Severe cardiac disease in pregnancy, part I: hemodynamic changes and complaints during pregnancy, and general management of cardiac disease in pregnancy Walther N.K.A. van Mooka and Louis Peetersb Purpose of review Part I of this review gives an overview of the hemodynamic changes that occur in normal pregnancy, the approach to the pregnant patient with complaints during pregnancy, and the general management of cardiac disease in pregnancy. Recent findings The maternal circulatory adaptation to pregnancy consists almost entirely of adaptive changes in the maternal cardiovascular system in response to a primary systemic vasodilatation. Conversely, hemodynamic maladaptation consists of a combination of absence of these changes with signs of sympathetic dominance in the autonomic control of the cardiovascular system. Summary The hemodynamic changes of normal pregnancy per se have profound effects on preexisting cardiac function. Counseling of and care for this subset of patients are challenging for the obstetrician, cardiologist, anesthesiologist and, sometimes, the intensivist to optimize maternal and neonatal survival.
Introduction
Keywords arrhythmia, cardiac surgery during pregnancy, congenital, endocarditic prophylaxis, heart disease, ischemic, peripartum cardiomyopathy, thromboprophylaxis, valvular
Hemodynamic changes of normal pregnancy
Curr Opin Crit Care 11:430— —434. ª 2005 Lippincott Williams & Wilkins. a
Department of Intensive Care and Internal Medicine and bDepartment of Gynecology and Obstetrics, University Hospital Maastricht, Maastricht, Netherlands Correspondence to Walther N.K.A. van Mook, Department of Intensive Care and Internal Medicine, P Debeyelaan 25, 6202 AZ Maastricht, The Netherlands Tel: +31 43 3876385; fax: +31 43 3874330; e-mail:
[email protected] Current Opinion in Critical Care 2005, 11:430— —434 Abbreviations CHD HELLP
congenital heart disease hemolysis elevated liver enzymes low platelets
ª 2005 Lippincott Williams & Wilkins. 1070-5295
430
Although the incidence of cardiac disease in pregnancy remained more or less unchanged (0.1–4%) [1–4], maternal mortality has decreased from 6% in the 1930s [5•], to 0.5% to 2.7% now [1–3,6]. Pregnancy increases the maternal mortality risk in cardiac patients as compared with the general pregnant population [4], and actual risk depends on the underlying cardiac disease. With some exceptions (see Part II), maternal death during pregnancy is rare in women with heart disease [2,7–10]. Cardiac disease in pregnancy presently accounts for 15% of pregnancyrelated maternal mortality [11], and is the most common nonobstetric cause of maternal death [11–13]. Although maternal mortality is low, pregnant women with heart disease are at risk for serious morbidity such as heart failure, arrhythmias, and stroke [14,15]. The hemodynamic changes of normal pregnancy per se have profound effects on preexisting cardiac function, so counseling of and care for this subset of patients are challenging for the obstetrician, cardiologist, anesthesiologist and, sometimes, the intensivist to optimize maternal and neonatal survival [16].
In the sixth week of pregnancy, the maternal circulation becomes ‘hyperdynamic,’ indicating that cardiac output increases and systemic vascular resistance decreases without concomitant rise in metabolic rate [17,18]. The latter is not accompanied by acceleration of the mean circulation time, most likely because of the observed concomitant rise in arterial and venous compliance [19]. Meanwhile, almost all measurable circulatory changes consist of compensations for an initial fall in systemic vascular tone induced by a yet unknown pregnancy-specific factor [20]. The current concept is that this particular fall in systemic vascular tone lowers mean systemic filling pressure and with it, both cardiac preload and afterload. The decrease in cardiac preload activates the volume-retaining systems, resulting in plasma volume expansion [21]. On the other hand, the fall in cardiac afterload not only raises cardiac output by enabling a larger stroke volume to be ejected into the ascending aorta [22]. It also leads to a fall in arterial filling pressure, which triggers the nonosmotic release of vasopressin, and with it water retention and hemodilution [21]. The consequences of these changes for the cardiac output are as follows. In the first trimester the cardiac output increases by approximately 30% or ±1500 mlminÿ1 mostly due to a rise in stroke volume. The rise in cardiac output reaches a plateau of
Severe cardiac disease in pregnancy, part I van Mook and Peeters 431
