Obstetric Anesthesia and Heart Disease: Practical Clinical Considerations

Marie-Louise Meng, M.D.; Katherine W. Arendt, M.D.

Anesthesiology. 2021;135(1):164-183.

Abstract and Introduction

Abstract

Maternal morbidity and mortality as a result of cardiac disease is increasing in the United States. Safe management of pregnancy in women with heart disease requires appropriate anesthetic, cardiac, and obstetric care. The anesthesiologist should risk stratify pregnant patients based upon cardiac disease etiology and severity in order to determine the appropriate type of hospital and location within the hospital for delivery and anesthetic management. Increased intrapartum hemodynamic monitoring may be necessary and neuraxial analgesia and anesthesia is typically appropriate. The anesthesiologist should anticipate obstetric and cardiac emergencies such as emergency cesarean delivery, postpartum hemorrhage, and peripartum arrhythmias. This clinical review answers practical questions for the obstetric anesthesiologist and the nonsubspecialist anesthesiologist who regularly practices obstetric anesthesiology.

Introduction

Maternal mortality is increasing in the United States, and cardiovascular disease is now the leading cause.^[1,2] According to the Centers for Disease Control and Prevention, cardiovascular disease is currently responsible for one-quarter of maternal deaths in the United States and similar trends are occurring in other high-income countries.^[2–4] These trends may be a result of an increasing average age of maternity during the last 4 decades, compounded by increases in known risk factors for cardiovascular disease such as diabetes, hypertension, and obesity.^[5–7]

With improvements in the surgical and medical management of congenital heart disease, the number of women with congenital heart disease who survive to childbearing years and present to labor and delivery units in the United States has increased.^[8] The European Society of Cardiology's Registry of Pregnancy and Cardiac Disease has recorded more than 5,700 pregnancies in women with cardiovascular disease, 57% of whom had congenital heart disease. Based on the Registry of Pregnancy and Cardiac Disease data, patients with congenital heart disease with appropriate cardiac and obstetric care do well, with relatively low rates of morbidity and mortality compared to other types of heart disease.^[3] In contrast, patients at the highest risk of cardiovascular complications and death in pregnancy are women who are older, identify as Black or African American, acquire heart disease in pregnancy, and/or have unrecognized cardiovascular disease and become pregnant.^[1,9–11]

There are little data to guide the anesthetic management of women with cardiac disease. Statements by the American Heart Association (Dallas, Texas), European Society of Cardiology (Sophia Antipolis Cedex, France), Society of Maternal–Fetal Medicine (Washington, D.C.), and American College of Obstetricians and Gynecologists (Washington, D.C.) provide valuable guidance regarding the diagnosis and management of cardiovascular disease preconception, in pregnancy, and in the peripartum and postpartum periods.^[12–14] These guidelines recommend that a "pregnancy heart team" care for pregnant patients with complex cardiovascular disease. Such a team is defined as cardiologists, obstetricians, perinatologists, and anesthesiologists. Through a nonsystematic literature review with incorporation of national and international guidelines, this Clinical Review answers practical questions for the obstetric anesthesiologist and the nonsubspecialist anesthesiologist who regularly practices obstetric anesthesiology. Besides society statements and guidelines, many of the suggestions in this review are based on hemodynamic and physiologic extrapolation and advice from other experts.

