Skin blood flow pattern in burns outcomes.

Functional microcirculatory aspects of burned sites were examined including areas of self-healed burns, and grafted areas. Donor areas were also examined. In 10 patients with burns in the lower limbs, both self-healed and with grafts, the microcirculatory response was evaluated by Laser Doppler flowmetry (LDF) measuring for each site the resting flux at 36 degrees, the postural venular-arteriolar reflex (VAR) and the flux at 41 degrees (heating). The first evaluation was carried out on discharge, and subsequently at approximately 45 day intervals during uniform therapy follow-up (elastocompression). The burn-affected area (self-healed, graft) and those donor areas present should increase resting flux by comparison with control areas. This was particularly so in the self-healed burn, which does however tend to converge in time towards control values. Response to stress tests (VAR and heating) presents percentage variations similar to normal skin in the various areas, with the exception of the grafted areas which present a reduced response in the 1st weeks following engraftment. No significant differences in response to heating were detected. It can be suggested that these differences are due to anatomic variations in revascularization and healing in the different areas as well as to alterations in microvascular innervation and local response to vasoactive substances.

Coronary vasodilator capacity and epicardial vessel remodeling in physiological and hypertensive hypertrophy.

The aim of this study was to compare resting coronary flow velocity, determinants of myocardial oxygen demand, and coronary vasodilator capacity in subjects with physiological, exercise-induced, and hypertensive left ventricular hypertrophy. Sixteen healthy sedentary men, 16 endurance athletes, and 16 hypertensive subjects (mean+/-SEM for left ventricular mass index: 94.9+/-5.5, 184.6+/-8.4, 154.4+/-9.5 g/m(2), respectively) were studied by transesophageal and transthoracic Doppler echocardiography. Coronary flow velocity in left anterior descending artery and cross-sectional area of left main artery were assessed at rest and during dipyridamole-induced vasodilation. Myocardial oxygen demand was estimated through rate-pressure product, left ventricular wall stress, and inotropic function. Coronary flow reserve and minimum coronary resistance were comparable to those of sedentary men in athletes (mean+/-SEM: 3. 23+/-0.16 versus 3.60+/-0.18 and 0.96+/-0.06 versus 1.04+/-0.04 mm Hg. s. cm(-1)), while in hypertensive subjects they were decreased and increased, respectively (mean+/-SEM: 2.31+/-0.08 and 1.21+/-0.10 mm Hg. s. cm(-1); P:<0.05 for both). Resting flow velocity was directly related to rate-pressure product in sedentary men and athletes and also to wall stress in athletes, while these correlations were absent in hypertensives. Dilation of left main artery after dipyridamole was significantly higher in athletes than in sedentary men and hypertensive subjects (mean+/-SEM for area change: 32.9+/-3.7% versus 12.8+/-2.5% and 6.4+/-3.3%; P:<0.05 and 0.01). These data indicate that vasodilator capacity of coronary microcirculation is not impaired in athletes with physiological hypertrophy, in contrast to hypertensive patients. The relationship between resting flow velocity and determinants of oxygen demand is preserved in physiological hypertrophy but missing in hypertensive hypertrophy. Furthermore, the vasodilator capacity of coronary macrocirculation is also enhanced in exercise-trained subjects.

Early impairment of coronary flow reserve and increase in minimum coronary resistance in borderline hypertensive patients.

OBJECTIVE: To evaluate relations between coronary flow velocity and myocardial oxygen demand at rest, as well as coronary vasodilator capacity and flow reserve, in asymptomatic subjects with borderline hypertension as compared to normotensive controls and patients with sustained high blood pressure (HBP) and without left ventricular hypertrophy (LVH). SUBJECTS AND METHODS: Forty-two asymptomatic males were studied: 13 healthy normotensive volunteers; 12 subjects with borderline HBP and 17 asymptomatic subjects with sustained systemic hypertension. Coronary flow velocity in left anterior descending artery and coronary flow reserve were assessed by transesophageal echo-doppler at baseline and during intravenous adenosine infusion. Left ventricular mass, peak systolic wall stress (PSWS; Pa), and midwall fractional shortening (MFS; %) were obtained from M-mode images of the left ventricle in transthoracic long-axis view and in transesophageal transgastric view. RESULTS: Coronary flow velocity at baseline was not significantly different in the three groups, despite significantly higher rate-pressure product (RPP) in the hypertensive groups as compared with controls. Only in control subjects, was resting coronary flow velocity significantly correlated with RPP (y = 4279 + 200x, r = + 0.58, P < 0.05) and PSWS (y = 17.2 + 5.1 x, r = + 0.62, P < 0.05). Coronary reserve was 3.5 +/- 0.65 in controls and significantly lower (P < 0.05) in borderline hypertensive (2.87 +/- 0.46) and in sustained hypertensive subjects (2.66 +/- 0.56). Minimum coronary resistance was significantly increased in both hypertensive groups (1.30 +/- 0.29 and 1.39 +/- 0.48 mmHg/s per cm) as compared to normotensive controls (0.93 +/- 0.20 mmHg/s per cm, P < 0.01). CONCLUSIONS: In asymptomatic subjects with borderline hypertension and without LVH, a significant reduction in coronary flow reserve is already detectable and appears almost entirely related to an impaired coronary vasodilator capacity rather than to an increased myocardial oxygen demand.

