The importance of early identification and management of the high-risk obstetric patient is emphasised in the Confidential Enquiry into Maternal and Child Health (CEMACH) report. High-risk patients who need anaesthetic input include those with airway problems, cardiorespiratory disease and rare genetic conditions, such as malignant hyperthermia and suxamethonium apnoea. Anaesthetic options for labour analgesia as well as anaesthesia for operative delivery will need to be discussed in detail with the patient if a delivery management plan is to be constructed. Input from other medical teams, such as cardiologists or haematologists, are often needed. Ultimately, these measures should reduce maternal morbidity and mortality.
The relevance of pre-assessment
Despite numerous advances in medicine, obstetrics and anaesthesia, maternal mortality rates have remained fairly constant in the United Kingdom (UK) and the United States (US) in the past few decades. One reason for this is the growing number of high-risk patients becoming pregnant, including those with advanced maternal age, obesity and significant cardiovascular, respiratory and neurological conditions. The management of high-risk pregnant patients is amongst some of the most challenging clinical fields for obstetricians and anaesthetists and needs multidisciplinary input from other specialists including cardiologists, haematologists and a variety of other medical specialists.
Careful and early identification of these high-risk patients can lead to timely investigations, referrals and medical management while anticipating and preventing worsening of the pre-existing condition and forming an appropriate delivery plan. The importance of early identification and management of the high-risk obstetric patient is emphasised in the Confidential Enquiry into Maternal and Child Health (CEMACH) report. This peer-reviewed maternal morbidity and mortality audit includes examples of maternal deaths that have resulted from poor recognition of life-threatening illness by inexperienced clinicians and lack of timely input from seniors and other specialties.
Obstetric pre-assessment clinics with joint anaesthetic input are a useful way to achieve early identification and appropriate management of the high-risk pregnant woman. Recognition and early referral for an anaesthetic opinion can save lives in a variety of medical conditions. These include the appropriate recognition of the potentially difficult airway, optimisation of treatment plan in patients with cardiorespiratory, thrombo-embolic and neurological disease, including those with prosthetic valves, cardiomyopathies, asthma, procoagulant conditions, haemophilia, human immunodeficiency virus (HIV), multiple sclerosis (MS) and epilepsy. Of particular importance is the appropriate management of the obese parturient due to the rising incidence of obesity which is coupled to an increased risk of emergency caesarean section (CS), bleeding and difficult airway problems.
Growing numbers of high-risk patients are becoming pregnant which increases the demand for early joint obstetric and anaesthetic intervention. Early identification, timely investigation, appropriate specialist referral, planned anaesthetic management and involvement of a multidisciplinary team could reduce maternal morbidity and mortality.
Assessment and recognition of the difficult airway
For over 2 decades, despite various advances in the management of the pregnant patient, the incidence of failed intubation in the obstetric population remains around 1 in 300 cases, which is approximately 10 times higher than in the general population. At the same time airway complications remain the leading cause of anaesthetic death amongst parturients. Majority of cases of failed intubation have occurred in the context of an emergency CS under general anaesthesia (GA) , which is associated with a greater risk of maternal mortality than neuraxial anaesthesia.
These trends have to be examined in the context of the increasing CS rates in the US and the UK. In the US, >30% of the deliveries are performed by a CS whereas, in the UK, the CS rate is around 24%. Because some are performed as emergencies and/or in patients with contraindications to regional techniques, the overall number of cases performed under GA is likely to increase and, as a consequence, the incidence of difficult airway amongst the obstetric population is likely to rise, especially as the incidence of obesity increases. Obesity is increasing at an alarming rate worldwide. It is estimated that >30% of parturients in the US and the UK are obese (body mass index (BMI): >30 kg/m 2 ). The potential airway problems associated with pregnancy and obesity are well known and are discussed in two reviews of maternal mortality in Michigan. From 1972 to 1984, there were 15 maternal deaths due to anaesthetic reasons; of these, 80% of the mothers were obese and 80% of the cases were CSs. From 1985 to 2003, there were eight deaths directly attributable to anaesthesia.
Clearly, the potential for morbidity and mortality due to the difficult airway is large with a spectrum of situations, most of which are variations of the same theme – difficult/failed intubation, difficult mask ventilation and lung aspiration. Therefore, the earliest possible recognition of the potentially problematic airway is of utmost importance.
