Implications for anesthetic care in antenatal and postpartum care for pregnant women with cardiovascular conditions

Pregnancy heart team: A lesion-specific approach

Editor, Heart disease is a leading cause of maternal death. Management of pregnant women with preexisting cardiac problems should be undertaken by multidisciplinary teams in tertiary centres [1]. Single ventricle anomalies occur in only 1.5% of patients with congenital heart disease [2]. The primary anaesthetic goal is to avoid any haemodynamic change that might increase the right to left shunt and, thereby, increase hypoxaemia [3]. With this in mind, many practitioners have avoided regional anaesthetic techniques in favour of general anaesthesia. We report a case of a pregnant woman with a functionally univentricular heart and double outlet right ventricle who underwent caesarean section using an epidural technique. Case report A 32-year-old woman was referred at 30 weeks gestation to our antenatal anaesthetic clinic. Her past medical history included cyanotic congenital heart disease. At the age of 2, she was diagnosed as having congenital heart disease, the exact nature of which was not known. She had a right thoracotomy and a R. Blalock shunt. Her obstetric history included a caesarean section for partial placental abruption 8 years previously, which had been performed under general anaesthesia without complications. On admission, the patient was 165 cm, 75 kg and she was New York Heart Association (NYHA) class IIA. Her physical examination showed moderate central cyanosis, marked digital clubbing, a grade 3/6 systolic ejection murmur heard maximally at the upper left sternal border radiating over the entire precordium into her neck. On room air, arterial blood gas analysis revealed a PaO2 of 68 mmHg. Oxygen saturation by pulse oximetry (SpO2) was 89%. Haematocrit was 50%. Echo revealed mitral atresia, double outlet right ventricle, pulmonary valve stenosis and severe hypoplastic left ventricle (Fig. 1). The ECG showed normal sinus rhythm with right ventricular hypertrophy.Fig. 1Because of increasing fetal hypoxia (as shown by fetal bradycardia, pathological blood flow in ductus venous and umbilical vein on Doppler) a caesarean section was electively performed at the 34th week of gestation. The patient was given ranitidine and metoclopramide intravenously (i.v.) 1 h before the operation. The heart rate and ECG were monitored continuously using a three-lead system, the arterial pressure was monitored directly through left radial artery cannulation and a central line was inserted into the right jugular vein. Endocarditis prophylaxis was given. Pulmonary artery catheterization was considered. However, it was felt that, because of the anatomy, interpretation of values would be extremely difficult. With the patient in the sitting position, a lumbar epidural catheter was inserted through a standard 18-gauge Tuohy needle at the L3/L4 intervertebral space. Preservative free normal saline was used to test for the loss of resistance. Following a test dose of 3 ml lidocaine 2%, the patient was placed in the supine position with a left lateral tilt. Throughout the procedure, her central venous pressure (CVP) was maintained between 6 and 10 mmHg with i.v. Ringer lactate. Epidural boluses of 5 ml of ropivacaine 0.75% were given 5, 15 and 30 min after the test dose (with the addition of fentanyl 50 μg to the first two boluses). The choice of ropivacaine was made because of its safer haemodynamic profile [4]. Sensory blockade to touch and cold was achieved at the 6th and 4th thoracic dermatomes, respectively. Cardiovascular parameters remained stable during the development of the block. Blood pressure (BP) ranged from 110/65 mmHg to 125/75 mmHg. Just after delivery, 5 mg of furosemide was given to the patient and an oxytocin infusion was commenced. Following a fall in BP to 80/40 mmHg, she became nauseous. Treatment consisted of 50 μg increments of phenylephrine to a total dose of 100 μg and another litre of Ringer's solution was infused. Thereafter, BP was kept stable using 5 mg increments of ephedrine to a total of 20 mg. After the operation, the patient was transferred to the ICU and a continuous infusion of ropivacaine 4 mg h-1 and morphine was commenced. She remained in the ICU for 24 h and in the coronary care unit for another 5 days. Her postoperative course was complicated by deep vein thrombosis (DVT) in the left leg, even though low molecular weight heparin had been given. The patient was treated conservatively and she was discharged from the hospital 2 weeks later. Discussion Congenital heart disease in pregnancy is increasingly common because of the advances in surgery and medical therapy which have taken place over the last 30 years, which means that more affected women are surviving to reproductive age [5]. Single ventricle anomalies are rarely seen in parturients [6]. The management of anaesthesia in these patients should be aimed at providing anaesthesia while maintaining a favourable balance between systemic and pulmonary vascular resistance. This would ensure that there would be minimal change in the amount of right to left shunt [7]. Traditionally in Greece, general anaesthesia has been recommended for these patients because the relative sympathectomy that occurs with regional anaesthesia would tend to decrease systemic vascular resistance (SVR) and, therefore, promote increased right to left shunting. General anaesthesia, however, carries some risks. These include the potential for tachycardia and increasing BP in response to catecholamine release after laryngoscopy, during anaesthesia and in recovery given the relatively poor pain control achievable with systemic opioids. Intermittent positive ventilation increases intrathoracic pressure, reduces venous return and increases pulmonary arterial pressure. In addition, general anaesthesia can be associated with difficult or failed intubation and aspiration of gastric contents. The use of regional anaesthetic techniques in high-risk cardiorespiratory patients undergoing elective caesarean section is a new trend, as an increasing number of case reports demonstrate satisfactory cardiovascular stability. Epidural anaesthesia because of its slow onset has a reduced chance of precipitating haemodynamic deterioration and has been used successfully in similar cases [8]. Although epidural anaesthesia can result in patchy or incomplete block, which in turn may lead to undesirable sympathetic stimulation, it was adequate for this patient. The patient received an oxytocin infusion. Oxytocin can cause direct vasodilatation and reduction of the SVR with a compensatory increase in heart rate and cardiac output. These effects can be decreased by a slow i.v. infusion. The importance of maintaining SVR has already been emphasized. The prophylactic and therapeutic use of vasoconstrictor drugs, therefore, seems logical and attractive. We initially used phenylephrine because the patient was tachycardic. But later, when the heart rate was within normal values, we chose ephedrine, as it is the most commonly used vasoconstrictor in obstetric practice [9]. Patients with cyanotic congenital heart disease are at increased risk of developing air embolism and thromboembolism. Therefore, the i.v. lines should be carefully checked; the patient should also receive heparin [10]. Although epidural anaesthesia decreases the likelihood of postoperative DVT formation, the patient developed a DVT postoperatively in her left leg despite being on low molecular weight heparin. Invasive monitoring has been used, except for a pulmonary artery catheter. It has been suggested that the use of pulmonary artery catheters has not reduced the peripartum mortality; also insertion can be difficult owing to low cardiac output and anatomy. Echocardiography represents another possibility for monitoring these patients and could be used. The risk of congenital heart disease in the fetus is increased from twice to 20-fold, depending on the nature of the mother's lesion [11]. As haemodynamics do not return to normal for several days, continued close monitoring in a high-dependency unit is necessary for a minimum of 72 h. Women with complex congenital heart disease rarely achieve successful pregnancy. For optimum outcome these patients should be managed by multidisciplinary teams. The clinical team should include obstetricians, cardiologists, anaesthetists and midwives with experience in such cases. This case adds to the total experience of a subject where, due to considerable individual variations, every such case tends to be unique.

