Echocardiography is central to the management of the pregnant woman with heart disease. It is readily avail- able, can be performed safely throughout gestation, and allows a more precise defi nition of the presence and severity of cardiac lesions and serial assessment of ventricular function compared with clinical assess- ment alone. A detailed description of physiological changes and cardiac remodeling related to pregnancy
Section 2: Antenatal Care: General Considerations
is given in Chapter 3 . Understanding these changes is crucial to anticipating and recognizing the eff ects of these changes on various cardiac lesions. Th e added hemodynamic burden of pregnancy may unmask a previously well-compensated or undiagnosed lesion.
Th e frequency of echocardiography surveillance required is related to the cardiac condition and the clinical assessment. In our practice, echocardiography is usually performed at the initial assessment during pregnancy and then repeated (in all except the low-risk patients) toward the end of the second trimester when the hemodynamic changes have almost reached a maximum. In high-risk conditions, for example car- diomyopathy, PH, or aortopathy, more frequent echo- cardiographic studies are recommended. [ 1 , 2 ]
Congenital and structural heart disease encompasses a broad spectrum of lesions and each patient is poten- tially unique. Th erefore, an exhaustive approach to their echocardiographic assessment is outside the scope of this chapter. However, for all heart disease and pregnancy the essential information provided should include:
1. Ventricular size and function 2. Valvar abnormality and function
3. Estimation of cardiac pressures, in particular pulmonary artery pressure
4. Aortic dimensions .
Ventricular size and function
Measurement of systolic ventricular function has been shown to enable a degree of prediction of future cardiac events. A systemic ventricular ejection fraction <40% is particularly likely to be associated with adverse events ( Table 6.1 ).[ 4 ] It is therefore crucial that an accurate estimation of ventricular function is made precon- ception and that women with impaired function are monitored closely with serial echocardiography in pregnancy. Measures of ventricular function have to be interpreted in the context of previous measurements and the underlying cardiac lesions. Th e frequency of scans needs to be based on clinical assessment and the stability of function during pregnancy . It is important not to overlook specifi c assessment of diastolic func- tion because women with restrictive fi lling (for exam- ple, those with left ventricular hypertrophy secondary to hypertrophic cardiomyopathy or hypertensive heart disease [ Figure 6.1 ]) may poorly tolerate the increased blood volume associated with pregnancy.
Pregnancy can cause cardiomyopathy (peripartum cardiomyopathy) but it may also unmask pre-existing intrinsic cardiomyopathy. Peripartum cardiomyopa- thy is therefore a diagnosis of exclusion (discussed in detail in Chapter 16 ) and is diagnosed in the last tri- mester or the fi rst 6 months following delivery. Left
Figure 6.1 Left, apical four-chamber view in a patient showing increased wall thickness of left ventricular lateral wall and mid to distal septum (arrows). The restrictive physiology was unmasked during pregnancy by increased circulatory volume and patient developed pulmonary edema during delivery. The four pictures to the right show speckle tracking of the left ventricle of the same patient showing decreased left ventricular global strain suggesting myocardial disease. For the color version, please refer to the plate section. In some formats this fi gure will only appear in black and white.
ventricular dysfunction (ejection fraction <45%) is essential for the diagnosis; women presenting with pulmonary edema and with left ventricular dilatation but normal systolic function should not be labeled as having peripartum cardiomyopathy but need further echocardiography follow-up .
Right ventricle assessment is potentially more chal- lenging. Quantitative parameters of right ventricular function should be used to allow objective serial com- parison. Women with systemic right ventricles need close surveillance in pregnancy and the postpartum period because in some women pregnancy may be associated with deterioration in systemic ventricu- lar function despite previously good function.[ 15 , 16 ] Subpulmonary right ventricular function may also deteriorate during pregnancy in women with right ventricular volume and/or pressure overload as seen, for example, in repaired tetralogy of Fallot with severe pulmonary regurgitation.[ 5 , 13 , 17 ]
A potential role for exercise or dobutamine stress echocardiography in the preconception assessment of pregnancy risks merits investigation but data are lack- ing and this is not currently routine practice .
Valvar abnormalities and function
Careful monitoring of valvar lesions is needed during pregnancy because the normal changes expected may cause stable compensated patients to become unstable because of ventricular dilatation.
Left ventricular outfl ow tract obstruction has been identifi ed as a predictor of pregnancy outcomes in both
right- and left -sided obstructive lesions ( Table 6.1 ).
