CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 4, September/October 2023 AFRICA 249 Exclusion criteria were New York Heart Association (NYHA) class IV heart failure, cardiogenic shock, severe liver disease, respiratory failure necessitating intubation, severe obstructive airway disease, active malignancy, sepsis/septic shock and active infection, and history of allergy to iodinated contrast agents, adenosine or adenosine-containing products. Demographic and clinical characteristics, medical history, cardiovascular risk factors, laboratory tests, electrocardiography, echocardiography, CAG, stent length and diameter if undergoing percutaneous coronary intervention (PCI) were collected. Diabetes mellitus (DM) was defined as a diagnosis of fasting blood glucose ≥ 126 mg/dl (6.99 mmol/l) or glycated haemoglobin (HbA1c) ≥ 6.5% or the use of diabetes medication. Hypertension (HT) was defined as a diagnosis of systolic blood pressure ≥ 140 mm/Hg, diastolic blood pressure ≥ 90 mm/Hg or use of antihypertensive medication. Smoking was defined as current smoking or quitting within the previous year. Previous myocardial infarction (MI) was defined as MI diagnosed according to the European Society of Cardiology Fourth Universal Definition of Myocardial Infarction (2018) guidelines and stent implantation for an occlusive epicardial coronary lesion.4 An estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m2 for three months or longer was defined as chronic kidney disease (CKD).5 The study adhered to the tenets of the Declaration of Helsinki and was conducted with the permission of the Clinical Ethical Research Committee of Bursa City Hospital. FFR measurement was planned for patients with anatomical stenosis between 50 and 90% on CAG. Using the Boston Polaris multimodality guidance system, the COMET I or COMET II pressure guidewire was first flushed and reset with the pressure sensor externally placed in a horizontal position at the heart level. The guidewire pressure was then equalised with aortic pressure. The guidewire sensor was passed through the lesion at least 5 mm distal to the narrowed segment, and baseline Pd/Pa was measured and recorded as the baseline FFR value. Intracoronary isosorbide dinitrate was administered at a dose of 200 µg to rule out vasoconstriction,6 and adenosine infusion was then begun at a dose of 140 µg/kg/min via a large peripheral venous access. The lowest Pd/Pa value at the time of maximal hyperaemia was measured between 30 and 120 seconds after the start of the infusion, and this value was recorded as the FFR value. The guidewire was pulled proximal to the lesion and into the aorta. An increase in pressure and Pd/Pa value was observed, and the success of the procedure was confirmed. Values < 0.75 were considered critical stenosis. Values of 0.75–0.80 were decided by individual assessment. For values > 0.80, deferring PCI was considered. After collecting the data from the intracoronary pressure measurement protocols, the correlation of FFR values with various parameters (DM, HT, history of previous MI, vessel diameter, stent length, stent diameter) was assessed according to the presence or absence of critical coronary stenosis. Patients were divided into four groups, Q1, Q2, Q3 and Q4 (< 0.89, 0.89–0.92, 0.93–0.95 and > 0.95, respectively), taking into account patients’ baseline Pd/Pa values and clinical characteristics, including DM, HT, multivessel disease, previous MI, CKD and vessel diameter (< 3 mm or > 3 mm), stent length and stent diameter. Changes in FFR value at the time of maximal hyperaemia compared to baseline FFR value were evaluated, including subgroup analysis. Statistical analysis Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS version 21.0; IBM Corp, Armonk, NY, USA). Statistical significance was set at p < 0.05. The Shapiro–Wilk test was used to assess whether the measurements conformed to a normal distribution. The Student’s t-test or Mann–Whitney U-test was used for continuous variables according to the distribution pattern. Categorical variables are presented as percentages and the chi-squared test was used for comparison. A receiver operating characteristic (ROC) curve was used for sensitivity and specificity analysis. Results The mean patient age was 59.8 ± 9.2 years and 124 patients were male (78.5%). There was no significant difference in risk factors between the Q1, Q2, Q3 and Q4 groups. Multivessel disease was significantly higher in the Q1 group (p = 0.041). Baseline FFR value was lower in the Q1 group than in the other groups. Adenosine values were significantly lower in the Q1 and Q2 groups than in the Q3 and Q4 groups (p < 0.001). When analysing the percentage change, the Q3 and Q4 groups showed a greater change in adenosine level than the Q1 and Q2 groups (p < 0.001). Based on the FFR results, critical stenosis was more common in the Q1 and Q2 groups, whereas non-critical stenosis was more common in the Q3 and Q4 groups (p < 0.001). The threshold value of baseline FFR level for predicting critical stenosis was ≤ 0.92 with a sensitivity of 92.8% and a specificity of 82% (upper limit of Q2 quartile). Patients with a baseline FFR value ≤ 0.92 had a 58.4-fold greater likelihood of a critical outcome compared with patients with a baseline FFR value > 0.92 (OR: 58.4; 95% CI: 20.3–124.6). In patients with a baseline FFR ≤ 0.92, the Q1 group had a 10.23-fold higher odds of critical stenosis compared with the Q2 group (OR: 10.23; 95% CI: 2.14–48.84) (Figs 1, 2). 100 – Specificity (%) 0 20 40 60 80 100 Sensitivity (%) 100 80 60 40 20 0 AUC ± SE = 0.938 ± 0.02 Sensitivity = 92.8% Specificity = 82.0% PPV = 80% NPV = 93.6% Reference line Cut-off value ≤ 0.92 Fig. 1. The threshold value of the basal FFR value in predicting critical coronary artery stenosis was ≤ 0.92, with a sensitivity of 92.8% and a specificity of 82% (upper limit of the Q2 quartile) (AUC: area under the curve, PPV: positive predictive value, NPV: negative predictive value).
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