DOACs in Patients With Giant Coronary Artery Aneurysms After Kawasaki Disease

This case series examines outcomes among patients with giant coronary artery aneurysms after Kawasaki disease treated with direct oral anticoagulants (DOACs).

Long-term health outcomes in young adults after Kawasaki disease

Background

We compared the long-term health of adults with prior Kawasaki disease (KD) to controls and determined whether outcomes varied by coronary artery (CA) status.

Methods

We conducted a prospective cohort study of 258 KD subjects (mean 19 ± 9 years since KD) and 148 age-similar controls who completed extensive health questionnaires. KD subjects were divided into 2 groups, Cohort 1: 109 subjects followed since KD diagnosis at our institution; Cohort 2: 149 KD subjects diagnosed elsewhere.

Results

KD subjects and controls were of similar age at the time of questionnaire completion (p = 0.50). Overall, 128 subjects (including 60 in Cohort 1) reported normal CAs during and after KD. Compared to controls, KD subjects with normal CAs reported several medical conditions with increased prevalence including migraine headaches, shortness of breath, and leg pain with walking, among others. When limited to Cohort 1, KD subjects were significantly more likely to report chest pain (47% vs 16%, p < 0.001) or palpitations (23% vs 10%, p = 0.01) compared to controls. Prevalence of depression was similar (7% vs 5%, p = 0.73).

Conclusions

Despite always having normal CAs in the acute and subacute phases of KD, young adults with a history of KD with normal coronaries were more likely than controls to experience cardiovascular symptoms. These differences could be influenced by anxiety or depression, but report of depression was similar between groups. Whether these health differences reflect a heightened awareness of symptoms among KD subjects, or underlying vascular pathology (i.e. vasospasm, microvascular dysfunction, other) merits further study.

Falling Through the Cracks: The Current Gap in the Health Care Transition of Patients With Kawasaki Disease: A Scientific Statement From the American Heart Association

Background

Health care transition (HCT) is a period of high vulnerability for patients with chronic childhood diseases, particularly when patients shift from a pediatric to an adult care setting. An increasing number of patients with Kawasaki disease (KD) who develop medium and large coronary artery aneurysms (classified by the American Heart Association according to maximal internal coronary artery diameter Z‐scores ≥5 and ≥10, respectively) are becoming adults and thus undergoing an HCT. However, a poor transition to an adult provider represents a risk of loss to follow‐up, which can result in increasing morbidity and mortality.

Methods and Results

This scientific statement provides a summary of available literature and expert opinion pertaining to KD and HCT of children as they reach adulthood. The statement reviews the existing life‐long risks for patients with KD, explains current guidelines for long‐term care of patients with KD, and offers guidance on assessment and preparation of patients with KD for HCT. The key element to a successful HCT, enabling successful transition outcomes, is having a structured intervention that incorporates the components of planning, transfer, and integration into adult care. This structured intervention can be accomplished by using the Six Core Elements approach that is recommended by the American Academy of Pediatrics, the American Academy of Family Physicians, and the American College of Physicians.

Conclusions

Formal HCT programs for patients with KD who develop aneurysms should be established to ensure a smooth transition with uninterrupted medical care as these youths become adults.

Biomarkers of inflammation and fibrosis in young adults with history of Kawasaki disease

Background

Myocardial histology from autopsies of young adults with giant coronary artery aneurysms following Kawasaki disease (KD) shows bridging fibrosis beyond the territories supplied by the aneurysmal arteries. The etiology of this fibrosis is unknown, but persistent, low-level myocardial inflammation and microcirculatory ischemia are both possible contributing factors. To investigate the possibility of subclinical myocardial inflammation or fibrosis, we measured validated biomarkers in young adults with a remote history of KD.

Methods

We measured plasma calprotectin, galectin-3 (Gal-3), growth differentiation factor-15 (GDF-15), soluble ST2 (sST2), and serum procollagen type 1C-terminal propeptide (P1CP) in 91 otherwise healthy young adults with a remote history of KD and in 88 age-similar, healthy controls. KD subjects were stratified by coronary artery aneurysm (CAA) status and history of remote myocardial infarction (MI).

Results

After correction for multiple testing, calprotectin, Gal-3, and GDF-15 levels were significantly higher in subjects with persistent CAA (n = 26) compared with KD subjects with remodeled CAA (n = 20, p = 0.005, 0.001, 0.0036, respectively). In a multivariable regression model with CA status as the main predictor and adjusting for sex, MI history, and interval from KD onset, CA status was a significant predictor (Persistent CAA vs KD Normal CA) of calprotectin, Gal-3, GDF-15 and sST2 levels (p = 0.004, <0.001, 0.007, and 0.049, respectively).

Conclusions

These results suggest that ongoing inflammation and fibrosis may be occurring in individuals with persistent CAA. Longitudinal follow-up is needed to clarify the clinical significance of these elevated biomarker levels in this patient population that requires life-long monitoring.

Lifetime cardiovascular management of patients with previous Kawasaki disease

Kawasaki disease (KD) is an inflammatory disorder of young children, associated with vasculitis of the coronary arteries with subsequent aneurysm formation in up to one-third of untreated patients. Those who develop aneurysms are at life-long risk of coronary thrombosis or the development of stenotic lesions, which may lead to myocardial ischaemia, infarction or death. The incidence of KD is increasing worldwide, and in more economically developed countries, KD is now the most common cause of acquired heart disease in children. However, many clinicians in the UK are unaware of the disorder and its long-term cardiac complications, potentially leading to late diagnosis, delayed treatment and poorer outcomes. Increasing numbers of patients who suffered KD in childhood are transitioning to the care of adult services where there is significantly less awareness and experience of the condition than in paediatric services. The aim of this document is to provide guidance on the long-term management of patients who have vascular complications of KD and guidance on the emergency management of acute coronary complications. Guidance on the management of acute KD is published elsewhere.

Circulating Markers of Inflammation Persist in Children and Adults With Giant Aneurysms After Kawasaki Disease

Background:

The sequelae of Kawasaki disease (KD) vary widely with the greatest risk for future cardiovascular events among those who develop giant coronary artery aneurysms (CAA). We sought to define the molecular signature associated with different outcomes in pediatric and adult KD patients.

Methods:

Molecular profiling was conducted using mass spectrometry–based shotgun proteomics, transcriptomics, and glycomics methods on 8 pediatric KD patients at the acute, subacute, and convalescent time points. Shotgun proteomics was performed on 9 KD adults with giant CAA and matched healthy controls. Plasma calprotectin was measured by ELISA in 28 pediatric KD patients 1 year post-KD, 70 adult KD patients, and 86 healthy adult volunteers.

