Answer: Peripheral arterial pressure wave in the presence of ventricular asystole

What is the most probable aetiology of the radial arterial pressure tracing and peripheral saturation read, in the absence of QRS waves, depicted in Panels D/E and Supplementary material online, Video S1? Chest compressions during cardiopulmonary resuscitation Mechanical circulatory support device Atrial contraction in the presence of ventricular standstill A technical artefact Ventricular asystole is well described due to transient AV block from stimulation of vagus nerve fibres,1 as was previously described in patients during tracheal suctioning.2 This is a rate-dependent phenomenon where the conducted sinus node activation suppresses intrinsic ventricular activation at higher rates. There has not previously been a description of the haemodynamic phenomena associated with this transient ventricular asystole. Review of concomitant radial arterial line tracing and O2 saturation reading revealed pressure waves immediately after each non-conducted P-wave (in the complete absence of QRS complexes), followed by an O2 saturation wave (Figure 1, Panels D and E), that were both distinct and smaller in size, than the arterial and saturation waves caused by each QRS complex, before and after the transient AV block (Figure 1, Panel F). The arterial pressure waves recorded during ventricular asystole in this case represent ejection of blood through the aortic valve, originating from left atrial contraction3 alone, in the presence of ventricular standstill. To the best of our knowledge, this is the first description of such haemodynamic tracing, illustrating the ability of the left atrium to contract and induce modest ventricular ejection in the presence of ventricular asystole. Telemetry recordings from a mechanically ventilated patient with sudden intermittent bradycardia and transient asystole. Panel A: Bradycardia in keeping with a vagal response pattern, with sudden prolongation of P-P and R-R intervals. Panel B: Progressive atrioventricular block with no ventricular activation. Panel C: Spontaneous resolution of atrioventricular block. Panel D, E & F: Concomitant telemetry (green) radial arterial line (red) and O2 saturation (blue) tracing during ventricular asystole and recovery. Supplementary material is available at European Heart Journal: Acute Cardiovascular Care. D.H.B. is supported by a research grant from TRANSFORM HF. The data underlying this article cannot be shared due to the privacy of individual that participated in this report and the limitations of the consent provided for this publication.