Medical therapy for pulmonary arterial hypertension

When to initiate intravenous therapy and/or refer

Intravenous (IV) prostacyclin (epoprostanol) and its analogs (iloprost and treprostinil) are effective in treating pulmonary artery hypertension (PAH). Although prostacyclins are available for inhaled and subcutaneous delivery, IV administration of prostacyclins, sometimes in combination with other agents, such as bosentan or sildenafil, is considered the most aggressive method to manage PAH. This report attempts to help clinicians determine when to initiate IV treatment of PAH and when to refer a patient with PAH to a center for treatment. IV prostacyclin therapy initiation is suggested when patients exhibit World Health Organization functional class IV symptoms. The Registry to EValuate Early And Long-term Pulmonary Arterial Hypertension disease management (REVEAL) risk calculator can help determine a patient's 1-year mortality with PAH and characterize the clinical course, treatment, and predictors of outcomes in patients with PAH. Referring physicians can screen their patients for PAH and refer even before the diagnosis has been confirmed so that the center can facilitate the diagnostic process and provide suggestions for initial therapy selection and provide other collaborative and supportive services. Alternatively, the physician can diagnose and initiate early therapy with a plan to involve the pulmonary hypertension center at the need for IV therapy or consideration for transplantation, working closely with the patient to ensure stability. Physicians and pulmonary centers must develop good methods of communication to ensure effective diagnosis and management.

Targeted oral therapies in the treatment of pulmonary arterial hypertension

Recent advances in our understanding of the pathophysiology of pulmonary arterial hypertension (PAH) have led to the US FDA's approval of eight drugs for its treatment. Although guidelines for the use of PAH therapies are available and regularly updated, there is a lack of information on how these agents differ and what characteristics may enable one agent to be of greater relative clinical utility than another. Oral agents may be compared across a variety of measures, including clinical efficacy, safety and tolerability, dosing and pharmacology, potential for drug interactions, treatment adherence and suitability for use in combination regimens. Although no large, prospective, head-to-head trial has been conducted with oral agents for PAH, data from placebo-controlled studies indicate that the enrolled patient populations were remarkably homogeneous with respect to demographic and disease severity parameters. In general, data suggest that these agents improve functional capacity, delay disease progression and improve haemodynamics. Additionally, long-term sustainability of response has been demonstrated. However, there was no consistently superior agent across the primary and secondary endpoints assessed in these trials, and the magnitudes of improvements were in a fairly defined range across agents. Consequently, treatment choice may shift to other aspects such as drug safety and tolerability, potential for drug interactions, dosing convenience, treatment adherence, effect on quality of life and access to medication. In this review, the four targeted oral agents approved for the treatment of PAH in the US are reviewed, and clinical results are placed into context.

Etiology, diagnosis, and pharmacologic treatment of pediatric pulmonary hypertension

Major advances have been made in the understanding and treatment of pulmonary hypertension in the last few years. Without treatment (medication) for idiopathic pulmonary arterial hypertension, which is a rare and potentially fatal condition, the survival time is only about 3 years after diagnosis. However, if pulmonary hypertension is secondary to other causes such as congenital heart disease, it is possible to survive for 30 years or more without treatment. The condition can affect children at any age, from fetal life to adulthood. Patients with pulmonary hypertension can present to the respiratory pediatrician with unresponsive asthma, to the neurologist with faints, or to the general pediatrician with failure to thrive. Over the last few years there have been significant developments in the available therapy for managing this complicated disease. There is now a generally recognized ladder of long-term therapy for chronic pulmonary hypertension. Treatment can start with oxygen at home at night or even during the day. Next is the use of oral phosphodiesterase inhibitors, mostly type V, such as sildenafil, which enhance endogenous nitric oxide. More potent are the endothelin receptor antagonists and the most potent are the prostanoids, especially epoprostenol, which is given by constant intravenous infusion. In addition to interventional catheterization with atrial septostomy, these agents have improved the prognostic outlook. This article reviews the current knowledge about the etiology, investigation, and treatment of children with pulmonary hypertension in the clinical setting.

Treatment of pediatric pulmonary hypertension

Pulmonary hypertension was once thought to be a rare condition and only managed in specialized centers. Now however, with the advent of echocardiography, it is found in many clinical scenarios, in the neonate with chronic lung disease, in the acute setting in the intensive care unit, in connective tissue disease and in cardiology pre- and postoperatively. We have a better understanding of the pathological process and have a range of medication which is starting to be able to palliate this previously fatal condition. This review describes the areas that are known in this condition and those that are less familiar. The basic physiology behind pulmonary hypertension and pulmonary vascular disease is explained. The histopathologic process and the various diagnostic tools are described and are followed by the current and future therapy at our disposal.

Cyclic GMP signaling in cardiovascular pathophysiology and therapeutics

Cyclic guanosine 3',5'-monophosphate (cGMP) mediates a wide spectrum of physiologic processes in multiple cell types within the cardiovascular system. Dysfunctional signaling at any step of the cascade - cGMP synthesis, effector activation, or catabolism - have been implicated in numerous cardiovascular diseases, ranging from hypertension to atherosclerosis to cardiac hypertrophy and heart failure. In this review, we outline each step of the cGMP signaling cascade and discuss its regulation and physiologic effects within the cardiovascular system. In addition, we illustrate how cGMP signaling becomes dysregulated in specific cardiovascular disease states. The ubiquitous role cGMP plays in cardiac physiology and pathophysiology presents great opportunities for pharmacologic modulation of the cGMP signal in the treatment of cardiovascular diseases. We detail the various therapeutic interventional strategies that have been developed or are in development, summarizing relevant preclinical and clinical studies.

Ambrisentan

Elevated endothelin (ET)-1 levels are strongly correlated with the pathogenesis and prognosis of pulmonary arterial hypertension (PAH). Ambrisentan is an orally active, highly selective ETA receptor antagonist with >4000-fold higher selectivity over the ETB receptor. In two large, well designed, 12-week, placebo-controlled, phase III trials (ARIES-1, n = 202 and ARIES-2, n = 192) in patients with PAH (WHO group I), ambrisentan 2.5-10 mg once daily significantly increased 6-minute walk distance by 31-59 m from baseline (primary outcome measure) versus placebo. The incidence of clinical worsening (secondary outcome measure) was significantly delayed for the combined ambrisentan 5 mg once daily groups versus the combined placebo groups from ARIES-1 and -2. At week 12, WHO functional class distribution was significantly improved with once-daily ambrisentan 5 mg, and Borg dyspnoea scores were significantly improved with ambrisentan 2.5-10 mg versus placebo in combined data from the ARIES-1 and -2 trials. The beneficial effects of ambrisentan on exercise capacity, WHO functional class and Borg dyspnoea scores seen at 12 weeks were maintained at 48 weeks in the ARIES-E phase III extension trial (n = 361). One-year survival rates with ambrisentan were 95-97%. Treatment with ambrisentan for up to 2.8 years was generally well tolerated in clinical trials.