Homogeneously reduced versus regionally impaired myocardial blood flow in hypertensive patients: two different patterns of myocardial perfusion associated with degree of hypertrophy.

OBJECTIVES: The aim of this study was to quantitatively measure regional and global myocardial blood flow and coronary reserve in hypertensive patients without coronary artery disease and to assess the correlation with left ventricular mass. BACKGROUND: The effect of left ventricular hypertrophy on regional vasodilating coronary capability in arterial hypertension is controversial, and no quantitative method has been applied to assess a possible correlation. METHODS: Positron emission tomography was performed in 50 untreated hypertensive patients and 13 normotensive subjects. Blood flow at baseline and after dipyridamole was globally and regionally measured by using nitrogen-13 ammonia; coronary reserve and resistance were calculated. Left ventricular mass was assessed by two-dimensional echocardiography. RESULTS: In hypertensive patients, flow at baseline was similar to that of normotensive subjects (p = 0.21), but values were reduced after pharmacologic vasodilation (p < 0.05). This impairment of maximal coronary flow was not correlated with left ventricular mass (p = 0.13). Among hypertensive patients, we identified a group with a homogeneous distribution of perfusion and a group with a heterogeneous flow pattern. Flow was globally reduced in the former group, but it was abnormal only at the site of perfusion defects in the latter. Patients with regional defects showed the highest likelihood of having an increased left ventricular mass. CONCLUSIONS: In arterial hypertension, left ventricular mass is not correlated with global myocardial blood flow. Nevertheless, patients with ventricular hypertrophy are likely to show a heterogeneous flow pattern with regional defects and almost normal blood flow in nonaffected regions. In hypertensive patients with a homogeneous perfusion pattern during stress, myocardial blood flow frequently shows a diffuse reduction.

Assessment of coronary reserve by transoesophageal Doppler echocardiography. Direct comparison between different modalities of dipyridamole and adenosine administration.

BACKGROUND: This study was undertaken to compare the coronary vasodilator response to different application modalities of intravenous vasodilators, in order to identify the optimal pharmacological protocol for the evaluation of coronary reserve by means of transoesophageal Doppler echocardiography. METHODS: Blood flow velocity in the left anterior descending artery, coronary vascular resistance and left main coronary artery cross-sectional area were assessed by transoesophageal echo-Doppler during an i.v. adenosine bolus (5 mg), a 5-min adenosine infusion (infusion rate 140 micrograms. kg-1 min-1), and low (0.56 mg.kg-1. 4 min-1), and high-dose (0.84 mg.kg-1.9 min-1) dipyridamole infusions in 10 healthy normals (Group 1) and in 20 patients (Group 2) with either coronary microvascular disease (11 patients) or coronary artery disease (nine patients). RESULTS: In both groups, the highest flow velocity and the lowest coronary vascular resistance were observed during the adenosine infusion. Flow velocity values and indices of coronary vasodilator capacity observed after the adenosine bolus and the high-dose dipyridamole infusion were very close to those obtained during the adenosine infusion, especially in Group 1. Coronary flow velocity was lower and coronary vascular resistance higher after low-dose dipyridamole, significantly in Group 2. The maximal flow response to the adenosine bolus was observed within a few seconds after the injection, and was very short. The peak response to the adenosine infusion was observed 57 +/- 27 s after its start. The coronary flow velocity response to dipyridamole was dose dependent and differed between Groups 1 and 2. CONCLUSION: In combination with transoesophageal Doppler echocardiography, a short-lasting adenosine infusion at a rate of 140 micrograms.kg-1.min-1 seems to be preferable to an adenosine bolus and dipyridamole infusion. The effect of the bolus is too short for an accurate measurement of coronary flow velocity, while the dipyridamole infusion, especially at a low dose, induces a submaximal vasodilator response.