MINISTRY OF EDUCATION AND TRAINING MINISTRY OF DEFENCE 108 INSTITUTE OF CLINICAL MEDICAL AND PHARMACEUTICAL SCIENCES NGUYEN DUNG LATE POTENTIALS CHARACTERISTICS AND VENTRICULAR ARRHYTHMIAS IN CHRONIC[.]
MINISTRY OF EDUCATION AND TRAINING MINISTRY OF DEFENCE 108 INSTITUTE OF CLINICAL MEDICAL AND PHARMACEUTICAL SCIENCES NGUYEN DUNG LATE POTENTIALS CHARACTERISTICS AND VENTRICULAR ARRHYTHMIAS IN CHRONIC ISCHEMIC HEART DISEASE PATIENTS Majors/Speciality: Internal medicine/Internal cardiology Code: 9720107 SUMMARY OF MEDICAL PhD THESIS Hanoi – 2023 The thesis was done at: 108 Institute of Clinical Medical and Pharmaceutical sciences Supervisors: Assoc Prof PhD Pham Thai Giang Assoc Prof PhD Pham Nguyen Son Reviewers: This thesis will be presented at the Institute Council at: 108 Institute of Clinical Medical and Pharmaceutical sciences Day Month Year 20 This thesis can be found at: National Library of Vietnam Library of 108 Institute of Clinical Medical and Pharmaceutical sciences INTRODUCTION Necessity of the thesis Chronic ischemic heart disease (IHD) or stable coronary artery disease (CAD) and chronic coronary artery syndrom as Consensus of the European Society of Cardiology 2019 This disease affected about 126 million individuals (1,655/100,000), about 1.72% of the world population, of which about million deaths caused by: arrhythmia, heart failure, or heart attack Arrhythmias, especially ventricular arrhythmias, including ventricular tachycardia, ventricular fibrillation, can cause cardiac arrest, even sudden death Stratification and risk prediction for ventricular arrhythmias in patients with chronic IHD was important, and late potentials could help predict dangerous arrhythmias and predict cardiovascular disease There were many studies on late potential, but no study on late potential and its association with ventricular arrhythmias in patients with chronic IHD Meaning of the study The assessment, prediction, and risk stratification would help prevent and treat effectively Late ventricular potential recording was an effective, inexpensive, noninvasive, bedside technique that contributes to risk stratification for dangerous ventricular arrhythmias in patients with chronic IHD Objectives of the study To investigate of clinical, subclinical and late potential characteristics in patients with chronic IHD To assess the relationship between late potential and clinical characteristics, subclinical and ventricular arrhythmias in patients with chronic IHD The layout of the thesis The thesis had 125 pages, including: introduction and study objectives (2 pages), overview (35 pages), research objects and methods (19 pages), research results (28 pages), discussion (36 pages), conclusion (2 pages) and recommendations (1 page) The thesis had 50 tables, charts, 12 images, 170 references, 17 of which were Vietnamese and 153 English CHAPTER 1: OVEVIEW Chronic IHD, also known as chronic CAD, was a condition that occured when blood flow to the heart was reduced, usually dued to a partial or completed blockage of the coronary arteries that feed the heart, reducing the heart's ability to pump, leading to heart failure, to heart attacks or serious arrhythmias 1.1 Causes - Atherosclerosis: Atherosclerotic plaque accumulated on the thickened coronary artery wall, narrowing the coronary artery, obstructing blood flow, this was the most common cause - Blood clots: Atherosclerotic plaques could rupture causing blood clots, blocking the coronary arteries leading to myocardial ischemia Sometimes blood clots traveled from somewhere else - Coronary artery spasm: Prinzmetal's syndrome - Other causes: exertion, emotional stress, cold, stimulant abuse, overeating, violent sex 1.2 Symptoms 1.2.1 Symptoms - Angina: the most important clinical symptom The pain was usually behind the sternum