Point-of-care ultrasound, or POCUS, has become fully incorporated into almost every aspect of clinical care over the past 5 years. COVID-19 has further solidified the use of POCUS for the evaluation of dyspnea and cough given its portability. But what about the use of POCUS for a woman during pregnancy?
Ultrasound has been consistently employed to evaluate the fetus in all 3 trimesters. There is another patient, though; the mother! Rising maternal morbidity and mortality secondary to cardiovascular disease requires the obstetrical care provider to employ point-of-care clinical assessment that targets the maternal cardiovascular system. This is the problem and the solution may be “getting a CLUE” by implementing cardiac limited ultrasound evaluation (CLUE) at the bedside as suggested by Kimura et al.
In contrast to fetal imaging, which utilizes higher frequency transabdominal and transvaginal ultrasound probes, penetration of the chest wall requires a lower frequency probe (2–4 mHz). Ideally, a low frequency probe that is compatible with most commonly used obstetrical equipment would facilitate ease of utilization. The CLUE protocol employs the following views: parasternal long axis view, lung anteroapex view, lung posterolateral base view, subcostal view, and right sub-xyphoid view. These views allow the clinician to evaluate the patient for pathophysiologic findings including the presence of pleural or pericardial effusion; abnormal contractility, chamber enlargement, and valvular dysfunction. Assessment of the size and collapsibility of the inferior vena cava can be a noninvasive marker of right-sided filling pressures to evaluate volume status in an oliguric patient with preeclampsia.
I propose that CLUE be extrapolated from the non-pregnant patient population for applicability in the pregnant patient population. This may be particularly relevant in certain scenarios including: triage of pregnant women with cardiac symptoms in an outpatient or in-patient setting as an adjunct to the physical exam; and labor and delivery units with lack, or limited immediate availability, of formal echocardiography. While anecdotal case experience suggest utility, formal studies designed to compare CLUE in pregnancy to the gold standard of transthoracic echocardiography will confirm the feasibility of CLUE in this unique population. Even though obstetricians are trained to perform obstetrical and gynecologic ultrasound, and are well versed with the existing ultrasound equipment on their units, additional training may be required. In addition to obstetrical care providers, other clinicians, such as emergency room and internal medicine providers, may also perform CLUE to assess the maternal cardiopulmonary system.
Limitations of point-of-care cardiac examination of the heart include both patient characteristics and technique. Large body mass size and enlarged breast tissue common in pregnancy can lead to imaging acquisition challenges. Off-axis imaging technique can lead to false positive or false negative diagnoses. Patient positioning should be optimized and shifted to left lateral tilt to accommodate aortocaval compression.
CLUE demonstrates potential as an innovative diagnostic point-of-care technique that can be adapted to maternal use. Timely future clinical studies that compare CLUE with formal echocardiography during pregnancy will further clarify its feasibility and full utility in the clinical arena as a tool to combat rising maternal morbidity in the new millennium.
- Kimura BJ, Shaw DJ, Amundson SA, Phan JN, Blanchard DG, DeMaria AN. Cardiac Limited Ultrasound Examination Techniques to Augment the Bedside Cardiac Physical Examination. J Ultrasound Med. 2015;34:1683–1690.
Carolyn M. Zelop, MD, is a Director of Perinatal Ultrasound and Research at The Valley Hospital, Ridgewood, New Jersey; a Clinical Professor of Ob/ Gyn at NYU School of Medicine; and she is a senior member of the AIUM and the ACOG rep to women’s imaging for ACR.
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