“…Three studies [17,34,36] adopted a crossover design while the remaining adopted a parallel design [1,2,4,5,7,8,15,18,19,[24][25][26][27][28][29][30][31][32][33]36]. Twenty-one studies [1,2,4,5,8,15,[17][18][19][26][27][28][29][30][31][32][33][34][36][37][38] provided LVEF values at baseline and after pacing, eight [2,4,8,15,31,32,37,38] of ...…”