The aim of this study was to determine differences in the acute and chronic impact of adaptive servo-ventilation (ASV) on left chamber geometry and function in patients with chronic heart failure (CHF). An acute ASV study was performed to measure echocardiographic parameters before and 30 min after the initiation of ASV therapy in 30 CHF patients (mean age: 69 years, 23 male). The chronic effects of ASV therapy were also evaluated in 26 of these 30 patients over a mean follow-up period of 24 weeks. Patients were divided into two groups according to the status of ASV therapy [ASV group (n= 15) and withdrawal group (n= 11)]. In the acute study, heart rate and blood pressure were significantly decreased 30 min after the ASV therapy compared with baseline. Stroke volume and cardiac output were significantly increased in conjunction with a reduction in systemic vascular resistance. Multivariate regression analysis revealed baseline E/e' to be an independent predictor for absolute increase in cardiac output. In the chronic study, a significant reduction of left ventricular (LV)/left atrial (LA) volumes and the severity of mitral regurgitation (MR), and improved LV diastolic function parameters were noted in the ASV group. These beneficial effects were not observed in the withdrawal group. The acute beneficial impact of ASV is mainly associated with the reduction of afterload resulting in an increase in stroke volume and cardiac output. In contrast, chronic ASV therapy produces LV and LA reverse remodelling resulting in an improvement in LV function and the severity of MR in patients with CHF.

