Nagib S Dahdah

Normal values and methodologic recommendations for signal-averaged electrocardiography in children and adolescents.

Signal-averaged electrocardiography was performed in 153 normal children and adolescents (1 day to 18.3 years old) to examine the effects of age, sex, and race on different electrocardiographic variables, and to evaluate whether the current methods for analysis of the signal-averaged electrocardiogram are applicable to small children. Tracing with inaccurate automatic determination of the QRS end point or high noise levels were excluded. Filtered QRS duration, root-mean-square voltage, and low-amplitude signal duration were measured using 25, 40, and 80 Hz filters. All variables were significantly different (p <0.01) in infants compared with subjects aged >15 years. These differences gradually resolved with increasing age. Sex differences were present for some variables in adolescents only, and there was no significant race-related difference. Because of the shorter QRS duration, the terminal activities were more accurately reflected at the terminal duration of 30 ms in infants and 35 ms in children aged at least 1 year to <6 years. Normative data for filtered QRS duration, root-mean-square voltage, and low-amplitude signal duration are provided for different age groups.

A National Survey on the Pediatric Cardiologist's Clinical Approach for Patients with Kawasaki Disease

In 1994, the American Heart Association (AHA) published the most recent guidelines for long-term cardiovascular management of Kawasaki disease. Since then, recent publications have shed new light on different diagnostic, prognostic, and management issues. We sought the opinion of pediatric cardiologists practicing in U.S. fellowship programs on the subject by means of a multiple-choice survey. Two questions addressed therapy in the acute phase, each preceded by a statement from related literature. Ten duplicate questions addressed the long-term cardiovascular management in five sets of paired questions; each question was first given in reminiscence of a clinical situation and then preceded by a statement from particular publications representative of new information that has become available since the publication of the 1994 AHA guidelines. All questions were provided in the same mailing. Replies were received from 97 participants practicing at 29 institutions. For the acute illness, 21% of respondents do not use high-dose aspirin, and 50% support reassessment of current guidelines. Universal intravenous immune globulin (IVIG) administration is followed by 97%, among whom 20% agree that evaluation of selection criteria is needed. For long-term management, 60–75% advocate regular follow-up of risk level I patients, and 80% favor periodic follow-up, with stress imaging (34–40%), for risk level II. For risk level IV more respondents favor stress echocardiography as opposed to nuclear imaging, in consonance with recent literature. For risk levels III and IV, 36–40% perform coronary angiography on a regular basis, whereas 60% do so when coronary symptoms are present or when stress imaging suggests myocardial ischemia. Finally, 19–25% of respondents do not routinely advise healthy lifestyle to patients free of coronary artery lesions. In conclusion, the guidelines for conventional therapy in the acute phase and long-term cardiovascular management need to be revised.

Endothelial Dysfunction in Cerebral Microcirculation During Hypothermic Cardiopulmonary Bypass in Newborn Lambs † 1908

OBJECTIVES Inflammatory stimuli or mechanical stresses associated with hypothermic cardiopulmonary bypass could potentially impair cerebrovascular function, resulting in inadequate cerebral perfusion. We hypothesize that hypothermic cardiopulmonary bypass is associated with endothelial or vascular smooth muscle dysfunction and associated cerebral hypoperfusion. Therefore we studied the cerebrovascular response to endothelium-dependent vasodilator, acetylcholine, endothelium-independent nitric oxide donor, sodium nitroprusside, and vasoactive amine, serotonin, in newborn lambs undergoing hypothermic cardiopulmonary bypass (nasopharygeal temperature = 18 degrees C). METHODS Studies were performed on 13 newborn lambs equipped with a closed cranial window, allowing for direct visualization of surface pial arterioles. Six animals were studied while undergoing hypothermic cardiopulmonary bypass, whereas seven served as nonbypass, warm (37 degrees C) controls. Pial arteriolar caliber (range = 111 to 316 microm diameter) was monitored using video microscopy. RESULTS Topical application of acetylcholine caused a dose-dependent increase in arteriolar diameter in the control group that was absent in animals undergoing hypothermic cardiopulmonary bypass. Hypothermic cardiopulmonary bypass did not alter the vasodilation in response to sodium nitroprusside. Furthermore, the contractile response to serotonin was fully expressed during hypothermic cardiopulmonary bypass. CONCLUSIONS The specific loss of acetylcholine-induced vasodilation suggests endothelial cell dysfunction rather than impaired ability of vascular smooth muscle to respond to nitric oxide. It is speculated that loss of endothelium-dependent regulatory factors in the cerebral microcirculation during hypothermic cardiopulmonary bypass may enhance vasoconstriction, and impaired cerebrovascular function may be a basis for associated neurologic injury during or after hypothermic cardiopulmonary bypass.

Contractile Response of Isolated Newborn Lamb Coronary vessels Exposed to Profound Hypothermia and Anoxia: The Protective Role of Hypothermosol, a New Preservation Medium 97

Contractile Response of Isolated Newborn Lamb Coronary vessels Exposed to Profound Hypothermia and Anoxia: The Protective Role of Hypothermosol, a New Preservation Medium 97

Effect of Ultraprofound Hypothermia on the ex vivo Contractile Response of Cerebral Arteries: Relevance to Cerebrovascular Dysfunction during Cardiopulmonary Bypass • 238

Effect of Ultraprofound Hypothermia on the ex vivo Contractile Response of Cerebral Arteries: Relevance to Cerebrovascular Dysfunction during Cardiopulmonary Bypass • 238

Cold-induced protein tyrosine phosphorylation in cerebral arteries of newborn lambs: a mechanism of cold-induced contraction • 1177

Cold-induced protein tyrosine phosphorylation in cerebral arteries of newborn lambs: a mechanism of cold-induced contraction • 1177

Cold-Induced Contraction of Newborn Lamb Cerebral Arteries: Role of Na+,K+-ATPase and Ca2+-ATPase in the Potentiation by Sodium Orthovanadate |[dagger]| 358

Cold-Induced Contraction of Newborn Lamb Cerebral Arteries: Role of Na + ,K + -ATPase and Ca 2+ -ATPase in the Potentiation by Sodium Orthovanadate † 358