Atrioventricular Septal Defect, Partial and Intermediate Medication

Medical treatment is indicated in patients with congestive heart failure (CHF) usually before surgical repair. However, it may also be needed in patients in whom mitral regurgitation (MR) persists postoperatively. The treatment outlined below is usually indicated for outpatient management.

Class Summary

These medications are used to decrease the afterload to the left ventricle (LV) produced by the MR. This effect is achieved by producing peripheral vasodilatation, which, in turn, reduces systemic blood pressure (ie, reduces afterload). Reduction in systemic blood pressure decreases the amount of blood pumped by the LV with each systolic contraction (ie, stroke volume) and also reduces the pressure at which the blood is ejected. This, in turn, diminishes the amount of blood regurgitated by the mitral valve from the LV into the left atrium (LA) during systole, which decreases pulmonary venous pressure and, thus, decreases pulmonary congestion. By decreasing the afterload to the LV, ACE inhibitors reduce the left-to-right shunt through the atrioventricular septal defect (AVSD) or the atrial septal defect (ASD) in the case of partial AVSD.

A recently published observational study by Cooper et al reported that babies whose mothers had taken an ACE inhibitor during the first 3 months of pregnancy had an increased risk of birth defects compared with babies whose mothers had not taken any drugs for high blood pressure.^[9] At this time, based on this one observational study, the US Food and Drug Administration (FDA) did not change the pregnancy categories for ACE inhibitors. The current pregnancy categories assigned to ACE inhibitors are C for the first trimester and D for the second and third trimesters.

Enalapril (Vasotec)

Prevents conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in increased levels of plasma renin and a reduction in aldosterone secretion.

Helps control blood pressure and proteinuria. Decreases pulmonary-to-systemic flow ratio in the catheterization laboratory and increases systemic blood flow in patients with relatively low pulmonary vascular resistance. Has favorable clinical effect when administered over a long period. Helps prevent potassium loss in distal tubules. Body conserves potassium; thus, less oral potassium supplementation needed.

Patients who develop a cough, angioedema, bronchospasm, or other hypersensitivity reactions after starting ACE inhibitors should receive an angiotensin-receptor blocker.

Captopril (Capoten)

Prevents conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in lower aldosterone secretion. Rapidly absorbed, but bioavailability is significantly reduced with food intake. It achieves a peak concentration in an hour and has a short half-life. The drug is cleared by the kidney. Impaired renal function requires reduction of dosage. Absorbed well PO. Give at least 1 h before meals. If added to water, use within 15 min. Can be started at low dose and titrated upward as needed and as patient tolerates.

Lisinopril (Prinivil, Zestril)

Prevents conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in lower aldosterone secretion.

Class Summary

These agents help decrease pulmonary congestion.

Furosemide (Lasix)

Loop diuretic that increases excretion of water by interfering with chloride-binding cotransport system, which, in turn, inhibits sodium and chloride reabsorption in ascending limb of loop of Henle and distal renal tubule. Increases renal blood flow without increasing filtration rate. Onset of action is generally within 1 h. Increases potassium, sodium, calcium, and magnesium excretion.

Dose must be individualized to patient. Depending on response, administer at increments of 20-40 mg, no sooner than 6-8 h after the previous dose, until desired diuresis occurs. When treating infants, titrate with 1 mg/kg/dose increments until a satisfactory effect is achieved.

Diuretics have major clinical uses in managing disorders involving abnormal fluid retention (edema) or in treating hypertension, in which their diuretic action causes decreased blood volume. Chronic use of furosemide can lead to hypercalcemia with renal damage and electrolyte disturbances.

Spironolactone (Aldactone)

For management of edema resulting from excessive aldosterone excretion. Competes with aldosterone for receptor sites in distal renal tubules, increasing water excretion while retaining potassium and hydrogen ions. Therefore, it is generally used when concomitant chronic use of sodium-wasting diuretics such as furosemide is noted.

Class Summary

It is used because of its direct inotropic effects in addition to indirect effects on the cardiovascular system.

Its indirect actions result in increased carotid sinus activity and enhanced sympathetic withdrawal for any given increase in mean arterial pressure. These effects help reduce the heart rate response to CHF, rendering a more effective stroke volume with each ventricular systole.

Digoxin (Lanoxin)

Enhances myocardial contractility by inhibition of Na+/K+ ATPase, a cell membrane enzyme that extrudes Na and brings K into the myocyte. Resulting increase in intracellular Na stimulates Na-Ca exchanger in the cell membrane, which extrudes Na and brings in Ca, leading to an increase in intracellular calcium in the sarcoplasmic reticulum of cardiac cells, therefore increasing contractility of myocyte (ie, positive inotropic effect). Has direct inotropic effects in addition to indirect effects on the cardiovascular system. Increases myocardial systolic contractions. It exerts vagomimetic action on sinus and AV nodes (slowing heart rate and conduction). Also, decreases degree of activation of sympathetic nervous system and renin-angiotensin system, which is referred to as the deactivating effect. May be given as a loading dose followed by a maintenance dose or simply as a maintenance regimen. Digitalis loading increases hazards of this drug. Therapeutic serum level range is 0.8-2 ng/mL.