Thrombin receptor expression in normal and atherosclerotic human arteries.

Thrombin is a multifunctional serine protease generated at sites of vascular injury. A host of thrombin actions on vascular endothelial cells, smooth muscle cells, and macrophages has been defined in cell culture systems, but the in vivo significance of these activities is unknown. We have defined the expression of the recently identified receptor for thrombin in human arteries by both in situ hybridization and immunohistochemistry. In normal-appearing arteries, thrombin receptor was expressed almost exclusively in the endothelial layer. By contrast, in human atheroma, the receptor was widely expressed, both in regions rich in macrophages and in regions rich in vascular smooth muscle cells and mesenchymal-appearing intimal cells of unknown origin. Thrombin receptor was expressed by human vascular endothelial cells and smooth muscle cells in culture and by macrophages obtained by bronchioalveolar lavage, thus demonstrating that all three cell types are indeed capable of expressing the thrombin receptor. These results establish thrombin receptor activation as a candidate for contributing to sclerotic and inflammatory processes in the human vasculature, such as those that occur in atherosclerosis and restenosis.

Chronic nitric oxide inhibition in utero produces persistent pulmonary hypertension in newborn lambs.

Persistent pulmonary hypertension of the newborn (PPHN) is associated with chronic intrauterine events. Acute nitric oxide (NO) inhibition attenuates the normal increase in pulmonary blood flow at birth. We investigated whether chronic NO inhibition in utero causes persistent pulmonary hypertension. 11 fetal lambs received either a continuous infusion of N omega-nitro-L-arginine (an NO synthesis inhibitor) or 0.9% saline. Before infusion, acetylcholine (dependent upon endogenous NO production) and sodium nitroprusside (which releases its own NO) produced potent pulmonary vasodilation. After 10.5 +/- 1.5 d of infusion, acetylcholine did not produce pulmonary vasodilation in N omega-nitric-L-arginine-treated fetal lambs, but did in saline-treated fetal lambs; sodium nitroprusside produced pulmonary vasodilation in both groups. Immediately after birth, at 140 d of gestation, during the 3-h study period, mean pulmonary arterial pressure did not decrease in N omega-nitro-L-arginine-treated lambs; the increase in pulmonary blood flow and decrease in pulmonary vascular resistance were markedly attenuated compared to saline-treated lambs. These hemodynamic derangements were reversed by L-arginine. There were no anatomic abnormalities in the pulmonary circulation. Chronic NO inhibition in utero reproduces many of the physiologic derangements of PPHN. Intrauterine events which result in endothelial dysfunction and inhibition of NO may produce the physiologic derrangements of PPHN.

Ventilation and oxygenation induce endothelial nitric oxide synthase gene expression in the lungs of fetal lambs.

At birth, ventilation and oxygenation immediately decrease pulmonary vascular resistance (PVR) and increase pulmonary blood flow (PBF); more gradual changes occur over the next several hours. Nitric oxide, produced by endothelial nitric oxide synthase (eNOS), mediates these gradual changes. To determine how ventilation and oxygenation affect eNOS gene expression, 12 fetal lambs were ventilated for 8 h without changing fetal descending aortic blood gases or pH (rhythmic distension) or with 100% oxygen (O2 ventilation). Vascular pressures and PBF were measured. Total RNA, protein, and tissue sections were prepared from lung tissue for RNase protection assays, Western blotting, and in situ hybridization. O2 ventilation increased PBF and decreased PVR more than rhythmic distension (P < 0.05). Rhythmic distension increased eNOS mRNA expression; O2 ventilation increased eNOS mRNA expression more and increased eNOS protein expression (P < 0.05). To define the mechanisms responsible for these changes, ovine fetal pulmonary arterial endothelial cells were exposed to 1, 21, or 95% O2 or to shear stress. 95% O2 increased eNOS mRNA and protein expression (P < 0.05). Shear stress increased eNOS mRNA and protein expression (P < 0.05). Increased oxygenation but more importantly increased PBF with increased shear stress induce eNOS gene expression and contribute to pulmonary vasodilation after birth.

A receptor for vascular endothelial growth factor that stimulates endothelial apoptosis.