Assessment and recognition of the difficult airway
For over 2 decades, despite various advances in the management of the pregnant patient, the incidence of failed intubation in the obstetric population remains around 1 in 300 cases, which is approximately 10 times higher than in the general population. At the same time airway complications remain the leading cause of anaesthetic death amongst parturients. Majority of cases of failed intubation have occurred in the context of an emergency CS under general anaesthesia (GA) , which is associated with a greater risk of maternal mortality than neuraxial anaesthesia.
These trends have to be examined in the context of the increasing CS rates in the US and the UK. In the US, >30% of the deliveries are performed by a CS whereas, in the UK, the CS rate is around 24%. Because some are performed as emergencies and/or in patients with contraindications to regional techniques, the overall number of cases performed under GA is likely to increase and, as a consequence, the incidence of difficult airway amongst the obstetric population is likely to rise, especially as the incidence of obesity increases. Obesity is increasing at an alarming rate worldwide. It is estimated that >30% of parturients in the US and the UK are obese (body mass index (BMI): >30 kg/m 2 ). The potential airway problems associated with pregnancy and obesity are well known and are discussed in two reviews of maternal mortality in Michigan. From 1972 to 1984, there were 15 maternal deaths due to anaesthetic reasons; of these, 80% of the mothers were obese and 80% of the cases were CSs. From 1985 to 2003, there were eight deaths directly attributable to anaesthesia.
Clearly, the potential for morbidity and mortality due to the difficult airway is large with a spectrum of situations, most of which are variations of the same theme – difficult/failed intubation, difficult mask ventilation and lung aspiration. Therefore, the earliest possible recognition of the potentially problematic airway is of utmost importance.
Induction of anaesthesia
A period of pre-oxygenation using a tight-fitting mask connected via hollow tubing to an anaesthesia machine is performed immediately prior to the administration of intravenous drugs to induce anaesthesia. Following this, the anaesthetist will pass an endotracheal tube (ETT; intubate) through the vocal cords with the aid of a laryngoscope blade. If the anaesthetist has difficulty in intubating the patient, the initial safest option is to maintain oxygenation using facemask ventilation. Airway deaths during anaesthesia are commonly due to a failure to oxygenate the patient, rather than failure to intubate. Persistent attempts at intubation at the expense of oxygenation are inadvisable. A difficult airway can be defined either as difficulty in placing an ETT or as difficulty in providing mask ventilation. In effect, either scenario could result in lack of oxygenation to the patient.
Airway difficulties in obstetrics may occur in up to 7.9% of parturients , which is more than 3 times the incidence in the rest of the population. Difficulties in intubation and mask ventilation can exist independently of each other. In addition, multiple attempts at intubation can lead to trauma and airway swelling and bleeding, all of which can make it difficult or impossible to mask-ventilate the patient.
Physiological and anatomical changes in pregnancy influencing airway management:
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Airway oedema – Oestrogen-mediated decreased size of laryngeal inlet requiring the use of a smaller-size ETT; also worse in pre-eclampsia, with the administration of fluids, and in the second stage of labour due to expulsive efforts.
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Respiratory changes – Increased oxygen consumption, cephalad displacement of the diaphragm by the pregnant uterus, which leads to a decreased functional residual capacity (FRC) and expiratory reserve volume (ERV). This leads to rapid desaturation during times of hypoventilation or during attempts to intubate since there is less oxygen reserve available in the lungs. This makes it mandatory to pre-oxygenate every pregnant woman for at least 3 min with 100% oxygen prior to administering a general anaesthetic as well as giving oxygen during the recovery period. The supine position and obesity further decrease FRC and speed up the process of desaturation and fatal hypoxaemia. Therefore, it is imperative to elevate the head and provide a slight left-tilt in order to displace the gravid uterus and to prevent it from splinting the diaphragm and compressing the vena cava. The desaturation that occurs during apnoea in a term-parturient in the supine or Trendelenburg position is similar to the speed of desaturation in a morbidly obese patient. Furthermore, in the paralysed patient, the time to severe hypoxia is much shorter than the half-life of suxamethonium, which is a commonly used muscle relaxant to facilitate intubation.
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Weight gain – In general, most women gain, on average, 15 kg or more in pregnancy. Weight gain may lead to difficult/impossible intubation and/or mask ventilation. Obesity leads to further decrease in FRC as well as greater metabolic demands, all of which compound the speed of desaturation during periods of apnoea/hypoventilation which, of course, makes intubation and ventilation even more challenging.
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Breast tissue enlargement – During intubation, enlarged breasts may interfere with the laryngoscopic view in the supine position by making the insertion of the blade more difficult and also restricting the degree of laryngoscope manipulation necessary to improve visualisation of the larynx.
