Regional geometry and function during myocardial ischemia and recovery

Area of Science:

• Cardiology
• Physiology
• Biomedical Engineering

Background:

• Left ventricular (LV) geometry influences regional myocardial function.
• Understanding geometric changes during ischemia and recovery is vital for assessing cardiac performance.

Purpose of the Study:

• To define the effects of altered LV geometry on regional myocardial function during ischemia and recovery.
• To investigate the correlation between geometric changes and functional recovery post-ischemia.

Main Methods:

• Measurements of regional and global LV geometry and transmural pressure in conscious dogs using sonomicrometry and micromanometry.
• Assessment of myocardial function during control, ischemia, and reperfusion periods.
• Calculation of regional midwall minor axis (MA) Lagrangian strain and stress, unstressed geometry (L0), and stroke work (SWL, SW sigma epsilon).

Main Results:

• Ischemia increased unstressed regional geometry (L0) by 15.2%, which persisted after 1 hour of reperfusion.
• Both steady-state SWL and SW sigma epsilon decreased significantly with ischemia and during early reperfusion.
• Regional Frank-Starling mechanisms (M sigma epsilon) normalized within 1 hour of reperfusion, despite persistent geometric alterations.

Conclusions:

• Late functional recovery from reversible ischemic injury is primarily linked to the reversal of regional geometric changes, specifically diastolic creep.
• Accurate quantification of post-ischemic myocardial performance necessitates evaluating both geometric alterations and Frank-Starling mechanisms.