Introduction

Current echocardiographic imaging demonstrates aneurysmal dilation of the ductus arteriosus in more than 8% of full-term newborns.^1,2 An aneurysm of the ductus arteriosus (ADA) manifests as a saccular dilation originating from the ductus arteriosus’s descending aortic origin. An ADA may occur from an in utero process, result from a postnatal complication after a surgical or transcatheter closure of a patent ductus arteriosus, or occur secondarily from ductal endarteritis.^3,4 Proposed in utero mechanisms for an ADA include narrowing or tortuosity of the fetal ductus arteriosus with poststenotic dilatation,⁵ increased fetal ductal flow, or abnormal intimal cushion formation secondary to abnormal elastin expression.⁶

Echocardiography

Either a prenatal or postnatal echocardiogram can demonstrate an ADA. In our experience, a prenatal echocardiogram more often proves a fetal ADA in the mid to late 3rd trimester rather than earlier in gestation. A fetal ADA is usually associated with increased ductal tortuosity, ductal narrowing (Figure 14-1), a variable degree of ventricular asymmetry with right ventricular dominance, and an increased ductal flow velocity. In most cases, the neonatal ADA is an incidental finding noted during an echocardiogram performed for unrelated reasons. In some cases, a neonatal ADA is suspected because a chest radiograph demonstrates a left upper mediastinal mass. On rare occasion an ADA is discovered during evaluations for perinatal distress, pulmonary hypertension, dyspnea, stridor, hoarseness, severe perinatal hypoxia, or neonatal thromboembolic events.

In the neonate, the high-parasternal short-axis echocardiographic view visualizes the ADA just to the left of the main and left pulmonary arteries (Figure and Video 14-2). The ADA may be patent in the early neonatal evaluations with a narrowed pulmonary artery end and a wide-open aortic end. If the ductus is patent, color Doppler usually demonstrates a characteristic horizontal jet, as opposed to the almost vertical jet in the usual patent ductus arteriosus (Figure and Video 14-2). The horizontal ductal jet prevents accurate flow velocity measurement that is needed for estimating the pressure gradient between the aorta and the pulmonary artery.⁵ With color Doppler, a low Nyquist frequency allows visualization of the low blood-flow velocities inside the ADA. Echocardiographic imaging may demonstrate thrombus formation inside the ADA (Figure and Video 14-3). Echocardiography can also rule out potential thrombus migration that can propagate into the descending aorta or the pulmonary arteries.

Follow-up

Most neonatal ADAs resolve spontaneously within the first 2 months of age.^1,2 In a work by Jan and colleagues, the ADA resolved as the ductus constricted in 70% of the cases; nevertheless, the echocardiogram showed thrombus formation inside the ADA in 30 percent of cases that ADA eventually resolved.¹ The natural history of an uncomplicated ADA persisting beyond 2 months of age is unknown. A few case reports in newborns, children, and adults have emphasized the rare, yet serious, complications associated with an ADA. Reported complications include spontaneous rupture, thromboembolism, erosion into airways or esophagus, and infection. Complications may arise at any age; a recent report accounts a case of fetal demise from thrombosis of an ADA.⁷ Many of the reported complications occurred in previously undiagnosed patients. Some ADAs are diagnosed only at autopsy, following death from unrelated reasons.

All neonatal ADAs require serial echocardiograms. Surgical repair is recommended for ADAs persisting beyond the neonatal period. Surgical repair is also recommended in cases where a large ADA does not appear to be involuting, when there is migration of thrombus into pulmonary arteries or descending aorta, when there is evidence of thromboembolism, and where ADAs are compromising adjacent structures, and in patients with Marfan syndrome or other connective tissue disorders. Most authors recommend cardiopulmonary bypass for surgical resection. In those with a history of an ADA surgically repaired, follow-up is needed, as such patients may develop other cardiac lesions associated with connective tissue disorders.⁶

