Detecting subtle myocardial injury after percutaneous coronary intervention: Insights from electrocardiography and heart rate variability analysis

Abstract

Percutaneous coronary intervention (PCI) remains one of the most effective therapies for coronary artery disease, yet even technically successful procedures can place short-lived or mild stress on the myocardium. In routine practice, this early myocardial stress often goes unnoticed because standard 12-lead electrocardiography (ECG) and peri-procedural biomarkers are not well suited to detect small, transient, or patchy injury. In a recent observational study by Chaikovsky et al, published in World Journal of Cardiology, explored whether a more detailed ECG-based analysis could uncover these subtle changes. By integrating more than 240 ECG and heart rate variability parameters into composite indices, they identified distinct physiological response patterns in a small cohort of patients undergoing PCI. One subgroup demonstrated post-procedural changes suggestive of mild myocardial injury, including altered ventricular repolarization, increased electrical instability, and reduced autonomic balance – findings that were not captured by conventional ECG interpretation systems. These observations are preliminary and hypothesis-generating, but they highlight the potential of advanced ECG-heart rate variability analytics as a sensitive, noninvasive approach to assessing early myocardial stress after PCI. Larger prospective studies, with correlation to biomarkers, imaging, and clinical outcomes, are needed before such tools can be considered for routine clinical use.

Key Words: Percutaneous coronary intervention; Myocardial injury; Troponin; Electrocardiography; Heart rate variability; Composite electrocardiography-heart rate variability analysis; Subclinical ischemia; Post-percutaneous coronary intervention monitoring; Signal processing; Micro-infarction detection

Core Tip: Subtle myocardial stress after percutaneous coronary intervention is common but frequently undetected by routine electrocardiography (ECG) interpretation or selective biomarker testing. A composite ECG-heart rate variability analytical approach has been proposed to capture small electrical and autonomic changes shortly after coronary intervention. Although early and exploratory, this strategy illustrates how more nuanced ECG analysis may complement existing tools and improve post-percutaneous coronary intervention risk assessment once validated.

This editorial refers to "Mild myocardial injury during percutaneous coronary intervention based on minor changes on electrocardiogram and heart rate variability" by Chaikovsky et al, 2025; https://dx.doi.org/10.4330/wjc.v17.i12.112141.

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INTRODUCTION

Percutaneous coronary intervention (PCI) has fundamentally changed the treatment of coronary artery disease, restoring coronary perfusion in both acute and elective settings. Despite its success, PCI is not entirely benign[1,2]. Mechanical manipulation of the coronary arteries, distal embolization, and brief episodes of ischemia can result in mild myocardial injury, even when angiographic results appear optimal[3]. Prior studies suggest that up to one-third of patients may experience some degree of myocardial injury during PCI, most often reflected by small elevations in cardiac biomarkers[3]. Cardiac troponins and creatine kinase-MB are highly sensitive indicators of myocardial necrosis, yet their role after PCI remains debated. Minor troponin elevations are common; their prognostic relevance varies by clinical context, and interpretation can be particularly challenging in patients presenting with acute coronary syndromes[3-5]. As a result, routine post-PCI biomarker testing is not universally performed, and small procedural injuries may go unrecognized[3].

Standard 12-lead electrocardiography (ECG) interpretation faces similar limitations[6-8]. Overt ischemic changes, such as new Q waves or significant ST-segment shifts, are uncommon after PCI and typically indicate larger areas of myocardial damage[9-11]. Advanced imaging techniques, especially cardiac magnetic resonance imaging with late gadolinium enhancement, have demonstrated that even modest biomarker rises can correspond to irreversible micro-infarction[12,13]. However, the cost and logistical demands of routine post-PCI imaging limit its widespread use[14-16].

Together, these challenges create a diagnostic gray zone between procedural success and overt myocardial injury. The study by Chaikovsky et al[17] seeks to address this gap by applying advanced ECG and heart rate variability (HRV) analysis to detect subtle physiological changes early after PCI. This editorial discusses the potential implications of that approach while emphasizing its exploratory nature and current limitations.

In this context, the report by Chaikovsky et al[17] published in World Journal of Cardiology is noteworthy because it attempts to extract clinically meaningful ‘micro-injury’ signals from short peri-procedural ECG recordings by analyzing 240 ECG-derived parameters and clustering post-PCI response patterns. We argue that the key contribution is conceptual, demonstrating that coordinated, small-amplitude electrical and autonomic shifts may be detectable when conventional ECG reads as normal, but that the current evidence base is insufficient to justify clinical decision-making without external validation and transparent interpretability.

A COMPOSITE ECG-HRV APPROACH: CONCEPT AND METHODOLOGICAL CONTEXT

Chaikovsky et al[17] applied a multiparametric framework that combines 240 ECG-derived and HRV-derived features into composite indices reflecting myocardial electrical behavior, autonomic regulation, and arrhythmic activity. In their observational study, brief ECG recordings were obtained immediately before PCI and again within hours after the procedure. Individual parameters, including waveform amplitudes, interval durations, and frequency-domain HRV measures, were normalized against reference values and integrated into hierarchical composite scores.

