Age: 33
Gender: Female
Occupation: Housewife
Working diagnosis: Subaortic stenosis
HISTORY
The patient had been diagnosed with mild subaortic stenosis in early childhood but did not require intervention. She had been discharged from pediatric cardiology follow-up at age 13.
She remained asymptomatic throughout her adult life and led an unrestricted lifestyle. She had no complications or events, but was not receiving regular medical care or cardiology follow-up.
The patient became pregnant at the age of 33. At 23 weeks gestation she developed fevers, sweats, headaches, and general lethargy for 3 days. Blood cultures were positive, and she was referred with a provisional diagnosis of bacterial endocarditis. Hospital admission was arranged.
Comments: Subaortic stenosis is an uncommon lesion and accounts for approximately 1% of congenital heart defects. It is usually caused by a fixed lesion in the LVOT and consists of a fibrous ridge in the LVOT proximal to the aortic valve. Less commonly the obstruction can take the form of a less discrete, tunnellike narrowing. It is often associated with other forms of congenital heart disease such as ventricular septal defect, patent ductus arteriosus, coarctation of the aorta, bicuspid aortic valve, abnormal left ventricular papillary muscle, and atrioventricular septal defect.
It is uncommon for subaortic stenosis to present with symptoms in infancy or early childhood unless there is other, concomitant congenital heart disease. It is usually diagnosed after evaluation of a childhood murmur. Symptoms are related to the degree of LVOT obstruction and may include exertional dyspnea, effort syncope, angina, congestive cardiac failure, and sudden death.
Once diagnosed, progression can be anticipated, although in childhood this is variable and many patients remain stable and asymptomatic for a long period of time. Occasionally, subaortic stenosis can be rapidly progressive. Once adulthood is reached patients may remain stable for years, though some do eventually require surgery to relieve the obstruction. Patients with subaortic stenosis are at risk of developing aortic regurgitation, usually related to the eccentric jet from the membrane striking and adversely affecting the aortic valve (which in itself is usually morphologically normal to start). The risk of bacterial endocarditis is substantial. It is more common in patients with a damaged aortic valve and can lead to significant aortic regurgitation and congestive heart failure.
CURRENT SYMPTOMS
She was well throughout pregnancy until the 23rd week, and reported fevers, sweats, headaches, and general lethargy that began 3 days prior to presentation. In particular she denied any exertional dyspnea, syncope, palpitations, or chest discomfort.
NYHA class: I
Comments: The risk to the pregnant woman with subaortic stenosis depends on the degree of LV outflow obstruction, LV function, and the presence of any associated congenital heart defects.
Ideally, patients would have been assessed prior to conception with in-depth counseling, and patients with severe obstruction and/or symptoms would have been repaired prior to pregnancy.
The hemodynamic changes during pregnancy result in a predictable increase in the gradient across the LVOT as the stroke volume rises during the second trimester and the systemic blood pressure falls.
Unfortunately, the patient was discharged from tertiary care in her early teens even though she had a commonly progressive lesion. Furthermore, and regrettably, the patient received no information on pregnancy risks to herself or her infant, or information on the risks of recurrence of congenital heart disease (estimated at up to 10% for left-sided obstructive lesions). Paradoxically, this case represents the rule rather than the exception for most of the developed world, emphasizing the need for raising awareness of pregnancy and heart disease among professionals and patients alike.
PHYSICAL EXAMINATION
BP 125/80 (right arm), HR 90 bpm, oxygen saturation 99% on room air
Height 165 cm, weight 73 kg, BSA 1.83 m 2
Surgical scars: None
Neck veins: Her JVP was not elevated.
Lungs/chest: Clear
Heart: The heart rate was regular. The cardiac impulse was slightly increased but not displaced. She had a palpable thrill with a normal first heart sound, split second, and a 3–4/6 harsh ejection systolic murmur throughout her precordium together with an early soft diastolic murmur at the left sternal edge.
Abdomen: Normal
Extremities: There was no peripheral edema and no radio-femoral delay. The patient was not clubbed and there were no splinter hemorrhages or other stigmata of infective endocarditis.
Comments: Peripheral pulses are generally of normal volume unless the LVOT obstruction is severe.
A forceful apex beat is usually present in most patients with more than mild subaortic stenosis. The presence of an increased cardiac impulse suggests significant LV hypertrophy.
The second heart sound can be narrowly split or single because of prolonged LV systole.
An ejection systolic murmur is typically heard with the length of the murmur being proportional to the degree of obstruction when LV function is preserved.
The high-pitched early diastolic murmur indicates coexisting aortic regurgitation, which may be present in 50% of patients with fixed subaortic stenosis.
LABORATORY DATA
| Hemoglobin | 10.7 g/dL (11.5–15.0) |
| Platelet count | 198 × 10 9 /L (150–400) |
| Total white cell count | 9.2 × 10 6 /L (1.0–7.6) |
| Sodium | 133 mmol/L (134–145) |
| Potassium | 4.0 mmol/L (3.5–5.2) |
| Creatinine | 0.6 mg/dL (0.6–1.2) |
| Blood urea nitrogen | 3.9 mmol/L (2.5–6.5) |
| CRP | 58 mg/dL (0.0–5.0) |
Blood cultures grew Streptococcus mitis sensitive to penicillin.
Comments: The raised white cell count, elevated C-reactive protein (CRP) concentration levels, and positive blood cultures with a typical organism strongly suggest the diagnosis of infective endocarditis. Echocardiography would be indicated to look for vegetations.
Renal function is normal, which is important as aminoglycosides, normally given in conjunction with another antibiotic for the treatment of infective endocarditis, are nephrotoxic. Furthermore, renal dysfunction can result from hemodynamic compromise secondary to acute endocarditis. The latter constitutes an indication for surgery when medical treatment is failing.
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