Gonzalo Varela

Resynchronization improves heart-arterial coupling reducing arterial load determinants

BACKGROUND Cardiac resynchronization therapy (CRT) has benefits on left ventricle (LV) performance, but its mid-term effects on LV load and LV-arterial coupling are unknown. AIMS To evaluate CRT mid-term effects on LV-arterial coupling, arterial load and its determinants, and the association between CRT-dependent aortic haemodynamic changes and the arterial biomechanics. METHODS AND RESULTS Cardiac and aortic echographies were done in 25 patients (age: 61 ± 12 years; 14 men; New York Heart Association functional classes III-IV; LV ejection fraction = 28 ± 7%, QRS = 139 ± 20 ms) before and after (23 ± 12 days) CRT. Standard structural and functional parameters and dyssynchrony indices were evaluated. Ascending aorta flow and diameter waveforms were measured. Central pressure was derived using a transfer function and the diameter calibration method. Calculus: arterial elastance (EA); aortic impedance (Zc) and distensibility (AD); systemic resistances (SVR), total compliance (CT); global reflection coefficient; LV end-systolic elastance (EES); and LV-arterial coupling (EA/EES). After CRT EA diminished (-30%;P = 0.001), EES increased (29%; P = 0.001) and EA/EES improved (pre-CRT: 2.9 ± 0.9, post-CRT: 1.6 ± 0.7; P = 0.001). Arterial elastance changes were associated with changes in arterial properties. Cardiac resynchronization therapy was associated with pressure-independent increase in mean aortic diameter (pre-CRT: 30.0 ± 4.0 mm, post-CRT: 33.0 ± 5.1 mm; P = 0.005) and distensibility (pre-CRT: 3.8 ± 2.6 × 10(-3)mmHg(-1), post-CRT: 6.4 ± 2.5 × 10(-3) mmHg(-1); P = 0.002), and Zc reduction (pre-CRT: 3.5 ± 1.8 × 10(-2)mmHg.s/mL, post-CRT:1.9 ± 0.8 × 10(-2) mmHg.s/mL; P = 0.001) and SVR (pre-CRT:1.7 ± 0.4 mmHg.s/mL, post-CRT:1.0 ± 0.3 mmHg.s/mL; P = 0.001). Changes in EA determinants were associated with changes in aortic flow. CONCLUSION Early after CRT central and peripheral arterial biomechanics improved, determining a pressure-independent increase in aortic diameter and a reduction in arterial load. Left ventricular systolic performance and LV-arterial coupling were enhanced. Arterial biomechanical changes were associated with aortic flow changes.

Cardiac resynchronization results in aortic blood flow-associated changes in the arterial load components: Basal biomechanical conditions determine the load changes

The cardiac resynchronization therapy (CRT) effects on the arterial load components, the mechanisms (i.e. haemodynamic changes-dependence) involved in the load reduction and the factors (i.e. basal load conditions) associated with the load changes after CRT, are to be evaluated. Aims: a) to analyze the potential changes in the arterial load components (peripheral resistances, arterial compliance and impedance) associated with the CRT, b) to determine if the load components changes are associated with variations in haemodynamic variables (pressure, heart rate or blood flow), c) to analyze the relationship between the load components basal state and their changes after CRT. To fulfill these aims cardiac and arterial structural and mechanical parameters were non-invasively evaluated in 8 heart failure patients, pre- and post-CRT (23±8 days). The main results were that short-term after CRT: 1) there were changes in the static and dynamic determinants of the arterial load; 2) the changes in the load components were not associated with heart rate or pressure variations, but with blood flow changes, and 3) the load components basal levels and their changes after CRT were associated.