and was an area (not a point), could spread to the neck, shoulder, hand, jaw, epigastric, back, commonly opened out to the left shoulder, then spread to the inner surface of the left hand, sometimes down to the fingers 4, It occured while exertion, strong emotions, cold, after a lot of meals or smoking and quickly decreased/ disappeared within a few minutes when the above factors decreased - Dyspnea: In patients with high risk of CAD, dyspnea was an important clinical indicator and was recommended by the ESC 2019 in addition to angina - Palpitations - Dizzies 1.2.2 Signs - Heart rate: If lower wall was ischemia, the heart rate slowed down, causing atrioventricular node ischemia Resting tachycardia: The cause was usually sympathetic nervous system activation, but could also be a manifestation of ischemic arrhythmias - Blood pressure measurement: Essential to diagnose hypertension, or hypotension (due to heart failure or an overdose of antihypertensive drugs) 1.3 Risk factors Including: old age, male gender, smoking, hypertension, diabetes, dyslipidemia, obesity, inactivity, family history of coronary artery disease 1.4 Diagnosis (5 steps) - Clinical examination - Assess comorbidities and quality of life - Laboratory testing - Assess the prior probability and the likelihood of disease - Select the appropriate diagnostic exploration method 1.5 Complications of chronic IHD - Myocardial infarction (MI): A coronary artery was completely blocked leading to MI, which was one of the serious complications, which could be fatal - Heart failure: Over time, IHD could lead to heart failure - Arrhythmias: Abnormal heart rhythms could disrupt the heart's contractile activity, which could be life-threatening Includes: tachyarrhythmias (ventricular tachycardia, ventricular fibrillation) and bradyarrhythmias (sick sinus syndrome ) Mechanism of arrhythmia in patients with chronic IHD Ischemia caused electrophysiological changes in myocardial cells, dispersed the repolarization and refraction time between the ischemic and healthy myocardium, changed electricity in ischemic hypertrophic myocardium, as well as after repolarization refraction, decreased conduction velocity At the same time there was an extracellular accumulation of potassium, the action of the sodium - potassium pump was incompletely inhibited in the ischemic myocardium, reducing the ability to maintain the potassium concentration difference The process of ischemia changed cell membrane permeability, changed the entry and exit mechanism of ions, changed intracellular Ca++, increased extracellular K+, decreased intracellular and extracellular pH, increased Ca++ and Na+ influx Accumulation of lysophospholipids inhibited some ion channels, causing changes in action potentials, causing cardiac arrhythmias In addition, myocardial ischemia also increased catecholamine release, adrenorecepter activation leading to an increased risk of ventricular arrhythmias 1.6 Late potential and signal averaged electrocardiogram (SAECG) Late potential was considered to be the body surface expression of late conduction in the heart, caused by ischemic or damaged myocardial areas, in patients with chronic ischemic heart disease or chronic heart failure In many studies, it had been found that there was a high rate of coronary artery disease in patients with dangerous ventricular arrhythmias Therefore, late potential was a prognostic indicator of patients at high risk of developing dangerous ventricular arrhythmias such as ventricular tachycardia, ventricular fibrillation in patients with chronic ischemic heart disease Ventricular late potentials are high-frequency, low-amplitude waves (1 to 40 µV), occurring in the terminal part of the QRS complex, recorded by a signal averaging and amplifying electrocardiogram (SAECG) Late potential