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Emergency Ultrasound

Cardiac Journal Summary

By Mark Favot, MD, FACEP and Scott Sparks, MD, FACEP

Case


You arrive for a midnight shift ready, when walk-in triage brings back a 28 year-old male patient in cardiac arrest. The police accompany the patient and inform you that he was out celebrating his birthday and while he and friends were driving from one bar to the next, he became short of breath, which quickly progressed to severe dyspnea. His friends drove him to the hospital, during which his dyspnea was unrelieved by an albuterol inhaler, then dropped him off unresponsive at the front door and left. You evaluate the patient in the resuscitation bay - he is unresponsive, pulseless, apneic, mildly obese. Cardiac monitor reveals a narrow complex, slow rhythm consistent with PEA. Nursing obtains an IV while you intubate the patient and begin ACLS measures. Review of the EMR reveals multiple ED visits for symptoms related to asthma, as well as one prior intubation and ICU admission for respiratory failure. Despite aggressive resuscitation measures, serial cardiac ultrasounds reveal no cardiac activity, and you pronounce the patient dead. What happened to this man? 

During medical examiner (ME) grand rounds, you assume that your young cardiac arrest patient was celebrating his birthday by using some illicit drugs and assume a sympathomimetic. The ME reveals that the man died from a cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy (ARVC), and that his lungs revealed no findings consistent with asthma. Unfortunately for this man, despite multiple medical evaluations, including an ICU admission, he had never undergone echocardiography, which may have detected findings suggesting this fatal diagnosis. How many patients have you seen during a shift who have felt palpitations, syncope, mild dyspnea with a normal pulse oximetry and normal lung auscultation, or patients that “nearly fell out?” Podcasts, textbooks, and blogs abound with scary causes for each: cardiac dysrhythmias and ischemia, pulmonary embolism, pulmonary hypertension, Wolf-Parkinson White syndrome, hypertrophic cardiomyopathy, and Romano-Ward and Brugada channelopathies. In a recent New England Journal of Medicine review, Dr. Corrado and colleagues discuss arrhythmogenic right ventricular cardiomyopathy (ARVC).1

How can echo help in the Emergency Department?

ARVC is estimated to have a prevalence of 1:5000 and as low as 1:2000 in certain European populations, (with only half of those affected with a positive family history), has an autosomal dominant transmission, and is due to mutations in the desmosomal proteins.2 There is variable penetrance and phenotypic expression, and the disease tends to be more malignant in men than women. It typically presents itself in the 20s to 40s and, like some of the earlier syncope causes, may first present as sudden cardiac death.

What do we look for?

ARVCLuckily, the most common presentation is as palpitations or effort induced syncope in a young adult with T wave inversions in the right precordial leads (V1 through V4) on the EKG (Figure 1 and 2), ventricular arrhythmias with a LBBB pattern, and right ventricular structural anomalies on imaging allowing us the means to identify it earlier in the emergency department. The arrhythmias range from infrequent PVC, to ventricular tachycardia degenerating to ventricular fibrillations, and is thought to be exacerbated by catecholamine surges. The echocardiographic findings are nonspecific but given the primary pathology (fibrofatty tissue replacing the myocardium in the RV) they typically consist of RV dilation and reduced systolic function with a normal LV size and systolic function and normal pulmonary artery pressures. Prominent trabeculations of the RV free wall, increased echogenicity of the moderator band (when present) and occasionally small RV aneurysms can be seen.3 The preferred imaging modality is cardiac MRI (cMRI) due to combined, non-invasive structural and functional evaluation.

Figure 1: Electrocardiographic and imaging features of ARVC. The 12-lead standard electrocardiogram in Panel A shows a repolarization abnormality that is characteristic of ARVC, with negative T waves in leads V1 through V4 and depolarization changes, including low QRS voltages (<0.5 mV) in the limb leads and prolongation of the right precordial QRS complex, with a delayed S-wave upstroke. The terminal activation duration (TAD), which is the interval between the nadir of the S wave and the end of all depolarization deflections, is prolonged, at 80 msec, in lead V1 (inset); the normal value is less than 55 msec. Panel B shows an example of “epsilon waves” (i.e., small-amplitude distinct potentials between the end of the QRS complex and the beginning of the T wave) in leads V1 and V2. This is a highly specific electrocardiographic abnormality that is seen in a minority of patients with advanced disease. The 12-lead standard electrocardiogram in Panel C shows ventricular tachycardia (160 beats per minute) with a left bundle-branch block pattern. The two-dimensional echocardiogram, parasternal long-axis view (PLAX), in Panel D shows dilatation of the right ventricular outflow tract (RVOT), at 38 mm (normal value, <32 mm). The cardiac MRI scan (systolic frame of right ventricular two-chamber long-axis view on cine sequences) in Panel E shows an aneurysm of the RVOT (solid arrows) and multiple sacculations of the inferior and apical regions (open arrows). RA denotes right atrium, and RV right ventricle.