Hemodynamic trial of sequential treatment with diuretic, vasodilator, and positive inotropic drugs in left ventricular failure following acute myocardial infarction

Background:Liver donors are subjected to specific postresection hemodynamic changes. The aim was to monitor these changes and to evaluate the effect of magnesium sulfate infusion (MgSO4) on these changes together with total anesthetic agents consumption.Patients and Methods:A total of 50 donors scheduled for right hepatotomy were divided into two equal groups. Controls (C) received saline and magnesium group (Mg) received MgSO4 10% (30 mg/kg over 20 min) administered immediately after induction of anesthesia, followed by infusion (10 mg/kg/h) till the end of surgery. Hemodynamics, transesophageal Doppler (TED) data and anesthetic depth guided by Entropy were recorded.Results:Postresection both groups demonstrated an increase in heart rate (HR) and cardiac output (COP) in association with lowering of systemic vascular resistance (SVR). The increase in HR with Mg was lower when compared with C, P = 0.00. Increase in COP was lower with Mg compared to (C) (6.1 ± 1.3 vs. 7.5 ± 1.6 L/min, P = 0.00) and with less reduction in SVR compared to C (1145 ± 251 vs. 849.2 ± 215 dynes.s/cm5, P < 0.01), respectively. Sevoflurane consumption was lower with Mg compared to C (157.1 ± 35.1 vs. 187.6 ± 25.6 ml, respectively, P = 0.001). Reduced fentanyl and rocuronium consumption in Mg group are compared to C (P = 0.00). Extubation time, postoperative patient-controlled fentanyl were lower in Mg than C (P = 0.001).Conclusion:TED was able to detect significant hemodynamic changes associated with major hepatotomy. Prophylactic magnesium helped to reduce these changes with lower anesthetic and analgesics consumption and an improvement in postoperative pain relief.

The hemodynamic actions of the new dihydropyridine calcium-channel blocker amlodipine were assessed and compared with those of nitrendipine using anesthetised dogs and were also investigated in conscious dogs with and without beta-adrenergic blockade. After bolus intravenous administration, amlodipine (25 to 1600 micrograms/kg) or nitrendipine (1 to 128 micrograms/kg) was administered to anesthetised dogs at 30-minute intervals, caused dose-related reductions in systemic and coronary vascular resistances with corresponding increases in cardiac output and coronary flow. Nitrendipine, unlike amlodipine, caused marked acute hypotension. The onset of action of amlodipine was markedly slower than that of nitrendipine, and effects were maintained for 30 minutes--recovery from nitrendipine was largely complete at 30 minutes. In conscious dogs, amlodipine (250, 500, 1000 micrograms/kg IV) caused dose-related reductions in systemic vascular resistance that approached maximum within 5 minutes and persisted for over 4 hours. Reflex increases in heart rate, cardiac output, and cardiac contractility were attenuated by prior treatment with propranolol, resulting in earlier and greater falls in blood pressure, but no marked adverse effects on cardiac contraction or conduction. In the absence of propranolol, maximum falls in blood pressure occurred 3 to 4 hours after the dose, possibly as a result of the changed baroceptor sensitivity induced by amlodipine. These results show amlodipine to have the basic hemodynamic profile of other dihydropyridine calcium-channel blockers, but in addition it demonstrates a slower onset and longer duration of action; the reasons behind these pharmacodynamic properties are discussed.

Gerard W. Ostheimer “What’s New in Obstetric Anesthesia” Lecture

The hemodynamic pattern in hypertension varies according to the age of the subject and the stage of the hypertensive disorder. In the early stage, both cardiac output and systemic vascular resistance tend to be elevated. Already at that stage, mild degrees of left ventricular function disturbance can be detected. Advanced stages are characterized by a hypokinetic type of circulation with subnormal cardiac output and considerably increased systemic vascular resistance. Both cardioselective and nonselective beta-receptor antagonists lower cardiac output and tend to raise systemic vascular resistance. Even left ventricular filling pressures tend to be higher. While these effects are most distinct in the acute experiment, cardiac output remains always depressed and systemic vascular resistance stabilizes often at a higher level, compared with pretreatment values, even during long-term therapy. The antihypertensive action of beta-receptor blockers appears to be mainly due to the reduction of cardiac output. Combined alpha--beta-adrenergic blockade lowers blood pressure predominantly by alpha-adrenoceptor-mediated reduction of systemic vascular resistance both when induced acutely and during long-term administration. Owing to its beta-adrenoceptor blocking component, the increase of cardiac output is abolished: cardiac output is maintained at pretreatment levels, as is left ventricular filling pressure. Since a well-balanced blockade of both alpha- and beta-adrenergic receptors counteracts the hemodynamic changes occurring in the course of hypertension and tends to restore cardiovascular dynamics towards normal, combined alpha--beta-adrenoceptor blockade appears to be one of the most logical and rational therapeutical approaches to hypertension.

Clinical Update on Vasopressors and Titration Strategies.