Results:

A characteristic molecular profile was seen in pediatric patients during the acute disease, which resolved at the subacute and convalescent periods in patients with no coronary artery sequelae but persisted in 2 patients who developed giant CAA. We, therefore, investigated persistence of inflammation in KD adults with giant CAA by shotgun proteomics that revealed a signature of active inflammation, immune regulation, and cell trafficking. Correlating results obtained using shotgun proteomics in the pediatric and adult KD cohorts identified elevated calprotectin levels in the plasma of patients with CAA. Investigation of expanded pediatric and adult KD cohorts revealed elevated levels of calprotectin in pediatric patients with giant CAA 1 year post-KD and in adult KD patients who developed giant CAA in childhood.

Conclusions:

Complex patterns of biomarkers of inflammation and cell trafficking can persist long after the acute phase of KD in patients with giant CAA. Elevated levels of plasma calprotectin months to decades after acute KD and infiltration of cells expressing S100A8 and A9 in vascular tissues suggest ongoing, subclinical inflammation. Calprotectin may serve as a biomarker to inform the management of KD patients following the acute illness.

The State of the Absorb Bioresorbable Scaffold: Consensus From an Expert Panel

Significant progress has been made in the percutaneous coronary intervention technique from the days of balloon angioplasty to modern-day metallic drug-eluting stents (DES). Although metallic stents solve a temporary problem of acute recoil following balloon angioplasty, they leave behind a permanent problem implicated in very late events (in addition to neoatherosclerosis). BRS were developed as a potential solution to this permanent problem, but the promise of these devices has been tempered by clinical trials showing increased risk of safety outcomes, both early and late. This is not too dissimilar to the challenges seen with first-generation DES in which refinement of deployment technique, prolongation of dual antiplatelet therapy, and technical iteration mitigated excess risk of very late stent thrombosis, making DES the treatment of choice for coronary artery disease. This white paper discusses the factors potentially implicated in the excess risks, including the scaffold consideration and deployment technique, and outlines patient and lesion selection, implantation technique, and dual antiplatelet therapy considerations to potentially mitigate this excess risk with the first-generation thick strut Absorb scaffold (Abbott Vascular, Abbott Park, Illinois). It remains to be seen whether these considerations together with technical iterations will ultimately close the gap between scaffolds and metal stents for short-term events while at the same time preserving options for future revascularization once the scaffold bioresorbs.

Management of sequelae of Kawasaki disease in adults

Background: A growing population of young adults is presenting to cardiologists with late manifestations of Kawasaki disease (KD) that include cardiomyopathy, ischemia, and infarction. The management of these conditions differs in important ways from atherosclerotic heart disease, and yet there is little awareness in the adult cardiology community regarding the special challenges posed by the cardiovascular sequelae of KD.

Methods: Observations were made on a population of 140 adult KD patients enrolled in the San Diego Adult KD Collaborative Study.

Results: Coronary artery aneurysms resulting from KD in childhood are associated with a high risk of thrombosis and stenosis at the inlet or outlet of the aneurysm. These aneurysms are often highly calcified and may contain a large thrombus burden that may obscure the true size of the aneurysm. Pitfalls in the management of these patients stem largely from failure to recognize the nature of the lesions, which leads to attempts to dilate highly calcified stenotic segments and undersizing of stents. Intravascular ultrasound is helpful in appreciating the true dimensions of the aneurysm, which may be filled with thrombus. Thrombolysis and use of anti-platelet agents followed by systemic anti-coagulation are appropriate management strategies for patients presenting with acute infarction. Bypass grafting with the internal thoracic arteries can be a successful strategy, but care must be taken to avoid competitive flow through the native vessel leading to graft failure. In contrast to the individuals who developed coronary artery aneurysms, young adults who had documented normal echocardiograms associated with their acute KD in childhood and who have no evidence of calcium deposition in the arterial wall as assessed by computed tomography (CT) calcium score appear to have no increased cardiovascular risk in the medium term. Long-term outcomes for adults post-KD in childhood are still being defined.

Conclusions: KD poses special management challenges for the adult cardiologist who must recognize the unique features of the cardiovascular lesions in this growing population of patients.

Usefulness of Calcium Scoring as a Screening Examination in Patients With a History of Kawasaki Disease

Subsets of patients with a remote history of Kawasaki disease (KD) have coronary artery aneurysms with associated risks of late morbidity. In a pilot study, we previously showed that computed tomography (CT) coronary artery calcium (CAC) scoring detects late CAC in patients with aneurysms and a remote history of KD. We performed CT calcium volume scoring in 166 subjects (median age 19.5 years) with a remote history of KD (median interval from KD to CT 15.1 years). Coronary arteries were classified as normal (n = 100), transiently dilated (n = 23), persistently dilated (n = 10), remodeled aneurysm (n = 9), or aneurysm (n = 24) based on echocardiography. All subjects with coronary arteries classified as normal, persistently dilated, or remodeled aneurysm had zero CAC. Of the 24 subjects with coronary aneurysms, all but 5 had CAC (median volume 542 mm³; range 17 to 8,218 mm³). For subjects imaged ≥9 years after their acute KD (n = 144), the presence of CAC had a sensitivity of 95% and a specificity of 100% for detecting coronary artery abnormalities (defined as coronary artery aneurysm and/or stenosis). In conclusion, coronary calcification was not observed in subjects with a history of KD who had normal coronary arteries by echocardiography during the acute phase. Coronary calcification, which may be severe, occurs late in patients with coronary aneurysms. Therefore, CAC scanning may be a useful tool to screen patients with a remote history of KD or suspected KD and unknown coronary artery status.

The Intersection of Medical Child Abuse and Medical Complexity

Children with medical complexity and victims of medical child abuse may have similar clinical presentations. Atypical or unexplained signs and symptoms due to rare diseases may lead providers to suspect medical child abuse when not present. Conversely, medical child abuse may be the cause of or coexist with medical complexity. Careful consideration of whether or not medical child abuse is present is essential when assessing a child with medical complexity since either diagnosis has significant consequences for children and families.

Galectin-3 is a marker of myocardial and vascular fibrosis in Kawasaki disease patients with giant aneurysms

BACKGROUNDS

Galectin-3 (Gal-3) is a multifunctional matricellular protein associated with heart failure and cardiovascular events. Gal-3 is required for transforming growth factor-β pathway-mediated myofibroblast activation that is a key process in coronary artery aneurysm formation in Kawasaki Disease (KD). Autopsies from young adults late after KD onset (AKD) have demonstrated bridging fibrosis throughout the myocardium and arteries. In this study, we postulated that Gal-3 may participate in the pathogenesis of myocardial and vascular fibrosis and the remodeling of coronary artery aneurysms following acute KD.

METHODS AND RESULTS

We measured plasma Gal-3 levels in 63 pediatric KD (PKD) and 81 AKD subjects. AKD subjects with giant aneurysms had significantly higher Gal-3 levels compared to the other adult groups (all p<0.05). All PKD groups had significantly higher Gal-3 levels than pediatric healthy controls (HC) (all p<0.05). Histological and immunohistochemical staining was performed on tissues from 10 KD autopsies and one explanted heart. Gal-3 positive staining was detected associated with acute inflammation and in spindle-shaped cells in the myocardium and arterial wall in KD subjects with giant aneurysms.

