A meta‐analysis of outcomes after IVUS‐guided vs. angiography‐guided DES implantation in 26 503 patients enrolled in three randomized trials and 14 observational studies, demonstrated that IVUS‐guided PCI was associated with a significantly lower risk of TLR (OR 0.81; p = 0.046). In addition, the risk of death (OR 0.61; p <0.001), MI (OR 0.57; p <0.001), and stent thrombosis (OR; p <0.001) were also decreased [47]. A recent metanalysis of 10 RCTs (5007 participants, which include the largest RCTs IVUS‐XPL and ULTIMATE Trial) including patients with CTO, stable ischemic heart disease or presented as ACS showed that routine use of IVUS was effective in reducing TLR (RR 0.59; p < 0.01), TVR (RR 0.59; p < 0.01), and MACE (RR 0.63; p < 0.01). Cardiovascular mortality was also significantly reduced (RR 0.51; p = 0.04) [48].
Clinical outcomes using IVUS for LMCA PCI
Observational Studies
Observational studies overall provide robust evidence of benefit for intracoronary imaging. A multicenter revascularization for unprotected left MAIN coronary arterystenosis: COMparison of Percutaneous coronary Angioplasty versus surgical Revascularization (MAIN‐COMPARE) [50] registry of LMCA interventions showed that patients treated with IVUS‐guided DES implantation had better three year survival than patients in whom IVUS was not used to guide LMCA DES implantation (4.7% vs 16.0%, p = 0.048). A pooled analysis of four Spanish registries examined the outcomes of 1670 LMCA PCI patients. By means of matching, 505 patient pairs were constructed and survival free of cardiac death, MI, and target lesion revascularization at 3 years was 88.7% in the IVUS group and 83.6% in the non‐IVUS group (p =0.04) [51].
In a single‐center analysis by Gao et al. including consecutive patients with unprotected LMCA stenosis who underwent DES implantation, unadjusted MACE rates at one year follow‐up were significantly lower in the IVUS‐guided group. These findings were consistent after propensity‐score matching, driven by a reduction in cardiac death and target vessel revascularization (TVR) [52].
In another study, using the Swedish Coronary Angiography and Angioplasty Registry (SCAAR), both a retrospective and a propensity‐matched analysis of 2468 patients, the authors showed that at 10 years of follow‐up, IVUS guidance reduced mortality compared to angiographic guidance from 62.1 to 32.5% (HR = 0.44) overall and from 56.6 to 33.7% (HR=0.57) in propensity score‐matched patients [53].
Recently, a single‐center registry of 6005 patients assessed the impact of IVUS‐guided PCI on long‐term (64 months median follow‐up) in patients undergoing PCI for complex lesions (11.4% LMCA PCI). IVUS guidance was associated with a reduction in cardiac mortality both overall, in every patient subgroup, and in almost every lesion subgroup. Overall, IVUS‐guided DES implantation was associated with a signifcantly lower risk of cardiac death compared with angiography‐guided DES implantation (10.2% vs 16.9%; HR = 0.57, p<0.001) [54].
The largest observational study so far involved an analysis from the British Cardiovascular Intervention Society (BCIS) database. Imaging guidance (mostly IVUS) for LMCA PCI increased from 30.3% in 2007 to 50.2% in 2014. Of note, imaging guidance was associated with lower 30‐day and 12‐month all‐cause mortality rates. Operators with greater LMCA PCI volumes had greater mortality reductions when these operators used IVUS guidance [55].
Metanalysis
In the meta‐analysis by Ye et al. that included 10 studies, IVUS guidance was associated with a reduction in all‐cause mortality (RR = 0.60, p < 0.001), cardiac mortality (RR = 0.47, p < 0.001), myocardial infarction (RR = 0.80, p = 0.12), and stent thrombosis (RR = 0.28, p = 0.004). In the meta‐analysis by Wang et al. that included seven studies (only some of which were included in the Ye meta‐analysis), IVUS guidance was associated with a reduction in all‐cause mortality (RR= 0.55, p < 0.001), cardiac mortality (RR= 0.45, p<0.001), myocardial infarction (RR=0.66, p <0.001), and stent thrombosis (RR=0.48, p=0.001) [46].
Special imaging cases
IVUS provides the potential for reduced contrast volume with an upfront low contrast IVUS‐guided strategy as demonstrated in recent studies zero‐contrast IVUSguided PCI. [56,57]. Efforts are underway to develop noncontrast‐based flush media alternatives for optical coherence tomography (OCT) [58]. IVUS is also important for PCI for chronic total occlusion intervention (see relevant chapter); identifying and crossing the proximal fibrous cap, determining whether the wire and IVUS catheter are in the true or false lumen proximally and distally before stenting to avoid implanting a stent into a false lumen, guiding stent optimization, and assessing complications. IVUS is also the preferred modality to visualize the true lumen especially after guidewire crossing because it avoids hydraulic forces that occur with forceful injection of flush media (i.e. risk to widen the flap if wiring went in the false lumen) with either angiography or OCT.
Conclusions
Grayscale IVUS provides (i) high quality, tomographic imaging of the lumen, the atheroma, and the vessel wall, (ii) incremental and more detailed qualitative and quantitative information than coronary angiography, (iii) practical guidance for percutaneous coronary intervention, and (iv) many clinical and research insights. IVUS has become an important part of DES studies, representing an effective way to understand the mechanisms, effects, and complications of stent technology. PCI optimization with IVUS after stent implantation has been associated with a reduction in death as well as other hard end points of myocardial infarction and stent thrombosis. Development of high‐definition IVUS, hybrid IVUS‐OCT imaging or integration of novel techniques, including IVUS and near‐infrared spectroscopy may represent the next intracoronary imaging frontier.
Interactive multiple choice questions are available for this chapter on www.wiley.com/go/dangas/cardiology
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