Pulmonary arterial changes in patients with ventricular septal defects and severe pulmonary hypertension

Commercial Air Travel for Passengers With Cardiovascular Disease: Recommendations for Less Common Conditions, Considerations for Venous Thromboembolism, and General Guidance

The accelerated growth of commercial flights has resulted in a huge upswing of air travelers over the last few decades, including passengers with a wide range of cardiovascular conditions. Notwithstanding the ongoing COVID-19 pandemic that has set back the aviation industry for the next 1-2 years, air travel is expected to rebound fully by 2024. Guidelines and evidence-based recommendations for safe air travel in this group vary, and physicians often encounter situations where opinions and assessments on fitness for flights are sought. This article aims to provide an updated suite of recommendations for the aeromedical disposition of passenger with uncommon cardiovascular conditions, such as congenital heart diseases, inflammatory cardiac conditions (endocarditis/pericarditis/myocarditis), pulmonary hypertension, and venous thromboembolism. In addition, the article also aims to provide practical general guidance for the aeromedical examiner in evaluating, preparing, and optimizing the cardiac status of the patient with cardiovascular ailments for air travel.

Implication of in vivo circulating fibrocytes ablation in experimental pulmonary hypertension murine model

BACKGROUND AND PURPOSE

Recruitment and involvement of bone-/blood-derived circulating fibrocytes (CF) in the promotion of fibrotic tissue remodelling processes have been shown. However, their direct contribution to pathological changes is not clear. The present study investigates the causal role of CF in the pathogenesis of pulmonary hypertension (PH).

EXPERIMENTAL APPROACH

For selective ablation of CF, we applied the suicidal gene strategy with herpes simplex virus thymidine kinase (HSV-TK) and ganciclovir. The transgenic mice were generated, having HSV-TK-GFP transgene under the collagen 1 promoter. To selectively target CF, HSV-TK-GFP+ bone marrow transplanted into irradiated wild type mice. These chimera mice were subjected to hypoxia for PH induction and ganciclovir for CF ablation.

KEY RESULTS

In vivo CF ablation reduced right ventricular hypertrophy and vascular remodelling with reduced total collagen content. We quantified the CF recruited in the perivascular area and arterial wall of small pulmonary arteries. There was significant recruitment of CF in the lung in response to hypoxia. The characterization of CF showed the expression of CD45 and collagen1 (GFP) along with α-smooth muscle actin (αSMA).

CONCLUSION AND IMPLICATIONS

Our data demonstrated that CF ablation has a potential impact on right ventricular hypertrophy and vascular remodelling in the setting of experimental pulmonary hypertension induced by hypoxia. The beneficial effects may be related to the direct contribution of fibrocytes or its paracrine effect on other resident cell types. Thus, clinical manipulation of CF may represent a novel therapeutic approach to ameliorate the disease state in pulmonary hypertension.

Outcomes of infants and children undergoing surgical repair of ventricular septal defect: a review of the literature and implications for research with an emphasis on pulmonary artery hypertension

BACKGROUND

Pulmonary vascular disease resulting from CHDs may be the most preventable cause of pulmonary artery hypertension worldwide. Many children in developing countries still do not have access to early closure of clinically significant defects, and the long-term outcomes after corrective surgery remain unclear. Focused on long-term results after isolated ventricular septal defect repair, our review sought to determine the most effective medical therapy for the pre-operative management of elevated left-to-right shunts in patients with an isolated ventricular septal defect.

METHODS

We identified articles specific to the surgical repair of isolated ventricular septal defects. Specific parameters included the pathophysiology and pre-operative medical management of pulmonary over-circulation and outcomes.

RESULTS

Studies most commonly focused on histologic changes to the pulmonary vasculature and levels of thromboxanes, prostaglandins, nitric oxide, endothelin, and matrix metalloproteinases. Only 2/44 studies mentioned targeted pharmacologic management to any of these systems related to ventricular septal defect repair; no study offered evidence-based guidelines to manage pulmonary over-circulation with ventricular septal defects. Most studies with long-term data indicated a measurable frequency of pulmonary artery hypertension or diminished exercise capacity late after ventricular septal defect repair.