CONCLUSIONS

AKD subjects with giant aneurysms and PKD subjects had significantly higher plasma Gal-3 levels than HC and Gal-3 expression was increased in the myocardium of KD subjects who died with either acute inflammation or marked myocardial fibrosis. Gal-3 may be a clinically useful biomarker that identifies a subset of KD patients at highest risk of myocardial and vascular fibrosis, and may be an attractive therapeutic target to prevent myocardial dysfunction in this subset.

Role of TGF-β Signaling in Remodeling of Noncoronary Artery Aneurysms in Kawasaki Disease

Coronary artery aneurysms (CAA) remain an important complication of Kawasaki disease (KD), the most common form of pediatric acquired heart disease in developed countries. Potentially life-threatening CAA develop in 25% of untreated children and 5% of children treated with high-dose intravenous immunoglobulin during the acute phase of the self-limited vasculitis. Noncoronary artery aneurysms (NCAA) in extraparenchymal, muscular arteries occur in a minority of patients with KD who also have CAA, yet little is understood about their formation and remodeling. We postulated that activation of the transforming growth factor-β (TGF-β) pathway in KD may influence formation and remodeling of aneurysms in iliac, femoral, and axillary arteries, the most common sites for NCAA. We studied a resected axillary artery from one adult and endarterectomy tissue from the femoral artery from a second adult, both with a history of CAA and NCAA following KD in infancy. Histology of the axillary artery aneurysm revealed destruction of the internal elastic lamina and recanalization of organized thrombus, while the endarterectomy specimen showed dense calcification and luminal myofibroblastic proliferation. Immunohistochemistry for molecules in the TGF-β signaling pathway revealed increased expression of TGF-β2, TGF-β receptor 2, and phosphorylated SMAD3. These findings suggest ongoing tissue remodeling of the aneurysms decades after the acute injury and demonstrate the importance of the TGF-β signaling pathway in this process.

Missed Kawasaki disease in childhood presenting as myocardial infarction in adults

Kawasaki disease (KD) is an acute, self-limited vasculitis that occurs in young children and was first described by Japanese pediatrician Tomisaku Kawasaki in 1967. Although originally thought to be a rare condition, KD has become the most common cause of acquired heart disease in the pediatric population in developed countries. The majority of patients with KD appear to have a benign prognosis, but a subset of patients with coronary artery aneurysms are at risk for ischemic events and require lifelong treatment. In the 4 decades since the initial recognition of KD, the number of patients reaching adulthood has continued to grow. Adult cardiologists will be increasingly involved in the management of these patients. Currently, there are no established guidelines for the evaluation and treatment of adult patients who have had KD. We report 4 most probable cases of KD missed in childhood and presented as acute coronary syndrome in adulthood.

Acute myocardial ischemia in adults secondary to missed Kawasaki disease in childhood

Coronary artery aneurysms that occur in 25% of untreated Kawasaki disease (KD) patients may remain clinically silent for decades and then thrombose resulting in myocardial infarction. Although KD is now the most common cause of acquired heart disease in children in Asia, the United States, and Western Europe, the incidence of KD in Egypt is unknown. We tested the hypothesis that young adults in Egypt presenting with acute myocardial ischemia may have coronary artery lesions because of KD in childhood. We reviewed a total of 580 angiograms of patients ≤40 years presenting with symptoms of myocardial ischemia. Coronary artery aneurysms were noted in 46 patients (7.9%), of whom 9 presented with myocardial infarction. The likelihood of antecedent KD as the cause of the aneurysms was classified as definite (n = 10), probable (n = 29), or equivocal (n = 7). Compared with the definite and probable groups, the equivocal group had more traditional cardiovascular risk factors, smaller sized aneurysms, and fewer coronary arteries affected. In conclusion, in a major metropolitan center in Egypt, 6.7% of adults aged ≤40 years who underwent angiography for evaluation of possible myocardial ischemia had lesions consistent with antecedent KD. Because of the unique therapeutic challenges associated with these lesions, adult cardiologists should be aware that coronary artery aneurysms in young adults may be because of missed KD in childhood.

Impact of caring for children with medical complexity and high resource use on family quality of life

PURPOSE

This study examined the impact of caring for children with medical complexity (CMC) and high resource use on family quality of life (QoL).

METHODS

Families of CMC enrolled in a complex care program completed the PedsQL Family Impact module (PedsQL FIM) and Healthcare Satisfaction module (PedsQL HCS) at enrollment then 1 and 2 years after enrollment. Tertiary center resource utilization and staff care coordination time were collected for the two years.

RESULTS

PedsQL FIM scores were low at enrollment and did not improve over time. Social Functioning, Worry, and Daily Activities were the lowest domains. PedsQL HCS scores were higher at enrollment, but also failed to improve over the two years. Changes in resource use were not associated with changes in PedsQL FIM or HCS scores. Staff care coordination time was highest for patients with ≥ 10 hospital days per year.

CONCLUSION

CMC families' low QoL did not appear to be related to healthcare satisfaction or a shift from inpatient to outpatient resource use. Less staff support for families of CMC who spent more time at home may have contributed to their continued low QoL. Further study is required to identify causes of and strategies for improving the low QoL of families of CMC.

Lipoprotein particle concentrations in children and adults following Kawasaki disease

OBJECTIVE

To test the hypothesis that children and adults with a history of Kawasaki disease (KD) are more likely to have abnormal lipoprotein particle profiles that could place them at increased risk for developing atherosclerosis later in life.

STUDY DESIGN

Fasting serum samples were obtained from 192 children and 63 adults with history of KD and 90 age-similar healthy controls. Lipoprotein particle concentrations and sizes were measured by nuclear magnetic resonance spectroscopy (LipoScience Inc, Raleigh, North Carolina), and serum was assayed for total cholesterol (TC), triglycerides, and high-density lipoprotein (HDL) cholesterol (HDL-C). Low-density lipoprotein (LDL) cholesterol was estimated using the Friedewald formula. Data were analyzed in a least-square means model, with adjustment for age and sex and with the use of Holm correction for multiple comparisons.

RESULTS

Compared with respective control groups, both adult and pediatric subjects with KD had significantly lower mean very low-density lipoprotein-chylomicron particles, intermediate-density lipoproteins, triglycerides, and TC concentrations. Pediatric subjects with KD had significantly lower LDL particle and LDL cholesterol concentrations and lower mean TC/HDL-C ratio (P < .001). In contrast, the adult subjects with KD had significantly lower HDL particle, small HDL particle, and HDL-C concentrations (P < .001), but HDL-C was within normal range.

CONCLUSIONS

Nuclear magnetic resonance lipoprotein particle analysis suggests that pediatric and adult subjects with KD, regardless of their aneurysm status, are no more likely than age-similar, healthy controls to have lipid patterns associated with increased risk of atherosclerosis.

