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Pulmonary Hypertension
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Best Method for Mx of PHTN is PREVENTION
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Conditions associated with PAH Acyanotic CHD Increased Pulmonary Blood Flow Cyanotic CHD Increased Pulm Blood Flow
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CLASSIFICATION OF CHD ACYANOTIC Increased PBF ATRIAL: ASD VENTR: VSD ARTERIAL: PDA COMBINED: VSD+PDA No Shunts Pulm or Aortic Stenosis CYANOTIC Decreased Flow TOF Pulm Atresia Increased Flow TAPVD TGA Truncus Tricuspid Atresia
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So what is the right time to operate in these conditions
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Timing of surgery: Acyanotic ASD: 2 years or later VSD Large: 3-6 months Moderate: when there is FTT Small: when there is AI or InfectiveEndocardiaits
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Acyanotic, when to operate PDA Infancy ALL PDA’S CAN BE CLOSED WITH DEVICE Neonatal Prematurity Closure by surgical ligation Full Term Wait for child to grow if possible
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ATRIAL SEPTAL DEFECT PRIMUM SINUS VENOSUS
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ATRIAL SEPTAL DEFECT-II
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ASD-DEVICE
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Acyanotic CHD Increased Pulmonary Blood Flow PRETRICUSPID SHUNT: RA RV DILATATION ATRIAL SEPTAL DEFECT POST TRICUSPID SHUNT: LA V DILATATION VENTRICULAR SEPTAL DEFECT PATENT DUCTUS ARTERIOSUS
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What is a Large, Moderate, Small VSD Effects of VSD PRESSURE EFFECT: Pulmonary Hypertension VOLUME EFFECT: Cardiac enlargement
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Pressure Effect: Types Flow Related PAH: Reversible Irreversible PAH due to permanent Changes
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Flow Related PAH Increased Flow Increased Pressure When you remove the extra flow ie close the VSD, the Pulmonary Pressure comes back to normal
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Flow related PAH (Pre/Post Tricuspid Shunt) Symptoms of increased Flow Tachypnea, Rec infections, failure to thrive Signs Tachycardia, Harrison’s sulcus, retractions X-ray Cardiac enlargement, Increased Pulmonary Blood Flow
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Increased Flow PAH All these indicate Patient is operable with good results without post-op PAH
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Till when is this phase: Reversible PAH VSD-LARGE: UPTO 6 MONTHS PDA-LARGE: UPTO 6 MONTHS ASD: LARGE: UPTO LATER 4-8 YRS
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So, What is a Large Shunt Post tricuspid Large VSD/PDA Clinically PAH Present (Pressure Effect) Clinically Volume Effect Present (Cardiac Enlargement)
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Moderate Shunt No Pressure Effect But Volume Effect Present
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Small Shunt No Pressure or Volume Effect No Symptoms or Signs of increased flow
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So if the surgery is done at the right time it is likely the patient will not get pulmonary hypertension
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What Happens when Reversible PAH starts becoming Irreversible …the child shows some signs and these are signs of Post Op PAH
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Signs of Reversible to Irreversible PAH Symptoms: Start improving Less FTT Less Infectios Less tachypnea Signs: Murmur shorter, P2 Louder, Cardiac Enlargement less
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When Reversible Changing to Irreversible Patient still operable But the post op risks are more and episode of life threatening PAH in immediate post op period is high
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When Completely Irreversible Patient now has Eisenmanger’s Decreased Pulm Blood Flow Cyanosis starts Now risk of surgery more than living without surgery
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Chest Xrays Indicating Increased PBF w PAH ie operability
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VSD
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ASD
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MODERATE VSD
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LARGE VSD LARGE SHUNT
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AV CANAL
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TGA
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TRUNCUS
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EISENMANGERS
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Pulmonary Hypertension
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Classification Group 1 PAH Examples: "Pulmonary arterial hypertension". 1. Idiopathic (IPAH) 2. Familial (FPAH) 3. Associated with (APAH): Collagen vascular disease Congenital systemic-to-pulmonary shunts Portal hypertension HIV infection Drugs and toxins Other (thyroid disorders, glycogen storage disease, Gaucher disease, hereditary hemorrhagic telangiectasia, hemoglobinopathies, myeloproliferative disorders, splenectomy) 4. Associated with significant venous or capillary involvement Pulmonary veno-occlusive disease (PVOD) Pulmonary capillary hemangiomatosis (PCH) 5. Persistent pulmonary hypertension of the newborn
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Classification Group 2 PH — "Pulmonary venous hypertension". Examples: 1. Left-sided atrial or ventricular heart disease 2. Left-sided valvular heart disease Group 3 PH — "Pulmonary hypertension associated with disorders of the respiratory system or hypoxemia". Examples: 1. Chronic obstructive pulmonary disease 2. Interstitial lung disease 3. Sleep-disordered breathing 4. Alveolar hypoventilation disorders 5. Chronic exposure to high altitude 6. Development abnormalities
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Classification Group 4 PH — "Pulmonary hypertension caused by chronic thrombotic or embolic disease". Examples: 1. Thromboembolic obstruction of proximal pulmonary arteries 2. Thromboembolic obstruction of distal pulmonary arteries 3. Non-thrombotic pulmonary embolism (tumor, parasites, foreign material) Group 5 PH — These patients have PH caused by inflammation, mechanical obstruction, or extrinsic compression of the pulmonary vasculature (eg, sarcoidosis, histiocytosis X, lymphangiomatosis, compression of pulmonary vessels by adenopathy, and fibrosing mediastinitis).