After completing this article, readers should be able to: Pregnancy causes considerable physiologic change in women, particularly in their cardiovascular systems. Circulating blood volume increases dramatically, and cardiac output increases up to 50% by the end of pregnancy. Pregnant women who have cardiac disease must be able to accommodate these normal changes to have a successful pregnancy. Inability to do so can result in increased morbidity and mortality.Cardiac disease is an important cause of nonobstetric mortality during pregnancy and can result in significant morbidity. (1)(2) Approximately 10% of all maternal deaths in the United States can be attributed to cardiac disease, a number that has remained consistent for the last half century. (1) In one study of 1,000 pregnant women who had various types of cardiac disease and were followed by the same health-care team over a 10-year period, more than 75% of the women had no complications during pregnancy. (2) Among the remaining 25%, the following complications were seen most often: The overall maternal mortality rate in this group was 2.7%, and the stillbirth and spontaneous abortion rate was 7.7%.Cardiac disease covers a wide range of conditions, including congenital heart disease, acquired disease such as rheumatic valvular disease, and coronary disease. It is estimated that 1% to 3% of women either have cardiac disease entering pregnancy or are diagnosed with cardiac disease while they are pregnant. (1)(3) The frequency of specific types of cardiac disease seen in an individual medical center depends on the patient population and local conditions. Advances in the diagnosis and treatment of congenital heart disease have increased the survival rate of children affected with these disorders. As this population enters childbearing age, pregnancy counseling and management need to be addressed. Pregnant women who have congenital heart disease represent the largest number of patients seen at some referral centers, comprising as many as 70% to 80% of all the cardiac patients evaluated. (1)(4)(5) It is estimated that 1 in 10,000 pregnancies is associated with coronary heart disease, notably myocardial infarction. (6)The purpose of this article is to review the physiologic changes of pregnancy that affect cardiac disease, preconception counseling, general management throughout pregnancy, and neonatal implications.The cardiovascular changes that occur during pregnancy result in a high-flow, low-resistance state. Changes begin as early as 7 weeks’ gestation and persist until approximately 2 weeks postpartum. (7) Some of these alterations may be problematic for the woman who has cardiac disease.Blood volume increases approximately 1,600 mL in the singleton pregnancy and 2,000 mL in the twin pregnancy. Blood volume begins to increase as early as 7 weeks’ gestation and peaks at approximately 32 weeks’ gestation. In addition, by term, approximately 500 to 900 mEq of sodium and 6 to 8 L of total body water are accumulated. The composition of whole blood changes, with red blood cells increasing 20% and plasma volume increasing 45% to 50%. (7) The increase in plasma volume is responsible for the physiologic anemia of pregnancy, although the ability to carry oxygen actually increases (approximately 1,400 mL/min by term). (1) Blood flow to the uterus at the end of pregnancy increases greater than 50-fold when compared with the nonpregnant state. Uterine flow rates can be as high as 750 mL/min, consuming 10% to 15% of maternal cardiac output. (8) Cardiac output is a function of heart rate times stroke volume. During pregnancy, the maternal heart rate increases slightly, which, in addition to the markedly increased blood volume, results in an increase in cardiac output of up to 50% by term. (7)Extra blood volume can be problematic for women who have stenotic valves, dysfunction of the myocardial muscle, or ischemic heart disease. In these cases, the inability of the heart to accommodate the excess volume may lead to congestion in the heart and lungs or acceleration of ischemia. Areas of vascular weakness or defect, as seen with Marfan syndrome and aneurysms, respectively, may rupture or be weakened further under the pressure of extra blood flow. (9)(10)(11)(12)The previously noted changes account for the high-flow state of pregnancy. The low-resistance state results from a 25% decrease in SVR. Blood pressure drops in response to the decline in SVR, with the nadir occurring at 20 weeks’ gestation. As blood volume increases, blood pressure returns to early prenatal values during the third trimester. (7) Women who have left-to-right shunts are susceptible to shunt reversal if pulmonary hypertension is present or if SVR drops too low and particularly if these events occur simultaneously. Clinical signs of shunt reversal are hypoxemia and maternal and fetal decompensation. (9)(10)Labor marks a period of fluctuations in cardiac output. Uterine contraction can cause as much as 300 mL of blood to re-enter the central circulation, thereby increasing cardiac output. With the increase in cardiac output, blood volume to the placenta increases to approximately 750 mL/min. Because oxygen consumption can increase 300% during labor, the increased blood flow satisfies the demand for oxygen in the patient who has adequate blood volume, appropriate hemoglobin levels, and a healthy cardiovascular system. On delivery of the fetus and placenta, it is estimated that 1,000 mL of blood can be displaced from the uterus and lower extremities back into the maternal circulation. (7)(8)(13) Pulmonary hypertension and certain valvular lesions require a consistent amount of volume or preload to maintain cardiac output. Fluctuations in volume delivered to the right side of the heart during labor and at the time of delivery can result in a decline in cardiac output. (9)(10)Pregnancy is a hypercoagulable state. An increase in certain clotting factors in conjunction with depression of the fibrinolytic system places the pregnant woman at increased risk for thrombus formation. This is particularly problematic with certain types of atrial fibrillation and mechanical heart valves. The need for anticoagulation to prevent thrombus formation can place the patient at risk for postpartum hemorrhage. (9)Many of the normal symptoms of pregnancy, such as fatigue, dyspnea, orthopnea, and palpitations, can mimic symptoms of cardiac disease. (14)(15) Careful examination for abnormal cardiovascular signs and symptoms is an important part of prenatal care because cardiac disease may be unmasked by physiologic changes of pregnancy (Table 1).It is mandatory that women who have chronic cardiac disease undergo a complete evaluation before attempting pregnancy. The basic evaluation should include: complete cardiovascular history and physical examination, 12-lead electrocardiography, transthoracic echocardiography, and possibly pulse oximetry or arterial blood gas determination. (4) Transthoracic echocardiography confirms the lesion and determines severity. An ejection fraction of less than 55% is associated with an increased risk of heart failure during pregnancy. (16)(17) An exercise stress test mimics changes seen during pregnancy, such as elevation in heart rate, and can assist the clinician in estimating cardiac response. (14) Doppler flow studies are useful in measuring the size of the affected valve(s), which then helps to determine the risk of complications during pregnancy. (16)Determining the woman’s ability to function