## 2 Literature Search Methods  
We perform a narrative review to highlight validation gaps in electrocardiographic R-peak detection. Information on validation studies of R-peak detection algorithms and recognized databases was analyzed to identify discrepancies by examining commonalities and differences among the included studies. The review highlights discrepancies, key conclusions, and future prospects.  
The scientific literature search was performed using several databases (Scopus, Web of Science). Specific terms such as ECG R-peak detection, ECG validation techniques, MIT-BIH arrhythmia, WFDB tools, ECG window size, ECG window tolerance, false positive ECG, false negative ECG, ECG statistics, and ECG validation tools were used in the search query. The search was not restricted by a particular time period but was limited to English-language articles. To determine if a study met the inclusion criteria for this review, two reviewers independently screened each record, and a third reviewer double-checked the results for accuracy and fairness. No automation tools were used in the screening process.  
The search provides a substantial number of peer-reviewed research articles and conference papers relevant to R-peak detection validation. After removing duplicates and excluding papers that did not meet the eligibility criteria, the remaining articles were further processed. Each study was analyzed for R-peak validation method, beat numbers, testing format, window size, and statistical metrics, and the findings were tabulated to ensure key aspects of ECG validation methods were addressed. The gathered information was then classified from different perspectives: adopted validation methodologies (custom methods),  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Literature**} & **R-Peak** & **MIT-BIH** & **Testing Format** & **Window** & \multicolumn{4}{c}{**Statistical Metrics**} \\ \cline{3-8}  & **Validation** & **Beats** & & **Size (ms)** & **FP** & **FN** & **Se (\%)** & **+P (\%)** \\ \hline [PERSON] et al. [57] & NG & 109,985 & Entire Record & NG & NG & NG & 97.93 & 98.84 \\ [PERSON] et al. [58] & NG & 109,966 & Entire Record & NG & 728 & 870 & 99.21 & 99.34 \\ [PERSON] et al. [59] & NG & 19,098 & Selective Records & NG & 40 & 76 & 99.66 & 99.55 \\ [PERSON] et al. [60] & NG & 45,936 & PVC, BBB & NG & 17 & 54 & 99.98 & 99.96 \\ [PERSON] et al. [61] & NG & 109,452 & Segment & NG & 127 & 138 & 99.87 & 99.88 \\ [PERSON] et al. [62] & NG & 109,949 & Entire Record & NG & 289 & 502 & 99.54 & 99.73 \\ [PERSON] et al. [63] & NG & 109,441 & Segment & NG & 122 & 46 & 99.97 & 99.93 \\ [PERSON] et al. [64] & NG & 109,494 & Entire Record & NG & 108 & 137 & 99.87 & 99.99 \\ [PERSON] et al. [65] & NG & 109,494 & Entire Record & NG & 104 & 126 & 99.89 & 99.91 \\ [PERSON] et al. [66] & NG & 109,494 & Entire Record & NG & 70 & 52 & 99.95 & 99.94 \\ [PERSON] et al. [67] & NG & 109,267 & Selective & NG & 248 & 340 & 99.68 & 99.77 \\ [PERSON] et al. [68] & NG & 109,510 & Entire Record & NG & 204 & 213 & 99.81 & 99.80 \\ [PERSON] et al. [69] & NG & 108,494 & Selective & NG & 97 & 171 & 99.84 & 99.91 \\ [PERSON] et al. [70] & NG & 109,491 & Entire Record & NG & 574 & 160 & 99.85 & 99.85 \\ \hline \hline \end{tabular} This table examines the details of ECG testing in the literature, considering which R-peak validation tool was utilized for ECG testing. It also explores testing formats, whether all records were tested collectively or individually with sample exclusion, adherence to the AAMI standard for window size if applied, and the statistical metrics. It also shows the variation in the reported number of total beats for the MIT-BIH arrhythmia dataset. BBB = Bundle block branch beat, NG = Not given in the literature, PVC = Premature ventricular contraction.  
\end{table}
Table 1: _Cont._use of WFDB tools to validate R-peaks, mention of window size parameters, numeric discrepancies in beat reporting, and methodologies that reported only validation metrics.