The role of increased pulmonary blood flow in pulmonary arterial hypertension.

Chronic increased pulmonary blood flow is considered a pre-requisite for the induction of advanced vascular lesions in pulmonary arterial hypertension in congenital heart defects. The aim of the present study was to characterise the effects of increased pulmonary flow induced by an aortocaval shunt in the monocrotaline rat model for pulmonary hypertension in terms of survival, haemodynamics, pathology and histology. Male Wistar rats were injected with monocrotaline followed by the creation of an abdominal aortocaval shunt. Animals were sacrificed when displaying symptoms of weight loss or dyspnoea, 4-5 weeks after the creation of the shunt. Echocardiography identified increased ventricular dimensions in shunted rats and right ventricular hypertrophy in monocrotaline-treated rats. At similar pulmonary artery pressures, shunted monocrotaline rats displayed higher morbidity and mortality, increased pulmonary-to-systemic artery pressure ratios and increased right ventricular hypertrophy compared with nonshunted monocrotaline rats. Histological assessment demonstrated increased number and diameter of pre-acinar pulmonary arteries. Intra-acinar vessel remodelling and occlusion occurred to a similar extent in shunted and nonshunted monocrotaline rats. In conclusion, increased pulmonary blood flow in monocrotaline-induced pulmonary hypertension is associated with increased morbidity, mortality, and unfavourable haemodynamic and cardiac effects. These effects could be attributed to more pronounced right heart failure rather than to altered intra-acinar pulmonary vessel remodelling.

Coronary artery intimal thickening in the transplanted heart. An in vivo intracoronary untrasound study of immunologic and metabolic risk factors.

This study examined the hypothesis that immunologic factors are the major correlates of coronary artery intimal thickening and luminal stenosis. The study population included 116 adult heart transplant recipients with a mean age of 44.7 +/- 12.0 years (89 men and 27 women) undergoing annual coronary angiography and intracoronary ultrasound 3.4 +/- 2.7 (range, 1.0-14.6) years after transplantation. Mean intimal thickness was obtained from several distinct sites along the left anterior descending and/or left circumflex coronary artery by intracoronary ultrasound. Coronary artery stenosis defined by angiography was classified as mild (< 30% luminal stenosis), moderate (> or = 30-70% luminal stenosis), or severe (> 70% luminal stenosis or diffuse pruning of distal vessels). Prevalence of any transplant coronary artery disease (TxCAD) was 85% by intracoronary ultrasound and 15% by angiography. By multiple regression analysis, only average fasting plasma triglyceride level (P < 0.006) and average weight (P < 0.007) were significantly correlated with severity of intimal thickening (R = 0.54, P < 0.0001). Donor age (P < 0.006) and average fasting plasma triglyceride level (P < 0.009) were significantly correlated with stenosis by angiography. Correlation of multiple immunologic and metabolic factors with intimal thickness by univariate analysis suggests a multifactorial etiology for TxCAD. Among the multiple univariate correlates of TxCAD, higher fasting plasma triglyceride levels and body weight are the only independent correlates of TxCAD. The absence of acute rejection as an independent predictor of intimal thickening suggests that mechanisms beyond those mediating typical cellular rejection should be targeted for advancing our understanding of Tx-CAD.

Metabolic risk factors for atherosclerosis in heart transplant recipients.

Development of coronary artery disease (CAD) in the cardiac allograft limits long-term survival after heart transplantation. Previous studies, focusing on lipoprotein metabolism, have paid little attention to changes in glucose and insulin metabolism that increase the risk of CAD in these patients. To address this issue, plasma glucose and insulin responses to an oral glucose load and lipid and lipoprotein concentrations were measured in male normal volunteers (n = 40) and cardiac transplant recipients with pretransplant diagnoses of either idiopathic cardiomyopathy (n = 24) or ischemic heart disease (n = 28), matched for age and body mass index. Patients with a pretransplant diagnosis of ischemic heart disease had higher plasma glucose and insulin concentrations in response to oral glucose as well as higher fasting plasma triglyceride, cholesterol, and low-density lipoprotein cholesterol concentrations than did the control group (p < 0.005 to p < 0.001). In addition, high-density lipoprotein cholesterol concentrations were lower and the ratio of cholesterol to high-density lipoprotein cholesterol higher than control values in those with a pretransplant diagnosis of ischemic heart disease (p < 0.001). Values for almost all variables were intermediate in patients with a pretransplant diagnosis of idiopathic cardiomyopathy and in most instances were significantly different from both. Thus, male cardiac transplant recipients are dyslipidemic, relatively glucose intolerant, and hyperinsulinemic compared to normal volunteers. These changes, observed in patients with a pretransplant diagnosis of either ischemic heart disease or idiopathic cardiomyopathy, emphasize the important role of immunosuppression in the development of metabolic risk factors for CAD in these individuals.