Prospective Comparison of Palpation Versus Ultrasound-Guided Radial Access for Cardiac Catheterization

Abstract: Background. Radial access is increasingly used for both diagnostic and interventional cardiac procedures. Prospective data comparing ultrasound- versus palpation-guided radial catheterization are largely lacking. Methods. In this prospective, single-center study, a total of 183 consecutive patients scheduled for transradial cardiac catheterization by an experienced interventionalist were assigned 1:1 to either palpation- or ultrasound-guided radial access. Demographic and procedure parameters were prospectively recorded. Results. Baseline demographic and clinical parameters did not differ significantly between the ultrasound group (n = 92) and palpation group (n = 91). The initial radial catheterization success rate (87% vs 86.8%; P=.999) and time to access (47 seconds [interquartile range (IQR), 20-90 seconds] versus 31 seconds [IQR, 20-75 seconds]; P=.179) did not differ between the ultrasound and palpation groups, respectively. Pulse quality (absent, weak, strong) was independently associated with access failure in both groups (P<.001). Obesity was associated with access failure in the palpation group (P=.005), but not in the ultrasound group (P=.544). In 3/12 cases (25%) in the ultrasound group and 2/6 cases (33%) in the palpation group, the operator was able to establish radial access using the alternative method (P=.710). If palpation-guided radial access failed, an additional ultrasound-guided attempt before crossover to femoral access was associated with a shorter overall time to access (525 seconds [IQR, 462-567 seconds] versus 744 seconds [IQR, 722-788 seconds]; P=.016). Conclusions. Ultrasound-guided radial access seems to provide no substantial additional benefit over palpation-guided access alone. Attempting the alternative guiding methods to establish radial access before crossover to femoral access seems to be a reasonable approach.

J INVASIVE CARDIOL 2013;25(10):538-542

Key words: transradial, intravascular ultrasound, PCI

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Transradial access (TRA) has been increasingly adopted in the United States as a method for diagnostic and interventional cardiac catheterization. There are many reasons for this, but in particular, the decreased rate of access-site complications compared to femoral access as demonstrated by the recent RIVAL trial makes radial access attractive for interventionalists.¹ There have been studies concerning arterial lines that have suggested that the success rate on the first attempt is greater when ultrasound guidance is used, and that the time to access is generally shorter when using ultrasound guidance.^2-4 However, prospective data on whether ultrasound still provides any benefits over palpation alone to establish radial access for an experienced transradial cardiac interventionalist are lacking. The present prospective study was conducted to close this important gap in knowledge. 

Methods

This investigator-initiated, single-center, prospective trial was performed in the cardiology interventional suites of a tertiary-care center. Consecutive patients scheduled for emergency or elective cardiac catheterization or percutaneous coronary intervention via transradial access were enrolled and assigned 1:1 to either palpation- or ultrasound-guided radial access by an operator performing >200 transradial procedures per year. Failure to achieve transradial access by the primary method was either followed by use of the alternate method or crossover to femoral access at the discretion of the operator. Patients who had a history of unsuccessful transradial access, patients with a pathologic Allen test, cognitive impairment, and/or patients younger than 18 years were not eligible for enrollment. There were no other exclusion criteria. The study protocol was approved by the Institutional Review Board, and the need for patient consent for inclusion in the study was waived. Procedure-related information, including time to access (time between the start of radial palpation/ultrasound by the interventionalist and successful sheath introduction), radial pulse quality (no pulse, weak pulse, strong pulse) as assessed by an independent registered nurse, and complications (vessel dissections and access-site hematoma requiring medical attention) were collected using a dedicated datasheet. Baseline parameters, including patient medical history and medication, were collected using the prospective maintained National Cardiovascular Data Registry (NCDR) CathPCI registry as prespecified in the protocol and in accordance with Health Insurance Portability and Accountability Act (HIPAA) guidelines.

