Wide complex tachycardias detected by smartwatch: what is the diagnosis?

Abstract

CASE 1 Clinical presentation A 64-year old woman with no significant past medical history presented to our cardiology clinic for recurrent intermittent palpitations at rest for the past 7 years. She also had an episode of left-sided chest pain. Her symptoms occurred about once a month, lasted 2–3 h with sudden onset and offset and were irregular in nature. The symptoms were associated with giddiness, and she complained of lethargy after the palpitations stopped. She did not have any near-syncopal or syncopal episodes. The patient is a non-smoker and non-drinker, and does brisk walking twice a week (30–45 min each session). Her electrocardiogram (ECG) at the clinic showed normal sinus rhythm with normal PR, QRS and QTc interval [Figure 1]. Serial event monitors (including 24-h monitoring, 14 days of transtelephonic ECG monitoring) showed intermittent rate-related left bundle branch block (LBBB), no significant pause and infrequent premature atrial (<1%) and ventricular (<1%) ectopics. No symptom was recorded while she was on the event monitors.Figure 1: Case 1. 12-lead ECG shows normal sinus rhythm with normal PR, QRS and QTc interval.Other investigations included computed tomography (CT) coronary angiogram, which showed minor coronary artery disease. The patient’s myocardial perfusion imaging was negative for ischaemia, and 2D echocardiography showed a normal left ventricular ejection fraction (LVEF) of 57%, normal left atrium (LA) size (LA volume 29.9 mL/m2) and mild to moderate mitral regurgitation. The patient continued to have intermittent symptoms despite being started on beta-blocker empirically. Due to her recurrent symptoms, her son decided to use his Apple Watch to record the ECG tracing for her whenever she was symptomatic. ECG interpretation The smartwatch ECG tracing (correlates to lead I) showed an irregularly irregular wide complex tachycardia [Figure 2]. The differential diagnosis included the following the: (a) atrial fibrillation (AF) with rate-related bundle branch block; (b) pre-excited AF; and (c) polymorphic ventricular tachycardia (VT) (torsades de pointes).Figure 2: Case 1. Smartwatch ECG tracing (represents lead I) shows an irregularly irregular wide complex tachycardia.Clinical course The patient was counselled on AF due to her symptoms and tracing from her smartwatch. In the later part of the day, she was admitted to the hospital for sudden onset of palpitations associated with shortness of breath when climbing the stairs. On examination, her pulse was irregularly irregular. The rest of the physical examination was unremarkable. The patient’s ECG showed an irregularly irregular wide complex (left bundle branch block pattern) tachycardia [Figure 3], similar to that shown by the smartwatch ECG tracing. The patient was diagnosed with AF with aberrancy and rapid ventricular rate of 160 bpm. Her troponin T level was normal at 5 ng/L and electrolytes were normal.Figure 3: Case 1. 12-lead ECG shows an irregularly irregular wide complex (left bundle branch block pattern) tachycardia.The patient was given a dose of intravenous amiodarone 150 mg and the rhythm converted to sinus rhythm [Figure 4]. She was started on flecainide 100 mg bd, and her bisoprolol dose was increased to 1.25 mg bd to achieve better rate control. She was asymptomatic and remained in normal sinus rhythm on the day of discharge.Figure 4: Case 1. 12-lead ECG shows conversion back to normal sinus rhythm after administration of intravenous amiodarone.CASE 2 Clinical presentation A 19-year-old woman presented with sudden onset and offset of recurrent paroxysmal palpitations. Her symptoms were not related to physical exertion, and each episode lasted 30 min to 1 h. Her cardiologist ordered a cardiac event recorder for 1 month, but no arrhythmias were captured. Her resting 12-lead ECG showed normal sinus rhythm, normal PR, QRS and QTc interval with no pre-excitation [Figure 5]. Echocardiography showed a structurally normal heart. Six months later, she developed palpitations again, and this was captured on her smartwatch.Figure 5: Case 2. 