parameters include: + HFQRS: The QRS duration based on the filtered high frequency signal + LAHF: Duration of the high frequency, low amplitude portion at the end of QRS cycle + RMS40: Root mean square value of the high frquency signal for terminal 40ms of the ventricular activation According to the consensus at the American Cardiology Conference 1995, the criteria to evaluate abnormal late potential was when at least of parameters are as follows: HFQRS > 114 ms, RMS40 < 20 µV, LAHF > 38 ms CHAPTER 2: RESEARCH OBJECTS AND METHODS 2.1 Objects Selection criterias Selection criterias for patients 162 old MI patients with or without revascularization, or patients had coronary angiography with stenosis greater than 50% of the diameter of the coronary artery Selection criterias for control group 87 people with no history and/or no cardiovascular disease or conditions affecting the heart: physical examination, 12-lead ECG at rest, routine echocardiography showed normal results Exclusion criterias Who need of immediate treatment: acute coronary syndrome, persistent ventricular tachycardia, ventricular fibrillation, high-grade atrioventricular block, severe electrolyte disturbances… Who was taking drugs that affect the heart rhythm a lot, such as: Digoxin, Atropin, Amidarone but could not be stopped Who had results of SAECG and Holter were too noisy, the time of wearing the Holter electrocardiogram machine was less than 22 hours Not agreeing to participate in the study 2.2 Methods Methods: Cross-sectional, descriptive, controlled study Objects were asked about the disease, taking history and risk factors for CAD Time: from 3/2016 to 10/2018 Place: 108 Military Central Hospital Research steps - Step 1: Made a medical record (Appendix I) - Step 2: Explained and requested to patients to participate in the study Collected information on history, examined for symptoms - Step 3: Laboratory tests: blood test, electrocardiogram, echocardiogram - Step 4: Recording 24-hour Holter ECG, recording SAECG - Step 5: Collecting and processing research data Signal averaged electrocardiogram recording procedure Equipment MAC 5500 HD high resolution ECG system (signal averaged) of General Electric (USA) Steps to take - Patient preparation - Preparing the SAECG - Attaching electrodes on the skin: according to the specified positions - Measuring late potential parameters on SAECG: + HFQRS: (ms) + LAHF: (ms) Diagram of parameters of late potential + RMS40: (µV) + Noise: Required less than 1µV, if above 1µV would be removed Holter electrocardiogram recording procedure Equipment PHILIPS DigiTrak XT Electrocardiogram Holter System (USA) Via the 5electrode cable system, thanks to the exclusive technology of Philips EASI The position of the electrodes was as follows: - E (brown): Intercostal space 5, mid-thoracic (near the nasopharynx) - A (black): Same level as E in the left midaxillary line - S (red): The apex (hilt) of the sternum - I (white): Same level as E and A, right mid-axillary line - Ground (green): in the middle of the sternum or any other convenient location Signal channels: - Channel 1: E (+) to S (-): V1 on ECG - Channel 2: A (+) to S (-): V6 on ECG - Channel 3: A (+) to I (-): aVF on ECG Steps to take - Patient preparation - Attaching the electrode and connecting the 24-hour Holter recorder Location of electrodes - Setting program for Holter system - Unplug the device after 24 hours Analysing 24 - hour Holter ECG result Analyzing parameters: mean heart rate, fastest, slowest heart rate, ventricular and supraventricular arrhythmias, number of extrasystoles, features of ventricular arrhythmias according to Lown's classification CHAPTER 3: RESULTS OF THE STUDY 3.1 General features of study objects 3.1.1 Features of age, gender The number of patients with chronic IHD was more