Overweight and sympathetic overactivity in black Americans.

A large body of clinical investigation implicates an important role for the sympathetic nervous system in linking obesity with hypertension. However, the experimental support for this hypothesis is derived from strictly white cohorts. The goal of this study was to determine whether being overweight begets sympathetic overactivity in black Americans, the ethnic minority at highest risk for hypertension. We recorded postganglionic sympathetic nerve discharge with microelectrodes in muscle nerve fascicles of the peroneal nerve in 92 normotensive young adult black men and women within a wide range of body mass index. The same experiments were performed in a control group of 45 normotensive white men and women of similar ages and body mass indices. The major new findings are 2-fold. First, in young, normotensive, overtly healthy black women, being overweight begets sympathetic overactivity (r=0.45, P=0.0009), a putative intermediate phenotype for incident hypertension. Second, in black men, sympathetic nerve discharge is dissociated from body mass index (r=0.03, P=NS). This dissociation is explained in part by a 20% to 40% higher rate of sympathetic nerve discharge in lean black men compared with lean white men and lean black and white women (28+/-3 versus 18+/-2, 21+/-2, and 17+/-2 bursts/min, respectively; P<0.05). Sympathetic nerve discharge in lean black men is comparable to that of overweight black men and women as well as white men and women. These data provide the first microneurographic evidence for tonic central sympathetic overactivity in blacks, both adiposity-related sympathetic overactivity in black women and adiposity-independent sympathetic overactivity in black men.

Transdermal estrogen replacement therapy decreases sympathetic activity in postmenopausal women.

BACKGROUND: Menopause heralds a dramatic increase in incident hypertension, suggesting a protective effect of estrogen on blood pressure (BP). In female rats, estrogen has been shown to decrease sympathetic nerve discharge (SND) and BP. SND, however, has not been recorded during estrogen replacement therapy (ERT) in humans. Methods and Results-In 12 normotensive postmenopausal women, we conducted a randomized crossover placebo-controlled study to test whether chronic ERT caused a sustained decrease in SND and BP. Twenty-four-hour ambulatory BP, SND, and arterial baroreflex sensitivity were measured before and after 8 weeks of transdermal estradiol (200 microgram/d), oral conjugated estrogens (0.625 mg/d), or placebo. To test the acute effects of estrogen on SND, additional studies were performed in the same women receiving intravenous conjugated estrogens or sublingual estradiol. After 8 weeks of transdermal ERT, the basal rate of SND decreased by 30% (from 40+/-4 to 27+/-4 bursts per minute, P=0.0001) and ambulatory diastolic BP fell by 5+/-2 mm Hg (P=0.0003). In contrast, SND and BP were unaffected either by 8 weeks of oral ERT or by acute estrogen administration. Neither transdermal nor oral ERT had any effects on baroreflex sensitivity. CONCLUSIONS: In normotensive postmenopausal women, chronic transdermal ERT decreases SND without augmenting arterial baroreflexes and causes a small but statistically significant decrease in ambulatory BP. Sympathetic inhibition is evident only with chronic rather than acute estrogen administration, implying a genomic mechanism of action. Because the effects of transdermal ERT are larger than those of oral ERT, the route of administration may be an important consideration in optimizing the beneficial effects of ERT on BP and overall cardiovascular health.

Cocaine stimulates the human cardiovascular system via a central mechanism of action.

BACKGROUND: Cocaine is thought to stimulate the cardiovascular system by blocking peripheral norepinephrine reuptake. This study was designed to test the novel hypotheses that cocaine also stimulates the human cardiovascular system by (1) increasing central sympathetic outflow, or (2) decreasing parasympathetic control of heart rate. METHODS AND RESULTS: In 14 healthy cocaine-naive humans, we measured blood pressure, heart rate, and skin sympathetic nerve activity (SNA) with intraneural microelectrodes before, during, and for 90 minutes after intranasal cocaine (2 mg/kg, n=7) or lidocaine (2 mg/kg, n=7). Intranasal cocaine caused an initial but transient 3. 3-fold increase in skin SNA during the period of intranasal administration followed by a sustained 2.4-fold increase lasting for up to 90 minutes after cocaine. Unlike cocaine, intranasal lidocaine caused only a small transient increase in skin SNA due to local nasal irritation. The cocaine-induced increase in SNA was accompanied by decreased skin blood flow, increased skin vascular resistance, and increased heart rate. In 11 additional subjects, we showed that the cocaine-induced increase in heart rate was eliminated by beta-adrenergic receptor blockade (propranolol) but unaffected by muscarinic receptor blockade (atropine), indicating sympathetic mediation. CONCLUSIONS: These studies provide direct microneurographic evidence in humans that intranasal cocaine stimulates central sympathetic outflow. This central sympathetic activation appears to be targeted not only to the cutaneous circulation promoting peripheral vasoconstriction but also to the heart promoting tachycardia.