Introduction

Cardiomyopathies, or diseases of the myocardium, often cause both systolic and diastolic ventricular dysfunction. Most cardiomyopathies result in generalized myocardial disease and include dilated, hypertrophic, and restrictive forms.⁸ Occasionally, myocardial abnormalities are localized, rather than diffuse, such as in arrhythmogenic right ventricular cardiomyopathy (ARVC) and noncompaction cardiomyopathy. Noncompaction cardiomyopathy detection has increased via echocardiography and magnetic resonance imaging (MRI); nonetheless, the World Health Organization does not include noncompaction cardiomyopathy in its classification schema.⁹ The Pediatric Cardiomyopathy Registry estimates the annual pediatric incidence of all forms of cardiomyopathy at 1.13 per 100,000. Dilated cardiomyopathy is the most frequent at 0.54 per 100,000, followed by hypertrophic cardiomyopathy at 0.47 per 100,000. The overall incidence is significantly higher in infants <1 year of age at 8.34 per 100,000 than in older pediatric patients.¹⁰

Although “dilated cardiomyopathy” and “hypertrophic cardiomyopathy” imply primary myocardial disease, clinicians often use the terms to describe ventricular hypertrophy or dilatation of unclear etiology. We prefer using specific terminology such hypertrophic cardiomyopathy of the infant of diabetic mother or the left ventricular dysfunction and dilatation from perinatal asphyxia.

Dilated Cardiomyopathy

Dilated cardiomyopathy usually implies global systolic dysfunction and dilation of the left ventricle; however, the condition may also involve the right ventricle. Patients may present with symptoms and signs of congestive heart failure, arrhythmias, and thromboembolic events, especially from left ventricular mural thrombi. Occasionally, a prenatal echocardiogram detects fetal-cardiac systolic dysfunction, accompanied by a spectrum of fetal heart failure and hydrops.

Echocardiographic findings include increased left ventricular end-systolic and end-diastolic diameters, resulting in a reduced shortening fraction. The normally bullet-shaped left ventricle acquires a globular-spherical shape (Figures 14-4 and 14-5). The atria may also dilate, especially with atrioventricular valve regurgitation. Mitral valve annulus dilates with progressive left ventricular enlargement, leading to mitral valve regurgitation from poor leaflet coaptation (Figure and Video 14-6). Flow stasis may encourage intracardiac thrombus formation (Figure and Video 14-7).

Acute pharmacological support may require diuretics, dobutamine, dopamine, epinephrine, milrinone, and anticoagulants. Patients in significant distress will require assisted ventilation. Patients not responding to supportive therapy may need cardiac transplant. Mechanical assist devices such as extracorporeal membrane oxygenation can serve as a bridge to transplant. Chronic therapy usually includes diuretics, digoxin, ACE inhibitors, and beta-blockers. Measuring B-type natriuretic peptide, which the ventricles secrete under stress, helps guide therapy.

Familial dilated cardiomyopathy occurs in about 20 to 50% of cases. All 1st-degree relatives require regular echocardiographic screening.

Dilated Cardiomyopathy in Specific Diseases

Perinatal Asphyxia

Severe perinatal asphyxia may cause ventricular dysfunction and dilatation, likely from myocardial ischemia. Echocardiographic findings may include decreased fractional shortening, dilated ventricles, and mitral and tricuspid valve regurgitation. Tricuspid valve regurgitation may result from ischemia or necrosis of the papillary muscles and may be accentuated by coexistent pulmonary hypertension. Other than those with severe myocardial damage, most patients stabilize and improve their ventricular function after several days of supportive care.

Systemic Hypertension

Severe systemic hypertension may cause neonatal myocardial dysfunction with echocardiographic features similar to those in dilated cardiomyopathy. Echocardiography must include evaluation of the aortic arch for ruling out coarctation of the aorta, and evaluation of the abdominal descending aorta to rule out thrombi, especially in neonates with a history of having had an umbilical artery catheter. Frequently, myocardial dysfunction improves following hypertension treatment.