common in the 61-75 age group (79.4% women and 64.1% men in this age group) Rarely in women under 60 years of age, and no young women < 45 years with chronic IHD Meanwhile, the number of male patients under 45 years old with chronic IHD accounted for 2.3% Table 3.1 Comparison of age and gender of the study objects Patients group Control group Parameters p (n = 162) (n = 87) Age (year) 66,91 ± 8,92 64,15 ± 7,82 > 0,05* Male 128 (79%) 60 (69%) Gender > 0,05** Female 34 (21%) 27 (31%) (*: t-test, **: χ2 -test) 3.2 Clinical, subclinical and late potential features in study objects 3.2.1 Clinical features Heart rate, blood pressure of study objects Table 3.3 Heart rate, blood pressure of study objects Patients group Control group Parameters p (n = 162) (n = 87) Heart rate (bpm) 78,25 ± 8,66 76,47 ± 7,14 > 0,05 Systolic BP (mmHg) 125,74 ± 10,91 119,60 ± 6,30 < 0,05 Diastolic BP (mmHg) 75,07 ± 8,66 72,99 ± 6,12 < 0,05 (t-test) Angina pectoris Angina grades (%) No angina CCS CCS 00 01 09 09 CCS CCS 80 Chart 3.2 Agina feature of chronic IHD patients Dyspnea: Assess the degree of heart failure and the degree of dyspnea according to NYHA Table 3.4 Features of heart failure of chronic IHD patients Features NYHA I NYHA NYHA level NYHA Number 89 43 28 Percentage % 54,9 26,5 17,3 NYHA 162 1,2 100 Total Other symptoms Table 3.5 Other clinical manifestations in patients with chronic IHD Symptoms Number Percentage % Palpitations 54 33,3 Dizziness 5,6 Syncope 2,5 Risk factors: Common risk factors were: hypertension (87.0%), dyslipidemia (56.8%), smoking (53.7%), alcohol abuse (42.6%), and history of MI (38.9%) 3.2.2 Subclinical features 3.2.2.2 ECG characteristics Table 3.10 Ischemic features on ECG of chronic IHD group Percentages in Percentages in Parameters n No of ischemic total of patient ECG (n=70) (n=162) Front wall 17 24,3 10,5 16 22,9 9,9 Ischemic Back wall location Lateral wall 10 14,3 6,2 Multi regions ischemic 27 38,6 16,7 ECG no ischemic 92 56,8 3.2.2.3 Echocardiography features Table 3.12 Features of ejection fraction and regional dyskinesia Parameters n % EF% ≥ 50% 115 71,0 EF% from 40 - 49% 19 11,7 EF% from 30 - 39% 24 14,8 EF% < 30% 2,5 Total 162 100 Wall dyskinesia 63 38,89 11 Late potential features in chronic IHD patients with alcohol abuse Table 3.23 Late potential features related with alcohol abuse Alcohol abuse Nondrinker Parameters p (n = 69) (n = 93) HFQRS (ms) 96,91 ± 21,27 91,06 ± 18,81 < 0,05 LAHF (ms) 35,28 ± 9,10 32,28 ± 10,98 > 0,05 RMS (µV) 23,28 ± 9,77 26,06 ± 13,48 > 0,05 (t – test) Late potential features in chronic IHD patients with reduced EF Table 3.28 LP features in group with EF < 40% and group with EF ≥ 40% Parameters EF < 40% EF ≥ 40% p (n=28) (n=134) HFQRS (ms) 104,71 ± 20,96 91,22 ± 19,12 0,001 LAHF (ms) 37,71 ± 9,38 32,69 ± 10,30 < 0,05 RMS40 (µV) 20,04 ± 6,49 25,89 ± 12,74 < 0,05 (t – test) 3.3 The relationship between late potential with some clinical, subclinical features and ventricular arrhythmias in patients with chronic IHD 3.3.1 The relationship between late potential with some clinical features 3.3.1.2 Risk of abnormal LP associated with some clinical features and risk factors in patients with chronic IHD Table 3.30 Risk of abnormal LP associated with clinical features Normal LP Abnormal LP (n=100) (n=62) Clinical features OR 95%CI p n % n % No 15,0 9,7 0,20Angina 0,59 > 0,05 1,78 Yes 93 85,0 55 90,3 No 61 52,0 20 37,1 1,69Dyspnea 3,29 < 0,001 6,40 Yes 39 48,0 42 62,9 No 94 94,0 14 22,6 19,42Palpitation 52,71 < 0,001 148,60 Yes 6,0 48 77,4 No 98 98,0 55 87,7 1,25Dizziness 6,24 < 0,05 31,07 Yes 2,0 11,3 No 99 99,0 59 95,2 0,51Syncope 5,03 > 0,05 49,51 Yes 1,0 4,8 (χ2-test) 12 3.3.2 The relationship between late potential with some subclinical features 3.3.2.1 The relationship between late potential with ECG features