within the constraints of her cardiac disease is an important baseline and ongoing assessment. The New York Heart Association (NYHA) Functional Classification is used to determine the woman’s baseline functional status and to monitor how functional status changes in response to the changes of pregnancy (Table 2). (1)In general, if the patient has a symptomatic lesion that can be corrected, this should be undertaken before pregnancy. (4)(14) In two studies comparing women who had cyanotic lesions that were corrected prior to pregnancy with women who did not have corrective surgery, the women who had the corrective surgery had fewer early pregnancy losses and small-for-gestational age infants. (14)(18)(19) Women who have stenotic valves that are classified as severe also should be considered for palliative treatment before pregnancy. (17)Different types of cardiac disease have been grouped into risk categories to estimate maternal risk. The risk assigned to each group is based on treatment given by a multidisciplinary health-care team experienced in caring for pregnant women who have cardiac disease (Table 3).Although useful, assigning of risk categories should be accompanied by a thorough review of the literature for the woman’s specific lesion that takes into consideration outcomes associated with new treatments and therapies. (9) Because pregnancy is a dynamic state, the woman’s functional classification may change during the course of the pregnancy. A woman who has mitral stenosis functional class I may be NYHA functional class III or IV at the time of delivery. (20)Anticoagulation therapy is required for some cardiac disease, most notably valvular lesions complicated by atrial fibrillation and mechanical valves. Controversy exists as to the best medication and regimen to achieve adequate anticoagulation. When used for anticoagulation for mechanical valves, warfarin is believed to provide better protection against thrombus formation than heparin. Because warfarin may be teratogenic during organogenesis, its use during early pregnancy is not recommended. Fetal/neonatal complications reported when warfarin was administered during organogenesis include nasal hypoplasia, optic atrophy, abnormalities of the digits, changes in the epithelium, mental impairment, and chondroplasia punctata. (17) In addition, because warfarin crosses the placental barrier, it must be discontinued late in the pregnancy to reduce the risk of intracranial hemorrhage in the fetus during the delivery process. (1)(4)(17)(21)To achieve therapeutic heparin levels to prevent thrombus formation, the partial thromboplastin time must be approximately twice that of normal. However, it can be difficult to achieve a consistent level of therapeutic anticoagulation with unfractionated subcutaneous heparin. (1) The ability of low-molecular weight heparin to provide adequate anticoagulation with mechanical valves remains uncertain. (22) The optimal choice for anticoagulation (warfarin, heparin, or a combination of both) in pregnancy in the setting of a mechanical heart valve is controversial, and close collaboration between specialists in obstetrics, cardiology, and anesthesia is critical. (4)(17)(21)Of all cardiac diseases, the types associated with the highest risk for maternal mortality are Marfan syndrome with valve involvement, dilated cardiomyopathy, uncorrectable NYHA class III or IV lesion resistant to medical treatment, and pulmonary hypertension with either systolic pulmonary pressure greater than 50 mm Hg or with Eisenmenger syndrome. In these cases, a thorough discussion with the woman regarding pregnancy termination is mandatory. (1)(23)Preconception counseling should include a review of the patient’s disease and current functional status as well as a discussion of the anticipated risks to her of pregnancy. The possibility of preconception corrective surgery or therapy should be addressed. Management during pregnancy, the effect pregnancy might have on maternal life expectancy, and the ability of the patient to care for her child all are important issues to address during counseling. Patients should be made aware of any risks of fetal damage as a result of treatment during pregnancy as well as the increased risk of cardiac disease in the fetus/neonate. (4)(24)If the woman who has cardiac disease did not have the benefit of preconception counseling before pregnancy, testing and counseling as described previously should be undertaken as soon as possible. Women who have symptomatic valvular disease may be candidates for valve replacement or palliative therapy during pregnancy. The optimal time for the procedure may be during the second trimester to avoid organogenesis in the first trimester as well as the increased risk of preterm labor or decreased placental perfusion in the third trimester. (4)(16)(17)A multidisciplinary team should be assembled early in the pregnancy that includes obstetrics, cardiology, anesthesia, neonatology, and nursing. The purpose of the team is to review specific information about the woman’s cardiac disease, anticipate potential system problems or problems the woman may encounter during pregnancy, and develop a written plan of care that is available to all departments. (4)(24) The plan should include optimal gestational age for delivery, best location for labor and delivery, and specific plans for delivery, such as the need for invasive monitoring or subacute bacterial endocarditis prophylaxis. (4)At each prenatal visit, the functional status of the woman should be reassessed. Evaluation for abnormal cardiovascular signs and symptoms listed in Table 1 may warn of complications. Complications specific to pregnancy, such as preeclampsia, anemia, infection, and hyperthyroidism, are treated aggressively if found. (4)In a review of 276 pregnancies in 221 women who had cardiac disease, predictors of cardiac complications during pregnancy included history of a prior cardiac event or arrhythmia, NYHA functional class III or IV on entry to prenatal care, left heart obstruction (presence of a mitral valve or aortic valve lesion or both), and myocardial dysfunction. (25) Prior cardiac events were defined as heart failure, stroke, and transient ischemic attack. Arrhythmias were either bradyarrhythmias or tachyarrhythmias that were symptomatic or required treatment. A complication was reported in 18% of the 276 pregnancies. Among those who experienced a complication, 89% of the complications occurred in the antepartum period and were due to either heart failure or arrhythmia. (25)As stated earlier, labor and delivery involves substantial hemodynamic fluctuations. Uterine contractions during labor result in a rise in blood pressure, heart rate, cardiac output, and oxygen consumption. Relief of the discomfort of contractions can lessen the rise in blood pressure and heart rate, but it has less effect on cardiac output. (17) During the late second stage of labor, cardiac output can increase as much as 45%, and each contraction can increase the value an additional 15%. (13)(17)The timing, management, and route of delivery in a woman who has cardiac disease are dependent on her functional status late in pregnancy and her particular cardiac disease. Timing of delivery is based on functional status in response to the cardiovascular changes in late pregnancy, trends in functional status, the status of the fetus based on antenatal testing and growth measurements, and the possibility of further treatments that could relieve signs of