Vascular endothelial growth factor (VEGF) is a dimeric angiogenic factor that is overexpressed by many tumors and stimulates tumor angiogenesis. VEGF initiates signaling by dimerizing the receptors VEGFR-1 and VEGFR-2. The Fas receptor stimulates apoptosis, and artificial dimerization of the Fas cytoplasmic domain has been shown to induce apoptosis. We constructed a chimeric receptor (VEGFR2Fas) combining the extracellular and transmembrane domains of VEGFR-2 with the cytoplasmic domain of Fas receptor. When VEGFR2Fas was stably expressed in endothelial cells in vitro, treatment with VEGF rapidly induced cell death with features characteristic of Fas-mediated apoptosis. These findings demonstrate that VEGFR2Fas functions as a VEGF-triggered death receptor and raise the possibility that introduction of VEGFR2Fas into tumor endothelium or tumor cells in vivo may convert tumor-derived VEGF from an angiogenic factor into an antiangiogenesis agent.

Heart rate is a marker of amiodarone mortality reduction in severe heart failure. The GESICA-GEMA Investigators. Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiaca en Argentina-Grupo de Estudios Multicéntricos en Argentina.

OBJECTIVES: The impact of amiodarone on mortality in patients with severe congestive heart failure (CHF) (New York Heart Association functional classes II [advanced], III and IV; left ventricular ejection fraction < 35%) In the Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiaca en Argentina (GESICA) trial was analyzed in relation to initial mean baseline heart rate (BHR) and its change after 6 months of follow-up. BACKGROUND: Trials of amiodarone therapy in CHF have produced discordant results, suggesting that the effect is not uniform in all patient subgroups with regard to survival. METHODS: The present analysis was carried out in 516 patients randomized to receive amiodarone, 300 mg/day (n = 260), or nonantiarrhythmic therapy (n = 256, control group) and followed up for 2 years. Survival was evaluated for patients with a BHR > or = 90 beats/min (control: n = 132; amiodarone: n = 122) and < 90 beats/min (control: n = 124; amiodarone: n = 138). Survival was also analyzed according to heart rate reduction at 6 months for 367 patients. RESULTS: For patients with a BHR > or = 90 beats/min, amiodarone therapy reduced mortality to 38.4% compared with 62.4% in control patients (relative risk [RR] 0.55, 95% confidence interval [CI] 0.35 to 0.95, p < 0.002). Both sudden death (RR 0.46, 95% CI 0.24 to 0.90, p < 0.02) and progressive heart failure death (RR 0.60, 95% CI 0.30 to 1.03, p < 0.06) were reduced, and functional capacity was improved. In patients with a BHR < 90 beats/min, amiodarone did not alter survival. Among 367 patients who completed 6 months of follow-up, amiodarone reduced 2-year mortality only in those with a BHR > or = 90 beats/min, which was reduced at 6 months. CONCLUSIONS: Elevated rest heart rates in severe CHF identify a subgroup of patients who benefit from treatment with amiodarone. Amiodarone-induced heart rate slowing may be an important benefit for patients.

Effects of activity on ascending aortic velocity in children with valvar aortic stenosis.

The peak velocity of aortic blood flow was measured in 12 normal children and 20 children with valvar aortic stenosis (AS) by continuous-wave Doppler ultrasound (CWD). Measurements were made at rest, after 2 forms of exercise and, in the 11 children who underwent cardiac catheterization, while under sedation. The exercise was both formal cycle ergometry and a 200-meter jog. The peak velocity in normal children was 1.5 +/- 0.2 m/s at rest, increasing to 2.1 +/- 0.4 m/s (p less than 0.01) after running and to 1.9 +/- 0.4 m/s (p less than 0.01) after cycling. Peak velocity in children with AS was 3.5 +/- 0.8 m/s at rest, increasing to 4.4 +/- 0.8 m/s (p less than 0.01) after running and to 4.5 +/- 0.5 m/s (p less than 0.01) after cycling. The increase in peak velocity was greater in children with AS than in normal children. Measurements of left ventricular (LV) aortic pressure differences by cardiac catheterization were compared to those made by CWD, using the modified Bernoulli equation. The best correlation of the CWD prediction of LV aortic pressure differences was achieved when the children were sedated. The peak velocity of blood flow in the ascending aorta varied with level of activity, and this variability must be considered when using the Bernoulli equation to predict LV aortic pressure differences. CWD prediction of the LV aortic pressure difference was best when the child was sedated (r = 0.98). It is therefore prudent to consider the velocity measurement proximal to the AS to calculate LV aortic pressure differences more accurately unless the child is sedated.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency of family history of acute myocardial infarction in patients with acute myocardial infarction. Argentine FRICAS (Factores de Riesgo Coronario en America del Sur) Investigators.

