Impaired Vasoreactivity in End-Stage Heart Failure Patients on Intravenous Inotropic Support

The effect of dobutamine without and with L-arginine on arterial compliance in heart failure patients

The effect of dobutamine on carotid and brachial arteries compliance and the association of L-arginine as a potential nitric oxide pathway restorer were evaluated in patients with heart failure. Twenty-seven outpatients participated. Drugs used for the treatment of heart failure were withheld at least 24 hours before the study. The carotid and brachial artery diameters and hemodynamic variables were evaluated by ultrasonography and Doppler in baseline conditions, with dobutamine, with flow-mediated dilatation (FMD), and with placebo or L-arginine alone and associated with dobutamine. There was a significant increase in carotid peak blood flow with dobutamine when compared with that at baseline (P = 0.0001) or with L-arginine or placebo (P = 0.0001 and P = 0.0001, respectively), with increase of the cardiac index (P = 0.0001). Dobutamine did not increase carotid arterial compliance. FMD significantly increased the brachial peak blood flow (P = 0.0022) and the artery diameter (P = 0.0001). Dobutamine did not change the brachial artery diameter. Brachial peak blood flow was increased with dobutamine alone or associated with placebo or L-arginine comparing with L-arginine or placebo alone (P = 0.0168 and P = 0.0140, respectively), but was not increased compared with that at baseline. L-arginine infusion was not associated with changes in carotid, brachial, or in the cardiac index. We concluded that dobutamine increased carotid peak blood flow in patients with heart failure, although without changing the arterial compliance. The FMD of brachial artery was maintained, while brachial artery response to dobutamine infusion was less reliable. The carotid artery may be under the direct influence of the heart, while the brachial artery may be under predominant local control.

Inotropic agents improve the peripheral microcirculation of patients with end-stage chronic heart failure

BACKGROUND

Skeletal muscle microcirculation impairment in patients with chronic heart failure (CHF) seems to correlate with disease severity. We evaluated the microcirculation by near-infrared spectroscopy (NIRS) occlusion technique before and after inotropic infusion.

METHODS

We evaluated 25 patients with stable CHF, 30 patients with end-stage CHF (ESCHF) receiving treatment with intermittent infusion of inotropic agents, and 12 healthy subjects. Thenar muscle tissue oxygen saturation (StO(2)%) was measured noninvasively by NIRS before, during, and after 3-minute occlusion of the brachial artery (occlusion technique) in all subjects and in patients with ESCHF before and after 6 hours of inotropic infusion (dobutamine and/or levosimendan) or placebo (N = 5).

RESULTS

Patients with ESCHF or CHF presented significantly lower StO(2)% than healthy subjects (74.5% +/- 7%, 78.6% +/- 6%, and 85% +/- 5%, respectively; P = .0001), lower oxygen consumption rate during occlusion (24.6% +/- 8%/min, 28.6% +/- 10%/min, and 38.1% +/- 11.1%/min, respectively; P = .001), and lower reperfusion rate (327% +/- 141%/min, 410% +/- 106%/min, and 480% +/- 133%/min, respectively; P = .002). After 6 hours of inotropic infusion, patients with ESCHF showed significantly increased StO(2)% (74.5% +/- 7% to 82% +/- 9%, P = .001), oxygen consumption rate (24.6% +/- 8%/min to 29.3% +/- 8%/min, P = .009), and reperfusion rate (327% +/- 141%/min to 467% +/- 151%/min, P = .001). No statistical difference was noted in the placebo group.

CONCLUSION

Peripheral muscle microcirculation as assessed by NIRS is impaired in patients with CHF. This impairment is partially reversed by infusion of inotropic agents in patients with ESCHF.

Use of a flow-mediated vasodilation technique to assess endothelial function in dogs

OBJECTIVE

To develop and assess the reproducibility of a protocol to noninvasively test endothelial function in dogs on the basis of the flow-mediated vasodilation (FMD) procedure used in humans.

ANIMALS

5 healthy spayed female dogs.

PROCEDURES

Luminal arterial diameter and blood flow velocity in the brachial and femoral arteries were measured with ultrasonography. The within-dog reproducibility of these ultrasonographic measurements was tested. An occlusion period of 1, 3, or 5 minutes with an inflatable cuff was used to create the FMD response. Measurements made at 15, 30, and 60 seconds following release of the occlusion were compared with measurements made immediately prior to each occlusion to assess the FMD response.

RESULTS

Within-dog reproducibility of measurements revealed moderate to high correlations. Change from baseline in luminal arterial diameter was most substantial when measured at 30 seconds following release of occlusion, whereas blood flow velocity changes were maximal when measured at 15 seconds following release. The brachial imaging site provided a larger number of significant FMD responses than the femoral site. The 3-minute occlusion period provided equal or better responses than the 5-minute occlusion period.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonographic measurement of the FMD responses was a feasible and reproducible technique and significant changes from baseline were detected. The FMD responses in dogs were most substantial when performed at the brachial artery with blood flow velocity and luminal arterial diameter changes from baseline measured at 15 and 30 seconds, respectively, following release of a 3-minute occlusion period.