US - Chest Pain in the Young: Ultrasound of the Month

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THE CASE PRESENTATION…

The patient is a young male with a past medical history of polysubstance use disorder who presents to the emergency department (ED) in the custody of police complaining of chest pain. He states that the pain began on the day of presentation when he was involved in an argument with an acquaintance, which led to a physical altercation and his subsequent arrest. While in police custody his chest pain progressed. It is described as central, pressure-like, non-radiating, and without associated nausea, vomiting, or diaphoresis. Of note, on further questioning he has had similar chest pain fairly frequently over the past year. It is usually precipitated by exertion, and has preceded several episodes of syncope. He has not noticed any infectious symptoms including cough or fever. He has had no peripheral edema nor orthopnea. Additionally, the patient has a family history of young need for “heart surgery” for unknown reasons as well as early idiopathic death.

The vital signs are as follows: heart rate 110, blood pressure 140/90, oxygen saturation 100%, respiratory rate 18. The patient appears generally anxious but is in no acute distress. He is tachycardic, with a regular rhythm. A III/VI systolic murmur is present without appreciable radiation, most prominently at the left upper sternal border - there is no rub or gallop. There is no visible jugular venous distension. The remainder of his exam is unremarkable.

A 12 lead electrocardiogram is obtained, which shows sinus tachycardia with a normal axis and large voltage QRS complexes across the precordial leads. There are deep, thin Q waves in V1 and V2, with diffuse T wave inversions, favoring the lateral and inferior leads. There is no prior for comparison.

Due to the concerning clinical history and abnormal ECG a transthoracic echo is obtained in the emergency department...

And now for the ultrasound images…

Watch HCM PSL GIF on Gfycat. Discover more related GIFs on Gfycat

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What do you see on ultrasound?

The interventricular septum is severely hypertrophied - great than 25mm in multiple sections on the still images. Although there are only two views provided, the left ventricular (LV) ejection fraction is probably normal. There is no pericardial effusion. In the context of his clinical and family history this is concerning for hypertrophic cardiomyopathy (HCM).

Ultrasound pearls

Clinical information

HCM is an inherited disorder resulting from a mutation in any one of a number of sarcomeric proteins expressed in cardiac myocytes. Traditionally it has been thought of as a relatively rare diagnosis (although frequent by genetic standards) affecting approximately 1 in 500 adults1. The inheritance pattern is most often autosomal dominant, producing a strong family history. Recently HCM has been proposed to be more common with a prevalence of up to 1 in 200 when accounting for less frequently observed pathogenic variants2. Mortality attributed to HCM varies depending on the source. Affected patients, when treated at referral centers, may reach their full life expectancy without issue. That said, patients diagnosed at younger ages are at higher risk for sudden cardiac death, which occurs at rate of 2% annually in children and adolescents, compared to 0.5-1.5% in adults10.

Echocardiographically, the diagnosis is made by the presence of unexplained LV hypertrophy >15 mm2. The inclusion of the term “unexplained” precludes the presence of risk factors for reactive hypertrophy, whether that be long-standing hypertension, valvular disorders, athlete’s heart, or congenital heart disease.

Although there are a number of structural cardiac abnormalities in HCM, LV outflow tract (LVOT) obstruction is one of the more concerning. This phenomenon is well-described, most often resulting from systolic anterior motion (SAM) of the mitral valve and subsequent sealing of the LVOT. There is some disagreement regarding the underlying forces leading to SAM. Some authors credit the Venturi effect - a reduced outflow diameter leads to a rise in flow velocity and concomitant drop in pressure, drawing the valve anteriorly towards the septum4. Others suggest mechanical forces due to a hyperdynamic ventricle are responsible. Higher outflow velocity and gradients are associated with sudden cardiac death and disease progression5. It should be noted that although obstruction most commonly occurs at the outflow, mid-cavitary obstruction has also been described3.