The relation between family history of acute myocardial infarction (AMI) and the risk of AMI was analyzed using data of a case-control study conducted in Argentina between 1992 and 1994. Case patients were 1,060 subjects with AMI admitted to 35 coronary care units, and controls were 1,071 subjects admitted to the same network of hospitals where cases had been identified, for a wide spectrum of acute conditions unrelated to known or likely risk factors for AMI: 31% of cases versus 15% of controls reported > or = 1 first-degree relative with history of AMI. Compared with subjects without family history of AMI, the odds ratio (OR) of AMI, after allowance for age, sex, cholesterolemia, smoking, diabetes, hypertension, body mass index, education, social class, and physical exercise, was 2.18 (95% confidence interval [CI] 1.74 to 2.74) for those with family history of AMI. The OR was 2.04 (95% CI 1.60 to 2.60) for subjects with 1 relative, and 3.18 (95% C 1.86 to 5.44) for those reporting > or = 2 relatives with AMI. In women the OR for any family history of AMI was 2.83, and in men 2.01. The association was of similar magnitude if the mother (OR 1.98), the father (OR 2.13), or a sibling (OR 2.48) had had an AMI. The association with family history was stronger at a younger age because the OR for subjects reporting > or = 2 more relatives with a history of AMI was 4.42 for subjects aged < 55 years, and 3.00 for those aged > or = 55 years. The association between AMI and family history of AMI was consistent across separate strata of education, social class, smoking, and serum cholesterol, but was less strong in subjects with history of diabetes and hypertension. When the interaction of known risk factors with family history of AMI was analyzed, hypercholesterolemia, hypertension, and smoking had approximately multiplicative effects on the relative risk. The OR was 4.50 for subjects with family history and cholesterol > or = 240 ml/dl, 4.52 for those with hypertension, and 5.77 for current smokers with family history of AMI. Thus, this study confirms that a family history of AMI is a strong and independent risk factor for AMI. In this population from Argentina, family history accounted for 14% of all cases of AMI in men and 26% in women.

Aspirin anticoagulation in children with mechanical aortic valves.

The optimal method of anticoagulation in children with mechanical heart valves is controversial. Between 1975 and 1986, aspirin or aspirin with dipyridamole has been used for anticoagulation in children receiving a mechanical aortic valve at the University of California, San Francisco. Fifty-one patients (ages 1 to 23 years, mean 12.9 years) were treated with aspirin (n = 45) or aspirin with dipyridamole (n = 6) and observed a mean of 36.5 months (range 3 to 100 months). There were four late deaths: two from endocarditis and two from other medical problems, but none related to thrombosis or embolus. Follow-up was accomplished by direct contact with the patient, parent, or referring physician. Two patients (3.9%) were lost to late follow-up. One minor neurologic event occurred perioperatively and resolved spontaneously. There were no postoperative thromboembolic events. Eleven asymptomatic children were recently studied by magnetic resonance imaging or computed axial tomography of the brain and had no evidence of prior silent cerebral thromboembolic defects. There were four patients (5.9%) who had minor hemorrhagic complications: Three patients had nosebleeds and one patient had an upper gastrointestinal hemorrhage. Five patients were changed to warfarin anticoagulation: the patient with upper gastrointestinal hemorrhage and four older patients because of physician preference, all after uncomplicated aspirin therapy. There were no mechanical valve failures, although one patient required reoperation 9 months later for perivalvular leak. All children have remained in normal sinus or paced rhythm during follow-up. These results show that children with mechanical aortic valves in normal sinus rhythm can be safely treated with aspirin (or aspirin with dipyridamole) with little risk of thromboembolic events, valve thrombosis, or valve failure. Hemorrhagic complications resulting from aspirin are minor and easily treated.

Selective pulmonary vasodilation with ATP-MgCl2 during pulmonary hypertension in lambs.

