Reduced left ventricular functional reserve in hypertensive patients with preserved function at rest

Area of Science:

• Cardiology
• Cardiovascular Physiology
• Hypertension Research

Background:

• Hypertensive patients often exhibit normal resting left ventricular pump function, but abnormal function during exercise.
• Potential causes include myocardial dysfunction or altered left ventricular loading.
• This study investigates impaired myocardial functional reserve in the hypertensive heart.

Purpose of the Study:

• To assess stress-adjusted midwall shortening response to dobutamine infusion in hypertensive individuals with normal resting function.
• To identify subtle myocardial dysfunction masked at rest.
• To explore the relationship between this dysfunction and cardiac structural changes.

Main Methods:

• Sixty-five subjects (45 hypertensive, 20 normotensive) received graded low-dose dobutamine (1-5 microg x kg(-1) x min(-1)).
• Echocardiography (2D, M-mode, Doppler) assessed cardiac function at baseline and during infusion.
• Midwall shortening response to dobutamine was analyzed, defining a normal response based on control group data.

Main Results:

• Normotensive controls showed a significant increase in midwall shortening with dobutamine.
• Hypertensive subjects were divided into normal (Group I) and subnormal (Group II) responders.
• Group II (subnormal response) had greater left ventricular relative wall thickness than Group I, despite similar blood pressure and mass.

Conclusions:

• Very-low-dose dobutamine unmasks subtle impairment of myocardial functional reserve in hypertensive patients with normal resting function.
• This myocardial dysfunction is associated with increased left ventricular relative wall thickness.
• Hypertension-induced cardiac alterations can affect functional reserve even before resting dysfunction is apparent.