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Gastro-oesophageal sphincter laxity – Due to the influence of progesterone, gastro-oesophageal smooth muscle relaxes, making reflux common in pregnancy. Labour and the use of opioids, including neuraxial opioids, also decrease the speed of gastric emptying making pregnant women at increased risk of regurgitation and aspiration of gastric contents.
Airway assessment
The majority (>90%) of airway disasters could potentially be predicted. This is possible by a thorough examination of patients’ airways in a non-urgent setting, such as in the preassessment clinic. By performing a few simple tests (e.g., Mallampati test, thyromental distance, atlanto-axial extension and mandibular protrusion), we can recognise the signs of a potentially problematic airway. The patient can then be referred to an anaesthetist and an appropriate early management plan created. Taking into account conditions such as obesity and pre-eclampsia would further help anticipate problems. In such cases, there is an opportunity to assess the airway and to look out for physical characteristics associated with a potentially difficult airway as well as to advise the patient with regard to the appropriateness of placement of an epidural early in order to avoid airway problems.
Commonly used tests for assessing the airway
Mallampati test ( Fig. 1 )
This test assesses the size of the tongue in relation to the oropharynx. It is performed with the patient sitting with their mouth wide open and tongue protruded without phonation. The structures visible should be recorded as follows:
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Mallampati class 1 – Uvula, tonsillar pillars, soft and hard palate all visible
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Mallampati class 2 – Soft palate, hard palate and only base of the uvula are seen
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Mallampati class 3 – Soft and hard palate are visible
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Mallampati class 4 – Hard palate is visible only
Traditionally, Mallampati classes 1 and 2 are not associated with a difficult intubation whereas 3 and 4 are associated with problems. The score seems to increase with gestational age and weight gain during pregnancy as well as in the course of a prolonged labour. The test has a low predictive value on its own and should be used in combination with other airway assessment tests in order to improve its sensitivity and specificity. In combination with ‘thyromental distance’ evaluation, the specificity is 98% and sensitivity 80%. The rationale behind measuring thyromental distance is that it gives an idea of the mandibular space depth. If the mandibular space is small then this, anatomically, could mean an obstacle to obtaining a good laryngoscopic view, making intubation more difficult.
Thyromental distance
This is easily measured by extending the patients neck and measuring the distance (in centimetres or finger breadths) between the chin and the notch of the thyroid cartilage. If it is ≥6.5 cm, intubation should not be difficult. A short thyromental distance of < 6.5 cm might be associated with a difficult intubation, especially if the Mallampati score is 3 or 4.
Atlanto-occipital joint extension
This simple test is performed by asking the patient to maximally extend her head while in the sitting position. The normal range is around 35° extension and correlates with the ability to assume the ‘sniffing the morning air’ position which is optimal for obtaining a good laryngoscopic view. A reduction in the extension range of ≥12° correlates with difficult intubation.
Mandibular protrusion test
The patients’ ability to protrude the mandible beyond the upper incisors may also be a useful tool. Normally, the patient should be able to protrude her mandible anterior to the upper incisors. This is a good predictor of an easy laryngoscopic view, in contrast to those in whom the lower incisors cannot be brought in line with the upper incisors.
Similar to the Mallampati score, none of the above-described tests have a good predictive value for difficult intubation. In combination, however, they can alert the assessor of potential airway difficulties, especially if also associated with obesity and a short neck. These tests are simple and can be performed as part of an antenatal assessment and, if in doubt, patients should be referred for an anaesthetic opinion. If a difficult intubation is anticipated, the parturient should be encouraged to have an early epidural insertion, assuming there are no contraindications.
Haematological problems in pregnancy
Thrombophilia
Pregnancy is associated with a physiological hypercoagulable state. Venous thrombo-embolism occurs in 0.1% of pregnancies but is the most common direct cause of maternal death. Untreated calf-vein thrombosis and pulmonary embolism in pregnancy is associated with 15% and 25% mortality, respectively. Some women have hereditary (e.g., activated protein C resistance, antithrombin III deficiency, protein C or protein S deficiency) or acquired thrombophilia (e.g., antiphospholipid syndrome) or a past medical history of thrombosis. In addition, some obstetricians treat women with a history of stillbirth, miscarriage and intrauterine death with prophylactic doses of antithrombotics, such as aspirin or low-molecular-weight heparin (LMWH) or both. Others require continuation of their pre-pregnancy therapeutic dose of antithrombotics for indications such as prosthetic heart valves.