approximately 40% above nonpregnant values by pregnancy weeks 24 to 28. The midpregnant rise in cardiac output mostly results from a combined rise in heart rate and stroke volume. Finally, in the third trimester the cardiac output tends to fall again by 10–20%, in conjunction with a decrease in stroke volume, which is only partly compensated for by a rise in heart rate [18,22]. Postpartum, the circulatory changes return to prepregnant values within several days [23]. Maternal posture may affect cardiac output, particularly in advanced pregnancy. In supine position, the cardiac output tends to be lower than in lateral position, probably due to pressure of the gravid uterus upon the inferior vena cava, thus impeding venous return. In a small proportion of women, the latter is accompanied by a fall in blood pressure [24]. The more or less abrupt fall in systemic vascular tone in the sixth week of pregnancy is accompanied by an approximately 10 and 5 mmHg fall in diastolic and systolic blood pressure, respectively (Fig. 1), with a pattern of change until midpregnancy mirroring that in cardiac output. After week 30 of pregnancy, blood pressure begins to rise again to reach prepregnant values by term. The larger decrease in diastolic than in systolic blood pressure complies with its probable trigger being the fall in total peripheral vascular resistance [18,20,22]. Nevertheless, the underlying mechanism of the latter is incompletely understood. It is conceivable that the baroreceptor is reset in conjunction with the higher compliance of the vascular tissue surrounding the receptor [19]. During labor, blood pressure may increase by up to 10 mmHg [22] in response to the stress of labor, which increases the sympathetic activity in the vascular bed [22]. During pregnancy, the pressure in the central veins and those in the upper extremities changes little. Pressure in the veins in the lower extremities, however, increases progressively from 10 mm H2O in pregnancy week 10, to 25 mm H2O near term [22]. Structural changes in the heart resemble those in response to endurance training. Already by the end of the first trimester, both atria and Figure 1. Pattern of change in blood pressure with advancing pregnancy
Adapted from [22].
the left ventricle have become enlarged, indicating the development of a mild cardiac hypertrophy [22,25]. It is unclear whether the latter is paralleled by a consistent change in cardiac contractility [20,25]. The increase in abdominal pressure pushes the diaphragm upwards, giving rise to a more cranial, slightly exorotated position of the heart, changes that mildly affect the electrocardiogram in pregnancy [26]. The pregnancy-dependent changes in vascular tone and compliance have no appreciable structural effects on the vasculature. The hyperdynamic circulation raises shear forces in the circulation and with it, the mechanical stress exerted upon the endothelial lining of the vascular bed. These forces stimulate the endothelial release of protective vasodilators such as nitric oxide and prostaglandin I2, thus emphasizing the hyperdynamic circulation [27]. In the first trimester, most of the rise in cardiac output is directed towards kidneys, mammary glands, and skin [22]. Meanwhile, the overall oxygen consumption does not increase appreciably [17]. The latter supports the view that most of the generated surplus in cardiac output is directed towards arteriovenous shunts, mostly those in the skin, or to the kidneys, where it causes hyperfiltration. Both effects seem to protect the microcirculation against excessive flow. After the first trimester, O2 uptake and with it, O2 extraction begins to increase gradually in concert with a progressive rise in uterine O2 consumption. These changes are consistent with a rise in uterine blood flow at the expense of shunt flow, suggesting that the gradual rise in total O2 consumption results from an increase in fetoplacental oxygen consumption [22,26]. The most important changes in hemodynamics during uneventful human pregnancy are listed in Table 1. The cardiovascular adaptation to pregnancy consists of a so-called Table 1. Changes in hemodynamics and volume homeostasis during pregnancy Parameter Cardiac output (l/min) Heart rate (beats/min) Stroke volume (ml) Systolic blood pressure (mmHg) Diastolic blood pressure (mmHg) Peripheral vascular resistance (dynecmsecÿ5) Pulmonary vascular resistance (dynecmsecÿ5) Colloid-osmotic pressure (mmHg) Active plasma renin concentration (pg/ml) a-Atrial natriuretic peptide (pmol/l) Osmolality (mOsm/l) Plasma volume (ml) Total red blood cell volume (ml)
Nonpregnant 4.5 70 65 110 80
24— —28 wk pregnant 6.0 85 72 105 70
1600
1000
119 21
78 18
16 54 287 2500 1500
41 30 272 3800 1800
All listed changes are significant except for those in a-atrial natriuretic peptide. Data are collected and deduced using the sources listed in [37].