Structural Cardiovascular Disease

The left ventricular outflow, the descending aorta, the aortic arch, and the origin of the coronary arteries need careful assessment during echocardiographic evaluation of the infant with dilated cardiomyopathy. Aortic valve stenosis and coarctation of the aorta are frequent causes of left ventricular dysfunction and dilatation in the newborn. Anomalous origin of the left coronary artery is a rare congenital condition, which usually manifests later in infancy after the pulmonary vascular resistance decreases. With decreasing pulmonary vascular resistance, the left coronary artery blood flows retrograde into the pulmonary artery, leading to myocardial ischemia.

Myocarditis

Many viruses can cause myocarditis, including enterovirus, adenovirus, cytomegalovirus, echovirus, respiratory syncytial virus, influenza, mumps, and rubella. Viral transmission can occur transplacentally or postnatally. The echocardiogram usually reveals left-ventricular dilatation and systolic dysfunction. Nonetheless, in fulminant myocarditis, the ventricular function is often decreased without chamber dilatation. Pericardial effusion is common.

Treatment includes similar pharmacological supportive care that we noted above with dilated cardiomyopathy. Intravenous immunoglobulin may be of benefit, although validation studies are lacking.^11–13 Anecdotal evidence largely accounts for the use of steroids. Fortunately, most pediatric patients improve; however, a substantial number die or develop persistent dilated cardiomyopathy, which can lead to heart transplantation.¹⁴

Sepsis

The cause of the sepsis related myocardial dysfunction is unclear. Possibly, dysfunction occurs from circulating myocardial depressants such as endotoxins, tumor necrosis factor, and interleukin. The echocardiographic findings may be indistinguishable from dilated cardiomyopathy. The echocardiogram should rule out intra-cardiac vegetations or masses. The presentation, clinical, and laboratory findings can assist in making a diagnosis.

Hypertrophic Cardiomyopathy

Myocardial hypertrophy in hypertrophic cardiomyopathy is not from outflow obstruction or systemic diseases. Studies have revealed several causative autosomal-dominant gene mutations. Symptoms and signs relate to decreased cardiac output and occasionally complicating arrhythmias. Ventricular hypertrophy may affect the normal hemodynamics via two principle mechanisms.

1. 
   

   Outflow obstruction that limits cardiac output by blocking the exit of blood from the ventricle.

   
   
2. 
   

   Abnormal diastolic function that limits cardiac output by impeding inflow to the ventricular cavity.

Asymmetric septal hypertrophy (ASH) is the most common phenotype. Septal hypertrophy is more severe than that of the free walls (Figure and Video 14-8). ASH frequently causes left ventricular outflow obstruction, systolic anterior motion (SAM) of the mitral valve, and mitral valve regurgitation. When the hypertrophied septum bulges in systole, the left ventricular outflow narrows, producing obstruction to the flow. The Venturi effect from the outflow jet sucks the mitral valve leaflets (systolic anterior motion), further obstructing the outflow and causing mitral valve regurgitation (Figure and Video 14-9 and Figure 14-10).

The two-dimensional (2D) echocardiogram demonstrates the ventricular hypertrophy and can also evaluate the mitral valve for SAM. M-mode is useful for measuring wall thickness and documenting SAM (Figure 14-11). The systolic function is often normal to hyperdynamic. Color Doppler helps evaluate outflow obstruction and valve regurgitation. Spectral Doppler aids in quantifying the degree of stenosis and evaluating diastolic function. In hypertrophic cardiomyopathy, abnormal relaxation is responsible for diastolic abnormalities. Mitral valve-inflow Doppler can detect impaired myocardial relaxation by recording a reduced early rapid filling (E) and an increased flow velocity during atrial contraction (A) (Figure 14-12). We suggest more extensive references for a discussion of using tissue Doppler and speckle tracking for assessing diastolic dysfunction.