Ultrasound Evaluation in the ED

Ultimately patients with findings concerning for HCM will need full assessment with consultative echocardiography and perhaps more advanced imaging. In the ED, there are several variables that can be used to inform not only the diagnosis, but the urgency of follow up (if patients are otherwise appropriate for discharge). In addition to global function, physicians should attempt to quantify LV wall thickness.

As previously stated, the threshold for echocardiographic diagnosis of HCM is a wall thickness of 15mm. There are some authors who recommend a threshold of 13mm in patients with a strong family history6. This hypertrophy can be diffuse or isolated to a specific segment of myocardium. LV wall thickness is best quantified from the parasternal short axis view, and should be assessed during diastole. Confirmation of myocardial hypertrophy requires multiple views. Some sources suggest using the ratio of septum to posterior LV wall of greater than 1.3 as a diagnostic criteria as well7.

Advanced Assessments

SAM (Systolic Anterior Motion)

SAM is best appreciated in the parasternal long axis view. Placing the M-mode cursor directly over the anterior leaflet of the mitral valve should demonstrate intersection of the leaflet with the surface of the interventricular septum. Quantitative severity of SAM is determined by the duration of contact between the valve and septum: mild SAM occurs for less than 10% of systole, while greater than 30% is indicative of severe disease7. Use of ECG leads may be helpful in quantifying duration of SAM as a proportion of systole. Qualitatively, SAM will produce turbulent flow in the LVOT, leading to a “mosaic pattern” on color doppler8. It should be noted that although SAM was at one time considered pathognomonic of HCM, up to 40-70% of affected patients will not have this finding on TTE7.

LVOT Gradient

Assessment of the LVOT gradient using continuous wave doppler is helpful in risk stratifying patients with HCM (see Table 1). Gradient assessment is accomplished in the apical 5 or 3 chamber view, focusing on the LVOT. A maximum gradient of >30mmHg at rest is concerning for obstruction. Absence of a resting gradient does not exclude HCM with other concerning findings on history and echo. Valsalva is a simple bedside maneuver that can be utilized to assess for provocable obstruction in the ED, where pharmacological agents may not be easily accessible. Ensuring that the doppler beam is parallel to the flow of blood is essential in obtaining an accurate estimate of the gradient. Exclusion of a mitral regurgitation jet, if present, is also key, as this may falsely increase estimates of LVOT gradient9. Of note, mitral regurgitation is common in HCM due to SAM producing poor coaptation of the mitral leaflets. The regurgitant jet resulting from SAM will usually be directed posteriorly, while anterior or centrally-directed jets often result from intrinsic valvular pathology10. Lastly, there are other pathologies that may lead to a resting LVOT gradient which will need to be ruled out, including subaortic membrane or subvalvular aortic stenosis. Thus consultation with a cardiologist is essential in determining appropriate follow up and further diagnostic evaluation for these patients.

Case resolution

After the bedside echo was performed, the images were reviewed with the in-house cardiology fellow. The patient was informed of the likely diagnosis and an urgent referral was placed to cardiology for further evaluation. The patient was prescribed a low dose beta blocker on discharge. He was given education regarding the importance of maintaining appropriate hydration, abstaining from vigorous exercise and drug use, especially stimulants, given his relatively high risk for sudden cardiac death.

Take home points

  • HCM may not be as rare as we once thought -- consider echocardiography in the ED if a patient has concerning historical or ECG features
  • LV wall thickness >15mm in any segment should raise concern for HCM in the appropriate clinical setting
  • Advanced assessmentes, including quantification of SAM and LVOT obstruction, can help risk stratify patients and inform the urgency of follow up and potential therapeutic options at the point of care

Table 1. Risk factors for sudden cardiac death in HCM (adapted from Williams et al. & Nishimura & Holmes)

AUTHORED BY: CHRIS SHAW, MD

Dr. Shaw is a PGY-2 at the University of Cincinnati Emergency Medicine Residency pursuing a career in Critical Care Medicine

PEER REVIEWED BY: PATRICK MINGES, MD

Dr. Minges is an Assistant Professor at the University of Cincinnati and fellowship trained in Ultrasound

References

  1. Maron, B. J., Gardin, J. M., Flack, J. M., Gidding, S. S., Kurosaki, T. T., & Bild, D. E. (1995). Prevalence of hypertrophic cardiomyopathy in a general population of young adults: echocardiographic analysis of 4111 subjects in the CARDIA study. Circulation, 92(4), 785-789.