The underlying premise of this approach is straightforward: While a single ECG or HRV variable may change only slightly, coordinated shifts across many parameters may collectively signal meaningful myocardial stress. Using cluster analysis in a cohort of 23 patients, the investigators identified three distinct post-PCI response patterns. One subgroup demonstrated deterioration in composite indices after PCI, another showed improvement consistent with relief of ischemia, and a third exhibited minimal physiological change.

Notably, patients in the deterioration subgroup also showed widening of the frontal QRS-T angle, reductions in T-wave amplitude in select leads, increased arrhythmic indicators, and reduced HRV suggestive of autonomic imbalance. These findings are physiologically plausible markers of myocardial stress, yet they were not detected by standard ECG interpretation algorithms. Given the small sample size and limited follow-up, these results should be interpreted cautiously and viewed as hypothesis-generating rather than confirmatory.

Several features strengthen the signal that this approach is worth testing further: The authors analyze paired recordings before and several hours after PCI, interrogate a broad feature set (240 primary/computed ECG parameters), and identify three response clusters using K-means with cross-validation. At the same time, the study’s analytical degrees of freedom are large relative to the sample (n = 23), and HRV/repolarization metrics are vulnerable to peri-procedural confounding (analgosedation, pain, anxiety, respiratory pattern, medications, and acute coronary syndrome physiology). Most importantly, the composite indices are not yet anchored to an external reference standard (e.g., hs-troponin deltas, cardiac magnetic resonance imaging micro-infarction, arrhythmia endpoints, or longer-term clinical events), leaving open whether these clusters represent injury, recovery from ischemia, or non-specific autonomic perturbation.

CLINICAL IMPLICATIONS: PROMISE BALANCED BY CAUTION

Periprocedural myocardial injury is clinically consequential because even small injuries may signal downstream risk, yet existing post-PCI surveillance often misses transient or patchy abnormalities[18-20]. The potential value of the Chaikovsky et al[17] approach is not that it creates a new diagnosis on its own, but that it may offer an earlier and more graded physiological signal that could be tested as part of a risk-stratification strategy.

To place these findings into a practical clinical context, the key potential applications and current limitations of composite ECG-HRV analysis after PCI are summarized in Table 1.

Table 1 Electrocardiography-heart rate variability composite analytics for detecting subtle post-percutaneous coronary intervention myocardial injury.

Appraisal domain	What the focal study did	Editorial value and promise	Key limitations/critical comments	What would strengthen the evidence next
Clinical question	Sought to detect subtle peri-procedural myocardial injury not captured by routine ECG reads	Targets a real “gray zone” in post-PCI assessment	“Injury” vs non-specific stress cannot be assumed without external anchors	Pre-specify injury definitions; relate signals to accepted injury criteria and adjudicated events
Data acquisition	Paired short ECG recordings before and several hours after PCI	Practical and scalable if standardized	Short recordings can be sensitive to sedation, pain, respiration, posture, and acute coronary syndrome physiology	Protocolize recording conditions; document medications/sedation timing; replicate across centers
Feature space	Analyzed approximately 240 ECG-derived parameters (with HRV features integrated)	High-dimensional approach may detect weak coordinated changes	High degrees of freedom relative to n risks instability; interpretability can be opaque	External validation; reduce to parsimonious, interpretable feature set with prespecified thresholds
Pattern discovery	Identified three response clusters using K-means with cross-validation	Suggests heterogeneity in early physiological response to PCI	Clusters may reflect mixed constructs (ischemia relief vs injury vs autonomic perturbation)	Test reproducibility of clusters; assess calibration; compare to alternative clustering/classification strategies
Reference standards	Primarily ECG/HRV-derived indices	Demonstrates a signal-detection concept	Lacks direct linkage to hs-troponin deltas, magnetic resonance imaging micro-infarction, and clinically meaningful endpoints	Correlate indices with troponin kinetics, imaging, arrhythmia monitoring, and outcomes
Clinical implications	Hypothesizes that “worsening” patterns could mark higher-risk patients	May eventually support stratified follow-up	Clinical actionability is premature; risk of over-triage and anxiety	Prospective studies testing whether acting on the signal improves outcomes and is cost-effective
Generalizability	Single-center, small cohort	Useful as hypothesis generation	Unknown performance across PCI indications, comorbidities, devices, and workflows	-

ECG: Electrocardiography; HRV: Heart rate variability; PCI: Percutaneous coronary intervention.

Closer monitoring after PCI

If a patient shows an abnormal ECG/HRV pattern, like those in the high-risk cluster, it may be a sign they need a bit more attention after the procedure. For example, if the system picks up signs of higher arrhythmia risk or stress on the heart, the care team could keep them on telemetry a little longer, watch more closely for rhythm issues, or make sure pain and anxiety are well controlled to avoid extra strain on the heart. In simple terms, this acts like an early-warning system. It helps us notice patients who might look fine on the surface but aren’t as stable underneath. As Chaikovsky et al[17] highlight, these advanced measures can give us a helpful heads-up before a small problem turns into a serious one.