Pregnancy in women with a history of Kawasaki disease: management and outcomes

OBJECTIVE

To characterise the obstetrical management and outcomes in a series of women with a history of Kawasaki disease (KD) in childhood.

DESIGN

Retrospective case series.

SETTING

Tertiary healthcare setting in the USA.

POPULATION

Women with a history of KD in childhood.

METHODS

Women completed a detailed health questionnaire and participated in research imaging studies as part of the San Diego Adult KD Collaborative Study.

MAIN OUTCOME MEASURES

Obstetrical management, complications during pregnancy and delivery, and infant outcomes.

RESULTS

Ten women with a history of KD in childhood carried a total of 21 pregnancies to term. There were no cardiovascular complications during labour and delivery despite important cardiovascular abnormalities in four of the ten subjects. Pregnancy was complicated by pre-eclampsia and the post-partum course was complicated by haemorrhage in one subject each. Two of the 21 progeny subsequently developed KD.

CONCLUSIONS

Women with important cardiovascular sequelae from KD in childhood should be managed by a team that includes both a maternal-fetal medicine specialist and a cardiologist. Pre-pregnancy counselling should include delineation of the woman's current functional and structural cardiovascular status and appropriate adjustment of medications, but excellent outcomes are possible with appropriate care. Review of the English and Japanese literature on KD and pregnancy revealed the occurrence of myocardial infarction during pregnancy in women with missed KD and aneurysms that were not diagnosed until their acute event. Our study highlights the need for counselling with regard to the increased genetic risk of KD in offspring born to these mothers.

Furegrelate, a thromboxane synthase inhibitor, blunts the development of pulmonary arterial hypertension in neonatal piglets

The development of pulmonary arterial hypertension (PAH) in pediatric patients has been linked to the production of the arachidonic acid metabolite, thromboxane A₂ (TxA₂). The present study evaluated the therapeutic effect of furegrelate sodium, a thromboxane synthase inhibitor, on the development of PAH in a neonatal piglet model. Three-day-old piglets were exposed to 21 days of normoxia (N; 21% F_IO₂) or chronic hypoxia (CH; 10% F_IO₂). A third group of piglets received the oral TxA₂ synthase inhibitor, furegrelate (3 mg/kg, 2 or 3 times daily) at the induction of CH. In vivo hemodynamics confirmed a 2.55-fold increase of the pulmonary vascular resistance index (PVRI) in CH piglets (104±7 WU) compared to N piglets (40±2 WU). The CH piglets treated twice daily with furegrelate failed to show improved PVRI, but furegrelate three times daily lowered the elevated PVRI in CH piglets by 34% to 69±5 WU and ameliorated the development of right ventricular hypertrophy. Microfocal X-ray computed tomography (CT) scanning was used to estimate the diameter-independent distensibility term, α (% change in diameter per Torr). Pulmonary arterial distensibility in isolated lungs of CH piglets (α=1.0±0.1% per Torr) was lower than that of N piglets (α=1.5±0.1% per Torr) indicative of vascular remodeling. Arterial distensibility was partially restored in furegrelate-treated CH piglets (α =1.2±0.1% per Torr) and microscopic evidence showing muscularization of small pulmonary arteries also was less prominent in these animals. Finally, isolated lungs of furegrelate-treated piglets showed lower basal and vasodilator-induced transpulmonary pressures compared to CH animals. These findings suggest that pharmacological inhibition of TxA₂ synthase activity by furegrelate blunts the development of hypoxia-induced PAH in an established neonatal piglet model primarily by preserving the structural integrity of the pulmonary vasculature.

Prevalence of Kawasaki disease in young adults with suspected myocardial ischemia

BACKGROUND

Up to 25% of patients with untreated Kawasaki disease (KD) and 5% of those treated with intravenous immunoglobulin will develop coronary artery aneurysms. Persistent aneurysms may remain silent until later in life when myocardial ischemia can occur. We sought to determine the prevalence of coronary artery aneurysms suggesting a history of KD among young adults undergoing coronary angiography for evaluation of possible myocardial ischemia.

METHODS AND RESULTS

We reviewed the medical histories and coronary angiograms of all adults <40 years of age who underwent coronary angiography for evaluation of suspected myocardial ischemia at 4 San Diego hospitals from 2005 to 2009 (n=261). History of KD-compatible illness and cardiac risk factors were obtained by medical record review. Angiograms were independently reviewed for the presence, size, and location of aneurysms and coronary artery disease by 2 cardiologists blinded to the history. Patients were evaluated for number of risk factors, angiographic appearance of their coronary arteries, and known history of KD. Of the 261 young adults who underwent angiography, 16 had coronary aneurysms. After all clinical criteria were assessed, 5.0% had aneurysms definitely (n=4) or presumed (n=9) secondary to KD as the cause of their coronary disease.

CONCLUSIONS

Coronary sequelae of KD are present in 5% of young adults evaluated by angiography for myocardial ischemia. Cardiologists should be aware of this special subset of patients who may benefit from medical and invasive management strategies that differ from the strategies used to treat atherosclerotic coronary artery disease.

When children with Kawasaki disease grow up: Myocardial and vascular complications in adulthood

Kawasaki disease (KD) is an acute, self-limited vasculitis that typically occurs in young children and was first described by Japanese pediatrician Tomisaku Kawasaki in 1967. Although originally thought to be a rare condition, KD has become the most common cause of acquired heart disease in the pediatric age group in developed countries. The majority of patients with KD appear to have a benign prognosis, but a subset of patients with coronary artery aneurysms are at risk for ischemic events and require lifelong treatment. In the 4 decades that have passed since the initial recognition of KD, the number of patients reaching adulthood has continued to grow. Adult cardiologists will be increasingly involved in the management of these patients. Currently, there are no established guidelines for the evaluation and treatment of adult patients who have had KD. We review here the current literature that may be helpful to clinicians who care for adults who experienced KD in childhood.

Upregulation of vascular calcium channels in neonatal piglets with hypoxia-induced pulmonary hypertension

Inhibition of voltage-gated, L-type Ca(2+) (Ca(L)) channels by clinical calcium channel blockers provides symptomatic improvement to some pediatric patients with pulmonary arterial hypertension (PAH). The present study investigated whether abnormalities of vascular Ca(L) channels contribute to the pathogenesis of neonatal PAH using a newborn piglet model of hypoxia-induced PAH. Neonatal piglets exposed to chronic hypoxia (CH) developed PAH by 21 days, which was evident as a 2.1-fold increase in pulmonary vascular resistance in vivo compared with piglets raised in normoxia (N). Transpulmonary pressures (DeltaPtp) in the corresponding isolated perfused lungs were 20.5 +/- 2.1 mmHg (CH) and 11.6 +/- 0.8 mmHg (N). Nifedipine reduced the elevated DeltaPtp in isolated lungs of CH piglets by 6.4 +/- 1.3 mmHg but only reduced DeltaPtp in lungs of N piglets by 1.9 +/- 0.2 mmHg. Small pulmonary arteries from CH piglets also demonstrated accentuated Ca(2+)-dependent contraction, and Ca(2+) channel current was 3.94-fold higher in the resident vascular muscle cells. Finally, although the level of mRNA encoding the pore-forming alpha(1C)-subunit of the Ca(L) channel was similar between small pulmonary arteries from N and CH piglets, a profound and persistent upregulation of the vascular alpha(1C) protein was detected by 10 days in CH piglets at a time when pulmonary vascular resistance was only mildly elevated. Thus chronic hypoxia in the neonate is associated with the anomalous upregulation of Ca(L) channels in small pulmonary arteries in vivo and the resulting abnormal Ca(2+)-dependent resistance may contribute to the pathogenesis of PAH.