prognostic stratification
Figure 2: Proposed scheme for prognostic stratification of patients with ARVC according to the clinical presentation. The risk subgroups shown in the figure have been defined on the basis of the estimated probability of a major arrhythmic event (ie, sudden cardiac death, cardiac arrest due to ventricular fibrillation, sustained ventricular tachycardia, or an event requiring defibrillator intervention) during follow-up, in relation to previous arrhythmic events or risk factors. An estimated annual risk of more than 10% defines the high-risk group, a risk between 1% and 10% the intermediate-risk group, and a risk below 1% the low-risk group. PVB denotes premature ventricular beats.

How do we definitively diagnosis it?

Typically, “we” (emergency physicians) don’t. An international task force first proposed guidelines in 1994 and updated them in 2010 (Table 1). However, the variable nature of the disease makes the guideline sensitivity low. Major risk factors include unexplained syncope, non-sustained ventricular tachycardia on ambulatory monitoring or exercise testing, and severe systolic dysfunction of either ventricular. The most important predictors of life-threatening arrhythmic events during following include prior cardiac arrest due to ventricular fibrillation and sustained ventricular tachycardia (Figure 2).  

 

Category Major Criteria Minor Criteria
Echocardiography 1. Regional RV Akinesia, Dyskinesia, or Aneurysm PLUS
2. PLAX RVOT ≥ 32mm, PSAX RVOT ≥ 36 mm, or FAC ≤33%
1. Regional RV Akinesia, Dyskinesia, or Aneurysm PLUS
2. PLAX RVOT 29 to <32 mm, PSAX RVOT 32 to <35 mm, or FAC 34 to 40%
EKG Inverted T waves in Right Precordial Leads (V1-V3) in patients older than 14 yo* 1. Inverted T waves in leads V1 and V2, OR in V4, V5, or V6 in patients older than 14 yo*.
2. Inverted T waves in leads V1 through V4 in patients older than 14 yo++.

Table 1: International task force definition of arrhythmogenic right ventricular cardiomyopathy. * In the ABSENCE of complete RBBB. ++ In the PRESENCE of complete RBBB. PLAX: Parasternal Long Axis. RVOT: Right Ventricular Outflow Tract. PSAX: Parasternal Short Axis. FAC: Fractional Area Change.

What to do in the ED? 

The goal is to identify findings on H&P, ECG, limited echo or other imaging modalities that can clue us to the diagnosis, urgent cardiology follow-up, with the ultimate goal being to reduce the risk of sudden cardiac death. Placement of an implantable cardiac defibrillator (ICD) would then be considered once the diagnosis is confirmed by cMRI. Amiodarone alone, or in conjunction with beta-blockers, is the most effective medical therapy, although current therapeutic options are palliative and help prevent the risk of sudden cardiac death. We already use POCUS transthoracic echocardiography to evaluate for the life-threatening anomalies and now add ARVC to the list of saves we can make.

References

  1. Corrado D, Link MS, Calkins H. Arrhythmogenic right ventricular cardiomyopathy. N Engl J Med. 2017 Jan 5;376(1):61-72. doi: 10.1056/NEJMra1509267.
  2. Corrado D, Thiene G. Arrhythmogenic right ventricular cardiomyopathy/dysplasia: clinical impact of molecular genetic studies. Circulation. 2006 Apr 4;113(13):1634-1637.
  3. Yoerger DM, Marcus F, Sherrill D, et al. Echocardiographic findings in patients meeting task force criteria for arrhythmogenic right ventricular dysplasia: new insights from the multidisciplinary study of right ventricular dysplasia. J Am Coll Cardiol. 2005 Mar 15;45(6):860-865.

 

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