CONCLUSION

Long-term pulmonary vascular and respiratory changes can occur in children after ventricular septal defect repair. Research should be directed at providing an evidenced-based approach to the medical management of infants and children with ventricular septal defects (and naturally all CHDs) to minimise consequences of pulmonary artery hypertension, particularly as defect repair may occur late in underprivileged societies.

Can pulmonary vasodilator therapy expand the operative indications for congenital heart disease?

The operability of congenital heart disease with left to right shunt depends on the severity of the pulmonary vascular disease induced by the increased pulmonary blood flow. Although some recommendations exist regarding operative indications according to pathological, hemodynamic, and epidemiological factors, the evidence underlying these recommendations is not conclusive. Recently, oral pulmonary vasodilator therapy has been reported to improve outcomes in patients with idiopathic pulmonary arterial hypertension, and this therapy also appears to be effective in patients with congenital heart disease and pulmonary arterial hypertension, including those with postoperative pulmonary hypertension and Eisenmenger syndrome. It is expected that the availability of novel pulmonary vasodilator therapy will expand the operative indications in patients with congenital heart disease with left to right shunt, but there is currently insufficient evidence to definitively determine this. A multicenter double-blind study should be conducted to further examine this issue.

Do preoperative haemodynamic data and reactivity test predict the postoperative reversibility of pulmonary arterial hypertension in patients with large ventricular septal defect and borderline operability?

BACKGROUND

Decisions to operate on patients with shunt lesions presenting late with severe pulmonary arterial hypertension (PAH) and borderline operability are often not based on precise cut off values of haemodynamic data owing to paucity of studies.

OBJECTIVE

To assess the reliability of the preoperative haemodynamic data and reactivity test in predicting the postoperative reversibility of PAH in patients with isolated large ventricular septal defects (VSDs) and borderline operability.

PATIENTS AND METHOD

Between 2004 and 2010, 30 patients underwent VSD closure surgically; no early deaths occurred. Twenty-six patients were followed up regularly (mean 39.6±16 months) and one late postoperative death occurred. Fourteen patients who had been followed up for at least 1 year postoperatively underwent cardiac catheterisation.

RESULTS

There were 3 responders (asymptomatic patients with pulmonary vascular resistance (PVR) index <3 WU.m(2)) and 12 non-responders. The following were lower among responders: mean age at surgery (3.2±0.42 vs 11.55±3.29 years, p=0.227), mean baseline PVR index (3.69±0.8 vs 10.57±9.1, p=0.204), average resistance ratio (RR=0.25±0.01 vs 0.59±0.25, p=0.049) and ratio of pulmonary and systemic mean pressures (PAm:SAm ratio) (0.70±0.009 vs 0.87±0.118, p=0.003).

CONCLUSIONS

Preoperative 'base line' PAm:SAm and RR appear to be better predictors of postoperative outcome than other baseline parameters. Preoperative reactivity test had no significant role in predicting postoperative reversibility of PAH at mid-term.

A process-based review of mouse models of pulmonary hypertension

Genetically modified mouse models have unparalleled power to determine the mechanisms behind different processes involved in the molecular and physiologic etiology of various classes of human pulmonary hypertension (PH). Processes known to be involved in PH for which there are extensive mouse models available include the following: (1) Regulation of vascular tone through secreted vasoactive factors; (2) regulation of vascular tone through potassium and calcium channels; (3) regulation of vascular remodeling through alteration in metabolic processes, either through alteration in substrate usage or through circulating factors; (4) spontaneous vascular remodeling either before or after development of elevated pulmonary pressures; and (5) models in which changes in tone and remodeling are primarily driven by inflammation. PH development in mice is of necessity faster and with different physiologic ramifications than found in human disease, and so mice make poor models of natural history of PH. However, transgenic mouse models are a perfect tool for studying the processes involved in pulmonary vascular function and disease, and can effectively be used to test interventions designed against particular molecular pathways and processes involved in disease.