We investigated the effects of infusions of ATP-MgCl2 on the circulation in 11 spontaneously breathing newborn lambs during pulmonary hypertension induced either by the infusion of U-46619, a thromboxane A2 mimetic, or by hypoxia. During pulmonary hypertension induced by U-46619, ATP-MgCl2 (0.01-1.0 mg.kg-1.min-1) caused a significant dose-dependent decrease in pulmonary arterial pressure (12.4-40.7%, P less than 0.05), while systemic arterial pressure decreased only at the highest doses (P less than 0.05). Left atrial infusions of ATP-MgCl2 caused systemic hypotension without decreasing pulmonary arterial pressure. During hypoxia-induced pulmonary hypertension, ATP-MgCl2 caused a similar significant dose-dependent decrease in pulmonary arterial pressure (12.0-41.1%, P less than 0.05), while systemic arterial pressure decreased only at high doses (P less than 0.05). Regression analysis showed selectivity of the vasodilating effects of ATP-MgCl2 for the pulmonary circulation during pulmonary hypertension induced either by U-46619 or hypoxia. ATP-MgCl2 is a potent vasodilator with a rapid metabolism that allows for selective vasodilation of the vascular bed first encountered (pulmonary or systemic). We conclude that infusions of ATP-MgCl2 may be clinically useful in the treatment of children with pulmonary hypertension.

Bradykinin produces pulmonary vasodilation in fetal lambs: role of prostaglandin production.

Bradykinin produces pulmonary vasodilation and also stimulates production of other pulmonary vasodilators, including prostaglandin I2 (PGI2) and endothelial-derived relaxing factor. In 12 chronically instrumented fetal lambs, we therefore investigated potential mediation of the bradykinin response by PGI2 or other cyclooxygenase products. A 15-min infusion of bradykinin (approximately 1 microgram/kg estimated fetal wt/min) increased fetal pulmonary blood flow by 522% (P less than 0.05) and decreased pulmonary vascular resistance by 86% (P less than 0.05); plasma 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) concentration also increased (P less than 0.05). After cyclooxygenase inhibition by indomethacin (3 mg), bradykinin increased pulmonary blood flow by only 350% (P less than 0.05) and decreased pulmonary vascular resistance by 83% (P less than 0.05); plasma 6-keto-PGF1 alpha concentrations did not increase. The increase in pulmonary blood flow produced by bradykinin was greater before administration of indomethacin than after (P less than 0.05). These studies demonstrate that bradykinin produces fetal pulmonary vasodilation by at least two mechanisms, one dependent on and the other independent of PGI2 production, the latter mechanism predominating.

K+ channel pulmonary vasodilation in fetal lambs: role of endothelium-derived nitric oxide.

To define the role and mechanism of action of K+ channels in regulating fetal pulmonary vascular tone, we studied the hemodynamic effects of pinacidil (a K+ channel activator) and glibenclamide (a K+ channel blocker). The effects of pinacidil were compared with those of acetylcholine [an endothelium-derived relaxing factor- (EDRF) dependent pulmonary vasodilator] and 8-bromoguanosine 3',5'-cyclic monophosphate (8-bromo-cGMP, an EDRF-independent pulmonary vasodilator) before and after treatment with N omega-nitro-L-arginine [a competitive inhibitor of an EDRF, endothelium-derived nitric oxide (EDNO), synthesis], or L-arginine (the substrate for the formation of EDNO). In 14 unanesthetized fetal lambs in utero, catheters were inserted into the fetal pulmonary artery, descending aorta, left atrium, and superior vena cava to measure pressures and administer drugs. An ultrasonic flow transducer was placed around the left pulmonary artery to measure flow (QP) continuously. In eight animals, pinacidil, acetylcholine, and 8-bromo-cGMP caused similar acute maximal increases in QP of 128, 137, and 155 ml/min, respectively. After a 60-min infusion of N omega-nitro-L-arginine (2.07 +/- 0.27 mg.kg-1.min-1), the increase in QP caused by acetylcholine and pinacidil was significantly attenuated, by 84 and 68%, respectively, with only a 10% attenuation of the increase in QP caused by 8-bromo-cGMP. In six additional N omega-nitro-L-arginine-pretreated fetal lambs, infusion of L-arginine (32.2 +/- 4.3 mg.kg-1.min-1) restored the vasodilatory effects of acetylcholine and pinacidil. A 20-min infusion of glibenclamide (n = 6; 0.64 +/- 0.07 mg.kg-1.min-1) blocked the vasodilation by pinacidil but not acetylcholine.(ABSTRACT TRUNCATED AT 250 WORDS)

EDRF inhibition attenuates the increase in pulmonary blood flow due to oxygen ventilation in fetal lambs.

