Diagnosis of coronary microvascular dysfunction by intracoronary electrocardiogram. Comparison of an intracoronary doppler and an intracoronary electrocardiogram

Aim of the study: Calculation of coronary flow reserve by taking basal and hyperemic recordings with intracoronary Doppler is one of the gold standard methods in the diagnosis of coronary microvascular dysfunction. This system, which provides information about the physiology of coronary flow with its specially designed pressure transducer at its tip, is not available in most angiography laboratories, and is not routinely applied in laboratories because of its longer processing time than diagnostic angiography, the cost of wire and the need for a compatible device for measurements. Electrocardiogram is an indispensable part of routine cardiology practice. The 12-lead ECG used in daily practice is used in the diagnosis and exclusion of coronary artery disease in patients with ischemic symptoms. ECG changes can be recorded instantaneously in correlation with the symptoms and clinical conditions of the patients, and can also give an idea about the disease. In this study; we aimed to compare intracoronary Doppler measurements used in the diagnosis of coronary microvascular dysfunction with intracoronary ECG changes. Material and Methods:In our study, the patients who applied to Istanbul Medical Faculty Cardiology Department between 07.12.2021 and February 2022; 21 patients who underwent myocardial perfusion scintigraphy with suspicion of coronary artery disease and were scheduled for coronary angiography due to ischemia were included. Information about the medical history and chronic diseases of the patients was obtained from the anamnesis forms taken during the outpatient clinic examinations. Myocardial perfusion scintigraphy was performed with the GE Healthcare Discovery NM/CT 670 device in the Nuclear Medicine Department of Istanbul Medical Faculty. Coronary angiography was performed in the patients who were found to have ischemia as a result of the test, as recommended by the guidelines. In cases where plaques narrowing the vessel lumen by 30% or less were detected as a result of coronary angiography, planned intracoronary measurements were performed because microvascular angina was considered. Doppler measurements were made with a 0.014 inch sensor-tipped pressure recording wire (ComboWire XT, Philips Volcano Corporation, San Diego, CA, USA) parked in the coronary artery at the location where the flow pattern is optimal. Intracoronary adenosine was used in appropriate doses to achieve maximal hyperemia. Intracoronary ECG recordings were performed with DONGJIANG ECG-11D device by attaching probes to the patient's extremity leads and connecting to lead V1 via an intracoronary 0.014 inch floppy wire. The doses obtained in the Doppler recording were used for maximal hyperemia. Results: As a result of the average of 63 recordings made as a result of the evaluation of the records transferred to the ComboMap console of the pressure + flow sensor wire (ComboWire) measurements in 3 normal epicardial arteries in each patient, it was found the mean intracoronary basal flow velocity was 22.53 ± 5.95 cm/sec, and the mean intracoronary hyperemic flow velocity was 59.63 ± 13.05 cm/sec, mean CFR 2.34 ± 0.65, mean basal microvascular resistance 4.51 ± 1.22 mmHg.cm-1.sec, mean hyperemic microvascular resistance 2.01 ± 0.56 mmHg.cm-1.sec, and mean arteriolar resistance index 2.50 ± 1.03 . Although the averages of hemodynamic recordings made separately from the LAD, right coronary artery and circumflex artery area showed small differences, these differences were not significant. As a result of the comparison of intra-coronary pressure/flow and intra-coronary ECG (ICECG) recordings made in the artery (ischemic) irrigating the myocardial ischemia region indicated by the noninvasive test and in 2 other coronary arteries irrigating the non-ischemic myocardial regions, the artery irrigating the ischemic region was compared to the arteries irrigating the non-ischemic region. Intracoronary hyperemic flow velocity (APVH) (45 ± 12.68 vs 53.45 ± 12.44 cm/sec, p= 0.014) and CAR (2.09 ± 0.39 vs 2.46 ± 0.72, p= 0.011) were significantly lower and hyperemic microvascular resistance (HMR) ( 2.26 ± 0.63 vs 1.87 ± 0.48 mmHg.cm-1.sec, p= 0.009 ) were found to be significantly higher. In ICECG measurements, delta ST (difference between the absolute amount of ST segment deviation taken from IKEKG at basal conditions and ST segment deviation obtained under hyperemic conditions) showed a significant difference between ischemic (0.30 ± 0.34) and non-ischemic (0.06 ± 0.10) regions (p). = 0.001). Other parameters did not indicate a significant difference between ischemic and non-ischemic regions. Basal mean intracoronary flow velocity (APVB) (r= -0.28, p= 0.026) of delta ST determined from IKEKG records as a result of a total of 63 conjugate measurements performed in basal (n= 63) and hyperemic (n=63) conditions in 3 vessels in a total of 21 patients, with APVH (r= -0.388, p= 0.082) , BMR (r= 0.475, p= 0.03), HMR ( r= 0.399, p= 0.07) found to be significantly related. In the subgroup analysis, these relationships remained significant in the group of arteries irrigating the ischemic area (n= 21), APVB (r= -0.487, p= 0.025), BMR (r= 0.475, p= 0.03); It was observed that it remained close to the limit of significance for APVH (r= -0.388, p= 0.082) and HMR (r= 0.399, p= 0.07). In the analysis performed in the whole group, it was observed that while delta ST showed significant relationships with APVB (R= -0.28, P= 0.026), APVH (R: -0.354, P= 0.004) , BMR (R= 0.317, P= 0.011) and HMR (R= 0.408, P= 0.001), its relationship with other hemodynamic parameters did not reach the level of significance. Functional microvascular disease was defined as the coexistence of CFR <2 and structural microvascular disease CFR<2 and HMR >1.9 (ESC guideline). According to this classification, in 17 patients with structural coronary disease, the delta ST value was significantly lower (0.08 ± 0.11 vs 0.30 ± 0.38, p: 0.001) compared to the group without structural disease (n= 46). Although this difference was significant in the group with only functional dysfunction, it was less. In the ROC curve analysis, the parameter with the highest sensitivity and specificity in the detection of ischemia detected in SPECT was delta ST (cut-off value: 0.19, area under the curve: 0.83); it was followed by HMR (cutoff value 2.05, area under the curve: 0.69) and finally CFR (cutoff value: 2.60, area under the curve 0.35). Conclusion: It is seen that the difference between basal and hyperemic ST segment levels (Delta-ST) stands out among IKEKG indices. With the growth of the database, further analysis may provide additional IKECG indices (Delta-T, area under the curve, ST and T curves…) of clinical value. First of all, the negative result of Delta-ST in myocardial segments without microvascular structural and functional disorders increases its negative predictive value. The fact that Delta-ST even allows to distinguish between functional and structural disorders in patients with microvascular disease (Table 5) seems exciting in terms of its diagnostic value. Hemodynamic parameters and Delta-ST were significantly correlated as expected (Table 3). Although it is significant, the relatively scattered relationship may be related not only to the limited number of patients, but also to the high variability of hemodynamic indices. However, it is clear that IKEKG also has this responsibility methodically. It is important that this correlation is higher in ischemic area data. It is usual that there is no association in non-ischemic regions. Delta-ST, which is essentially an indicator of ischemia, does not need to predict "good perfusion" indicators in well-perfused segments (Table 4). When the relationship between IKEKG and hemodynamic parameters is examined at the level of arteries, it is seen that the relationship is strongest in data originating from LAD, the Cx artery comes second, and RCA takes the last place (Table 7). Electrocardiographic ischemia changes are created by the difference in perfusion between regions, not by absolute perfusion deficiency of the region. Evidence of ischemia in a region occurs when that region is less perfused than other regions. Therefore, ECG ischemia sensitivity decreases when all regions are ischemic. Even if the perfusion of the examined region is increased, ischemia findings may develop when this increase is less than the increase in the reference regions. The ST segment elevation after the use of hyperemic agents in IKECG recordings must be related to the inability to increase the perfusion of the problematic region as much as other regions. Although the results of the study were obtained from patients with microvascular disease, it can be thought that it may also be useful in revealing ischemia due to epicardial stenosis other than microvascular disease, since the parameter examined reflects ischemia. If the method is shown to be useful in evaluating the functional significance of epicardial stenosis, a significant contribution can be made to the practice of invasive cardiology.