Fig. 2.1
MATRIX Access trial: Kaplan Meier curves for the co-primary end-points (Reprint with permission from Ref. [10])
No differences were observed with respect to myocardial infarction or stroke between the two groups. Radial approach significantly reduced vascular access complications and red blood cell transfusion compared with femoral access, with similar PCI success rates. Evidence for an interaction between tertiles of the centers’ percentage of radial PCI and allocated access site was noted for both two co-primary end-points (Pint = 0.0048) with a pronounced benefit of radial access in center that did at least 80 % radial PCI. On the other hand, the anti-thrombin regimen used as per randomization scheme (bivaliridin vs. unfractionated heparin) did not modify the effect of arterial access site. Moreover, in contrast with the RIVAL results, the radial benefit was consistent across ACS patients [10].
In order to put the MATRIX Access results in the context of prior trials, the authors performed a meta-analysis updating those reported by RIVAL investigators, which confirms a significant mortality and MACE reduction in the radial as compared to femoral group [10]. (Fig. 2.2).
Hence, when taken together, the MATRIX Access study and the update meta-analysis suggest that radial access, reducing MACE, major bleeding and mortality, should become the default approach for patients with acute coronary syndrome undergoing invasive management [10].
2.4 Learning Curve and Expertise
Many studies attempted to define the learning curve of the trans-radial approach.
Ball et al. prospectively collected almost 1,700 patients with single vessel disease, undergoing non-urgenttrans-radial PCI by different physicians. The outcomes were stratified according to the time of operators starting trans-radial experience. The control group included only expert radial operators (>300 trans-radial procedures). The study showed that the PCI failure occurrence was inversely associated with the physician experience; about 30 % reduction of PCI failure every additional 50 radial procedures performed was observed [11].
More recently, Hess et al. investigated the learning curve for radial PCI among 54,561 procedures performed at 704 centres. Interestingly, as radial caseload increased, higher-risk patients were chosen (i.e., women, ST-segment elevation myocardial infarction and emergency indications). There was higher use of fluoroscopy time and contrast among newer (<30–50 cases) compared with more experienced (>30–50 cases) operators whereas procedural success rate was linearly associated with greater operator radial experience. The authors concluded that the threshold to overcome the learning curve appears to be approximately 30–50 cases [12].
It has been suggested that left radial approach may have a shorter learning curve compared to the right radial access, owing to a lower impact of subclavian tortuosity in the left radial artery. Moreover, standard diagnostic and procedural catheters have been largely designed for the femoral route and as such may better adapt to left than right radial access site [13].
The radial approach requires expertise of both individual operators and institutional teams. The consensus document performed by the European Association of Percutaneous Cardiovascular Interventions in 2013 reported that, after learning curve, over 50 % radial access in routine practice with a minimum of 80 procedures/year per operator (including diagnostic and interventional procedures) should be a reasonable objective for achieving an average satisfactory proficiency [14].
In the RIVAL study, that included operators who had cumulatively performed at least 50 trans-radial catheterization at the randomization time, a significant interaction between access site and volume radial centers was observed for the primary outcome, with benefit for radial access in highest tertile [7].
Although MATRIX Access trial used a more strict selection of expert radial and femoral operators (at least 75 trans-radial intervention) the center proportion of radial PCI emerged as treatment modifier for both co-primary endpoints and all cause death. When major bleeding was separately appraised, there was no such effect of radial versus femoral access. These observations may suggest that while the bleeding benefit accrues at an earlier stage of the learning curve of trans-radial intervention, high proficiency and superior efficacy as compared to femoral requires high skills which can be met only by high volume radial operators [10].
2.5 Bleeding Issue
Bleeding related to the access site occurred in 30–70 % of PCI [15]. This high variability probably depends on patient’s clinical presentation, concomitant medications and employed bleeding definition.
Based on MATRIX results, radial approach is associated to a 63 % reduction of access site related major bleeding, 33 % decrease of non–CABG-related major bleeding (Fig. 2.3) and 38 % reduction of transfusion rates compared with the femoral route [10].
Fig. 2.3
MATRIX Access trial: bleeding events in radial and femoral groups according to BARC, TIMI and GUSTO classifications
Interestingly, the bleeding benefit of radial approach persisted also when vascular closure devices were employed in the femoral arm [16].
Considering the potential relationship between major bleeding and mortality, the reduction of bleeding events is of paramount importance.
Rao et al. demonstrated, in a large cohort of patients with NSTEACS, that bleeding severity was significantly related to 30-day mortality [17].
A sub-study of the TRITON-TIMI 38 trial that there was a high correlation between serious spontaneous bleeding and mortality within the first month after PCI [18].
Similarly, a sub-analysis of the PLATO trial demonstrated that bleeding related to the procedure strongly affected death at early follow-up [19].
As consequence of these findings, bleeding prevention strategies have been applied demonstrating a better survival in ACS patients.
In the OASIS-5 trial fondaparinux was found to be not inferior compared with enoxaparin in terms of ischemic outcomes and superior with respect to major bleeding at 9 days eventually resulting in a significant decrease of 30-day all-cause death [20].
Moreover, in the HORIZONS AMI the implementation of the bivalirudin compared with unfractionated heparin plus GPI in patients who underwent primary PCI, resulted in a reduction of both major bleeding and mortality at 30 days [21].
Finally, the EUROMAX trial showed that upstream bivalirudin compared with heparin use, in a context of new antiplatelet drugs (i.e., prasugrel and ticagrelor), reduced 30-day mortality or major bleeding [22].
2.6 Does the Radial Approach Reduce the Mortality?
Before the RIVAL study, many registries showed a mortality benefit of trans-radial as compared to the trans-femoral approach [4, 23, 24].
The unexpected results of RIVAL trial tempered the enthusiasm showing a not significant mortality difference between the two access groups. However, in the subgroup of STEMI patients with STEMI a 54 % mortality reduction after the trans-radial treatment was observed. On the other hand, in patients with NSTEACS a trend towards a 66 % higher mortality rate was noted (P = 0.082) [7].
In the RIFLE-STEACS trial a significant decrease of 30-day mortality was found in the radial group [8].
In the REAL registry a significant mortality reduction was reported in the radial versus femoral group at both early- and long-term follow-up [5].
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