A micropuncture radial access kit including a 21-gauge single-wall introducer needle and 0.018˝, 60 cm Cope Mandril wire (both Cook Medical) and a 100 mm, 4-8 Fr, hydrophilic-coated introducer sheath (Glidesheath; Terumo Interventional Systems) was used. A Sonosite M-Turbo (SonoSite, Inc) with a linear 13-6 MHz transducer was used for the ultrasound-guided procedures. The access technique was at the discretion of the operator; however, in general, the radial artery was visualized in a transverse axis to guide single (front) wall puncture using the introducer needle. Upon blood return, the guidewire was advanced, and the needle exchanged for an introducer sheath in standard Seldinger technique. 

Statistical analysis. Demographic and clinical parameters were presented as mean ± standard deviation (SD) or median (interquartile range [IQR]), as appropriate. Comparisons between groups were made using a two-sided unpaired Student’s t-test, or non-parametric Mann-Whitney U-test or Chi-square test, as appropriate. The DuBois and DuBois equation was used to calculate the body surface area (BSA).⁵ A multivariate regression analysis was performed to determine independent parameters for procedure success. The level of significance was set at P<.05 (two-sided) for all analyses. Analyses were performed using SPSS version 20 software package (IBM Corporation).

Results

Between April and December 2011, a total of 202 consecutive patients scheduled for cardiac catheterization by TRA were enrolled. There were 19 cases in which inconsistencies in the 1:1 randomization protocol occurred (15 assigned to palpation, 4 assigned to ultrasound), and these cases were excluded from the analysis, as prespecified. No reason for the protocol violations were specified by the responsible operator and no specific pattern concerning these cases was observable. No differences in the main findings were observed in an “intention-to-treat” analysis including the 19 patients, and the presented values below refer to the 183 “per-protocol” patients.  Figure 1 displays the patient study flow chart. The baseline demographic and clinical parameters of the remaining 183 patients are summarized in Table 1. No significant differences between the palpation (n = 91) group and ultrasound group (n = 92) were observed with regard to medical history, cardiovascular risk factors, or body status. Procedure-specific data are presented in Table 2. In 159 patients (86.9%), the operator was able to establish radial access with the assigned method. No significant difference in the primary success rate or time to establish access was observed between the ultrasound and palpation group (P=.999 and P=.179, respectively.). Figure 2A displays the distribution of time needed to establish access according to the primary guiding method used. The median time needed to establish access was 42 seconds (IQR, 20-90 seconds); the operator was able to establish access within 1 minute in 65.4% of cases and within 2 minutes in 85.8% of cases. In 70.5% of the palpation-only cases and in 63.6% of the ultrasound cases, access was established within 1 minute and no overall difference between groups was detectable (P=.481). In 24 cases (13.1%), the operator was not able to establish radial access with the primary guiding method. The access failure rate did not differ between groups (13.0% [n = 12] in the ultrasound group vs 13.2% [n = 12] in the palpation group; P=.999).  

Primary access failure was similarly associated with the pulse quality in both groups, as displayed in Figure 3. In patients with absent pulse, the overall failure rate was 76.9% (3/13), compared to 27.8% (10/36) in patients with weak pulse and 3.0% (4/134) in patients with a strong pulse (P<.001 for between-group differences and trend). Radial access success was associated with obesity, with an observed failure rate of 5.1% in patients with BMI <25 vs 24.1% in patients with BMI >35 (P=.022). As demonstrated in Figure 4, obesity was significantly associated with access failure in the palpation group (0% in patients with BMI <25 vs 36.4% in patients with BMI >35; P=.005). In contrast, no significant association between obesity and access failure was observed in the ultrasound group (10% in patients with BMI <25 vs 16.7% in patients with BMI >35; P=.544). Multivariate regression analysis showed that only the pulse quality was independently associated with access success, in the total group as well as in the palpation or ultrasound group separately (Table 3).

