An Unusual Presentation of Congenital Heart Disease

Abstract

We describe an unusual presentation of congenital heart disease mimicking preeclampsia in a young, gravid girl. The diagnosis of Shone's complex was confirmed by echocardiography. This complex is manifested by multiple levels of obstruction involving the left side of the heart and the systemic circulation. It is extremely rare, especially in pregnant adolescents. We briefly describe the patient's clinical history, physical examination, and treatment, as well as our clinical decisions regarding her case. The discussion focuses on the spectrum of findings in Shone's complex and the physiologic impact of therapy on this patient. (Tex Heart Inst J 2003;30:214–7)

During pregnancy, a series of cardiovascular adaptations increase cardiac output to support the developing fetus. Both heart rate and stroke volume are increased. Echocardiographic studies show that these changes begin very early in pregnancy, reaching nearly maximal values by 16 weeks, with a rapid return to normal after delivery. ¹ In the presence of congenital or acquired heart disease, physiologic reserves are used to maintain adequate cardiac output and low filling pressures at rest. During the stress of pregnancy, however, symptoms often develop. Similarly, under markedly abnormal loading conditions, such as those that occur in preeclampsia, afterload mismatch may occur, with signs and symptoms of heart failure despite a structurally normal heart. Therefore, heart failure symptoms during pregnancy require careful evaluation of both structural and functional capacity.

We present the case of a young pregnant woman who presented with elevated blood pressure and signs and symptoms of congestive heart failure.

Case Report

The patient was a 15 year-old girl, pregnant for the first time, who presented in November 2000 at 25 weeks' gestation. She was seen by a physician in an outlying community for shortness of breath, dyspnea on exertion, and a flu-like syndrome. She was found to be hypertensive, with a blood pressure of 152/98 mmHg, and her chest radiograph showed pulmonary edema. A presumptive diagnosis of preeclampsia was made, and her physician arranged an immediate referral to our institution for further management.

The patient reported a history of dyspnea on exertion since the age of 9 years; she did not participate in school physical education because she could not “keep up.” Her symptoms had increased when she became pregnant, and a few days before her hospital admission, she had experienced 3-pillow orthopnea and paroxysmal nocturnal dyspnea. The flu-like symptoms had been present for 1 week. She had no history of rheumatic fever, cyanosis, chest pain, hemoptysis, palpitations, syncope, headache, facial swelling, lower extremity edema, claudication, or surgical procedures.

Physical examination showed an afebrile, 63″, 119-lb girl in mild respiratory distress with no cyanosis. Her blood pressure was 150/98 mmHg, the pulse was regular at a rate of 102 beats/min, and the respiratory rate was 22/min. Her carotid upstrokes were normal with no delay, and the jugular venous pressure was 10 cm. On palpation, she had a hyperdynamic apical impulse that was normal in size. Prominent parasternal and subxiphoid lifts were present. The S₁ was soft, and the P₂ was prominent. An opening snap was present, and a soft 2/6 diastolic rumble was heard at the apex. There was also a grade 3/6 systolic ejection murmur. Bilateral basilar rales were noted. The abdomen was gravid. The extremities showed no cyanosis, clubbing, or signs of peripheral emboli. She had bilateral 1+ pitting pretibial edema, and no pulses were palpable in the feet.

The hemoglobin level was 10.9 g/dL, and the hematocrit was 0.30. Laboratory results of clinical blood and urine chemistries were normal, and there was no proteinuria. The chest radiograph (Fig. 1) showed pulmonary edema with peribronchial cuffing and prominent pulmonary arteries. The cardiac silhouette showed left atrial enlargement with normal heart size overall. Although prominent rib notching was noted, the aortic contour appeared normal with no dilatation. Electrocardiography (Fig. 2) showed sinus tachycardia with biatrial enlargement and right ventricular hypertrophy.

Fig. 1 A) Chest radiograph shows mild pulmonary edema with a normal-sized cardiac silhouette. B) Enlargement of rib notching (arrows) is a result of collateral flow bypassing the coarctation of the aorta.

Fig. 2 An electrocardiogram reveals sinus tachycardia with biatrial enlargement and right ventricular hypertrophy.

The initial diagnosis was mild preeclampsia. A cardiologist was consulted and a transthoracic echocardiogram (TTE) was performed. The TTE showed severe stenosis at the level of the mitral valve (MV), with a supravalvular MV ring and a mean gradient of 22 mmHg. No fusion of the leaflet tips was seen. Two distinct papillary muscles were identified, and there was no parachute deformity. The pulmonary systolic pressure was estimated at 72 mmHg. Coarctation of the aorta with a gradient of 70 mmHg was shown, and a diagnosis of Shone's complex was made.