432 Cardiovascular system
preparational phase (first half of pregnancy) and a so-called materialization phase (second half of pregnancy). In most cases, the adequacy of the preparational phase is determined by the ability of the maternal cardiovascular system to accommodate the initial pregnancy-specific systemic fall in vascular tone. In conditions of compromised cardiovascular reserves (e.g. chronic hypertension, renovascular disease, diabetes, etc.), the ability to respond properly to the latter is inadequate [28]. As a matter of fact, it is conceivable that the consequence of inadequate adaptive capacity in these women would be a fall in blood pressure in response to the pregnancy-specific stimulus. Observations in these women suggest that such a potentially life-threatening response may be overruled by some ‘rescue response,’ which consists of a rise in cardiovascular sympathetic tone [29]. Therefore, these women may be identified during the preparational phase by a combination of absent normal compensations to the primary vasodilator stimulus with presence of signs of sympathetic cardiovascular hyperactivity [30]. The absent or only small increase in metabolic demands in the preparational phase explains why maternal maladaptation to pregnancy can remain latent. With pregnancy advancing beyond 20 weeks, the impact of the rapidly rising metabolic demands of the conceptus increasingly challenge the maternal cardiovascular system and metabolism. When uteroplacental insufficiency leads to intervillous hypoxia, free oxygen radicals, and other toxic products may be spilled into the maternal bloodstream, triggering systemic endothelial dysfunction, which initiates a cascade that culminates into the clinical symptoms of hypertensive disorders of pregnancy, such as preeclampsia and the hemolysis-elevated liver enzymeslow platelets syndrome [31].
The approach to the pregnant patient with complaints It can be difficult to differentiate between patients with complaints attributable to changes of pregnancy itself, and those with complaints related to heart disease. Shortness of breath, palpitations, dizziness, edema, and limited exercise capacity are common complaints during pregnancy. Pregnancy can also induce normal variants using commonly used diagnostic tools, thereby providing an extra pitfall in the work-up of these patients [32]. The following list indicates the findings on physical examination and variants encountered using common additional investigation tools [8]. (1) Inspection (a) jugular venous distention and prominent pulsation; (b) brisk and diffuse apex pulsation; (c) right ventricular impulse. (2) Auscultation (a) mitral component S1 increased, S1 widely split; (b) pulmonary component S2 increased, S2 split;
(c) occasional S3; (d) aortic or pulmonary middiastolic flow murmurs; (e) systolic brachiocephalic trunk murmur; (f) continuous venous hum over jugulum; (g) systolic or continuous mammary souffle audible. (3) Chest radiograph (a) apparent cardiomegaly; (b) enlarged left atrium; (c) increased vascular marking; (d) straightening of left-sided heart border; (e) postpartum pleural effusion (right sided). (4) Electrocardiography (a) Rhythm, rate, and intervals (i) increased rate, sinus tachycardia; (ii) small increases of PR and QT (heart rate dependent); (iii) right bundle branch block. (b) Axis (i) 15 degrees axis rotation; (ii) deviation of electrical axis to the left. (c) De/repolarization changes (i) Q waves in III; (ii) T wave inversion in III, V2, V3. (5) Echocardiogram (a) trivial tricuspid regurgitation; (b) pulmonary regurgitation; (c) increased left atrial size (12–14%); (d) increased left ventricular end-diastolic dimensions (6–10%); (e) inconsistent increase in left ventricular thickness; (f) mitral regurgitation; (g) pericardial effusions. On the other hand, chest pain, syncope or near-syncope, paroxysmal nocturnal dyspnea, hemoptysis, and progressive edema are not normal during pregnancy and should be carefully evaluated [32]. Acute pulmonary edema in pregnancy is frequently caused by cardiac disease (25.5%) [33], and 15% to 52% of cardiac abnormalities are diagnosed during pregnancy [2,32,33]. Once a diagnosis of cardiac disease has been made, its should be followed throughout pregnancy.
