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Effects of changes in atrioventricular gradient and contractility on left ventricular filling in human diastolic
D J Lenihan1, M C Gerson, G W Dorn
1Department of Internal Medicine, University of Cincinnati, OH 45267-0542, USA.
Insights
Left ventricular diastolic filling is primarily influenced by the atrioventricular gradient, not isovolumic relaxation rate. This finding is crucial for understanding diastolic dysfunction in hypertension patients.
Area of Science:
- Cardiology
- Physiology
Background:
- Diastolic filling abnormalities in hypertension are not fully understood.
- Noninvasive testing of diastolic function requires further investigation.
Purpose of the Study:
- To investigate left ventricular diastolic filling indexes.
- To assess the impact of atrioventricular gradient and isovolumic relaxation on diastolic function.
Main Methods:
- Radionuclide angiography during right atrial pacing.
- Direct measurement of left atrioventricular gradient.
- Assessment of isovolumic relaxation time constant.
- Altering loading conditions (nitroprusside, phenylephrine) and contractility (dobutamine).
Main Results:
- Maximum left atrioventricular gradient depends on loading conditions.
- Left atrioventricular gradient is not significantly affected by contractility or relaxation.
- Peak filling rate is highly dependent on the atrioventricular gradient.
- Peak filling rate is not affected by improved isovolumic relaxation rate.
Conclusions:
- Left ventricular diastolic filling is primarily determined by the atrioventricular gradient.
- Isovolumic relaxation rate does not significantly impact peak filling rate in this cohort.
- Findings offer insights into diastolic dysfunction mechanisms in hypertensive patients.
Abstract:
The factors responsible for abnormalities in diastolic filling indexes as assessed by noninvasive testing in human beings have been extensively studied but are not completely understood. We therefore investigated left ventricular diastolic filling indexes by radionuclide angiography during right atrial pacing simultaneously with assessment of a directly measured left atrioventricular gradient and a time constant of isovolumic relaxation in 11 patients with hypertension and diastolic dysfunction. Loading conditions were altered with nitroprusside and phenylephrine, and contractility was improved by dobutamine infusion. The maximum left atrioventricular gradient at constant heart rates was determined by loading conditions and was not significantly affected by increases in contractility or an improvement in isovolumic relaxation rate. The peak filling rate according to radionuclide angiography was highly dependent on the atrioventricular gradient and was not affected by enhancement of the isovolumic relaxation rate.