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UDC 616.12-008.3-073.96
DISTRIBUTION OF QT DURATION ACCORDING
TO AMBULATORY ECG MONITORING DATA IN PATIENTS WITH HYPERTENSION DEPENDING ON CLINICAL MANIFESTATIONS
Tselik N. E., Shmidt O. Y., Martynenko O. V.
V. N. Karazin Kharkiv National University, Kharkiv, Ukraine
The study was carried out to identify the distribution of QTc during ECG AM depending on clinical features of EH in 82 patients. As classified shortened was considered QTc < 320 ms, as normal > 320 ms and < 440 ms, as classified prolonged was considered QTc > 440 ms. Average, maximum and minimum QTc are registered in every patient during ECG AM. The results confirm low probability of short QTc and demonstrate presence of prolonged QTc in every patient during ECG AM. The largest duration of maximal QTc have adulthood male patients with obesity III st., with low and high circadian index, with II stage and mild EH, with for the first time diagnosed EH and with EH lasting more than 10 years, with mild cardiovascular risk, with diffuse cardiosclerosis, with I and II FC and I and IIA st of HF.
KEY WORDS: hypertension, duration of QTc interval, ambulatory ECG monitoring
РОЗПОД1Л ТРИВАЛОСТ1 1НТЕРВАЛУ QTc ЗА ДАННИМИ АМБУЛАТОРНОГО МОН1ТОРУВАННЯ ЕКГ У ХВОРИХ З Г1ПЕРТОН1ЧНОЮ ХВОРОБОЮ В ЗАЛЕЖНОСТ1 В1Д КЛ1Н1ЧНИХ ПРОЯВ1В
Целж Н. €., Шмiдт О. Ю., Мартиненко О. В.
Харювський нацюнальний ушверситет iMeHi В. Н. Каразша, м. Харюв, Украша
Проведено вивчення розподшу тривалост QTс при АМ ЕКГ в залежност вщ клшчних ознак ГХ у 82 пащенлв. За класифжований укорочений приймали QTc < 320 мс, нормальний > 320 мс та < 440 мс, класифжований подовжений > 440 мс. У кожного пащента за даними АМ ЕКГ зареестроваш середнш, максимальний та мшмальний QTc. Результати тдтверджують рщку вiрогiднiсть укороченого QТс i показують юнування подовженого QТс у кожного пащента при АМ ЕКГ. Тривалють максимального QTc найбшьша у пащенпв зршого в^, чоловiчоl стап, з ожирiнням III ст., iз зниженим та високим циркадним шдексом; II стадiею та м'якою ступеню ГХ, з вперше зареестрованою та бiльше 10 рокiв ГХ, помiрним кардiоваскулярним ризиком серцево-судинних ускладнень, дифузним кардюсклерозом, I i II ФК та I i НА стадiею ХСН.
КЛЮЧОВ1 СЛОВА: гшертошчна хвороба, тривалiсть iнтервалу QTc, амбулаторне монггорування ЕКГ
РАСПРЕДЕЛЕНИЕ ПРОДОЛЖИТЕЛЬНОСТИ ИНТЕРВАЛА ОТе ПО ДАННЫМ АМБУЛАТОРНОГО МОНИТОРИРОВАНИЯ ЭКГ У ПАЦИЕНТОВ С Г1ПЕРТОНИЧЕСКОЙ БОЛЕЗНЬЮ В ЗАВИСИМОСТИ ОТ КЛИНИЧЕСКИХ ПРОЯВЛЕНИЙ
Целик Н. Е., Шмидт Е. Ю., Мартыненко А. В.
