Pulmonary arterial hypertension (PAH) is a disease where the blood pressure in the pulmonary arteries (PAP) is high. PAH increases the risk of adverse events, including death, during and or after procedures. The severity of baseline PAH correlates with the incidence of major complications, such that those with PAP higher than their systemic blood pressure (SBP) had a 8 fold increased risk of complications. These children present for procedures where an acute exacerbation of their chronic illness-termed Pulmonary Hypertensive (PH)crisis, can occur, often resulting in death if not detected and managed expeditiously. Unfortunately there is little data and no consensus in the pediatric literature on how PH crisis should be managed.

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Pulmonary arterial hypertension (PAH) is a disease where the blood pressure in the pulmonary arteries (PAP) is high. PAH increases the risk of adverse events, including death, during and or after procedures. The severity of baseline PAH correlates with the incidence of major complications, such that those with PAP higher than their systemic blood pressure (SBP) had a 8 fold increased risk of complications. These children present for procedures where an acute exacerbation of their chronic illness-termed PH crisis, can occur, often resulting in death if not detected and managed expeditiously. Unfortunately there is little data and no consensus in the pediatric literature on how PH crisis should be managed. Over the last 10 years we have developed considerable expertise in managing children with PAH and preventing and treating their acute crisis, using a medication called phenylephrine. This medication is routinely used to increase the blood pressure in patients (adults and children) to treat hypotension. Our theory has been that by increasing SBP, we can increase the blood flow to the coronary arteries and prevent the right ventricle from failing acutely. The latter results in catastrophic hypotension, heart arrythmias and death. There is no consensus or protocol guiding the management of the acute crisis. This purpose of this study is to close that gap.

Inclusion Criteria:

• Patients presenting for cardiac catheterization procedure with a diagnosis of PAH either by previous cardiac catheterization or echocardiography

Exclusion Criteria:

• Children presenting for cardiac catheterization who do not have PAH;
• Children with PAH but with intracardiac shunts

During procedure (approx. 5 h)