Abstract
Background
Radiation absorbed by interventional cardiologists is a frequently under-evaluated important issue. Aim is to compare radiation dose absorbed by interventional cardiologists during percutaneous coronary procedures for acute coronary syndromes comparing transradial and transfemoral access.
Methods
The randomized multicentre MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX) trial has been designed to compare the clinical outcome of patients with acute coronary syndromes treated invasively according to the access site (transfemoral vs. transradial) and to the anticoagulant therapy (bivalirudin vs. heparin). Selected experienced interventional cardiologists involved in this study have been equipped with dedicated thermoluminescent dosimeters to evaluate the radiation dose absorbed during transfemoral or right transradial or left transradial access. For each access we evaluate the radiation dose absorbed at wrist, at thorax and at eye level. Consequently the operator is equipped with three sets (transfemoral, right transradial or left transradial access) of three different dosimeters (wrist, thorax and eye dosimeter). Primary end-point of the study is the procedural radiation dose absorbed by operators at thorax. An important secondary end-point is the procedural radiation dose absorbed by operators comparing the right or left radial approach. Patient randomization is performed according to the MATRIX protocol for the femoral or radial approach. A further randomization for the radial approach is performed to compare right and left transradial access.
Conclusions
The RAD-MATRIX study will probably consent to clarify the radiation issue for interventional cardiologist comparing transradial and transfemoral access in the setting of acute coronary syndromes.
1
Introduction
Interventional cardiologists are routinely and chronically exposed to ionizing radiations that are necessary to perform diagnostic and interventional coronary procedures. Moreover, some reports have shown that the radiation dose absorbed by interventional cardiologists is the greatest registered by any medical staff exposed to X-rays .
Even if radioprotection is an important issue for operators due to the long term stochastic risk of radio-induced cancer , this issue is often under evaluated.
1.1
Radiation risk for interventional cardiologists
Generally the stochastic risk related to radiation is an all-or-none phenomenon for any individual cell, but the greater the radiation exposure, the bigger number of injured cells . Other than cancerous effects, such as cataract formation, were found to be statistically related to radio-exposure . In a recent study an increased risk for brain and neck tumours has been observed among physicians performing interventional procedures. Consequently, operators should apply all efforts to reduce their exposition to radiation dose according to the ALARA principle : operators should maintain radiation exposure at a level that is “As Low As Reasonably Achievable”, limiting the duration of exposure, increasing the distance from the radiation source and implementing the shielding equipment.
Radiation dose can be expressed in different ways: the Air Kerma is the amount of energy absorbed in a given mass of air, whereas the dose area product (DAP) is the absorbed dose of radiation across a given surface area. Generally DAP measurements are more accurate than using Air Kerma measurements for the estimation of patient radiation dose as DAP allows for variations in field size . DAP consents a good estimation of the dose to the irradiated tissue and is an indicator for patient cancer risk. Differently Sievert is the unit used to express the biological damage to human tissues and to evaluate the radiation dose absorbed by operators.
1.2
Transradial approach and clinical outcome
The number of percutaneous diagnostic and interventional percutaneous coronary procedures performed through transradial approach is progressively increasing worldwide . The many reasons for this “radial boom” include a reduction in vascular complications and a better patient comfort compared to transfemoral approach. Moreover there is now a growing body of evidence that transradial approach might be associated with a better outcome in patients with acute coronary syndromes. The RIVAL and the RIFLE-STEACS trials are two randomized studies that showed a significant reduction in mortality with the transradial compared to transfemoral access in patients with acute ST elevation myocardial infarction. Also in non-ST elevation myocardial infarction there is a possible advantage in terms of better outcome for transradial approach even if data are conflicting. Indeed a better outcome associated with transradial approach in this subset of patients was shown in some observational studies although it was not confirmed in the RIVAL study . The MATRIX trial and possibly other randomized studies will clarify this issue.