Bronchial circulation angiogenesis in the rat quantified with SPECT and micro-CT

INTRODUCTION

As pulmonary artery obstruction results in proliferation of the bronchial circulation in a variety of species, we investigated this angiogenic response using single photon emission computed tomography (SPECT) and micro-CT.

MATERIALS AND METHODS

After surgical ligation of the left pulmonary artery of rats, they were imaged at 10, 20, or 40 days post-ligation. Before imaging, technetium-labeled macroaggregated albumin ((99m)Tc MAA) was injected into the aortic arch (IA) labeling the systemic circulation. SPECT/micro-CT imaging was performed, the image volumes were registered, and activity in the left lung via the bronchial circulation was used as a marker of bronchial blood flow. To calibrate and to verify successful ligation, (99m)Tc MAA was subsequently injected into the left femoral vein (IV), resulting in accumulation within the pulmonary circulation. The rats were reimaged, and the ratio of the IA to the IV measurements reflected the fraction of cardiac output (CO) to the left lung via the bronchial circulation. Control and sham-operated rats were studied similarly.

RESULTS

The left lung bronchial circulation of the control group was 2.5% of CO. The sham-operated rats showed no significant difference from the control. However, 20 and 40 days post-ligation, the bronchial circulation blood flow had increased to 7.9 and 13.9%, respectively, of CO. Excised lungs examined after barium filling of the systemic vasculature confirmed neovascularization as evidenced by tortuous vessels arising from the mediastinum and bronchial circulation.

CONCLUSION

Thus, we conclude that SPECT/micro-CT imaging is a valuable methodology for monitoring angiogenesis in the lung and, potentially, for evaluating the effects of pro- or anti-angiogenic treatments using a similar approach.

A tertiary care-primary care partnership model for medically complex and fragile children and youth with special health care needs

OBJECTIVE

To evaluate the impact of a tertiary care center special needs program that partners with families and primary care physicians to ensure seamless inpatient and outpatient care and assist in providing medical homes.

DESIGN

Up to 3 years of preenrollment and postenrollment data were compared for patients in the special needs program from July 1, 2002, through June 30, 2005.

SETTING

A tertiary care center pediatric hospital and medical school serving urban and rural patients.

PARTICIPANTS

A total of 227 of 230 medically complex and fragile children and youth with special needs who had a wide range of chronic disorders and were enrolled in the special needs program.

INTERVENTIONS

Care coordination provided by a special needs program pediatric nurse case manager with or without a special needs program physician.

MAIN OUTCOME MEASURES

Preenrollment and postenrollment tertiary care center resource utilization, charges, and payments.

RESULTS

A statistically significant decrease was found in the number of hospitalizations, number of hospital days, and tertiary care center charges and payments, and an increase was found in the use of outpatient services. Aggregate data revealed a decrease in hospital days from 7926 to 3831, an increase in clinic visits from 3150 to 5420, and a decrease in tertiary care center payments of $10.7 million. The special needs program budget for fiscal year 2005 had a deficit of $400,000.

CONCLUSION

This tertiary care-primary care partnership model improved health care and reduced costs with relatively modest institutional support.

Assessment of Recurrent Heart Failure Associated with Left Ventricular Assist Device Dysfunction

BACKGROUND

Patients with advanced heart failure may require long-term support with an intracorporeal left ventricular assist device (LVAD) before cardiac transplant, while awaiting myocardial recovery, or during destination therapy. Compared with the diagnosis of native heart dysfunction, there is less experience with the assessment of recurrent heart failure after LVAD placement.

METHODS

Ten patients (9 men, 1 woman; age, 58 +/- 11 years) were studied after LVAD placement. Six patients were studied because of recurrent heart failure; the remaining 4 had other indications for study and are reported here as controls. Cardiac catheterization, including LVAD and cannulae catheterization, and angiography were performed.

RESULTS

Inflow cannula valve regurgitation by LVAD angiography was found in 3 cases. Patients with regurgitation had a mean increased resting LVAD rate of 105 beats/min (range, 90-120); LVAD output exceeded forward cardiac output (LVAD - thermodilution cardiac output = +3.7 liters/min [0.6-6.4]). Inflow cannula obstruction identified with a filling phase pressure gradient between the left ventricle and the LVAD was found in 3 additional patients. Patients with obstruction had decreased resting LVAD rates (50 beats/min, all patients); LVAD output was less than the forward cardiac output (LVAD - thermodilution cardiac output = -2.3 liters/min [-0.8 to -3.5]). Compared with those with inflow valve regurgitation, patients with cannula obstruction had higher pulmonary capillary wedge pressures; phasic left ventricular pressure variation was reduced. Patients with cannula dysfunction underwent surgical intervention, and 4 of 6 were long-term survivors.

CONCLUSIONS

When heart failure recurs after LVAD placement, abnormalities of the inflow cannula are common. Cardiac catheterization can confirm the diagnosis before surgical intervention. Hemodynamic coupling between the left ventricle and the LVAD is increased with inflow valve regurgitation and reduced with cannula obstruction.

Hypercapnic acidosis and compensated hypercapnia in control and pulmonary hypertensive piglets

Low tidal volume/inspiratory pressure ventilator strategies result in hypercapnia, which has been shown to increase pulmonary vasomotor tone. This may be particularly detrimental in infants and children with preexistent pulmonary hypertension. In this study, a piglet model of chronic hypoxia-induced pulmonary hypertension was used to test the hypotheses that: 1) the effects of hypercapnic acidosis are exaggerated by preexistent pulmonary hypertension; and 2) the pulmonary hemodynamic effects of hypercapnic acidosis are attenuated by normalizing pH. Pulmonary hypertension was induced by 2 weeks of hypoxia. Hemodynamic responses were measured in control and pulmonary hypertensive piglets during both normoxia and hypoxia under normocapnic, hypercapnic acidotic, and compensated hypercapnic conditions. We found that: 1) hypercapnic acidosis increased both normoxic and hypoxic pulmonary vascular resistance index (PVRI) in control piglets; 2) the pressor effects of hypercapnia were not attenuated by infusing bicarbonate to normalize the pH; and 3) piglets with chronic hypoxia-induced pulmonary hypertension had elevated baseline normoxic and hypoxic PVRI, but responded to hypercapnic acidosis and compensated hypercapnia in a similar way to control piglets. These data suggest that acute hypercapnic acidosis may have deleterious effects on the pulmonary hemodynamics of normal and pulmonary hypertensive subjects which may not be acutely reversed by buffering the pH.