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Histologically Speaking The above mechanisms all cause small muscular arteries and arterioles to undergo intimal hyperplasia and medial hypertrophy 1 Narrowed lumen Decreased cross-sectional area Increased resistance 1 - Though again with PPH likely primary process, rather than reactive
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PULMONARY VASODILATION HYPEROXIA HYPOCARBIA ALKALOSIS NON REM SLEEP SEDATED PARALYSED
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Basic 3 Mechanisms 2º pulmonary arterial hypertension: Reduced cross-sectional area of pulmonary vasculature, secondary to: Occlusion of vessels (e.g. emboli) Primary disease of pulmonary vasculature walls (e.g. 1º pulmonary hypertension, portal hypertension) Primary parenchymal disease (e.g. interstitial lung disease, emphysema) Vasoconstriction 2/2 hypoxia or acidosis Increased flow through pulmonary vascular bed secondary to left to right shunts Increased “back pressure” secondary to pulmonary venous hypertension
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3 types of abnormalities Maladaptation Maldevelopment Underdevelopment
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Maladaptation Prototype: Meconium aspiration pneumonia Pneumonia, RDS Obstruction of the airways Chemical pneumonitis Release of endothelin,thromboxane vasoconstrictors
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Maldevelopment Prototype: Idiopathic PPHN (“black lung” PPHN) Vessel wall thickening Smooth muscle hyperplasia Cause – intrauterine exposure to NSAID constriction of ductus arteriosus genetic
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Disruption of NO-cGMP pathway Disruption of PGI2-cAMP pathway Guanylate cyclase is less active Increased ROS (reactive oxygen species) vasoconstrictor Increased thromboxane, endothelin Maldevelopment
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Underdevelopment Prototype: Congenital diaphragmatic hernia Pulmonary hypoplasia Decreased cross sectional area of pulmonary vasculature Decreased pulmonary blood flow Abnormal muscular hypertrophy of the pulm arterioles
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MEDIATORS OF PULMONARY HYPERTENSION Prostacycline Thromboxane A2 Endothelin-1 Nitric Oxide (NO) Serotonin Adrenomedullin Vasoactive Intestinal Peptide (VIP) Vascular Endothelial Growth Factor (VEGF)
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ENDOTHELIN-1 Potent vasoconstrictor Stimulates proliferation of smooth muscle cells in PA Plasma levels increased in PHT Level inversely proportional to pulmonary blood flow & CO - ? Direct effect
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VASODILATORS Oxygen CCBs Endothelin-receptor antagonists BNP Calcitonin gene-related peptide
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Bosentas
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ENDOTHELIN RECEPTOR ANTAGONISTS Endothelin-1 overexpressed in PHT Improve pulmonary haemodynamics, exercise capacity, functional status, clinical outcomes Bosentas, sitaxentan and ambrisentan
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BOSENTAS Sulphonamide-based ET A & ET B receptor blocker Inducer of CYP2C9 - Vori/ fluconazole, warfarin, digoxin, simvastatin, tac/ sirolimus, sildenafil, OCP CYP3A4 – ketaconazole t½ 5.6 +/- 1.6 hours
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PHOSPHODIESTERASE INHIBITORS Sildenafil PDE type5 inhibitor Reduce metabolism of cGMP t½ 3-5 hours CYP3A4 & 2C9 substrate Concentration increased by concurrent bosentan – I/As nitrates Tadalafil t½ 17 hours CYP 3A4
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PROSTACYCLINE ANALOGUES Vasodilators Reduce R & L afterload & increase SV & CO Platelet aggregation inhibitors Main ADRs H/A and dizziness (~80%) Nausea and jaw pain
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PROSTACYCLINE ANALOGUES Iloprost IV or Inhaled I/As with CCBs, BBs and ACEIs (animal data) NO PK STUDIES FOLLOWING INHALATION!! t½ ~ 0.7 hours Treprostinol IV or s/c injection No CYP inhibition - ? induction t½ 2-4 hours
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Epoprostenol Continuous IV infusion F 0.2/ t½ 2-6 mins Spontaneous B/D to 6-oxo-prostaglandin F 1α
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WHERE TO NOW? PDE5 inhibitors & ERAs first line for 1 o PHT Increasing evidence that combination therapies are more effective (theoretical)
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Nitric Oxide Selective pulmonary vasodilation, improves oxygenation ↑ cGMP Used in ARDS, PPHN, cardiogenic shock, post CPB Risks: methemoglobinemia and carboxyhemoglobinemia, rebound pulm HTN when stopped Requires closed inhalational circuit
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Phosphodiesterase inhibitors Inhibition of nitric oxide degradation Sildenafil (PDE-5 inhibitor): ↓ PAP/PVR Min effects on systemic vasculature Synergistic with NO Reduction in RV mass: role in prevention or reversal of remodeling of RV Milrinone (PDE-3 inhibitor): ↓ PVR/PAP/SVR in setting of CV shock Nebulized minimizes systemic vasodilation
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Prostacyclins Potent pulm and systemic vasodilators with antiplatelet properties Epoprostenol (IV): ↓ PVR, better CO/ex. Tolerance s/e: ↓BP, need for central line (risk of infection) Beraprost (PO): Longer duration Iloprost (nebulized)
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Endothelin receptor antagonists Endothelin-1: neurohormone that causes pulm vasoconstriction, smooth muscle proliferation, fibrosis Stimulates endothelin receptors A & B A: vasconstriction B: vasodilation Nonselective: Bosentan A selective: sitaxsentan, ambrisentan Chronic pulm htn tx given long ½ life and no IV preparation s/e: hepatic toxicity
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BOSENTAS
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DEFINITION Pulmonary hypertension is mean pulmonary artery pressure greater than 25mmHg at rest or greater than 30mmHg with exercise
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