Activation of endothelin-1 receptor signaling pathways is associated with neointima formation, neoangiogenesis and irreversible pulmonary artery hypertension in patients with congenital heart disease

BACKGROUND

It is unclear why some patients, who undergo complete repair or palliative surgery for congenital heart disease (CHD), still develop irreversible pulmonary artery hypertension (PAH). There is no consensus to preoperationally assess the reversible and irreversible pulmonary vasculopathy seen in PAH.

METHODS AND RESULTS

The peri-operative pulmonary hemodynamic data of 16 CHD patients (reversible PAH, n = 6; irreversible PAH, n = 10) were analyzed. The lung biopsies were also performed during surgery for defining histopathological characteristics as well as immunohistochemical expression of endothelin-1 (ET-1), endothelin-1 receptors (ETR), and its downstream signaling markers in the small pulmonary arteries and arterioles. Neointimal formation and neoangiogenesis was characterized by increased intimal layer immunoreactivity for α-SMA, Factor VIII, CD34, and VEGF. Neointimal formation was found in 90% of patients and neoangiogenesis was found in 80% of patients with irreversible PAH. Neither was present in the reversible PAH group and the control group. Expression of ET-1 and ETR in the neointimal layer of the pulmonary arterioles was upregulated in irreversible PAH, and immunoreactivity of phospho-Akt, phospho-ERK1/2, and phospho-mTOR was also increased in irreversible PAH.

CONCLUSIONS

Increased expression of ET-1, ETR, and activation of signaling pathways were observed in the pulmonary arteries and arterioles of irreversible PAH patients associated with CHD. Activation of these pathways might in turn lead to neointimal formation and neoangiogenesis and thus might contribute to irreversible pulmonary vascular abnormalities.

Pulmonary arterial remodeling induced by a Th2 immune response

Pulmonary arterial remodeling characterized by increased vascular smooth muscle density is a common lesion seen in pulmonary arterial hypertension (PAH), a deadly condition. Clinical correlation studies have suggested an immune pathogenesis of pulmonary arterial remodeling, but experimental proof has been lacking. We show that immunization and prolonged intermittent challenge via the airways with either of two different soluble antigens induced severe muscularization in small- to medium-sized pulmonary arteries. Depletion of CD4(+) T cells, antigen-specific T helper type 2 (Th2) response, or the pathogenic Th2 cytokine interleukin 13 significantly ameliorated pulmonary arterial muscularization. The severity of pulmonary arterial muscularization was associated with increased numbers of epithelial cells and macrophages that expressed a smooth muscle cell mitogen, resistin-like molecule alpha, but surprisingly, there was no correlation with pulmonary hypertension. Our data are the first to provide experimental proof that the adaptive immune response to a soluble antigen is sufficient to cause severe pulmonary arterial muscularization, and support the clinical observations in pediatric patients and in companion animals that muscularization represents one of several injurious events to the pulmonary artery that may collectively contribute to PAH.

Flap Valve Double Patch Closure of Ventricular Septal Defects in Children With Increased Pulmonary Vascular Resistance

BACKGROUND

Closure of a large ventricular septal defect (VSD) in children with elevated pulmonary vascular resistance (PVR) is associated with significant morbidity and mortality. Sophisticated medications and circulatory assist devices may not be available to assist in the care of children with elevated PVR undergoing VSD closure. We designed a fenestrated flap valve double VSD patch to decrease the morbidity and mortality associated with the closure of a large VSD in this high-risk group.

METHODS

Ninety-one children (median age 4.0 +/- 3.1 years) with a large VSD and elevated PVR (10.5 +/- 4.9 Wood units) underwent double patch VSD closure. The routine VSD patch was fenestrated (4 to 8 mm), and on the left ventricular side of the patch, a second smaller patch was attached to the upper third of the fenestration before VSD patch placement.

