POCUS-FOCUS #1: Recognizing Hypertrophic Cardiomyopathy

Welcome to the first of what I hope will be a continuing series of concise monthly videos or e- learning material FOCUSed on POCUS (Point-Of-Care-UltraSound). The intention of the series is to draw attention to supplemental or more advanced uses for POCUS, interesting cases, important EM Ultrasound literature, online resouces (FOAM), and other fun EM Ultrasound tidbits.

The first POCUS-FOCUS topic will be:
Differentiating Hypertrophic Cardiomyopathy (HCM) from both hypertensive heart disease (HHD) AND Athletic heart.

I will keep this simple and focused on scanning techniques that most EM-trained docs should be able to perform, while avoiding much the more difficult and advanced methods.
HCM: A genetic protein mutation leading to inappropriate LV muscular thickness (anywhere) but more often septal leading to obstruction of the LVOT (left ventricular outflow tract) and often malignant dysrhythmia.

Our job in the ED: Risk stratifying and screening appropriate patients with concerning clinical and/or family history for HCM. Our job is NOT TO DIAGNOSE HCM. We should simply search for evidence that this may be the underlying etiology of the presenting complaint which could alter our disposition or management.

What you should do?: Perform focused cardiac ultrasound (FoCUS). Most importantly the Parasternal Long Axis and the Parasternal Short Axis ; if desired use M-mode which will ensure more accurate phase (end-diastole). Measure the LV thickness at end diastole at various different locations.

PSSA: Measure Base, Mid, and Apical LV Thickness _________________________________________________________________

                      

PSLA (with M-mode): Measure LV thickness @ the trough (end diastole) -Septal wall AND posterior wall (yellow) measurements (then calculate ratio)

What measurements should worry you?: 

Guidelines differ however it appears widely accepted that LV thickness in ANY myocardial segment >15mm is concerning for HCM. Also, septal to posterior (s/p) wall thickness ratio > 1.3 (in normotensive) and > 1.5 (in hypertensive patients) is considered highly suspicious for HCM
Hypertensive hearts MAY also have larger septal thickness compared to posterior. They are not always concentrically hypertrophic as is classically taught. Athlete hearts are often much less thick than both HHD and HCM.
Here are some tables with important measurements, these are the some of the values from which the guidelines have been derived:

Bonus (more advanced US technique/interpretation): There are no pathognomonic findings on echo for HCM, given that hypertension can give profound LV thickness, even asymmetric septal thickness. However, there is a finding called SAM (systolic anterior motion) which is anterior motion of the anterior leaflet of the mitral valve toward the septum just after systole begins (which is why HCM becomes obstructive – particularly in hypovolemia/Valsalva/etc). See the table above which reveals that no normal or hypertensive patients demonstrated SAM and 36/47 HCM patients did. This finding is very specific, but not so sensitive, for HCM.
You can see this as an EM doc at the bedside ... I PROMISE. Just watch the LVOT (left ventricular outflow tract) –particularly the anterior mitral leaflet- in these parasternal long axis (PSLA) clips of NORMAL patients and HCM patients.

References:
Sheikh N. The electrocardiographic phenotype in athletes with hypertrophic cardiomyopathy: implications for pre-participation cardiovascular evaluation using electrocardiography. Heart. 2014 Jun;100 Suppl 3:A51
Bart et al. Measurement of Left Ventricular Wall Thickness and Mass by Echocardiography. Circulation. 1972;45:602-611
Williams, et al. Echocardiography in hypertrophic cardiomyopathy diagnosis, prognosis, and role in management. Eur J Echocardiogr (2009) 10 (8):iii9-iii14. (http://ehjcimaging.oxfordjournals.org/content/10/8/iii9.full)
Doi, et al. Echocardiographic differentiation of hypertensive heart disease and hypertrophic cardiomyopathy. Br Heart J 1980;44:395-400 doi: 10.1136/hrt.44.4.395
Lang, R. M., et al. (2005). "Recommendations for chamber quantification: a report from the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology." J Am Soc Echocardiogr 18(12): 1440-1463.