Left ventricular spherical dilation and regional contractile dysfunction in dogs with heart failure

Area of Science:

• Cardiology
• Physiology
• Biomedical Engineering

Background:

• Congestive heart failure (CHF) is a complex syndrome characterized by impaired cardiac function.
• Understanding the mechanisms of cardiac remodeling in heart failure is crucial for developing effective treatments.
• Pacing-induced heart failure models provide insights into the progression of cardiac dysfunction.

Purpose of the Study:

• To investigate the serial changes in left ventricular (LV) contractile function and structure during the development of congestive heart failure (CHF).
• To differentiate the mechanisms of LV dilation in pacing-induced CHF versus acute volume overload.
• To identify the role of heterogeneous contractile depression in initiating cardiac remodeling.

Main Methods:

• Serial measurements of LV short- and long-axis contractile function and structural changes in eight instrumented dogs.
• Induction of CHF using rapid right ventricular (RV) pacing over 30 days.
• Analysis of LV pressure-volume and pressure-dimension relations, and LV end-diastolic volume (VED).

Main Results:

• After 10 days of pacing, LV contractility decreased, particularly in the short axes, without significant VED increase.
• After 20 days, VED increased due to selective short-axis dilation, with further decline in LV global contractility.
• After 30 days, both short- and long-axis dimensions increased, contrasting with symmetrical dilation from acute volume loading.

Conclusions:

• Heterogeneous contractile depression, especially in the LV short axes, precedes and initiates spherical end-diastolic chamber dilation in pacing-induced CHF.
• Pacing-induced CHF leads to anisotropic LV remodeling, distinct from the isotropic remodeling seen in acute volume overload.
• These findings highlight the importance of regional myocardial function in the pathogenesis of heart failure progression.