CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 4, September/October 2023 AFRICA 207 As a result of the lack of data concerning arrhythmia, there are limited specific recommendations concerning duration of hospitalisation and follow up for this specific setting. For example, atrial fibrillation (AF) is the most common arrhythmia in daily clinical practice. Identifying MINOCA patients at risk for AF using simple, non-invasive and widely accessible electrocardiographic (ECG) markers would be extremely useful for clinicians in determining which patients should be monitored more closely and for more extended periods.8 On the other hand, ventricular arrhythmias are the most critical, life-threatening arrhythmias, and necessary recommendations and precautions can be applied by pre-detection of the risk utilising ECG.9 This study aimed to determine whether MINOCA patients may be at increased risk of AF and ventricular arrhythmias based on readily available ECG measurements, compared to stable patients without significant lesions in their coronary arteries. Methods In this retrospective cohort study, patients who were admitted to the emergency department with chest pain and high cardiac troponin levels between January 2020 and September 2021, who were diagnosed as MINOCA patients, were identified and included. The control group included patients who were scheduled to undergo coronary angiography under out-patient clinic conditions but did not have significant lesions (< 50% stenosis) in their coronary arteries. The coronary angiography of MINOCA patients was evaluated by at least two invasive cardiologists’ visual evaluation and quantitative angiography (QCA) measurements. The pathophysiological mechanisms of MINOCA were investigated from the coronary angiography images of patients. One of the most important limitations of our study is that we could not give precise information about the underlying pathophysiology of MINOCA since we could not use routine intravascular ultrasound (IVUS) and optical coherence tomography (OCT). The literature defines vulnerable plaque morphology angiographically in studies performed before IVUS and OCT. Based on these studies, we determined that irregular borders or intraluminal lucency, haziness and slowing of the flow rate in the lesion area are characteristic of vulnerable plaque.10,11 Suspected clinical vasospastic angina was diagnosed by acetylcholine provocation test, but a routine provocation test was not performed to detect epicardial coronary vasospasm for all patients. The inclusion criteria in both groups were age above 18 years, patients who were scheduled to have angiography as out-patients and who were not found to have significant coronary stenosis. Exclusion criteria in both groups were defined as patients whose file records and ECGs could not be accessed from the hospital archive and data system; those with atrial fibrillation, atrial flutter, multifocal–unifocal atrial tachycardia, atrial extrasystole, ventricular tachycardia, ventricular extrasystole and ventricular conduction delay in the admission ECG or medical history of the patients; patients with unstable cardiac status (in unstable clinical conditions such as unstable angina and decompensated heart failure, repolarisation and depolarisation abnormalities are frequently observed in the ECG); patients with organ failure (chronic renal failure, cirrhosis, chronic obstructive lung disease, stroke and dementia), malignancy and infectious status. All procedures were performed as per the Declaration of Helsinki. The local ethics committee approved the study (University of Health Sciences Gülhane Training and Research Hospital Ethics Committee decision number 2021-362, date: 21.10.2021). Following a 10-minute rest period, 12-lead ECGs were acquired in a supine position using a commercially available ECG machine (GE Healthcare, MAC 2000) with 10 mm/mV amplitude and 25 mm/s rates and standard lead placements. The ECG records of the patients were taken before coronary angiography in the control group and on the day of admission when cardiac enzymes were elevated in the MINOCA patients to eliminate bias. Each ECG lead was measured with at least five consecutive beats as an average, depending on heart rate. ECG images were 10-fold amplified and measured with Image J software. Two blinded cardiologists who had no information about the patients examined each image. We investigated P waves after determining that the isoelectric interval existed and that the P waves did not fuse with the preceding QRS complex or T wave. PR intervals were calculated from the onset of the P wave to the beginning of the QRS complex, and PR segments were calculated from the end of the P wave to the beginning of the QRS complex. P-wave duration was assessed in leads II, III and aVF of the 12 surface ECG leads. The voltage of the P wave in lead I was used to determine the wave’s peak or nadir to the isoelectric line. P-wave duration ≥ 120 ms was considered as prolongation. Partial inter-atrial conduction block was defined as P-wave duration ≥ 120 ms. Advanced inter-atrial block was defined as prolongation and a biphasic (±) morphology in the inferior leads. The morphology–voltage–P‐wave duration (MPV) ECG AF risk score is a simple and effective method that can predict the risk of AF, utilising ECG, which has only recently been used in the research.12,13 Three P‐wave variables formed the MPV score: P-wave morphology in the inferior leads, the voltage of the P wave and duration in lead 1.12 The QRS complex, which is a composite of the Q, R and S waves, represents ventricular depolarisation and is measured from the end of the PR interval (or the beginning of the Q wave) to the end of the S wave. The QT interval, measured from the beginning of the QRS complex to the end of the T wave, was calculated using the Bazett formula: QTc = QT (R–R interval). QT dispersion was measured within each lead by comparing the longest (QTmax) and shortest (QTmin) QT intervals. The Tpeak–Tend interval was defined as the interval between the T wave’s peak and end. Tpeak–Tend interval measurements were taken using precordial leads. These measurements were used to calculate the Tpeak–Tend/QT and Tpeak–Tend/QTc ratios. Studies use QT interval, QT dispersion Tpeak–Tend time, and Tpeak–Tend/QT interval ratios to predict ventricular arrhythmia risk from ECG in many diseases and clinical conditions.9,14,15 All echocardiographic examinations were performed using the ultrasound imaging system with S4-2 transducer (GE Healthcare, Vivid S70N). Apical four- and two-chamber images were acquired in the left lateral decubitus position, using the parasternal long and short axes. Two-dimensional images were used to determine the left atrial size, left ventricular (LV) end-systolic and LV end-diastolic diameters. Simpson’s biplane volume method was used to measure the ejection fraction. Diastolic function was evaluated following current guideline recommendations.16
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