1. Introduction

Percutaneous coronary intervention (PCI) is the recommended revascularization procedure for patients with acute coronary syndrome (ACS) [1]. Despite the advancements associated with the procedure, complications are known to occur and almost half of them are access site complications which can lead to prolonged hospital stay and increased mortality and morbidity [1]. CABG patients represent a subset of challenging coronary artery disease patients with multivessel disease, complex coronary anatomies [2], and high atherosclerotic disease burden in other arterial territories such as iliac and femoral arteries [3]. They tend to be older and have multiple comorbid conditions [4].

Minimizing the procedural risks while adequately cannulating the grafts remains a challenge [2]. For diagnostic angiography in general, transradial access (TRA) has increasingly become a more popular method than TFA and carries several advantages including faster mobilization [5], reduced access site bleeding complications [6], and greater patient comfort [7]. Nonetheless, TRA does come with some degree of risk including radial artery occlusion (RAO), increased radiation exposure [8], and, rarely, osteofascial compartment syndrome of the forearm [6]. Additionally, in patients with prior CABG, radial access is sometimes made more challenging due to the presence of IMA grafts, gastroepiploic artery grafts, and incidences where the radial artery had been harvested as a conduit [9].

After CABG, many patients require subsequent coronary angiograms, and TFA has traditionally been the most commonly used access site in cannulation in these patients [10]. Unfortunately, most studies comparing radial and femoral approaches excluded CABG patients and therefore limited studies are available regarding the ideal access site [2].

First introduced by Kiemeneij [10] in 2017, LdTRA, has increasingly been used for arterial access in PCI. This technique involves accessing the distal radial artery in the anatomical snuffbox of the hand [10]. It is a much more feasible approach in patients with prior CABG involving left inframammary artery (LIMA) grafts [11] and more ergonomic for both the operator and the patient as it requires the hand to remain pronated during the procedure [12] and spares the superficial palmar branch thus reducing the risk of RAO and compartment syndrome of forearm [13]. To the best of our knowledge, this is the first retrospective study addressing the simultaneous comparison of LdTRA, TRA, and TFA in post-CABG patients undergoing coronary angiography..

2. Methods

We retrospectively studied 417 patients with prior CABG who were undergoing coronary angiography at our institution’s cardiac catheterization lab between January 2018 and August 2020, to compare the type of intervention using the site of access as an independent factor. The study took place in consideration of ethical principles for medical research involving human subjects. No recruitment was needed as there was no intervention involved. The procedures were performed by board certified interventional cardiologists who were skilled in radial access. There was no consent taken as this was a retrospective chart review. Data collection was performed through chart review. Patients with no prior history of CABG were excluded from the study. The following information was obtained: Patient demographics (age, gender, BMI, smoking), pre-existing medical conditions (diabetes, hyperlipidemia, COPD, hypertension, CKD), family history of ischemic heart disease (IHD), prior PCI, prior history of heart failure, prior history of myocardial infarction (MI), information on catheterization procedure (eg time to gain access, access site, procedure duration, fluoroscopy dose and fluoroscopy time) and length of hospital stay.

These parameters were examined in three groups of patients who have had coronary angiography +- intervention; the first group who had their angiography access via the TFA to those with TRA versus those who had their access via LdTRA. We screened patients' charts using Xper IM. Analyses were performed by Statistical Product and Services Solution using the Chi-Square test and Pearson's correlation for categorical data and ANOVA test for nominal data. All the analyses were done using an alpha (α) level of <0.05. Pre-defined endpoints were time to access, procedure duration, fluoroscopy time, and dose and length of hospital stay. Mortality was not observed among the three groups.

3. Results

650 patients were screened from the hospital database using Prior CABG as screening criteria. (ICD 10 Codes: Z95.1). After an initial screening to include patients who had their right radial artery used as a graft during CABG, 398 patients were found eligible for study participation as shown in flow diagram.