Tabel 3.32 The relationship between ischemic location on ECG and late potential Ischemic Non Front Back Lateral Multi location ischemic wall wall wall region Late potential Normal 67 11 (n, %) (72,8%) (41,2%) (56,3%) (60%) (40,7%) Abnormal 25 10 16 (n, %) (27,2%) (58,8%) (43,7%) (40%) (59,3%) Total 92 17 16 10 27 3.3.2.3 Risk of abnormal LP associated with reduces ejection fraction (EF < 40%) Table 3.34 Risk of abnormal LP in patients with EF 0.05) (table 3.22) Late potential characteristics in chronic IHD patients with alcohol abuse HFQRS in the chronic IHD group with alcohol abuse was higher than that in the non-drinking group 96.91 ± 21.27 ms versus 91.06 ± 18.81ms (p < 0.05) And LAHF and RMS40 in the groups were not different: 35.28 ± 9.10 ms versus 32.28 ± 10.98 ms and 23.28 ± 9.77 µV versus 26.06 ± 13.48 µV (p) > 0.05) (table 3.23) Late potential characteristics in chronic IHD patients with reduced ejection fraction In the group with EF < 40%: HFQRS = 104.96 ± 19.95 ms was larger than 89.60 ± 17.80 ms in the EF group ≥ 40% (p = 0.001) Similarly LAHF = 38.43 ± 7.49 ms was greater than 33.15 ± 8.77 ms (p < 0.05); and RMS40 = 20.04 ± 6.60 µV was smaller than 25.43 ± 11.28 µV (p < 0.05) (table 3.28) 4.3 The relationship between late potential and clinical, subclinical and ventricular arrhythmias features in patients with chronic IHD 4.3.1 The relationship between LP and clinical features and risk factors 4.3.1.2 Association of some clinical features with abnormal LP Abnormal LP did not affect the risk of angina (p > 0.05) (table 3.30) Angina was a common symptom in patients with chronic IHD, among the study subjects, the rate of angina accounted for more than 90% But abnormal LP was not a feature that increased or decreased the risk of angina or its severity However, having abnormal LP increased the risk of developing dyspnea by 3.29 times (OR=3.29; 95%CI: 1.69-6.40) compared with the group without abnormal LP, with p < 0.001 This could be understood because patients with chronic IHD when admitted to the hospital had shortness of breath, that was, they almost had clinical heart failure And heart failure patients with dilated heart chambers, electrolyte disturbances increased the frequency of abnormal LP According to Galinler et al., the rate of abnormal LP in patients with heart failure 21 due to chronic ischemic heart disease was 35%, increased compared with the group without heart failure In this study, we found that having an abnormal LP also increased the risk of palpitations and dizziness, which were very important signs Specifically, patients with abnormal LP, the risk of palpitations was 52.7 times higher than those without abnormal LP (OR = 52.71; 95% CI: 19.42- 148.6; p < 0.001) With the manifestations of dizziness and vertigo, abnormal LP was also a factor that increased the risk of occurrence by 6.2 times (OR=6.24; 95%CI: 1.2531.07; p) < 0.05) This was a sign that we can saw in patients with chronic IHD, especially those with arrhythmias, with unstable chest pain Causes of dizziness can include: atrial fibrillation that causes an irregular heartbeat, and heart attacks… Syncope could occur in chronic IHD According to a study by Aro A.L et al in 2017: syncope was associated with an increased risk of sudden cardiac arrest in patients with chronic IHD even with preserved left ventricular function In our study, the number of cases of syncope was cases, accounting for 2.5% However, the effect of abnormal LP on the risk of syncope not clearly seen (p > 0.05) Maybe because the sample size of our study was small, the number of patients with syncope was small, not enough to make a conclusion, and so there were no results consistent with foreign studies (table 3.30) 4.3.2 The relationship between late potential and subclinical features 4.3.2.1 Association