Харьковский национальный университет имени В. Н. Каразина, г. Харьков, Украина
Проведено изучение распределения продолжительности интервала QTc при АМ ЭКГ в зависимости от клинических признаков ГБ у 82 пациентов. За классифицированный укороченный принимали QTc < 320 мс, нормальный > 320 мс и < 440 мс, классифицированный удлиненный > 440 мс. У каждого пациента по данным АМ ЭКГ зарегистрированы средний, максимальный и минимальный QTc. Результаты подтверждают редкую вероятность укороченного Q^ и показывают существование удлиненного Q^ у каждого пациента при АМ ЭКГ. Продолжительность максимального QTc наибольшая у пациентов зрелого возраста, мужского пола, с ожирением III ст., с пониженным и высоким циркадным индексом; II стадией и мягкой степенью ГБ, с впервые
© Tselik N. E.,Shmidt O. Y.,Martynenko O. V., 2017
зарегистрированной и более 10 лет ГБ, умеренным кардиоваскулярным риском сердечно-сосудистых осложнений, диффузным кардиосклерозом, I и II ФК и I и II А стадией ХСН.
КЛЮЧЕВЫЕ СЛОВА: гипертоническая амбулаторное мониторирование ЭКГ
INTRODUCTION
Hypertension (EH) - is one of the most common chronic diseases that significantly increase the risk of cardiovascular complications and sudden death [1-2].
Prolongation or shortening of QT interval is seen as the factor which increases risk of life-threatening arrhythmias [3-6]. Electro-physiological phenomenon of prolonged QT intervals considered to be independent predictor of fatal arrhythmias that leads to sudden cardiac death [7-9].
International guidance on the prevention of sudden cardiac death (SCD) [10] recommends evaluation of QT interval as class 1A indication for the ambulatory ECG monitoring (ECG AM) in risk groups of developing life-threatening arrhythmias.
Ambulatory ECG monitoring is one of the basic methods in identifying this class of arrhythmias [11-12]. We didn't find in the literature any information about the relationship between the distributions of QT duration in ECG AM and clinical signs of EH.
OBJECTIVE
The aim of the work is to study the distribution of QTc duration in ECG AM depending on clinical manifestation of the EH.
The study was conducted as a part of research work «Development and research of automatic control system of heart rate variability», state registration 0109U000622.
MATERIALS AND METHODS
82 patients were examined in the outpatient clinic № 24 in Kharkov (28 male and 54 female, age 33-76 years old, with duration of EH from first identified till 30yers lasting.
Among 82 patients with hypertension the mild hypertension took place in 51, 22 %, moderate - in 29, 27 %, severe - in19, 51 %. The largest proportion of patients with EH II stage was 71, 95 %, I stage - 14, 63 %, III stage - 13, 41 %. The Ischemic heart disease (IHD) was 73,17 % out of the total number of registered patients with EH, among them -52,44 % diffuse cardiosclerosis (DC), 18,29 % - stable angina (SA), 2,44 % - post infarction
болезнь, продолжительность интервала QTc,
cardiosclerosis (PIC). Patients with EH without IHD accounted 26, 83 %. Chronic heart failure (CHF) I stage - 42, 68 %, IIA stage - 30, 49 %. Chronic heart failure with functional class I (CHF FC) was registered in 40,24 %, II class - in 28,05 %, III class -in 4,88 %.
Patients with acute cardiovascular diseases, with stable exertion angina IV FC, HF IIB-III stages and with thyroid diseases were not included in the study.
Identifying of the duration of the medium, maximum and minimum QTc was conducted by results of ECG AM. For these goals we used combined Holter monitoring (ECG + BP). Calculation of QTc duration was carried out with the help of program «Cardio Sense». Corrected QT interval was used (QTc) taking into account the heart rate. Calculation was conducted by Bazzet formula [13-14]. As classified shortened was considered QTc < 320 ms, as normal > 320 ms and < 440 ms, as classified prolonged was considered QTc > 440 ms [6, 12, 15]. These indicators correspond to the resting ECG parameters.
We determined the dependence of average daily indicators of QTc duration in patients with essential hypertension according to gender, age, weight of patients, duration of EH, stage and degree of EH, cardiovascular risk, presence of diabetes, ischemic heart disease, FC HF, stage of HF and the type of circadian index.
Statistical data analysis was performed with applying of parametric criteria (average value -х and standard deviation - s). For determining statistically significant difference in quantitative indicators of QTc in selected groups Student's t-test and multifactor test were used (MANOVA). Calculations were carried out on a personal computer using programs «Microsoft Office Excel 2010» and «STATISTICA 10».
