The Challenge of Chamber Stiffness Determination in Chronic Atrial Fibrillation vs. Normal Sinus Rhythm:...

Area of Science:

• Cardiology
• Biomedical Engineering
• Echocardiography

Background:

• Diastolic function (DF) assessment in atrial fibrillation (AF) is challenging due to limitations of standard echocardiographic indexes and chamber remodeling.
• Chronic, rate-controlled AF can alter cardiac chamber properties, complicating DF evaluation.

Purpose of the Study:

• To determine if echocardiography can accurately characterize diastolic chamber properties in chronic AF.
• To compare conventional DF parameters and a novel kinematic modeling-derived chamber stiffness index (k) against invasive measurements.

Main Methods:

• Simultaneous echocardiography and cardiac catheterization were performed on 15 chronic AF and 15 age-matched normal sinus rhythm (NSR) subjects.
• Conventional DF parameters (DT, Epeak, AT, Edur, E-VTI, E/E') and the chamber stiffness parameter (k) were analyzed.
• Invasive chamber stiffness (dP/dV) was determined from multi-beat P-V loop data for validation.

Main Results:

• Standard indexes like AT, Epeak, and E-VTI did not differentiate between AF and NSR groups.
• DT, Edur, and E/E' showed differences, but the model-derived chamber stiffness parameter (k) was the only index specific for chamber stiffness (p < 0.005).
• Passive (diastatic) chamber stiffness was significantly greater in AF than in NSR (p < 0.05), a finding not evident from invasive end-diastolic stiffness measurements alone.

Conclusions:

• Passive (diastatic) chamber stiffness is increased in normal ejection fraction chronic, rate-controlled AF hearts compared to NSR controls.
• The E-wave derived chamber stiffness index (k) differentiates AF from NSR groups, offering improved characterization of diastolic properties.
• This study provides mechanistic insight into altered diastolic mechanics in AF, highlighting the utility of advanced echocardiographic modeling.