Left ventricular filling and stress response pattern in essential hypertension

To evaluate whether impaired left ventricular filling determines the hemodynamic responses to isometric and orthostatic stress in a population with mild essential hypertension.

The study population consisted of 32 patients with essential hypertension who were subdivided into those with preserved left ventricular filling (15 patients) and those with impaired left ventricular filling (17 patients). Echocardiograms were obtained before hemodynamic assessment was performed. Isometric stress and head-up tilt tests were done with a recovery period of at least 10 minutes between each to allow for blood pressure and heart rate to return to baseline. Hemodynamic reassessment was performed during the last minute of each test and at the end of the recovery period. Plasma epinephrine, norepinephrine, and dopamine levels were determined by radioenzymatic method.

Isometric stress increased mean arterial pressure by 30% (p less than 0.0001) by an increase in cardiac output (p less than 0.0001) and total peripheral resistance (p less than 0.0001) associated with an increase in plasma catecholamine levels (p less than 0.0001). Patients with preserved left ventricular filling had an increase in arterial pressure predominantly through an elevation in cardiac output (17%, p less than 0.0001) associated with a small increase in plasma norepinephrine levels (p less than 0.05) and in peripheral resistance (11%, p less than 0.05). In contrast, patients with impaired left ventricular filling had an increase in arterial pressure mainly through an increase in peripheral resistance (25%, p less than 0.0001) that was associated with a 45% elevation in plasma norepinephrine levels (p less than 0.0001). Orthostatic stress (passive head-up tilt) caused an exaggerated decrease in stroke volume (p less than 0.01) and cardiac output (p less than 0.01) in patients with impaired left ventricular filling when compared with those with preserved diastolic function.

Impaired left ventricular filling blunts the response of the heart to isometric and orthostatic stress. As a consequence, hypertensive patients with impaired ventricular filling respond to these stressors with enhanced sympathetic stimulation and exaggerated vasoconstriction.