Management of cardiac disease in pregnancy Of course, risk stratification and counseling is best performed before conception. Risk stratification data can be derived from cardiovascular history taking, and physical examination, 12-lead electrocardiogram, echocardiography data, and arterial oxygen saturation (when indicated). In counseling, six areas should be considered: the underlying cardiac lesion, maternal functional status, the possibility of further palliative or corrective surgery, additional associated risk factors, maternal life expectancy and ability to care for a child, and – in case of congenital heart disease (CHD) – the risk of CHD in offspring [14]. The underlying cardiac lesion is important because almost all
Severe cardiac disease in pregnancy, part I van Mook and Peeters 433
patients can be stratified into low, intermediate, and high risk groups (Table 2). Maternal functional status is an important predictor of maternal and neonatal complications [9]. Further palliative or corrective surgery should be undertaken before pregnancy if necessary and possible, and is, for example, indicated in cyanotic heart disease and/or other symptomatic patients. The additional risk factors that can complicate pregnancy include, for example, a history of arrhythmia, presence of prosthetic heart valves, and the use of (necessary) potential teratogenic medication. Maternal life expectancy and ability to care for a child are important considerations. A limited maternal physical capacity and/or a high likelihood of fetal complications may imply a potential functional inability to care for the child. Risk of recurrence of CHD in offspring in case of familial CHD is also relevant. The risk with a first-degree relative being affected increases 10-fold, and reaches an even 50% risk in autosomal dominant diseases [14]. Patients with pulmonary hypertension (systolic pulmonary artery pressure >50 mmHg) either primary or in Eisenmenger’s syndrome, dilated cardiomyopathy, Marfan syndrome with cardiovascular involvement, pulmonary arteriovenous fistulae, and any uncorrectable cardiac lesion in patients with functional class III or IV of the New York Heart Association should strongly be advised against pregnancy, and in case of pregnancy these are potential indications for pregnancy termination [32]. Some authors advise that counseling about termination of pregnancy should include the advice of a woman, preferably one who has experience of pregnancy and child care [13]. In pregnant women with uncomplicated cardiac disease, prenatal visits are scheduled at least monthly until 28–30 weeks of
gestation, then every 2 weeks until week 36, and weekly thereafter until delivery. Admission to the hospital is recommended when signs of congestive heart failure, infection, or anemia are present [32]. Women with pulmonary hypertension (in case of continuation of pregnancy) should be hospitalized around week 20, and patients in functional class IV should be hospitalized throughout pregnancy [34,35]. All other patients seem to benefit from a policy of liberal hospital admission based on maternal functional status, fetal growth and well-being, and standard prenatal care [32,36]. Further management and planning requires a multidisciplinary approach. Timing and mode of delivery, intrapartum hemodynamic monitoring, peripartum medication management including endocarditis prophylaxis, anticoagulation, and inotropic and vasopressor support should all be discussed [32]. In the sections in Part II, characteristics of specific cardiac diseases are discussed in more detail.
Conclusion The incidence of cardiac disease in pregnancy has not changed substantially over the last decades. Mortality from cardiac disease in pregnancy has decreased and is low. However, serious morbidity is still associated with cardiac disease in pregnancy. The maternal circulatory adaptation to pregnancy consists almost entirely of adaptive changes in the maternal cardiovascular system in response to a primary systemic vasodilatation. Conversely, hemodynamic maladaptation consists of a combination of absence of these changes with signs of
Table 2. Mortality risk in groups of patients with cardiac disease in pregnancy Group
Cardiac disease
I
Small left-right shunt (atrial septal defect, ventricular septal defect, patent ductus arteriosus) Mild pulmonic/tricuspid valve abnormalities Corrected tetralogy of Fallot Bioprosthetic valve Repaired lesions without residual cardiac dysfunction Isolated mitral valve prolapse without significant regurgitation Bicuspid aortic valve without stenosis Valvular regurgitation with normal ventricular systolic function Mitral stenosis Large left-to-right shunt Mechanical prosthetic heart valve Severe pulmonic stenosis Aortic stenosis Uncorrected coarctation of aorta Uncorrected tetralogy of Fallot and other unrepaired cyanotic congenital heart disease Previous myocardial infarction Moderate to severe systemic ventricular dysfunction History of peripartum cardiomyopathy without residual dysfunction Marfan syndrome with aortic or valvular involvement Severe pulmonary hypertension NYHA class III and IV symptoms Severe aortic stenosis History of peripartum cardiomyopathy with residual ventricular dysfunction
II
III
Adapted from [6,8] with permission.
Risk of cardiac complications
Mortality
Low risk