RESULTS AND DISCUSSION
Average, maximum and minimum QTc are registered in every patient during AM ECG. But only by one ECG episode of QTc duration it can't be assigned to the class of normal, prolonged or short QT as in majority of modern researches [6, 9]. That's why it is not
enough and required 24-hours ECG monitoring age, gender, BMI and circadian index are [6-7, 12]. presented in table 1.
QTc interval duration of patients with EH during AM ECG in general and depending on
Table 1
QTc interval duration QTc (x, s) during AM ECG in patients with EH in general and depending on age, gender, BMI and circadian index
Clinical manifestation Graduation of clinical features N P, % Average QTc, ms Maximum QTc, ms Minimum QTc, ms
X s X s X s
82 100 421 18 486 31 382 27
Age, years Adulthood 35 43 416* 18 487* 34 379 * 26
Old age 47 57 398* 18 457* 29 361* 27
Gender Female 54 66 426* 18 490 31 385 27
Male 28 34 411* 19 497 32 377 27
BMI, kg/m2 Normal weight 9 11 420 20 479 40 391 16
Overweight 27 33 418 18 480 33 384 22
Obesity I 27 33 421 20 491 28 379 34
Obesity II 14 17 422 15 491 31 380 28
Obesity III 5 6 431 22 495 25 381 16
Circadian index Normal 40 49 419 20 484 37 384 23
Low 38 46 424 17 487 24 381 32
High 4 5 419 11 488 17 378 11
Note: N — number of surveys; P — specific gravity; x — arithmetic mean; s — standard deviation; QTc — corrected QT; * — p < 0,05 — between QTc values in clinical groups.
In all patients in group the only episode of shortened QTc was registered, the duration of average and minimum QTc are within normal range, while maximum QTc significantly exceeds the normal range. In adulthood patients maximum and minimum QTc were registered, but in aged patients - minimum QTc. Female patients had more prolonged average QTc, but male patients had more prolonged maximum and minimum QTc. In case of obesity of Ill degree average and maximum QTc intervals are more prolonged, while in case of obesity of I
degree the least QTc was minimum. The longest duration of average QTc is in patients with low circadian index (CI), of maximum - in patients with low and high, and minimum duration of average QTc is in patients with high circadian index.
QTc interval duration QTc (x, s) during ECG AM in patients with EH depending on stage and degree of EH, duration of the disease and cardiovascular risk are presented in tab. 2.
Table 2
QTc interval duration QTc (x, s) during AM ECG in patients with EH depending on stage and degree of EH, duration of the disease and cardiovascular risk
Clinical manifestation Graduation of clinical features N P, % Average QTc, ms Maximum QTc, ms Minimum QTc, ms
X s X s X s
Stages of EH I 12 15 409 13 480 34 371* 16
II 59 72 423 18 492 30 383* 29
III 11 13 422 19 464 25 392* 21
Degrees of EH Mild 42 51 417* 17 489 31 381 22
Moderate 24 29 421* 17 484 30 382 33
Severe 16 20 430* 22 484 35 386 29
Duration, years For the first time 7 8 418 6 494 32 374 21
0-5 31 38 418 18 489 31 381 27
6-10 23 28 420 18 474 20 383 26
>10 21 26 426 21 494 39 386 30
Cardiovascular risk Low 11 13 422 19 464 25 392 21
Moderate 50 61 420 19 488 34 378 29
High 13 16 424 18 484 29 386 29
Very high 11 13 422 19 464 25 392 21
Note: N — number of surveys; P — specific gravity; x — arithmetic mean; s — standard deviation; QTc — corrected QT; * — p < 0,05 — between QTc values in clinical groups.
