Feasibility, safety, and diagnostic potential of endomyocardial micro-biopsies

Abstract

Endomyocardial biopsy (EMB) is considered a reference method for diagnosis of several cardiac diseases, but the method is limited by significant complication risks and relatively poor sensitivity. Although attempts have been made to improve the tissue analysis with modern molecular methods, the safety and accuracy issues of EMB sampling remain unaddressed. We hypothesized that the EMB device can be made significantly smaller and more flexible while retaining the ability to use molecular methods for analysis, such as RNA-sequencing. More specifically, the thesis was outlined to investigate whether it is technically feasible to create and use such a device (Paper I and IV) and evaluate outcomes in terms of diagnostic capabilities (Paper II) as well as safety (Paper III).

In Paper I, we invented a sub-millimeter endovascular biopsy device (micro-EMB) and developed a low-input RNA-sequencing protocol for analyzing small tissue samples. We evaluated the method in swine and showed that most biopsy attempts are successful (81 %), and that high quality RNA-sequencing data can be generated from the samples. In Paper II, we investigated whether the micro-EMB device can be used to detect gene expression changes in myocardial disease in swine. We showed that the method is capable of detecting a large number of responding genes in the first hours after myocardial infarction, but fewer at later timepoints. In Paper III, we compared acute complication frequencies between micro-EMB and EMB using a high-risk sampling approach in swine (n = 20). We found a significantly lower number of acute complications using micro-EMB compared to standard EMB. In Paper IV, we showed that micro-EMB samples can be handled in a regular operating room with simple tools. We also showed that microarray can be used on human cardiac micro-biopsy sized tissue, as an alternative to RNA-sequencing.

In conclusion, this thesis describes a novel, sub-millimeter EMB device (micro-EMB) which can be used to consistently collect myocardial samples. The work demonstrates the technical feasibility of constructing such a device, and that the obtained samples can be used to generate high-quality gene expression data by using RNA-sequencing or microarray. We also show that the method is capable of detecting gene expression changes in the swine heart. The method has improved flexibility and safety properties in the used animal models compared to current techniques. Future utility of the device depends on the development of a clinical grade device, diagnostic capabilities in relevant clinical scenarios, as well as extended safety trials.