RESULTS

Fifty-six children with a VSD as the primary lesion, 16 with complete atrioventricular canal, 10 with double outlet right ventricle/VSD, 2 with interrupted aortic arch/VSD, 2 with truncus arteriosus, and 1 each with transposition/VSD, corrected transposition/VSD, total anomalous pulmonary venous connection/VSD, VSD/left pulmonary artery atresia, and aortopulmonary window underwent operation; the overall early mortality rate was 7.7% (7 of 91). There have been 7 late deaths: 2 VSD and 5 complex defects.

CONCLUSIONS

Closure of a large VSD with elevated PVR can be performed with reasonable mortality and morbidity.

Open-lung biopsy guides therapy in children

BACKGROUND

Open-lung biopsy is uncommon in children. Modern indications and outcomes are unknown.

METHODS

This is a retrospective review of 64 open-lung biopsies (58 patients) from 1976 to 1996. Open-lung biopsies were used to grade vasculopathy in 8 patients (12% of 64) with pulmonary hypertension and in 10 patients (16% of 64) with combined pulmonary hypertension and lung parenchymal disease. Forty-six biopsies (72%) were obtained to diagnose parenchymal disease. Comparisons were made between biopsies performed from 1976 to 1989 and from 1990 to 1996.

RESULTS

In the period 1990 to 1996, there were significantly more infants (p = 0.03), comorbid disease (p = 0.009), extracorporeal membrane oxygenation support (p < 10(-4)), and ventilator dependence (p = 0.05) and significantly less immunocompromise (p = 0.04). A definitive diagnosis was made in 43 of 64 cases (67%) and altered workup in 63 of 64 cases (98%). No correlation existed between Heath-Edwards grade of microangiopathy and catheterization data. Definitive diagnosis was most strongly associated with a nonimmunocompromised patient (p < 10(-4)). Although only one death (1.5%) was related to open-lung biopsy, the procedure was associated with a 30% inhospital mortality rate and an 11% morbidity rate. Of the 19 deaths, 1 patient died from the procedure, 13 died from their diseases, and 5 had support withdrawn. Death was associated with preoperative ventilator dependence (p < 10(-4)) and extracorporeal membrane oxygenation (p = 0.007).

CONCLUSIONS

Pediatric open-lung biopsy commonly alters the diagnostic workup (98%). It is recommended for children who have been supported for 2 weeks by extracorporeal membrane oxygenation and for those with combined pulmonary hypertension and parenchymal lung disease. It is less useful in immunocompromised children.

Sudden death due to ventricular septal defect

Ventricular septal defects (VSD) are usually considered non-life-threatening, usually closing spontaneously or causing symptoms of congestive heart failure, which can be surgically treated in time to save the patient's life. Despite the usually benign clinical course of VSD, serious arrhythmias occur in 16-31% of patients. Sudden death accounted for one-third of all deaths in a series of medically managed patients and occurred in 4.2% of patients in a study of VSD and arrhythmias. Cardiac hypertrophy is the common denominator in all cases reported in detail of VSD-associated sudden death. We have encountered four cases of sudden unexpected death from VSD in infants ranging in age from 1 week to 3 and (1/2) months. In each case there was cardiomegaly and in one case there was pulmonary arteriolar medial thickening, with extension of smooth muscle into small intralobular vessels. In half of our cases the attending physician was sued for malpractice. We believe that VSD in infants and young children are potentially life-threatening malformations which warrant careful clinical follow-up.

Double patch closure of ventricular septal defect with increased pulmonary vascular resistance

BACKGROUND

Closure of a large ventricular septal defect (VSD) in children with elevated pulmonary vascular resistance is associated with significant morbidity and mortality. Pulmonary hypertensive episodes continue to be a major cause of postoperative morbidity and mortality. We designed a fenestrated flap valve double VSD patch in an effort to decrease the morbidity and mortality associated with the closure of a large VSD with elevated pulmonary vascular resistance.