The longest average daily and maximum QTc were recorded in group with EH II stage, minimum was in patients with EH I stage. An increase of average QTc duration was correlated with an increasing degree of hypertension. The longest duration of the maximum and minimum QTc was observed in patients with mild hypertension. Patients with course of the disease more than 10 years had the highest rates of average daily and maximum QTc, patients with EH diagnosed for
the first time had maximum and minimum QTc. The duration of average daily QTc is longer in patients with high cardiovascular risk, while the duration of maximum and minimum QTc are longer in patients with mild cardiovascular risk.
QTc interval duration QTc (x, s) during AM ECG in patients with EH depending on IHD, HF stage and FK of HF, presence of diabetes mellitus are presented in Table 3.
Table 3
QTc interval duration QTc (x, s) during AM ECG in patients with EH depending on IHD, HF stage
and FK of HF, presence of diabetes mellitus
Clinical manifestation Graduation of clinical features N P, % Average QTc, ms Maximum QTc, ms Minimum QTc, ms
X s X s X s
IHD In total 60 73 416 19 478 30 376 28
Stable angina 15 18 417 20 475 37 377 29
Diffuse cardiosclerosis 43 53 424 18 491 26 384 28
Focal cardiosclerosis 2 2 425 12 478 20 396 13
Absence of IHD 22 27 416 17 487 37 382 25
CHF FC I 23 28 425 18 487 24 384 33
II 33 40 420 19 486 34 379 23
III 4 5 429 20 484 12 403 26
Stage I 35 43 425 19 483 31 382 30
II A 25 30 420 18 483 31 382 24
Diabetes mellitus DM 2 type 11 13 426 18 484 17 399 19
Absence of DM 71 87 420 18 487 33 381 27
Note: N — number of surveys; P — specific gravity; x — arithmetic mean; s — standard deviation; QTc — corrected QT; * — p < 0,05 — between QTc values in clinical groups.
In patients with focal cardiosclerosis the largest was average daily QTc, with diffuse cardiosclerosis (DC) - the maximum QTc and with stable angina - the minimum QTc. The longest duration of average daily QTc was observed in patients with HF FC III, and uniformly the same duration of QTc was observed in patients with FC I, I stage of HF and FC II, IIA stage of HF. The duration of the maximum interval QTc was the largest in patients with I and II FC of HF, and uniformly the same - in patients with FC III and I and IIA stages of HF; the duration of the minimum interval QTc was the least in patients with FC II of HF. The duration of average daily and maximal QTc more often was recorded in patients with DM, and minimal QTc interval -in patients without DM [16].
Student's t-test for independent groups showed that for grouping sign «stages of EH», accurately different at level p < 0,05 is minimal QTc, and for grouping sign «degrees of EH» -minimal QTc. Multifactorial test (MANOVA) confirms that researched effects are significant on level p < 0,05.
In all the above data accurate difference at level p < 0,05 between the average and the
maximum QTc; between the average and minimum QTc; between the minimum and the maximum QTc is observed. That's why the corresponding marks are not put anywhere in the tables.
Therefore, obtained results not only confirm a rare probability of short QTc [4-5, 13], but also show presence of prolonged QTc in every patient during ECG AM. Based on the abovementioned it is necessary to use ECG AM in clinical practice to evaluate QTc duration in patients with EH. But such works have not been conducted before. Obviously, specific gravity of prolonged QTc during 24-hours must be the most important, but it requires further study.
CONCLUSIONS
1. Average, maximum and minimum QTc are registered in every patient during ECG AM. At the same time the average and minimum QTc are within normal ranges while maximum QTc far exceeds it.
2. The largest duration of maximal QTc have adulthood male patients with obesity III st., with low and high circadian index, with II stage and mild EH, with for the first time diagnosed EH and with EH lasting more than
10 years, with mild cardiovascular risk, with diffuse cardiosclerosis, with I and II FC and I and IIA stage of HF.
3. The presence of critical level of maximum indicators of the QTc duration in each patient with EH demonstrates the need to use ECG AM in its evaluation taking into account the specific gravity per day.
PROSPECTS FOR FUTURE STUDIES
The prospect of further research is studying of the relationship between specific gravity of maximum QT min ambulatory ECG monitoring and clinical manifestations in patients with essential hypertension.
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