The development of endomyocardial biopsy in the 1960s facilitated percutaneous sampling of the myocardium without the need for a grossly invasive procedure.1 However, in recent decades, significant advances in both invasive and non-invasive cardiac imaging have enabled the study of a wide array of cardiac diseases, without the need for a histopathological analysis of the heart. As a result, enthusiasm for myocardial biopsy has waned. Indeed, the most recent recommendations regarding endomyocardial biopsy date back to 2007, and a high level of recommendation applies in only a handful of settings.2 However, these guidelines base their recommendations on efficacy and safety data in existence at that time. Since then, two main changes have occurred: Firstly, several authors have published extensive data on an approach via the left ventricle rather than just the right ventricle, allowing for more extended myocardial sampling.3,4 Secondly, several operators started performing left ventricular (LV) biopsy using the radial approach, widely popular in the interventional community for its simplicity, comfort and increased safety.5 As a result, more recent documents call for a wider use of this technique, particularly in myocarditis,6,7 dilated cardiomyopathy8 and myocardial infarction with non-obstructive coronary artery disease.9

In this paper, we report our initial experience of the feasibility, safety and usefulness of transradial endomyocardial biopsy.

In our initial experience, transradial endomyocardial biopsy achieved excellent results, both regarding procedural success and complications. Our research is supported by an increasing amount of published data on this particular approach to endomyocardial biopsy.

Safety is the major concern when performing this technique, as many patients are often young (especially in the setting of myocarditis) and others have large ventricles with thin walls. We did not encounter safety issues, especially perforation, embolization or mitral regurgitation. This was likely the result of specific operator training both in radial intervention and LV biopsy, as well as technical safety precautions. We highlight the use of pressure monitoring, extensive back bleed and catheter aspiration, as well as peri and intra-procedural echocardiography guidance. All of these enable constant monitoring of the procedure and minimize risks.

As mentioned above, current guidelines regarding endomyocardial biopsy are now over a decade old and base their safety considerations on even older data.2 Indeed, these recommendations highlight a large series of transvenous RV biopsies with an overall 6% complication rate, a 1.2% possible or definite perforation rate and 0.4% death rate.14 Over the past decade, however, several authors from experienced European centers have published more extensive experience (ranging from 755 to 4221 procedures) totaling more than 8000 procedures.3,4,15 In addition, two of these publications provide extensive data on both left and RV biopsy, thereby providing clearer data.3,4 Overall, the published major and minor complication rate of these authors ranges from 0.12% to 0.82% and 1.35 to 5.2%, respectively, regarding RV biopsies.3,4,15 The rate of LV biopsy major and minor complications in LV biopsies was 0.33 to 0.64% and 2.2% to 2.89%, respectively.3,4 Importantly, there were no deaths in any of these series. Most major complications were perforation with subsequent tamponade. A very small number were cases of embolization. Several minor complications included bleeding or vascular-related.

These data provide valuable insights into safety. Firstly, the risk of the procedure when performed in experienced centers is low, and seemingly lower than previously published studies; secondly, LV biopsy seems at least as safe, if not safer, than RV biopsy.

Published transradial endomyocardial biopsy experience is quite recent. The earliest publications date back to 201412 and 2015.10,11 The largest series published to date was multicenter data comprising over 100 patients.13 In all of these recent case series, there were no major complications. Furthermore, the latter group published the largest radial versus femoral case series comparing both approaches, with 129 cases via radial and 134 cases via femoral access. There were no major complications and bleeding occurred exclusively in the transfemoral group.16

Our experience thus reflects the findings in contemporary data. Endomyocardial biopsy is a largely safe technique, all the more so when performed via the left ventricle, especially with the added safety benefits of the transradial approach.

In the series presented herein, the feasibility rate was 100%, with no cross-overs and only mild radial spasm observed in two patients. This was likely the result of patient selection, spasm prophylaxis administration, the use of hydrophilic catheters and the use of large size intra-luminal sheathless catheters, which allow for comfortable bioptome passage and have a reduced external caliper. Importantly, patient feedback was very positive and one patient, who had previously undergone a transjugular RV biopsy at another institution, actively voiced his preference for the transradial technique, because of improved comfort. When the procedure is performed electively, and if no complications occur, same-day discharge is possible. Our results are similar to previously published data. In fact, in the largest series published to date, cross-over to the femoral technique was required in only one patient (0.98%).13

The last issue regarding this technique is its diagnostic yield and clinical usefulness. In our experience, in which LV biopsy was always performed outside the setting of transplant, the results were clinically meaningful, as they added to the clinical question at hand. Indeed, the suspected diagnosis was either confirmed or ruled out, such as in the setting of myocarditis. Additionally, a doubtful diagnosis was clarified, such as the etiology of a cardiomyopathy, or amyloidosis infiltration and/or type in cases with predominant heart involvement and previously inconclusive studies. Finally, atypical forms of LV hypertrophy (i.e. apical) were observed in patients with ATTR, and tissue biopsy was most useful for confirming amyloidosis and ruling out hypertrophy.

Importantly, our pathologist's feedback was also very positive, as the quality and size of the samples was deemed excellent and better than when we had previously used the RV approach.

The abovementioned papers from the transfemoral era suggest that the LV approach is superior to the RV approach outside the transplant setting. Indeed, in the setting of myocarditis, the largest published series reports a 92.1% vs. 81.3% diagnostic yield,4 and in the setting of predominant LV disease, the difference is quite large and the LV approach is favored with 97.8% vs. 53%, respectively.3 Published data from the transradial approach do not allow for a comparison of left versus right approaches, however the conclusions are similar to ours: the results added to the clinical dilemma, confirming, excluding or clarifying a diagnostic hypothesis.13

Despite its advantages, the transradial LV endomyocardial biopsy technique is not without limitations. This approach requires the use of heparin, which may add to the risk of bleeding. In cases in which repeated biopsy is required, such as transplant patients, radial patency and the risk of vascular complications may become an issue with frequent procedures. In addition, the LV approach, while apparently less prone to perforation, regardless of the access site, may lead to a more dangerous scenario should perforation occur, given the much higher intracavitary pressure of the left ventricle. Also, the risk of cerebral embolization is essentially a concern of the left, rather than the right, approach, and thus it cannot be performed in the presence of LV intracavitary masses.

It is also important to point out the particular limitations of this paper. This an observational single-center study. Additionally, the sample size is relatively small given the single-center nature of the data. And finally, an ultrasound study of the radial artery was not performed after the procedure. Thus, although there was no clinical evidence of radial patency complications, these cannot be completely ruled out.

Transradial LV endomyocardial biopsy provides a safe and feasible method of sampling the myocardium for histopathological analysis, with a good diagnostic yield and clinically meaningful results in properly selected patients. This technique should probably be the default method for endomyocardial biopsy in patients undergoing a single biopsy procedure outside the setting of cardiac transplant in a radial center.

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  What is known about the topic?

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  The indications for endomyocardial biopsy are still debated, partly because of safety concerns and doubts about the clinical usefulness of the results;

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  Recent papers suggest the safety of LV biopsy is superior to RV biopsy;

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  Very recent data suggest that the transradial approach is a new and better method of sampling the left ventricle when compared to the transfemoral approach.

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  What does this study add?

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  Additional data confirming that transradial LV biopsy is feasible and safe;

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  Clinical data explaining how the results were useful in a variety of clinical scenarios;

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  Data to support the growing indications for endomyocardial biopsy.

The authors have no conflicts of interest to declare.