Device Optimization
Cardiac resynchronization therapy improves important clinical endpoints in patients with reduced cardiac function and conduction abnormalities. However, approximately 1/3 of patients do not appear benefit. Atrio-ventricular (AV) and interventricular (VV) pacing-interval optimization acutely improves cardiac function, and may enhance the response to CRT relative to default interval settings among both the traditional responder and nonresponder groups. While pacing interval optimization is generally advocated, it is rarely done in practice because methods are time consuming and expensive, and data demonstrating clinical improvement are limited.
Because device optimization has the potential, as yet unproven, to significantly improve patient health with a low-cost, low-risk intervention, we view it as an important area of research, and have approached it from multiple fundamental directions. Remarkably, the field has lacked methods to assess the statistical significance of measured data and the precision of estimated optima. We have developed such tools and used them in a comparative study of multiple optimization techniques. The figure below shows an example of echocardiography (left panel) and impedence cardiography data (right panel) recorded from the same patient at the same optimization session, and highlights the danger of neglecting an assessment of statistical significance: programming the device according to the predicted optimum of the VTI data (left panel) would leave the patient with worse settings than the manufacturer’s default, as demonstrated by the highly significant and precise impedance cardiography data (right panel). Other ongoing work includes an examination of the practice of independent AV and VV optimization, a double-blind, randomized optimization trial with functional endpoints, and lead and timing optimization using invasive assessment of hemodynamics (see Hemodynamics of cardiac contractility).