Figure 1: Study Flow Diagram showing total and final number of patients in retrospective analysis after application of exclusion criteria

Based upon whether LdTRA, right TRA or femoral artery was used for vascular access, patients were classified into three groups. Out of the total sample size of 398 patients, 324 patients underwent coronary angiography using femoral approach, 28 patients had LdTRA and about 46 patients had right TRA. Out of 398 patients, 78.4% were identified as males and 21.6% were identified as females. The mean age was 71.6 years. 14.3% were smokers, 97.5% had hypertension, 50.5% had diabetes, 98.0% had hyperlipidemia, 35.2% had a family history of Ischemic heart disease, 52.3% had a prior myocardial infarction, and 27.6% had a history of prior heart failure. The distribution of the type of approach used during PCI using demographic characters was as follows:

Table1 A:

Table 1 B:

Table 1: A: Distribution of total sample size with respect to type of access,

B: showing distribution of demographic risk factors in all three subgroups of arterial access

Considering BMI as a risk factor for ease of access, patients were classified based on BMI into further subgroups as

1. Group 1: BMI = <18.5
2. Group 2: BMI= 5-24.9
3. Group 3: BMI= 0-29.9
4. Group 4: BMI= 0-34.9
5. Group 5: BMI= 0-39.9
6. Group6: BMI= >40.0

Table 2: Distributions of BMI in the subgroups based on type of access

Time of access, time of procedure, fluoroscopy time, fluoroscopy dose, length of post-procedural stay were the parameters used to judge the clinical difference between the approaches used. The results are as follows: The mean time for femoral access was 37.68±1.19 seconds (95% CI 35.3295-40.04), for snuffbox access 36.4±5.06 seconds (95% CI=26.03-46.81), and for proximal radial access 40.71±4.17 seconds (95% CI=31.21-50.20).Mean procedural time via femoral access was 37.68±1.97 minutes, via snuffbox access was 36.43±5.06 minutes, and via radial access was 40.71±4.17 minutes. Mean length of stay for femoral access was 1.97±0.14 days, for radial access 2.13±0.31 days and for snuffbox access 1.68±0.27 days. The fluoroscopy time for femoral access was 10.23±0.41 minutes, for snuffbox access was 11.28±2.00 minutes and for radial access was 13.23±1.74 minutes. The fluoroscopy dose for femoral access was 599.98±26.63 Gy/cm2, for snuffbox approach 722.71±112.94 Gy/cm2 and for radial access was 767.06±90.89 Gy/cm2. There were no complications noted in our study. We found no statistical significance difference between approaches with regards to time of access, procedure duration, fluoroscopy time and dose.

Table 3: showing the relationship between different measured parameters with reference to type of access

Table 4: showing the results of Chi- square test to identify statistical significance of difference between the choice of site for access and the demographic risk factors

The Chi Square Test shows that there is a significant difference between choice of site of access and Age and smoking status (p <0.05). ANOVA test was run using Site of access, categorical age, categorical BMI and smoking as independent factor and procedural time, time of access, length of Hospital stay, fluoroscopy time and fluoroscopy dose as dependent factors. One way ANOVA revealed that there was a statistical significant difference in fluoroscopy dose between at least two groups based on BMI. (F(5,392)=[12.153], p<0.001). Similarly, there was a statistically significant difference in the time of access in patients grouped based on smoking (F(1,396)=[6.795], p=0.009).

Figure 1: Bar chart showing the relationship between access time, procedure time and fluoroscopic time in all three approaches

Student-Newman-Keuls Post-Hoc Analysis was conducted to see the statistically significant difference between subgroups. Post Hoc Analysis could not be carried out for the relationship of smoking and time of access. However, Post Hoc Analysis showed that the mean dose of fluoroscopy significantly varies between patients with BMI <30 and those with >30. All the analysis were done using alpha (α) level of <0.05. Based on the findings as stated above, our study did not find any statistical significant difference the choice of site of access, the demographic factors, time of access, procedural time, fluoroscopy time, fluoroscopy dose and length of Hospital stay, except for a significant increased fluoroscopy dose in patients with BMI >30. Therefore, the null hypothesis holds stating that there is no difference in outcome of patient regardless of site of access use.

4. Discussion

Radial access remains the most preferred way of coronary angiography by operators today [14]. Multiple studies, including randomized trials that compared TRA with TFA have shown that TRA is associated with greater patient satisfaction, reduced bleeding and vascular complications [15], reduced morbidity and mortality [16-19], and cost reductions [20].

However, although infrequent, TRA is associated with some known complications such as asymptomatic and symptomatic RAO, perforation, spasm, nonocclusive injury, pseudoaneurysm and arteriovenous fistulae [21-22]. These complications may prevent future utilization of the radial artery, including use as the grafting vessel in coronary artery bypass graft (CABG), repeat access for staged or repeat PCI and establishing arteriovenous fistulae in chronic renal dysfunction [23]. The right TRA is more commonly used as compared to the left TRA, because performing catheterization through the left TRA approach is ergonomically challenging for operators, especially in cases of obese patients and short operators [6]. In patients whom the left radial is chosen (e.g. right radial tortuosity, spasm or occlusion and in the left internal mammary angiography graft), these technicalities may be overcome by using the left distal transradial approach (LdTRA), otherwise called the anatomical snuffbox approach [23, 24]. First introduced in 2017 by Kiemencij [10], this approach was found to be more convenient for both parties involved because patients can keep their left hand pronated near their right groin, which allows the operator to cannulate the artery at the snuffbox without reaching across the patient [12]. The risk of complications was also lower with LdTRA as it spares the palmar branch that supplies the deep palmar arch, reducing ischemic hand events and also facilitates early hemostasis [6].