A working party of the Royal College of Obstetricians and Gynaecologists (RCOG) have published guidelines for the prophylaxis of thrombo-embolism during pregnancy. The drug of choice for most prothrombotic conditions is LMWH. LMWHs are recommended because their use is associated with a lower incidence of osteoporosis and thrombocytopaenia than with unfractionated heparin (UFH), need less monitoring and may be given as a once-daily subcutaneous injection. They have a prolonged action and are only partially reversible with protamine, which implies that LMWH prophylaxis may delay administration of regional blockade. Prophylactic doses of LMWH have been associated with the formation of spinal haematoma in non-pregnant patients who have received regional analgesia and anaesthesia although many of these cases have been associated with the use of large doses in high-risk patients. The risk of developing a spinal haematoma following a prophylactic dose of LMWH in pregnancy is unknown. Most units follow the same protocols as for non-obstetric patients :
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Regional anaesthesia should be avoided for 12 h after a prophylactic dose of LMWH (6 h after a dose of UFH).
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Regional anaesthesia should be avoided for 24 h after a therapeutic (treatment) dose of LMWH.
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LMWH can be given 2 h after placement of a regional block (epidural/spinal) or removal of an epidural catheter. However, many units choose to give LMWH 6 h after surgery to reduce the potential for postoperative surgical bleeding problems.
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In any other case, the risk–benefit ratio of the patient’s condition should be examined and a joint decision with an anaesthetist, with regard to the options and timing of analgesia, should be taken. For example, in severe cardiac disease a labour epidural may represent a safer management option for delivery even though the patient may be on anticoagulants.
Thrombocytopaenia
A low platelet count may occur in pregnancy (<150 × 10 9 l −1 ) for many reasons ranging from gestational thrombocytopaenia to idiopathic thrombocytopenic purpura (ITP). The platelet count normally decreases in pregnancy, but should be investigated if the level is <115 × 10 9 . Platelet count differs from platelet function. In gestational thrombocytopaenia, the count may be low but function is normal. In ITP, the count will be low. Naturally, it is easier to measure platelet count than function. The difficulty lies with deciding when to perform a regional block with a low platelet count, since there are no fixed ‘safe limits’ for platelet count prior to inserting an epidural. However, most units would adhere to the policy of not instituting regional blockade if the count is <75 – 80 × 10 9 . In addition, trends in platelet count may be more important than absolute values. Tests of platelet function, such as those using the thromboelastography and the platelet function analyser (PFA100), are available but not routinely performed. In some conditions it is advisable to perform coagulation tests as well when the platelet count is low, for example, severe pre-eclampsia.
Von Willebrand’s disease
Von Willebrand’s disease (vWD) is a heterogeneous group of mainly autosomal dominant disorders in which there is a decreased or abnormal circulating von Willebrand factor (vWF). vWF combines with factor VIII to form a procoagulant complex, which protects factor VIII from premature destruction and also assists platelet adhesion to the exposed sub-endothelium of damaged capillaries. This leads to impairment of platelet adhesion to exposed endothelium and the whole clotting cascade. The condition varies in severity from mild disease (type 1: 80–90% of cases), which improves with pregnancy to a very severe form in which vWF is absent (type 3, autosomal recessive: <1% of cases). Desmopressin (DDAVP) may increase the concentration of vWF in certain forms of vWD.
Haemophilia
Haemophilia A and B are X-linked disorders with factor VIII and IX deficiencies, respectively. Classically, they do not affect female population; however, approximately 1 in 10 female carriers have a clinically significant clotting deficiency. A concentration of factor of 30% of normal or more is acceptable for vaginal delivery. For operative delivery, factor concentrations are brought up to normal levels.
Both haemophilia and vWD should be managed jointly with a haematologist. There should be a clear management plan, which should also include management of a secondary haemorrhage, the latter being not uncommon in either condition. An epidural is rarely contraindicated in type 1 vWD; however, haematological interpretation of factor VIII concentration is needed before deciding on a regional technique. In haemophilia, regional analgesia is usually contraindicated.
Where an epidural has been placed, removal of the catheter might be hazardous due to a precipitous fall in factor VIII concentration in the post-partum period. Therefore, it should be removed immediately after birth or only when the coagulation profile has returned to normal. In any case, the involvement of a haematologist at an early stage in all bleeding disorders cannot be overemphasised.
Cardiovascular disease in the pregnant patient
The latest CEMACH report showed that cardiac disease is the most common direct cause for maternal death and the second most common after thrombo-embolism.