decompensation to allow the pregnancy to continue. (1)For women who have cardiac disease, delivery is planned best at a time when all team members are available. This is especially true for women who have NYHA functional class III or IV disease and a risk classification of intermediate/moderate or high/major. (1) The optimal mode of delivery must be individualized. Vaginal delivery is reasonable for most women and is associated with less risk of hemorrhage, infection, and pulmonary edema as well as an easier postpartum recovery compared with cesarean delivery. Women who have suspected aortic dissection, a dilated aortic root, or severe valvular disease requiring urgent repair probably are delivered best via cesarean section. (1)(4)(14)The level of monitoring during labor is dependent on functional status and risk classification. Functional classification should be reassessed regularly during labor and delivery and specifically for a persistent heart rate greater than 100 beats/min at rest. If allowed to persist, such a heart rate can result in decompensation with some forms of cardiac disease. Pulse oximetry (with the use of oxygen to maintain saturation at pre-established baseline levels), auscultation of the lungs, strict intake and output, and continuous fetal heart rate monitoring are basic monitoring components. (1)(9) The lateral recumbent position most often is the position of choice during labor because it maintains adequate venous return. (4)(14)(17)(26)Invasive hemodynamic monitoring should be considered for women who have NYHA functional class III or IV disease, pulmonary hypertension, impaired left ventricular function, severe aortic stenosis, or recent myocardial infarction. (1)(4)(14) Invasive hemodynamic monitoring may be contraindicated if the woman has had corrective heart surgery that involved placement of shunts or other devices. (1)Pain control is a key part of the labor and delivery management plan. Epidural anesthesia is the preferred method of pain control because it can decrease workload on the heart, provide consistent pain relief, and minimize the release of catecholamines in response to pain and stress. Early consultation with anesthesia ensures that the anesthesiologist has adequate time and information to determine the best method of maintaining adequate preload with epidural administration or, if epidural administration is contraindicated, the best method of managing the woman’s pain control needs. (1)(4)(6) Shortening the end of the second stage of labor with low outlet forceps or vacuum, thereby avoiding the Valsalva maneuver, prevents further hemodynamic changes that may affect cardiac function. (4)(14)During delivery, patients may be exposed to a period of bacteremia. The exact incidence is not known, and the duration of exposure is believed to be brief, but in certain women who have cardiac disease, the duration may be sufficient to result in the development of endocarditis. According to the American College of Obstetricians and Gynecologists, the American Heart Association, and the American College of Cardiology, women who have cardiac disease can be placed into three categories for risk of development of bacterial endocarditis during labor and delivery: negligible risk, moderate risk, and high risk (Table 4).(27)(28)(29)Antibiotic prophylaxis is initiated approximately 30 minutes before delivery and administered only for a total of 6 to 8 hours. The antibiotics used most commonly are ampicillin (2 g either intramuscularly or intravenously) plus intravenous gentamicin (1.5 mg/kg, not to exceed 120 mg). Six hours later, 1 g of either ampicillin or amoxicillin is administered by the appropriate route. Vancomycin is substituted for women who are allergic to penicillin. Women in the negligible-risk category do not require prophylaxis for an uncomplicated delivery or if bacteremia (eg, intra-amniotic infection) is suspected at the time of delivery. Women in the moderate-risk category should receive prophylaxis if bacteremia is suspected, but it is not recommended for an uncomplicated delivery. If infection is suspected in women who fall in the high-risk category, prophylaxis should be given, but it is optional if the delivery is uncomplicated. (27) The dilemma this poses to most obstetricians is the inability to know which deliveries will be complicated; therefore, some clinicians administer prophylaxis to all women in the high-risk category. (1)(4)(14)(26)Anticoagulation with warfarin should be discontinued at least 2 weeks before delivery is anticipated and subcutaneous heparin therapy begun. Anticoagulation with heparin should be discontinued prior to active labor. The antidote for heparin, protamine sulfate, should be available for delivery if needed. Anticoagulation therapy can be resumed postpartum after stabilization, usually 6 to 12 hours after delivery. (4)The level of observation and assessment is maintained in the first several days postpartum because a significant number of deaths occur during this time. (1) Cardiac output may increase as much as 65% after delivery. (17) The greatest risks immediately postpartum are hemorrhage and pulmonary edema. More-than-average blood loss is treated with hemostasis and replacement of blood products and plasma as needed. Pulmonary edema may be seen up to 3 days postpartum or beyond, depending on the specific cardiac disease and complications encountered during pregnancy. The risk of pulmonary edema may increase postpartum as interstitial fluid is mobilized into the vascular space. (1) The number of days of close observation of the woman depends on the severity of cardiac disease. (25)The fetus/neonate is exposed not only to the risks associated with maternal cardiac disease in pregnancy, but also to the increased risk of genetic transmission of a cardiac defect. In the general population, the risk of congenital heart disease is less than 1%. When either parent is affected with congenital heart disease, the risk to the fetus increases 10-fold. Therefore, genetic counseling and fetal echocardiography are recommended in these cases. (4)(14)Babies born to pregnant women who have cardiac disease are at risk for neonatal and cardiac complications. (30) In one study, pregnant women who had heart disease were followed during 302 pregnancies, and the frequency of maternal cardiovascular and neonatal complications was compared with a group of women who did not have heart disease and who experienced a total of 572 pregnancies. (30) Neonatal complications, such as intraventricular hemorrhage, preterm delivery at less than 34 weeks’ gestation, and fetal/neonatal death, occurred in 6% of the group who had heart disease compared with 2% in the control group, a statistically significant difference.The relationship between maternal heart disease and neonatal complications is believed to be caused by maternal cyanosis, low maternal oxygen saturation, and uteroplacental insufficiency. Uteroplacental insufficiency can be linked to poor maternal NYHA functional classification and left heart obstruction. (30)(31) In the setting of maternal cardiac disease, especially functional class III and IV, intensive fetal surveillance with ultrasonography and antepartum testing is mandatory.The care of pregnant women who have cardiac disease is challenging. Preconception counseling is critical. Use of a well-informed multidisciplinary team, with close communication throughout pregnancy, is necessary to achieve the best possible outcome for the woman and her baby.

