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Common Congenital Heart Lesions - page 90 / 126

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90 / 126

90 of 126

  • A.

    Diuretics:

    • Mechanism of action: reduce volume causing reduced preload. End - diastolic volume and pressure fall, preventing pulmonary congestion.

    • If patient is on the flat part of the Frank-Starling curve, then decrease in preload will not significantly reduce CO. Must monitor dosage carefully to ensure diuretic does NOT significantly CO.

    • Only used if there is evidence of pulmonary congestion (rales) or edema

    • Since patients with heart failure have reduced renal perfusion, they must be treated with LOOP diuretics (furosemide, torsemide, bumetanide), thiazide diuretics can also be used

    • Caution: overdiuresis decreases CO and causes hypokalemia and hypomagnesia, which can precipitate arrhythmias.

    • If patient has purely diastolic dysfunction, then they need high diastolic filling pressures, therefore must be careful with diuretics

  • B.

    Vasodilators:

    • Mechanism of action: counteract vasoconstriction of neurohormonal mechanisms, results in reduced volume and ventricular remodeling

    • Venous vasodilators (nitrates): decrease venous return to the heart, reducing LV diastolic filling pressure and pulmonary capillary hydrostatic pressure, results in decreased pulmonary congestion

    • Arteriolar vasodilators (hydralazine): decrease systemic vascular resistance, therefore decreases afterload and increases SV. Increased CO balances decreased TPR, causing BP to stay the same.

    • Balanced vasodilators (ACE inhibitors): affects both veins and arteries. ACE inhibitors reduce AII, which 1. reduces vasoconstriction 2. reduces aldosterone promoting sodium and water excretion and decreasing volume 3. increases bradykinin, a vasodilator

      • 4.

        limits ventricular remodeling

    • ACE inhibitors increase survival and are the standard first line therapy for patients with LV systolic dysfunction.

    • What if patient can’t tolerate ACE inhibitors? Angiotensin II receptor blockers (ARB) also block AII and do not cause cough associated with ACE Inhibitors. Can also use H-ISDN (combo of venous dilator isosorbide dinitrate and arteriolar dilator hydralazine). Third choice is Nesiritide (recombinant BNP), but administered IV and is expensive.

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