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Next Section

Abstract and Introduction
Discussion
References

Table 1. Modified World Health Organization Classification of Cardiovascular Disease in Pregnancy ^1,2
Risk Classification	Cardiac Lesions
Class I No detectable increased risk of maternal mortality and no or minimal increase in maternal morbidity	• Uncomplicated mild pulmonary stenosis • Ventricular septal defect • Patent ductus arteriosus • Mitral valve prolapse with no more than trivial mitral regurgitation • Successfully repaired simple lesions (atrial or ventricular septal defect, patent ductus arteriosus, anomalous pulmonary venous drainage) • Isolated ventricular extra-systoles and atrial ectopic beats
Class II Small increased risk of maternal mortality or moderate increase in morbidity	• Unrepaired atrial or ventricular septal defect • Repaired tetralogy of Fallot • Most arrhythmias
Class II–III Moderate increased risk of maternal mortality or morbidity	• Hypertrophic cardiomyopathy • Native or tissue valvular heart disease not considered Modified World Health organization I or IV • Repaired coarctation • Marfan syndrome without aortic dilatation • Bicuspid valve with aorta <45 mm • Mild ventricular impairment • Heart transplantation
Class III Significantly increased risk of maternal mortality or severe morbidity, and expert cardiac and obstetric prepregnancy, antenatal, and postnatal care are required	• Mechanical valve • Systemic right ventricle • Fontan circulation • Unrepaired cyanotic heart disease • Other complex congenital heart disease • Marfan syndrome with aorta 40–45 mm • Bicuspid aortic valve with aorta 45–50 mm
Class IV Pregnancy is highly discouraged	• Pulmonary hypertension • Eisenmenger syndrome • Systemic ventricular ejection fraction <30% • Systemic ventricular dysfunction with New York Heart Association class III–IV • Severe mitral stenosis or symptomatic aortic stenosis • Marfan syndrome with aorta >45 mm • Bicuspid aortic valve with aorta >50 mm • Native severe coarctation • Previous peripartum cardiomyopathy with any residual impairment of ventricular function

Table 2. Maternal Levels of Care ³
Level	Title	Maternal Health	Hospital Capabilities	Anesthesia Staffing	Modified World Health Organization Patients*
Birth center	Birth center	Low risk	Not applicable	None	None
Level I	Basic care	Low to moderate risk	Limited obstetric ultrasound	Anesthesia provider readily available at all times	Modified World Health Blood bank Organization class I
Level II	Specialty care	Moderate to high risk	Computed tomography scanning/magnetic resonance imaging Maternal echocardiogram Nonobstetric ultrasound	Anesthesiologist readily available at all times	Modified World Health Organization class I or II
Level III	Subspecialty care	More complex maternal, obstetric and fetal conditions	Interventional radiology In-house capability of all blood components	Board-certified anaesthesiologist physically present at all times	Modified World Health Organization class I or II, some III
Level IV	Regional perinatal health center	Most complex maternal conditions	ICU care with Maternal Fetal Medicine comanagement Cardiovascular surgery, ECMO, and transplant capabilities	Board-certified anesthesiologist with obstetric anesthesia fellowship or experience in obstetric anesthesia physically present at all times	Modified World Health Organization class I, II, III, or IV

*The addition of the Modified World Health Organization classifications into the Maternal Levels of Care is an extrapolation based upon Drs. Meng and Arendt's experience, and is not a direct recommendation from the American College of Obstetricians and Gynecologists, Society of Maternal–Fetal Medicine, or Modified World Health Organization.
ECMO, extracorporeal membrane oxygenator; ICU, intensive care unit