The patient was treated with furosemide, β-blockers, and 2 units of packed red blood cells; her symptoms resolved. A transesophageal echocardiogram confirmed the findings of the TTE, and also revealed a bicuspid aortic valve (Fig. 3).

Fig. 3 A transesophageal echocardiogram at the mid-esophageal level shows a supravalvular mitral valve ring (arrow).

The patient was kept on bed rest with a strategy to delay delivery until 30 weeks' gestation. Fetal growth was confirmed to be normal by periodic ultrasonography. A TTE, performed while the patient was on medical therapy, showed a decrease in pulmonary systolic pressure to 50 mmHg and a decrease in the mean mitral valve gradient to 14 mmHg. Labor was induced at 37 weeks with a radial arterial line as the only invasive monitoring. The patient was hemodynamically stable throughout labor, and delivery was uncomplicated. The baby boy had normal Apgar scores. The estimated maternal blood loss was 350 cc. The patient was given prophylactic antibiotics against possible endocarditis. She remained clinically stable during the postpartum period. A repeat TTE, performed 2 days after delivery, revealed a mean mitral gradient of only 8 mmHg. She was discharged 4 days after the delivery with outpatient follow-up by a cardiologist.

Discussion

On initial presentation, this patient had elevated blood pressure and pulmonary congestion, prompting the diagnosis of preeclampsia. On the basis of auscultatory findings, we obtained a transthoracic echocardiogram, which led to the diagnosis of Shone's complex. This anatomic complex was first reported in 1963 ² and comprises 4 obstructive lesions on the left side of the heart and circulation: a parachute deformity of the mitral valve, a supravalvular mitral ring, subaortic stenosis, and aortic coarctation. Shone described 8 patients in whom a supravalvular ring and some degree of subaortic stenosis was present. Of those patients, the parachute mitral valve and coarctation was present in 4. The associated condition of bicuspid aortic valve was also present in 4 patients. Thus, there is a complete form of Shone's complex wherein all 4 lesions are present and incomplete forms with only 2 or 3 of the lesions. ²

Our patient had an incomplete form of Shone's complex, and her symptoms at the time of presentation were caused by hypertension resulting from aortic coarctation and pulmonary congestion due to supravalvular mitral stenosis, with the latter being more serious. The fact that she had substantial pulmonary congestion despite only moderate increases in blood pressure was a clue that this might not be a typical case of preeclampsia. As is true in rheumatic mitral stenosis, the atrioventricular gradient in Shone's complex is strongly affected by heart rate and cardiac output, both of which were elevated in our patient at the time of presentation. By administering packed red blood cells and diuretics, we were able to improve the oxygen-carrying capacity and reduce the blood volume. Through the use of β-blockers, we were able to slow the heart rate. With this treatment, the patient quickly became asymptomatic, and repeat echocardiographic studies showed substantial decreases in the valve gradient and pulmonary pressure.

It is not coincidental that the patient presented at 25 weeks' gestation, since this is the time in pregnancy when cardiac output is maximal. A number of physiologic changes accompany normal pregnancy, and these can exacerbate symptoms when mitral flow is impeded. Blood volume is elevated early in gestation and is increased by about 33% between 21 and 24 weeks; ³ the volume continues to rise until around 30 weeks' gestation. The heart rate increases during the course of pregnancy and is about 10 to 20 beats/min faster at the time of delivery. ⁴ In our patient, the hemodynamic changes of pregnancy were sufficient to cause decompensation, with severe pulmonary congestion.

Of note, this patient became asymptomatic with treatment, and her induced vaginal delivery was uncomplicated. Labor and delivery cause major hemodynamic stresses, including an increase in cardiac output that is associated with uterine contraction, and with tachycardia due to pain and anxiety. ⁵ Moreover, during the immediate postpartum period, cardiac output is further elevated. ⁶ Despite this, our patient had no further pulmonary congestion—due, in part, to the continued use of β-blockade, which limited the adverse effects of tachycardia on transmitral flow.

Our patient responded to aggressive medical therapy, which spared us from considering more invasive intervention. Although percutaneous balloon mitral valvuloplasty has been used successfully during pregnancy, this technique applies only to valve leaflets that are pliable. Congenital supravalvular mitral rings typically are not compliant and are difficult to dilate; therefore, anecdotal results with percutaneous balloon mitral valvuloplasty in such situations have been disappointing.^* In their series of 72 children with congenital mitral stenosis (35% of whom had Shone's syndrome), Serraf and colleagues ⁷ avoided the use of balloon dilation. Generally, a surgical strategy, with careful consideration of valve repair, is the definitive therapy for this anatomic abnormality. However, surgery for this condition during pregnancy would most likely result in a high fetal mortality rate; therefore, the ideal situation would be to perform elective surgical correction after delivery. As part of the surgical repair, supravalvular ring resection is recommended, because valve replacement is associated with higher mortality rates and is often unnecessary.