- Email: [email protected]
Time-domain determination of systemic arterial properties in hypertension
AJH–APRIL 2000 –VOL. 13, NO. 4, PART 2
stroke volume in MTX. The C(P) waveforms can thus be used to provide a new measure of severity of hypertension in relation to arterial wall structure.
Key Words: Hypertension, pressure-dependent compliance, arteries B045 TIME-DOMAIN DETERMINATION OF SYSTEMIC ARTERIAL PROPERTIES IN HYPERTENSION J.K-J. Li*, Y. Zhu, J. Xiao, J.P. Matonick*, G. Drzewiecki*, D. O’Hara, J. Kedem, and J.B. Agarwal. Rutgers University and UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ Frequency domain impedance description of vascular properties is useful, but time-consuming and hinders rapid assessment of hemodynamic conditions and drug efficacy during routine catheterization. A fast time domain method was developed for transient intervention applications. Canine aortic pressure (P, mmHg) and flow (Q, ml/s) were obtained during control (CON), 20 s descending thoracic aortic (DTA) occlusion and bolus nitroprusside (NTP: 10 g/ml i.v.) infusion, resulting in transient changes of mean P between 68 and 139 mmHg. Arterial properties were assessed by Zo (mmHg/ml/s) ⫽ characteristic impedance ⫽ ratio of P/Q at early ejection, C(ml/ mmHg) ⫽ arterial compliance ⫽ /Rs with ⫽ diastolic P decay time constant, and Rs(mmHg/ ml/s) ⫽ peripheral resistance ⫽ Pmean/Qmean. Zo, Rs and C for CON vs. DTA and NTP are: 0.20⫾0.02 vs. 0.26⫾0.03 and 0.19⫾0.02, 3.65⫾0.21 vs. 6.54⫾0.43 and 2.25⫾0.23, 0.45⫾0.08 vs. 0.23⫾0.07 and 0.84⫾0.12, respectively. These values correlated well with those obtained by the impedance method (p⬍0.01, p⬍0.001, p⬍0.01 for Zo, Rs and C, respectively). Forward and reflected waves can also be resolved. This time-domain method provides beat-to-beat on-line determination of arterial properties and allows rapid assessment of hypertension conditions and evaluation of antihypertensive drug efficacy. Key Words: Arterial compliance; peripheral resistance; vascular impedance; wave reflections B046 INCREASED ARTERIAL STIFFNESS ASSESSED BY PULSE WAVE ANALYSIS IN PATIENTS WITH HYPERCHOLESTEROLAEMIA † I.B. Wilkinson, †H. MacCallum, A. Thomas, M. Van der Steen, M.P. Frenneaux, †D.J. Webb, and J.R. Cockcroft. † Department of Medical Sciences, University of Edinburgh, Western General Hospital, Edinburgh. Department of Cardiology, University of Wales College of Medicine, Cardiff
POSTERS: Arterial Structure and Compliance
203A
Arterial stiffness is an important determinant of cardiovascular risk, which may, in part, be regulated by the vascular endothelium. Hypercholesterolaemia (HC) is associated with endothelial dysfunction and a decrease in the production of endogenous nitric oxide (NO) which may be reflected in an increase in arterial stiffness. Pulse wave analysis (PWA) uses applanation tonometry to record peripheral pressure waveforms from which central pressures and augmentation index (AIx) can be determined. AIx represents the effect wave reflection has on central pressure, and is, therefore, a measure of systemic arterial stiffness. We hypothesised that patients with a raised cholesterol (⬎6.5 mmol/l) would have increased arterial stiffness as compared to a group of matched controls. 