The Eisenmenger syndrome in adults.

For this article, the literature on the pathophysiology, clinical features, natural history, prognosis, and management of the Eisenmenger syndrome in adults was reviewed. English-language articles from 1966 to the present were identified through a search of the MEDLINE database by using the terms Eisenmenger, congenital heart disease, and pulmonary hypertension. Selected cross-referenced articles were also included. Articles on the pathophysiology, clinical presentation, evaluation, natural history, complications, and treatment of the Eisenmenger syndrome in adults were selected, and descriptive and analytical data relevant to the practicing physician were manually extracted. The Eisenmenger syndrome is characterized by elevated pulmonary vascular resistance and right-to-left shunting of blood through a systemic-to-pulmonary circulation connection. Most patients with the syndrome survive for 20 to 30 years. The hemostatic changes associated with the syndrome may lead to thromboembolic events, cerebrovascular complications, or the hyperviscosity syndrome. Erythrocytosis is present in most patients, but excessive phlebotomy may cause microcytosis and exacerbate the symptoms of hyperviscosity. Other complications associated with the Eisenmenger syndrome include hemoptysis, gout, cholelithiasis, hypertrophic osteoarthropathy, and decreased renal function. Pregnancy or noncardiac surgery is associated with a high mortality rate in patients with the Eisenmenger syndrome. Because most pediatric patients with the Eisenmenger syndrome survive to adulthood, primary care physicians should have a thorough understanding of the syndrome; its associated complications; and medical and surgical management, especially with regard to the appropriate timing of phlebotomy and lung or heart-lung transplantation. In addition, patients with the syndrome should undergo routine follow-up at a tertiary care center that has physicians and nurses with special expertise in congenital heart disease. In patients with the Eisenmenger syndrome who are pregnant or require noncardiac surgery, a multidisciplinary approach should be used to reduce the excessive mortality associated with these conditions.

Effects of the intracoronary infusion of cocaine on left ventricular systolic and diastolic function in humans.

BACKGROUND: In dogs, a large amount of intravenous cocaine causes a profound deterioration of left ventricular (LV) systolic function and an increase in LV end-diastolic pressure. This study was done to assess the influence of a high intracoronary cocaine concentration on LV systolic and diastolic function in humans. METHODS AND RESULTS: In 20 patients (14 men and 6 women aged 39 to 72 years) referred for cardiac catheterization for the evaluation of chest pain, we measured heart rate, systemic arterial pressure, LV pressure and its first derivative (dP/dt), and LV volumes and ejection fraction before and during the final 2 to 3 minutes of a 15-minute intracoronary infusion of saline (n=10, control subjects) or cocaine hydrochloride 1 mg/min (n=10). No variable changed with saline. With cocaine, the drug concentration in blood obtained from the coronary sinus was 3.0+/-0.4 (mean+/-SD) mg/L, similar in magnitude to the blood cocaine concentration reported in abusers dying of cocaine intoxication. Cocaine induced no significant change in heart rate, LV dP/dt (positive or negative), or LV end-diastolic volume, but it caused an increase in systolic and mean arterial pressures, LV end-diastolic pressure, and LV end-systolic volume, as well as a decrease in LV ejection fraction. CONCLUSIONS: In humans, the intracoronary infusion of cocaine sufficient in amount to achieve a high drug concentration in coronary sinus blood causes a deterioration of LV systolic and diastolic performance.

Usefulness of transesophageal echocardiography in determining the source of emboli in patients with acute limb ischemia.

A potential cardiovascular source of embolism was demonstrated by transesophageal echocardiography in 20 of 33 patients (61%) with acute limb ischemia. The percentage was higher in patients with large artery occlusions (9 of 11, 82%) than in those with small artery occlusions (9 of 22, 41%) (p = 0.026).

Comparison of cocaine-induced vasoconstriction of left and right coronary arterial systems.

In patients undergoing cardiac catheterization, we measured left and right coronary arterial dimensions before and 15 minutes after intranasal saline (n = 8) or cocaine (n = 8). In response to cocaine, left and right coronary arterial areas declined by 11 +/- 6% and 12 +/- 11%, respectively; thus, intranasal cocaine induces a similar magnitude of vasoconstriction of the left and right coronary arteries.