What leads to different mediators of alkalosis-induced vasodilation in isolated and in situ pulmonary vessels?

We previously found that nitric oxide synthase (NOS) inhibition fully blocked alkalosis-induced relaxation of piglet pulmonary artery and vein rings. In contrast, NOS inhibition alone had no effect on alkalosis-induced pulmonary vasodilation in isolated piglet lungs. This study sought to identify factors contributing to the discordance between isolated and in situ pulmonary vessels. The roles of pressor stimulus (hypoxia vs. the thromboxane mimetic U-46619), perfusate composition (blood vs. physiological salt solution), and flow were assessed. Effects of NOS inhibition on alkalosis-induced dilation were also directly compared in 150-350-microm-diameter cannulated arteries and 150-900-microm-diameter, angiographically visualized, in situ arteries. Finally, effects of NOS inhibition on alkalosis-induced vasodilation were measured in intact piglets. NOS inhibition with N(omega)-nitro-L-arginine fully abolished alkalosis-induced vasodilation in all cannulated arteries but failed to alter alkalosis-induced vasodilation in intact lungs. The results indicate that investigation of other factors, such as perivascular tissue (e.g., adventitia and parenchyma) and remote signaling pathways, will need to be carried out to reconcile this discordance between isolated and in situ arteries.

Modulation of pulmonary vasomotor tone in the fetus and neonate

The high pulmonary vascular resistance (PVR) of atelectatic, hypoxic, fetal lungs limits intrauterine pulmonary blood flow (PBF) to less than 10% of combined right and left ventricular output. At birth, PVR decreases precipitously to accommodate the entire cardiac output. The present review focuses on the role of endothelium-derived nitric oxide (NO), prostacyclin, and vascular smooth muscle potassium channels in mediating the decrease in PVR that occurs at birth, and in maintaining reduced pulmonary vasomotor tone during the neonatal period. The contribution of vasodilator and vasoconstrictor modulator activity to the pathophysiology of neonatal pulmonary hypertension is also addressed.

Stability of dopamine and epinephrine solutions up to 84 hours

OBJECTIVES

The current practice of preparing fresh dopamine and epinephrine solutions every 24 hrs may lead to hemodynamic instability caused by the interruption of infusions with each change. We determined the stability of these catecholamines over an 84-hr period and whether stability was enhanced by dextrose-containing solutions.

SETTING

Tertiary care teaching hospital.

DESIGN

The stability of dopamine and epinephrine, each at three commonly used concentrations, was studied in three vehicles (10 gm/dl dextrose in water [D10W], 5 gm/dl dextrose in water [D5W], and 0.9% NaCl in water [NS]). To mimic clinical conditions, solutions were placed on syringe pumps infusing continuously into a closed system at ambient temperature for 84 hrs.

MEASUREMENTS

Concentrations of dopamine in mg/ml and epinephrine in microg/ml were measured by high-performance liquid chromatography at 0, 24, 36, 48, 72, and 84 hrs.

RESULTS

Dopamine and epinephrine concentrations did not change over the 84-hr period regardless of the vehicles in which the drugs were prepared.

CONCLUSIONS

Clinically relevant concentrations of dopamine and epinephrine remain stable in dextrose- and saline-containing solutions for >or=84 hrs. These data suggest that solutions of these catecholamines may safely be used in clinical practice beyond the currently recommended 24 hrs.

Multiple Ca(2+)-dependent modulators mediate alkalosis-induced vasodilation in newborn piglet lungs

We previously found that alkalosis-induced vasodilation was mediated by endothelium-derived nitric oxide (EDNO) in newborn piglet pulmonary artery and vein rings precontracted with the thromboxane mimetic U-46619. In contrast, prostacyclin or K(+) channel activation contributed to the response in other preparations. This study was undertaken to determine whether EDNO alone also mediates alkalosis-induced pulmonary vasodilation in piglet lungs vasoconstricted with hypoxia and, if not, to identify the mediator(s) involved. Responses to alkalosis were measured during hypoxia under control conditions after blocking nitric oxide synthase (N(omega)-nitro-L-arginine), cyclooxygenase (meclofenamate), or both endothelium-derived modulators (Dual); after blocking voltage-dependent (4-aminopyridine), ATP- dependent (glibenclamide), or Ca(2+)-dependent K(+) (K(Ca); tetraethylammonium) K(+) channels; and after blocking both endothelium-derived modulators and K(Ca) channels (Triple). Vasodilator responses measured after 20 min of alkalosis were blunted in Dual and tetraethylammonium lungs and abolished in Triple lungs. Thus alkalosis-induced vasodilation in hypoxic lungs appeared to be mediated by three Ca(2+)-dependent modulators: EDNO, prostacyclin, and K(Ca) channels. In addition, a transient, unidentified modulator contributed to the nadir of the vasodilator response measured at 10 min of alkalosis. Future studies are needed to identify factors that contribute to the discordance between isolated vessels and whole lungs.

The Internet as a source of information on breast augmentation

The Internet was evaluated as a source of information for the layperson on the topic of breast augmentation. Three commonly used search engines (Excite, AOL, and Yahoo) were employed using the term "breast augmentation." These sites were then evaluated by each of three experienced plastic surgeons for their quality and content. Separately, 17 health Web sites were identified as authoritative by means of recommendation in lay publications. Each "supersite" was accessed, and its search engine was used. The top 10 hits for "breast augmentation" on each site were then evaluated by the senior author for content (Matthews). We found the majority of sites identified by the general search engines (AOL, Excite, Yahoo) to be physician Web sites. Forty-one unique sites were found that applied to the topic. Four of the "hits" did not actually apply to the topic. In general, the applicable Web sites contained limited but accurate procedural details and offered an interactive forum, most commonly email responses. Photographic documentation was given in less than half the sites reviewed, and most of the results shown were only "good" outcomes. Most sites did not discuss any complications of surgical procedures, but those that did were usually accurate. Eighty-three percent of the sites were biased toward a particular surgical technique. The reviewers believe that only about 15 percent of the sites were acceptable to recommend to their patients. The senior author accessed 17 Web sites that are considered authoritative health information Web sites. Each of these sites was searched for information on breast augmentation by means of its internal search engine. Only 29 percent (5 of 17) had any information in their top 10 hits. Three sites had only chat transcripts. One site had limited but accurate information with a link to the American Society of Plastic Surgeons, and one site had scientific information on product safety. No site met the criteria of accurate, complete information on the surgical procedure of breast augmentation. This study demonstrates that it is difficult for the average layperson to get authoritative information quickly and easily on at least one aspect of cosmetic surgery.

