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Endothelium-derived relaxing factor
LITERATURE REVIEW
on right ventricular function. Pulsatile and nonpulsatile components interact to produce the hydraulic load with the contribution by pulsatile components (elastance and wave reflectance) increasing substantially in pulmonary hypertension. However, the failure to produce clinical improvement in pulmonary vascular resistance with vasodilators may result from inaccurate monitoring of the pulmonary circulation. The use of calculated pulmonary vascular resistance (mean pulmonary artery pressure - mean left atrial pressure/ pulmonary blood flow) is relevant only when left atrial pressure is the downstream pressure. When critical closing pressure (the pressure intercept at zero flow on the pulmonary pressure/flow curve) exceeds left atrial pressure, it is the appropriate downstream pressure. The failure to use pressure/flow curves and appropriate downstream pressure in documenting reductions in pulmonary resistance accounts for the clinical lack of success from pharmacologic therapy.
Murray DP, Salih M, Tan LB, et ah Which exercise test variables are of prognostic importance post-myocardial infarction? Int J Cardiol 2 0 : 3 5 3 - 3 6 3 , 1988 The aim of pre-discharge exercise testing is to identify patients whose prognosis is guarded due to myocardium at risk for infarction. Such patients might benefit from betaadrenergic blockade, percutaneous transluminal coronary angioplasty, or coronary bypass grafting. In 300 patients nine days after myocardial infarction, 158 had ST-segment depression during exercise. Angina, need for cardiac surgery, heart failure, and recurrent myocardial infarction were all more common in patients with exercise-induced ST-segment depression. ST-segment depression was a more sensitive indicator of subsequent cardiac events than angina. Abnormal blood pressure responses to exercise were also associated with subsequent heart failure and angina. The combination of abnormal blood pressure response to exercise, limited exercise tolerance, or angina increased the prognostic implications of ST-segment depression. Duration of exercise of less than six minutes was significantly associated with subsequent cardiac events. Exercise-induced ST-segment elevation over the site of infarction was unassociated with subsequent cardiac events, a result possibly explained by the routine administration of beta-blockers.
Griffith TM, Lewis M J, Newby AC, et al: Endothelium-derived relaxing factor. J Am Coil Cardiol 12:797-806, 1988 Vascular endothelium releases endothelium-derived contracting factors, endothelium-derived hyperpolarizing factor, and endothelium-derived relaxing factor (EDRF). EDRF is probably either nitric oxide ora ready source of it. It is released continuously in the basal state, and its release is stimulated by adenosine diphosphate and triphosphate, acetylcholine, bradykinin, norepinephrine, and other substances. EDRF stimulates soluble guanylate cyclase to increase cyclic guanosine monophosphate causing vascular relaxant and platelet antiaggregatory effects. EDRF activity is reduced in atheroselerosis and aging. Coordination of vasomotor activity within the vascular
243
bed is modulated by flow-related EDRF activity. Basal EDRF activity is greatest in resistance vessels. Impairment or inhibition of EDRF may be involved in coronary vasospasm and cerebral vasoconstriction.
Luisiri A, Graviss ER, Weber T, et al: Neurosonographic changes in newborns treated with extracorporeal membrane oxygenation. J Ultrasound Med 7:429-438, 1988 Extracorporeal membrane oxygenation (ECMO) successfully treats newborns with intractable respiratory distress syndrome. However, bleeding, including intracranial hemorrhage, remains one of the serious complications of such therapy. Cannulation for ECMO is via the internal jugular vein and common carotid artery. In this study of 40 near-term neonates receiving ECMO, 10 developed abnormal neurosonograms. Patterns associated with ECMO therapy included: (1) Diffuse focal echogenic areas of hypoxia-ischemia resulting from cerebral edema, large vessel infarction, or periventricular leukomalacia; and (2) Hyperechoic areas of intracranial hemorrhage. Two infants developed intracranial hemorrhage, a lower incidence than in other series, probably because of the older gestational age of the patients. Ischemic changes, seen in nine infants, are more common in older gestational age and higher birth weight infants. Right cerebral arterial infarction was not observed despite ligation of the common carotid artery. Only 3 of the 10 infants survived, all with neurologic deficits. Observation of abnormal neurosonograms requires reassessment of capability for weaning from ECMO.
Varnauskas E, European Coronary Surgery Study Group: Twelve-year followup of survival in the randomized European coronary surgery study. N Engl J Med 319:332-337, 1988 Numerous multicenter long-term studies have attempted to determine the efficacy of coronary artery bypass grafting. This study of 767 men with good left ventricular function demonstrated a significantly higher survival rate with surgical therapy than with medical treatment of coronary artery disease (92% v 83%). Thirty-six percent of medically treated patients crossed over to surgical therapy (136 of 373). Benefits of surgical treatment were limited to men younger than 53 years in age, patients with markedly positive exercise tests, subjects with abnormal resting ECG, and patients with left anterior descending coronary artery lesions. Reevaluation of these patients at I 0 to 12 years after initial randomization continued to yield favorable results for surgical treatment, but with marked attenuation of survival compared to the 5-year interval. Explanations for reduced benefit in later years include progression of native coronary disease and new atherosclerotic lesions in vein grafts.