The spectrum of cardiac disease amongst mothers in the UK is very wide. However, there are some general principles applicable to each heterogeneous group, many of which have been outlined in the latest CEMACH report. The summary of those findings is outlined below:
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There is a distinct need to appreciate the profound impact of physiological changes in pregnancy on pre-existing cardiac disease. Even when only mildly symptomatic, certain cardiac conditions (e.g., aortic or mitral stenosis, coarctation of aorta and many others) are associated with significant maternal and fetal risks.
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Management of pregnant women with cardiac disease should be delivered by consultant obstetricians and anaesthetists experienced in dealing with high-risk patients.
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Investigations such as chest X-rays (CXRs) are essential in certain circumstances (e.g., cardiac failure) and should not be deferred, as the fetal radiation exposure is minimal.
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It is essential to involve other specialists including an anaesthetist, cardiologist and/or a haematologist at an earliest stage and outline clear management plans for delivery.
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The severity of the maternal condition must not be underestimated and must not be attributed to the ‘normal’ symptoms of pregnancy.
The severity of cardiac disease is assessed according to the New York Heart Association (NYHA) classification of severity of symptoms:
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NYHA class 1–No limitation of physical activity and no symptoms of fatigue, palpitations, dyspnoea or angina
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NYHA class 2–Slight limitation of normal activity and symptomatic with ordinary physical activity
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NYHA class 3–Marked limitation of physical activity and symptomatic on mild exertion
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NYHA class 4–Unable to carry out any physical activity without discomfort and symptomatic at rest
Women of NYHA class 1 and 2 tolerate pregnancy well, although certain conditions (aortic and mitral stenosis, pulmonary hypertension and complex lesions) are extremely hazardous even if asymptomatic. NYHA classes 3 and 4, the presence of cyanosis, myocardial dysfunction, prior arrhythmia and prior heart failure or stroke are considered high risk for maternal cardiac events. In any case, a full history and examination should be performed at a very early stage of pregnancy (during the first trimester) and ideally the management of the woman with cardiac disease should have commenced prior to conception.
During early pregnancy the woman should be managed jointly with a cardiologist and, in some instances, a haematologist. An appropriate set of cardiac investigations should be arranged on recommendation of a cardiologist, including an echocardiogram, electrocardiogram (ECG), CXR and, in some instances, cardiac catheterisation. There needs to be a clear plan regarding the best place for antenatal management and delivery. In many instances, the woman should be referred to a regional unit with specialist cardiology or cardiac surgery facilities. The antenatal visits should be more frequent and an experienced obstetric anaesthetist should also be involved in the delivery plan. Women should have serial cardiac investigations and, in some instances, should be admitted to hospital towards the end of the third trimester for repeat investigations, monitoring of anticoagulation, oxygen therapy and developing a multidisciplinary management plan. At this stage, if not already discussed, various analgesia and anaesthesia options should be planned with the anaesthetist. In any case, irrespective of the condition, all cardiac pregnant patients require a high degree of vigilance regarding their condition, good communication amongst senior obstetricians, cardiologists and anaesthetists and appropriate facilities for antenatal and postnatal care including high dependency care and cardiac surgery facilities in some cases.
Valvular disorders
Pregnant patients may have undergone valve replacement with either a mechanical, porcine or homograft valve. Bio-prosthetic valves do not need anticoagulation but have a limited life span, whereas modern mechanical valves have an excellent haemodynamic profile and rarely need replacement, but their use still requires anticoagulation. Warfarin use is probably safe during the first 6 weeks of pregnancy, but there is a risk of embryopathy if used between 6 and 12 weeks’ gestation. For pregnant women with prosthetic heart valves, the American College of Chest Physicians (ACCP) has recommended one of the following thromboprophylactic regimens :
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Administration of adjusted-dose, twice-daily LMWH throughout pregnancy
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Adjusted-dose UFH throughout pregnancy
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Administration of either UFH or LMWH in the first trimester and then warfarin until close to delivery, when either UFH or LMWH is used. This allows for more flexibility reversing the anticoagulant effects of these drugs prior to delivery.