  2. Semsarian, C., Ingles, J., Maron, M. S., & Maron, B. J. (2015). New perspectives on the prevalence of hypertrophic cardiomyopathy. Journal of the American College of Cardiology, 65(12), 1249-1254.

  3. Maron, B. J., McKenna, W. J., Danielson, G. K., Kappenberger, L. J., Kuhn, H. J., Seidman, C. E., ... & Wigle, E. D. (2003). American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy: a report of the American College of Cardiology foundation task force on clinical expert consensus documents and the European Society of Cardiology committee for practice guidelines. Journal of the American College of Cardiology, 42(9), 1687-1713.

  4. Walker, C. M., Reddy, G. P., Mohammed, T. L. H., & Chung, J. H. (2012). Systolic anterior motion of the mitral valve. Journal of thoracic imaging, 27(4), W87.

  5. Maron, B. J., McKenna, W. J., Danielson, G. K., Kappenberger, L. J., Kuhn, H. J., Seidman, C. E., ... & Wigle, E. D. (2003). American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy: a report of the American College of Cardiology foundation task force on clinical expert consensus documents and the European Society of Cardiology committee for practice guidelines. Journal of the American College of Cardiology, 42(9), 1687-1713.

  6. Maron, M.S. (2018). Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation. In B.C. Downey (Ed.), UpToDate. Retrieved March 14, 2019 from https://www.uptodate.com/contents/hypertrophic-cardiomyopathy-clinical-manifestations-diagnosis-and-evaluation.

  7. Williams, L. K., Frenneaux, M. P., & Steeds, R. P. (2009). Echocardiography in hypertrophic cardiomyopathy diagnosis, prognosis, and role in management. European Journal of Echocardiography, 10(8), iii9-iii14.

  8. Nagueh, S. F., Bierig, S. M., Budoff, M. J., Desai, M., Dilsizian, V., Eidem, B., ... & Woo, A. (2011). American Society of Echocardiography clinical recommendations for multimodality cardiovascular imaging of patients with hypertrophic cardiomyopathy: endorsed by the American Society of Nuclear Cardiology, Society for Cardiovascular Magnetic Resonance, and Society of Cardiovascular Computed Tomography. Journal of the American Society of Echocardiography, 24(5), 473-498.

  9. Losi, M. A., Nistri, S., Galderisi, M., Betocchi, S., Cecchi, F., Olivotto, I., ... & Mele, D. (2010). Echocardiography in patients with hypertrophic cardiomyopathy: usefulness of old and new techniques in the diagnosis and pathophysiological assessment. Cardiovascular ultrasound, 8(1), 7.

  10. Veselka, J., Anavekar, N. S., & Charron, P. (2017). Hypertrophic obstructive cardiomyopathy. The Lancet, 389(10075), 1253-1267.

  11. Nishimura, R. A., & Holmes Jr, D. R. (2004). Hypertrophic obstructive cardiomyopathy. New England Journal of Medicine, 350(13), 1320-1327.

  12. Gersh, B. J., Maron, B. J., Bonow, R. O., Dearani, J. A., Fifer, M. A., Link, M. S., ... & Seidman, C. E. (2011). 2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines developed in collaboration with the American Association for Thoracic Surgery, American Society of echocardiography, American Society of nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Journal of the American College of Cardiology, 58(25), e212-e260.