Table 3. Anesthetic Care Steps for Pregnant Women with Known Cardiovascular Disease
Predelivery Consultation with the Anesthesiology Service
1. Summarize cardiovascular, obstetric, and anesthesia history and risk factors 2. Cardiac history should focus on: a. Previous surgeries, echocardiograms, electrocardiograms, Holter monitors, stress tests, heart catheterization, etc. b. Previous or current episodes of heart failure c. Intracardiac shunting and cyanosis d. Previous arrhythmias e. L eft heart obstructive lesions f. L eft and right heart function 3. Risk stratify according to the Modified World Health Organization criteria 4. Participate in multidisciplinary planning of labor and delivery 5. With obstetric team, plan appropriate delivery location according to maternal levels of care 6. Partner with pregnancy heart team* for anticoagulation regimen to optimize ability to perform neuraxial techniques 7. Clarify in the consultation note plan for pacemaker or defibrillator (keep automatic implantable cardioverter defibrillator "on" during labor or cesarean delivery 8. Clarify in the consultation notes which obstetric drugs could cause hemodynamic instability (see table 5) 9. Partner with pregnancy heart team* to clarify in the consultation notes postdelivery plans for monitoring
Trial of Labor
1. Besides standard labor monitoring, also consider monitoring with: a. Pulse oximetry with a wave form b. Five-lead electrocardiography if at risk for tachyarrhythmia or cardiac ischemia c. Intraarterial blood pressure monitoring if at risk for hemodynamic instability with induction of neuraxial or general anesthesia 2. Initiate neuraxial analgesia early in labor (unless contraindication) 3. Do not use a routine preepidural fluid bolus in patients at risk for pulmonary edema 4. Consider modifying epidural test dose to minimize the risk of high spinal or intravascular epinephrine 5. Monitor for hypotension closely during induction of neuraxial labor analgesia and treat with goal-directed fluids and vasopressors (e.g., phenylephrine, norepinephrine, and ephedrine) to maintain normal blood pressure 6. Readily replace suboptimal epidural catheter 7. Keep epidural block dense enough throughout labor such that it eliminates pain and catecholamine release, facilitates operative vaginal delivery, and can quickly be converted to a surgical block in the event of an obstetric emergency
Cesarean Delivery
1. Low threshold to monitor with intraarterial blood pressure 2. Perform neuraxial anesthesia if no contraindications (choose epidural, sequential combined spinal epidural, or single-shot spinal based upon presumed tolerance of sympathectomy) 3. Titrate vasopressor infusion (e.g., phenylephrine or norepinephrine) to maintain blood pressure 4. Titrate oxytocin on an infusion pump
Postpartum
1. Titrate oxytocin on an infusion pump 2. Monitor for postpartum hemorrhage and treat rapidly 3. In most cardiovascular patients, risks of methylergonovine and carboprost may outweigh the benefits of these uterotonics medications (see table 5) 4. More intense monitoring postpartum (e.g., five-lead electrocardiographic monitoring, continuous pulse oximetry) may be indicated in patients with Modified World Health Organization class III or IV lesions, or those who experience obstetric or cardiac complications during labor or delivery. This may require intensive care or step-down unit admission.
*An institution's team of cardiologists, obstetricians, perinatologists, and anesthesiologists focused on the care of pregnant women with cardiovascular disease.