METHODS

Eighteen children (mean age, 5.7 years) with a large VSD and elevated pulmonary vascular resistance (mean, 11.4 Wood units) underwent double patch VSD closure using moderately hypothermic cardiopulmonary bypass and cardioplegic arrest. The routine VSD patch was fenestrated (4 to 6 mm) and on the left ventricular side of the patch, a second, smaller patch was attached to the fenestration along its superior margin before closure of the VSD.

RESULTS

All children survived operation and were weaned from inotropic and ventilator support within 48 hours postoperatively. Postoperative pulmonary artery pressures were significantly lower than preoperative values. One child died 9 months postoperatively.

CONCLUSIONS

Closure of a large VSD in children with elevated pulmonary vascular resistance can be performed with low morbidity and mortality when a flap valve double VSD patch is used.

Intravascular ultrasonic characteristics and vasoreactivity of the pulmonary vasculature in children with pulmonary hypertension

We sought to describe the morphologic characteristics of pulmonary arteries by intravascular ultrasound (IVUS) in children with and without pulmonary hypertension to compare these anatomic findings with those of pulmonary wedge angiography, and to determine the relation between these structural findings and functional reactivity to pulmonary vasodilators. Direct evaluation of pulmonary vascular structure in children with pulmonary hypertension with current imaging techniques has been limited and little is known about the relation between structural and functional characteristics of the pulmonary vasculature. In 23 children undergoing cardiac catheterization (15 with pulmonary hypertension and 8 controls) we performed IVUS and pulmonary wedge angiography of the distal pulmonary arteries in the same lobe. IVUS was performed in 44 pulmonary arteries measuring 2.5 to 5.0 mm internal diameter with a 3.5Fr 30-MHz IVUS catheter. We assessed vasoreactivity to inhaled nitric oxide (NO) and oxygen in 13 of 15 children with pulmonary hypertension. Baseline pulmonary vascular resistance (PVR) was greater in the 15 children with pulmonary hypertension than in the 8 controls (9.5+/-1.9 vs 1.5+/-0.3 U x m2, p <0.05). NO lowered PVR in patients with pulmonary hypertension (p <0.05). IVUS studies in patients with pulmonary hypertension showed a thicker middle layer, wall thickness ratio, and diminished pulsatility than did those in controls (p <0.05). The inner layer was not visualized by IVUS in any control patient, but was seen in 9 of 15 patients with pulmonary hypertension. Pulmonary artery wedge angiography correlated with baseline mean pulmonary artery pressure and PVR as well as with IVUS findings of wall thickness ratio and inner layer thickness. The inner layer was not visualized by IVUS in any patient with grade 1 wedge angiograms or in 86% of patients with grade 2 wedge angiograms. All patients with grade 4 and 80% of patients with grade 3 wedge angiograms had a visible inner layer. Vasoreactivity to NO and oxygen did not correlate with structural assessment of the pulmonary vasculature by IVUS. Structural changes in the pulmonary arteries in children with pulmonary hypertension can be directly visualized by IVUS, but are not predictive of NO-induced pulmonary vasodilation. IVUS examination of pulmonary arteries may complement current techniques utilized in the evaluation of children with pulmonary hypertension.

Lung function in VSD patients after corrective heart surgery

Static lung volumes, lung elasticity, and airway patency indices were measured in 47 children operated on for ventricular septal defect (VSD). Open-heart surgery was performed at the age of 0.6-12.0 years (median 4.1 years). In the first group (34 subjects), after primary repair of the VSD, there was an increase in lung recoil pressure at 100% of total lung capacity (TLC) (128% of the predicted value) and a reduction in specific airway conductance (sGaw) (75% of the predicted value). In the second group (13 patients), who had had previous pulmonary artery banding at 0.2-4.0 years (median 0.7 year) there was an increased functional residual capacity/TLC ratio (111% of predicted value), reduced sGaw (69% of predicted value), and reduced maximum expiratory flow at 25% of vital capacity (79% of predicted value). Lung volumes were insignificantly reduced in both groups. The frequency of lung function disturbances was similar in the two groups (71% of patients in the former group and 77% of patients in the latter group). A linear positive correlation between specific airway conductance and the mean pulmonary artery pressure (mPAP) (r = 0.793, p < 0.006) was observed in children with an mPAP <30 mmHg prior to open-heart surgery. A positive correlation between static recoil pressure at full inflation and mPAP (r = 0.545, p < 0.03) was found in children with an mPAP > 30 mmHg. The severity of congenital heart disease prior to surgery and the influence of the timing of the surgical procedures may cause the differences in lung function tests between the groups.

