Catecholamine-induced cardiomyopathy.

OBJECTIVE: To review the pathogenesis as well as the clinical and laboratory features of catecholamine-induced cardiomyopathy associated with pheochromocytoma and other disorders and discuss the various treatment options available. METHODS: Materials used for this article were identified through MEDLINE, PubMed, and Google Scholar searches of the relevant literature from 1955 to the present. RESULTS: Catecholamines and their oxidation products cause a direct toxic effect on the myocardium. Catecholamines also exert a receptor-mediated effect on the myocardium. Catecholamine-mediated myocardial stunning has been implicated in the pathogenesis of stress-induced cardiomyopathy. Biopsy of the myocardium in patients with pheochromocytoma or those with stress-induced cardiomyopathy shows similar pathologic findings. The clinical features in pheochromocytoma-related cardiomyopathy include hypertension, dilated or hypertrophic cardiomyopathy, pulmonary edema due to cardiogenic and noncardiogenic factors, cardiac arrhythmias, and even cardiac arrest. Stress-related cardiomyopathy such as takotsubo cardiomyopathy occurs primarily in postmenopausal women. These patients may present with clinical features suggestive of an acute myocardial infarction or a hemodynamically compromised state. The definitive management of cardiomyopathy associated with pheochromocytoma includes medical treatment with alpha-adrenergic blockade, possibly along with angiotensin converting enzyme blockers and beta1-adrenergic receptor blockers, followed by excision of the tumor. Stress-induced cardiomyopathy is usually self-limiting; patients may require support with nonadrenergic inotropes. CONCLUSION: Recognition of catecholamine-induced cardiomyopathy, especially in patients with pheochromocytoma, before surgical treatment is important to minimize morbidity and mortality.

Phosphoinositide turnover in human platelets is stimulated by albumin.

The effect of human serum albumin (HSA) on the hydrolysis of phosphatidylinositides in human platelets labeled with myo(3H)inositol was studied. Incubation of platelets with HSA (4 gm/dl) for 10 seconds increased IP2, and IP3, by 169% and 217% respectively. 93% of IP3 accumulated within the first 10 seconds. This effect was also shared by bovine serum albumin, although no changes in IP3 levels occurred with ovalbumin. All albumin species used induced 45Ca+2 release from platelets irrespective of its effect on IP3 accumulation. These findings indicate that albumin may function in biological systems by inducing intracellular signaling.

Pituitary and peripheral hormone responses to T3 administration during Antarctic residence.

Very little is known regarding hormonal adaptation in human subjects who are exposed to the extremes of temperature and light that are found in polar latitudes. We have previously reported a 50% elevation in the serum thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH), a fall in serum total triiodothyronine (T3) and free T3 (fT3), and no change in serum total thyroxine (T4) or free T4 (fT4) after 42 wk of Antarctic cold exposure. To differentiate between central and peripheral mechanisms that may lead to these changes, we report the effect of sequentially increasing oral doses of T3 (Cytomel) on serum T3 and fT3 levels and on the resultant attenuation of the TSH response to TRH in nine men before, during, and after 42 wk residence in Antarctica. Serum T3 values basally and following the administration of 25, 50, and 75 micrograms/day of T3 were lower after 42 wk of cold exposure (151 +/- 4, 160 +/- 8, 189 +/- 10, and 222 +/- 14 ng/dl, respectively, compared with control values of 160 +/- 7, 178 +/- 7, 202 +/- 9, and 251 +/- 19 ng/dl, respectively, P less than 0.05). Likewise, the fT3 values measured after these three increasing T3 doses were also lower after 42 wk of cold exposure. The pituitary response to TRH was attenuated by each T3 regimen (48 +/- 6, 68 +/- 4, and 77 +/- 4% decreases in the control period), and this suppression was not different after 20 and 42 wk of Antarctic residence.(ABSTRACT TRUNCATED AT 250 WORDS)