Table 4. Hemodynamic Effects of Pregnancy and Anesthetic Management Considerations in Specific Cardiovascular Diseases ²¹
	Effects of Pregnancy and Delivery	Management Considerations
Coronary artery disease	(-) Decrease in SVR can result in reduced diastolic blood pressure and thereby decreased coronary perfusion pressure (-) Increase in heart rate can result in decreased coronary filling time (-) Cardiac work can increase significantly during labor	Normal heart rate (avoid tachycardia): • Maintain effective neuraxial labor analgesia • Continue β-blockade through labor and delivery • Avoid β-agonist agents (e.g., terbutaline) Maintain afterload: • Consider intraarterial blood pressure monitoring • Consider phenylephrine for vasopressor of choice • Carefully titrate neuraxial anesthesia onset for labor or cesarean delivery • Consider prophylactic phenylephrine infusion for cesarean delivery • Titrate oxytocin carefully • Early recognition and aggressive response to hemorrhage Monitor for and avoid ischemia: • Five-lead electrocardiographic monitoring for cesarean delivery or labor • Avoid methylergonovine • Recognize and carefully treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring) Postpartum monitoring: • Monitor for postpartum ischemia or heart failure
Severe left ventricular dysfunction (e.g., dilated or peripartum cardiomyopathy)	(-) Increase in cardiac output and blood volume can result in heart failure and pulmonary edema (-) Decrease in oncotic pressure can result in pulmonary edema (-) Patients with previous episode of peripartum cardiomyopathy are at risk for further deterioration in left ventricular function with subsequent pregnancies (-) Angiotensin-converting enzyme inhibitors are discontinued due to teratogenicity	Normal heart rate (avoid bradycardia): • Treat bradycardia with ephedrine or glycopyrrolate Maintain afterload (avoid hypertension or hypotension): • Consider intraarterial blood pressure monitoring • Maintain effective neuraxial labor analgesia • Carefully titrate neuraxial anesthesia onset for labor or cesarean delivery • Treat hypotension with ephedrine or norepinephrine • Titrate oxytocin carefully • Recognize and carefully treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring) • Early recognition and aggressive response to hemorrhage Maintain contractility: • Consider ephedrine for vasopressor of choice • If low cardiac output syndrome develops, consider milrinone or dobutamine with the addition of epinephrine or norepinephrine to maintain blood pressure Prevent and monitor for pulmonary edema: • Careful fluid balance • Continuous pulse oximetry throughout labor and peripartum (including postpartum) Manage pulmonary edema: • Consider diuresis • Administer supplemental oxygen • Labor in upright position • If necessary, consider intubation with positive end expiratory pressure and controlled ventilation Monitor for and avoid ischemia or arrythmia: • Five-lead electrocardiographic monitoring for cesarean delivery or labor Manage automatic implantable cardioverter defibrillator, if present: • Keep antitachyarrhythmia function of automatic implantable cardioverter defibrillator active in labor and may be kept active in the event of emergent cesarean delivery Minimize pulmonary vascular resistance: • Administer supplemental oxygen • Avoid oversedation • Assure well-controlled ventilation if intubated • Avoid carboprost Postpartum monitoring: • Monitor for postpartum heart failure
Pulmonary hypertension	(-) Increased cardiac output may not be accommodated by the fixed pulmonary vasculature resulting in right heart failure (-) Decrease in SVR can result in reduced diastolic blood pressure and thereby decreased coronary perfusion pressure especially in a dilated and failing right ventricle (-) Hypercoagulable state can result in pulmonary emboli which can exacerbate pulmonary hypertension	Minimize pulmonary vascular resistance: • Administer supplemental oxygen • Avoid oversedation, hypercapnia • Maintain effective neuraxial labor analgesia • Assure well-controlled ventilation if intubated • Avoid carboprost Maintain adequate blood volume and venous return: • Strict monitoring of fluid balance • Recognize and carefully treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring) • Early recognition and aggressive response to hemorrhage Avoid myocardial depressants: • Avoid β-blockade if possible Monitor for and avoid ischemia or arrythmia: • Five-lead electrocardiographic monitoring for cesarean delivery or labor Maintain afterload: • Consider intraarterial blood pressure monitoring • Careful titration of onset of neuraxial anesthetic for labor or cesarean delivery • Consider phenylephrine for vasopressor of choice • Titrate oxytocin carefully Invasive pulmonary artery catheter monitoring as well as vasoactive agents may be necessary: • Consider partnership with cardiovascular anesthesiologist Postpartum monitoring: • Monitor for postpartum heart failure
History of unstable arrhythmia	(-) Pregnancy, labor, and delivery can incite tachyarrhythmias which can be associated with poor fetal outcome	Minimize maternal plasma catecholamines: • Maintain effective neuraxial labor analgesia • Consider avoiding epinephrine-containing local anesthetics (including in a test dose) • Avoid ephedrine and terbutaline • Recognize and carefully treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring) • Early recognition and aggressive response to hemorrhage Identify arrhythmias rapidly: • Five-lead electrocardiographic monitoring for labor, cesarean delivery, and postpartum Cardiovert unstable tachyarrhythmias rapidly: • Cardioversion can be performed in pregnancy • With tachyarrhythmia, consider fetal distress an indication for cardioversion Manage pacemaker/automatic implantable cardioverter defibrillator, if present: • Keep antitachyarrhythmia function of automatic implantable cardioverter defibrillator active in labor and may be kept active in the event of emergent cesarean delivery Postpartum monitoring: • Monitor for postpartum arrhythmia
Aortopathy (e.g., Marfan syndrome)	(-) Pregnancy, labor, and delivery may increase dilation of aortic root and increase the risk of aortic dissection (-) Maternal Valsalva maneuver may result in increased arterial sheer stress	Minimize aortic wall tension: • Maintain effective neuraxial labor analgesia • Continue β-blockade through labor and delivery • Cardio-Obstetrics may recommend cesarean delivery or no Valsalva during second stage Minimize hemodynamic fluctuations: • Carefully titrate neuraxial anesthesia onset for labor or cesarean delivery • Consider intraarterial blood pressure monitoring • Avoid methylergonovine and carboprost • Titrate oxytocin carefully • Recognize and carefully treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring) • Early recognition and aggressive response to hemorrhage Postpartum monitoring: • Monitor for postpartum hemodynamic instability