31 HC patients (age 50 ⫾ 2 yrs) and 31 controls (age 48 ⫾ 2 yrs) were recruited from two centres: Edinburgh and Cardiff. Both groups were screened for established cardiovascular disease. Blood pressure (HEM-705CP; Omron, Japan) and AIx (Sphygmocor BPAS-1-1; PWV) Medical, Australia) were measured in duplicate in each subject following 5 minutes of seated rest. Venous blood was then drawn to measure total serum cholesterol. The results are quoted as mean ⫾ SEM. Total serum cholesterol was significantly higher in HC patients as compared to the control group (7.1 ⫾ 0.1 mmol/l versus 5.2 ⫾ 0.1 mmol/l; p⬍0.0001) AIx in the control group was 13.5 ⫾ 1.8% compared to 21.6 ⫾ 1.9% in the HC group (p⬍0.005). There were no significant differences in any of the other parameters, including blood pressure, heart rate or height. In conclusion, we have shown that HC is associated with increased arterial stiffness, as assessed by AIx. This may be explained, in part, by a reduction in the bioavailability of nitric oxide as a result of endothelial dysfunction in HC. Moreover, studies are required to establish whether cholesterol lowering will reduce arterial stiffening which may assist in assessing the likely underlying cause of increased stiffness. Key Words: Human; cholesterol; arterial stiffness B047 AORTIC STIFFNESS IN NEVER-TREATED HYPERTENSIVES: LACK OF RELATION WITH MYOCARDIAL HYPERTROPHY AND IMPAIRED LEFT VENTRICULAR RELAXATION A.M. Grandi*, D. Imperiale, R. Santillo, S. Colombo, R. Broggi, A. Bertolini, L. Guasti, E. Selva, A. Jessula, A. Venco. Department of Clinical and Biological Sciences—Faculty of Medicine—University of Insubria—Varese—Italy Aim of the study was the evaluation of the relationship between the degree of aortic stiffness and left ventricular (LV) morpho-functional changes in hypertension. Using carotid-femoral pulse wave velocity (PWV), as index of aortic distensibility, 24-hour blood pressure (BP) monitoring, Doppler and digitized M-mode echocardiography, we studied never-treated hypertensives (H) with aortic stiffness greater or similar to that expected (measured PWV ⬎ or ⱕ PWV expected on the basis of age, sex, heart rate, BP, BMI). We enrolled never-treated H (day-time BP ⱖ 140 and/or 90 mmHg): 49 H (Gr 1)(28 men, 42.7⫾10 years, BMI 25.6⫾3.7
stroke volume in MTX. The C(P) waveforms can thus be used to provide a new measure of severity of hypertension in relation to arterial wall structure.
Key Words: Hypertension, pressure-dependent compliance, arteries B045 TIME-DOMAIN DETERMINATION OF SYSTEMIC ARTERIAL PROPERTIES IN HYPERTENSION J.K-J. Li*, Y. Zhu, J. Xiao, J.P. Matonick*, G. Drzewiecki*, D. O’Hara, J. Kedem, and J.B. Agarwal. Rutgers University and UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ Frequency domain impedance description of vascular properties is useful, but time-consuming and hinders rapid assessment of hemodynamic conditions and drug efficacy during routine catheterization. A fast time domain method was developed for transient intervention applications. Canine aortic pressure (P, mmHg) and flow (Q, ml/s) were obtained during control (CON), 20 s descending thoracic aortic (DTA) occlusion and bolus nitroprusside (NTP: 10 g/ml i.v.) infusion, resulting in transient changes of mean P between 68 and 139 mmHg. Arterial properties were assessed by Zo (mmHg/ml/s) ⫽ characteristic impedance ⫽ ratio of P/Q at early ejection, C(ml/ mmHg) ⫽ arterial compliance ⫽ /Rs with ⫽ diastolic P decay time constant, and Rs(mmHg/ ml/s) ⫽ peripheral resistance ⫽ Pmean/Qmean. Zo, Rs and C for CON vs. DTA and NTP are: 0.20⫾0.02 vs. 0.26⫾0.03 and 0.19⫾0.02, 3.65⫾0.21 vs. 6.54⫾0.43 and 2.25⫾0.23, 0.45⫾0.08 vs. 0.23⫾0.07 and 0.84⫾0.12, respectively. These values correlated well with those obtained by the impedance method (p⬍0.01, p⬍0.001, p⬍0.01 for Zo, Rs and C, respectively). Forward and reflected waves can also be resolved. This time-domain method provides beat-to-beat on-line determination of arterial properties and allows rapid assessment of hypertension conditions and evaluation of antihypertensive drug efficacy. Key Words: Arterial compliance; peripheral resistance; vascular impedance; wave reflections B046 INCREASED ARTERIAL STIFFNESS ASSESSED BY PULSE WAVE ANALYSIS IN PATIENTS WITH HYPERCHOLESTEROLAEMIA † I.B. Wilkinson, †H. MacCallum, A. Thomas, M. Van der Steen, M.P. Frenneaux, †D.J. Webb, and J.R. Cockcroft. † Department of Medical Sciences, University of Edinburgh, Western General Hospital, Edinburgh. Department of Cardiology, University of Wales College of Medicine, Cardiff
