Hypertrophic cardiomyopathy (HCM) is a genetic disorder with an incidence of 0.1% to 0.5% in pregnant women.1,2 With the cardiovascular changes associated with pregnancy, parturient women with preexisting heart disease, such as HCM, face an increased risk of morbidity and mortality from dysrhythmias and hemodynamic instability. In particular, pressure from the gravid uterus may impair venous return, reducing stroke volume and precipitating cardiac decompensation.3–5 In patients with HCM, this reduction in preload may exacerbate left ventricular outflow tract (LVOT) obstruction.6
There are only a few reports documenting the anesthetic management of parturients with HCM (Table 1). The literature suggests that epidural analgesia may be used if efforts are made to minimize systemic vasodilation and avoid hypotension.7–10 Transthoracic echocardiography (TTE) may help differentiate the causes of hypotension and guide management; however, TTE is not used commonly in obstetrical anesthesia.7,11–13 This case describes the use of TTE to guide anesthetic management of a 26-year-old parturient woman with known HCM who required urgent cesarean delivery for stable accelerated idioventricular rhythm. We obtained written consent from the patient to publish this report.
Our patient was a 26-year-old woman, G3P2, with known familial HCM. Her first pregnancy was an uncomplicated spontaneous vaginal delivery at term without neuraxial analgesia. Her second pregnancy was complicated by fetal situs inversus and intrauterine fetal demise at 37 weeks of gestation. She underwent induction of labor with lumbar epidural analgesia and had an uncomplicated vaginal delivery.
HCM was diagnosed after her second pregnancy after detection of a murmur. Although she had a positive family history of HCM, there had been no screening before the discovery of her peripartum heart murmur. HCM was documented by the use of TTE, which revealed severe concentric hypertrophy of the left ventricle (LV) with midcavitary obstruction. The dynamic outflow tract obstruction ranged from 100 to 130 mm Hg. The septal thickness was measured as 20 mm. The patient was clinically asymptomatic with only mild chronic fatigue. Given the high LVOT gradient and modest fatigue, she was treated with atenolol 25 mg daily.
For her third pregnancy, the patient attended the Congenital Heart Disease Clinic, starting at 16 weeks of gestation. She received preconception genetic counseling before this pregnancy and was counseled on the risk of future pregnancies. She declined DNA testing. Prenatal testing also was reviewed with the patient. She also declined prenatal testing. She would not consider termination of a pregnancy for either maternal or fetal reasons.
TTE was performed at 16 and 21 weeks of gestation. The latter (Fig. 1) revealed an intraventricular septal thickness of 36 mm with minimal systolic anterior motion of the mitral valve and minimal mitral regurgitation. The midcavitary peak instantaneous pressure gradient was 150 mm Hg (increased from 100 mm Hg at diagnosis). In addition, there was moderate pulmonary hypertension, with right ventricular systolic pressure = 56 mm Hg and right atrial pressure = 40 mm Hg.
She remained relatively asymptomatic during the first trimester, other than worsening fatigue and occasional nonsustained palpitations at 22 weeks of gestation. Her heart rate was approximately 100 bpm and arterial blood pressure stable, remaining >100 mm Hg systolic. She denied dyspnea and syncope. Her cardiologist titrated her dose of atenolol from 25 to 100 mg daily with a maternal heart rate goal 60 bpm. At 28 weeks of gestation, the atenolol dose was 100 mg daily, her heart rate was at target, and she reported feeling better. Retrospectively, she recognized she had been experiencing mild chest pressure and shortness of breath that now was resolved.
In the current pregnancy, twin A was known to have fetal situs inversus. Her pregnancy was further complicated by fetal growth discordance, with twin A at the 18th percentile and twin B at the sixth percentile, fetal abdominal circumference at less than the third percentile, and low amniotic fluid.
The patient was admitted to IWK Health Centre at 31 weeks of gestation for fetal surveillance. It was anticipated that an early delivery would be likely. At this time, the patient was asymptomatic with an arterial blood pressure 118/64 mm Hg, heart rate 85 bpm. Her admission electrocardiogram revealed normal sinus rhythm, left atrial enlargement, and LV hypertrophy. It was unchanged from her previous tracing (Fig. 2). Both fetuses were considered stable, determined by the use of routine nonstress tests, with normal reactivity and baselines for twin A and twin B (fetal heart rate 145 and 140 bpm, respectively).
The obstetric anesthesia team was consulted as part of the multidisciplinary management for this patient. Multidisciplinary plans for cesarean delivery were developed to account for her obstetrical and maternal cardiac status and urgency. If her cardiac status remained stable, she would undergo planned cesarean delivery with extended intraoperative monitoring and postpartum care in the high-acuity birth unit. Extended management would include arterial monitoring and TTE. Central pressure monitoring was deferred because of the risk of guidewire-precipitated ventricular arrhythmia. If her cardiac status deteriorated, she would be transferred urgently to the adult tertiary care hospital for cesarean delivery. Postoperative care would then be provided in the adult cardiovascular intensive care unit. If emergency delivery was indicated for either maternal or fetal compromise, cesarean delivery would proceed with a pediatric cardiologist immediately available and with TTE capability in the operating room.