In 6/24 patients (25%), the operator decided to obtain femoral access instead of further attempting radial access using the alternative guiding modality. All 6 patients were in the ultrasound group and the reasons for not attempting a palpation-guided radial approach were mainly due to the observation of an unsuitable radial artery (<2 mm, heavily calcified) during the primary approach. In the remaining 18 cases, radial access was successfully established using the alternative guiding method in 5 cases (27.8%). After palpation failed, the success rate with ultrasound was 25% (3/12 cases). Conversely, after ultrasound-guided access failed, the operator was able to establish access by palpation in 33.3% of cases (2/6 cases; P=.710 between groups). If the primary access attempt failed, the time needed to establish access increased significantly from a median of 42 seconds (IQR, 20-90 seconds) to a median of 583 seconds (IQR, 465-744 seconds; P<.001). Despite an absent pulse, the operator was able to establish radial access using ultrasound in 33% of the cases (3/9 patients) as opposed to 0% success rate using palpation only (0/4 patients; P=.188). Figure 2B displays the time needed to establish access after the primary attempt failed. In the palpation group, the median time needed to establish access increased from 31 seconds (IQR, 20-75 seconds) to 551 seconds (IQR, 424-740 seconds; P=.007) and in the ultrasound group from 47 seconds (IQR, 20-90 seconds) to 628 seconds (IQR, 478-744 seconds; P=.034). The median time to establish access when the operator chose to proceed directly with a femoral approach was longer compared to the time the operator needed if he first tried to gain radial access by palpation and proceeded with femoral access if palpation also failed (744 seconds [IQR, 722-788 seconds] versus 525 seconds [IQR, 462-567 seconds]; P=.016). No access-related complications (vessel dissection or clinically significant access-site bleeding) were observed.

Discussion

In this prospective, single-center study comparing ultrasound- versus palpation-guided radial access for cardiac catheterization performed by an experienced cardiac interventionalist in 183 patients, we report six main findings: (1) The success rate and (2) the time needed to establish radial access were similar between the ultrasound and palpation groups. (3) Pulse quality was independently associated with access failure in both groups. (4) Obesity was associated with access failure in the palpation group, but not in the ultrasound group. (5) If the initial method to gain radial access failed, an experienced operator was subsequently able to establish radial access using the alternative method in 25%-33% of cases. (6) If ultrasound-guided radial access failed, an additional palpation-guided attempt before crossover to femoral access was associated with a significantly shorter overall time to access.

The number of percutaneous diagnostic and interventional cardiac catheterizations has dramatically increased worldwide over the last decades. Traditionally, most centers use a transfemoral approach for vessel access, but in recent years, transradial access has become an accepted alternative approach. Radial access is believed to be technically more challenging than femoral access and a failure rate of up to 16% has been reported in inexperienced operators.^6,7 Ultrasound has been reported to be useful during the learning period in aiding operators to achieve adequate radial arterial puncture. A recent meta-analysis of four trials with a total of 311 subjects showed that ultrasound-guided radial access tended to be faster and was associated with a 71% higher first-attempt access success rate as compared to palpation-guided access only;⁴ some interventionalists may even see the lack of an ultrasound-equipped cardiac catheterization lab as a barrier to implementing radial access in everyday clinical practice. However, these studies were conducted in the critical care setting, and the catherization lab set-up with availability of different access equipment, as well as the experience of arterial access by an interventional cardiologist, are very different from a critical care set-up and critical care physician. In the present study, a high initial radial access success rate could be achieved by an experienced cardiac operator using ultrasound or palpation only to guide puncture (87.0% and 86.8%, respectively; P=.999 respectively). It is likely that an even higher overall radial approach success rate would have been achieved if an additional contralateral radial approach was also used; however, in this study, a direct switch to the femoral approach was used due to logistic reasons. Nevertheless, the observed overall rate of successful radial access (89.6%) is comparable to the reported radial success rate of 93.0% in 3479 patients of the RIVAL trial, a randomized, controlled, multicenter study that compared radial versus femoral access for percutaneous coronary intervention. Taking into account the learning curve, only experienced operators (defined as experience with >50 transradial interventions) were allowed to participate in the RIVAL trial, resulting in similar success rates, but a significantly lower rate of local vascular complications in the radial access group compared to femoral access (1.4% vs 3.7%, respectively; P<.0001).