Valvular lesions
Mechanical prosthetic valve	(-) Hypercoagulable state of pregnancy increases risk of valve thrombosis (-) Vitamin K antagonists (most effective way to prevent valvular clot formation) are teratogenic. Suboptimal anticoagulation regimens may be used during pregnancy	Balance risk of anticoagulation therapy and anesthesia technique: • Perform general anesthesia for cesarean delivery in patients who are anticoagulated Recognize anticoagulation also increases risk of intrapartum and postpartum hemorrhage: • Select and/or titrate uterotonics carefully depending on underlying cardiac disease recognizing that oxytocin decreases SVR, methylergonovine behaves as an adrenergic alpha agonist and carboprost increases pulmonary vascular resistance significantly • Postpartum monitoring • Monitor for postpartum valvular clotting or obstetric bleeding
Mitral stenosis	(-) Elevation in blood volume and heart rate increases left atrial pressure which may lead to atrial fibrillation and pulmonary edema (-) Because of relatively fixed preload to the left ventricle, the heart may not adequately generate increased cardiac output (-) Decreased oncotic pressure further increases risk of pulmonary edema	Normal heart rate (avoid tachycardia): • Maintain effective neuraxial labor analgesia • Continue β-blockade through labor and delivery • Five-lead electrocardiographic monitoring for cesarean delivery or labor • Avoid β-agonist agents (e.g., terbutaline) • Early recognition and aggressive response to hemorrhage • Avo Atrial fibrillation • In new-onset atrial fibrillation, cardioversion should be considered • In failed cardioversion and in cases with chronic atrial fibrillation, treat rapid ventricular rate with medical therapy Prevent and monitor for pulmonary edema: • Careful fluid balance • Continuous pulse oximetry throughout labor and peripartum (including postpartum) • Recognize and carefully treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring) Manage pulmonary edema: • Consider diuresis • Administer supplemental oxygen • Labor in upright position • If necessary, consider intubation with positive end expiratory pressure and controlled ventilation Postpartum monitoring: • Monitor for postpartum pulmonary edema
Aortic stenosis/hypertrophic obstructive cardiomyopathy	(-) Decrease in SVR can result in reduced diastolic blood pressure and therefore decreased coronary perfusion pressure to the thickened left ventricle myocardium (-) Left ventricle diastolic dysfunction and excess volume can lead to pulmonary edema	Maintain afterload (avoid hypotension and hypovolemia): • Consider intraarterial blood pressure monitoring • Carefully titrate neuraxial anesthesia onset for labor or cesarean delivery • Treat hypotension with phenylephrine • Avoid nonspecific β-agonist agents (e.g., terbutaline) • Titrate oxytocin carefully • Early recognition and aggressive response to hemorrhage Normal heart rate (avoid tachycardia): • Maintain effective neuraxial labor analgesia • Prevent and monitor for ischemia • Five-lead electrocardiographic monitoring for cesarean delivery or labor • Recognize and carefully treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring) Maintain normovolemia: • Strict monitoring of fluid balance • Postpartum monitoring • Monitor for postpartum hypotension or ischemia
Mitral/aortic insufficiency	(+) Decreased SVR results in a lower regurgitant volume (-) Pregnancy can worsen ventricular dilation	Avoid increases in SVR and decreases in contractility: • Maintain effective labor analgesia • Avoid bradycardia • In cesarean delivery under spinal anesthesia, if prophylactic phenylephrine administered, carefully titrate and treat bradycardia. Alternatively, consider norepinephrine Maintain sinus rhythm: • Maintain effective neuraxial labor analgesia • Consider afterload reduction • Neuraxial analgesia/anesthesia typically well tolerated if preserved ventricular function • Recognize and aggressively treat hypertensive disorders of pregnancy (e.g., consider intraarterial monitoring)
Shunt lesions
Right-to-left shunt (e.g., tetralogy of Fallot, Eisenmenger syndrome)	(-) Decreased SVR increases right-to-left shunting and possible cyanosis (+) In unrepaired tetralogy of Fallot and normal right ventricle function, the increase in blood volume is beneficial because adequate right ventricular preload is necessary to eject blood past the outflow obstruction and increase pulmonary blood flow*	Maintain afterload and recognize worsening cyanosis: • Continuous pulse oximetry throughout labor and peripartum (including postpartum) • Treat cyanotic episodes with phenylephrine • Consider intraarterial blood pressure monitoring • Carefully titrate neuraxial anesthesia onset for labor or cesarean delivery • Titrate oxytocin carefully • Minimize pulmonary vascular resistance • Administer supplemental oxygen throughout labor and delivery • Avoid oversedation • Maintain effective neuraxial labor analgesia • Assure well-controlled ventilation if intubated • Avoid carboprost Maintain adequate blood volume and venous return: • Strict monitoring of fluid balance • Avoid supine position • Early recognition and aggressive response to hemorrhage Avoid myocardial depressants because any decrease in right ventricular contractility can decrease pulmonary circulation: • Avoid β-blockade if possible • Five-lead electrocardiographic monitoring for cesarean delivery or labor If pulmonary vascular disease is present, invasive pulmonary artery catheter monitoring, as well as vasoactive agents, may be necessary: • Consider partnership with cardiovascular anesthesiologist Avoid paradoxical embolism: • Place filters on intravenous lines • Perform epidural loss of resistance technique with saline not air • Postpartum monitoring • Monitor for postpartum cyanosis
Left-to-right shunt (e.g., ventricular septal defect or atrial septal defect)	(+) Decrease in SVR decreases left-to-right shunting (-) Increase in blood volume can precipitate failure because the patient is in a state of compensatory hypervolemia	Avoid excessive fluid administration, overtransfusion, and Trendelenburg position: • Strict monitoring of fluid balance • Early recognition and careful response to hemorrhage • Avoid increases in afterload • Maintain effective neuraxial labor analgesia Avoid paradoxical embolism: • Place filters on intravenous lines • Perform epidural loss of resistance technique with saline and not air

