Anomalous Left Coronary Artery From the Pulmonary Artery: Treatment & Medication

Treatment

Medical Care

• Initial management of anomalous left coronary artery from the pulmonary artery (ALCAPA) is both supportive and temporary. Treatment of congestive heart failure (CHF) includes carefully using diuretics, afterload reduction medications, and inotropic drugs.
• Although systemic oxygen transport may be reduced in the presence of low systemic blood flow, using 100% oxygen may be deleterious. Oxygen may further reduce pulmonary vascular resistance and magnify coronary steal from the right coronary artery into the pulmonary arteries.
• A similar phenomenon occurs with aggressive afterload reduction, during which right coronary artery perfusion may be reduced, leading to decreased left coronary blood flow.
• Inotropic support, on the other hand, may significantly increase myocardial oxygen consumption, which, in the presence of reduced myocardial blood flow, may result in worsening ischemia.
• Increasing reports of catheter intervention for this lesion are emerging. The results in these instances remain conflicting. Surgical intervention remains the procedure of choice.

Surgical Care

• Spontaneous resolution of CHF symptoms is rare. Surgical revascularization of the left coronary artery system is usually necessary.
• Once the patient is stabilized, perform surgical revascularization to create a 2 coronary artery system. Over the years, the following techniques have been advocated:
  
  
  • Ligation of the left coronary artery at its origin from the main pulmonary artery is an original technique, performed without the use of cardiopulmonary bypass. The long-term results were not optimal since myocardial perfusion remained solely dependent on extensive collateralization from the right coronary artery, and the patient remained at risk for ischemic episodes and sudden death.
  • Current surgical procedures are directed at establishing revascularization by creating a 2 coronary artery system via either (1) a left subclavian artery-coronary artery anastomosis, (2) a saphenous vein bypass graft, (3) Takeuchi procedure (creation of an aortopulmonary window and an intrapulmonary tunnel extending from the anomalous ostium to the window), or (4) direct reimplantation. By establishing a patent 2 coronary artery system, most patients experience normalization of left ventricular systolic function, thereby improving long-term survival.
  • The need for simultaneous mitral valve reconstruction, in the presence of severe insufficiency, is controversial because spontaneous improvement of mitral valve function often occurs following surgical revascularization.
  • Once revascularization to a 2 coronary artery system is accomplished, most patients demonstrate improved left ventricular systolic function, decreased mitral valve insufficiency, and resolution of CHF symptoms. In many cases, the classic infarct pattern on electrocardiography eventually disappears following normalization of left coronary blood flow (see Media file 2). Occasionally, persistent refractory mitral regurgitation will necessitate delayed mitral valve repair or replacement.
• Postoperative care, precautions, and complications
  
  
  • Diuretics, and afterload reduction may be necessary until there is significant improvement in left ventricular systolic and diastolic function with resolution of mitral valve insufficiency. These medications improve cardiac output and eliminate the preoperative symptoms of congestive heart failure.
  • Although unusual, there remains a risk of cardiac dysrhythmia secondary to preoperative myocardial ischemia or infarction. Monitor continuously in the immediate postoperative period.^3,6,7,8

Consultations

Pediatric cardiologist; Pediatric cardiothoracic surgeon

Diet

No specific postoperative restrictions are usually necessary.

Activity

• Restrictions are directly related to the severity of left ventricular dysfunction and postoperative mitral valve insufficiency.
• No specific recommendations are necessary since the majority of patients are infants. For patients who are able to participate in exercise or competitive sports or those with residual postoperative hemodynamic problems, consider recommending avoidance of significant isometric activities.

Medication

Medications used at the time of presentation in patients with anomalous left coronary artery from the pulmonary artery (ALCAPA), including the judicious use of diuretics, focus on afterload reduction and inotropic support for the treatment of congestive heart failure (CHF) symptoms. Except for diuretics, medications may have immediate deleterious effects that could lead to worsening myocardial ischemia, further reductions in cardiac output, and the potential for ventricular arrhythmias. Following surgical revascularization, these same medications may be used more aggressively for the continued treatment of CHF, left ventricular dysfunction, and mitral valve insufficiency.