Endothelium-independent and -dependent vasodilation in alkalotic and acidotic piglet lungs

Although significant pulmonary hypertension can occur in patients treated with either hypocapnic alkalosis or "permissive" hypercapnic acidosis, the effects of sustained alkalosis or acidosis on subsequent vasodilator responses have not been established. This study measured the effects of 60-100 min of sustained alkalosis or acidosis on endothelium-independent and -dependent vasodilation with inhaled nitric oxide (iNO) and acetylcholine (ACh) in isolated lungs from 1-week-old piglets. After stabilization, lungs were divided into control (pH 7.40, PaCO(2) 40 torr, n = 5), alkalotic (pH 7.60, PaCO(2) 25 torr, n = 6), or acidotic (pH 7.25, PaCO(2) 65 torr, n = 5) groups and ventilated with 21% O(2) for 40 min. Acute hypoxic pulmonary vasoconstriction (HPV) was then induced with 4-6% O(2). After a stable pressor response had occurred (approximately 20 min), pulmonary artery dose-response relationships to increasing concentrations of iNO were measured. The iNO was then stopped and after a stable hypoxic pressure had again been reestablished (approximately 20 min), dose-responses to increasing concentrations of ACh were measured. Hypoxic pulmonary vascular resistance (PVR) was similar in all groups. Pulmonary artery pressure dose-response relationships to iNO and ACh were blunted in the alkalosis group, suggesting that both endothelium-independent and -dependent vasodilation were reduced during sustained hypocapnic alkalosis. In contrast, sustained acidosis did not alter subsequent vasodilator responses. Future studies must elucidate the mechanisms underlying blunted pulmonary vasodilation during sustained alkalosis and examine the consequences of sustained alkalosis therapy on subsequent vasodilator responses in clinical practice.

Mediators of alkalosis-induced relaxation of piglet pulmonary veins

Pulmonary venous constriction leads to significant pulmonary hypertension and increased edema formation in several models using newborns. Although alkalosis is widely used in treating neonatal and pediatric pulmonary hypertension, its effects on pulmonary venous tone have not previously been directly measured. This study sought to determine whether alkalosis caused pulmonary venous relaxation and, if so, to identify the mediator(s) involved. Pulmonary venous rings (500-microm external diameter) were isolated from 1-wk-old piglets and precontracted with the thromboxane mimetic U-46619. Responses to hypocapnic alkalosis were then measured under control conditions after inhibition of endothelium-derived modulator activity or K(+) channels. In control rings, alkalosis caused a 34.4 +/- 4.8% decrease in the U-46619-induced contraction. This relaxation was significantly blunted in rings without functional endothelium and in rings treated with nitric oxide synthase or guanylate cyclase inhibitors. However, neither cyclooxygenase inhibition nor voltage-dependent, calcium-dependent, or ATP-dependent K(+)-channel inhibitors altered alkalosis-induced relaxation. These data suggest that alkalosis caused significant dilation of piglet pulmonary veins that was mediated by the nitric oxide-cGMP pathway.

Site-specific effect of guanosine 3',5'-cyclic monophosphate phosphodiesterase inhibition in isolated lamb lungs

OBJECTIVE

To determine the effect of combining inhaled nitric oxide (NO) with an inhibitor of guanosine 3',5'-cyclic monophosphate-specific phosphodiesterase on total and segmental lung resistances.

STUDY DESIGN

A controlled laboratory study in isolated blood-perfused lungs prepared from lambs.

SETTING

Animal research facility affiliated with a university teaching hospital.

SUBJECTS

Five newborn lambs at <48 hrs of life.

INTERVENTIONS

Isolated blood-perfused lungs were prepared and treated with indomethacin (40 microg/mL) to inhibit prostaglandin synthesis. After a baseline period of normoxia (28% oxygen), pulmonary hypertension was induced with the thromboxane mimetic U46619 (0.1-0.4 microg/kg/min). During pulmonary hypertension, lungs were studied with inhaled NO only, with infusion of zaprinast only (0.25 mg/kg bolus and 0.05 mg/kg/min infusion), and with a combination of the two. For each study condition, the total pressure decrease across the lung was measured, and the inflow-outflow occlusion technique was used to partition the total pressure gradient measured at constant flow (100 mL/kg/min) into gradients across relatively noncompliant large arteries and veins and more compliant small arteries and veins.

MEASUREMENTS AND MAIN RESULTS

U46619 infusion produced significant pulmonary vasoconstriction. The combination of inhaled NO and zaprinast decreased the total pressure decrease across the lung significantly more than NO alone. This effect was primarily attributable to a significantly greater decrease in gradient across the small artery segment after inhaled NO and zaprinast compared with NO alone.

CONCLUSIONS

Guanosine 3',5'-cyclic monophosphate phosphodiesterase inhibition with zaprinast enhances the effect of inhaled NO, particularly in conditions in which small arteries represent the site of resistance. Phosphodiesterase inhibition may be a promising adjunct to inhaled NO for the treatment of persistent pulmonary hypertension.

Pulmonary vascular responses during acute and sustained respiratory alkalosis or acidosis in intact newborn piglets

Acute alkalosis-induced pulmonary vasodilation and acidosis-induced pulmonary vasoconstriction have been well described, but responses were generally measured within 5-30 min of changing pH. In contrast, several in vitro studies have found that relatively brief periods of sustained alkalosis can enhance, and sustained acidosis can decrease, vascular reactivity. In this study of intact newborn piglets, effects of acute (20 min) and sustained (60-80 min) alkalosis or acidosis on baseline (35% O2) and hypoxic (12% O2) pulmonary vascular resistance (PVR) were compared with control piglets exposed only to eucapnia. Acute alkalosis decreased hypoxic PVR, but sustained alkalosis failed to attenuate either baseline PVR or the subsequent hypoxic response. Acute acidosis did not significantly increase hypoxic PVR, but sustained acidosis markedly increased both baseline PVR and the subsequent hypoxic response. Baseline PVR was similar in all piglets after resumption of eucapnic ventilation, but the final hypoxic response was greater in piglets previously exposed to alkalosis than in controls. Thus, hypoxic pulmonary vasoconstriction was not attenuated during sustained alkalosis, but was accentuated during sustained acidosis and after the resumption of eucapnia in alkalosis-treated piglets. Although extrapolation of data from normal piglets to infants and children with pulmonary hypertension must be done with caution, this study suggests that sustained alkalosis may be of limited efficacy in treating acute hypoxia-induced pulmonary hypertension and the risks of pulmonary hypertension must be considered when using ventilator strategies resulting in permissive hypercapnic acidosis.

Discordant effects of alkalosis on elevated pulmonary vascular resistance and vascular reactivity in lamb lungs

OBJECTIVES

After an initial vasodilator response to alkalosis, many children with pulmonary hypertension exhibit marked pulmonary vascular reactivity despite continued alkalosis therapy. This study sought to a) identify the mediator of alkalosis-induced pulmonary vasodilation in isolated lamb lungs; b) determine whether alkalosis-induced pulmonary vasodilation decreases over time in this model; and c) determine whether alkalosis enhanced vascular reactivity to subsequent pressor stimuli.

