What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Essential hypertension (n=19). Intervention: Essential hypertension vs. Normotension. Primary outcome: Total arterial resistance (dyn-s/cm5) (p=<0.001).

June 1, 1995

Arterial Hemodynamics in Human Hypertension

Q: What are the key findings of this study?

Essential hypertension in Chinese patients was associated with significantly higher total arterial resistance (2,295 vs. 1713 dyn-s/cm5) and characteristic impedance compared to normotensive controls.

Key Result

Essential hypertension in Chinese patients was associated with significantly higher total arterial resistance (2,295 vs. 1713 dyn-s/cm5) and characteristic impedance compared to normotensive controls.

Study Design

Type

Cross-Sectional (n=19)

Multicenter

Yes

Structured PICO

Do vasodilators (nifedipine, nitroprusside) or beta-blockers (propranolol) normalize arterial hemodynamic abnormalities in patients with essential hypertension?

Population

19 ethnic Chinese patients undergoing diagnostic cardiac catheterization, including 11 with recently diagnosed essential hypertension (mean age 34.8, 6 men/5 women) and 8 normotensive controls (mean age 41.9, 7 men/1 woman).

Intervention

Acute administration of vasodilators (sublingual nifedipine mean 24 mg, or IV sodium nitroprusside starting at 0.25 µg/kg/min) and beta-blocker (IV propranolol 0.15 mg/kg), as well as isometric handgrip exercise during cardiac catheterization.

Comparator

Normotensive control group matched for age, body size, and proportion of men and women, as well as baseline resting state within groups.

Outcome

Aortic input impedance, wave reflection magnitude, and arterial compliance computed from ascending aortic micromanometer pressures and electromagnetic flows.surrogate

Essential hypertension is characterized by increased arterial resistance and wave reflections that are normalized by vasodilators like nifedipine and nitroprusside, but exacerbated by beta-blockers.

Main Result

Absolute Event Rate: 2295% vs 1713%

p-value: p=<0.001

Limitations

Small sample size
Patients were undergoing cardiac catheterization for other indications, which may introduce selection bias
Potential sources of error involved in the calculation of characteristic impedance
Did not measure aortic compliance directly

Abstract

Previous studies have shown some distinct hemodynamic alterations in essential hypertension, including increased resistance, wave reflections, and pulse wave velocity and decreased arterial compliance. These abnormalities are completely normalized by nonspecific smooth muscle dilation with nitroprusside but not by combined alpha- and beta-adrenergic blockade or angiotensin-converting enzyme inhibition, suggesting an enhanced smooth muscle tone that cannot be attributed solely to the sympathetic nervous or renin-angiotensin systems. Since hypertensive patients have an enhanced calcium influx-dependent vasoconstriction, we performed the present study to examine the extent to which the dihydropyridine calcium channel antagonist nifedipine could normalize the hemodynamic abnormalities in essential hypertension. An essential hypertensive patient group was compared with a normotensive group similar in age, body size, and proportion of men and women. During diagnostic cardiac catheterization, ascending aortic micromanometer pressures and electromagnetic flows were measured at baseline and after sufficient sublingual nifedipine (mean, 24 mg) to normalize blood pressure. From the pressures and flows, aortic input impedance, wave reflection magnitude, and compliance were computed. In the hypertensive group, the hemodynamic alterations were indistinguishable from those summarized above. Nifedipine produced sufficient vasodilation to completely normalize all of these hemodynamic alterations, including wave reflections. From these results, together with those reported in our previous studies, it is clear that the various classes of antihypertensive agents affect hemodynamics differently. All are capable of decreasing blood pressure to normotensive levels, but only nitroprusside and nifedipine can also completely normalize all the other pulsatile hemodynamic alterations. Thus, these hemodynamic effects of the different classes of antihypertensive agents should be considered in choosing a therapeutic modality.

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