Diuretics

These agents promote excretion of water and electrolytes by the kidneys. They are used to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention has resulted in edema or ascites. These medications ease the work of breathing by decreasing the degree of pulmonary venous congestion (pulmonary edema) secondary to mitral valve insufficiency or elevated left atrial pressures resulting from diminished left ventricular compliance. Diuretics also may decrease systemic venous congestion (preload reduction) if right heart failure also has occurred.

Furosemide (Lasix)

Increases excretion of water by interfering with chloride-binding cotransport system, which, in turn, inhibits sodium and chloride reabsorption in ascending loop of Henle and distal renal tubule. Diuretic effect occurs within 10-20 min following an IV dose and peaks 1-1.5 hours later.

• Dosing
• Interactions
• Contraindications
• Precautions

Adult

1-2 mg/kg/dose PO/IV; may be repeated q6-8h prn

Pediatric

Administer as in adults

Afterload-reducing agents

These agents improve preoperative or postoperative cardiac output by reducing systemic vascular resistance and increasing systemic blood flow resulting from myocardial dysfunction and/or significant mitral valve insufficiency. Nitrates are peripheral and coronary vasodilators used in the management of angina pectoris, heart failure, and myocardial infarction. ACE inhibitors are beneficial in all stages of chronic heart failure. Pharmacologic effects result in a decrease in systemic vascular resistance, reducing blood pressure, preload, and afterload. Dyspnea and exercise tolerance are improved.

Nitroprusside (Nitropress)

Vasodilator of choice for severe, low-output, left-sided heart failure, providing that the arterial pressure is reasonably maintained. Rapidly acts and has a balanced effect, dilating both arterioles and veins. Because of an increase in stroke volume, considerable hemodynamic improvement without much hypotension may occur. In general, some decrease in blood pressure occurs, which may limit therapeutic effect. No PO equivalent is available.

• Dosing
• Interactions
• Contraindications
• Precautions

Adult

0.3-0.5 mcg/kg/min IV initially; titrate to effect in increments of 0.5 mcg/kg/min; average dose is 1-6 mcg/kg/min
Infusion rates >10 mcg/kg/min may lead to cyanide toxicity

Pediatric

Administer as in adults

Captopril (Capoten)

Angiotensin converting enzyme (ACE) inhibitors have a major role as a peripheral vasodilator in hypertension and CHF. They act on angiotensin-renin-aldosterone system by inhibition of ACE. Prevents conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in increased levels of plasma renin and a reduction in aldosterone secretion. This is most beneficial when CHF is accompanied by high plasma renin activity that leads to increased sympathetic activity, aldosterone release, and peripheral vasoconstriction. Use of ACE inhibitors usually is reserved for long-term postoperative management, at which point, the severity of myocardial dysfunction and mitral valve insufficiency has improved significantly to allow the use of PO medications.

• Dosing
• Interactions
• Contraindications
• Precautions

Adult

6.25-12.5 mg PO tid; not to exceed 150 mg tid

Pediatric

0.5-2 mg/kg/d PO divided tid
Test dose to evaluate the patient's blood pressure response may be necessary before institution of the normal daily dose

Phosphodiesterase Enzyme Inhibitor

Milrinone

Bi-pyridine positive inotrope and vasodilator with little chronotropic activity. Different in mode of action from both digitalis glycosides and catecholamines. Selectively inhibits phosphodiesterase type III (PDE III) in cardiac and smooth vascular muscle, resulting in reduced afterload, reduced preload, and increased inotropy.

• Dosing
• Interactions
• Contraindications
• Precautions

Adult

50 mcg/kg IV loading dose over 10 min followed by continuous infusion at 0.375-0.75 mcg/kg/min

Pediatric

Administer as in adults; although used as DOC in many pediatric intensive care units, safety and efficacy not well established. Typical dosing is 0.25-0.50 mcg/kg/min. There is some evidence, in adults, that doses about 0.4 mcg/kg/min increase myocardial oxygen supply-demand mismatch, which could be deleterious in ALCAPA. The use of a loading dose at initiation of therapy is controversial.