On the sixth day of admission, the patient had an unwitnessed syncopal event. She reported feeling weak, short of breath, and experienced chest heaviness. On examination, she was alert and pale. Her vital signs were arterial blood pressure 64/50 mm Hg, heart rate 100 bpm, and oxygen saturation (SpO2) 100%.
She was immediately assisted back to her bed and placed in left uterine displacement position with administration of supplemental oxygen. A repeat systolic blood pressure was palpable at 75 mm Hg, heart rate 97 bpm, and SpO2 98%. The patient was given a 500-mL bolus of normal saline, resulting in rapid improvement of her symptoms: arterial blood pressure 106/68 mm Hg, heart rate 100 bpm, and SpO2 100%. External fetal monitoring showed a normal fetal heart rate for both twins (twin A 140 seconds and twin B 130 seconds). The patient’s electrocardiogram (Fig. 3) revealed a wide complex tachycardia at a rate of 100 to 110 beats per minute, consistent with accelerated idioventricular rhythm. She was transferred immediately from the antenatal inpatient ward to the birth unit.
Given her relatively slow heart rate and stabilized blood pressure, combined with the underlying degree of LV obstruction, the cardiologists elected not to attempt conversion to sinus rhythm. The concern was her risk for deterioration into a malignant cardiac rhythm (i.e., ventricular tachycardia or ventricular fibrillation). Because of the risk for maternal hemodynamic decompensation during transfer between hospitals, and the significantly limited emergency obstetrical and neonatal resources at the adult hospital, the decision was made to proceed with an urgent cesarean delivery at IWK Health Centre.
The patient was transferred to the operating suite. In the operating suite, the cardiac arrest cart was immediately available, and defibrillation pads were placed on the patient. A second 16-g large bore IV and arterial line monitoring were placed. An epidural catheter was placed at the L3-L4 interspace, with an 18-gauge Tuohy needle with the patient in left lateral position.
Lidocaine 240 mg (2% with epinephrine and bicarbonate) and 50 μg fentanyl were administered via the epidural catheter over 30 minutes. A phenylephrine infusion was initiated at 20 μg/min. During this initial slow induction of epidural anesthesia, the cardiologists performed an intraoperative TTE (Fig. 4). The TTE was used to assess LV function and filling throughout local anesthetic administration. This allowed titration of phenylephrine infusion rates and guided crystalloid administration to maintain ventricular filling. The goal was to maintain systolic blood pressure between 90 and 130 mm Hg. An intraoperative TTE revealed peak LVOT gradient = 98 mm Hg, right ventricular systolic pressure = 52 mm Hg, and septal wall thickness = 36 mm.
During skin preparation, the patient had a brief course (seconds) where she reverted to normal sinus rhythm. The first twin baby was delivered at 4:14 PM, weighing 1270 g, with Apgar scores of 6 (1 minute) and 8 (5 minutes). The second twin was delivered at 4:16 PM, weighing 1220 g, with Apgar scores of 8 (1 minute) and 9 (5 minutes). The patient remained in accelerated idioventricular rhythm during her operative course. After delivery of the second twin, oxytocin infusion (without bolus) was initiated at 0.5 IU/min for a total dose of 30 IU administered over 60 minutes. A further 25 mg ropivacaine and 2.5 mg morphine was administered via the epidural catheter. During skin closure, her cardiac rhythm converted to normal sinus rhythm at 60 bpm, and her systolic blood pressure increased to 140 mm Hg. Her estimated blood loss was 900 mL. We administered 2.4 L crystalloid during the 2-hour intraoperative time period (60 minutes of surgical time).
She was transferred to the postanesthetic care unit. Her electrocardiogram continued to show normal sinus rhythm. An amiodarone infusion was initiated at 54 mg/h. TTE demonstrated improvement in her cardiac function with her conversion to sinus rhythm (LVOT gradient = 85 mm Hg, right ventricular systolic pressure = 54 mm Hg).
After initial recovery, she was transferred to the adult cardiac care unit in a separate tertiary care hospital for intensive monitoring. She remained in sinus rhythm for the remainder of her hospitalization. After consultation with the electrophysiology service, an automated implantable cardiac defibrillator was inserted. She was discharged home on postoperative day 5, with no further complications during her stay.
HCM is an autosomal-dominant disease characterized by LV hypertrophy. The presentation of HCM is heterogeneous, depending on the site and extent of hypertrophy. Concurrent cardiac abnormalities include LVOT obstruction, diastolic dysfunction, myocardial ischemia, and mitral regurgitation.1,2 LVOT obstruction and mitral regurgitation are dynamic processes and may be exacerbated by decreased preload, decreased afterload, increased contractility, or tachycardia.