At birth, pulmonary vasodilation occurs during rhythmic distension of the lungs and oxygenation. Inhibition of prostaglandin synthesis prevents pulmonary vasodilation during rhythmic distension of the lungs but not during oxygenation. Because endothelium-derived relaxing factor (EDRF) modulates pulmonary vascular tone at birth, at rest, and during hypoxia in older animals, we hypothesized that EDRF may modulate pulmonary vascular tone during oxygenation in fetal lambs. We studied the responses to N omega-nitro-L-arginine, a competitive inhibitor of EDRF synthesis, in nine near-term fetal lambs and to drug vehicle in six of these lambs and the subsequent responses to in utero ventilation with 95% O2 in these fetal lambs. In all fetal lambs, prostaglandin synthesis was prevented by meclofenamate. N omega-nitro-L-arginine increased pulmonary and systemic arterial pressures by 28% (P < 0.05) and 31% (P < 0.05), respectively, and decreased pulmonary blood flow by 83% (P < 0.05). In the controls, ventilation with 95% O2 increased pulmonary blood flow by 1,050% (P = 0.05) without changing pressures, thereby decreasing pulmonary vascular resistance by 88% (P = 0.05). During N omega-nitro-L-arginine infusion, ventilation with 95% O2 increased pulmonary blood flow by 162% (P = 0.05) and decreased pulmonary vascular resistance by 74% (P = 0.05). This suggests that EDRF may play an important role in modulating resting pulmonary vascular tone in fetal lambs and in the vasodilatory response to ventilation with O2 in utero.

In vivo attenuation of endothelium-dependent pulmonary vasodilation by methylene blue.

In vitro evidence suggests that resting pulmonary vascular tone and endothelium-dependent pulmonary vasodilation are mediated by changes in vascular smooth muscle concentrations of guanosine 3',5'-cyclic monophosphate (cGMP). We investigated this hypothesis in vivo in 19 mechanically ventilated intact lambs by determining the hemodynamic effects of methylene blue (a guanylate cyclase inhibitor) and then by comparing the hemodynamic response to five vasodilators during pulmonary hypertension induced by the infusion of U-46619 (a thromboxane A2 mimic) or methylene blue. Methylene blue caused a significant time-dependent increase in pulmonary arterial pressure. During U-46619 infusions, acetylcholine, ATP-MgCl2, sodium nitroprusside, isoproterenol, and 8-bromo-cGMP decreased pulmonary arterial pressure. During methylene blue infusions, the decreases in pulmonary arterial pressure caused by acetylcholine and ATP-MgCl2 (endothelium-dependent vasodilators) and sodium nitroprusside (an endothelium-independent guanylate cyclase-dependent vasodilator) were attenuated by greater than 50%. The decreases in pulmonary arterial pressure caused by isoproterenol and 8-bromo-cGMP (endothelium-independent vasodilators) were unchanged. This study in intact lambs supports the in vitro evidence that changes in vascular smooth muscle cell concentrations of cGMP in part mediate resting pulmonary vascular tone and endothelium-dependent pulmonary vasodilation.

Infant coarctation: a spectrum in clinical presentation and treatment.

Between 1975 and 1985, 125 infants 2 to 365 days old (majority, 30 days old or less) with coarctation of the aorta underwent surgical repair. Forty-seven patients (38%) had severe congestive heart failure (CHF), metabolic acidosis, and poor systemic perfusion. The predominant operative technique was synthetic patch aortoplasty (100 patients); the remaining 25 had an end-to-end anastomosis. There were no operative deaths. Perioperative complications were minimized with the synthetic patch technique (less than 15%). For patients surviving at least 3 months after repair, the arm-leg systolic blood pressure gradient was relieved in 82% (71/87) of the patients having patch aortoplasty versus 65% (15/23) of the patients with end-to-end anastomosis. Although the rate of reoperation between the two groups was similar (patch, 5 [6%]; end-to-end, 3 [13%], two of the reoperations in the patch group were for preexisting hypoplastic transverse aortic arch. Late deaths (20 patients, 16%) were due to other major associated cardiac anomalies. Patch aneurysms have not occurred. Expedient use of synthetic patch aortoplasty has decreased perioperative complications, relieved coarctation gradients for CHF, increased early survival even in the presence of complex or associated cardiac anomalies, and has an acceptable rate of recurrent coarctation (6 to 13%).

