Background
Yesterday, my fellow informed me about a frantic call for cardiac fitness for an emergency cesarian section in 24-year-old woman with hypertrophic cardiomyopathy, who is asymptomatic and has a 20mmhg gradient across LVOT.
“Was she in labor”?
“No, she is 36 weeks term.
“Why LSCS? Why emergency”?
“I don’t know sir. Let me discuss and come again”.
HCM in pregnancy: An approach
Hypertrophic cardiomyopathy is a specific genetic disorder of myocyte (myosin and others) within the sarcomere. Though uncommon in pregnancy it raises considerable anxiety to the patient, family, and the obstetrician.
Hemodynamics
Though we tend to worry more about dynamic LVOT obstruction, it is actually the restrictive physiology of LV myocardium that might cause more concern. Three key variables operate in this entity namely preload, afterload, and contractility that determine the cardiac hemodynamics and possibly the symptoms. We know the classical consequence of pregnancy is a fall in systemic vascular resistance( SVR) ie afterload.
In pregnancy, there is a complex interaction between these three parameters along with heart rate. Fortunately, the net effect ends up favorable for LV performance. This is made possible because a major compensation occurs by a 50% increase in blood volume that effectively counters the deleterious effect of fall in SVR on LVOT gradient. (If mitral regurgitation is significant, the fall in SVR actually may help reduce regurgitant fraction especially if its intrinsic defect )
Maternal outcome
Is good (if not excellent). Maternal mortality reported in the literature, is gradually coming down (0 to .5% in various series) However, about 15 % of HCM patients with gross LVH or obstruction, may develop pulmonary congestion in the third trimester. In some patients, VPDs, nonsustained VT, even AF can lead to some tense cardiac consultations but are usually innocuous. I am not sure about the sudden death in pregnancy. I guess it should be negligible, unlike the non-pregnant HCM.
A mystery learning point
It is surprising both fetal and maternal outcome is little related to the severity of LVOT gradient (Ref 2)
Indication for cesarian
- Most mothers can deliver per vaginalis without much hemodynamic challenge.
- Vey rarely cardiac indication for LSCS need to happen. (However, in the real world many land up in LSCS , since true indication can be blurred due to cardio-obstetrical anxiety)
- Spinal anesthesia to be avoided as hypotension is poorly tolerated
- Beta-blockers to be continued during pregnancy labor.(Need not start however if already not taking)
Fetal outcome
Premature birth, stillbirths, low weight are little more common than normal pregnancies. Fetal bradycardia due to beta-blockers has been noted but not troublesome.
What is the role of cardiologist?
The precise answer is “minuscule role”. I can vouch for this from a personal level. ( Consults are meant only for bringing some comfort to the obstetrical team). Active cardiac interventions are rarely required or rather desired. (Of course, patients who have significant symptoms, operated for HC, on OAC for AF, the rare ones with ICD needs expert care)
Final message
- Women with HCM can safely become pregnant and deliver.
- Best outcome is likely for both mother, and baby if basic precautions are taken.
- LSCS is rarely required*.
- Counseling about the condition needs to be gentle and just adequate. Dwelling deep into the pathology, hemodynamics, and statistics in totally asymptotic patients invites trouble to all stakeholders.
*It is worthwhile to note other forms of severe LVOT obstruction like valvular, supra valvular stenosis, and Aortic pathologies like Marfan, coarctation aorta are serious entities that deserve prompt cesarian sections.
Reference
2.
https://academic.oup.com/eurheartj/article/38/35/2683/3811991
Dr.S.Venkatesan MD 