The primary function of the cardiopulmonary system is to provide blood flow (and oxygen) in quantities sufficient to support the metabolic needs of the body. The capacity of the cardiopulmonary system to fulfill this function is maximally stressed when an individual's metabolic rate is increased, a condition that occurs most commonly during physical activity/exercise. A number of physiological changes accompany and facilitate the accommodation of the circulatory system to the hemodynamic demands of exercise (Figure 1). In normal individuals, these changes (which during upright exercise include a tripling of the resting heart rate, a >60% reduction in systemic and pulmonary vascular resistance, and a >50% increase in stroke volume) can ultimately produce a >5-fold increase in cardiac output. The increase in cardiac output is accompanied by enhanced ventricular preload (as the ventricles move up their Starling curves to accommodate the increased workload), a doubling of systolic and mean pulmonary artery pressures (most of the increase in pulmonary artery pressures is due to the concomitant rise in left-sided filling pressures; the increase in transpulmonary pressure gradient is relatively small), and a more modest increase in systemic arterial pressures.1,–,4 Figure 1. Some of the physiological changes that accompany and facilitate the accommodation of the circulatory system to the hemodynamic demands of exercise. RAp indicates right atrial pressure; LAp, left atrial pressure; PVR, pulmonary vascular resistance; SVR, systemic vascular resistance; PAp, pulmonary artery pressure; and AOp, aortic pressure. Congenital heart disease (CHD) may, in a variety of ways and to a variable extent, adversely affect these hemodynamic adaptations. For instance, patients with a Fontan procedure lack a pulmonary ventricle. They therefore cannot increase their pulmonary blood flow and pressures normally (and consequently cannot maintain their ventricular preload and systemic blood flow) during exercise.5 Patients with tetralogy of Fallot and …