of abnormal LP with ECG characteristics More than half of patients with extensive myocardial ischemia (59.3%) and anterior wall ischemia (58.8%) had an abnormal LP This rate was higher than the rate occurring in other ischemic sites (table 3.32) 4.3.2.3 Risk of abnormal LP in patients with reduced ejection fraction In our study, when chronic IHD patients had heart failure, EF decreased (EF < 40%) the risk of abnormal LP increased 6.8 times compared with the other group (EF ≥ 40%) (OR = 6.8; 95% CI: 2.68-17.26; p < 0.001) (table 3.34) According to author Gatzoulis et al (2017) for patients with chronic IHD, if the ejection fraction reduced - the risk of ventricular arrhythmias would increase However, not only relied on ejection fraction to stratify risk, but also needed to combine other methods, including late potential 22 4.3.2.3 Risk of abnormal LP in patients with wall dyskinesia According to the results of our study, in chronic IHD patients with wall dyskinesia, the risk of abnormal LP was 3.74 times higher than that of the other group (OR = 3.74; 95% CI: 1) .92-7.32; p < 0.001) (table 3.35) 4.3.3 The relationship between late potential and ventricular arrhythmias in chronic IHD patients 4.3.3.2 Risk of ventricular arrhythmias in chronic IHD patients with abnormal LP Abnormal LP parameters increased the risk of ventricular arrhythmias (tables 3.37, 3.38, 3.39): Abnormal HFQRS increased the risk of couplets VPCs 9.5 times (p < 0.001), increased the risk of ventricular tachycardia 5.35 times (p < 0.001), increased the risk of VPCs R/T type 4.38 times (p < 0.05) and increased the risk of complicated ventricular arrhythmia 10.82 times (p < 0.001) Abnormal LAHF increased the risk of couplets VPCs 20.61 times (p < 0.001), increased the risk of ventricular tachycardia 23.01 times (p < 0.001) and increased the risk of complicated ventricular arrhythmias 22, 25 times (p < 0.001) Abnormal RMS40 increased the risk of of couplets VPCs 21.47 times (p < 0.001), increased the risk of ventricular tachycardia 52.36 times (p < 0.001) and increased the risk of complicated ventricular arrhythmias 22.25 times (p < 0.001) Abnormal LP increased the risk of couplets VPCs 71.62 times (p < 0.001), increased the risk of ventricular tachycardia 2.3 times (p < 0.001) and increased the risk of complicated ventricular arrhythmias 79.17 times (p < 0.001) compared to patients with normal late potential results (table 3.40) Obviously, abnormal LP increased the risk of developing dangerous ventricular arrhythmias, so treatment to reduce abnormal LP would help reduce the risk of ventricular arrhythmias Recently, with the development of interventional techniques, abnormal LP catheter ablation has been applied to treat ventricular arrhythmias Di Marco et al (2018) found that late potential ablation reduced recurrent ventricular tachycardia, especially in patients at high risk for chronic complete occlusion of the coronary arteries According to 23 Zachariah et al (2022): late potential was associated with ventricular arrhythmias and had a sensitivity of 67.3%, a positive predictive value of 77.8% 4.3.3.3 Sensitivity and specificity of late potentiation in predicting ventricular arrhythmias in patients with chronic IHD: The late potential recording method had an important role in predicting ventricular arrhythmias in patients with chronic IHD In our study: the sensitivity of the method was 90.9% and the specificity was 88.8% The positive predictive value was 80.6% and the negative predictive value was 95% (table 3.41) According to Hammil's study, the sensitivity was 87%, the specificity was 65%, and the positive predictive value was 77% to identify patients at risk for ventricular tachycardia The sensitivity in our study was close to that of Kuchar (93%) and higher than most other authors