PBLD6: Anesthetic Management of Hypertrophic Obstructive Cardiac Disease in Pregnancy

Patients with hypertrophic cardiomyopathy (HOCM/ HCM) have enlargement of heart muscle tissue (hypertrophy of the left ventricle) with the possibility of resulting impairment of cardiac function.(1) Frequently, this is manifested by left ventricular outflow tract (LVOT) obstruction and associated mitral regurgitation.(2)

In parturients in labor, pain-related sympathetic stimulation leading to an increased release of catecholamines can worsen the degree of LVOT obstruction, resulting in hemodynamic instability. Sympathomimetic medications such as ephedrine should be avoided in favor of medications such as phenylephrine which maintain a low heart rate while increasing blood pressure. Furthermore, dyspnea is a common symptom when LVOT obstruction occurs. Other symptoms associated with LVOT obstruction include dizziness, fatigue, and episodes of syncope.(3)

Given that this patient’s cervical examination shows 2cm dilation and she is having mild pain, she is most likely in early labor and does not require neuraxial anesthesia at this time. Hemodynamic control of the patient with appropriate pharmacologic therapy is the best option to optimize the patient’s hemodynamic profile.

References:

1. Maron, B. J., & Braunwald, E. (2012). Evolution of hypertrophic cardiomyopathy to a contemporary treatable disease. Circulation, 126(13), 1640-1644. doi:10.1161/CIRCULATIONAHA.112.123174
2. Gersh, B. J., Maron, B. J., Bonow, R. O., Dearani, J. A., Fifer, M. A., Link, M. S., . . . Yancy, C. W. (2011). 2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: executive summary: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol, 58(25), 2703-2738. doi:10.1016/j.jacc.2011.10.825
3. Stroumpoulis, K. I., Pantazopoulos, I. N., & Xanthos, T. T. (2010). Hypertrophic cardiomyopathy and sudden cardiac death. World J Cardiol, 2(9), 289-298. doi:10.4330/wjc.v2.i9.289

HOCM can lead to outflow obstruction which is caused by narrowing of the LVOT due to hypertrophy of cardiac muscle. Abnormal systolic anterior motion (SAM) of the mitral valve can also lead to LVOT obstruction secondary to abnormal flow across the mitral valve pulling the mitral valve leaflets anteriorly and leading to dynamic obstruction.(4) LVOT obstruction and MR are best evaluated by the parasternal long axis view which is obtained by placing the echo transducer in the 3rd-4th intercostal space (left of sternum). With this view, the transducer orientation marker is pointing toward the patient’s right shoulder (~10 o’clock) which provides optimal visualization of the LVOT and also allows visualization of the mitral valve (see Figure 1).

Image courtesy of Antonio Hernandez Conte, MD, MBA.

Figure 1.
Left: Correct probe location for obtaining parasternal long axis view. Probe placement is in the 3rd-4th intercostal space with the transducer orientation marker pointing toward the patient’s right shoulder.
Right: Parasternal long axis view allows visualization of the left atrium, left ventricle, aortic valve and left ventricular outflow tract.

Reference:

4.  Sherrid MV, Gunsburg DZ, Moldenhauer S, Pearle G. Systolic anterior motion begins at low left ventricular outflow tract velocity in obstructive hypertrophic cardiomyopathy. J Am Coll Cardiol 2000; 36:1344–1354.

Epidural anesthesia can be used safely in patients with HOCM and has been shown to be safe in patients with severe LVOT obstruction.(6) Careful consideration to avoid an acute drop in preload, tachycardia, and hypotension must be ensured. Of particular importance, placement of epidural anesthesia early in the course of labor can help prevent pain-induced tachycardia, providing optimal hemodynamic conditions. Spinal anesthesia (including combined spinal epidurals) should be avoided due to the rapid drop in preload associated with sympathetic blockade, potentially exacerbating LVOT obstruction. In the event of a Cesarean section, epidural anesthesia with careful titration can be used safely. Early placement of epidural anesthesia is imperative in laboring patients due to the risks of anesthesia-related complications associated with general anesthesia should Cesarean delivery be required.(8)

References:

6. DesRoches, J. M., McKeen, D. M., Warren, A., Allen, V. M., George, R. B., Kells, C., & Shukla, R. (2016). Anesthetic Management Guided by Transthoracic Echocardiography During Cesarean Delivery Complicated by Hypertrophic Cardiomyopathy. A A Case Rep, 6(6), 154-159. doi:10.1213/XAA.0000000000000275

8. Hawkins, J. L., Koonin, L. M., Palmer, S. K., & Gibbs, C. P. (1997). Anesthesia-related deaths during obstetric delivery in the United States, 1979-1990. Anesthesiology, 86(2), 277-284.

Left uterine displacement achieved with a 15 degree left tilt of the supine patient, has been shown to improve maternal hemodynamics by improving cardiac output and reducing total phenylephrine usage in patients receiving spinal anesthesia.9 Although clinically significant changes such as dizziness related to hypotension (also referred to as “supine hypotension syndrome”) only occurs in 8-10% of parturients, this practice is recommended in all parturients regardless of medical history.(10-11)

In patients with HOCM, a decrease in preload and accompanying tachycardia can produce significant hemodynamic compromise by increasing the degree of LVOT obstruction.

References:

10. NICE, NIfHaCE: Clinical guidelines and updates: Caesarean section. Available at: https://www.nice.org.uk/guidance/ cg132/chapter/1-guidance. Accessed May 26, 2016
11. Practice guidelines for obstetric anesthesia: An updated report by the American Society of Anesthesiologists Task Force on Obstetric Anesthesia and the Society for Obstetric Anesthesia and Perinatology. ANESTHESIOLOGY 2016; 124:270–300

Cardiovascular physiology in pregnancy and in the post-partum period is imperative for anesthesiology providers to understand. These changes have direct implications for parturients with cardiovascular conditions sensitive to abrupt hemodynamic changes that accompany pregnancy. Prominent changes include increases in cardiac output notable at 5 weeks of gestation and increasing dramatically in the immediate post-partum period.(13) To accommodate increases in blood volume and cardiac output, hormonal-induced changes dramatically decrease systemic vascular resistance beginning in the first trimester and through delivery.(13)

In patients with no significant heart failure, regurgitant cardiac lesions such as mitral, tricuspid and aortic regurgitation are well tolerated in pregnancy due to the decrease in systemic vascular resistance which leads to a total decrease in regurgitant flow.(13) This decrease in systemic vascular resistance can exacerbate right-to-left shunting seen in patients with Eisenmenger syndrome.(14) However, in the immediate post-partum period, there is a significant rise in systemic vascular resistance which can exacerbate regurgitant lesions. Therefore regurgitant lesions are poorly tolerated postpartum, while the rapid increase in systemic vascular resistance is more favorable in stenotic lesions. This highlights the postpartum period as a critical interval for parturients with significant cardiac conditions and warrants close monitoring.

References:

13. Hall, M. E., George, E. M., & Granger, J. P. (2011). [The heart during pregnancy]. Rev Esp Cardiol, 64(11), 1045-1050. doi:10.1016/j.recesp.2011.07.009
14. Fujitani, S., & Baldisseri, M. R. (2005). Hemodynamic assessment in a pregnant and peripartum patient. Crit Care Med, 33(10 Suppl), S354-361.