Abstract 14082: The Effect of Diagnostic Ultrasound Mediated High Mechanical Impulses on Cardiac Output During an Ultrasound Enhancing Agent Infusion

Abstract

Introduction: Diagnostic ultrasound high mechanical index (MI) impulses are used during an ultrasound enhancing agent (UEA) infusion to improve endocardial border resolution and study myocardial perfusion. They have also been shown to cause endothelial shear, resulting in prolonged increases in ATP release and augment microvascular flow. The potential for these high MI impulses to alter cardiac output (CO) are unknown. Hypothesis: To study the impact of high MI impulses on CO Methods: Fifty one patients (mean age 63±15 years; 41% female) referred for contrast echocardiography underwent very low MI imaging with intermittent high MI impulses (1.6-1.7 Megahertz) in three different apical windows during either a Definity (Lantheus Medical) or Lumason (Bracco Diagnostics) infusion or bolus. CO was determined from Doppler measurements of left ventricular outflow tract stroke volume and heart rate. Mean contrast enhanced biplane left ventricular ejection fraction (LVEF) was 53±15%; (range 10-75%). CO from baseline without contrast (COwoC) and baseline after contrast (COwC) before high MI impulses were compared to CO after contrast and after high MI impulses (COaHMI). All CO measurements were made by an independent reviewer blinded to time of measurement (before or after high MI impulses). Results: Although heart rate did not change before and after intermittent high MI impulse administration, COaHMI increased significantly when compared to COwoC and COwC (p< 0.001 for both comparisons; Figure). In nine patients (18%), CO increased by more than 20%. In patients with LVEF < 40% COwC was 2.4±0.8 liters per minute (LPM) and COaHMI increased to 2.7± 0.8 LPM (p=0001). In patients with LVEF≥40%, COwC was 3.4±1.06 LPM while COaHMI increased to 3.8± 1.2 LPM (p=0.00001). Conclusions: Application of diagnostic guided high MI impulses during a commercially available microbubble infusion significantly increases CO irrespective of underlying left ventricular systolic function.