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Influence of left ventricular diastolic function on vascular and humoral responses to head-up posture in hypertension
M A Madkour1, F M Fouad-Tarazi
1Department of Heart and Hypertension Research, Cleveland Clinic Foundation, OH 44195-5069.
Insights
Hypertension can impair left ventricular (LV) diastolic filling. Reduced LV filling in hypertensive patients leads to a blunted increase in total peripheral resistance during head-up tilt, indicating abnormal cardiovascular adjustment.
Area of Science:
- Cardiology
- Physiology
Background:
- Hypertension is often associated with reduced left ventricular (LV) diastolic filling rates.
- Altered LV diastolic function may impact the body's ability to regulate peripheral vascular resistance.
Purpose of the Study:
- To investigate how impaired LV diastolic function in hypertensive patients affects peripheral vascular regulation.
- To examine hemodynamic responses during postural changes (head-up tilt) in relation to LV filling rates.
Main Methods:
- Hemodynamic measurements were taken in 16 hypertensive patients (7 men, 9 women; age 30-62).
- Measured parameters included LV peak filling rate, LV peak ejection rate, ejection fraction, heart rate, total peripheral resistance, stroke volume, and cardiac index.
- The ratio of LV filling rate to ejection rate (+dv/dt/-dv/dt) was calculated.
Main Results:
- Patients with a slow LV diastolic filling rate (ratio < 0.9) showed a less pronounced increase in total peripheral resistance during head-up tilt compared to those with normal filling (ratio >= 0.9).
- Stroke volume changes during tilt did not differ significantly between groups.
- No significant differences in supine resting cardiac index or total peripheral resistance were observed among groups.
Conclusions:
- Abnormal left ventricular diastolic filling is linked to impaired cardiovascular adjustments to postural changes.
- The blunted response to head-up tilt may stem from reduced sensitivity of cardiopulmonary low-pressure receptors due to impaired LV diastolic function.
Abstract:
The left ventricular (LV) diastolic filling rate has been reported to be reduced in hypertensive patients. To investigate the possible influence of altered LV diastolic function in hypertension on peripheral vascular regulation, hemodynamic measurements were obtained in 16 hypertensive patients in the resting supine position and during head-up tilt. The study population included seven men and nine women with an age range of 30 to 62 years (mean, 49.5 years +/- 10.6). Measurements included LV peak filling rate (+dv/dt), LV peak ejection rate (-dv/dt), LV ejection fraction, heart rate, total peripheral resistance, stroke volume, and cardiac index. Moreover, we calculated the ratio relating left ventricular filling rate to left ventricular ejection rate (+dv/dt/-dv/dt) because a complex interaction between ventricular contraction and relaxation is well recognized. We observed that in patients with slow diastolic filling rate (ratio +dv/dt/-dv/dt less than 0.9), the increase in total peripheral resistance in response to head-up tilt was less marked than in those with normal LV filling rate (+dv/dt/-dv/dt greater than or equal to 0.9), whereas changes in stroke volume during tilt were not statistically different between the two groups. Conversely, supine resting cardiac index and total peripheral resistance was not significantly different among groups. We conclude that abnormal diastolic filling is associated with abnormal cardiovascular adjustment to changes in body posture. We suggest that the altered response to head-up posture is related to decreased sensitivity of low pressure receptors in the cardiopulmonary area as a result of impaired LV diastolic function.(ABSTRACT TRUNCATED AT 250 WORDS)