Luscher TF, Diederich D, Siebenmann R, et Difference between endothelium-dependent relaxation in arterial and in venous coronary bypass grafts. N E n g l J M e d 3 1 9 : 4 6 2 - 4 6 7 , 1988 ah
Endothelium-dependent relaxation was studied in internal mammary arteries and saphenous veins from 58
on right ventricular function. Pulsatile and nonpulsatile components interact to produce the hydraulic load with the contribution by pulsatile components (elastance and wave reflectance) increasing substantially in pulmonary hypertension. However, the failure to produce clinical improvement in pulmonary vascular resistance with vasodilators may result from inaccurate monitoring of the pulmonary circulation. The use of calculated pulmonary vascular resistance (mean pulmonary artery pressure - mean left atrial pressure/ pulmonary blood flow) is relevant only when left atrial pressure is the downstream pressure. When critical closing pressure (the pressure intercept at zero flow on the pulmonary pressure/flow curve) exceeds left atrial pressure, it is the appropriate downstream pressure. The failure to use pressure/flow curves and appropriate downstream pressure in documenting reductions in pulmonary resistance accounts for the clinical lack of success from pharmacologic therapy.
Murray DP, Salih M, Tan LB, et ah Which exercise test variables are of prognostic importance post-myocardial infarction? Int J Cardiol 2 0 : 3 5 3 - 3 6 3 , 1988 The aim of pre-discharge exercise testing is to identify patients whose prognosis is guarded due to myocardium at risk for infarction. Such patients might benefit from betaadrenergic blockade, percutaneous transluminal coronary angioplasty, or coronary bypass grafting. In 300 patients nine days after myocardial infarction, 158 had ST-segment depression during exercise. Angina, need for cardiac surgery, heart failure, and recurrent myocardial infarction were all more common in patients with exercise-induced ST-segment depression. ST-segment depression was a more sensitive indicator of subsequent cardiac events than angina. Abnormal blood pressure responses to exercise were also associated with subsequent heart failure and angina. The combination of abnormal blood pressure response to exercise, limited exercise tolerance, or angina increased the prognostic implications of ST-segment depression. Duration of exercise of less than six minutes was significantly associated with subsequent cardiac events. Exercise-induced ST-segment elevation over the site of infarction was unassociated with subsequent cardiac events, a result possibly explained by the routine administration of beta-blockers.
Griffith TM, Lewis M J, Newby AC, et al: Endothelium-derived relaxing factor. J Am Coil Cardiol 12:797-806, 1988 Vascular endothelium releases endothelium-derived contracting factors, endothelium-derived hyperpolarizing factor, and endothelium-derived relaxing factor (EDRF). EDRF is probably either nitric oxide ora ready source of it. It is released continuously in the basal state, and its release is stimulated by adenosine diphosphate and triphosphate, acetylcholine, bradykinin, norepinephrine, and other substances. EDRF stimulates soluble guanylate cyclase to increase cyclic guanosine monophosphate causing vascular relaxant and platelet antiaggregatory effects. EDRF activity is reduced in atheroselerosis and aging. Coordination of vasomotor activity within the vascular
243
bed is modulated by flow-related EDRF activity. Basal EDRF activity is greatest in resistance vessels. Impairment or inhibition of EDRF may be involved in coronary vasospasm and cerebral vasoconstriction.
Luisiri A, Graviss ER, Weber T, et al: Neurosonographic changes in newborns treated with extracorporeal membrane oxygenation. J Ultrasound Med 7:429-438, 1988 Extracorporeal membrane oxygenation (ECMO) successfully treats newborns with intractable respiratory distress syndrome. However, bleeding, including intracranial hemorrhage, remains one of the serious complications of such therapy. Cannulation for ECMO is via the internal jugular vein and common carotid artery. In this study of 40 near-term neonates receiving ECMO, 10 developed abnormal neurosonograms. Patterns associated with ECMO therapy included: (1) Diffuse focal echogenic areas of hypoxia-ischemia resulting from cerebral edema, large vessel infarction, or periventricular leukomalacia; and (2) Hyperechoic areas of intracranial hemorrhage. Two infants developed intracranial hemorrhage, a lower incidence than in other series, probably because of the older gestational age of the patients. Ischemic changes, seen in nine infants, are more common in older gestational age and higher birth weight infants. Right cerebral arterial infarction was not observed despite ligation of the common carotid artery. Only 3 of the 10 infants survived, all with neurologic deficits. Observation of abnormal neurosonograms requires reassessment of capability for weaning from ECMO.
Varnauskas E, European Coronary Surgery Study Group: Twelve-year followup of survival in the randomized European coronary surgery study. N Engl J Med 319:332-337, 1988 Numerous multicenter long-term studies have attempted to determine the efficacy of coronary artery bypass grafting. This study of 767 men with good left ventricular function demonstrated a significantly higher survival rate with surgical therapy than with medical treatment of coronary artery disease (92% v 83%). Thirty-six percent of medically treated patients crossed over to surgical therapy (136 of 373). Benefits of surgical treatment were limited to men younger than 53 years in age, patients with markedly positive exercise tests, subjects with abnormal resting ECG, and patients with left anterior descending coronary artery lesions. Reevaluation of these patients at I 0 to 12 years after initial randomization continued to yield favorable results for surgical treatment, but with marked attenuation of survival compared to the 5-year interval. Explanations for reduced benefit in later years include progression of native coronary disease and new atherosclerotic lesions in vein grafts.
Luscher TF, Diederich D, Siebenmann R, et Difference between endothelium-dependent relaxation in arterial and in venous coronary bypass grafts. N E n g l J M e d 3 1 9 : 4 6 2 - 4 6 7 , 1988 ah
Endothelium-dependent relaxation was studied in internal mammary arteries and saphenous veins from 58