The specificity was close to that of Rodriguez (91%), but higher than most other authors CONCLUSION Clinical, subclinical and late potential features in chronic ischemic heart disease patients - Mean age: 66.91 ± 8.92 years old (from 28-88), mostly 61-75 years old Ratio: male/female ~ 3.8/1 - Common symptoms in chronic IDH patients were: angina (90.7%); dyspnea (50%); palpitations (33.3%), dizziness (5.6%) - Common risk factors: hypertension: 87%; dyslipidemia: 56.8%; smoking: 53.7%; alcohol abuse: 42.6% and history of MI: 38.9% - Holter ECG results: + In group of chronic IHD: 88.9% had ventricular premature complexs (VPCs), of which complicated VPCs (Lown 3-5) accounted for 34.0% + In control group: 57.5% had VPCs, mainly simple VPCs - The rate of abnormal LP in the chronic IHD group was 38.3%, in the control group: 1.1% - The parameters of the abnormal LP group: HFQRS = 111.71 ± 17.39 ms; LAHF = 41.11 ± 6.54 ms and RMS40 = 16.84 ± 3.90 µV, while in the normal LP group, HFQRS = 82.30 ± 11.51 ms, LAHF = 82.30 ± 11, 51 ms and RMS40 = 29.86 ± 12.75 µV 24 The relationship between late potential with clinical, subclinical and ventricular arrhythmias in patients with chronic IHD - Young people with chronic IHD had a higher risk of abnormal LP than the elderly (more than 50% of patients under 60 years old had abnormal LP) - The abnormal LP in men and women was equivalent - Smoking and alcohol abuse affected the late potential - Patients with chronic IHD with abnormal LP did not have an increased risk of angina and syncope, but the risk of palpitations increased 52.71 times and the risk of dizziness increased 6.24 times compared with those with normal LP - Patients with chronic IHD with EF < 40%, the risk of abnormal LP was 6.28 times higher than with EF ≥ 40%; with wall dyskinesia on echocardiography, the risk of abnormal LP was 3.74 times higher than that without wall dyskinesia - Patients with chronic IHD with abnormal LP had 71.62 times increase in the risk of couplet VPCs, 2.3 times increase in short ventricular tachycardia, and 79.17 times increase in the risk of complicated ventricular arrhythmias compared with patients with normal LP results If had abnormal HFQRS, the risk of VPCs R/T increased 4.38 times - The sensitivity of the LP recording method in assessing ventricular arrhythmias in patients with chronic IHD was 90.9%; the specificity was 88.8% The positive predictive value was 80.6% and the negative predictive value was 95% RECOMMENDATIONS - It was recommended to record the signal averaged electrocardiogram in patients with chronic IHD to evaluate the late potential, which was the basis for predicting the risk of ventricular arrhythmias, especially in patients with symptoms of dyspnea, palpitations, and dizziness or on echocardiography with an ejection fraction less than 40% and/or wall dyskinesia - It was necessary to set up the signal averaging electrocardiogram system for the cardiovascular departments of provincial general hospitals to help stratify and predict the risk of dangerous ventricular arrhythmias in patients with chronic ischemic heart disease LIST OF PUBLISHED RESEARCH RELATED TO THE THESIS Nguyen Dung, Pham Nguyen Son, Pham Thai Giang (2022) Research of ventricular arrhythmias on Holter ECG and relationship with late potentials in chronic ischemic heart disease patients Journal of 108Clinical Medicine and Pharmacy, volume 17, issue 7/2022: – Nguyen Dung, Pham Nguyen Son, Pham Thai Giang (2022) Assessment of late potential in chronic ischemic heart disease patients Journal of 108Clinical Medicine and Pharmacy, volume 17, issue 7/2022: 13 – 18 Nguyen Dung, Pham Nguyen Son, Pham Thai Giang (2022) Late potential assessment in normal subjects Journal of 108-Clinical Medicine and Pharmacy, volume 17, special issue 11/2022: 156 - 161