Effects of Various Left Ventricular Assist Device Models on Echocardiographic Markers of Aortic Compliance

Abstract

The HeartMate 3 (HM3) left ventricular assist device (LVAD) is known to cause increased shear stress on the aortic wall related to the acceleration phase of the artificial pulse. We hypothesized that aortic compliance, as assessed by 2D transthoracic echocardiography (TTE), would be increased in patients with the HeartMate 3 LVAD as compared to the Heartmate 2 (HM2) or HeartWare HVAD, based on the hemodynamic properties of each device. We identified 30 patients with HM3, HM2, and HVAD left ventricular assist devices, respectively. The groups did not differ significantly in terms of age, gender, or rates of hypertension, diabetes, or chronic kidney disease. For each patient, we identified the most recent echocardiogram with a recorded blood pressure at the time of the study. Ascending aortic diameters were measured 3 centimeters above the aortic valve in the parasternal long-axis view and used to calculate aortic strain and aortic distensibility, two markers of aortic compliance. The following calculations were used to obtain aortic strain and aortic distensibility: aortic strain = (aortic diameter end-systole - aortic diameter end-diastole) / aortic diameter end-diastole * 100 and aortic distensibility = 2 * aortic strain / pulse pressure * 1000. The HM3 had higher indices of aortic strain and aortic distensibility compared to the HM2 and HVAD patients, respectively. Aortic strain was significantly increased in the HM3 compared to the HM2 (8.3±3.1% vs. 6.2±1.9%, p=0.002) patients as well as compared to the HVAD patients (8.3±3.1% vs. 4.3±1.7%, p=0.0001). Aortic distensibility was not significantly increased between the HM3 and the HM2 patients (7.8±4.0 vs. 6.5±4.2 cm2dyne-110-3, p=0.23), but was significantly increased between the HM3 and the HVAD patients (7.8±4.0 vs. 4.4±2.6 cm2dyne-110-3, p=0.0002). Echocardiographic markers of aortic compliance differ in HM3 LVADs compared to HM2 and HVAD models. This could be due to increased shear stress on the aortic wall in HM3 patients, though further studies with more robust methods of measuring aortic compliance are needed to confirm these results.