One anticipates that with the increased stroke volume of pregnancy there will be an increase in the mean and peak gradient. In aortic valve stenosis, direct planim- etry and the dimensionless index (ratio of velocity time integral in the left ventricular outfl ow tract and veloc- ity time integral above the aortic valve) may be bet- ter markers of severity compared with peak gradients alone. A fall in the gradient should raise concerns that ventricular function has deteriorated. Similarly, during pregnancy the mitral valve area may be underestimated by traditional echocardiographic parameters because the gradient across the valve increases by the square of the proportionate increase in cardiac output. Th at is, if the resting mitral valve gradient is 4 mmHg with a cardiac output of 6 l/m, an increase of cardiac output to 12 l/m will increase the gradient to 16 mmHg, mean- ing that a doubling of cardiac output will lead to quad- rupling of the gradient. Furthermore, mitral pressure half-time may be an inaccurate assessment of mitral area during pregnancy.[ 18 ] Th erefore, mitral valve area should be estimated by independent echocardi- ography measurements and calculation ( Figure 6.2 ) . Th e continuity equation (mitral valve area = stroke volume / transmitral velocity time integral) yields com- parable values during pregnancy and postpartum. It is also important in these patients to monitor pulmonary pressures closely as pregnancy progresses.
Aortic and mitral regurgitation tend to be bet- ter tolerated than obstructive lesions. In moderate to severe mitral regurgitation it remains important to monitor pulmonary pressures because left atrial
Figure 6.2 A 32-year-old patient in her fi rst pregnancy with rheumatic mitral stenosis became increasingly symptomatic with pregnancy, requiring diuretics in the third trimester. Left, transmitral Doppler in the fi rst trimester with mean diastolic gradient of 7 mmHg. Right, the gradient had increased to 15 mmHg in the third trimester. The mitral valve area was 0.71 cm 2 by the continuity equation method. For the color version, please refer to the plate section. In some formats this fi gure will only appear in black and white.
Section 2: Antenatal Care: General Considerations
pressures may be signifi cantly elevated as pregnancy progresses. Similarly, in signifi cant aortic regurgita- tion, left ventricular dimensions and function should be monitored .
Although isolated valvar regurgitation tends to be well tolerated, new-onset or signifi cant valvar regurgi- tation in the setting of complex congenital defects is oft en a prelude to hemodynamic deterioration, such as in Fontan patients. Patients with mechanical or bio- prosthetic valves should be closely assessed for valve dysfunction during pregnancy. Sudden increases in transvalvular fl ow velocity and limited leafl et open- ing are signs of valve thrombosis. If valve thrombosis is suspected, then transesophageal echocardiography should be used to confi rm or refute the diagnosis.
Right ventricular outfl ow obstruction tends to be better tolerated than left , although signifi cant pulmon- ary stenosis may result in right ventricular dysfunction and right heart failure, and pressures should therefore be monitored. We expect to see the gradients through the valve increase as pregnancy progresses. In patients with signifi cant pulmonary regurgitation, assessment of right ventricle size and function should be the focus of the assessment .
With all valve lesions, the development of arrhyth- mia may lead to decompensation in clinical status and, in many cases, further ventricular dysfunction.
Restoration of normal rhythm and close echocar- diography surveillance in these cases is therefore imperative .
Estimation of cardiac pressures; in particular, pulmonary pressure
PH carries a substantial mortality risk in pregnancy ( Chapter 15 ). Th e increased blood volume is poorly tolerated by the remodeled pulmonary vascular bed and women with this condition are at risk of right heart failure. In pregnant women with PH, regular echocar- diography is essential to assess not only pulmonary pressures (which are derived from the velocity of tri- cuspid regurgitation or pulmonary regurgitant jets) but also the right ventricular response to pregnancy.
Deterioration in right ventricular function can be an indication for early delivery. Postdelivery, regular echocardiography and clinical follow-up is crucial because most women who have died from this condi- tion have done so in the puerperium .
Patients with CHD defects may have a degree of adverse pulmonary vascular remodeling despite
good or even timely surgical repair, and this may be unmasked for the fi rst time in pregnancy .
Pulmonary pressures may also be used as an indi- cator of left atrial pressure in women with left heart disease. In women with shunt lesions, the pressure gra- dient across the ventricular septal defect may be used to estimate right ventricular pressure .
Aortic dimensions
Acute aortic dissection is a rare complication of pregnancy that occurs with increased frequency in certain congenital and genetic conditions such as bicuspid aortic valve, Marfan syndrome, Loeys-Dietz syndrome, and Turner syndrome. Th e risk of dis- section is linked to the initial degree of aortic dila- tation and the extent of progression of dilatation during pregnancy. However, there is a risk of aortic dissection even when aortic dimensions are in the normal range. Accurate assessment of the aortic root is crucial for preconception counseling because women may require root replacement prior to preg- nancy ( Chapter 12 ). Ideally, patients with a dilated aorta should be treated prior to pregnancy based on contemporary guideline cutoff s and clinical experi- ence at the time of counseling.[ 19 ] In women with conditions associated with aortopathy, echocardio- graphic aortic root surveillance should be performed 4–12 weekly depending on aortic root dimensions and the underlying pathology .