The influence of changes in loading patterns on left ventricular relaxation in humans

Area of Science:

• Cardiovascular Physiology
• Cardiac Mechanics
• Hemodynamics

Background:

• Left ventricular (LV) relaxation is a critical determinant of diastolic function.
• Understanding factors influencing LV relaxation is essential for diagnosing and managing cardiovascular diseases.
• Loading conditions and pressure wave characteristics can affect cardiac performance.

Purpose of the Study:

• To investigate the effect of altered loading patterns on left ventricular (LV) relaxation.
• To determine the role of ascending aortic systolic pressure wave contour in LV relaxation.
• To maintain a constant heart rate during the investigation of these effects.

Main Methods:

• Twenty patients were studied using a multisensor catheter to measure LV and ascending aortic pressure.
• Pharmacological interventions (angiotensin and nitroglycerin) were used to alter loading conditions.
• The augmentation index (AI) characterized the aortic pressure wave contour.
• The time constant (Tau) quantified the rate of isovolumic LV pressure decline.

Main Results:

• Ascending aortic systolic pressures varied significantly with interventions (127±29 mmHg baseline, 158±20 mmHg angiotensin, 109±15 mmHg nitroglycerin).
• The augmentation index (AI) also changed (1.61±1.14 baseline, 2.08±1.11 angiotensin, 1.27±1.14 nitroglycerin).
• The time constant (Tau) for LV pressure decline was prolonged with increasing AI (p<0.001, r=0.64), indicating slower relaxation.

Conclusions:

• Late systolic pressure augmentation in the ascending aorta is a significant factor influencing the rate of isovolumic left ventricular pressure decline.
• Altered loading conditions affect both the aortic pressure wave contour and LV relaxation.
• These findings provide insights into the interplay between systemic hemodynamics and diastolic function.