It is also important to note, in such patients, infective endocarditis antibiotic prophylaxis is no longer recommended for vaginal delivery or CS in the absence of infection, irrespective of the type of maternal cardiac lesion. Most patients with cardiac disease can be delivered vaginally. Pre-existing maternal cardiac disease is not an indication for an elective CS. Regional analgesia and anaesthesia is not an absolute contraindication in such patients either. Epidurals, single-shot spinals, combined spinal epidural and continuous spinal techniques can be used. However, a careful evaluation of the underlying cardiac condition and the potential effects of regional blockade is needed. For example, a single-shot spinal for an elective CS may lead to a profound fall in blood pressure secondary to vasodilation (a reduction in systemic vascular resistance). Whilst this may be tolerated in healthy pregnant patients, a mother with severe aortic stenosis with a fixed cardiac output will not. A low-dose epidural for labour analgesia using 0.1% bupivacaine and 2 μg ml −1 fentanyl is unlikely to cause significant vasodilation/falls in blood pressure and may be beneficial to mothers with cardiac problems undergoing a trial of labour. Furthermore, the timing of regional blockade may be important if the mother is on anticoagulation with LMWH. Therefore, a combined peripartum management plan from the cardiology/obstetric/anaesthesia team is essential.
A few brief notes on some cardiac lesions encountered in pregnancy are given below.
Aortic stenosis
The severity of aortic stenosis (AS) can be classified according to the average valvular area or the pressure gradient. It becomes haemodynamically significant when the valve diameter is one-third of normal. Severe AS is defined as a valve area <0.8–1 cm 2 and a peak gradient >40–50 mmHg. Asymptomatic women prior to conception tolerate pregnancy well whereas those with severe symptoms prior to conception are at risk of acute left ventricular failure (LVF) and would need valve repair prior to conception. Moderately to severely symptomatic women have a relatively fixed stroke volume and may be unable to maintain adequate coronary or cerebral perfusion, producing symptoms of dizziness and syncope. Regional blockade has been safely used in these patients with adequate haemodynamic monitoring.
Aortic regurgitation
In the absence of left ventricular dysfunction, pregnancy is tolerated well. In the event of LVF, treatment is with diuretics, digoxin and salt restriction. Angiotensin-converting enzyme (ACE) inhibitors are contraindicated in pregnancy due to their potential to cause fetal renal agenesis and can be substituted with a different vasodilator, on the advice of a cardiologist. Epidural analgesia is beneficial and the preferred method both for vaginal and caesarean deliveries.
Mitral stenosis
This is the most common valvular defect seen in pregnancy and is almost always associated with a past history of rheumatic heart disease. Clinically, symptomatic stenosis occurs when the size of the valvular orifice is ≤2 cm 2 . It can be associated with atrial fibrillation (AF) and patients are at risk of embolic episodes. It may lead to pulmonary hypertension. These patients do not tolerate pregnancy well and have a high incidence of AF, which is associated with development of systemic emboli. The incidence of complications is related to the severity of the stenosis (67% if severe, i.e., valvular area of ≤1 cm 2 ; 38% if moderate, area of 1–1.5 cm 2 and 26% for mild mitral stenosis, valvular area of >1.5 cm 2 ). In labour, mitral stenosis patients need invasive haemodynamic monitoring and adequate HDU facilities with a cardiologist on site. There is no indication for operative delivery; however, the second stage may need to be assisted by forceps or ventouse as a Valsalva manoeuvre, during the pushing stage, may result in haemodynamic problems. These patients should have adequate analgesia and an epidural is recommended.
Congenital heart disease
A large proportion (∼80%) of children born with congenital heart disease (CHD) now reach reproductive age and can present in the antenatal clinic. Pregnancy can still be associated with a high number of serious complications. There is also the issue of managing the pregnant patient with a prosthetic valve. Cyanotic heart disease is associated with higher maternal morbidity and mortality but all pregnant women with CHD should be considered high risk, especially those with pulmonary hypertension, cyanotic conditions, Marfan’s syndrome, complex surgically repaired conditions (e.g., Fontans or Mustard procedures) and metal prosthetic heart valves.
Cardiomyopathy
Hypertrophic obstructive cardiomyopathy (HOCM) is frequently inherited and presents with left ventricular flow obstruction. These women have usually been diagnosed prior to conception and should already be under the care of a cardiologist. The greater the outlet obstruction to the left ventricle, the higher is the risk of myocardial ischaemia. Frequently, these patients are on beta-blockers, which should be continued throughout pregnancy. Tachycardias, arrhythmias and factors increasing myocardial contractility (vasopressors, circulating catecholamines, beta-agonists, etc.), as well as hypovolaemia and vasodilatation, are poorly tolerated.
Dilated cardiomyopathy can present in the peripartum period. The condition is characterised by reduced myocardial contractility, a hypokinetic left ventricle and a reduced ejection fraction (<0.4). These women present with classical signs of left heart failure and are at risk of embolic events.
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