LVOT obstruction is considered the main risk factor for morbidity and mortality in HCM, occurring in 20% of patients at rest.1,10 LVOT obstruction typically occurs at the subaortic level as a result of systolic anterior motion of the anterior mitral valve leaflet.2,14 Approximately 5% of patients with HCM present with an obstruction at the midcavitary level with septal hypertrophy coming into contact with the LV free wall.9,14–16 Our patient presented with the latter scenario, having a severe midcavitary obstruction gradient of 150 mm Hg.
Generally, pregnancy is well tolerated in patients with HCM who are asymptomatic before conception; however, because of the variety of competing hemodynamic changes during pregnancy, it is not surprising that up to 47% of women report some symptoms during pregnancy.1,16,17 These symptoms may include chest pain, breathlessness, presyncope, and syncope. Cardiac complications include atrial or ventricular arrhythmias, heart failure, and sudden cardiac death. The rate of maternal morbidity is related to the level of functional class before pregnancy.17 Although our patient reported being asymptomatic before pregnancy, she admitted to symptoms of shortness of breath and chest heaviness in retrospect after she noted an improvement after β-blockade therapy. She also had significant asymmetrical ventricular hypertrophy, with a severe midcavitary obstruction. As such, she was considered a high-risk patient. Her prepregnancy counseling reflected this.
The finding of accelerated idioventricular rhythm in our patient presented a unique challenge. The predominant dysrhythmia described in the literature with HCM is generally nonsustained ventricular tachycardia, polymorphic ventricular tachycardia, or ventricular fibrillation.7,18 The term idioventricular rhythm is used when the ventricle becomes the primary pacemaker, usually in response to sinus slowing. Accelerated idioventricular rhythm is seen commonly in athletes during periods of increased vagal tone with decreased sympathetic tone. Accelerated idioventricular rhythm is generally a transient rhythm, rarely causing hemodynamic instability or requiring treatment. Symptoms are related to decreased cardiac output: hypotension, dizziness, syncope, and chest pain. Accelerated idioventricular rhythm has been reported during cesarean delivery in healthy women during spinal anesthesia for cesarean delivery. In this setting, it has been attributed to vagal imbalance and is generally of little clinical significance.19
The clinical feature that differentiates between an accelerated idioventricular rhythm and ventricular tachycardia is rate. Ventricular tachycardia typically has a rate of >120 bpm. The rate is significant because ventricular tachycardia is more likely to deteriorate into ventricular fibrillation and sudden cardiac death, requiring a much more aggressive approach.8,16,19
Although it is difficult to determine the cause of her syncopal episode, it is reasonable to hypothesize that the accelerated idioventricular rhythm played a dominant role, combined with an abrupt decrease in preload when she stood up, exacerbating her LVOT.16
The goals for anesthetic management included avoidance of tachycardia, hypotension, and restoration of sinus rhythm. Epidural analgesia must be used cautiously in patients with HCM to avoid decreasing preload and increasing heart rate. Nonetheless, there are several successful cases of patients with HCM who received epidural anesthesia for cesarean delivery, even in the face of significant LVOT obstruction (Table 1).
Epidural anesthesia generally is considered safer than general anesthesia in patients with HCM because of its slow onset, precise drug titration, and avoidance of other risks of general anesthesia.2,7–10,14,20 Spinal anesthesia generally is avoided because of the rapid onset of sympathetic block and the potential for profound hypotension. We decided to use epidural anesthesia without concurrent spinal anesthesia. We used lidocaine 2% for the initial local anesthetic block to produce a sufficiently rapid onset. We used ropivacaine to extend epidural block duration partly because ropivacaine may have less cardiotoxicity than bupivacaine.21 Epidural anesthesia was combined with an IV phenylephrine infusion to mitigate any potential hypotension. Phenylephrine was selected because it is a potent peripheral vasoconstrictor without chronotropic side effects.2,7,8
TTE is relatively novel in obstetric anesthesia. This case is one of the few described in the literature in which TTE was available pre-, intra-, and postoperatively to monitor cardiac function and response to both epidural anesthetic management and phenylephrine infusion rates. TTE monitoring is particularly useful in the serial assessment of hemodynamically unstable patients with HCM to assess volume status, LVOT obstruction, LV cavity size, the degree and nature of mitral regurgitation, and LV systolic and diastolic function.
With pregnancy, anatomic displacement of the heart by the gravid uterus may alter the position of the heart and vessels. Surgery, including supine positioning and surgical drapes at the costal margin, may further challenge TTE assessment. With multidisciplinary planning, our patient presented an opportunity for the planned use of noninvasive monitoring using TTE.
This case demonstrates the use of TTE to assist in the anesthetic management of a parturient woman with HCM undergoing cesarean delivery for acute cardiovascular decompensation. It also demonstrates the utility of anticipatory multidisciplinary planning, assuring that the resources and expertise were immediately available when the decision was made to proceed with urgent cesarean delivery at the time of her cardiac decompensation.
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