Tricuspid regurgitation in children: a pulsed Doppler, contrast echocardiographic and angiographic comparison.

Thirty-one children with congenital heart disease were examined for tricuspid regurgitation by four methods: (1) auscultation, (2) pulsed Doppler echocardiography, (3) saline contrast echocardiography, and (4) right ventricular angiography. Tricuspid regurgitation was detected in three children by auscultation, in 20 by pulsed Doppler echocardiography, in 21 by saline contrast echocardiography, and in 20 by right ventricular angiography. To determine the prevalence of tricuspid regurgitation in children suspected of having congenital heart disease, we reviewed 5417 Doppler echocardiograms performed between 1983 and 1985. Tricuspid regurgitation was detected in 399 of 4670 children (8.5%) with congenital heart disease and in 26 of 106 newborns (25%) with respiratory distress. By comparison, tricuspid regurgitation was detected in only 19 of 641 (3%) normal children. Tricuspid regurgitation is uncommon in normal children, but its incidence in children with congenital heart disease and/or respiratory distress is high.

Altered endothelial function in lambs with pulmonary hypertension and acute lung injury.

Acute lung injury produces pulmonary hypertension, altered vascular reactivity, and endothelial injury. To determine whether acute lung injury impairs the endothelium-dependent regulation of pulmonary vascular tone, 16 lambs were studied during U46619-induced pulmonary hypertension without acute lung injury, or air embolization-induced pulmonary hypertension with acute lung injury. The hemodynamic responses to endothelium-dependent (acetylcholine, ATP, ET-1, and 4 Ala ET-1 [an ETb receptor agonist]) and endothelium-independent (nitroprusside and isoproterenol) vasodilators were compared. During U46619-induced pulmonary hypertension, all vasodilators decreased pulmonary arterial pressure and vascular resistance (P < 0.05). During air embolization-induced pulmonary hypertension, the pulmonary vasodilating effects of acetylcholine, ATP, and 4 Ala ET-1 were attenuated (P < 0.05); the pulmonary vasodilating effects of nitroprusside and isoproterenol were unchanged; and the pulmonary vasodilating effects of ET-1 were reversed, producing pulmonary vasoconstriction (P < 0.05). During air embolization, the pulmonary vasoconstricting effects of ET-1 were blocked by BQ 123, an ETa receptor antagonist. The systemic effects of the vasoactive drugs were similar during both conditions. We conclude that pulmonary hypertension with acute lung injury induced by air embolization results in endothelial dysfunction; there is selective impairment of endothelium-dependent pulmonary vasodilation and an altered response to ET-1 from pulmonary vasodilation to vasoconstriction. This altered response to ET-1 is associated with decreased ETb receptor-mediated vasodilation and increased ETa receptor-mediated vasoconstriction. Endothelial injury and dysfunction account, in part, for the altered regulation of pulmonary vascular tone during pulmonary hypertension with acute lung injury.

Synthetic patch aortoplasty. A simplified approach for coarctation in repairs during early infancy and thereafter.

Synthetic patch aortoplasty is an expedient, safe technique for coarctation repairs during early infancy and thereafter for reoperation since it affords both an immediate hemodynamic result and potential for late growth while avoiding sacrifice of a major arch vessel. The surgical advantages include minimization of the total cross-clamp time (10 minutes in infants and 12 minutes in older patients) and elimination of the need to sacrifice collateral vessels and the need for extensive dissection for proximal and distal control. Hence, this technique has minimized the associated severe complications of coarctation repair, even in emergency cases. In our study, there were no operative deaths, spinal cord injuries or recoarctation, and intraoperative cardiac arrest occurred in only 3 percent of the patients.

Future research directions in persistent pulmonary hypertension of the newborn.

Therapy of infants with PPHN is largely supportive because the etiology and the course of the disease are variable. The authors show that continued research on the regulation of perinatal circulation and the changes that occur with ventilation will lead to more specific therapy of infants with PPHN.