Tailored treatment after PCI

If we know a patient has even a small amount of heart muscle injury, it can change how we care for them. For example, we might strengthen their heart-protective medications, like making sure they’re on the right dose of statins, angiotensin-converting enzyme inhibitors, or beta-blockers, to help prevent any long-term effects of the injury. If their HRV shows a lot of stress, we might focus on calming the autonomic system with relaxation techniques or adjusting medications. In other words, this information lets us personalize care instead of using the same plan for everyone. As the study’s authors point out, spotting this vulnerable group gives us a chance to tailor monitoring and treatment. Patients showing signs of injury could get closer follow-up, while those whose numbers are improving could safely follow the usual recovery path.

Patient counseling and follow-up

Most patients leave the cath lab feeling reassured that everything went well, and for many, that’s true. But if advanced ECG analysis shows subtle heart stress or injury, it gives us a chance to talk honestly with the patient[21,22]. We can explain that while the angioplasty was successful, their heart muscle showed some signs of strain, so we want to keep a closer eye on things. This might mean an earlier follow-up visit, or planning a future echo or cardiac magnetic resonance imaging to check heart function. It also helps patients understand why it’s especially important for them to take their medicines, watch for symptoms, and follow lifestyle recommendations. In a larger sense, catching these small injuries early may help us prevent future problems, like heart failure or arrhythmias, by stepping in before those issues develop.

It’s important to remember that a single biomarker like troponin only tells us one thing; whether the level is elevated or not. But when we combine ECG and HRV data, we get a much deeper picture of what’s happening to the heart. For example, in the high-risk cluster, we didn’t just see signs of injury; we also saw increased sympathetic stress and more arrhythmias. That combination is likely more concerning than a quiet troponin rise. This reflects a broader shift in modern cardiology, using multiple types of data together to better understand risk.

We also have to remember that this was a small study and no major complications happened during the short follow-up period, so we shouldn’t overstate the immediate impact. But evidence from larger studies shows that even small signs of heart injury matter. Meta-analyses have found that mild troponin rises after PCI are linked to a real, measurable increase in long-term risk[23]. A large review of over 15000 patients found that about one-third had small troponin rises, and those patients had higher rates of death or heart attack later on (8.1% vs 5.2%)[9]. Even though some studies suggest that small, isolated troponin rises may not carry much risk in very stable patients, the overall pattern across the literature is consistent; any amount of heart injury is usually worse than none[10,24-27]. Therefore, if an advanced ECG/HRV system picks up signs of stress on the heart, it’s probably not something to ignore[28,29]. At the very least, it helps us spot patients who need closer follow-up. And in today’s personalized-medicine era, this kind of information can guide us in giving each patient the right level of care, hopefully catching problems early before they grow.

LIMITATIONS OF CONVENTIONAL BIOMARKERS AND ECG INTERPRETATION

Cardiac biomarkers and standard ECG interpretation remain central to post-PCI assessment, yet both have recognized limitations in detecting mild myocardial injury. High-sensitivity troponin assays frequently identify small post-procedural elevations that may represent true micro-infarction, but interpretation is complicated by baseline elevations, procedural context, and variable prognostic significance.

Traditional ECG interpretation is similarly constrained. Visual analysis is inherently binary and optimized for detecting gross abnormalities rather than subtle changes in repolarization or autonomic tone[14,30,31]. Advanced ECG analytics, including repolarization metrics and HRV-based indices, offer a more graded and physiologically nuanced assessment. However, the clinical meaning of these signals remains uncertain without robust outcome-based validation[14,30,31].

FUTURE DIRECTIONS AND NEED FOR VALIDATION

The observations discussed in this editorial underscore both the promise and the limitations of integrated ECG-HRV analysis after PCI. Future investigations should focus on larger, prospective, multicenter cohorts with standardized ECG acquisition and analysis protocols. Correlation with established biomarkers, advanced imaging modalities, and clinically meaningful outcomes, such as arrhythmias, heart failure, or mortality, will be essential to determine true clinical value.

Equally important will be comparisons with alternative assessment strategies, evaluation of cost-effectiveness, and assessment of feasibility within real-world clinical workflows. Only through such validation can advanced ECG analytics move from research settings into everyday practice.

CONCLUSION

Chaikovsky et al[17] offer an innovative perspective on post-PCI assessment by applying modern signal-processing techniques to a familiar tool, the ECG. Their exploratory findings suggest that subtle myocardial stress after PCI may be detectable through composite ECG-HRV indices even when conventional assessments appear normal. At present, this approach should be regarded as preliminary and hypothesis-generating. With appropriate validation, integrated ECG analytics may eventually contribute to more nuanced and personalized post-PCI care, helping clinicians better navigate the gray zone between procedural success and overt myocardial injury.