Pulmonary wedge angiography for prediction of pulmonary vascular disease in Down syndrome

We performed high resolution pulmonary wedge angiography (PWA) and conventional hemodynamics to predict the reversibility of structural pulmonary vascular disease. Sixty-one pulmonary wedge angiograms were performed on 41 patients with intracardiac shunts and Down syndrome (median age 8 months). Balloon occlusion wedge angiograms were analyzed for (1) monopedial branches from the distal 10 mm of muscular arteries, (2) capillary blush, (3) tapering indices, and (4) tortuosity. Twenty-five patients had open lung biopsy, graded by the Health Edwards classification, and analyzed morphometrically. Pulmonary vascular resistance of > or = 6 units was 100% sensitive and 94% specific for Heath Edwards Grade III-IV. A monopedial count < 3 vessels was 83% sensitive and 100% specific for Heath Edwards Grade III-IV. Abnormal capillary blush was 83% sensitive and 69% specific for Heath Edwards Grade III-IV. Tapering indices and tortuosity showed no significant correlation with lung biopsy. A combination of pulmonary vascular resistance < 6 units, monopedial count > or = 3, and normal capillary blush was 100% sensitive and specific for Heath Edwards Grade 0-II, and a combination of pulmonary vascular resistance > or = 6 units, monopedial count < 3, and abnormal capillary blush was 100% sensitive and specific for Heath Edwards Grade III-IV. Using the 3 criteria, Heath Edwards Grade was accurately predicted in 17 patients. In 4 patients, only 2 criteria were available. Morphometric analysis showed an inverse relationship between the lowest monopedial count and the number of occlusive vessels per cm of tissue, r = -0.74 p < 0.001. Arteries showing intimal and/or medial thickening causing > 90% luminal narrowing were scored as "occlusive." These results show that when the hemodynamic and pulmonary wedge angiography data are concordant, the structural changes of pulmonary vascular disease can be accurately predicted and lung biopsy may be avoided.

Correlations of lung morphology, pulmonary vascular resistance, and outcome in children with congenital heart disease

Pulmonary vascular resistance was measured in air, oxygen, and after administration of vasodilators in 14 children with pulmonary hypertension and congenital heart disease. Lung morphology was examined by light microscopy and assessed quantitatively. In this selected group of patients (a) medial muscle thickness of greater than 20% in the intra-acinar arteries and Heath-Edwards changes of I or II were significantly associated with perioperative death from pulmonary complications after cardiac surgery; (b) children with lower percentage medial muscle thickness had a higher baseline resistance (r = -0.84) associated with Heath-Edwards grade III or higher changes (most of these patients were not offered corrective surgery); (c) when the lowest pulmonary vascular resistance was less than 3 units, Heath-Edwards grading was I or II (n = 4). When the pulmonary vascular resistance was greater than 6 units, however, there was no direct correlation with Heath-Edwards grading (n = 9). Four patients with a resistance of greater than 6 units had only grade I or II changes. Three had a medial muscle thickness above 20%, and were among those who died at or soon after operation. It is concluded that (a) patients with a lowest pulmonary vascular resistance of greater than 6 units have a bad prognosis whatever their lung morphology; and (b) some patients with Heath-Edwards grade I or II will have a high resistance (this group has a high medial muscle mass and a poor prognosis and would not be detected by Heath-Edwards grading alone).