Table 1: Summary of Trials Supporting Use of Intravascular Ultrasound in Complex Percutaneous Coronary Intervention.

Study	Sample Size	Focus	Findings	Limitations
Patel et al. 2012[15]	449 (247 with IVUS, 202 without)	Long-term outcomes associated with using IVUS for treatment of bifurcation lesions	IVUS associated with lower rates of death, MI, TVR, and TLR	Selection bias by operators No prespecified stenting criteria
Chen et al. 2018[16]	1,465 (310 with IVUS, 1,155 without)	Composite MACE (cardiac death, MI, TVR) at 1 and 7 years after treatment of bifurcation lesions with IVUS versus angiography	IVUS was associated with lower rate of MACE at 1 and 7 years, with a more significant difference at 7 years. IVUS was also associated with lower rates of revascularization compared with angiography-guided PCI	Non-randomized Relatively lower rate of angiographic follow-up at 1 year
Kim et al. 2015[19]	402 (201 with IVUS, 201 without)	Cardiac death and composite MACE (cardiac death, MI, TVR) rates in CTO using IVUS-guided versus angiography-guided PCI	Cardiac death was not significantly lower, but MACE rates were significantly lower in IVUS group than in angiography group	Minimum stent areas used may have been too small No clear reason for improved clinical outcomes
Andell et al. 2017[21]	2,468 (621 with IVUS, 1,847 without)	Composite endpoint of all-cause mortality, restenosis, or definite stent thrombosis in IVUS-guided versus angiography-guided PCI for unprotected left main disease	IVUS group had significantly lower rates of primary composite endpoint and mortality compared with angiography group	Comorbidities and age difference in non-IVUS group Registry does not include whether IVUS used before PCI, after PCI, or both Not able to account for skill differences in operators
Choi et al. 2019[22]	6,005 (1,674 with IVUS, 4,331 without)	Long-term cardiac death risk in patients with complex lesions using IVUS-guided versus angiography-guided PCI	IVUS-guided PCI associated with significantly lower risk of cardiac death, as well as all-cause death, MI, ST, TLR compared with angiography-guided PCI on complex lesions	Non-randomized Selection bias by operators Confounding comorbidities in angiography group

CTO = chronic total occlusion; IVUS = intravascular ultrasound; MACE = major adverse cardiac events; PCI = percutaneous coronary intervention; ST = stent thrombosis; TLR = target lesion revascularization; TVR = target vessel revascularization.