The world has now completed 2 years of living with COVID-19. In developing nations, especially in Africa, limited vaccine availability has led to high case rates and the emergence of new variants, some of which are more virulent or contagious than wild-type SARS-CoV-2. With the Omicron variant, the pandemic is now transitioning to an epidemic because of widespread natural virus immunity from a less-virulent infection. We may soon have a combined RNA vaccine for annual single immunization for both the influenza virus and COVID-19.

The COVID-19 pandemic has required a retooling of education, necessitating virtual education innovation as well as changes in clinical practice. In this issue, Kashetsky et al examine the bedside use of the portable 8-MHz Doppler to detect Doppler arterial waveforms (DAW) as an alternative to the ankle-brachial pressure index (ABPI). The ABPI is the standard bedside test for ruling out arterial disease and usually is measured with a dorsalis pedis or posterior tibial systolic BP versus the highest brachial systolic BP in the arm. If this ratio is equal or higher than 0.9, there is a biphasic or triphasic arterial waveform.

The scoping review also recommends DAW as an alternative to the ABPI. Alavi and colleagues1 investigated the audible signal from the DAW and compared this signal to the ABPI in a certified vascular lab. The presence of audible biphasic and triphasic arterial waveforms were equivalent to an ABPI >= 0.9 and distinguishable from the monophasic or absent sound that is characteristic of arterial disease. The signals can be recorded with an MP4 format available on most smartphones. The audible test is faster to perform, not influenced by calcification, and does not require the patient to be recumbent or to have his or her calf squeezed with a BP cuff. This test can be completed in the home, avoiding COVID-19 spread and the formal arterial study delays in the vascular laboratory, which are only necessary if there is a monophasic or absent monophasic signal.

Idiopathic chilblains have long been associated with damp and cold exposure. Since the onset of COVID-19, young patients have been developing chilblain-like symptoms after COVID-19 infection. In this issue, Ganier and colleagues analyzed publicly available single-cell RNA data sets to identify the angiotensin-converting enzyme 2 receptors in the skin, specifically in keratinocytes and the cutaneous vasculature. These receptors facilitate SARS-CoV-2 entry into cells and may facilitate locally invasive infection, but the virus could also come from the blood stream and respiratory acquisition of infection.

In a recent prospective study, Kolivras et al2 noted that COVID-19-related chilblains have clinical and histologic features that are similar to idiopathic chilblains, but other secondary etiologies need to be ruled out. Electron microscopy revealed rare spike proteins within the endothelium that would be consistent with COVID-19. No patient with COVID-19 had a systemic coagulopathy. Common symptoms in the 29 evaluable patients with chilblains included: erythema/edema (19/29, 65.61%), lesions on the dorsal side of digits (27/29, 93.1%), papules and plaques (15/29, 51.72%), erosions/ulcers/crusts (15/29, 51.72%), and violaceous colour/purpura (13/29, 44.82%).

The world has changed. The new normal will include audible handheld Doppler exams in patients' homes or at ambulatory clinics. It also includes a new understanding of chilblains appearing after COVID-19 often in children and young adults. Luckily, most COVID-19 related chilblains patients are self-limited and do not require treatment.

R. Gary Sibbald, MD, DSc (Hons), MEd, BSc, FRCPC (Med Derm), FAAD, MAPWCA, JM

Elizabeth A. Ayello, PhD, MS, BSN, RN, CWON, ETN, MAPWCA, FAAN

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