Study design and stimulation protocols. Phase I-tested pacing-induced diaphragmatic stimulation (PIDS)-ventricular pacing configurations and different coupling intervals between the ventricular pacing and PIDS in both symptomatic and asymptomatic settings. Phase II monitored the consistency of the haemodynamic effect of PIDS for up to 1 h. Phase III followed the phase II protocol together with a repeated stimulation after 24 h to examine reproducibility of the haemodynamic effect of PIDS. AV, atrioventricular; DDD, atrioventricular synchronous pacing mode; EMAT, electromechanical activation time; PIDS, pacing-induced diaphragmatic stimulation; PR, ECG interval from P wave to R wave; Vp, ventricular pulse.