Patent Ductus Arteriosus in Pregnancy: Cardio-Obstetrics Management in a Late Presentation

The effects of substituting an infusion of salbutamol for isoprenaline were studied in 12 patients needing circulatory support after valve replacement surgery. The cardiac output rose while the heart rate remained unaltered. There was a reduction in systemic vascular resistance, and though the oxygen uptake tended to rise the increase in cardiac output was proportionately greater so that the arteriovenous oxygen difference fell.It is suggested that the drug is of value for two reasons. It causes a selective reduction in peripheral arteriolar resistance, which avoids peripheral pooling, but permits limited myocardial work to be used to generate flow rather than pressure, and the increase in cardiac output is not accompanied by a corresponding rise in oxygen uptake.

This study examined the hemodynamic and regional vascular profile of intravenous (i.v.) milrinone during increasing doses (3, 6, 12 micrograms/kg/min, n = 8) and by intraindividual comparison of milrinone and dobutamine (n = 10) in normal conscious rats. At 3 micrograms/kg/min, Milrinone increased coronary and cerebral blood flow (radioactive microspheres 15 +/- 5 microns) (7.7-9.8 and 1.05-1.27 ml/min/g respectively, both p less than 0.05) without significant changes in systemic hemodynamics. At 6 micrograms/kg/min milrinone increased skeletal muscle blood flow (0.19-0.24 ml/min/g, p less than 0.05) along with increases in cardiac output, stroke volume, and stroke work (all p less than 0.05), while systemic vascular resistance decreased (-51%, p less than 0.05). When compared with dobutamine, milrinone caused a greater increase in cardiac output (+26% vs. +17%) and a greater reduction in systemic vascular resistance. Milrinone and dobutamine increased renal, intestinal, cerebral, and coronary flow to a similar extent, but only milrinone enhanced hepatic arterial blood flow (+26%, p less than 0.05) and tended to increase flow to skeletal muscle (+35%, p = 0.07). We conclude that milrinone exerts significant regional vasodilating effects in a conscious rat model, being most prominent in the coronary and cerebral circulations at a dosage that does not alter central hemodynamics. At higher doses, milrinone causes a balanced increase in regional blood flow including enhanced flow to skeletal muscle. The hemodynamic (particularly as compared with dobutamine) and regional vascular profile of milrinone suggests a predominant vasodilating effect in the rat. Given a similar limited response of rat and diseased human myocardium to milrinone, these findings may have important clinical implications.

Angiotensin-converting enzyme inhibitors: More different than alike?: Focus on cardiac performance