Retrograde flow components in the brachial artery. A new hemodynamic index.

Arm elevation induces diastolic retrograde flow in the brachial artery and an incremental rise in arterial compliance in healthy subjects with no modifications in vascular resistance. In contrast, changes in resistance have been observed after handgrip exercise. Our objective was to investigate if the resistance change induced by isometric handgrip exercise is able to reverse diastolic retrograde flow induced by arm elevation in a healthy population and to explore these adaptive changes in hypertensive subjects. Arterial flow velocity Doppler measurements were obtained including: (a) a baseline measurement, (b) measurement 30 s after arm elevation, (c) measurement during handgrip maneuver with the arm elevated, (d) measurement during handgrip release with the arm elevated. Our findings showed that diastolic retrograde flow is induced by arm elevation, partially increased by arm-up handgrip and completely reversed during arm-up handgrip release both in healthy and hypertensive subjects. As compared with normal subjects, deceleration time was longer in the hypertensive subjects during baseline but not during the arm-up stage, handgrip contraction and handgrip release stages. An important increase in deceleration time values from baseline to arm-up and handgrip contraction stages was observed in normal subjects but not in the hypertensive group. We believe that the highly significant difference in reactivity to postural changes observed in deceleration time values constitutes a promising hemodynamic index to investigate. Also, our observation of complete reversal of the retrograde flow during arm-up handgrip release provides a new approach to postural and exercise-induced vasomotor responses.

Diastolic retrograde arterial flow and biphasic abdominal aortic Doppler wave pattern: an early sign of arterial wall deterioration?

Many authors have found that diastolic retrograde arterial flow is associated with increased stiffness of the arterial wall. Most of the studies were based in femoral or brachial artery examination. As the abdominal aorta is a large vessel routinely explored in abdominal ultrasound scans, we decided to study whether it could be useful for early identification of abnormalities of the arterial wall. Sixteen young and 16 old, healthy patients matched for sex, weight and height were studied using pulsed Doppler at the level of the abdominal aortic bifurcation. Different hemodynamic factors were measured and compared to establish the systolic and diastolic function of this artery. Triphasic wave pattern was present in 14 of 16 patients in the younger group and only in 4 of 16 in the older group. In addition, diastolic retrograde arterial flow duration and retrograde components of diastolic phase were more prominent in the advanced age group. Increased retrograde flow and incapacity to impulse arterial flow forward during diastolic time are early markers of vascular wall deterioration that can be observed easily in the abdominal aorta during routine abdominal ultrasound scans.

Pulsed Doppler in simulated compartment syndrome: a pilot study to record hemodynamic compromise.

BACKGROUND: Acute compartment syndrome occurs when the tissue pressure within a closed muscle compartment exceeds the perfusion pressure. We observed diastolic retrograde arterial flow (DRAF) in 2 patients in the arteries proximal to compartment syndromes in injured limbs. We hypothesized that DRAF may represent an early sign of compartment pressure increments. METHODS: We mimicked compartment syndrome by using a cuff to produce external compression of the forearm at increasing pressures. We correlated the applied pressure with brachial artery blood flow, velocities, and retrograde flow. We studied the brachial artery at baseline, at external compression of 40 mmHg applied to the forearm, at forearm compression equal to the patient's diastolic blood pressure (DBP), and at forearm compression equal to the patient's mean arterial pressure (MAP). Evaluations included Doppler velocities and DRAF percentage (%). Using a ROC analysis, we selected a DRAF (%) cutoff value for the identification of patients with an applied external pressure equal to or greater than their DBP and calculated its sensitivity and specificity. RESULTS: Compared with baseline, DRAF (%) was increased at 40 mmHg (P<0.05), at DBP (P<0.05), and at MAP (P<0.05). DRAF (%) was strongly correlated with applied external pressure (r=0.92, r(2)=0.85). DRAF 40% presented a 100% sensitivity and a 93% specificity for identifying a compression equal to or greater than the patient's DBP. CONCLUSION: DRAF (%) strongly correlates with the degree of external pressure applied to the brachial artery, suggesting it may represent a useful tool in the detection and evaluation of compartment syndrome.