 22 patients (7 with HF, 31%; 15 non-HF controls) who underwent echocardiography and analysis of central pressure waveform synthesised from radial artery pressure (SphygmoCor, AtCor Medical, Sydney, Australia). LV outflow tract Doppler recordings were digitised (custom software) and Zc was calculated as the ratio between pressure and flow in early systole before onset of wave reflections. Ea (LV end-systolic pressure / stroke volume (SV)) and Elv (single-beat method) were estimated; compliance (SV / brachial pulse pressure) and total peripheral resistance (TPR: mean arterial pressure / cardiac output) were computed. We found that HF patients had deranged VVC largely due to higher Ea (Table 1). Zc correlated strongly to Ea (r = 0.65; p = 0.02) and to Ea/Elv (0.80; p = 0.001) but neither to Elv (p = 0.81) nor higher age (p = 0.12). In conclusion, elevated Zc contributes to the deranged VVC seen in systolic HF. Variable HF Non-HF p-Value Age (years) 70 ± 11 54 ± 18 0.045 LVEF (%) 29 ± 15 52 ± 17 0.023 Compliance (mL/mmHg) 0.7 ± 0.3 1.1 ± 0.5 0.07 TPR (mmHg•s/mL) 0.03 ± 0.01 0.04 ± 0.04 0.84 Ea (mmHg/mL) 3.0 ±1.5 1.7 ± 0.4 0.029 Zc (mmHg•s/mL) 0.39 ± 0.08 0.20 ± 0.06 0.01 Elv (mmHg/mL) 1.7 ± 1.0 2.3 ± 0.3 0.07 VVC ratio: Ea/Elv 0.75 ± 0.17 2.3 ±1.5