Hemodynamic effects of unloading the old heart

Area of Science:

• Cardiology
• Gerontology
• Exercise Physiology

Background:

• Aging is associated with reduced upright exercise capacity.
• This decline is linked to acute left ventricular (LV) dilatation and impaired LV ejection.
• Adverse loading conditions may contribute to age-related cardiac dysfunction during exercise.

Purpose of the Study:

• To investigate if acute vasodilator administration can improve left ventricular (LV) ejection during exercise in older adults.
• To determine the effects of sodium nitroprusside (NP) on LV ejection fraction (EF) and other cardiac parameters during exercise.

Main Methods:

• 16 healthy older adults (64-84 yr) with no coronary heart disease were studied.
• Sodium nitroprusside (NP) was infused, titrated to reduce resting mean arterial pressure by 10%.
• LV ejection fraction (EF), stroke volume, stroke work, cardiac index, and work rate were measured during graded cycle exercise compared to placebo.

Main Results:

• NP infusion significantly increased LV ejection fraction (EF) at all exercise work rates compared to placebo.
• Stroke volume and stroke work were maintained with a smaller end-diastolic volume during NP infusion.
• The maximum increase in exercise EF with NP in older adults matched that of younger controls.
• Maximum exercise work rate and cardiac index remained unchanged with NP.

Conclusions:

• Combined preload and afterload reduction with NP improves LV ejection phase function in older individuals.
• Exercise LV stroke work is reduced, EF is increased, and stroke volume is maintained with reduced ventricular size.
• Age-associated decline in cardiac function during maximal aerobic exercise may be partly due to adverse loading conditions.