The patients with prior history of CABG undergoing PCI are traditionally approached using the femoral artery and are often excluded from the studies comparing the TFA and TRA [2]. In this subgroup of prior CABG, several factors have to be taken into account such as graft anatomy, graft degeneration, long standing atherosclerosis and diffusely diseased aortic wall [2]. The novel LdTRA has proven to have a better safety profile and higher satisfaction in recent years [4]. This is mainly due to shortened compression time, better hemostasis and lower incidence of RAO and spasm [4,13]. It was previously thought that LdTRA was associated with increased rate of cannulation failure and increased time of access when compared to TRA [25]. However, recent studies and meta-analysis have shown no difference in access success rate and puncture time between TRA and LdTRA approaches when performed by experienced operators [6].

Our study population was heterogeneous with mostly elderly patients with a mean age of 71.6 years. We also had a large number of patients with hypertension (97.5%), almost fifty percent had diabetes and 25% receiving hemodialysis. In end stage renal disease patients on hemodialysis, operators may prefer to use distal transradial access, as it will preserve the proximal artery for a future arteriovenous fistula [26]. Almost 35 % of patients were overweight (BMI 25-29) and almost thirty percent of patients were obese (BMI >/= 30). Central obesity may preclude the patient from being able to place their left arm across their lower abdomen in position for the operator to cannulate the artery [27]. Advancing the wire at the point of the elbow can be troublesome especially when patients are obese and must bend their elbow to place their hand at their right groin [27]. Additionally, using post hoc analysis, the mean dose of fluoroscopy significantly varies between patients with BMI <30 and those with >30 and it showed significantly increased fluoroscopy doses in patients with BMI >30.

The main results of our study did not show any statistically significant difference between the three approaches for invasive coronary procedures in terms of set endpoints. Ghose T et al reported that with LdTRA, there was a statistically significant increased mean procedure time, mean fluoroscopic time and similar fluoroscopic dose compared with TRA [28]. With regards to radiation exposure, the LdTRA approach places the operator farther away from the radiation source as the patient's hand is placed at the right groin, which may reduce radiation exposure to the operator [29]. Our study did not show any statistically significant difference between all three accesses for the aforementioned outcomes. A possible explanation for this difference could be due to the experience of the operators or the fact that our study had fewer participants. Similar to our retrospective study, Stefano et al reported in their meta-analysis that, in patients with previous CABG undergoing coronary procedures, TRA is associated with similar procedural and fluoroscopy times compared with TFA [11]. Several observational studies comparing TRA with TFA showed there are reduced complications with the transradial approach [30]. Data from the triangle registry [31] showed that there was a longer puncture time and a longer fluoroscopic time in LdTRA compared with rdRA (right distal radial access). The registry used no randomization or control group [31].

Coughlan ct. al [27] found that LdTRA could shorten length of stay for patients from a post-procedural standpoint. This was secondary to shortened post procedural radial compression time as compared with TRA. Our study in comparison with LdTRA, TRA and TFA did not show any difference between length of hospital stay. At this time there are no studies in the literature comparing LdTRA with conventional access methods in patients with prior CABG. Considering that most patients with CABG have in-situ left internal mammary artery (IMA) grafts and a variable number of aortocoronary saphenous vein grafts, LdTRA would probably be most appropriate given the ergonomic benefit to the operator, particularly in what can be a longer procedure in which several grafts need to be cannulated.

5. Study Limitation:

Our study is limited by a relatively small study sample, single-center experience with two operators performing the vast majority of the distal radial cases, and the retrospective nature of the analysis.  To best answer the question of which access site is best for patients with prior CABG undergoing coronary angiography, a randomized trial would be needed.

6. Conclusion:

Due to the lack of statistical significance between outcomes of either approach, all approaches remain reasonable access options in post-CABG patients. Clinically, the left distal radial approach may be superior and is recommended by the authors of this study because it avoids the risks of femoral access complications in these complex patients, allows an easy approach to the LIMA graft, and is more ergonomic for the operator than left proximal radial access.

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