DESIGN

Prospective, interventional study.

SUBJECTS

Isolated perfused lungs from 1-month-old lambs.

INTERVENTIONS

Hypocarbic alkalosis, hypoxia, and infusion of the thromboxane mimetic agent U46619

MEASUREMENTS AND MAIN RESULTS

Pulmonary artery pressure was measured at constant flow, so a change in pressure reflects change in resistance. Hypoxic pulmonary artery pressure was compared after 20 and 100 mins of hypocarbic alkalosis or normocarbia in control and cyclooxygenase-inhibited lungs. Pulmonary artery dose responses to U46619 were then measured in control lungs. Responses to hypoxia and U46619 were also compared after 60-80 mins of hypocarbic or normocarbic normoxia. Hypocarbic alkalosis acutely reduced hypoxic pulmonary vascular resistance, and this was sustained for at least 100 mins. Cyclooxygenase inhibition blocked this vasodilation, suggesting that it was mediated by dilator prostaglandins. However, subsequent reactivity to U46619 was enhanced in hypoxic alkalotic lungs, and both hypoxia and U46619 caused significant vasoconstriction in normoxic alkalotic lungs.

CONCLUSIONS

Alkalosis caused sustained vasodilation when pulmonary vascular resistance was high but either failed to attenuate or enhanced vascular reactivity to subsequent pressor stimuli.

Maturational changes in ovine pulmonary vascular responses to inhaled nitric oxide

Developmental changes in modulation of pulmonary vasomotor tone by endothelium-derived nitric oxide (EDNO) may reflect maturational differences in endothelial synthesis of and/or vascular smooth muscle response to nitric oxide. This study sought to determine whether pulmonary vascular sensitivity and responsiveness to nitric oxide change during newborn development, and whether this is related to changes in guanylate cyclase activity. Pulmonary artery dose-responses to inhaled nitric oxide (iNO, 0.25-100 parts per million) were measured in hypoxic, indomethacin-treated, isolated lungs from 1-day (1-d)- and 1-month (1-m)-old lambs. The lungs of 1-m-old lambs were ventilated with 4% (oxygen) O2, and lungs of 1-d-old lambs were ventilated with either 4% or 7% O2 in order to achieve similar stimuli or vasomotor tone. Cyclic guanosine monophosphate (cGMP) concentrations in the perfusate were measured at iNO concentrations of 0, 5, and 100 parts per million (ppm). Basal and stimulated pulmonary guanylate cyclase activity was also measured in lung extracts in vitro. The effects of iNO were similar in both 1-d groups, even though baseline hypoxic tone was significantly higher in 1-d lungs ventilated with 4% O2 than with 7% O2. Furthermore, both the 1-d 7% O2 and 1-d 4% O2 lungs exhibited greater responsiveness and sensitivity to iNO than 1-m lungs. Perfusate cGMP concentrations and soluble guanylate cyclase activity were higher under stimulated than basal conditions, but neither differed statistically between 1 d and 1 m. These data suggest that pulmonary vascular responsiveness and sensitivity to nitric oxide decrease with age, but the mechanisms underlying these maturational changes require further investigation.

Mediators of alkalosis-induced relaxation in pulmonary arteries from normoxic and chronically hypoxic piglets

Alkalosis-induced relaxation was measured in precontracted arterial rings from 1-wk-old piglets exposed to normoxia or to 3 days of chronic hypoxia. In normoxic piglet arteries, alkalosis-induced relaxation was blunted in arteries without functional endothelium and in arteries treated with nitric oxide synthase or guanylate cyclase inhibitors but not in arteries treated with cyclooxygenase inhibitors or Ca2+- and ATP-dependent K+-channel inhibitors. Inhibition of voltage-dependent K+ channels with 10(-3) M 4-aminopyridine also failed to block alkalosis-induced relaxation. 4-Aminopyridine at 10(-2) M did block the response, but this may have been due to sustained vascular smooth muscle depolarization. Arteries from hypoxic piglets exhibited greater contraction to the thromboxane mimetic U-46619, decreased endothelium-dependent relaxation, and blunted alkalosis-induced relaxation. The residual relaxation was eliminated by nitric oxide synthase but not by cyclooxygenase or voltage-dependent K+-channel inhibition. Alkalosis-induced relaxation of newborn piglet pulmonary arteries appears to be mediated by the nitric oxide-cGMP pathway and is attenuated after 3 days of hypoxia, likely because of decreased nitric oxide activity.

Developmental changes in synthesis of and responsiveness to prostaglandins I2 and E2 in hypoxic lamb lungs

Previous studies have shown that the attenuated hypoxic pulmonary vasoconstriction (HPV) of young newborn lamb lungs was enhanced by cyclooxygenase inhibition. We sought to determine whether this reflected greater synthesis of and (or) responsiveness to dilator prostaglandins (PG). Protocol 1 measured responses to graded hypoxia and perfusate concentrations of 6-keto-PGF1alpha (the stable metabolite of PGI2) and PGE2 in isolated lungs from 1-day- and 1-month-old lambs. Protocol 2 compared dose responses and segmental vascular resistances during infusion of PGI2 and PGE2 in hypoxic, cyclooxygenase-inhibited, lungs from 1- to 2-day-old and 1- to 3-month-old lambs. Lungs of 1-day-old lambs with attenuated responses to 4% O2 had significantly higher perfusate concentrations of 6-keto-PGF1alpha and PGE2, but responses to both PGE2 and the more potent vasodilator, PGI2 did not differ with age. These data support the hypothesis that attenuated HPV in young newborn lamb lungs is due to increased synthesis of dilator PG, particularly PGI2.

Developmental changes in synthesis of and responsiveness to prostaglandins I2 and E2 in hypoxic lamb lungs

Previous studies have shown that the attenuated hypoxic pulmonary vasoconstriction (HPV) of young newborn lamb lungs was enhanced by cyclooxygenase inhibition. We sought to determine whether this reflected greater synthesis of and (or) responsiveness to dilator prostaglandins (PG). Protocol 1 measured responses to graded hypoxia and perfusate concentrations of 6-keto-PGF1alpha (the stable metabolite of PGI2) and PGE2 in isolated lungs from 1-day- and 1-month-old lambs. Protocol 2 compared dose responses and segmental vascular resistances during infusion of PGI2 and PGE2 in hypoxic, cyclooxygenase-inhibited, lungs from 1- to 2-day-old and 1- to 3-month-old lambs. Lungs of 1-day-old lambs with attenuated responses to 4% O2 had significantly higher perfusate concentrations of 6-keto-PGF1alpha and PGE2, but responses to both PGE2 and the more potent vasodilator, PGI2 did not differ with age. These data support the hypothesis that attenuated HPV in young newborn lamb lungs is due to increased synthesis of dilator PG, particularly PGI2.Key words : hypoxic pulmonary vasoconstriction, pulmonary vascular development, cyclooxygenase inhibition, segmental vascular resistances.