Cardiology

Ultrasound Case of the Month

Case of the month from October, 2016

Case:

A 36 year old female with no significant past medical history comes in with sudden onset chest pain. Bedside ultrasound for this patient is below:

This patient had a saddle pulmonary embolism, with right heart strain as evidenced by D sign and McConnell's sign, with a positive troponin!

Image 1:

This is an apical 4-chamber (A4C) view, which is obtained by imaging underneath and lateral to the nipple (in the breast crease for women) and pointing your ultrasound beam like a spear to the patient’s right scapula. You may need to roll the patient onto their left side to bring the heart closer to the chest wall and optimize the image. 

In the A4C you are able to evaluate for equality which is to compare the left and right ventricle.  The RV: LV ratio should be about 0.6:1.  If you don’t want to remember that ratio, no worries! Instead you can just remember that the RV should be equal or slightly smaller in size when compared to the LV and that the apex of the LV is usually higher on the screen than the apex of the RV (left apex dominant).  In this image we see evidence of what we call McConnell’s sign which is when there is RV strain and akinesis of the RV.  However, we often see apical sparing in this scenario.  So the RV apex is still moving, but the lateral wall is hypokinetic or akinetic, from RV strain.

Image 2:

This is a parasternal short view (PSS), which is acquired with the probe placed on the chest wall along the short axis of the heart (marker to the right hip). The LV should look round, like a donut, and the RV has a crescent shape. This image is an example of a “D-sign” which represents septal flattening.  The pressure in the RV is so high that it is exerting pressure on the interventricular septum and causing it to flatten. As a result the LV looks more like a “D” than an “O”.

For more information on right heart strain: 5 Minute Sono

Resident Reviewer: Dr. Chana Rich
Faculty Reviewer: Dr. Kristin Dwyer

52 Articles: Chest Pain, Crickey!

This is part of a recurring series examining landmark articles in Emergency Medicine, in the style of ALiEM’s 52 Articles.

Discussing:

Than, M. Cullen, L. Aldous, S. et al “2-Hour Accelerated Diagnostic Protocol to Assess Patients With Chest Pain Symptoms Using Contemporary Troponins as the Only Biomarker: The ADAPT Trial.” Journal of the American College of Cardiology, 2012; 59(23):2091-98.

Main Points:

1. This 2012 prospective observational study of 1,975 patients evaluated an accelerated diagnostic protocol (ADP) to determine who may be suitable for rapid discharge. The authors determined that 20 percent of the patients evaluated could be classified as low risk for major adverse cardiac event (MACE) within 60 days. The sensitivity and negative predicative value of the ADP were both 99.7 percent.

2. This study followed the ASPECT trial and helped prove that cardiac troponin alone was a suitable biomarker for use within an ADP that also incorporated elements of the ECG and TIMI score risk assessment. The use of cardiac troponin doubled the proportion of patients classified as low risk in comparison to the ASPECT study, 20 v 9.8 percent.

Background:

In the United States more than 8 million patients present to emergency departments with the complaint of acute chest pain. Fewer than 10 percent of these individuals will be diagnosed with acute coronary syndrome (ACS); however, more than 25 percent will be admitted for further evaluation. Clearly, significant health care resources are utilized evaluating this concern and therefore many have studied these patients in hopes of identifying a cohort that is low risk and may be safely discharged home. There is no clear consensus for what represents an acceptable miss-rate of ACS, but many physicians who have been surveyed on the matter feel a value of less than one percent is the goal.

Continued research efforts are evaluating the use of even higher sensitivity cardiac biomarkers, but in the interim, clinicians continue to rely on clinical prediction tools that incorporate elements of the patients risk profile, current troponin assays as the primary cardiac biomarker and ECG. The HEART score has gained significant popularity and was recently adopted within our hospital system, Lifespan, Rhode Island. Using a cutoff of HEART≤3 the likelihood ratio (LR) is 0.20 and with a HEART≥7 the LR is 13 according to the JAMA review of the four large studies published to date that enrolled 13,000 patients. The use of clinical decision tools relies on establishing local knowledge so that accurate pre-test probabilities can be incorporated into the risk stratification of patients.

Details:

This trial was a prospective observational study that enrolled 1,975 participants in two urban emergency departments in Brisbane, Australia and Christchurch, New Zealand. This was a pre-planned addition to the ASPECT study, however, only 2 of the 14 study sites participated and the additional work consisted of adding a 2 hour blood sample for cardiac troponin from the time of presentation. This ADP demonstrated that 20 percent of patients could be deemed low risk with only a 0.25 percent risk of short term MACE. The authors argue that the use of this ADP could yield a significant reduction in the use of health care services.

The patients were adults who presented with at least five minutes of symptoms consistent with ACS according to the American Heart Association case definitions. Patients were excluded if they had ST-segment elevation on their ECG or a clear alternative diagnosis for their chest pain such as varicella zoster. Further exclusions included: those who could not be consented, transferred patients, pregnant patients, or those who could not be contacted after discharge. This last exclusion criterion is vague and one that likely limits further generalizability of the study.

Patients were managed based on local hospital protocols and cardiac troponin was drawn at presentation, and at the 6 and 12 hour mark. Patients received follow up at 30, 45, and 365 days from presentation using telephone encounters, hospital notes and national health databases for identifiable deaths. The ADP defined patients as low risk if they were negative for all parameters of the ADP.

ADAPT ADP:

1. Cardiac troponin level at 0 and 2 hours below institutional cutoff

2. No new ischemic changes on the initial ECG

3. TIMI score of zero

392 patients were identified as low risk of MACE within 30 days. One patient within this group, however, had a MACE and underwent angiography and stenting for right coronary and circumflex artery stenosis. The sensitivity and negative predictive value of the ADP was therefore 99.7 percent. The authors also performed secondary analyses to evaluate if the use of TIMI score of ≤1 may be utilized for categorizing patients as low risk but the sensitivity and negative predictive values suffered as a result, 97 and 98.8 respectively. The authors also attempted to tease out if individual parameters within the ADP were as effective at risk stratifying patients, but their conclusions clearly support the need for a combination of tools.

One of the limitations of incorporating an ADP such as this includes the need for a good outpatient system to be in place for appropriate and timely follow up. The patients included in this study also represent the more homogenous populations of Australia and New Zealand and were predominantly Caucasians.

Level of Evidence:

Utilizing the ACEP grading scheme dependent this study was graded a level II.

Surprises:

When utilizing clinical decision tools, especially with regards to ACS, one must remember that each item within the tool is an independent variable. As clinicians we are often biased by the initial ECG or lab studies prior to seeing a patient and collecting the history, so must remember to avoid premature closure.

Faculty Review: Dr. Siket

Relevant articles:

Farnaroff, A. Rymer, J. Goldstein, S. et al “Does This Patient With Chest Pain Have Acute Coronary Syndrome? The Rational Clinical Examination Systematic Review.” JAMA. 2015; 314(18): 1955-65.

Source Article:

Than, M. Cullen, L. Aldous, S. et al “2-Hour Accelerated Diagnostic Protocol to Assess Patients With Chest Pain Symptoms Using Contemporary Troponins as the Only Biomarker: The ADAPT Trial.” Journal of the American College of Cardiology, 2012; 59(23):2091-98.