Clin Res Cardiol (2021). 10.1007/s00392-021-01933-9

Atrial stimulation in the proximal coronary sinus in a patient with a ‘silent atrium’

B. M. Quesada Ocete1, H. Mollnau1, T. Konrad1, P. M. G. Seidel1, M. Hoffmann1, A. Marx1, R. Spittler1, T. Rostock1

1Kardiologie II - Rhythmologie, Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Mainz;

A 56-year-old woman with a known permanent congenital complete atrio-ventricular heart block (AVB) presented a new onset of symptomatic persistent common type flutter (aFlutt) with a ventricular rate of 36/min.  Due to asymptomatic status of the AVB, she had rejected pacemaker implantation earlier. Prior to electrical cardioversion (EC) we agreed to implant a dual chamber pacemaker, due to an increasing number of bradycardia induced premature ventricular contractions. During initial implantation, the placement of the atrial lead was difficult and prolonged due to poor atrial sensing (AS) at several typical sites in the right atrium (RA) (RA appendage (RAA) and high and lateral RA) during aFlutt. The electrode was placed in the typical position (RAA). After intraprocedural EC no atrial activity was detected with an AS <0.1 mV and an exit block at high voltage (pacing capture threshold (PCT) >5 V/1.5 msV/ms), with an impedance around 600 Ohm. Ventricular parameters were normal. Given the prolonged procedural duration, the atrial electrode was left in this position and reevaluation depending on her clinical process was planned. She was admitted 6 months later in our clinic with fatigue and discrete shortness of breath, presenting a pacemaker syndrome due to undersensing and exit block of the atrial lead at continuous sinus rhythm (SR). Consequently atrial lead revision was planned. During this second approach, atrial mapping reassessment was carried out using a new lead (Boston Scientific, Ingevity MRI 7741) at several typical sites for RA lead implantation. The maximal recorded AS was 0.25mV at the mid atrial septum and inferior RA with an exit block of PCT at any right atrial site (PCT > 7.5V/ms). In SR, a notched P wave in limb leads on surface ECG was observed with an inter-peak duration ≥ 0.04s (Figure 1A). We decided to map the coronary sinus (CS) with the new electrode. The CS was additionally cannulated using a pentapolar catheter over the subclavian vein through a CS guide sheath (Boston Scientific, Hook). To increase lead stability, we usually prefer an active fixation lead, as in previous reports this technique had been successful. At the proximal CS, sensing of 3,7 mV and a PCT of 1.0 V /0.4 ms were obtained. The lead was fixated proximally inside the CS. Before discharge, parameters remained stable, during atrial stimulation P-waves could be documented in the surface ECG and EGM (Figure – 1B), the patient reported symptom improvement. During 12-month follow-up, atrial parameters were: AS of 6.6mV, atrial PCT of 0.8 V at 0.4 ms and impedance 888 Ohms. The RA pacing percentage was <1% while the ventricle was paced at 99% at a programmed lower rate limit of 50 bpm. Atrial standstill (AS) is a rare condition characterized by the absence of electrical and mechanical atrial activity in which RA pacemaker lead implantation can fail owing to the inability to capture RA tissue at conventional pacing sites. In this case of a patient with a binodal disease with permanent AS, we were able to achieve sufficient atrial stimulation at the proximal CS. Figure 1: A) Surface ECG showing a notched P wave (red arrow). The chest X-ray in posteroanterior (B) and lateral (C) views showing lead location (star: atrial electrode, yellow arrow: right ventricular lead). D) shows the electrogram derived from the atrial and ventricular leads (AS: atrial sense, VP: ventricular pacing), the ventricular signal in CS from the atrial electrogram is circled.

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