Pseudo-V1 ECG lead recording with quality smartwatches and medical interpretation may be necessary for timelyand accurate remote detection of atrial flutter/fibrillation.

Background: Remote rhythm monitoring with wearable devices is increasingly used especially for early detection of atrial fibrillation/flutter (AF/Afl), being the access to hospital discouraged, especially for frail elderly patients, due to the burden and risk of COVID-19 pandemic. Whereas devices using photo plethysmography (PPG) may misinterpret as AF pulse irregularities due to extrasystoles, patient-directed recording of a single (usually wrist-to-wrist) lead ECG (LEAD I) with hand-held devices or smartwatches have been developed to increase accuracy in AF detection. However, although recent studies validating such devices single-lead ECG recording have shown high sensitivity and specificity, false negative findings such as those reported here are still possible and must be prevented (1). Purpose: Given previous experience of diagnostic uncertainty or failure of the smartwatch ECG (SW-ECG) LEAD I to detect AF/Afl, we have tested if false negative diagnosis could be avoided by recording in addition at least one right precordial (pseudo-V1) lead analyzed by a trained healthcare professional. Method: Over one calendar year observation, five patients with previous history of ablated supraventricular arrhythmias suffering sudden palpitations suspected of paroxysmal AF/Afl were instructed to record with their smartwatch at least one precordial lead in addition to LEAD I, to monitor ECG until the termination of symptoms. The SW-ECG strips were sent by telephone for professional interpretation. Diagnostic accuracy based on LEAD I and pseudo-V1 were independently validated by two cardiologists (diagnostic goldstandard - DGS). Results: 22 AF/Afl events occurred. Pharmacological cardioversion to sinus rhythm (SR) was obtained in 64%. 192 ECG strips were transmitted. 43,7% of the strips were automatically classified as "not significant" (or not valid"). Compared to DGS, out of 108 "valid" strips, correct automatic identification of AF/Afl was obtained in 36,4 % with LEAD I, in 33,3% with pseudo V1 and in 54,5% with combined leads, respectively. Interestingly, SW algorithm frequently misdiagnosed as SR, not only LEAD I, but also pseudo-V1 strips despite clear-cut evidence of typical flutter waves (39,4%), when RR intervals were regular due to high degree (e.g., 4:1) A-V block (Figure 1) Conclusions: With simple instructions, patients (or their relatives) can easily record an additional precordial (pseudo-V1) SW-ECG lead, that may enhance sensitivity and specificity for remote detection of AF/Afl. However, at present, visual interpretation of SW-ECG by a trained healthcare professional is still needed to guarantee a 100% correct diagnosis of AF/Afl, crucial to reduce thromboembolic risk and timely initiate the appropriate treatments.