Modified from Arendt²⁰ and Arendt and Lindley.²¹
*Cyanotic congenital heart disease, Eisenmenger syndrome, and all pulmonary vascular hypertensive diseases carry a high mortality rate in pregnancy, labor, delivery, and the postpartum period.
(-) indicates deleterious physiologic change; (+) indicates favorable physiologic change; SVR, systemic vascular resistance.

Table 5. Signs and Symptoms Indicating a Prompt Evaluation by the Pregnancy Heart Team*
Vital Signs	Physical Exam Signs	History and Symptoms
Heart rate ≥ 120 beats/min	Jugular venous pressure visible 2 cm above clavicle at 45°	History of cardiovascular disease
Systolic blood pressure ≥ 160 mm Hg	Loud systolic murmur or S4	Shortness of breath at rest, paroxysmal nocturnal dyspnea, orthopnea, refractory pneumonia, or bilateral chest infiltrates on chest radiography
Symptomatic low blood pressure	Wheezing	Chest pain at rest or minimal exertion
Respiratory rate ≥ 25 breaths/min	Lung crackles	Exertional or unprovoked syncope or palpations associated with near syncope or syncope
Oxygen saturation < 95%	Marked peripheral edema	Extreme fatigue

Modified from American College of Obstetricians and Gynecologists.¹⁴
*An institution's team of cardiologists, obstetricians, perinatologists, and anesthesiologists focused on the care of pregnant women with cardiovascular disease.

Table 6. Side Effects of Medications Commonly Used for Obstetric Care
Medication (Class)	Cardiopulmonary Effects	Lesions for Which Medication Is Relatively Contraindicated	Notes
Oxytocin (uterotonic)	↓ SVR and MAP Slight ↑pulmonary vascular resistance and PAP	Most cardiac patients tolerate oxytocin if carefully titrated	Effective uterotonic agent Administer slowly via infusion pump in patients intolerant of ↓ MAP Consider counteracting ↓ MAP with phenylephrine infusion Do not administer in bolus intravenous form in patients with cardiac disease
Misoprostol (uterotonic)	None	None	Least effective uterotonic agent Can be used prophylactically
Methylergonovine (uterotonic)	↑ SVR ↑Pulmonary vascular resistance	Hypertension Preeclampsia Pulmonary hypertension Ischemic disease Intracardiac shunts Aortopathy	Mechanism similar to an α-adrenergic agent Generally avoided in cardiac patients
Carboprost (uterotonic)	↑ PAP Bronchospasm resulting in ventilation perfusion mismatch	Fontan circulation Intracardiac shunt Pulmonary hypertension	Prostaglandin F2α Do not use in patients who cannot tolerate increased PAP
Terbutaline (uterine relaxant)	↑ Heart rate ↑ Myocardial contractility ↓ SVR	Hypertrophic obstructive cardiomyopathy History of tachyarrhythmias	β-agonist