Holter features to detect coronary artery spasm in ANOCA patients: A pilot study

Background: Coronary artery spasm (CAS), which can be epicardial and/or microvascular, is highly prevalent in patients with angina and non-obstructive coronary artery disease (ANOCA) undergoing coronary function testing (CFT). The CFT is invasive and limits larger diagnostics studies. We studied if Holter monitoring with symptom tracking identifies Holter-based CAS features with diagnostic potential in ANOCA patients. Methods: 42 ANOCA patients (88% female) were recruited in the UMCU-IMPRESS pilot study and wore a 12-lead Holter device for 2–7 days prior to CFT, with simultaneous symptom tracking. We compared symptoms and Holter-ECG characteristics between patients with and without CAS and calculated diagnostic measures for CAS using several thresholds for ischemia-related parameters. Results: 33 Patients were diagnosed with CAS (79%). These patients more often had ≥ 1 min of ST depression in total per day compared to patients without CAS (≥0.035 mV: 88% vs 44%, p = 0.013; ≥0.040 mV: 73% vs 33%, p = 0.049), but discriminative ability was limited (AUC (95% CI): 0.65 (0.48–0.68)). Furthermore, patients with CAS had periods of lower heart rates and longer PQ and QT times than patients without CAS, most evident at night and early morning. Conclusions: Patients with CAS more often demonstrated at least one minute of ST depression in total per day and exhibited periods of lower heart rates and longer PQ times mainly during the night and early morning compared to patients without CAS. Although discriminative ability was limited, we show that Holter monitoring may reveal signals in CAS patients, substantiating the need of large (AI-based) studies.