POSTERS: Arterial Structure and Compliance
203A
Arterial stiffness is an important determinant of cardiovascular risk, which may, in part, be regulated by the vascular endothelium. Hypercholesterolaemia (HC) is associated with endothelial dysfunction and a decrease in the production of endogenous nitric oxide (NO) which may be reflected in an increase in arterial stiffness. Pulse wave analysis (PWA) uses applanation tonometry to record peripheral pressure waveforms from which central pressures and augmentation index (AIx) can be determined. AIx represents the effect wave reflection has on central pressure, and is, therefore, a measure of systemic arterial stiffness. We hypothesised that patients with a raised cholesterol (⬎6.5 mmol/l) would have increased arterial stiffness as compared to a group of matched controls. 31 HC patients (age 50 ⫾ 2 yrs) and 31 controls (age 48 ⫾ 2 yrs) were recruited from two centres: Edinburgh and Cardiff. Both groups were screened for established cardiovascular disease. Blood pressure (HEM-705CP; Omron, Japan) and AIx (Sphygmocor BPAS-1-1; PWV) Medical, Australia) were measured in duplicate in each subject following 5 minutes of seated rest. Venous blood was then drawn to measure total serum cholesterol. The results are quoted as mean ⫾ SEM. Total serum cholesterol was significantly higher in HC patients as compared to the control group (7.1 ⫾ 0.1 mmol/l versus 5.2 ⫾ 0.1 mmol/l; p⬍0.0001) AIx in the control group was 13.5 ⫾ 1.8% compared to 21.6 ⫾ 1.9% in the HC group (p⬍0.005). There were no significant differences in any of the other parameters, including blood pressure, heart rate or height. In conclusion, we have shown that HC is associated with increased arterial stiffness, as assessed by AIx. This may be explained, in part, by a reduction in the bioavailability of nitric oxide as a result of endothelial dysfunction in HC. Moreover, studies are required to establish whether cholesterol lowering will reduce arterial stiffening which may assist in assessing the likely underlying cause of increased stiffness. Key Words: Human; cholesterol; arterial stiffness B047 AORTIC STIFFNESS IN NEVER-TREATED HYPERTENSIVES: LACK OF RELATION WITH MYOCARDIAL HYPERTROPHY AND IMPAIRED LEFT VENTRICULAR RELAXATION A.M. Grandi*, D. Imperiale, R. Santillo, S. Colombo, R. Broggi, A. Bertolini, L. Guasti, E. Selva, A. Jessula, A. Venco. Department of Clinical and Biological Sciences—Faculty of Medicine—University of Insubria—Varese—Italy Aim of the study was the evaluation of the relationship between the degree of aortic stiffness and left ventricular (LV) morpho-functional changes in hypertension. Using carotid-femoral pulse wave velocity (PWV), as index of aortic distensibility, 24-hour blood pressure (BP) monitoring, Doppler and digitized M-mode echocardiography, we studied never-treated hypertensives (H) with aortic stiffness greater or similar to that expected (measured PWV ⬎ or ⱕ PWV expected on the basis of age, sex, heart rate, BP, BMI). We enrolled never-treated H (day-time BP ⱖ 140 and/or 90 mmHg): 49 H (Gr 1)(28 men, 42.7⫾10 years, BMI 25.6⫾3.7