1.3
Radiation exposure according to vascular access
Despite multiple advantages of transradial approach, a possible drawback of this access is a higher radiation exposure compared to transfemoral approach. The radiation risk might be increased both for the physician and for the patient even if data are conflicting . Most of the studies evaluated only the radiation dose absorbed by patients and expressed it as DAP or Air Kerma ( Table 1 ): some studies showed a significant increase in radiation dose for transradial compared to transfemoral approach, other studies showed no differences between the two approaches while in few studies a lower radiation dose for transradial approach was observed. The major bias of these studies is the observational design of the vast majority with only a few being randomized. To correct for the potential procedural biases, some authors performed a multivariate analysis , and in only one case the transradial approach was an independent predictor of increased radiation dose . Another limitation of these studies is that most have assessed the fluoroscopy times, the DAP or the Air Kerma, that are only indirect measures of the radiation dose absorbed by operators. Only few studies used dedicated operators’ dosimeters and evaluated the radiation dose directly absorbed by operators when using different vascular accesses ( Table 2 ). The majority of these studies showed an increased operator radiation exposure with transradial compared to transfemoral access, although most data come from non randomized studies.
| Author (year) | Femoral ( n ) | Radial ( n ) | Design | Procedure | Right access (%) | DAP femoral | DAP radial | P | AK femoral | AK radial | P |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Shah (2013) | 870 | 240 | Retr | Cor | 85 | 50.19 | 60.40 | 0.003 | 670.3 | 805.4 | 0.02 |
| Shah (2013) | 512 | 74 | Retr | PCI | 89 | 153.95 | 196.49 | 0.02 | 2239 | 2795 | 0.03 |
| Delewi (2013) | 2950 | 6614 | Prosp | Cor | NA | 31 | 31 | 0.18 | NA | NA | – |
| Delewi (2013) | 2792 | 5056 | Prosp | PCI | NA | 79 | 73 | < 0.001 | NA | NA | – |
| Michael (2013) | 63 | 63 | Rand | Cor | 0 | NA | NA | – | ⁎ 1080 | ⁎ 1290 | 0.06 |
| Michael (2013) | 30 | 24 | Rand | PCI | 0 | NA | NA | – | ⁎ 1560 | ⁎ 1190 | 0.18 |
| Rigattieri (2013) | 243 | 1153 | Retr | Cor + PCI | 82 | 96.70 | 76.35 | 0.002 | NA | NA | – |
| Jolly (2013) | 2255 | Rand | Cor + PCI | NA | 51 | 53 | 0.828 | † 930 | † 1046 | 0.051 | |
| Lo (2012) Senior | 25 | 25 | Prosp | Cor | 100 | ⁎ 22.4 | ⁎ 21.7 | 0.74 | NA | NA | – |
| Lo (2012) Trainee | 25 | 25 | Prosp | Cor | 100 | ⁎ 25.2 | ⁎ 25.4 | 0.90 | NA | NA | – |
| Hibbert (2012) | 361 | 203 | Retr | Cor + PCI | NA | ⁎ 123.3 | 194.1 | < 0.001 | NA | NA | – |
| Mercuri (2011) | 4190 | 1764 | Prosp | Cor + PCI | NA | NA | NA | – | ¶ 6.28 | ¶ 6.49 | < 0.001 |
| Lehmann (2010) | 842 | 624 | Prosp | Cor + PCI | 100 | 13.38 | 15.76 | 0.149 | NA | NA | – |
| Brueck (2009) | 512 | 512 | Rand | Cor + PCI | NA | 38.2 | 41.9 | 0.034 | NA | NA | – |
| Achenbach (2008) | 155 | 152 | Rand | Cor + PCI | 92 | ⁎ 3.199 | ⁎ 3.737 | 0.13 | NA | NA | – |
| Lange (2006) | 103 | 92 | Rand | Cor | 100 | ⁎ 13.1 | ⁎ 15.1 | < 0.05 | NA | NA | – |
| Lange (2006) | 48 | 54 | Rand | PCI | 100 | ⁎ 51 | ⁎ 46.3 | NS | NA | NA | – |
| Sandborg (2004) | 40 | 36 | Prosp | Cor | NA | 33 | 45 | 0.0026 | NA | NA | – |
| Sandborg (2004) | 42 | 24 | Prosp | PCI | NA | 40 | 69 | 0.013 | NA | NA | – |
| Geijer (2004) | 114 | 55 | Posp | Cor + PCI | 98 | 54 | 51.9 | NS | NA | NA | – |
| Larrazet (2003) | 184 | 218 | Prosp | PCI | NA | 175 | 138 | < 0.001 | NA | NA | – |
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