Radial access, due to its lower rate of access-site complications, is especially attractive in severely obese patients.^8,9 It is noteworthy that palpation-guided radial access was most successful in normal-weight patients (BMI <25) and significantly lower in severely obese patients (BMI >35; P=.014), whereas the success rate was not significantly impaired by BMI in the ultrasound group (P=.653). However, in multivariate analysis, radial pulse quality (absent to strongly palpable) was the only independent predictor for access success, in the total group as well as in the groups separately. Interestingly, despite an absent pulse, the operator was still able to establish radial access using ultrasound in 33% of the cases (as opposed to 0% success rate using palpation only). This difference did not reach statistical significance, likely due to the limited case number in our study. Since we did not assess prospectively whether a previous transradial catherization had been performed, we also cannot draw any firm conclusion on whether ultrasound might have any advantage in these specific patient populations. Another limitation of our study is the fact that the classification of “no pulse, weak pulse and strong pulse” is arbitrary and might be influenced by many factors such as cardiac rhythm (sinus or atrial fibrillation) and/or systolic blood pressure. 

In a relatively small study in which 60 patients underwent radial artery cannulation, ultrasound guidance was found to significantly shorten the time to access compared to palpation (107 seconds vs 314 seconds; P=.0004),³ whereas the time difference was not significant in another study (n = 69; 56 seconds in the ultrasound group vs 112 seconds in the palpation group; P=.17),² perhaps reflecting the variation in operator experience across the studies. In the present study, the median time to establish radial access was shorter (42 seconds), likely reflecting the high level of operator experience. The median time needed to establish access was shorter in the palpation group (31 seconds) than in the ultrasound group (47 seconds), but the difference was not statistically significant and unlikely to be clinically relevant. However, the process of sterile preparation of the ultrasound probe is somewhat time consuming and was not included in our time measurement.  Nevertheless, it is our experience that in the cases where the initial attempt to establish radial access failed, ultrasound seems to be helpful for judging the general suitability of the radial artery (diameter, calcification) and for guiding the operator on the sheath size and whether to attempt another radial approach or to crossover directly to femoral access. Since the operator was able to establish radial access by the alternative method in 25%-33% of the cases in which the initial guiding modality failed (ultrasound when palpation failed and vice versa), it seems to be reasonable to first attempt radial access with both methods before crossing over to femoral access. In our study, this algorithm was also associated with a significantly shorter overall time to access and a crossover rate similar to the rate observed in RIVAL (10.4% vs 7.4%, respectively). 

Morbid obesity represents an increasingly prevalent challenge for interventionalists, and our results indicate that more research is needed to clarify whether ultrasound confers any benefits in this subpopulation (eg, increasing success rate and reducing complication rates). We did not observe local access-site complications in our study; therefore, our study does not have the power to draw firm conclusions on the effect of ultrasound on vascular complications in this or another subgroup. Nevertheless, the present study, though limited by its single-center design, is to date the largest prospective study comparing ultrasound versus palpation in the cardiac catheterization setting. As such, it provides evidence that an experienced operator can establish radial access in a high percentage of cases by palpation only, and that for an experienced operator, ultrasound may only confer additional benefits in selected cases in which initial palpation-guided access failed. Considering the fact that ultrasound equipment is expensive and not always available, our results indicate that palpation-guided interventions are reasonable in experienced operators. 

Conclusions

Ultrasound-guided radial access seems to provide no substantial additional benefit over palpation-guided access alone. However, although not reaching a statistically significant difference, our data indicate that in patients with an absent pulse, ultrasound might confer some advantage over palpation. If radial access with the initial guiding method failed, it seems to be reasonable to attempt radial access with the alternative guiding method before crossover to femoral access. 

References

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