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Crochetage Sign
Congenital heart disease remains the most common form of congenital abnormality. Despite its prevalence and screening prior to birth, it may continue, undiagnosed, into adulthood.1 One type of this congenital abnormality is an atrial septal defect (ASD). As EMS providers we may encounter patients who are unaware of having this condition. However, a distinct but often-unrecognized pattern on the ECG known as Crochetage sign, coupled with a thorough history and assessment, can indicate the presence of an ASD. Recognizing this abnormality can improve our patient management and expedite care.
Physiologically the atria serve three distinct purposes for cardiovascular function: containment, channeling, and contracting of blood within the myocardium. Atrial septal defects disrupt the normal blood flow in the heart, resulting in the myocardium being overworked to maintain homeostasis. Atrial septal defects left untreated can potentially lead to heart failure.
Normal Conditions vs. ASD
To understand why atrial septal defects can be problematic, we must first understand how the atria function under normal working conditions.
The heart has two atrial chambers, right and left. The right atrium obtains deoxygenated blood from the superior vena cava along with the coronary sinus. The left atrium gets oxygenated blood from the pulmonary veins. Each atrium equally distributes the blood into the ventricles during the systolic phase of the cardiac cycle.
Under normal physiologic conditions the right atrial pressure is markedly lower than the left. The difference allows for the passage of blood from the left atrium to the right, resulting in a left-to-right shunt. Generally patients with an atrial septal defect will have this left-to-right shunt.1
When an atrial septal defect is present, there is a hole in the septum that divides the right and left atria, the size of which corresponds to the severity of the shunt.2 This allows oxygen-rich blood to flow retrograde from the left atrium to the right, mixing with deoxygenated blood and increasing the total amount of blood flowing toward the lungs. Large atrial septal defects can thus produce volume overload in the lungs, taxing the heart—this is one reason why pulmonary hypertension can manifest in these patients. Small defects seldom create a concern. Some smaller defects close during the first year of life, others during early childhood.3
Crochetage Pattern
A Crochetage pattern occurs in the R-wave of the inferior limb leads. The diagnostic presentation will reveal the R-wave prime pattern, which is a second positive deflection of the QRS complex. The R-wave is the first positive deflection preceding the P-wave. Additional positive deflections of the QRS complex extending beyond the baseline and taller than the initial R-wave are defined as an R-wave prime or RSR prime pattern.
Incomplete right bundle branch blocks have been known as correlating markers for atrial septal defects for more than 60 years, but a Crochetage sign has some variability and does not depend completely on the presence of an incomplete right bundle branch block for diagnosis.4,5 The presence of the RSR pattern in even one lead can provide beneficial information for diagnosis of an ASD. True positive outcomes of this sign are extraordinarily increased when correlated with an incomplete right bundle branch in all three inferior limb leads.2
The electrical axis expeditiously conveys electrical transmissions that occur consecutively as the ventricles depolarize. When the ventricles are activated, impulse conduction initially occurs on either side of the septum, down the right and left bundle branches. Therefore, septal depolarization naturally occurs from left to right. Depolarization occurs when the membrane potential is reduced to a less-negative value.
Shapes of a QRS complex may appear different in each limb lead because each lead has a different vantage point to the specific order of depolarization. Since the normal QRS complex identifies synchronous depolarization of the ventricles, this is where abnormalities will be identified. When the Crochetage sign is accompanied by an incomplete right bundle branch block and noted in leads, II, III, and aVF, the specificity is near 90%.4 The name Crochetage sign came from the appearance of the distinct notch at the top of the R-wave that looks like the workings of a crochet needle.6
Some additional ECG findings that accompany the incomplete right bundle branch block are a posterior hemifascicular block and a right atrial enlargement.6 The presence of an RSR in lead V1 increases the specificity to approximately 80% likelihood of the presence of an ASD. Inversion of the P-waves can occur, suggesting sinoatrial node deficiency. T-wave inversion in leads V3R, V4R, and V5R also increases the specificity of diagnosis of atrial septal defect.6 After surgical repair around 35% of patients will lose the Crochetage sign on their ECG; however, the right bundle branch block pattern may still be present.4
Volume Overload and Effects
In patients with atrial septal defects, ECG abnormalities correlate with shunt severity and are independent of the right bundle branch pattern. The distinct presentation of the Crochetage sign shows a delay in the depolarization of the right ventricle. When a right bundle branch block is noted, this means the right ventricle depolarized last. The incomplete right bundle branch block is attributed to prolonged depolarization of the hypertrophied outflow tract of the right ventricle, potentially exacerbated by volume overload in the right ventricle.6
Volume overload resulting in elevated blood flow to the pulmonary circulation will result in structural changes within the pulmonary vasculature. Pulmonary vascular remodeling will result in an increased size of the smooth muscle layers within the vascular walls. This will inevitably result in restricted blood flow to the pulmonary circuit, resulting in pulmonary hypertension.7
Detection of congenital heart disease is complicated by signs and symptoms that are often multifactorial and nonspecific. As providers we often see it manifest as respiratory complaints (e.g., dyspnea on exertion). Patients present with dyspnea or fatigue with exercise or exertion, cardiac arrhythmias, palpitations, and ventricular dysfunction.