12-lead ECG shows normal sinus rhythm, normal PR, QRS and QTc interval with no pre-excitation.ECG interpretation The ECG tracing captured on her smartwatch showed a regular wide complex tachycardia [Figure 6]. The differential diagnoses included the following: (a) supraventricular tachycardia with aberrancy (SVT); (b) VT; and (c) atrial flutter with 1:1 conduction.Figure 6: Case 2. Smartwatch ECG tracing shows a regular wide complex tachycardia.Clinical course The patient subsequently underwent an electrophysiology study, which confirmed the diagnosis of SVT with aberrancy. The electrophysiology study showed that the patient had orthodromic atrioventricular re-entrant tachycardia with the retrograde limb up the concealed left free wall accessory pathway, and radiofrequency ablation was carried out successfully. DISCUSSION It can be challenging to interpret a single-lead ECG tracing on a smartwatch. One of the differentials for Case 1 is pre-excited AF. This is less likely as there was no slow QRS upstroke that may indicate ventricular pre-excitation. Furthermore, a previous ECG [Figure 1] did not show evidence of ventricular pre-excitation. The other differential is polymorphic VT (torsades de pointes), which is characterised by undulations of continually varying amplitudes that appear alternately above and below the baseline and are commonly associated with long QTc. However, in Case 1, the QRS complexes were similar in amplitude and morphology. The ‘twistings of the points’ was likely due to a wandering ECG baseline caused by the wrist motion while the patient was recording the ECG on her smartwatch. The smartwatch ECG tracing showed a wide complex tachycardia, which was irregularly irregular, suggestive of AF. The patient also had a pre-existing history of rate-related LBBB with a similar QRS morphology captured on previous Holter. Taking into consideration the clinical presentation, this makes AF with rate-related bundle branch block the most likely diagnosis in the absence of syncopal episode or cardiac arrest. One of the differentials for Case 2 is idiopathic VT. The patient had no previous history of underlying ischaemic heart disease or structural heart disease, which makes VT due to underlying substrate less likely. Supraventricular tachycardia with aberrancy and atrial flutter with 1:1 conduction are other possible differentials. Unfortunately, it will be difficult to differentiate these differential diagnoses without performing an electrophysiology study. The use of smartwatch ECG as an adjunct for the detection of clinically significant arrhythmias has been increasingly reported in the literature. This includes the diagnosis of AF,[1,2] atrial flutter,[3] SVT[4,5] and VT.[6] The US Food and Drug Administration (FDA) device classification decision published on 11 September 2018 states that an ECG software device for over-the-counter use creates, analyses and displays ECG data and can provide information for identifying cardiac arrhythmias. The device is not intended to provide a diagnosis. The statement added that the ECG waveform is meant to supplement rhythm classification for the purpose of discriminating AF from normal sinus rhythm, and is not intended to replace traditional methods of diagnosis or treatment.[7] The FDA states that this device should be classified as a Class II device under the generic name, ‘electrocardiograph software for over-the-counter use’. These two cases highlight the importance of consultation with a medical professional for clinical decision-making, and patients should be advised to seek medical attention if they are symptomatic, so that a 12-lead ECG can be performed to detect all types of arrhythmias and not just AF. This is especially important for both cases presented in this article, given the differentials of an irregular wide complex tachycardia and a regular wide complex tachycardia. The 2020 European Society of Cardiology guidelines for the diagnosis and management of AF also states that when AF is detected by a screening tool, including mobile or wearable devices, a single-lead ECG tracing of ≥30 s or 12-lead ECG showing AF analysed by a physician with expertise in ECG rhythm interpretation is necessary to establish a definitive diagnosis of AF. When AF detection is not based on an ECG recording or in case of uncertainty in the interpretation of device-provided ECG tracing, a confirmatory ECG diagnosis has to be obtained using additional ECG recording (e.g. 12-lead ECG, Holter monitoring, event loop recorder, implantable loop recorder, electrophysiology study, etc.).[8] Of note, the smartwatch used in Case 1 did not belong to the patient. This highlights the ease of patients’ access to the use of a smartwatch even if they do not own one. Physicians will likely see more patients presenting to the clinic with ECG recordings from their smartwatches. The smartwatch could potentially be used as an adjunct to diagnose arrhythmias; however, it should not replace clinical practice based on established guidelines. Patients should also be reminded to seek medical attention if they are symptomatic. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. SMC CATEGORY 3B CME PROGRAMME Online Quiz: https://www.sma.org.sg/cme-programme Deadline for submission: 6 pm, 07 December 2023