Atrial septal defects often produce heart murmurs in pediatric patients, which are frequently the only sign of their presence. The normal cardiac cycle has two distinct heart sounds, S1 and S2. S1 occurs when ventricular systole begins; S2 correlates to closing of the aortic and pulmonic valves and the beginning of ventricular diastole. Atrial septal defects will produce a distinct soft murmur heard during systole when the bell of the stethoscope is placed on left anterior chest wall at the second intercostal space. This is where the pulmonic valve is assessed. This observation can potentially reveal a widened fixed split of the S2 heart sound.7 Right ventricular volume overload is the primary indication for surgical intervention and closure of atrial septal defects. Closure of atrial septal defects in patients who are not symptomatic usually occurs around 5 years of age. Closure of atrial septal defects in adults is recommended when presentation is confirmed.8 It can be performed at a specialty center using a minimally invasive technique.
Diagnosis
According to the National Organization for Rare Disorders database on atrial septal defects, diagnosis usually occurs during infancy or between 6 months to 3 years. However, diagnosis after age 40 is very common once indicators appear.
A 12-lead ECG remains the standard for field assessment of cardiovascular complaints. However, the 12-lead is of little value without a detailed patient assessment, including a SAMPLE history. Obtaining thorough and complete histories can provide insight to a possible atrial septal defect. An example is when the patient describes progressive dyspnea, palpitations, and near-syncope over a period of weeks or months when performing light to moderate activities. Additionally, loss of energy or easy fatigue while performing normal daily activities should heighten awareness.
Identifying the Crochetage sign on the 12-lead ECG is important, especially when the patient is symptomatic due to the atrial septal defect. Treating a patient with an atrial septal defect will primarily depend on the patient’s age, whether symptoms of pulmonary congestion due to heart failure are present, and the severity of the shunt.8 Generally, children who have atrial septal defects will not have symptoms.
Very rarely the EMS provider may have to intervene pharmacologically if a patient presents with signs of heart failure resulting from moderate to severe mitral valve incompetence. In these situations it is recommended to treat with a medication that will reduce afterload, such as nitroglycerin, sodium nitroprusside, dobutamine, or isosorbide. Additionally, a diuretic, such as furosemide or bumetanide, may be required to assist with volume overload.8
Follow your local protocols, and should the patient require these pharmacological interventions, it is recommended to consult with medical control at the receiving facility.
References
1. Geva T, Martins JD, Wald RM. Atrial septal defects. Lancet, 2014 May 31; 383(9,932): 1,921–32.
2. Heller J, Hagège AA, Besse B, et al. “Crochetage” (notch) on R wave in inferior limb leads: a new independent electrocardiographic sign of atrial septal defect. J Amer Coll Cardiol, 1996 Mar 15; 27(4): 877–82.
3. Oster M, Bhatt AB, Zaragoza-Macias E, et al. Interventional therapy versus medical therapy for secundum atrial septal defect: a systematic review (part 2) for the 2018 AHA/ACC guideline for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation, 2019; 139(14): e814–e830.
4. Bhattacharyya PJ. (2016). ‘Crochetage’ sign on ECG in secundum ASD: clinical significance. BMJ Case Rep, 2016; 2016: bcr2016217817.
5. Ay H, Buonanno FS, Abraham SA, et al. An electrocardiographic criterion for diagnosis of patent foramen ovale associated with ischemic stroke. Stroke, 1998; 29(7): 1,393–7.
6. Raut MS, Verma A, Maheshwari A, Shivnani G. Think beyond right bundle branch block in atrial septal defect. Ann Cardiac Anaesth, 2017; 20(4): 475.
7. Naik RJ, Shah NC. Teenage heart murmurs. Pediatr Clinics, 2014; 61(1): 1–16.
8. Rao PS, Harris AD. (2017). Recent advances in managing septal defects: atrial septal defects. F1000Res, 2017 Nov 22; 6: 2,042.
Kory Lane, MEd, NRP, CCEMT-P, NCEE, is a paramedic at Cone Health CareLink Mobile Critical Care in Greensboro, N.C.
Roger L. Layell, AAS, FP-C, CCP-C, CCEMT-P, NRP, is a flight and critical care paramedic at Atrium Health MedCenter Air in Charlotte, N.C. He has 17 years of experience as a paramedic and 12 years in the HEMS environment.
